TANKER SAFETY GUIDE CHEMICALS International Chamber of Shipping
FOREWORD TO THE THIRD EDITION The first edition of the ICS Tanker Safety Guide (Chemicals) was published in 1971 and complemented the first IMO Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (Resolution A.212(VII)). It developed from a clear demand for advice on safe operations at sea, and became the standard reference work on chemical tanker operations. This third edition of the Guide is the result of substantial revision and updating. It reflects the continuing need for guidance on well-established chemical tanker practice, but also takes account of more recent developments, which have emerged, in the chemical trades. Cautions about the increasing use of nitrogen supplied at high flow rates from the shore are a case in point. A new feature introduced in this edition is the environmental care aspects of chemical tanker operations. Environmental responsibility is now recognized as one of the most important considerations of any industrial undertaking. The International Convention for the Prevention of Marine Pollution from Ships, universally known as MARPOL, is now so much a part of everyday life for seafarers that it is easy to forget that the chemical tanker regulations MARPOL Annex II - are a relatively recent addition to pollution control legislation. These days the requirements of MARPOL are an integral part of chemical tanker operations, and the Guide explains the link between chemical handling practices and the MARPOL Annex II requirements. The second edition of this Guide consisted of four volumes, three of which contained chemical data sheets. Today, however, chemical shippers are required to provide such data, and electronic technology enables accurate cargo information to be made available promptly to everyone in the transport chain. So whereas the number of chemicals being shipped, often under trade names, has increased to a thousand or more, the need for the ship to maintain an extensive reference library of data sheets is much reduced. It was therefore decided to omit data sheets from this third edition, allowing the operational guidance to be consolidated into a single, comprehensive volume. A model data sheet has however been included, to encourage the presentation of data in a standard format. This is particularly important with regard to emergency and first aid information, which needs to be readily identifiable and in a common layout. When a ship is at sea or at a remote terminal external assistance may not be available, and easily accessible emergency advice is therefore vital. No Guide of this nature can ever be complete, however much care and effort has gone into its preparation. Comments and suggestions for improvements to the Guide are therefore always welcome, and should be addressed to: International Chamber of Shipping 12 Carthusian Street London EC1M 6EZ E-mail: [email protected]
PURPOSE AND SCOPE The purpose of this publication is to provide those serving on ships carrying hazardous and noxious chemicals in bulk with up to date information on recognised good practice in safe operation. The Guide is intended to be a companion to the ICS Tanker Safety Guide (Liquefied Gas). The recommendations cannot cover every possible situation that may be encountered on a chemical tanker, but they do provide wide general guidance on safe procedures and safe working practices when handling and transporting chemicals in bulk. In the interests of consistent and uniform safe working practices, it is recommended that a copy of this Guide be kept - and used - on board all chemical tankers. Chemical tankers should also have on board the International Safety Guide for Oil Tankers and Terminals (ISGOTT), which should be consulted in conjunction with this Guide, especially when oil cargoes are carried, The Guide deals primarily with operational matters and good safety practices. It does not make recommendations on the construction or maintenance of chemical carriers or their equipment: such standards are set by the International Maritime Organization (IMO), national administrations and classification societies. Likewise, the Guide does not address the operation of specific items of equipment or their repair, although in some cases broad references are made to these matters. Nor does the Guide address commercial matters such as tank cleaning standards, cargo quality maintenance or equipment performance, which are set by industrial practices and the requirements of cargo owners.
IMPORTANT NOTE It is emphasised that this Guide is meant to complement, not supersede, any company safety and operational guidelines or ship emergency plans, including safety management procedures required by the IMO International Safety Management (ISM) Code. It should also be borne in mind that in all cases the advice given may be subject to local or national regulations, and that terminal operators have their own safety procedures which could affect cargo handling operations and the measures to be adopted in emergencies. The master and all personnel must be aware of and comply with those regulations and procedures. Their existence will be highlighted by the use of the Ship/Shore Safety Checklist included in Appendix L of this Guide which, together with its guidelines for completion, remains a fundamental part of establishing safe conditions for transport by sea of chemicals in bulk.
FOREWORD TO THE THIRD EDITION
PURPOSE AND SCOPE
GLOSSARY OF ABBREVIATIONS
AN INTRODUCTION TO SEA TRANSPORT OF CHEMICALS IN BULK
PART I OPERATIONAL AND EMERGENCY GUIDELINES 1 3 3 4 4 5 6 6
Chapter 1 HAZARDS AND PROPERTIES OF CHEMICALS 1.1 Introduction 1.2 Flammability 1.3 Health Hazards 1,4 Reactivity 1.5 Corrosiveness 1.6 Putrefaction 1.7 Physical Properties
9 11 11 11 12 12 13 13 14 14 14 15 16 19 19 20 20
Chapter 2 GENERAL PRECAUTIONS 2.1 Introduction 2.2 Cargo Information 2.3 Mooring 2.4 Emergency Towing-off Wires (Fire Wires) 2.5 Access to Ship 2.6 Notices 2.7 Effects of Other Ships and Berths 2.8 Weather Precautions 2.9 Openings in Deckhouses and Superstructures 2.10 Engine and Boiler Room 2.11 Ship/Shore Insulating and Earthing 2.12 Hot Work 2.13 Use of Tools for Ship's Maintenance 2.14 Pumprooms and Enclosed Spaces 2.15 Ship's Readiness to Move 2.16 Navigation
20 20 21 21 21
2.17 Pollution Prevention 2,18 Fire Fighting and Fire Protection Equipment 2.19 Helicopters 2.20 Tank Cleaning and Gas Freeing 2.21 Communication Equipment
Page 23 25 25 26 27 27 28 29 29 31
Subject Chapter 3 ENTRY INTO ENCLOSED SPACES 3.1 General 3-2 Atmosphere in Enclosed Spaces 3.3 Requirements for Entry 3.4 Testing Before Entry 3.5 Entry into Contaminated Cargo Tanks 3.6 Entry After Confirmation of a Safe Atmosphere 3.7 Work in Enclosed Spaces 3.8 Rescue from Cargo Tanks and Other Enclosed Spaces
33 33 35
Chapter 4 CONTROL OF OPERATIONAL DISCHARGES FROM A CHEMICAL TANKER 4.1 Environmental Responsibility 4.2 Existing Controls 4.3 New Controls
37 39 39 40 44 46 46 48 51 53 53 53 55 55 55
Chapter 5 PRECAUTIONS DURING CARGO OPERATIONS 5.1 Introduction 5.2. Responsibility 5-3 Cargo Systems 5.4 Liaison Between Ship and Shore 5.5 General Cycle of Cargo Operations 5.6 Preparation for Cargo Operations 5.7 Preparing a Cargo Tank Atmosphere 5.8 Cargo Loading 5.9 Disconnection of Cargo Hoses 5.10 Cargo Care During the Voyage 5.11 Cargo Unloading 5.12 Ballasting and Deballastmg 5.13 Tank Cleaning and Gas Freeing 5.14 Ship to Ship Transfer
59 61 61 63 63 64 65 66 66 67 69 70 72 74 75 76 77 79
Chapter 6 ENVIRONMENTAL CONTROL OF VAPOUR SPACE IN CARGO TANKS 6-1 Introduction 6.2 Control Methods 6.3 Sources of Inert Gases 6.4 ' Methods of Replacing Tank Atmospheres 6.5 Application to Cargo Tank Operations 6-6 Precautions to Avoid Health Hazards 6.7 Effect of Inert Gas on Inhibited Chemicals 6.8 Control of Tank Atmospheres for Cargo Quality Chapter 7 TANK CLEANING AND GAS FREEING 7.1 Introduction 7.2 Supervision and Preparation 7.3 Cargo Tank Washing and Cleaning 7.4 Special Cleaning Methods 7.5 Arrangements for Disposal of Tank Washings, Slops and Dirty Ballast 7.6 Tank Cleaning Equipment 7.7 Gas Freeing 7.8 Gas Detection Equipment
81 83 83 84 85 86 86 86 86
Chapter 8 EMERGENCY PROCEDURES 8.1 Introduction 8.2 Emergency Organisation 8.3 Emergencies 8.4 Emergency Discharge or Jettison of Cargo 8.5 Notification of Spillage into the Sea 8.6 Personnel Exposure 8.7 Action by Ships When an Emergency Occurs at Other Berths Nearby 8.8 Emergency Removal of a Tanker from a Berth
89 91 91 93 99 94 94
Chapter 9 PERSONAL PROTECTIVE EQUIPMENT 9.1 Introduction 9.2 Respiratory Protection 9.3 Body Protection 9.4 Eye Protection 9.5 Hand Protection 9.6 Foot Protection PART II TECHNICAL INFORMATION
95 97 98 99 100
Appendix A TOXIC PRODUCTS A.1 General A.2 IMO Code Requirements A.3 Medical First Aid A.4 Emergency Schedules (EmS)
101 103 104 105 106
Appendix B CORROSIVE SUBSTANCES B.1 General B.2 IMO Code Requirements B.3 Medical First Aid B.4 Emergency Schedules (EmS)
107 109 109 110 111 112 113
Appendix C REACTIVE CHEMICALS AND RELATED PRECAUTIONS C.1 Introduction C.2 Unstable Chemicals C.3 Chemicals which React with Oxygen C.4 Chemicals which in Contact with Water Emit Dangerous Gases C.5 Incompatible Chemicals C.6 Guidance m the Absence of Adequate Reactivity Data
115 117 117 119
Appendix D STATIC ELECTRICITY D.1 Introduction. D.2 Description of the Process D.3 Control of Static Electricity
123 125 125 126 126 126 127 127 128
Appendix E INERT GAS SYSTEMS E.1 Introduction E.2 Quality E.3 Gaseous Nitrogen Supplied from Shore E.4 Compressed Nitrogen Stored on Board E.5 Liquid Nitrogen Stored on Board E.6 Pressure Swing Adsorption (PSA) Nitrogen Generators E.7 Membrane Separation Nitrogen Generators E.8 Oil Fired Inert Gas Generators
129 131 131 132 132
Appendix F ELECTRICAL EQUIPMENT AND INSTALLATIONS IN HAZARDOUS AREAS F.1 Introduction F.2 Certified Safe Electrical Equipment F.3 General Precautions F.4 Electrical Maintenance and Repairs
133 135 135 136
Appendix G PRESSURE SURGE G.1 Introduction G.2 Generation of Pressure Surge G.3 Other Surge Effects
139 141 141 142 143
Appendix H FIRE FIGHTING - THEORY AND EQUIPMENT H.1Introduction H.2 Theory of Fire Fighting H.3 Fire Fighting Media H.4 Fire Fighting Practice
145 147 148 148 151 152 153 154 155 158
Appendix J INSTRUMENTATION J.1 Introduction J.2 Alarms and Shutdown Circuits J.3 Liquid Level Gauges J.4 Overfill Detection Systems J.5 Pressure Indicating Devices J.6 Temperature Monitoring Equipment J.7 Oxygen Analysers J.8 Cargo Vapour Detection Equipment J.9 Air Supply to Instruments and Controls
159 161 161 161 161 162 162 164
Appendix K CARGO HOSES K.1 Introduction K.2 Certification, Marking and Testing K.3 Cargo Compatibility K.4 Handling, Connection and Use K.5 Ship/Shore Insulation, Earthing and Bonding K.6 Storage and Maintenance K.7 Example Format for Cargo Hose Form
165 167 169 173
Appendix L SHIP/SHORE SAFETY CHECKLIST L.1 Introduction L.2 Ship/Shore Safety Checklist L.3 Guidelines for Completing the Ship/Shore Safety Checklist
Appendix M EXAMPLE OF CARGO INFORMATION FORM (DATA SHEET)
Appendix N EXAMPLE OF AN INHIBITED CARGO CERTIFICATE
Appendix P EXAMPLE OF A HOT WORK PERMIT
Appendix Q EXAMPLE OF AN ENCLOSED SPACE ENTRY PERMIT
BIBLIOGRAPHY The following publications of the International Chamber of Shipping (ICS), the International Association of Ports and Harbor.'' (IAPH), the Oil Companies International Marine Forum (OCIMF), the Tanker Structure Co-0perative Forum (TSCF), the Untied Stales Coast Guard (USCG) and the International Maritime Organization (IMO) should be referred to for additional information and guidance on particular aspects of chemical tanker operation!
Bridge Procedures Guide (ICS) Chemical Data Guide for Bulk Shipment by Water (USCG) Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (BCH Code) (IMO) Disabled Tankers — Report of Studies on Ship Drift and Towage (OCIMF) Guidelines for the Inspection and Maintenance of Double Hull Tanker Structures (TSCF) Guide to Helicopter/Ship Operations (ICS) International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code) (IMO) International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) (IMO) International Safety Guide for Oil Tankers and Terminals (ISGOTT) (TCS/OC1MF/IAPH) Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG) (IMO) Mooring Equipment Guidelines (OCIMF) Peril at Sea and Salvage — A Guide for Masters (ICS/OCIMF) Recommendations on the Safe Transport of Dangerous Cargoes and Related Activities in Port Areas (IMO) Reporting of Incidents Involving Harmful Substances (IMO) Ship to Ship Transfer Guide (Petroleum) (ICS/OCIMF)
DEFINITIONS For the purposes of this Guide the/allowing interpretations apply: Acute Toxic Effect
The effect on humans of a single exposure of short duration to high concentrations of a toxic compound or toxic vapour (see also Chronic Toxic Effect).
Alcohol Resistant Foam (Alcohol-type Foam)
A multi-purpose fire fighting foam effective against many water soluble cargoes. It is also effective against many non-water soluble cargoes. This is the most commonly used type of fire fighting foam on chemical tankers.
A total loss of feeling and consciousness, or the loss of power or feeling over a limited area of skin.
Chemicals which produce anesthesia.
Equipment of a design that has been tested, approved and certified by an appropriate authority, such as an administration or classification society, as safe for use in a specified hazardous atmosphere.
Indicating that the compound is in solution in water.
The condition arising when the blood is deprived of an adequate supply of oxygen/ so that loss of consciousness may follow.
A gas or vapour, which may or may not have toxic properties, which when present in sufficient concentrations excludes oxygen and leads to asphyxia.
Auto-ignition Temperature (Autogenous Ignition Temperature; Ignition Temperature)
The lowest temperature to which a solid, liquid or gas requires to be raised to cause self-sustaining combustion without initiation by a spark or name or other source of ignition (see also Flash Point).
The IMO Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk.
The temperature at which the vapour pressure of a liquid equals that of the atmosphere above its surface; this temperature varies with pressure.
Some liquids which are mixtures, or which contain impurities, boil over a range of temperatures known as the boiling range. When this occurs, the range will be stated on the data sheet. The low temperature is that at which components within the liquid start to boil.
The connecting together of metal parts to ensure electrical continuity.
The term 'in bulk' refers to carriage of cargo in tanks or pressure vessels which are constructed as part of the ship, the contents being loaded and discharged by the ship's installed handling system.
That part of the ship which contains the whole cargo system and cargo Pumprooms, and includes the full beam deck area over the length of the ship above the cargo containment system. Where fitted, the cofferdams, ballast or void spaces at the after end of the aftermost cargo space or at the forward end of the forward cargo space are excluded from the cargo area,
Cargo Handling (Cargo Operations)
The loading, storing, discharging, circulating and transferring of bulk liquid cargo, and associated tank cleaning and gas freeing.
Cargo Information Form
See Data Sheet.
A substance that starts or changes the rate of a reaction without being itself chemically changed. A catalyst, which reduces the rate of a reaction, is known as a negative catalyst.
Certificate of Fitness
A certificate issued by the flag administration confirming that the structure, equipment, fittings, arrangements and materials used in the construction of a chemical tanker are in compliance with the relevant 1MO Chemical Codes. Such certification may be issued on behalf of the administration by approved classification societies.
Certified Gas Free
Certified gas free means that a tank, compartment or container has been tested by an authorized person using an approved testing instrument, and found to be in a suitable condition - i.e. not deficient in oxygen and sufficiently free from toxic or flammable gases - for a specified activity such as hot work, and that a certificate to this effect has been issued.
Chemical Absorption Detector An instrument used for the detection of vapours, which works on the principle (Gas Absorption Detector) of a reaction between a vapour and the chemical agent in the apparatus; either the vapour discolours the agent or the agent dissolves some of the vapour. Chronic Toxic Effect
The cumulative effect on humans of prolonged exposures to low concentrations of a toxic compound or toxic vapour or of intermittent exposures to higher concentrations (see also Acute Toxic Effect).
Closed Gauging System (Closed Ullaging)
A system whereby the contents of a tank can be measured by means of a device which penetrates the tank, but which is part of a closed system and prevents tank contents from being released. It can be mechanical, electronic, magnetic or pressure operated (see also Open Gauging System and Restricted Gauging System).
Capable of being ignited and of burning. For the purposes of this Guide the terms combustible and flammable are synonymous.
Combustible Gas Indicator (Explosimeter)
An instrument for detecting a combustible gas/air mixture, usually measuring its concentration in terms of the Lower Flammable Limit (LFL).
Liquids which can corrode normal constructional materials at an excessive rate. Usually they also cause serious damage to human tissue and eyes.
Data Sheet (Cargo Information Form)
A document, in accordance with the IMO Codes and usually from the manufacturer of the cargo that contains necessary information about the properties of the chemical for its safe carriage as cargo.
Mass per unit volume, measured in a vacuum (see also Litre Weight).
A process which is accompanied by absorption of heat.
A process which is accompanied by evolution of heat.
See Combustible Gas Indicator.
Explosion Proof Equipment/ Equipment or apparatus which will withstand, without damage and in Flame Proof Equipment accordance with its prescribed rating, any explosion of a prescribed flammable gas to which it may be subjected under practical operating conditions, and which will prevent the transmission of flame to the surrounding atmosphere. Explosive Limits See Flammable Limits. Explosive Range
See Flammable Range.
Filling Ratio (for Liquids)
That volume of a tank, expressed as a percentage of the total volume, which can be safely filled by liquid when allowing for the possible expansion of the liquid. A device used to arrest the passage of flame in a pipeline.
Flame Proof Equipment
See Explosion Proof Equipment.
Flame Screen (Gauze Screen)
A portable or fitted device incorporating one or more corrosion resistant wire woven fabrics of very small mesh used for preventing sparks from entering a tank or vent opening. For a short period of time a flame screen will prevent the passage of flame, yet permit the passage of gas.
Capable of being ignited and of burning. For the purposes of this Guide the terms combustible and flammable are synonymous.
Flammable Limits (Explosive Limits)
The minimum and maximum concentrations of vapour in air which form flammable (explosive) mixtures are known as the lower flammable limit (LFL) and upper flammable limit (UFL) respectively. These terms are synonymous with lower explosive limit (LEL) and upper explosive limit (UEL) respectively.
Flammable Range (Explosive Range)
The range of flammable vapour concentrations in air between the lower and upper flammable limits. Mixtures within this range are capable of being ignited and of burning.
The lowest temperature at which a liquid gives off sufficient vapour to be ignited. This temperature is determined by laboratory testing in a prescribed apparatus (see also Auto-ignition Temperature).
A froth creating an air-excluding blanket, and used for fire fighting.
Freezing Point (Melting Point)
The temperature at which the liquid state of a substance is in equilibrium with the solid state, i.e. at a higher temperature the solid will melt and at a lower temperature the liquid will solidify. Freezing point and melting point may not always coincide, but they are sufficiently close to enable the difference between them to be ignored for the purposes of this Guide. This term is used to cover all vapour mixtures or vapour-and-air mixtures.
Gas Absorption Detector
See Chemical Absorption Detector.
Gas free means that a tank, compartment or container has been tested using appropriate gas detection equipment and found to be not deficient in oxygen and sufficiently free, at the time of the test, from toxic, flammable or inert gases for a specified purpose.
See Closed Gauging System, Open Gauging System and Restricted Gauging System.
See Flame Screen.
An area in which vapour may be present continuously or intermittently in sufficient concentrations to create a flammable atmosphere or an atmosphere which is dangerous for personnel.
A general descriptive term for a danger to the health of personnel.
Work involving flames, incendive sparks or temperatures likely to be sufficiently high to cause ignition of flammable gas. The term includes any work involving the use of welding, burning or soldering equipment, blow torches, some power driven tools, portable electrical equipment which is not intrinsically safe or contained in an explosion proof housing, and equipment with internal combustion engines. A document issued by an authorised person permitting specified work to be done for a specified time in a defined area, employing tools and equipment which could cause ignition of flammable gas (see Hot Work).
Hot Work Permit
The IMO International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk.
See Auto-ignition Temperature.
The International Maritime Organization; a specialised agency of the United Nations.
See BCH Code and IBC Code. The Codes are described in Chapter 4.
A spark of sufficient temperature and energy to ignite a flammable atmosphere.
A gas or vapour containing insufficient oxygen to support combustion.
The introduction of inert gas into a space to reduce and maintain the oxygen content to a level at which combustion cannot be supported, or to maintain the quality of the cargo. The act of introducing a substance into the body via the digestive system.
Ingestion Inhibited Cargo
A chemical cargo to which an inhibitor has been added.
A substance used to prevent or retard cargo deterioration or a potentially hazardous chemical self-reaction, e.g. polymerisation.
An insulating device placed between metallic flanges, bolts and washers, to prevent electrical continuity between pipelines, sections of pipelines, hose strings and loading arms, or equipment or apparatus. -
Intrinsically safe equipment, instruments or wiring are incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specified hazardous atmospheric mixture in its most easily ignited concentration.
A liquid which on direct contact with the eyes or skin will cause severe irritation, injury or burns.
A vapour, which will cause irritation of the eyes, nose, throat and respiratory tract.
The International Safety Guide for Oil Tankers and Terminals.
LFL or LEL
See Flammable Limits.
Mass per unit volume, measured in air (see also Density).
Loading Overall (Over the Top)
Loading through hatches or other deck openings by means of portable open ended pipes or hoses.
Valves in a tanker's piping system immediately adjacent to the ship/shore connecting flanges.
The International Convention for the Prevention of Pollution from Ships 1973, as modified by its Protocol of 1978.
See Freezing Point.
The IMO Medical First Aid Guide for Use in Accidents Involving Dangerous Goods.
The ability of a liquid or gas to dissolve uniformly in another liquid or gas. Gases mix in all proportions but the miscibility of liquids depends upon their chemical properties. Similar chemicals mix in all proportions (e.g. alcohol and water) but others are only partly miscible (e.g. benzene and water). Many gases are miscible with liquids.
MSDS or Material Safety Data Sheet
See Data Sheet.
Those surfaces of the human respiratory system lined with secretion; for example, the inside of the nose, throat, windpipe and lungs. Can also be applied to the eyes.
Open flames or fires, exposed incandescent material or any other unconfined source of ignition.
A condition of profound insensibility, resembling sleep, in which the unconscious person can only be roused with great difficulty but is not entirely indifferent to sensory stimuli.
The smallest concentration of gas or vapour, expressed in parts per million (ppm) by volume in air, that most people can detect by smell.
Open Gauging System
A system of measuring the contents of a tank, which makes use of an opening in the tank and may expose the gauger to the cargo or its vapour (see also Closed Gauging System and Restricted Gauging System).
Over the Top
See Loading Overall.
An element or compound that is capable of adding oxygen or removing hydrogen or one that is capable of taking one or more electrons from an atom or group of atoms (the opposite of a Reducing Agent).
An instrument used to measure oxygen concentrations, expressed as a percentage by volume.
Filling and maintaining the cargo tank and associated piping system with an inert gas, other gas or vapour, or liquid, in order to separate the cargo from air.
Compounds formed by the chemical combination of cargo liquid or vapour with atmospheric oxygen, or oxygen from another source. These compounds may in some cases be highly reactive or unstable and constitute a potential hazard.
A scale which indicates the acidity or alkalinity of a solution. Its range is 0 to 14. pH 7 represents absolute neutrality. A value of 0 represents high acidity (e.g. concentrated acids) and 14 represents high alkalinity (e.g. a caustic soda solution). '
A very toxic substance which when absorbed into the human body by ingestion, skin absorption, or inhalation produces a serious or fatal effect.
The phenomenon whereby the molecules of a particular compound link together into a larger unit containing anything from two to many thousands of molecules, the new unit being called a polymer. A compound may thereby change from a free flowing liquid into a viscous one or even a solid. A great deal of heat may be evolved when this occurs. Polymerisation may occur spontaneously with no outside influence, or it may occur if the compound is heated, or if a catalyst or impurity is added. Polymerisation may, under some circumstances, be dangerous but may be delayed or controlled by the addition of inhibitors.
The lowest temperature at which a liquid will remain fluid.
Force per unit area. Usually expressed as gauge pressure relative to atmosphere (as shown on a gauge that registers zero at atmospheric pressure) or absolute pressure.
Pressure/Vacuum Valve (P/V Valve)
A dual purpose valve commonly incorporated in the cargo tank venting system of tankers, the operation of which, when appropriately set, automatically prevents excessive pressure or vacuum in the tank or tanks concerned.
The natural decomposition, over time, of animal or vegetable oils, accompanied by offensive smells. Sometimes called 'going off.
An element or compound that is capable of removing oxygen, or adding hydrogen or one that is capable of giving one or more electrons to an atom or group of atoms (the opposite of an Oxidising Agent).
Reid Vapour Pressure (RVP) The vapour pressure of a liquid determined by laboratory testing in a standard manner in the Reid Apparatus at a standard temperature of 100T (37.8°C) expressed in pounds per square inch absolute, and commonly written 'RVP..... Ib.'. Relative Vapour Density
The relative weight of the vapour compared with the weight of an equal volume of air at standard conditions of temperature and pressure. Thus vapour density of 2.9 means that the vapour is 2.9 times heavier than an
equal volume of air, under the same physical conditions. Respiratory Tract
The human air passages from nose to lungs inclusive.
The master or any officer to whom the master has delegated responsibility for an operation or duty. See Terminal Representative.
Responsible Terminal Representative Restricted Gauging System
A system employing a device which penetrates the tank and which, when in use, permits a small quantity of cargo vapour or liquid to be exposed to the atmosphere: when not in use, the device is completely closed (see also Closed Gauging System and Open Gauging System).
Safety Relief Valve
A valve fitted on a pressure vessel to relieve overpressure.
The tendency of a chemical to react with itself, usually resulting in polymerisation or decomposition. Self-reaction may be promoted by contamination with small amounts of other materials.
Short Term Exposure Limit See Threshold Limit Value. (STEL) SOLAS
The International Convention for the Safety of Life at Sea 1974, as modified by its Protocol of 1988.
The ability of one substance (solid, liquid or gas) to blend uniformly with another. Solubility is usually understood as the maximum weight of substance which will dissolve in water in the presence of undissolved substance. The value is usually expressed as the number of grams of substance dissolving in 100 grams of water. In the case of liquid dissolving in another liquid, the term miscibility is often used instead of solubility.
The ratio of the weight of a volume of a substance at a given temperature to the weight of an equal volume of fresh water at the same temperature or at a different given temperature. Since temperature affects volume, the temperature at which a specific gravity comparison is made needs to be known, and is stated after the ratio. Ignition of a combustible material is termed 'spontaneous' if the inherent characteristics of the material cause a heat producing (exothermic) chemical action and thus ignition without exposure to external fire, spark or abnormal heat.
The electrical charge produced on dissimilar materials through physical contact and separation, such as is caused by a fluid passing through a pipeline or into a tank.
Stern Discharge Line
A cargo pipeline over the deck to a point terminating at or near the stern of the tanker.
The final operation in pumping bulk liquid from a tank or pipeline.
Sweeping (Squeegeeing or Puddling)
The manual pushing of semi-liquid residues of animal fat or vegetable oil cargoes towards the pump suction during the final stages of discharge, using sweeping sticks or squeegees.
Systemic Toxic Effect
The effect of a substance or its vapour on those parts of the human body with which it is not in contact. This presupposes that absorption has taken place. It is possible for chemicals to be absorbed through skin, lungs or stomach, producing later manifestations which are not a result of the original direct contact.
Tank Vent System (Vent Line)
The piping system and associated valves, installed to prevent overpressure or underpressure (vacuum) in cargo tanks.
A person designated by the terminal to take responsibility for an operation or duty.
Threshold Limit Value (TLV) The time weighted average (TWA) concentration of a substance to which it is (Short Term Exposure Limit) believed workers may be repeatedly exposed, for a normal 8 hour working day and 40 hour working week, day after day, without adverse effect. It may be supplemented by other limits. Topping Off
The operation of completing the loading of a tank to a required ullage.
Poisonous, i.e. causing bodily harm that may be severe (see also Acute Toxic Effect and Chronic Toxic Effect).
Toxic Liquid Toxic Vapour
A liquid which if ingested or absorbed through the skin causes bodily harm that may be severe. A vapour which if inhaled causes bodily harm that may be severe.
UFL or UEL
See Flammable Limits.
The depth of free space left in a cargo tank above the liquid level. One or more of the components of chemical products when in the vapour phase.
The pressure exerted by the vapour above the liquid, at a given temperature. It is expressed as absolute pressure.
The release of cargo vapour or inert gas from cargo tanks and associated systems.
See Tank Vent System.
The property of a liquid which determines its resistance to flow.
A liquid which evaporates readily at ambient temperatures.
The tendency for a liquid to vaporise.
Very fine droplets of water generally delivered at a high pressure through a fog nozzle.
Water divided into coarse drops by delivery through a special nozzle.
Water Spray System
A system of sufficient capacity to provide a blanket of water droplets to cover the cargo manifolds, deck storage tanks, and boundaries of superstructures and deckhouses.
GLOSSARY OF ABBREVIATIONS ACGIH
American Council of Governmental Industrial Hygienists
Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk
CHRIS Code Chemical Hazards Response Information System, published by the US Coast Guard EmS
Emergency Schedules (to MFAG)
Emergency Shutdown valve
High Level Alarm
International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk International Chamber of Shipping
International Electrotechnical Commission
International Labour Organization
Code International Maritime Dangerous Goods Code
International Medical Guide for Ships
International Maritime Organization
International Safety Guide for Oil Tankers and Terminals
ISM Code LEL
International Management Code for the Safe Operation of Ships and for Pollution Prevention (The International Safety Management (ISM) Code) Lower Explosive Limit
Lower Flammable Limit
Maximum Allowable Concentration of a vapour
International Convention for the Prevention of Marine Pollution from Ships
Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (Supplement to IMDG Code) Material Safety Data Sheet
Oil Companies International Marine Forum
P&A Manual Procedures and Arrangements Manual PPE
Personal Protective Equipment
Parts per million
Pressure Swing Adsorption
Polytetrafluoroethylene tape, for sealing joints
Reid Vapour Pressure
Shipboard Marine Pollution Emergency Plan
Shipboard Oil Pollution Emergency Plan
Self-contained compressed air breathing apparatus
International Convention for the Safety of Life at Sea
Short Term Exposure Limit
Ship to Ship
Threshold Limit Values
TLV - TWA Threshold Limit Values - Time Weighted Average TLV - STEL Threshold Limit Values - Short Term Exposure Limit TLV - C
Threshold Limit Values - Ceiling
Time Weighted Average
Upper Explosive Limit
Upper Flammable Limit
United States Coast Guard
Voyage Response Plan (US requirement)
Vapour Recovery Unit
World Health Organization
AN INTRODUCTION TO SEA TRANSPORT OF CHEMICALS IN BULK BRIEF HISTORY OF THE TRADE Organic and inorganic chemicals were first synthesised on an industrial scale using coal, limestone, cellulose or molasses as raw materials in the early 1900s. The first petrochemical plants were developed in the United States in the 1920s, in tandem with the early oil refineries. Bulk shipment of liquid chemicals began in the mid-1940s using standard oil product tankers. At about the same time, some traditional cargo ships were equipped with deep tanks suitable for carrying vegetable oils as part of their liner cargo service. The first tanker to be specially designed to carry chemicals in bulk was the Marine Dow-Chem, a twin-screw steam turbine ship built in 1954 in the USA.
Since that time, the range of chemicals shipped in bulk has increased enormously and a special class of ships has been developed to meet this need - the chemical tanker. Most early chemical tankers were slightly modified product tankers, in which the main variation was coating of the cargo tanks. Although many of the products shipped could be carried quite safely in uncoated mild steel tanks, the need to maintain product quality, to minimise the potential for discoloration, and to facilitate tank cleaning between cargoes led to tank surfaces being coated with an impervious material. As the shipment of bulk chemicals developed, different countries involved with the trade developed regulations to minimise the risk to the ship, its crew and the environment, and applied them to their own ships and ships trading to their ports. These regulations were not all the same, and it was extremely difficult for a ship and its crew to comply with them all. To establish an international standard for the safe design, construction and equipment of chemical tankers, IMO developed the Bulk Chemical Codes. It was a major step forward. A ship that complies with the IMO Codes is issued with a Certificate of Fitness that is recognised internationally, and enables the ship to trade worldwide carrying the cargoes for which it is approved. The cargoes now carried in these ships range from petrochemicals used as feedstock for plastics or synthetic rubbers and fibres, industrial acids and alkalis, alcohol and solvents, highly refined lubricating oils and lubricating oil additives, to detergents, animal and vegetable oils, and edible products such as fruit juices or wine. Furthermore, certain refined petroleum products that were previously considered to be oils are now classified as chemicals under IMO marine pollution or toxicity regulations, and must only be carried by chemical tankers.
CHEMICAL TANKER CARGOES Chemical tanker cargoes may be divided into four main groups: Petrochemicals. This is the collective name for organic chemicals derived from crude oil, natural gas and coal. Organic chemicals are those produced from living or once-living organisms, petroleum and natural gas (marine animals and plants) and coal (plants). It is now possible to synthesise organic chemicals from inorganic chemicals to the extent that 'organic chemicals' really means those compounds based upon the element carbon. But the term does not include the simplest carbon compounds such as carbon dioxide, carbon monoxide and the carbonates. Alcohols and carbohydrates. Alcohols may be derived from hydrocarbons or produced by fermentation. Vegetable and animal oils and fats. Derived from the seeds of plants and from the fat of animals and fish. Acids and inorganic chemicals. Inorganic chemicals are those that are not produced from living or once-living organisms. However, a number of inorganic chemicals such as sulphur and ammonia can be manufactured using petroleum as the raw material. Acids may be organic or inorganic. TYPES OF CHEMICAL TANKERS A modem chemical tanker is primarily designed to carry some of the several hundred hazardous products now covered by the IMO Bulk Chemical Codes. The following general types of chemical carriers have developed since the trade began:
Sophisticated parcel chemical tankers: typically up to 40,000 tonnes deadweight with multiple small cargo tanks - up to 54 - each with an individual pump and a dedicated pipeline, to carry small parcels of high grade chemicals. These ships have a significant proportion of the cargo tanks made with stainless steel, allowing maximum flexibility to carry cargoes that need their quality safeguarded. Product/chemical tankers: of similar size to parcel tankers but with fewer cargo tanks, mostly of coated steel rather than stainless, and less sophisticated pump and line arrangements. Such ships carry the less difficult chemicals, and also trade extensively with clean oil products. Specialised chemical carriers: small to medium sized ships, often on dedicated trades and usually carrying a single cargo such as an acid, molten sulphur, molten phosphorus, methanol, fruit juice/ palm oil or wine. Cargo tanks are coated or stainless steel according to the trade.
HAZARDS AND PROPERTIES OF CHEMICALS 1.1 Introduction 1.2 Flammability 1.3 Health Hazards .1 Toxicity .2 Asphyxia .3 Anesthesia .4 Additional health hazards 1.4 Reactivity .1 Self-reaction .2 Reaction with water .3 Reaction with air .4 Reaction with other cargoes .5 Reaction with other materials 1.5 Corrosiveness 1.6 Putrefaction 1.7 Physical Properties .1 Specific gravity .2 Vapour pressure and boiling point .3 Freezing point .4 Cubic expansion .5 Vapour density .6 Solubility .7 Electrostatic charging .8 Viscosity
HAZARDS AND PROPERTIES OF CHEMICALS This chapter gives an introduction to the range of hazards normally associated with the properties of chemicals that are carried as cargoes, and the precautions necessary to minimise or avoid those hazards. 1.1 INTRODUCTION Chemical tankers are required to transport a wide range of different cargoes, and many tankers are designed to carry a large number of segregated products simultaneously. The operation of chemical tankers differs from any other bulk liquid transportation operations, in that on a single voyage a large number of cargoes with different properties, characteristics and inherent hazards may be carried. Moreover, in port several products may be handled simultaneously at one berth, typically including different operations such as discharge and loading as well as tank cleaning. Even the less sophisticated chemical tankers are more complex to operate than oil tankers. Transportation of bulk chemicals by sea not only requires specialist ships and equipment, but also specialist crew training, both theoretical and practical, in order for those involved to understand the characteristics of the various chemicals and be aware of the potential hazards involved in handling them. A particularly important aspect of this requirement is the provision of a data sheet, or cargo information form, giving details specific to a substance, to be held on board whenever that substance is carried by the ship (see Section 2.2). The following notes are only intended to indicate the most common characteristics and hazards of chemicals transported by sea in bulk. More detailed information on the main hazards and properties will be found in relevant chapters and appendices, where guidance is also given on the precautions to be taken. 1.2 FLAMMABILITY Vapour given off by a flammable liquid will burn when ignited provided it is mixed with certain proportions of air, or more accurately with the oxygen in air. But if there is too little or too much vapour compared to the air, so that the vapour-and-air mixture is either too lean or too rich, it will not burn. The limiting proportions, expressed as a percentage by volume of flammable vapour in air, are known as the lower flammable limit (LFL) and the upper flammable limit (UFL), and the zone in between is the flammable range (see Definitions for further details). Combustion of a vapour-and-air mixture results in a very considerable expansion of gases which, if constricted in an enclosed space, can raise pressure rapidly to the point of explosive rupture. In addition, a flammable liquid must itself be at or above a temperature high enough for it to give off sufficient vapour for ignition to occur. This temperature is known as the flash point. Some cargoes evolve flammable vapour at ambient temperatures, others only at higher temperatures or when heated. Safe handling procedures depend upon the flammability characteristics of each product. Non-combustible cargoes are those which do not evolve flammable vapours. As mentioned, the fire risk presented by a flammable cargo depends upon the oxygen content of the atmosphere above it. By filling the ullage space in a cargo tank with an inert gas such as nitrogen or the output of an oil fired inert gas generator/ the oxygen content can be reduced to a level at which the atmosphere will no longer support combustion of flammable vapour. This is known as inerting a tank. But it is important to remember that an inerted atmosphere may
become flammable again if air is admitted, for instance during routine measuring or on venting the mixture to atmosphere or during gas freeing with air (see Chapter 6 for guidance on cargo tank atmospheres). An inert atmosphere must not be considered as being without hazard, however, as without enough oxygen it will not support life either. Any person entering a tank which has been inerted must always follow strict procedures for entry into enclosed spaces (see Chapter 3). 1.3 HEALTH HAZARDS 1.3.1 Toxicity Toxic means the same as poisonous. Toxicity is the ability of a substance, when inhaled, ingested, or absorbed by the skin, to cause damage to living tissue, impairment of the central nervous system, severe illness or, in extreme cases, death. The amounts of exposure required to produce these results vary widely with the nature of the substance and the duration of exposure to it. Acute poisoning occurs when a large dose is received by exposure to high concentrations of a short duration, i.e. a single brief exposure. Chronic poisoning occurs through exposure to low concentrations over a long period of time, i.e. repeated or prolonged exposures. Toxicity is objectively evaluated on the basis of test dosages under controlled conditions, and expressed as threshold limit values (TLVs). A full explanation is given in Appendix A. Prevention of exposure is achieved through a combination of cargo containment, which prevents toxic fumes or liquid from contaminating the workplace, and the use of personal protective equipment (PPE). The latter is described in Chapter 9. 1.3.2 Asphyxia Asphyxia is unconsciousness caused by lack of oxygen, and means suffocation. Any vapour may cause asphyxiation, whether toxic or not, simply by excluding oxygen in air. Danger areas include cargo tanks, void spaces and cargo pumprooms. But the atmosphere of a compartment may also be oxygen-deficient through natural causes, such as decomposition or putrefaction of organic cargo (see Appendix C), or rusting of steel in void spaces such as cofferdams, forepeak and afterpeak tanks. Precautions to be observed before entering these spaces are described in Chapter 3. 1.3.3 Anesthesia Certain vapours cause loss of consciousness due to their effect on the nervous system. In addition, anaesthetic vapours may or may not be toxic. 1.3.4 Additional health hazards Additional health hazards may be presented by non-cargo materials used on board during cargo handling. One hazard is that of frostbite from liquid nitrogen stored on board for use as atmosphere control in cargo tanks. Full advice on dealing with frostbite is contained in the MFAG (see Definitions). Another hazard is that of burns from accidental contact with equipment used while handling heated cargoes. 1.4 REACTIVITY A chemical may react in a number of ways; with itself, with water, with air, with other chemicals or with other materials.
1.4.1 Self-reaction The most common form of self-reaction is polymerisation. Polymerisation generally results in the conversion of gases or liquids into viscous liquids or solids. It may be a slow, natural process which only degrades the product without posing any safety hazards to the ship or the crew, or it may be a rapid, exothermic reaction evolving large amounts of heat and gases. Heat produced by the process can accelerate it. Such a reaction is called a run-off polymerisation that poses a serious danger to both the ship and its personnel. Products that are susceptible to polymerisation are normally transported with added inhibitors to prevent the onset of the reaction. See Appendix C for details. An inhibited cargo certificate should be provided to the ship before a cargo is carried. An example is shown in Appendix N. The action to be taken in case of a polymerisation situation occurring while the cargo is on board should be covered by the ship's emergency contingency plan. 1.4.2 Reaction with water Certain cargoes react with water in a way that could pose a danger to both the ship and its personnel. Toxic gases may be evolved. The most noticeable examples are the isocyanates; such cargoes are carried under dry and inert condition. Other cargoes react with water in a slow way that poses no safety hazard, but the reaction may produce small amounts of chemicals that can damage equipment or tank materials, or can cause oxygen depletion. 1.4.3 Reaction with air Certain chemical cargoes, mostly ethers and aldehydes, may react with oxygen in air or in the chemical to form unstable oxygen compounds (peroxides) which, if allowed to build up, could cause an explosion. Such cargoes can be either inhibited by an anti-oxidant or carried under inert conditions. 1.4.4 Reaction with other cargoes Some cargoes react dangerously with one another. Such cargoes should be stowed away from each other (not in adjacent tanks) and prevented from mixing by using separate loading, discharging and venting systems. When planning the cargo stowage, the master must use a recognised compatibility guide to ensure that cargoes stowed adjacent to each other are compatible. 1.4.5 Reaction with other materials The materials used in construction of the cargo systems must .be compatible with the cargo to be carried, and care must be taken to ensure that no incompatible materials are used or introduced during maintenance (e.g. by the material used for replacing gaskets). Some materials may trigger a self-reaction within the product. In other cases, reaction with certain alloys will be non-hazardous to ship or crew, but can impair the commercial quality of the cargo or render it unusable. ^ 1.5 CORROSIVENESS Acids, anhydrides and alkalis are among the most commonly carried corrosive substances. They can rapidly destroy human tissue and cause irreparable damage. They can also corrode normal ship construction materials, and create a safety hazard for a ship. Acids in particular react with most metals, evolving hydrogen gas which is highly flammable. The IMO Codes address this, and care should be taken to ensure that unsuitable materials are not included in the cargo system. See Appendix B. Personnel likely to be exposed to these products should wear suitable personal protective equipment (see Chapter 9).
1.6 PUTREFACTION Most animal and vegetable oils undergo decomposition over time, a natural process known as putrefaction (going off), that generates obnoxious and toxic vapours and depletes the oxygen in the tank. Tanks that have contained such products must be carefully ventilated and the atmosphere tested prior to tank entry (see Chapter 3). It must not be assumed that all vapours produced by cargoes liable to putrefaction will in fact be due to putrefaction; some may not be obvious, either through smell or appearance of the cargo. Carbon monoxide (CO), for instance, is colourless and odourless and can be produced when a vegetable or animal oil is overheated. 1.7 PHYSICAL PROPERTIES 1.7.1 Specific gravity Cargo tanks on a chemical tanker are normally designed to carry cargoes of a higher specific gravity than an oil tanker. Sometimes the design strength even differs between tanks on the same ship. The information regarding tank strength may be found on the classification society's certification of the ship, and the master must be familiar with any restrictions that may be imposed on loading heavy cargoes. Especially important is the risk of slack loading a tank because this can lead to sloshing forces that may cause damage to the tank structure or its equipment. Likewise, the tank's design capacity must be strictly observed: exceeding it is dangerous. Note that the cargo's specific gravity and its vapour pressure must be considered together. 1.7.2 Vapour pressure and boiling point At any given temperature every liquid exerts a pressure called the vapour pressure. The liquid will boil when its vapour pressure equals the external atmospheric pressure. In a closed cargo tank a liquid will boil when the vapour pressure is equal to the external vapour pressure plus the pressure setting of the pressure/vacuum (P/V) valve. The tanks and vent systems are designed to withstand this pressure, plus the hydrostatic pressure of the cargo. Cargoes that exceed the normal atmospheric pressure at 37.8°C (100°F) should not be loaded into a tank that is not specially designed for that duty. Where a P/V valve set point can be varied, the correct setting should be confirmed. Vent line systems must be checked for correct operation at regular intervals, as structural damage can easily result from malfunction or blockage due to freezing of cargo vapour, polymer build-up, atmospheric dust or icing in adverse weather conditions. Flame screens are also susceptible to blockage, which can cause similar problems. The higher the vapour pressure the more vapours will be released, a fact that may require use of personal protective equipment. 1.7.3 Freezing point. Most liquids have a defined freezing or solidification point, sometimes described as the melting point. Some products, such as lubricating oil additives, vegetable and animal oils, polyols etc. do not have a defined point, but a freezing or melting range. For such cargoes, viscosity is used as a measurement of the product's liquidity or handling characteristics, and the term pour point is used instead. Cargoes with a freezing point higher than the ambient temperature of the ship's trading area will need to be heated in order to remain liquid. The structure and equipment of a ship normally impose a limitation on the carriage of heated cargoes. Exceeding this limitation could damage the tank coating or its structure. Excessive heat will also create thermal stresses, and the risk of cracking will increase. (Note that moderate heat increases steel strength; it is expansion forces that are the immediate limiting factor.) Caution should be exercised when carrying high heat products because cargo in non-insulated pipes and vents may freeze and clog the systems. Heating arrangements must
be operated in accordance with design safety precautions; for example, pressures inside heating coils in tanks must be kept higher than the cargo pressure, and any interceptor tanks between heating return lines and the engine room must be checked regularly to detect any contamination. For certain cargoes, heating coils must be blanked off in accordance with IBC Code requirements. Uninsulated cargo pipes used for high heat products pose a further safety hazard, as they may cause severe burns if touched. 1.7.4 Cubic expansion Liquids will expand as temperature rises, or contract when temperature falls. Sufficient space must be allowed in the tank to accommodate any cubic expansion expected during the voyage. A useful formula is: Filling ratio (% full) = 100 (1 - RT) - S where R = coefficient of expansion per °C (from cargo data sheet) T = expected maximum temperature rise in °C (during voyage) S = safety margin, usually 2% of tank capacity. Vent line systems must be checked at regular intervals. Their design capacity is based on vapour flow only; structural damage may result if vent systems become full of cargo liquid due to thermal expansion. 1.7.5 Vapour density Vapour density is expressed relative to the density of air, as heavier or lighter. Most chemical cargo vapours are heavier than air. Caution must therefore be exercised during cargo operations, as vapour concentrations are likely to occur at deck level or in lower parts of cargo pumprooms. 1.7.6 Solubility Solubility is expressed in different ways: either as a simple yes or no, as slight, or as a percentage, but always in relation to water. Solubility is temperature dependant. A cargo with low solubility will form a layer above or below a water layer depending on its specific gravity. Most non-soluble chemicals are lighter than water and will float on top but some others, such as chlorinated solvents, are heavier and will sink to the bottom. Chemicals that are heavier than water can cause a safety risk in pumprooms when the overlying water is disturbed, and in drip trays. Even in cargo tanks they may be trapped under water in pump wells, and pose a danger even after the tank atmosphere is tested and found safe for entry. 1.7.7 Electrostatic charging Certain cargoes are known as static accumulators, and become electrostatically charged when handled. They can accumulate enough charge to release a spark that could ignite a flammable tank atmosphere. The precautions necessary to prevent ignition from electrostatic charging are contained m Chapter 5, and a description of the phenomenon itself is given in Appendix D. 1.7.8 Viscosity The viscosity of a cargo determines how easy it is to pump, and the amount of residue that will be left after unloading. Viscosity is related to temperature and, in general, a substance will become less viscous at higher temperatures, but note that certain cargoes (such as luboil additives) show increased viscosity when heated. IMO standards define high and low viscosity substances, and require cargo tanks that have contained substances with a high viscosity to be pre-washed and the washings discharged to shore reception facilities.
CHAPTER 2 GENERAL PRECAUTIONS 2.1 Introduction 2.2 Cargo Information 2.3 Moorings 2.4 Emergency Towing-off Wires (Fire Wires) 2.5 Access to Ship .1 Means of access (gangways or accommodation ladders) .2 Lighting .3 Unauthorised persons .4 Persons smoking or intoxicated 2.6 Notices .1 Permanent .2 Temporary 2.7 Effects of Other Ships and Berths .1 Tugs and other craft alongside .2 Other tankers at adjacent berths .3 Chemical tanker operations at general cargo berths 2.8 Weather Precautions .1 Wind conditions .2 Electrical storms .3 Cold weather 2.9 Openings in Deckhouses and Superstructures 2.10 Engine and Boiler Room .1 Combustion equipment .2 Blowing boiler tubes .3 Cargo vapour 2.11 Ship/Shore Insulating and Earthing .1 Insulating .2 Ship/shore bonding cables 2.12 Hot Work .1 General .2 Assessment of hot work .3 Preparations for hot work .4 Checks by officer responsible for safety during hot work .5 Action on completion of hot work 2.13 Use of Tools for Ship's Maintenance .1 Power tools .2 Hand tools 2.14 Pumprooms and Enclosed Spaces .1 Cargo pumprooms .2 Enclosed spaces 2.15 Ship's Readiness to Move 2.16 Navigation 2.17 Pollution Prevention 2.18 Fire Fighting and Fire Protection Equipment 2.19 Helicopters 2.20 Tank Cleaning and Gas Freeing .1 Awareness of additional hazards .2 Use of tank cleaning agents 2.21 Communication Equipment .1 Ship's radio transmission equipment .2 Personal items
This chapter deals with general precautions which should be observed on a chemical tanker, irrespective of the cargoes being carried. A chemical tanker has many potential dangers, and the need for constant vigilance is recognised in the extensive training of crew members and the safety procedures that have been established. Additional precautions for specific cargoes are dealt with in other chapters. 2.1 INTRODUCTION Care and attention should be given to safety precautions at all times/ both in port and at sea. The concept of safety first should be incorporated into the ship's operational and cargo handling manuals. Prior knowledge of a possible problem usually allows it to be avoided through precautionary planning or by the development of safe working practices. Ports and terminals may specify the need for additional and different precautions. It is the master's responsibility to see that local regulations are understood and observed. 2.2 CARGO INFORMATION The IMO Codes require that certain information must be available on board the ship for each particular cargo, and prior to loading. The information should include: • A full description of the physical and chemical properties, including reactivity, necessary for the safe containment of the cargo. • Compatibility with other materials. • Action to be taken in the event of spills or leaks. • Countermeasures against accidental personal contact. • Fire fighting procedures and fire extinguishing media. • Procedures for cargo transfer, tank cleaning, gas freeing and ballasting. • Whether the chemical is stabilised. The correct technical name of the cargo should be available, and only cargoes for which the ship is approved should be loaded. For those cargoes required to be stabilised or inhibited, the cargo should be refused if an inhibited cargo certificate (see Appendix N) is not supplied. It is the shipper's responsibility to provide the necessary information, which may be given in the form of a cargo information form or data sheet for each cargo. Loading should not commence before the master is satisfied that the necessary information for safe handling of the cargo is available to the personnel involved. 2.3 MOORINGS Chemical terminals are often located in tidal areas or rivers, with other ships passing at close distance, thus making proper mooring a significant safety issue. The consequences of a chemical tanker ranging along a jetty or breaking away from a berth could be disastrous,
especially during a cargo transfer involving multiple different chemicals. Correct and sufficient mooring is therefore of the utmost importance. Mooring requirements and arrangements are usually determined by the location and the layout of the terminal, supplemented by advice from the pilot. Moorings should be regularly checked and tended to ensure that they remain effective. The master should ensure that, during cargo operations, sufficient personnel are available for mooring adjustments.
2.4 EMERGENCY TOWING-OFF WIRES (FIRE WIRES) The ship should provide towing-off wires, ready for immediate use without adjustment, in case the ship needs to be moved in the event of fire or other emergency. In most ports, emergency towing-off wires are mandatory when at a berth. Wires should be positioned fore and aft on the offshore side of the ship. They should be in good condition, of adequate strength, and properly secured to the bitts such that full towing loads can be applied. The eyes should be maintained at or about the waterline in a position that tugs can easily reach. Sufficient slack to allow the tugs to tow effectively should be retained between the bitts and the fairlead, but prevented from running out by a rope yam or other easily broken means. There are various methods currently in use for rigging emergency towing-off wires, and the arrangement may vary from port to port. A terminal which requires a particular method to be used should advise the ship accordingly. 2.5 ACCESS TO SHIP 2.5.1 Means of access (gangways or accommodation ladders) Personnel should only use the designated means of access between ship and shore, or between ships. When a ship is berthed, at anchor or alongside another ship, the means of access should be close to the living accommodation, placed conveniently for supervision, and if possible away from the cargo manifold area. Gangways or other means of access should be properly secured and provided with an effective safety net. Suitable lifesaving equipment such as a lifebuoy should be available near the access point. 2.5.2 Lighting During darkness the means of access and the surrounding areas should be adequately illuminated. 2.5.3 Unauthorised persons Persons who have no legitimate business on board, or who do not possess the master's permission to be there, should be refused access. A crew list should be provided to the terminal security personnel who, in agreement with the master, should restrict access to the jetty or berth to people who can demonstrate legitimate business with the ship. 2.5.4 Persons smoking or intoxicated Personnel on watch on a chemical carrier must ensure that no one who is smoking approaches or boards the ship. Smoking on board must only take place in designated smoking areas. The company policy on drugs and alcohol must be strictly enforced.
2.6 NOTICES 2.6.1 Permanent Permanent notices should be displayed in conspicuous places on board, indicating where smoking and use of naked lights are prohibited, and where ventilation is necessary prior to entry. 2.6.2 Temporary On arrival at a terminal, a chemical tanker should display temporary notices at points of access to the ship, in English and other appropriate languages, to indicate the following: WARNING NO NAKED LIGHTS NO SMOKING NO UNAUTHORISED PERSONS In addition, when the chemicals being handled present a health hazard, further notices in appropriate languages should be prominently displayed stating: WARNING HAZARDOUS CHEMICALS
Local national or port regulations may require additional notices, and such requirements should be observed.
2.7 EFFECTS OF OTHER SHIPS AND BERTHS 2.7.1 Tugs and other craft alongside The number of craft which come alongside and the duration of their stay should be kept to a minimum. Subject also to port authority regulations, only authorised craft having the permission of the responsible officer, and where applicable the terminal representative, should be permitted to come alongside or remain alongside a chemical tanker while it is engaged in cargo operations. If an unauthorised craft comes alongside or operates in an area which may create a danger, it should be reported to the port authority and, if necessary, cargo transfer operations should cease. The resp6nsible officer should instruct personnel manning any craft alongside that the same safety regulations that apply on the chemical tanker must be observed on the craft. In the event of a, breach of the regulations operations should be stopped, and should not be restarted until the situation has been made safe. 2.7.2 Other tankers at adjacent berths Even when no cargo operations are being undertaken while at a terminal, dangerous concentrations of cargo vapour may be encountered if cargo or ballast handling, inerting, tank cleaning or gas freeing operations are being conducted by another tanker at an adjacent berth. In such circumstances appropriate precautions should be taken. 2.7.3 Chemical tanker operations at general cargo berths Where chemical tanker operations need to be conducted at general cargo berths it is unlikely that personnel on such berths will be familiar with the full range of safety requirements
relating to possible sources of ignition, or that cranes or other equipment will comply with the requirements for the design and installation of electrical equipment in hazardous areas. The master may therefore have to insist on precautions additional to those set out in this chapter. Such precautions could include restricted vehicular access, removable barriers, additional fire fighting equipment and control of sources of ignition, together with restrictions on the movement of goods and operation of cargo handling equipment. 2.8 WEATHER PRECAUTIONS 2.8.1 Wind conditions Most chemical vapours are heavier than air, so cargo vapours released during loading, gas freeing or accidental spills may concentrate in lower areas on deck, especially in conditions with little or no wind. Strong wind may create low pressure on the lee side of deckhouses or other structures, and thereby cause vapour to be carried in that direction. Personnel should be alert to either possibility. 2.8.2 Electrical storms During electrical storms in the immediate vicinity of the ship, all operations that may evolve flammable vapours should be stopped, including tank cleaning, gas freeing and ballasting. 2.8.3 Cold weather During cold weather, precautions should be taken to prevent equipment and systems from freezing. Attention should be given to pneumatic valves and control systems, fire lines and hydrants, steam driven equipment, cargo heating systems, pressure/vacuum valves etc. If fitted, heating arrangements should be used. Any water that has collected in a system should be drained off. Cooling water systems should be dosed with anti-freeze or drained. Water in a fire main or spray system should be circulated continuously, where possible. Special attention must be paid to emergency showers and eye-wash stations to ensure the availability of facilities. 2.9 OPENINGS IN DECKHOUSES AND SUPERSTRUCTURES Regulations require that windows and portholes in the superstructure within a certain distance of the cargo area must not open, and that openings are positioned to minimise the possibility of vapour entry. These design features must not be modified in any way. All doors (except when being used for access), portholes and other openings should be kept closed during cargo operations. Accommodation doors that have to be kept permanently closed when in port should be marked, but they should not be locked. Non-essential mechanical ventilation of internal compartments should be stopped, and air conditioning units operated on closed cycle or stopped if there is any possibility of toxic or flammable vapour being drawn into the accommodation. 2.10 ENGINE AND BOILER ROOM 2.10.1 Combustion equipment Boiler tubes, uptakes, exhaust manifolds and combustion equipment should be maintained in good condition as a precaution against funnel fires and sparks. In the event of a funnel fire, or if sparks are emitted from the funnel, cargo operations involving flammable products should be stopped and, at sea, the course should be altered to prevent sparks falling onto the cargo area.
2.10.2 Blowing boiler tubes Funnel uptakes and boiler tubes should not be blown in port. At sea they should only be blown in conditions where soot will be blown clear of the tank deck. 2.10.3 Cargo vapour It is important that flammable or toxic cargo vapour does not enter the engine room or boiler room spaces. Special attention should be paid to equipment in the engine room connected to the cargo area. Contingency plans should be prepared for the possibility of an accident or an emergency that could give rise to a situation where toxic or flammable vapours are likely to enter the machinery spaces. Consideration should be given to the possible effect that such vapour entry may have on personnel or the operation of equipment. Any necessary preventive actions should be taken, such as isolating the source, closing accesses and openings, shutting down mechanical ventilation systems or main machinery, or evacuation of the spaces. 2.11 SHIP/SHORE INSULATING AND EARTHING 2.11.1 Insulating In order to provide protection against static electrical discharge (arcing) during cargo hose connection and disconnection, the terminal should have ensured that hose strings and metal arms are fitted with an insulating flange or a single length of non-conducting hose, to create electrical discontinuity between the ship and shore. All metal on the seaward side of the insulating section should be electrically continuous to the ship, and all metal on the landward side should be electrically continuous to the jetty earthing system. The insulating flange or the single length of non-conducting hose must not be short-circuited; for example, an exposed metal flange on the seaward side of the insulating flange or hose length should not make contact with the jetty structure directly or through hose handling equipment. An explanation of the process is given in Appendix D.3.12. It should be noted that switching off a cathodic protection system is not a substitute for the installation of an insulating flange or a length of non-conducting hose. 2.11.2 Ship/shore bonding cables A ship/shore bonding cable is not effective as a safety device and may be dangerous. A ship/shore bonding cable should therefore not be used.
Although the potential dangers of using a ship/shore bonding cable are widely recognised/ attention is drawn to the fact that some national and local regulations may still require a bonding cable to be connected. If a bonding cable is insisted upon, it should first be visually inspected to see, as best possible, that it is mechanically and electrically sound. The connection point for the cable should be well clear of the manifold area. There should always be a switch on the jetty in series with the bonding cable and of a type suitable for use in hazardous areas. It is important always to ensure that the switch is in the open position before connecting or disconnecting the cable. Only when the cable is properly secured and in good contact with the ship should the switch be closed. The cable should be attached before the cargo hoses are connected and removed only after the hoses have been disconnected.
2.12 HOT WORK It is anticipated that owners and operators of chemical tankers will issue clear guidance to masters and crews on the control of hot work on board while the ship is in service. The following is intended to assist safety by indicating principal areas that should receive attention. 2.12.1 General Hot work means any work requiring the use of electric arc or gas welding equipment, cutting burner equipment or other forms of naked flame, as well as spark generating tools. It covers all such work, regardless of where it is carried out on board a ship, including open decks, machinery rooms and the engine room. Repair work outside the main engine room which necessitates hot work should only be undertaken when it is essential for the safety or immediate operation of the ship, and when no alternative repair procedure is possible. Hot work outside the engine room (and in the engine room when associated with fuel or lubrication systems) must be prohibited until the requirements of national legislation and other applicable regulations have been met, safety considerations taken into account, and a hot work permit has been issued. This may involve the master, owner's superintendent, shore contractor, terminal representative and port authority as appropriate. Hot work in port at a chemical terminal is normally prohibited. If such work becomes essential for safety or urgent operational needs, then port and terminal regulations must be complied with. Full liaison should be established with port and terminal authorities before any work is started. 2.12.2 Assessment of hot work The master is responsible for deciding whether the hot work is justified, and whether it can be conducted safely. Hot work in areas outside the engine room should not be started until a procedure has been discussed and agreed, and the master has informed the ship's owners or operators of details of the work intended. Before hot work is started a safety meeting under the chairmanship of the master must be held, at which the planned work and the safety precautions are carefully reviewed. The meeting should be attended at least by all those who will have responsibilities in connection with the work. An agreed written plan for the work and the related safety precautions should be made. The plan must clearly and unambiguously designate one officer who is responsible for the supervision of the work, and another officer who is responsible for safety precautions and communications between all parties involved. A flow chart to assist is shown opposite. All personnel involved in the preparations and in the hot work operation must be briefed and instructed on their own role. They must clearly understand which officer is responsible for work supervision and which for safety precautions. A written hot work permit should be issued for each intended task. The permit should specify the duration of validity, which should not exceed a working day. An example of a hot work permit is given in Appendix P. 2.12.3 Preparations/or hot work No hot work must be undertaken inside a compartment until it has been cleaned and ventilated. Tests of the atmosphere in the compartment should indicate 21% oxygen content by volume, flammable vapour as low as possible but not more than 1% LFL, and that the compartment is free from toxic gases. It is important to continue ventilation during hot work. No hot work should be undertaken on the open deck unless the area is free from flammable vapour and all compartments (including deck tanks) within a specified radius around the working area have been washed and freed of flammable vapour and/or inerted. Company or national regulations may give guidance on this distance. If no guidance is available, then the advice in ISGOTT should be taken into account.
All sludge, cargo-impregnated scale/ sediment or other material likely to give off flammable or toxic vapour, especially when heated, should be removed from an area of at least 10 metres around all hot work. All combustible material such as insulation should either be removed or protected from heat. Adjacent compartments should either be cleaned and gas freed to hot work standard, or freed of cargo vapour to not more than 1% LFL and kept inerted, or completely filled with water. No hot work should be undertaken in a compartment beneath a deck tank in use. Care should be taken to ensure that no release of flammable vapour or liquid can occur from non-adjacent compartments that are not gas free. An adjacent fuel oil bunker tank may be considered safe if tests using a combustible gas indicator give a reading of not more than 1% LFL in the ullage space of the bunker tank, and no heat transfer through the bulkhead of the bunker tank will be caused by the hot work. No hot work should be carried out on bulkheads of bunker tanks that are in use. All pipelines interconnecting with cargo spaces should be flushed, drained, vented and isolated from the compartment or deck area where hot work will take place. Hot work on pipelines and valves should only be permitted when the item needing repair has been detached from the system by cold work, and the remaining system blanked off. The item to be worked on should be cleaned and gas freed to a standard that is safe for hot work, regardless of whether or not it is removed from the hazardous cargo area. All other operations utilising the cargo or ballast system should be stopped before hot work is undertaken, and throughout the duration of the hot work. If hot work is interrupted for any reason for an extended period, hot work should not be resumed until all precautions have been rechecked and a new hot work permit has been issued. 2.12.4 Checks by officer responsible/or safety during hot work Immediately before hot work is started, the officer responsible for safety precautions should examine the area where it is to be undertaken, and ensure that tests with a combustible gas indicator show not more than 1% LFL, and, if the work is inside an enclosed space, that the oxygen content is 21% by volume. Adequate fire fighting equipment must be laid out and ready for immediate use. Fire watch procedures must be established for the area of hot work and in adjacent, non-inerted spaces where the transfer of heat may create a hazard. Effective means of containing and extinguishing welding sparks and molten slag must be established. The work area must be adequately and continuously ventilated. Flammable solvents must not be present, even for use in cleaning tools. The frequency with which the atmosphere is to be monitored must be established. Atmospheres should be retested at regular intervals and after each break in work periods. Checks should be made for flammable vapours or liquids, toxic gases or inert gas from non-gas free spaces. Welding apparatus and other equipment to be used should be carefully inspected before each occasion of use to ensure that it is in good condition and, where required, correctly earthed. Special attention must be paid to electric arc equipment to ensure that: • Electrical supply connections are made in a gas free space. • Existing supply wiring is adequate to carry the electrical current demanded without overloading and consequent heating. • Flexible electric cables laid across the deck have sound insulation. • The cable route to the work site is the safest possible, only passing over gas free or inerted spaces.
2.12.5 Action on completion of hot work The work area should be secured, and all special equipment used should be removed. The ship's owner or operator should be informed of the completion of all hot work allowed by the hot work permit. 2.13 USE OF TOOLS FOR SHIP'S MAINTENANCE 2.13.1 Power tools Although grit blasting and the use of mechanically powered tools are not normally considered to fall within the definition of hot work, both these operations should only be permitted under controlled conditions. Section 1 of the hot work permit is suitable (see Appendix P). The work area should not be subject to vapour release or a concentration of combustible vapours, and should be free from combustible material. The area should be gas free, and tests with a combustible gas indicator should give a reading of not more than 1% LFL. The ship must not be alongside at a terminal. There must be no cargo, bunkering, ballasting, tank cleaning or gas freeing operations in progress. The hopper and hose nozzle of a grit-blasting machine should be electrically earthed to the deck or the fitting to be blasted. There is a risk of perforation of pipelines when grit blasting or chipping, and great care must be taken over planning such work. Cargo and inert gas pipelines should not be blasted or mechanically chipped unless the entire ship is gas free. Adequate fire fighting equipment should be laid out and ready for immediate use. 2.13.2 Hand tools The use of hand tools such as chipping hammers and scrapers for steel preparation and maintenance may be permitted without a hot work permit. Their use must be restricted to deck areas and fittings not connected to the cargo system. The work area should not be subject to vapour release or a concentration of combustible vapours. The area should be gas free and clear of combustible materials. There must be no cargo, bunkering, ballasting, tank cleaning or gas freeing operations in progress. Work on cargo pipelines and inert gas pipelines should be subject to the same precautions as applies to power tools. • 2.14 PUMPROOMS AND ENCLOSED SPACES 2.14.1 Cargo pumprooms Cargo pumprooms, due to their location, design and operation, constitute a particular hazard and therefore necessitate special precautions. Cargo pumprooms should be continuously ventilated during all cargo operations. To meet the requirements of the IBC Code, they must be fitted with mechanical ventilation systems controlled from outside. Because of the potential for the presence of cargo vapours, such spaces should be ventilated for at least 15 minutes before entering and operating the equipment inside. Only authorised personnel should enter and operate equipment in cargo pumprooms. Leakage of toxic liquids and escapes of toxic vapours should always be suspected, because cargo pumprooms contain a large number of flanges, valve glands, pumps and couplings. Because pumprooms are enclosed spaces, the concentration of toxic and flammable vapours in their atmospheres might rise to dangerous levels. In the event of pump or pipeline leakage, the pumproom atmosphere must be tested for flammable and toxic vapours appropriate to cargoes recently handled, and the pumproom should only be entered if found safe. If entry becomes essential before a safe atmosphere is established, full personal protective equipment must be worn.
Cargo liquids from minor leaks should not be allowed to accumulate in pumproom bilges. If left to lie in place, there is the possibility of unsuspected vapours from former cargoes being released when the surface of the bilge water is disturbed. In particular this could occur when a chemical which is immiscible with and heavier than water has lain under the bilge water. Additionally, when pumping out accumulated liquids there is a risk of accidentally mixing an incompatible chemical with other chemicals already in a slop tank. Some cargoes are not allowed to be carried in tanks served by conventional below-deck pumprooms. 2.14.2 Enclosed spaces Those enclosed spaces in the cargo area that are not normally entered during the operation of the ship, such as ballast tanks, cofferdams, duct keels, pipe tunnels etc., may contain flammable or toxic vapours or be oxygen deficient. They must not be entered without a permit and only entered if proper ventilation of adequate capacity is provided. Proper procedures for entering such spaces must be established and adhered to (see Chapter 3 for detailed guidance). 2.15 SHIP'S READINESS TO MOVE At all times during discharge, loading and ballasting operations, alongside a berth or at an anchorage, the ship should be ready for departure at short notice in the event of an emergency. The ship's boilers, main engines, steering machinery, mooring equipment and other equipment essential for manoeuvring should be kept in a condition that will permit the ship to move away from the berth or anchorage at short notice in accordance with terminal and port regulations. Repairs and other work which may immobilise the ship should not be undertaken at a berth without prior, written agreement with the terminal. It may also be necessary to obtain permission from the local port authority before carrying out such work. 2.16 NAVIGATION Normal high standards of navigation, as described in the ICS Bridge Procedures Guide, should be maintained and any navigational restrictions (routeing, reporting requirements etc.) should be observed.
2.17 POLLUTION PREVENTION It is the responsibility of the master and those in charge of transfer operations involving cargo or bunkers to know the applicable pollution prevention regulations, and to ensure that they are not violated. Exercises should be held to train personnel in accordance with the applicable pollution contingency plan. See Chapter 8 for emergency responses and reporting requirements. There is increasing concern about all discharges from ships into the environment. Chapter 4 gives detailed advice on existing and anticipated controls. 2.18 FIRE FIGHTING AND FIRE PROTECTION EQUIPMENT
Fire fighting appliances should always be kept in good working order, tested regularly, and available for immediate use at all times (see Chapter 8 and Appendix H).
2.19 HELICOPTERS Helicopter operations in connection with chemical tankers are not routine operations, but in some ports it has become established practice to embark and disembark the pilot by helicopter, in particular on larger tankers and in bad weather. Helicopter operations must not be permitted over the cargo tank deck unless all other operations have been suspended and all cargo tank openings closed. Whenever helicopter services are used the safety measures recommended in the ICS Guide to Helicopter/Ship Operations should be taken into account. 2.20 TANK CLEANING AND GAS FREEING 2.20.1 Awareness of additional hazards Tank cleaning and gas freeing are operations that are frequently carried out on a chemical tanker. The numerous different chemical products involved, often toxic or corrosive or both, may expose the ship's personnel to additional hazards of cargo fumes or liquid, as well as injury from working with the extra equipment. See Chapter 7 for detailed guidance. Crew training is of the highest importance to allow understanding of the hazards involved in these operations, and the need to take necessary precautions. But it remains the master's responsibility to ensure that the personnel involved follow correct procedures and make proper use of personal protective equipment. 2.20.2 Use of tank cleaning agents Tank cleaning agents used on a chemical tanker may be toxic, corrosive or skin sensitive. When heated they may give off irritating fumes. Personnel handling cleaning agents should wear necessary personal protective equipment. 2.21 COMMUNICATION EQUIPMENT 2.21.1 Ship's radio transmission equipment During medium and high frequency radio transmissions significant energy is radiated, which can create a danger of incendive sparking by inducing an electrical potential in unearthed steelwork. The use of medium or high frequency main radio transmission equipment should therefore be prohibited in port and during ship to ship cargo transfers. If it is-necessary to operate the ship's radio in port for maintenance me agreement of the terminal and port authorities should be sought. Low energy transmissions of one watt or less, such as are used for VHF/UHF radios or satellite equipment, are not considered a hazard. The repositioning of satellite aerials, however, may involve the running of nonapproved drive motors within a shore hazardous zone, and consultation between the tanker and the terminal is advisable before the satellite terminal is operated. 2.21.2 Personal items Personal equipment such as mobile telephones and radio pagers, if switched on, can be activated remotely and a hazard can be generated by the alerting or calling mechanism and, in the case of mobile telephones, by the natural response to answer the call. In view of the widespread use of such equipment, appropriate measures should be taken to prevent its use within the cargo area. Visitors should be informed that such items should only be switched on in a safe area, such as within the ship's accommodation. Small battery powered personal items such as watches and hearing aids are not significant ignition sources when correctly used. However, portable domestic radios, electronic calculators, tape recorders, cameras and other non-approved battery powered equipment should not be used in the cargo area or wherever flammable vapour may be encountered. When in port, local regulations may prohibit the use of any portable electrical equipment.
ENTRY INTO ENCLOSED SPACES 3.1 General 3.2 Atmosphere in Enclosed Spaces 3.3 Requirements for Entry 3.4 Testing Before Entry 3.5 Entry into Contaminated Cargo Tanks 3.6 Entry After Confirmation of a Safe Atmosphere .1 General .2 Entry into cargo tanks .3 Entry into enclosed spaces separate from the cargo system 3.7 Work in Enclosed Spaces 3.8 Rescue from Cargo Tanks and Other Enclosed Spaces
ENTRY INTO ENCLOSED SPACES
This chapter gives guidance on procedures to follow when planning entry into an enclosed space that is not in normal daily use. On chemical tankers entry of personnel into cargo tanks is a common practice during cargo operations, and operators' instructions generally make special allowance for this. The following guidance is therefore intended to support company policy on training and operational practices, and provide some explanation of procedures. 3.1 GENERAL When it is intended that personnel should enter or work in an enclosed space that is not in normal daily use, great care should be taken to create and maintain safe working conditions, even if the duration of the work is to be short. Many fatalities in enclosed spaces have resulted from entering such spaces without proper supervision or adherence to agreed procedures. In almost every case the fatality would have been avoided if the simple guidance in this section had been followed. The rapid rescue of personnel who have collapsed in an enclosed space presents particular risk. It is a human reaction to go to the aid of a colleague in difficulties, but far too many additional deaths have occurred from impulsive or ill-prepared rescue attempts. The hazards and precautions associated with entering or working in enclosed spaces are outlined in this chapter. The normal oxygen level in fresh air is 21% by volume (but see Appendix J.7.2). Uncontaminated air with a slightly lower oxygen concentration can be breathed for some minutes before the effects become apparent. If the oxygen supply to the brain is depleted, victims will feel dizzy and have headaches before losing consciousness. This is particularly dangerous because they may not recognise that they are in danger or be capable of finding the way out of the space. They therefore become a risk to themselves and others. There is a danger of permanent brain damage after only four minutes in a very oxygen-deficient space. A successful rescue depends upon the victim being resuscitated in the shortest possible time. 3.2 ATMOSPHERE IN ENCLOSED SPACES When an enclosed space is left closed and unventilated for any length of time, the internal atmosphere may become unsafe to human life, either because it contains insufficient oxygen, or because it contains contaminants, or both. The oxygen content can be reduced naturally by the process of rusting or other oxidising, which absorbs oxygen from the air, or by the presence of inert gas. Contamination can come from sources such as stores. Decomposition of animal and vegetable oils and fats, a process known as putrefaction (or going off), can seriously deplete the oxygen content and evolve toxic gases, making proper ventilation of the space necessary prior to entry. However, it is possible that an oxygen deficiency is due to the air in the space being mixed with a contaminant such as cargo vapour. Cargo vapour or inert gas should always be anticipated in cargo tanks, and leakage into adjacent enclosed spaces separated from cargo
tanks by a single gas-tight bulkhead should be suspected. Similarly, cargo vapour or inert gas should be suspected in any space containing cargo handling or inert gas equipment. It is therefore vital that nobody ever enters an enclosed space without breathing apparatus until it has been confirmed that the atmosphere is safe and will remain so. As a general rule, enclosed spaces should not be entered unless it is absolutely necessary. Suitable notices should be prominently displayed to warn and inform personnel about the dangers of entering enclosed spaces. Instructions should clearly explain the precautions to be taken when entering tanks or other enclosed spaces, and listing any restrictions placed upon the permitted work. Company procedures should be such that the instructions are followed. On some ships, there is no door or hatch restricting passage from a pumproom into a duct keel. In these circumstances, the duct keel can be regarded as being ventilated by the pumproom extractor fans. Nevertheless, entry of personnel into the duct keel should be subject to a strict safety procedure involving prior notification to a responsible person. 3.3 REQUIREMENTS FOR ENTRY Prior to allowing personnel to enter an enclosed space, an entry permit should be issued. An example of an Enclosed Space Entry Permit is provided in Appendix Q. It is recommended that it should be signed by the master or a responsible officer expressly delegated by him. The entry permit should contain a clear indication as to its maximum period of validity (which should not exceed a normal working day), and the maximum time the space can be left unattended (which should not exceed four hours). It is critical to ensure that while personnel are within a space the levels of oxygen and any contaminants are frequently checked, and are within safe limits. If there is any doubt, suitable breathing apparatus and personal protective equipment should be worn, including a lifeline if practicable. The responsible officer should confirm that: • The space has been thoroughly ventilated by natural or mechanical means to remove any toxic or flammable gases, and to ensure an adequate level of oxygen throughout the space. • All personnel entering the space are properly trained in enclosed space entry procedures, and are familiar with safety and emergency procedures; they should be aware of the ship's procedure for issuing an enclosed space entry permit. • A trained crew member is standing by at the entrance. • A reliable system of communication has been established and is understood both by those entering the space and by the crew member standing by at the entrance. • The appropriate officer of the watch on the bridge or in the cargo control room or in the engine room is aware of the enclosed space entry operations. • Rescue procedures are in place. • Rescue equipment (including lifelines and harnesses) and breathing apparatus are readily available, and resuscitation equipment is prepared. The rescue procedures should clearly set out how to raise the alarm and summon assistance. Access to the space concerned, deployment of reserve equipment and communication between the emergency party and command centre should also be arranged. In the event of emergency, under no circumstances should an attending crew member enter the space before help has arrived and the situation has been evaluated, to ensure the safety of those carrying out rescue operations.
3.4 TESTING BEFORE ENTRY Before the space is entered it should be thoroughly ventilated. The time necessary to ensure thorough ventilation depends upon the size of the space, the capacity of the system used, the level of contamination and the efficiency of the ventilation system. Once the space has been ventilated, the atmosphere should be checked as follows: • The oxygen content should be sampled with a suitable and reliable detector: 21% oxygen is required for entry. The principle of measuring the oxygen level in an enclosed space, and interpretation of the figure obtained, must be thoroughly understood. The content of the world's air is constant at 21% life-sustaining oxygen, and 79% other gases which are breathable but do not themselves sustain life. Therefore, confirming that the oxygen level in a compartment is 21% ensures that there is no major component of the atmosphere that is not air. Nevertheless, this may not exclude trace volumes of toxic vapours. • If a flammable cargo vapour may be present, a combustible gas indicator should also be used. A content as low as practicable, but never more than 1% LFL, is required for entry. • If a toxic gas may be present, the correct toxic gas detector should be used to check that the level is below the safe operational exposure limit, depending on the nature of the previous contents of the space. Ventilation should be stopped about 10 minutes before tests are made and not restarted until the tests are completed. Sampling the atmosphere may require the use of breathing apparatus. A number of samples from different locations may have to be taken before the air in the whole space can be judged safe. Readings should be taken at several levels - top, middle and bottom. Suspected vapours which have a relative vapour density greater than that of air will be found at the bottom of any space, and those that have a relative vapour density less than that of air will be found at the top of a space. Vapour will also tend to remain where the ventilating airflow is least effective. Sampling and measurement should be done by personnel trained in use of the equipment, and sufficiently knowledgeable to understand the results obtained. It is vital that the correct instruments are used. A combustible gas indicator will not measure an oxygen deficiency, nor indicate the presence of toxic gas or the presence of flammable vapour in inert gas. All atmosphere testing equipment used should be of an approved type. It must be correctly maintained, prepared for use in accordance with the manufacturer's guidance, and regularly check-tested against standard samples. Even after a space has been made gas free and found to contain a respirable atmosphere, local pockets of gas should always be suspected. Cargo residues may be trapped in tank coatings or in residual scale. Generation of vapour should always be considered possible, even after loose scale has been removed. Hence a person moving around to different areas of a tank or compartment, or descending to the lower part after work in the upper part, should remain alert to the possible need for further tests to be made. ^ 3.5 ENTRY INTO CONTAMINATED CARGO TANKS Unless all necessary safety precautions can be followed, spaces should only be entered by personnel wearing breathing apparatus, appropriate protection against exposure to flammable, toxic or corrosive cargo vapours and, if practicable, a lifeline. In chemical tankers, operational entry into cargo tanks may be required before the atmosphere is certified as safe. A documented system should exist to ensure safety throughout any operation when entry of a contaminated cargo tank, or one suspected of being contaminated, is necessary.
3.6 ENTRY AFTER CONFIRMATION OF A SAFE ATMOSPHERE 3.6.1 General The guidance in this section is intended for all situations where it is intended to enter a space that is not in daily use by personnel on a ship, and is usually kept closed. As such, it describes procedures that will ensure personal safety in every case. 3.6.2 Entry into cargo tanks On chemical tankers entry of personnel into cargo tanks is a more common practice than it is on oil tankers. Chemical tanker operators' instructions often make special allowance for this when describing procedures for entry into cargo tanks. The intention is to avoid causing a comparatively routine event to distract everyone's attention, but equally to ensure that adequate checks are conscientiously made and recorded. It is essential that procedures remain sufficiently stringent to ensure the safety of personnel, but are not so disruptive that busy personnel who are familiar with the work become inclined to disregard them. Operators may therefore find it expedient to issue additional instructions that achieve those twin aims with regard to cargo tank entry during cargo operations, but insist on a more particular procedure at other times and for unusual entry into other enclosed spaces. It is also essential that the ship's safety management system is robust enough to make certain that instructions are followed. A system should be in place to indicate which cargo tanks are safe for entry by marking (or tagging) of appropriate tank entry hatches. The marking should be unambiguous, and procedures should be such that absence of the mark will forbid entry. Restricting the issue of entry permits, such that all cargo tanks which are safe to enter are shown on one entry permit, may be found to simplify the paper administration, avoid overlapping permits and the possibility of confusion as to which permit applies to which tank. If such a system is used there must be rigorous control to ensure cancellation of existing permits, and that the atmospheres of all named tanks are correctly tested at the time of issue so that an effective extension of a period of validity does not occur by default. It will be particularly important that it is supplemented by marking of tank lids with notices indicating which tanks are safe to enter. Inspection of cargo tanks after cleaning and before loading can require an independent surveyor to enter the tank. All relevant tank entry procedures must be observed (see Section 220.127.116.11). 3.6.3 Entry into enclosed spaces separate from the cargo system
On chemical tankers, entry into enclosed spaces separate from the cargo system should be treated with the same extreme caution as on all other ship types, and familiarity with practice in cargo tanks should not be allowed to induce any sense of complacency. In particular, it is recommended that a permit to enter is always restricted to a single compartment. Preparations for entry should be positively attended to, and pre-positioning of rescue apparatus near the entry point is recommended. No cofferdam, ballast tank, peak tank, fuel or lubricating oil tank, fresh water tank, duct keel not continuously open to a pumproom, void space, access trunk, or any other enclosed space should be entered unless all the precautions listed in Section 3.3 are strictly observed. The principal danger in such spaces is that rusting has depleted the oxygen content of the atmosphere to the point where it cannot support life. However, it is also possible for cargo vapour or inert gas to leak into such spaces and the atmosphere should therefore be checked for both oxygen content and cargo vapour before entry. The IBC Code requires a capability to ventilate all such spaces where cargo or cargo vapour may accumulate.
3.7 WORK IN ENCLOSED SPACES While personnel are inside the space, ventilation should be continued and the atmosphere monitored at regular intervals. If personnel begin to feel dizzy or unwell they should leave the space at once. Frequent atmosphere tests should be made, appropriate to the work in hand or to any change in conditions. In particular, tests should be made before each daily resumption of work. Tests should be so arranged that readings representative of the condition of the entire space are obtained. It is a normal practice in some trades for personnel to be sent into a cargo tank being drained of animal and vegetable oils or fats, in order to sweep the final traces towards the pump suction. Familiarity with the practice should not obscure the potential dangers of cargo generated vapours or an oxygen deficient atmosphere. Use of a personal alarm should be considered. Even after a cargo tank has been cleaned, there will always be a possibility of some cargo remaining, which could be a source of further flammable or toxic gas. Special care must therefore be taken whenever a pipeline or equipment in a tank is opened up, and additional tests should be made. If liquid or vapour escapes, the tank should be evacuated and not re-entered until the entire atmosphere has again been found to be safe. When removing sludge, scale or sediment from an enclosed space, periodic gas tests should be undertaken, and continuous ventilation should be maintained throughout the period the space is occupied. Whenever cargo pumps, pipelines or valves are to be opened, they should first be cleaned and gas freed. Many chemical tankers have individual cargo pumps and pipelines dedicated to each cargo tank. However, ships with fixed cargo lines that are common to several cargo tanks should take further precautions to isolate the tank where the work is being done. To avoid inadvertent operation, valves on all pipelines serving the space should be secured. Hot work in an enclosed space should only be carried out when all applicable regulations and safety requirements have been met and a hot work permit has been issued (see Section 2.12). 3.8 RESCUE FROM CARGO TANKS AND OTHER ENCLOSED SPACES It is imperative that regular drills and exercises to practice rescue from enclosed spaces are carried out and that all members of a rescue team know what is expected of them. When personnel are in need of rescue from an enclosed space, the first action must be to raise the alarm. Rescue and resuscitation equipment should already have been prepared. Although speed is often vital in the interest of saving life, rescue operations should not be attempted until the .necessary assistance has been obtained. There are many examples of lives having been lost through hasty, ill-prepared rescue attempts. Whenever it is suspected that an unsafe atmosphere has been a contributory factor to an accident, breathing apparatus and, where practicable, lifelines should be used by persons entering the space. A code of signals should be agreed in advance. The officer in charge of the rescue should remain outside the space, where he can exercise the most effective control.
CONTROL OF OPERATIONAL DISCHARGES FROM A CHEMICAL TANKER 4.1 Environmental Responsibility 4.2 Existing Controls .1 International regulations .2 Main requirements of MARPOL Annex n .3 Main requirements of the IMO Codes .4 Procedures and Arrangements (P&A) Manual for each ship .5 Environmental aspects of discharges into the sea 4.3 New Controls .1 Increased awareness .2 Air pollution .3 Ballast water management
CONTROL OF OPERATIONAL DISCHARGES FROM A CHEMICAL TANKER
This chapter provides background information on international regulations governing discharges/Torn ships into the environment, and points out the importance of these regulations to chemical tanker operations. In addition to cargo handling, the chapter refers to operational procedures which must be followed in respect of tank cleaning and the handling of slops and ballast, to comply with MARPOL and the IMO Codes. 4.1 ENVIRONMENTAL RESPONSIBILITY This guide is primarily concerned with the safety of the ship and its crew/ safe handling of cargo, and safe operation in ports and terminals. However, the growing importance of environmental care demands that the crews of chemical tankers have a clear understanding of the pollution regulations. Many additional tasks undertaken during cargo handling in a chemical tanker are dictated by a need to protect against any chance of discharge of cargo into the sea. These additional tasks must be performed safely, and an understanding of their purpose is a necessary part of chemical tanker operations today.
4.2 EXISTING CONTROLS 4.2.1 International regulations The International Convention for the Prevention of Marine Pollution from Ships 1973, as modified by the Protocol of 1978, known as MARPOL 73/78, is the principal regulation covering protection of the marine environment. MARPOL Annex I covers procedures for control of oil and oil-like substances, such as cargo or fuel, and applies to all ships including chemical tankers. MARPOL Annex II contains extensive regulations about the loading, carriage and discharge of noxious liquid cargoes, as well as the treatment of cargo residues remaining on board, washing of empty tanks and the final disposal of the contaminated washing medium. MARPOL Annex II affects all ships carrying noxious liquid cargoes in bulk. All personnel with responsibility for cargo operations on chemical tankers should be aware of the basic requirements of MARPOL, and take care that discharges into the sea never exceed the permitted limits. In addition to MARPOL there are two IMO Codes applicable to chemical tankers: • Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (the BCH Code). This was first adopted by IMO in 1971 as voluntary guidelines providing advice to the industry and to authorities. Under the subsequent provisions of MARPOL Annex II, chemical tankers constructed before 1 July 1986 and engaged in international trade must comply with this Code. • International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (the IBC Code), This was adopted by IMO in 1983. Under the provisions of SOLAS Chapter VII and MARPOL Annex II all chemical tankers constructed on or after 1 July 1986 must comply with the provisions of this Code. Both Codes have been amended several times since their adoption, in order to keep them up to date with best practice in the industry. The IBC Code also contains the current requirements
for safe handling of cargoes, and should be available on board for reference regardless of the age of the ship. The relevant Code or Codes applying to a particular ship must be carried on board. The IMO Codes are intended to produce a uniform set of regulations, allowing a ship to be issued with a Certificate of Fitness indicating compliance with the relevant Code. The certificate is accepted by the nations to which the ship may trade as an assurance of the ship's constructional safety, in a similar way to the international acceptance of Safety Equipment, Safety Construction, Load Line and other certificates issued to signify compliance with IMO standards. As with other certificates, the Codes require periodic reinspection of the ship during its lifetime to maintain validity. The implementation of these international regulations is through the approval by national administrations of a Procedures and Arrangements (P&A) Manual, individually developed for each ship. 4.2.2 Main requirements of MARPOL Annex II MARPOL Annex 11 categorises substances posing a threat of harm to the marine environment, with chemicals posing the greatest threat having the most severe controls placed upon their shipment and severe limitations on their discharge into the sea. A principal way of meeting the need to limit discharges to the sea is to reduce the residue that remains within a tank after unloading has been completed. Every chemical carrier is provided with pumping and piping arrangements specially designed to ensure that each tank designated for the carriage of controlled substances can be emptied so well that the quantity of cargo remaining afterwards is less than the minimum quantity specified in MARPOL. For each tank an initial assessment of the residue quantity has to be made, called a stripping test. The results of this test are recorded, and are used as the basis for the procedures described. Only when the residue is shown to be less than the quantity prescribed by MARPOL Annex II may the tank be approved for the carriage of a controlled substance. MARPOL then sets requirements for disposal of those residues, usually through dilution and use of shore reception facilities. It then specifies the records that must be kept of cargo work on board. Finally, it makes provision for inspections by authorities to confirm that the ship has complied. 4.2.3 Main requirements of the IMO Codes The IMO Codes address the safety of everyone involved and protection of the environment by ensuring that the ship will remain afloat after an assumed extent of damage, thereby minimising potential pollution and the uncontrolled release of cargo that could follow if a ship sank. They set detailed requirements for specific aspects of the ship: materials of construction; the separation of cargo, accommodation and machinery spaces; segregation of different types of cargoes; controls and instrumentation for cargo handling equipment; control of conditions within cargo spaces and venting from them; piping and pumping arrangements; electrical installations; fire fighting and extinguishing systems; and personal protective equipment. The IMO Codes then list cargoes, identifying the hazards each presents during carriage by sea. Cargoes which are assessed as presenting a safety or pollution hazard to such an extent as to warrant protection are required to be carried in designated ship types providing the appropriate degree of protection. Three ship types are prescribed, with the most hazardous cargoes receiving the most protection through further requirements applied to individual cargo tanks. 4.2.4 Procedures and Arrangements (P&A) Manual for each ship MARPOL Annex II requires that each chemical tanker be provided with a P&A Manual to achieve compliance with the regulations and to be able to demonstrate that compliance has been considered from the earliest design stage. The format of the P&A Manual and its contents must be as specified in MARPOL Annex II Appendix D, and be approved by the flag administration of the ship. The P&A Manual is concerned with the marine environmental
aspects of cleaning of cargo tanks, and the discharge of cargo residues that may or may not be mixed with a washing medium. The results of the stripping test are recorded in it. Ships' officers should familiarise themselves thoroughly with the P&A Manual, and adhere at all times to operational procedures with respect to cargo handling, tank cleaning, slop handling, residue discharge, ballasting and deballasting. The master is obliged to ensure that the ship does not discharge into the sea any cargo residues, or mixtures of residue with water, unless such discharges are made in full compliance with the operational procedures contained in the P&A Manual, and that the equipment required by the Manual for such discharge is used. The P&A Manual, together with the cargo record book and Certificate of Fitness, will be checked by the ship's own flag administration and by port state control officers in order to confirm full compliance with the requirements of MARPOL Annex II. 4.2,5 Environmental aspects of discharges into the sea Even after careful unloading, final disposal of residues may only be carried out in accordance with approved procedures and arrangements. It is necessary for tanks that have contained some specified cargoes to have a first rinse at the unloading port, called a pre-wash, and the initial washings discharged to shore reception facilities (usually the cargo receiver). Pre-wash sets a minimum required level of dilution of cargo residue for environmental protection. It has no direct relevance to preparing a tank for its next cargo. The commercial justification for any further tank cleaning is not addressed by authorities, although handling and disposal of washings must continue to take account of MARPOL. When a tank is washed with a washing medium other than water which would itself require control if carried as a cargo, discharge or disposal of the strippings will be governed by the provisions of MARPOL applying either to the washing medium or to the original cargo, whichever are the more severe. Discharge into the sea of cargo residues and tank cleaning products is strictly controlled. It is recommended that any discharge should be as far from land as practicable. Any discharge of effluent containing controlled substances (except in an emergency situation) is subject to a maximum concentration of the substance in the ship's wake or the dilution of substances prior to discharge, and must take account of the following: • A maximum quantity of such substance per tank. • The speed of the ship during the discharge. • The minimum distance from the nearest land during discharge. • The minimum depth of water during discharge. • The need to carry out the discharge below the water line. Some areas of the sea are designated as special areas in which even more stringent discharge criteria apply. Discharge overboard in port is always prohibited by local, national or regional standards that are usually supplementary to MARPOL, rather than in conflict with it.
4.3 NEW CONTROLS 4.3.1 Increased awareness It is now recognised that almost any discharge from a ship into the surrounding environment needs to be carefully considered in advance. Not only are chemical cargo residues, oily water from machinery room bilges and overboard disposal of garbage strictly regulated, but funnel exhausts and ballast water have now been identified as requiring control. 4.3.2 Air pollution Control of Ozone Depleting Substances (ODS), such as halogenated hydrocarbon gases, was established internationally in the early 1990s. In 1997, IMO adopted Annex VI to MARPOL,
addressing ships' emissions that are considered to be harmful to the atmosphere, or which can settle on land or into the sea. Funnel emissions of different oxides in engine and incinerator exhausts are generally not susceptible to daily adjustment by a ship's crew, but will be dependant upon the grade of fuel used and the condition of the engines. However, the crew will be involved in control of cargo vapours by on board techniques, such as vapour return to shore while loading, reducing excess discharge of inert gas, and avoiding unnecessary evaporation of liquid cargo into the atmosphere while cleaning tanks. While these regulations are not yet (2002) in force internationally, they will become important once ratified by enough countries to give them effect. 4.3.3 Ballast water management The intent of ballast water management is to minimise the transfer of marine organisms from one geographical region to another. The discharge of ballast water is now known to be responsible for the introduction of alien species into sensitive coastal waters, and the demand for ballast water management is an aspect of quarantine procedures rather than traditional pollution controls. IMO is seeking to encourage establishment of a single regime worldwide, in the manner of other Conventions, so that the present various requirements become standardised.
PRECAUTIONS DURING CARGO OPERATIONS 5.1 Introduction 5.2 Responsibility 5.3 Cargo Systems .1 Ship and shore cargo connections .2 Cargo pumprooms .3 Isolation of cargo tanks and piping systems .4 Cargo tank venting .5 Static electricity precautions .6 Pressure surge 5.4 Liaison Between Ship and Shore .1 Exchange of cargo information .2 Loading plan .3 Ship/Shore Safety Checklist .4 Communications during cargo operations 5.5 General Cycle of Cargo Operations 5.6 Preparation for Cargo Operations .1 Ship checks prior to arrival .2 Ship checks after arrival but prior to cargo operations .3 Joint ship and shore liaison, and checks prior to cargo operations 5.7 Preparing a Cargo Tank Atmosphere .1 General .2 Receiving nitrogen from shore .3 Preparations for receiving nitrogen from shore 5.8 Cargo Loading .1 General .2 Use of compressed gas .3 Topping off .4 Clearing shore pipelines .5 Clearing cargo hoses .6 Completion of loading 5.9 Disconnection of Cargo Hoses 5.10 Cargo Care During the Voyage 5.11 Cargo Unloading .1 General .2 Adding nitrogen to maintain overpressure .3 Sweeping of cargo residues. .4 Completion of discharge 5.12 Ballasting and Deballasting 5.13 Tank Cleaning and Gas Freeing 5.14 Ship to Ship Transfer .1 General .2 Responsibility .3 Communications .4 Navigational warnings .5 Weather conditions and limitations .6 Pre-transfer preparations on each ship .7 Cargo transfer operations .8 Completion of cargo transfer
PRECAUTIONS DURING CARGO OPERATIONS
This chapter outlines the range of safety precautions to be taken before and during the sort of cargo operations that are normally encountered on chemical carriers. It expands upon the precautions given in Chapter 2, including safety advice on purging and ballasting, and on ship to ship transfers. 5.1 INTRODUCTION The following procedures should be considered as general guidance only. There are large variations in the design of cargo containment and cargo handling systems, and specific instructions should always be prepared for inclusion in the ship's cargo handling manual. These instructions should be carefully studied and become familiar to all personnel involved in cargo handling operations. A chemical carrier's cargo containment and handling systems will have been carefully designed, and will have been constructed under strict supervision, to comply with the requirements of the IMO Codes and the SOLAS and MARPOL Conventions, in order to transport and handle safely the chemicals that the ship is certified to carry. However, the required level of safety in cargo operations can only be achieved if all parts of the cargo systems and equipment are maintained in good working order. Similarly, the personnel involved in cargo operations must be fully aware of their duties and be thoroughly trained in the correct cargo handling procedures and use of the equipment. Training in emergency procedures is particularly important (see Chapter 8). 5.2 RESPONSIBILITY It is the responsibility of the master to ensure that the officers and crew are properly and correctly informed of their duties, and understand how to fulfil them. It is the responsibility of the ship's owner or operator to ensure the master has the resources to achieve this. The master is responsible for the safety of the ship during all cargo operations. The master or a responsible officer appointed by him should be present whenever cargo operations are in progress, and be satisfied that all equipment in use or likely to be used is in good working condition. In port, the master should ensure that there is proper liaison between the responsible officer on the ship and his counterpart at the shore installation (see Ship/Shore Safety Checklist in Appendix L). Those personnel should establish the programme for all cargo operations, and the procedures to be adopted in the event of an emergency. Details of emergency contact names, titles or positions, telephone numbers etc. should be exchanged before cargo operations begin. Any special safety requirements of the shore installation should be brought to the attention of ship's personnel involved. Responsibility for safety is shared by everyone concerned, and all must be constantly alert to inherent dangers in the carriage of chemicals by sea.
5.3 CARGO SYSTEM
5.3.1 Ship and shore cargo connections The connection at the manifold of hoses or metal cargo arms for cargo handling is the primary cargo connection between ship and shore, and it is essential that both parties take proper care preparing for the connection. Flange faces, gaskets and seals used at this point should be clean and in good condition. Minimum standards for hoses are laid down in the IBC Code. The hoses should be in good condition and installed with gaskets, which are suitable for the chemical product to be handled. A bolt should be fitted in every hole, and tightened correctly and evenly. Nuts and bolts should be of the correct size and material, and damaged bolts should not be used. Improvised arrangements using G-cramps or similar devices must not be allowed for flange connections. Care should be taken to protect manifolds from mechanical damage. Reducers and spoolpieces should be made of suitable material compatible with the cargo, and comply with relevant industry standards. Whenever it is intended to use manifold reducers or spoolpieces made of a material other than steel, their use should be agreed by the ship and terminal. When long reducers or spoolpieces are used the resulting length must be properly supported to avoid exerting excessive cantilever force. Every manifold end should have a removable blank flange, made of steel or other approved material. Before removing a blank flange, a check should be made to ensure that the section of pipeline between the last valve and the blank does not contain cargo, possibly under pressure. Precautions must be taken to prevent any spillage. Permanent means for the retention of any slight leakage at ship and shore connections must be provided. If leakage develops from a deck pipeline, valve, hose or metal arm, all operations through that connection should be stopped and the situation treated as an emergency until the cause has been identified and the defect remedied. As a general rule, terminal hoses will be used for the connection between ship and shore. During connection, and when connected, flexible hoses should be suspended by suitable equipment to ensure that they are not subjected to excessive bending or liable to be crushed between the ship and the jetty. As the tanker rises or falls as a result of tide or cargo operations, the hose strings should be adjusted so as to avoid undue strain on the hoses themselves, the connections or the ship's manifold, and to ensure that the radius of curvature of the hose remains within the limits recommended by the manufacturer. For more detailed information see Appendix K. If metal cargo arms (sometimes referred to as hard arms) are used, the installation arrangements will have taken account of tidal range, the freeboard of the largest and smallest tankers for which the berth was designed, minimum and maximum distances that manifolds are set back from the deck edge, limited changes in horizontal position due to drift-off and ranging, and maximum and minimum spacing when operating with other arms in the bank. These limits should be thoroughly understood by operators, and alarms for excessive range and drift regularly tested. If range or drift alarms are activated while in service all cargo transfer operations should be stopped and remedial measures taken. Mechanical loading arms should be supported in such a way that they do not put excessive force on the manifold. 5.3.2 Cargo pumprooms On tankers equipped with a cargo pumproom, this is a potentially hazardous enclosed space. The pumproom precautions set out in Section 2.14 should be observed before and during all cargo handling operations involving the pumproom. Pump alarms and trips, level alarms etc. should be tested regularly, and in any case before commencing cargo handling operations, to ensure that they are functioning correctly. The results of such tests should be recorded. Bulkhead glands around driveshafts between the pumproom and an adjacent machinery space should be checked and adjusted or lubricated as necessary to ensure an efficient gas-tight seal. During all cargo operations, including loading, the pumproom should be inspected at regular intervals to check for signs of leakages from glands, drain plugs and drain valves, especially those fitted to cargo pumps. If the pumps are in use, pump glands, bearings and bulkhead glands should be checked for overheating. In the event of leakage or overheating the pump should be stopped. No attempt should be made to adjust pump glands on rotating shafts
while the pump is in service. No repairs should be undertaken on cargo pumps, their associated relief valves or controls systems while the pumps are running. Pumproom bilges should be drained of any liquid that has leaked from glands, pipelines or valves; such liquid is usually transferred into a slop tank for contaminated liquids. Not only is this good practice for cleanliness and reduction of vapours within the space, but it will avoid the possibility of incompatible cargoes becoming inadveriently mixed. It should be possible, when alongside a terminal, to transfer contaminated liquids directly to shore reception facilities. 5.3.3 Isolation of cargo tanks and piping systems When a single parcel of cargo is carried in several tanks served by a common pipeline system, containment within each tank depends upon the tightness of the inlet valve. Due to the pressure differential on either side during sequential loading into or discharge from such tanks, the tightness of a single valve should not be relied upon to prevent the entry or escape of cargo. It is advisable to achieve two valve separation between completed tanks and pump pressure in the pipeline. Regular checks should be made on completed tanks to ensure that the level of cargo does not change. More thorough segregation may be necessary when different parcels of cargo are carried in tanks served by common systems. In particular when carrying toxic cargoes, it is a requirement that cargo piping and pumps, as well as tank venting systems, are separated from those containing other products, to prevent any leakage causing toxic contamination of non-toxic products and subsequent exposure of personnel unaware of the contamination. Ships with common pipeline systems can achieve the separation required when carrying toxic cargoes by inserting two blank flanges (spectacle plates) with a bleed drain in between, or by removing a spoolpiece and using blank flanges strong enough to withstand the pressure expected. The engineering principle of using two stops, with a provision for detecting if one of the stops does not hold tight, ensures that a leak can be spotted immediately. The requirement is met on many chemical tankers by having separate pumps, pipelines and vents so that segregation is achieved by design. When blanks or a removable spool piece have been used, attention should be paid to restoring the system when the extra separation is no longer needed. 5.3.4 Cargo tank venting Venting of cargo tanks during cargo transfer or cargo related operations must be carried out in accordance with applicable international, national, port and-terminal regulations. Tank vent system outlets are located at a safe distance from all areas where personnel who are not involved in cargo work may be present, to ensure that toxic vapours are diluted to a safe level of concentration before they can reach such an area. The safe distances specified depend on the severity of the toxic hazard. In all cases the principles described in the IMO Codes will have been met by the ship's design. The cargo tank venting system should be set for the type of operation to be performed. Cargo vapour displaced from tanks during loading or ballasting should be vented through the installed venting system to atmosphere, except when return of the vapour to shore is required. The cargo or ballast loading rate should not exceed a rate of vapour flow within the capacity of the installed system. In the case of ships fitted with a venting system which is common to several tanks, it is important to remember that vapours (or liquid in the event of overfill) may pass through the venting system from one tank into another, and thereby cause contamination of cargo or tank atmosphere. A required level of maintenance and inspection will be necessary to ensure the cleanliness of the venting system, and in particular of the P/V valves, high velocity valves and devices to prevent the passage of flame into cargo tanks. Particular attention should be given to the possibility of flame screens becoming blocked by dirt, freezing water, or vapour condensation from certain chemical cargoes - e.g. those with high melting points or liable to polymerise -since blockage can severely jeopardise tank integrity.
The IBC Code requires the ship to be able to return vapours of most toxic chemicals to shore. When a tank is connected to a vapour return line, it is important to keep a safe pressure balance between the ship and shore. The vapours should be evacuated fast enough to keep the pressure in the tank below the set opening pressure of any pressure relief valve in the tank venting system; IMO guidelines recommend a maximum tank pressure of 80% of the set pressure. It is thus critically important clearly to agree in advance with the shore terminal management what the liquid loading rate and the pressure at the vapour connection will be, and to plan how they will be controlled. Liquid should not be permitted to enter the vapour return line. If liquid gets into the vapour line it will cause the cross section available for the flow of vapour to be reduced, as a result of which the pressure inside the tank can rise rapidly. Loading should be suspended until the pressure is released, and the presence of liquid dealt with. Connection of hoses intended for vapour transfer to manifold flanges of pipelines for liquid transfer is prevented by a stud permanently fixed between two bolt holes in the presentation flange of the ship's vapour return manifold. The stud will fit into a corresponding additional hole in the flange of the shore vapour hose. Vapour connections should also be identified by painting and stencilling in a standard way (see Figure 5.1).
5.3.5 Static electricity precautions, The primary concern about static electricity is the possibility of generating an incendive spark within a flammable atmosphere. Inerting a tank can prevent the existence of a flammable gas mixture so that no hazard will exist. Appendix D gives advice about the generation of static electricity due to the passage of a liquid through a hose or pipeline, and turbulence within a tank. In normal circumstances the charge generated is released instantaneously to earth (the ship's structure) because the liquid conducts it, and design features of cargo tank internals will avoid its build up. The problem is greater on very large tankers equipped with large
individual tanks than it is on the smaller size of chemical carriers with extensive subdivision and multiple cargo tanks. Problems from static electricity are most likely to arise when loading cargoes known as static accumulators, often highly refined petroleum products. Appendix D.3.4 explains that for most static accumulators the presence of water presents an increased opportunity for static generation. It is therefore important, quite apart from cargo quality requirements, to make sure that lines which have been flushed with water have been thoroughly drained and that the bottom of the tank is dry before starting to load a static accumulator cargo. At the initial stage of the loading operation, it is important that the loading rate is limited. Until the bottom longitudinals and tank suction are covered, loading speed of the liquid in the pipeline should not exceed a linear velocity of 1 metre per second (m/s), which corresponds to the following loading rates: Pipeline diameter
200 mm 150 mm 100mm
115 cubic metres per hour 65 cubic metres per hour 30 cubic metres per hour
Thereafter, loading may be increased to a maximum pipeline speed of 7 m/s. Experience indicates that hazardous potentials in respect of static electricity do not occur if the velocity is below 7 m/s. However, where well documented experience demonstrates that higher velocities have been safely used, an appropriately higher limit than 7 m/s may be employed. 5.3.6 Pressure surge It is a golden rule of tanker operations that a valve should never be shut against a liquid flow. Pressure surges can be created when the flow in a liquid is stopped too quickly. The potential hazards of pressure surges (shock pressure, known as water hammer or liquid hammer) resulting from rapid operation of valves should be emphasised to all personnel engaged in cargo transfer. The hazard is greatest when cargo is being transferred over long distances and at high velocity. If a valve is shut too quickly under these conditions the deceleration of the large column of liquid in the line sets up shock waves which can travel up and down the line causing extremely high surge pressures. The cargo hose is most vulnerable to failure in these circumstances. A full description of the pressure surge phenomenon is given in Appendix G. The following precautions should be taken to avoid pressure surge during cargo transfer: • Shutdown procedures should be in place, with the intent that pumps are stopped and upstream valves are closed first. Except in an emergency, unplanned shutdowns should be avoided. Special care is needed with automatic high level shutdown valves, which may close due to loss of power, or as a result of an external event unrelated to the ship. • During loading, when flow is diverted from one tank to another, the valves on the tank about to receive cargo should be fully opened before the valves on the tank being isolated are shut. When loading is completed, the flow should be stopped by the terminal using shore valves to prevent overstressing the cargo hose. During discharge, pump discharge valves should be shut or the pump stopped before manifold valves are closed or valves in the shore pipeline or tank farm are shut down.
5.4 LIAISON BETWEEN SHIP AND SHORE
5.4.1 Exchange of cargo information Operations concerning cargo handling, tank cleaning and pre-wash, ballasting and bunkering require an exchange of information between the ship and terminal before the ship arrives or after arrival. Each ship or company should have procedures for information to be exchanged between ship and terminal before a cargo operation commences. The following is a possible checklist of items that could be considered for inclusion in such an information exchange: 1. The maximum draught of the ship and maximum light freeboard. 2. Cargo specifications, to include the proper bulk shipping names, the nominated quantities to be transferred, expected temperature during transfer, flashpoint (where applicable), specific gravity, the MARPOL pollution category if applicable, and any viscosity and solidifying information. 3. Availability of emergency and health data for each cargo to be handled, 4. Where the ship has part cargoes, which will remain on board, the cargo name, volume and tank distribution of each cargo. 5. Any unusual characteristics of the cargo requiring special attention. 6. Proposed disposition of nominated cargo and preferred order of loading or discharge. 7. Details of cargo tank preparation for loading, including previous cargo carried, method of tank cleaning (if any), state of the cargo tanks and lines, and water dips in cargo tanks (where applicable). 8. Number and sizes of hoses or arms to be used, manifold connections required for each cargo to be handled and any limitations on the movement of hoses or arms. 9. Maximum pumping rates and maximum pressure available at the ship/shore cargo connection, and any restrictions due to inherent properties of the cargo. 10. Communication system for cargo control, including the signal for emergency stop. 11. Restrictions relating to electrostatic properties of a product, and precautions to prevent the generation of hazardous static electricity charges. 12. The use of automatic emergency shutdown valves, and their closing period. 13. Tank venting requirements and details of any required vapour return lines. 14. Tank environmental control requirements, e.g. drying and inert gas, and quality of inert gas (if applicable) 15. Whether foot samples or normal samples are to be taken, and any suspension of cargo operation while samples is being analysed. 16. Terminal or port regulations on pre-washing of cargo tanks alongside the berth, and details of reception facilities available to receive slops (if applicable). 17. Mandatory pre-wash requirements, cargo names and quantity of washings for discharge to reception facilities, and quantity, quality and disposition of slops (if applicable). 18. Whether alongside tank cleaning is required in addition to pre-wash?
19. Ballasting or deballasting requirements of the ship: if deballasting, the disposition, composition and quantities of ballast on board together with time required for discharge; if ballasting, the approximate time of commencement and the duration of ballasting into ballast or cargo tanks that will impinge upon cargo operations. 20. Proposed bunker handling to be done during port visit, including time, location of bunker manifold, whether delivery is to be from barge or quay, and whether cargo transfer will be interrupted. 21. Any other limitations at the terminal. 22. Measures to prevent accidental exposure of personnel to cargo vapours or contact with cargo liquids. 23. Action to be taken in the event of spills or leaks. 5.4.2 Loading plan On the basis of the information exchanged, an operational plan for the order of cargo handling should be made by the responsible officer covering the items felt to be significant, including a cargo plan showing cargo distribution. The operational plan should include indications of the expected duration of the operation, and the sequence in which the ship's tanks are to be loaded or discharged. 5.4.3 Ship/Shore Safety Checklist The Ship/Shore Safety Checklist concerns the safety of the ship, the terminal and all personnel, and should be completed jointly by the responsible officer and the terminal representative. Each item should be verified before it is ticked. This will entail a physical check by the two persons concerned which should be conducted jointly where appropriate. The completed checklist is of no value if it is merely regarded as a paper exercise. A full specimen of the Ship/Shore Safety Checklist is given in Appendix L. It is emphasised that some of the items on the checklist will require several physical checks or even continuous supervision during the operation. 5.4.4 Communications during cargo operations . To ensure the safe control of cargo operations at all times, it should be the responsibility of both parties to establish, agree in writing and maintain a reliable communications system. Before loading or unloading commences the communications system should be adequately tested. A secondary stand-by system should also be established and agreed and tested. Allowance should be made for the time required for action in response to signals. The use of one radio channel by more than one ship/shore combination should be avoided.
5.5 GENERAL CYCLE OF CARGO OPERATIONS The following sequence outlines a general cycle of cargo operations on chemical tanker. Supplementary comments where relevant are made in the sections which follow.
Every chemical tanker is required to have an approved Procedures and Arrangements (P&A) Manual complying with MARPOL Annex II, which gives instructions applying to that ship. 5.6 PREPARATION FOR CARGO OPERATIONS 5.6.1 Ship checks prior to arrival When approaching a port to load or discharge cargo, the following important checks should be made by the ship in time to allow any necessary work to be done: 1. On tanks in which cargo is to be transferred, in-tank instrumentation such as level gauges, level alarms and thermometers should be tested for operation and accuracy, and remote system controls tested where appropriate. High level alarms and tank overflow control alarms are safety critical components of the cargo transfer system, and loading should not commence if pre-transfer checks find them at fault. 2 . Hatches, lids and openings to cargo tanks that are not required to be open for a specific reason should be firmly closed. 3. Cargo pipelines and crossover valves should be checked, and all drains closed and secured. 4. All ship's cargo and bunker pipelines not in use should be securely blanked and fully bolted at the manifold. Unless it is to be used, the stern cargo pipeline should be isolated from the tanker's main pipeline system at a point forward of the aft accommodation, by blanking or the removal of a spool piece. 5. Where loading or discharging is to be via a cargo pumproom, the pumproom ventilation system should be checked to ensure readiness for operation throughout the cargo operations. 6. Cargo area deck lighting should be checked and confirmed as being in full working order, with special attention given to the area of the ship to shore cargo connection and hose handling equipment. 5.6.2 Ship checks after arrival but prior to cargo operations Before any cargo transfer starts, the responsible officer should be satisfied that the applicable precautions set out in Chapter 2 are being observed. The use of safety checklists, appropriately
adapted for the specific ship, is strongly recommended. The following important checks should be made by the ship at this stage: 1. Information should be sought on any forecast of adverse weather conditions which may require operations to be stopped or transfer rates reduced. 2. Certain cargoes require the vapour that is displaced by incoming cargo to be returned to the shore facility. The responsible officer should ensure that the ship and the shore vapour system are compatible, and that the system will operate in compliance with local and terminal regulations. 3. The characteristics of the product must be known, usually in the form of a cargo information form or data sheet indicating, among other things, health hazards, specific gravity, temperature, vapour pressure, reactivity with other materials or cargoes, heat sensitivity, risk of exothermic self-reaction, toxicity and general safe handling practices. It is desirable that initial response to emergencies is clearly shown. An example data sheet is in Appendix M. 4. If a cargo liable to self-reaction is to be loaded, correct arrangements should be made for conditions and limitations in the inhibitor certificate to be met for the duration of the voyage. An example of an inhibited cargo certificate is shown in Appendix N. 5. Normally tanks to be loaded are pre-inspected for cleanliness by an independent surveyor. This can vary from a superficial visual inspection from the deck, to a very detailed inspection inside the cargo tank in which bulkheads are wall-washed and thoroughly checked. The responsible officer should satisfy himself that the tanks to be so inspected are well ventilated and safe to enter, and are marked as being safe to enter. Tank entry procedures should be complied with. When a tank is entered for inspection the surveyor should be accompanied by the responsible officer or a person delegated by him. 6. Tanks passed for loading should be tightly secured with all cargo openings closed. 7. All sighting ports and ullage plugs should be closed and secured, unless expected to be used during handling of the cargo about to be loaded. If openings are required to be open for venting purposes, each opening should be protected by a flame screen designed for that opening and kept clean. 8. When not in use, sea suction and overboard discharge valves connected to cargo and ballast systems must be securely closed and lashed, and may be sealed by shore authorities. In-line blanks should be inserted where these are provided. When lashing is not practicable, valves should be suitably marked to indicate clearly that they are to remain closed. 9. Before cargo handling is started, all deck scuppers and any open drains onto the jetty must be effectively plugged to prevent spilled cargo escaping into the water around the tanker or onto the terminal. Accumulations of rainwater should be drained periodically and scupper plugs replaced immediately afterwards. Contaminated water should be transferred to a slop tank or other suitable receptacle. 10. Cargo manifolds should be ready for connection to shore hoses, but with blank flanges removed only on those lines to be used, and only on the connecting side of the ship. 11. He loading is via a cargo pumproom, the pumproom ventilation system should be working throughout the operation, and all drains and non-essential valves in the pumproom must be closed and secured. 12. Accommodation doors and portholes overlooking the cargo area should be shut. If stern loading is to be undertaken, it may be necessary to provide special advice to the crew. 13. The cargo venting system should be appropriate for the cargo operation. 14. Intakes for central air conditioning and mechanical ventilation systems should be checked for correct setting. 15. Means should be provided for the prompt removal of any spillage on deck.
16. Fire fighting equipment should be inspected, and ready for immediate use. 17. Correct personal protective clothing and breathing apparatus, appropriate to the cargo, should be immediately available, and should be worn as necessary. Just prior to commencing cargo transfer, the responsible officer should check that the cargo pipeline system is set correctly, that correct valves are open and that pipeline valves not being used (including drop valves) are closed. 5.6.3 Joint ship and shore liaison, and checks prior to cargo operations A liaison meeting should be held with the responsible terminal staff, at which the operational plan for the order of cargo handling can be agreed. In addition to the checks in paragraph 5.6.2, the following joint ship and shore checks in co-operation with a terminal representative are recommended: 1. That the Ship/Shore Safety Checklist has been completed satisfactorily. 2. That local and terminal regulations have been ascertained and are being observed. 3. That agreement has been reached with the responsible terminal representative about signals to indicate stand-by, start operation, slow down and stop operation. 4. That when shore-supplied nitrogen is to be used for inerting cargo tanks, the procedure for handling it has been agreed. 5. That the sequence of cargoes and pumping rates has been agreed. 6. Whether ship or shore will order pumps to be stopped on completion. 7. That emergency shutdown procedures, and action to be taken in case of fire or other emergency, have been agreed. 8. That if an insulating flange is used in the hose connection, its insulation has not been impaired. 5.7 PREPARING A CARGO TANK ATMOSPHERE 5.7.1 General For some cargoes the IBC Code requires vapour spaces within cargo tanks to have specially controlled atmospheres, principally when the cargo is either air reactive resulting in a hazardous situation, or has a low auto-ignition temperature, or has a wide flammability range. See Chapter 6 for guidance on establishing the correct atmosphere in a tank, either inerting to prevent the formation of flammable mixtures of cargo vapour and air, or padding to prevent chemical reaction (between oxygen and the cargo. It may also be necessary to reduce the humidity (dewpoint) of the atmosphere within the cargo system. The extent of atmosphere control to protect the quality of the cargo will normally be specified by the cargo shippers. Some cargoes are extremely sensitive to commercial contamination or discoloration, and for quality control reasons are carried under a blanket of nitrogen that is very pure and which must often be obtained from shore. 5.7.2 Receiving nitrogen from shore It is a frequent practice at chemical loading ports to control the atmosphere in cargo tanks with nitrogen supplied from shore, for the purpose of drying a tank and its associated piping system, purging a tank before loading the cargo or padding cargo in a tank. The nitrogen may be supplied at high pressure (up to 10 bar) and at a high flow rate. Agreement on the procedure for handling the nitrogen is paramount, and should be part of the pre-loading checklist between ship and shore, with emphasis on a clear understanding of the transfer rate and pressure.
Although the operation is an important stage in cargo handling, it is also potentially hazardous because high pressure gas is being introduced into a tank which is not designed to withstand internal pressure, and whose structure may fail at less than 0.5 bar overpressure. The associated risks of the operation should therefore be thoroughly understood. Procedures should be in place to ensure safety during the operation, and all personnel involved should be made conversant with those procedures. Bit is possible to overpressurise and even rupture a cargo tank if the nitrogen supply from shore is at too high a flow rate or too great a pressure. There have been incidents where structural damage has occurred.
Figure 5.2 Damage in a cargo tank due to overpressurisation during purging with nitrogen
When a liquid is being loaded through the cargo manifold and pipeline system on a chemical carrier/ the existing atmosphere in the tank can escape through a vent system that is notably smaller than the liquid filling line, because friction and turbulence are far greater impediments to liquid flow than to gas flow. Ships are designed with this in mind. However, when a gas is being introduced through the liquid filling line, especially a gas under pressure that will expand within the tank, the same condition does not apply, and the disparate sizes between inlet and outlet can allow an overpressure to develop. To avoid such an eventuality, the outlet for the existing atmosphere in the tank should be as big as or bigger than the pipeline supplying the gas. That is usually achieved by having the cargo tank lid or tank washing hatch open. But when vapour control and emission regulations require a closed operation (with the existing tank atmosphere forced to exhaust to shore), the incoming flow of nitrogen must be restricted to a rate equal to or less than the maximum flow of vapour possible through the venting system. If the capacity of the vapour return system is exceeded by the flow of nitrogen into a closed cargo tank, then the only other outlet is through the relief valve, which will prevent overpressurisation (though contravening the vapour control regulations). However, if the capacity of both outlets is exceeded, then overpressure will occur and damage to the tank structure may follow. The pressure and the flow rate of the incoming nitrogen must therefore be controlled. Use of a small hose or a reducer prior to the manifold will restrict the flow rate, but pressure must be controlled by the shore. A gauge will allow the ship to monitor the pressure. It is not appropriate to attempt throttling a gas flow by using the ship's manifold valve that is designed to control liquid flow. However, the manifold valve can and should be used as a rapid safety stop in an emergency: pressure surge in a gas is not as violent as in a liquid. When shore supplied nitrogen is to be used for drying or purging an empty tank that has been cleaned and gas
freed, the volume of nitrogen required should be calculated and agreed (tank volume multiplied by number of atmosphere changes needed to reach the desired level of dryness or oxygen exclusion), together with the flow rate, during the pre-transfer planning conference. Table 5.1 shows the volume of nitrogen that can be received in one minute through a known size of pipe at a known pressure. (The second figure in brackets indicates the associated hourly rate, which should be mentally compared to a liquid loading rate. Note that these tables are intended to be indicative only and any discrepancies are due to rounding of figures.) 200mm (8")
5.2 bar (75 psi)
3.4 bar (50 psi) 2.1 bar (30 psi) 0.7 bar (10 psi) Table 5 1 hour)
1 Cubic metres of through hoses of
Gas at various sizes.
gauge pressures received in 1 minute (and
Table 5.2 illustrates the time taken to receive gas into a tank at different pressures and hose sizes. The example used assumes a cargo tank of 1,250 cubic metres requiring four atmosphere changes, i.e. 5,000 cubic metres of nitrogen, to flow through. 200mm 5.2 bar 3.4 bar 2.1 bar 0.7 bar
3min. 4 min. 5 1/2 min. 11 min.
Table 5.2 Time to receive hose sizes.
5 ½ min. 7 ½ min. 11 min. 24 min.
15 min. 21 min. 29 min. 63 min.
½ hrs. ½ hrs. 2 ½ hrs. 5 ½ hrs.
7 hrs l0 ½ hrs.
Metres of gas with
When a cargo is required to be carried under a pad of nitrogen, and it is necessary to use nitrogen supplied from shore, it is better to purge the entire tank before loading. After such purging is completed, loading the cargo in a closed condition will create the needed pad within the tank. The risk of overpressurisation can be substantially reduced by avoiding padding with shore supplied nitrogen as a separate procedure on completion of loading. However, if padding with shore nitrogen has to be performed after loading, planning and good communication are essential. The supply should be through a small diameter connection to restrict the flow, and the rate must not exceed the vent capacity of the cargo tank. The operation should be stopped when a slight overpressure exists in the ullage space, but which is less than the tank pressure relief valve setting. The vapour space in a loaded tank is usually small, so overpressurisation can occur very suddenly, especially if cargo is forced into the vent lines which then become restricted or blocked and add to the rapid increase in tank pressure. 5.7.3 Preparations/or receiving nitrogen from shore When preparing to receive nitrogen from shore special emphasis should be placed on the following points:
• Ship and shore should agree in writing on the gas supply, specifying the volume required, the flow rate in standard cubic metres per minute, and the maxima in each case. • Care should be taken to ensure that the valves on the loading line between the shore manifold and the ship's tank are operated in the correct sequence, so that the ship is in control of the nitrogen flow. The ship should station a crew member at the loading manifold valve during the operation, even where remotely operated valves can be closed more quickly by a person in the cargo control room who is monitoring tank pressures. The crew member at the manifold is in the best position to react promptly to any other external indication of trouble. • Care should be taken to ensure that a tank to be dried or inerted has open vents with a greater flow rate capacity than the inlet, such that the tank cannot be overpressurised. This is usually achieved by having the cargo tank lid or a tank washing hatch open. • If local requirements for vapour control demand a closed venting of the tank through a vapour return line to shore, the nitrogen flow rate and pressure should not exceed the capacity of the venting system. Positive measures to ensure this should be agreed. • The tank pressure should be closely monitored during the operation. As with all inert gases, there is a potential health hazard, and it is necessary to ensure that crew members are not unnecessarily exposed to vapour being vented from a tank while it is inerted or purged with nitrogen. Special care is necessary when nitrogen as a gas is supplied to a ship directly from evaporating liquid nitrogen, sometimes delivered by a road tanker fitted with a vaporiser, because the volume and flow rate can be difficult to control and the agreed delivery figures may be unexpectedly and suddenly exceeded. The vaporisation ratio of nitrogen from its liquid form to its gaseous form is approximately 1:640. When any of this expansion is happening in the delivery pipeline the flow rate becomes uncontrolled, and it is the rapid expansion in volume that causes high pressures to be reached extremely quickly. In general, nitrogen should not be delivered to the ship this way, and the ship should request that it is provided from gas held in a buffer tank. If a ship suspects that traces of liquid nitrogen are arriving at the manifold valve (possibly indicated by ice forming on the ship's lines and valves), or that other agreed procedures are not being followed, the operation should be suspended until the apparent problems have been satisfactorily resolved. 5.8 CARGO LOADING 5.8.1 General. . General precautions when preparing for cargo operations are described earlier in this chapter, including the need for a liaison meeting with the terminal staff to agree an operational plan for the order of cargo handling. . Commencement of loading should be slow and, before the full loading rate is used, both ship and shore must be satisfied that the lines are correctly set and that there is no leak in the system. At the start of loading, and at regular intervals throughout the process, a check should be made that cargo is not leaking anywhere. During routine ullaging and testing the responsible officer should ensure that the procedure is conducted according to local and international regulations, and that correct precautions for personal protection are observed. 5.8.2 Use of compressed gas Compressed gas is sometimes used by a terminal to press products out of shore tanks (such as railway wagons) into the ship, and there is an inherent risk of overpressurisation of the ship's cargo tank. The gas pressure used for these operations varies, but can range between 2.5 and 5 bar. The point of greatest concern is when the supply into the ship's tank changes from liquid to compressed gas, causing an abrupt and dramatic increase in the tank filling rate from liquid at a few hundred cubic metres per hour to gas at several thousand cubic metres per hour. It will be seen from Table 5.1 on page 50 that a significant volume of gas will be received in a few seconds through the large liquid filling line.
Overpressurisation of a closed tank can occur in seconds, especially when the distance from the manifold to the tank is small or the vapour space in the tank is limited. A crew member stationed at the manifold will be best placed to detect and react to any indication that the flow in the system has changed from liquid to gas. 5.8.3 Topping off Care must be taken as tanks become full, especially when loading a product into more than one tank simultaneously, due to the increased risk of an overflow while topping off. High level alarms and tank overflow control alarms are safety critical items, and loading should be stopped if it is suspected that either is not working correctly. The responsible officer must ensure that tanks that have been topped off are properly isolated from tanks still being loaded. Cargo tanks which have been topped off should be checked frequently during the remaining loading operations to detect changes in liquid level, and to avoid an overflow. When nearing completion of loading the shore should be notified and, if necessary, the loading rate reduced. 5.8.4 Clearing shore pipelines When, after completion of a product, the shore pipelines are to be cleared by the use of air or inert gas (blow through) or by use of a line scraper (pigging), the responsible officer must ensure that there is sufficient space in the tank or tanks to accommodate the quantity of product in the shore pipeline, otherwise cargo overflow from a tank may occur. Blowing through or pigging could cause an increase in pressure, and the responsible officer must monitor the operation carefully in order to avoid tank Overpressurisation. The risk of large volumes of nitrogen or air, that has been under pressure in the shore line, escaping into the cargo tank must be taken into account (see Section 5.7). The same possibility exists for an abrupt and dramatic increase in the tank filling rate as is described in Section 5.8.2 when pressing a chemical out of shore tanks. During a line clearing operation it is important that terminal staff react promptly when the scraper is caught in its trap, in order to avoid all the compressed propelling gas entering a loaded cargo tank. 5.8.5 Clearing cargo hoses When clearing the line after loading a static accumulator cargo, it is desirable to minimise the introduction of gas into the tank which will bubble up through the cargo (see Appendix D.3.5). If nitrogen is used to clear the cargo hose after loading a cargo treated with an inhibitor that depends on oxygen, care should be taken to minimise the volume of nitrogen entering the cargo tank. Not only may bubbling the nitrogen through the liquid in the tank deplete the dissolved oxygen and affect the inhibitor by requiring it to take oxygen from the atmosphere in the ullage space, but it is also possible that excessive nitrogen will linger in the ullage space. 5.8.6 Completion of loading' When loading of a product is completed, the relevant manifold valve on the ship and the shore should be closed. This will provide separation of the ship and the shore system from a failure or unexpected action in the other. Samples should be taken in a safe manner using proper equipment suitable for the cargo involved and the pressures anticipated. Storage of samples on board should be strictly controlled; the IBC Code should be referred to for guidance. Care should be given to labelling and recording of samples, and their period of retention. After completion of loading, cargo hoses and arms should be cleared as agreed, and should only be disconnected from the manifold after they have been drained of cargo residues and relieved of any pressure (see Section 5.9).
5.9 DISCONNECTION OF CARGO HOSES After the transfer of a chemical cargo is complete, established procedures should be followed to minimise residues in the line, and especially in the cargo hose or cargo arm between ship and shore. Disconnection must only take place after draining of cargo residues and relief of any pressure, even before emergency disconnection if at all possible. Disconnection of the hose or cargo arm at the ship's manifold is a time when the cargo containment system is deliberately breached. Although hose disconnection is a routine operation that must be performed, it should be regarded as comparable to opening up any other cargo pipeline on deck. Personnel engaged in hose disconnection should wear protective equipment appropriate to the hazards of the cargo involved which, for a highly toxic cargo, will include a full chemical resistant suit and breathing apparatus. 5.10 CARGO CARE DURING THE VOYAGE Cargoes carried by a chemical tanker differ widely in characteristics and mode of handling, and thus in the care they require during transit. During the voyage, attention must be paid to these special needs of cargoes. Inert gas capacity should be sufficient for the entire voyage. If stored nitrogen is relied upon, it must be confirmed prior to sailing that the ship has sufficient nitrogen on board to be able to comply with the inerting requirements. Regular checks on tank contents should be made to detect an unexpected change in liquid level. Cargoes that need cooling or heating must be monitored daily and a temperature log kept. Some cargoes are liable to selfreact under certain conditions (see Section 1.4 and Appendix C). Cargoes that may self-react should be monitored daily in order to detect any abnormal behaviour at an early stage. Unexpected changes of temperature are an important early indicator of a possible self-reaction, and attention should be given to ensuring that any required heating does not cause part of the cargo to become overheated. Crystallisation of inhibited liquid cargoes can lead to depletion of inhibitor in parts of the tank's contents (because the inhibitor does not crystallise as well), and subsequent remelting of the crystals can thus yield pockets of uninhibited liquid, with the risk of starting dangerous self-polymerisation. With inhibited cargoes, the precautions and limitations described in the inhibitor certificate should be carefully observed. If control of the tank atmosphere is being used, ullage spaces should be monitored regularly to ensure that the correct atmosphere and overpressure are being maintained. Most inhibitors are not themselves volatile, so they do not vaporise with the cargo and are unlikely to be present in cargo vapours. Therefore, polymerisation may occur where cargo vapours condense. Such places as inside vent valves and flame arresters should be regularly inspected, and any blockage by solid polymers promptly cleared. 5.11 CARGO UNLOADING 5.11.1 General The general precautions when preparing for cargo operations, described earlier in this chapter, should be observed prior to and during discharge, and should include a liaison meeting with the responsible terminal staff to agree an operational plan for the order of cargo handling. Particular attention should be paid to ship's cargo discharge equipment, such as pumps and pumproom ventilation (see Section 5,3.2). Just prior to commencing discharge the responsible officer should check that the cargo pipeline system is set correctly, that correct valves are open, that valves not being used are closed, and that the cargo venting system is appropriate for the cargo operation. When a vapour balance is to be used by returning inert gas displaced from the shore receiving tank to the ship, the pressure in the ship's cargo tank must be carefully monitored, and necessary action taken
to avoid excessive over or underpressure. At the start of any unloading, and at regular intervals throughout the operation, checks should be made to ensure that cargo is not leaking. 5.11.2 Adding nitrogen to maintain overpressure When unloading cargoes that have to be carried under a blanket of nitrogen, it may be necessary to ensure that no air is drawn into the tank. Therefore an overpressure of nitrogen should be maintained as the liquid level falls. The nitrogen can be supplied from stored compressed gas or from a nitrogen generator on board, and be introduced into the tank ullage space. But if it is necessary to obtain nitrogen from the shore, it is essential that the pre-transfer discussion includes agreement on the nitrogen flow rate and pressure to be used. Although the overpressure required is no more than about 0.2 bar, it is usual for the shore nitrogen supply system to be well above this figure, perhaps as high as 7 bar. Particularly in the early stages when the ullage space is still small, it is possible for the flow rate to exceed the tank venting capacity, and for an overpressure to develop. A safe procedure is to use a pressure reducing device on the nitrogen supply line, and to have a calibrated gauge showing the pressure in the pipeline. There should be direct communication with the terminal, and the ship should monitor cargo tank ullage space pressure throughout. 5.11.3 Sweeping of cargo residues After the carriage of animal and vegetable oils and fats, manual sweeping of the cargo tanks is usually necessary to push the semi-liquid residues towards the pump suction to complete the discharge, and before commencing tank cleaning. (The process is sometimes called 'squeegeeing' or 'puddling'.) Despite the natural origins of the cargo, it is essential that safety precautions are observed on every occasion that personnel are sent into an enclosed space. Potential dangers with gases generated by these cargoes, not always during putrefaction, are indicated in Section 1.6. The tank should be mechanically ventilated for at least 1 hour, concurrently with discharge, to ensure its atmosphere is safe for entry without breathing apparatus before sweeping begins. The requirements for tank entry in Section 3.3 and atmosphere testing in Section 3.4 should be observed, and an enclosed space entry permit issued before personnel enter the tank. Ventilation should continue during the sweeping operation. A responsible person should remain in attendance at the tank entry hatch throughout the sweeping operation, keeping the personnel within under observation. . If at any time the oxygen level falls below 21%, the tank must be vacated until the oxygen level has been restored by ventilation. 5.11.4 Completion of discharge It is essential to reduce the cargo residue in a tank to the minimum attainable. Tanks should be stripped according to the requirements of the ship's P&A Manual. When discharge of a product is completed, the relevant manifold valve on the ship and the shore should be closed. This will provide separation of the ship and the shore system from a failure or unexpected action in the other. All openings on cargo tanks used for that product must be finally closed and secured. After completion of discharge, lines and hoses should be cleared to shore. Cargo hoses or arms must only be disconnected from the manifold after they have been drained of cargo residues, and relieved of any pressure. The importance that should be paid to safe disconnection is described in Section 5.9.
5.12 BALLASTING AND DEBALLASTING Many modem chemical tankers meet the segregated ballast requirements of MARPOL, and only infrequently use cargo tanks for ballast. Segregated ballast tank lids must be clearly marked as such. Sometimes, however, it may be necessary to load ballast water into cargo tanks, and before doing so the responsible officer should determine whether the tank is clean or contains cargo residues that might react in a hazardous manner with the ballast water. Ballasting a cargo tank that has not been cleaned may cause flammable, toxic or corrosive vapours to be expelled onto or around the cargo deck area. A cargo tank containing dirty ballast should be marked as such. It should never be allowed to overflow, and discharging of ballast from a cargo tank must only take place in accordance with the MARPOL Convention and local requirements. At the start of deballasting, especially from cargo tanks, and at regular intervals throughout the operation, checks should be made to ensure that cargo residue is not entering the sea. When emptying ballast tanks, cargo vapours may be drawn into the tank through openings. Ballast tank lids should therefore be kept closed when both cargo and ballast are being handled. Upon completion of ballasting or deballasting all tank openings used should be closed and secured. 5.13 TANK CLEANING AND GAS FREEING These operations are fully described in Chapter 7, together with the associated safety precautions. 5.14 SHIP TO SHIP TRANSFER 5.14.1 General The ship to ship (STS) transfer of cargoes carried on chemical tankers is a frequent operation, and the following section addresses some special safety aspects of the preparations and procedures that may be found necessary for STS operations. The guidance covers cargo transfer operations in open waters and roadsteads, either between two chemical carriers, or between a chemical carrier and barges. It is not intended to cover discharge to a barge from a chemical carrier already at a terminal, because that is considered to be normal cargo handling under the supervision and control of the port or terminal authorities. Navigational and ship handling aspects of an STS operation between chemical carriers will be very similar to those of an STS operation between oil tankers, as described in the ICS/OCIMF publication Ship to Ship Transfer Guide (Petroleum), which should be consulted (referred to as the STS Guide in the following sections). The guide also provides advice about special equipment necessary, and preparation of contingency plans for dealing with emergencies. In general, observance of the procedures followed when handling cargo alongside a terminal will ensure safe ship to ship transfers. However, an important additional task is careful pre-planning of the operation, noting instances where shore provision of materials or labour for handling equipment is normal terminal practice, and identifying on board or external sources of material or personnel to perform those duties during the ship to ship operation. 5.14.2 Responsibility In general, it is the responsibility of the ships' operators and agents to obtain any permission necessary for a ship to ship transfer operation, especially if the transfer area is within the jurisdiction of a port
authority. Check List 1 in the STS Guide should be used at the planning stage to ensure compatibility of ships and their cargo handling equipment. The general principles of a transfer, the area in which the transfer will take place, and the compatibility of the ships should follow the advice in the STS Guide, with safety always the primary consideration. Ship operators or the local agent should advise a master about documentation requirements, especially customs documentation, well in advance of the transfer. It is normal for the quantity transferred to be agreed between masters of both ships in accordance with operator's instructions. When preparing for a ship to ship transfer the two masters involved should agree at the earliest opportunity on every aspect of the transfer procedure, and agree which person will be in overall advisory control of the operation (this may be one of them or an experienced STS superintendent). At all times, however, each master will remain fully responsible for the safety of his own ship, its crew and its cargo, and must not permit safety to be jeopardised. 5.14.3 Communications The STS Guide gives advice on establishing communications at the earliest opportunity, and provides an example of an initial voyage instruction. Satisfactory communication between the two ships involved is an essential requirement for a successful ship to ship transfer operation. Neither approach and mooring, nor unmooring, should be attempted until satisfactory communications are established, and if during cargo operations there is a breakdown of communications on either ship, all operations should be suspended until they are satisfactorily restored. 5.14.4 Navigational warnings The person with overall advisory control should arrange for broadcast of a navigational warning about the transfer, as described in the STS Guide, and should arrange for its cancellation on completion of the operation. 5.14.5 Weather conditions and limitations It is impracticable to lay down the limits of weather conditions under which STS transfer operations can safely be carried out. All available weather forecasts for the area should be obtained before the operation begins. Thus any decision to proceed will be taken in the light of best available knowledge. 5.14.6 Pre-transfer preparations on each ship Preparations on each ship in readiness for the operation, the approach of the ships to each other, berthing and mooring of the ships and safety procedures when alongside, are all well described in the STS Guide. When preparing cargo loading and discharging plans, due regard should be given toensuring that adequate stability is maintained, hull stresses remain within sea-going limits, and that free surface effects are kept to a minimum throughout. Remember that normal shore resources will not be available and that prior assessment will help to avoid incorrect decisions that could compound an emergency and increase the peril for one or both ships. The cargo operation should be planned and agreed between the two ships, and should include information on the following, where applicable: • Quantity of each grade of cargo to be transferred, and the sequence of grades. • Cargo data from data sheets, and copies of the data sheets if available. • Details of cargo transfer system to be used, number of pumps and maximum pressure.
• Initial, maximum and topping off pumping rates. The discharging ship should be informed by the receiving ship of the flow rates required for each of the different phases of the cargo operation. • Notice of rate change, and transfer shutdown procedures. If variations in transfer rate subsequently become necessary due to circumstances on one ship, the other should be advised accordingly. • Emergency and spill containment procedures. • Watch or shift arrangements. • Critical stages of the operation. • Local and government rules that apply to the transfer. 5.14.7 Cargo transfer operations When the two ships are securely moored, and before cargo transfer commences, the pre-transfer checks should be satisfactorily completed (see Check List 4 in the STS Guide). In addition, attention should be given to completion, as far as practicable, of the appropriate Ship/Shore Safety Checklist (see Appendix L). Hose strings should be of sufficient length to avoid over-stressing and chafing throughout the cargo transfer. To establish the correct hose length, changes in relative freeboard and ship movement must be taken into account. Only hoses in good condition and suitable for the cargo to be transferred should be used. The agreed transfer rate should not exceed the manufacturer's recommended How rates for the cargo hoses. Vapour return and vapour balance between ships during an STS operation can be problematic. Its main advantage will be to limit the need for vapour release to atmosphere, and crew exposure to the vapour. But attention must be given to provision of a flame arresting arrangement. For some cargoes specified in the IMO Codes, vapour return is mandatory, and STS operations will be dependent on provision of correct vapour return equipment. Throughout cargo operations, the discharging ship and the receiving ship should each station a responsible person at the cargo manifold area to observe the hoses and to check for leaks. In addition, throughout the cargo transfer, the discharging ship should station a responsible person equipped with a portable radio at or near the cargo pump controls to take action as required. Regular transfer rate checks and comparisons should be made between the two ships, and the results logged. Any differences or anomalies revealed should be carefully checked, and if necessary cargo operations should be suspended until the differences are resolved. During cargo transfer, appropriate ballast operations should be performed on both ships in order to minimise extreme differences in freeboard, and to avoid excessive trim by the stern. Listing of either ship should be avoided, except as required for cargo tank draining on the discharging ship. Regardless of the type of ship, any ballast which is discharged overboard should be clean. All other ballast should be retained on board or transferred to the discharging ship. 5.14.8 Completion of cargo transfer After completion of cargo transfer, all hoses should be drained into the receiving ship prior to disconnecting. Disconnecting of cargo hoses should receive careful attention, as it is a procedure not usually undertaken by ship's personnel. The guidance in Section 5.9 should be noted. Cargo manifolds and cargo hoses should be securely blanked. Relevant authorities, if any, should be informed of completion of cargo transfer and the anticipated time of unmooring. Any navigational warning issued should be cancelled.
ENVIRONMENTAL CONTROL OF VAPOUR SPACE IN CARGO TANKS 6.1 Introduction 6.2 Control Methods .1 General .2 Drying .3 Inerting or purging .4 Padding .5 Ventilation 6.3 Sources of Inert Gases 6.4 Methods of Replacing Tank Atmospheres 6.5 Application to Cargo Tank Operations .1 Maintenance of an inert atmosphere .2 Inerting or purging of empty tanks .3 Loading into inerted tanks .4 Loaded passage .5 Discharge of cargo or ballast from inerted tanks .6 Tank washing .7 Gas freeing an inerted tank 6.6 Precautions to Avoid Health Hazards .1 General .2 Inert gas on the cargo deck .3 Entry into cargo tanks .4 Scrubber and condensate water 6.7 Effect of Inert Gas on Inhibited Chemicals 6.8 Control of Tank Atmospheres for Cargo Quality
ENVIRONMENTAL CONTROL OF VAPOUR SPACE IN CARGO TANKS This chapter describes ways of maintaining a non-flammable or non-reactive tank atmosphere through the use of inert gas or another medium. It covers, in general terms, the operation of the systems for achieving this. It also describes the precautions to be taken to avoid hazards to health. For guidance on the operation of the particular system fitted on a ship, reference should be made to the ship's operations manual, the equipment manufacturer's instructions and installation drawings. The IMO Guidelines for Inert Gas Systems should be consulted for a more detailed explanation of the principles behind the design and operating practices of typical fixed inert gas systems. For a detailed description of inert gas systems and their use, refer to Appendix E. 6.1 INTRODUCTION The requirements and practices of inerting cargo tanks on chemical tankers are different from those on oil tankers, except for those chemical tankers which have large cargo tanks or large capacity tank washing machines. The usual reasons for cargo tanks to be purged or for cargoes to be carried under inert conditions on chemical tankers are to avoid reactivity or achieve cargo quality control. The vapour (ullage) spaces within cargo tanks, and in some cases the void spaces surrounding the cargo tanks, may require specially controlled atmospheres. Chemical tankers with individual cargo tanks of 3,000m3 or bigger, or which have large capacity tank washing machines (i.e. with a nozzle throughput of more than 17.5m3 per hour, machine throughput greater than 60m3 per hour, or total water flow per cargo tank greater than 110m3 per hour) are required to use their inert gas systems when carrying low flashpoint chemicals in these cargo tanks. For smaller tanks containing chemicals, the summary of minimum requirements in the IBC Code states what environmental control is necessary, if any, for safety reasons. Additionally, chemical tankers of 30,000 dwt and over carrying oil cargoes will be required to inert all cargo tanks containing petroleum products with a flash point of 60°C and less. When a chemical tanker is required to transport oil cargoes, the recommendations in ISGOTT about inert gas should be followed. The provision and use of an inert gas system is specified by the SOLAS Convention. To meet the SOLAS requirements for non-flammability, an inert gas system must be capable of delivering inert gas with an oxygen content of not more than 5% by volume in the inert gas main at any required rate of flow. The system must also be able to maintain a positive pressure in the cargo tanks at all times, such that the tank atmosphere has an oxygen content of not more than 8% by volume. For cargoes which the IBC Code requires to be carried in an inerted condition, it is recommended that the maximum oxygen content limit of 8% in the tank atmosphere should be observed unless a lower figure is specified. 6.2 CONTROL METHODS 6.2.1 General For some cargoes, the IBC Code requires vapour spaces within cargo tanks to have specially controlled atmospheres, principally if the reaction between cargo and air would cause a hazardous situation, or if the cargo has a low auto-ignition temperature, or has a wide flammability range. Inerting may also be needed for cargo quality control purposes (see Section 6.8).
There are four recognised methods of environmental control for cargo tanks on chemical tankers - drying, inerting or purging, padding and ventilation. In general, inert gas is used to achieve the first three of these. When inerting or padding is required, care should be taken to ensure that there is an adequate supply of the inerting or padding agents on board, in order that the required conditions can be maintained in the cargo tank vapour space throughout the intended voyage. It is most important that the ship's fixed oxygen analyser system is regularly tested and maintained in good working order. 6.2.2 Drying Whenever a water-reactive cargo has to be carried, the cargo tank atmosphere must have all moisture and water vapour removed before loading to prevent an unsafe reaction with the cargo. To achieve this, the cargo tank is dried, generally with nitrogen or with specially dried air, and then the tank and associated piping and equipment are filled with moisture-free gas or vapour that has a dewpoint of -40°C or less. The dry conditions should be established prior to loading, and maintained during loading, transport by sea and discharge. 6.2.3 Inerting or purging The terms inerting or purging generally refer to the replacement of air in a cargo tank by an inert gas (usually nitrogen), and the maintenance of that condition to prevent the formation of flammable mixtures of cargo vapour and air, or to prevent chemical reaction between oxygen and the cargo. Inerting or purging may also be necessary to reduce the humidity (dewpoint) of the atmosphere within the cargo system or to protect the quality of the cargo. (In chemical tankers, as with oil tankers, the terms inerting and purging are almost synonymous, and must not be confused with the entirely different use of the terms in liquefied gas tanker operations.) The extent of inerting will normally be specified by the cargo shippers, sometimes in cargo data sheets. 6.2.4 Padding Where a cargo reacts with oxygen it needs to be isolated from air. Padding is a means of achieving this, as required by the IBC Code, by using a suitable dry gas or a layer of liquid with which the cargo will not mix. When a dry gas is to be used, the cargo tank and associated piping systems should be filled with the vapour, and the process should be completed before loading starts unless an alternative method is specified. When a liquid (usually water) is to be used it should be loaded into the cargo tank first, to the required depth, and the cargo should then be loaded through cargo piping that terminates near the bottom of the tank. The initial loading rate should be slow enough to enable a stable horizontal interface to be developed between the padding liquid and the cargo. Once this has been achieved the loading rate can be increased. Padding is also used to maintain the quality of the cargo by protecting it from air, and this process (often called blanketing) is usually performed after the cargo has been loaded, using nitrogen at low pressure and low flow rate. A safe practice is to introduce the nitrogen directly into the cargo tank ullage space or into the ship's cargo line, preferably using the ship's equipment and gas supply. However, a shipper may specify that nitrogen of a known purity be used, supplied by the shore usually at a higher pressure, in which case the empty tank should be purged prior to loading to create a pad after loading is complete. Monitoring of the ullage space should be carried out at regular intervals to ensure that the correct atmosphere is being maintained.
6.2.5 Ventilation A few products require ventilation while on board, to keep the cargo vapour concentration in the ullage space at or below half of its lower explosive limit throughout the period of carriage. The ventilation can be either forced or natural.
6.3 SOURCES OF INERT GASES Nitrogen is the primary medium for inerting and padding of cargo tanks on chemical tankers. Nitrogen supplied by the ship itself can either be produced on board as needed, e.g. from pressure swing adsorption or membrane separation generators, or can come from liquid nitrogen or compressed nitrogen stored on board. If the nitrogen supply system is located in a Class A machinery space, a device to prevent backflow will be installed, but on a chemical tanker the nitrogen supply must be dry so a water seal cannot, be used, and a dry seal will be employed. It is essential that the integrity of the seal is maintained. If the nitrogen supply system is within the cargo area, a primary seal is not required. The design and installation of an on board nitrogen generator will have taken into account that the generator's exhaust stream may be oxygen rich. No alterations should be made without careful consideration. Exhaust dueling and pipework should be made from material that is resistant to oxidation corrosion, and any corrosion holes should be repaired promptly. It has also become common to inert cargo tanks, pumps and pipeline systems with nitrogen supplied from shore, and loading nitrogen from shore for this purpose is now a frequent operation (see Section 5.7 for guidance on safe operational procedures). The loading process is an important stage in cargo handling. Alternatively, when oil cargoes are carried, inert gas may be generated on board by oil fired inert gas generating plant or from boiler flue gas, in which the oxygen is largely replaced by carbon dioxide. Inert gas generation systems are described in Appendix E, including details of the typical composition of each inert gas supplied. 6.4 METHODS OF REPLACING TANK ATMOSPHERES In theory, if the entire existing atmosphere in a tank could be replaced by an equal volume of inert gas the resulting tank atmosphere would have the same oxygen level as the incoming inert gas. In practice, however, a good deal of mixing takes place during the exchange, so that a volume of inert gas equal to several tank volumes must be introduced into the tank before the desired result can be achieved. One of two distinct processes, dilution or displacement, will be used. Dilution takes place when the incoming inert gas mixes with the original tank atmosphere to form a homogeneous mixture throughout the tank so that, as the process continues, the concentration of the original gas decreases progressively. It is important that the incoming inert gas has sufficient entry velocity to penetrate to the bottom of the tank, and a limit must therefore be placed on the number of tanks which can be inerted simultaneously. Displacement depends on the fact that inert gas is slightly lighter or slightly heavier than the existing gases in a tank, so that when the inert gas enters the tank the existing gases are displaced. When using this method it is important that the inert gas has a very low entry velocity to enable a stable horizontal interface to be developed between the incoming and escaping gases, although in practice some dilution inevitably takes place owing to the turbulence caused by the inert gas flow. The method generally allows several tanks to be inerted or purged simultaneously.
Whichever method is employed, it is vital that sufficient oxygen or gas measurements are taken to check the efficiency of the operations. A mixture of inert gas and flammable gas when vented and mixed with air can become flammable. The normal safety precautions taken when venting flammable gas should therefore be followed. Crew members should be aware of potential hazards to health from inert gases or oxygen depleted atmosphere in the vicinity of tank vents and outlets. 6.5 APPLICATION TO CARGO TANK OPERATIONS 6.5.1 Maintenance of an inert atmosphere When carrying a cargo that requires the atmosphere to be inert, that atmosphere should be maintained in an inert condition at all times, prior to and during loading of cargo, on passage by sea, during discharge of cargo and until the tank is gas freed. The tank atmosphere should be maintained at a positive pressure of at least 0.07 bar, taking care to prevent any rise in pressure which could result in the lifting of the tank pressure relief valve. It must be emphasised that the protection provided by an inert gas system depends on the proper operation and maintenance of the entire system. It is particularly important to ensure that non-return barriers function correctly so that there is no possibility of cargo vapour or liquid passing out of the cargo area. 6.5.2 Inerting or purging of empty tanks When the cargo requires an inert atmosphere, inert gas should be introduced into the empty tank through the distribution system while venting the air in the tank to atmosphere. This operation should continue until the oxygen content is at or below the value required for the cargo. When inerting with nitrogen from ashore, the pressure within the tank should be carefully monitored. Overpressurisation of a tank is a real danger. Prior discussion with the terminal representative is essential to agree a flow rate for the nitrogen. The capacity of the tank's normal venting system may not be adequate to accommodate the maximum flow rate, so that additional venting capacity will need to be used. A description of the operational aspects is given in Section 5.7. 6.5.3 Loading into inerted tanks When filling an inerted tank, the inert gas that is displaced should be vented through the appropriate venting system. On completion of cargo loading, the tank should be shut down and the atmosphere overpressure maintained as required. 6.5.4 Loaded passage A positive pressure of inert gas should be maintained in the ullage space of an inerted cargo tank at all times in order to prevent the possible ingress of air. If the pressure falls below the set level of the low pressure alarm, positive action should be taken to re-pressurise the tank. Pressure loss is normally associated with falling air and sea temperatures or leakage from tank openings. In the first case, where air may enter the tank, it is all the more important to maintain the inert gas overpressure. Leakages of escaping gas from tank openings are often detected by their noise. During the search for a leak, personnel should be aware that cargo vapour may be included in the escaping gas. Particular attention must be given to the seal of tank hatches, ullage lids, tank cleaning machine openings, P/V valves etc. Leaks which cannot be readily eliminated should be marked and recorded for attention at the next suitable opportunity.
6.5.5 Discharge of cargo or ballast from inerted tanks When carrying a cargo that requires the atmosphere to be inerted, it may be necessary to maintain the inert gas supply throughout cargo or ballast discharge operations to prevent air entering the tanks. Throughout the unloading, therefore, the oxygen content and pressure of the inert gas supply must be carefully monitored. Where a vapour balance is used to return the nitrogen displaced from the shore receiving tank to the ship, the pressure in the ship's cargo tank must be carefully monitored and necessary action taken to avoid underpressure or excessive overpressure. If the supply of inert gas fails during unloading, the positive pressure in the tanks will rapidly be lost. Unloading should be stopped immediately to prevent ingress of air, and should not be resumed until the inert gas supply is restored. 6.5.6 Tank washing If an inert atmosphere is to be maintained during tank washing, the advice in Section 7.3.3 should be observed. 6.5.7 Gas freeing an inerted tank Before starting to gas free an inerted cargo tank, it should be isolated from other tanks. When either portable fans or fixed fans connected to the cargo pipeline system are used to introduce air into the tank, the inert gas inlet should be isolated. When the inert gas system fan is employed to supply fresh or dry air, care is necessary to ensure isolation of both the line back to the inert gas source and the inert gas inlet into other tanks which are being kept inert. 6.6 PRECAUTIONS TO AVOID HEALTH HAZARDS 6.6.1 General All the types of inert gas considered for use on board chemical tankers are by definition asphyxiant, in that they ensure a deficiency of oxygen and therefore will not support human life. Nitrogen is not itself toxic or dangerous to human life, since four-fifths of the air normally breathed consists of nitrogen. It therefore presents a particular hazard since it has no smell and in an atmosphere inerted or padded with nitrogen there is no feeling of distress or warning symptoms of asphyxiation. Someone who enters an atmosphere containing only nitrogen can lose consciousness in as little as 20 seconds. Death usually follows rapidly, either by asphyxia or from injuries sustained when falling. Liquid nitrogen is stored at about -196°C so it also presents a low temperature hazard. Skin contact with liquid nitrogen can result in frostbite. Advice on dealing with frostbite is given in the IMO Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG). 6.6.2 Inert gas on the cargo deck In still weather conditions, vented vapours and inert gas can linger on deck, especially in the vicinity of vents and openings such as cargo measuring ports. The possibility of low oxygen levels should constantly be anticipated by those working in the cargo area, and care taken not to stand in the path of vented gas. 6.6.3 Entry into cargo tanks For general advice on entry into enclosed spaces see Chapter 3. Entry into cargo tanks should be permitted only after the tanks have been gas freed.
During any work, the safety precautions set out in Section 3.7 should be observed, and consideration given to the carriage of a personal oxygen deficiency alarm. If the tank cannot be freed of inert gas to the levels specified in Chapter 3, entry should be permitted only in exceptional circumstances and when there is no practicable alternative. In such cases personnel must wear breathing apparatus and the appropriate protective clothing, and the tank entry made under fully controlled conditions. 6.6.4 Scrubber and condensate water When inert gas is generated from flue gases, the scrubber effluent water is acidic to the touch. Another hazard is condensate water which tends to collect in the inert gas distribution pipes, particularly in the deck main. It is often more acidic than the scrubber effluent and is highly corrosive. It is best to avoid unnecessary skin contact with either scrubber effluent or condensate water.
6.7 EFFECT OF INERT GAS ON INHIBITED CHEMICALS Inhibited cargoes often need the presence of some oxygen in the tank atmosphere in order to permit the inhibitor to work properly. The minimum level of oxygen is usually stated on the inhibitor certificate but as a general rule, a cargo containing an inhibitor that needs oxygen should not be carried in an inerted tank. If nitrogen is bubbled through an inhibited cargo (such as when compressed nitrogen is used to clear the cargo hose after loading) the nitrogen will deplete the oxygen dissolved in the liquid, thereby requiring the inhibitor to take oxygen from the atmosphere. It is possible that excessive nitrogen used for blowing through might linger in the ullage space. 6.8 CONTROL OF TANK ATMOSPHERES FOR CARGO QUALITY As stated in Section 6.2, in addition to atmosphere control for safety reasons, further inerting measures may be taken to meet requirements for cargo quality control, usually specified by the shipper. The quality of the cargo is usually expressed by requiring a specified condition of arrival at the customer's premises. The specification is normally based on the customer's own requirements, but national specifications are sometimes used. Specifications for the same product can vary widely between customers due to different processing and end uses. Great care should be taken to avoid allowing trace constituents of the inert gas, and especially of inert flue gas produced on board, to cause degradation of a particular cargo. For a description of possible problems, see Appendix E.
TANK CLEANING AND GAS FREEING 7.1 Introduction .1 General . 2 Procedures and Arrangements Manual (P&A Manual) 7.2 Supervision and Preparation .1 Responsibility .2 Pre-cleaning conference .3 Preparations 7.3 Cargo Tank Washing and Cleaning .1 General .2 Tank washing atmospheres .3 Precautions when tank washing in an inert atmosphere .4 Precautions when tank washing in an undefined atmosphere .5 Precautions for sounding tanks when not using a sounding pipe .6 Steaming of cargo tanks .7 Cleaning of cofferdams or double bottom tanks .8 Free fall of wash water in slop tanks 7.4 Special Cleaning Methods 7.5 Arrangements for Disposal of Tank Washings, Slops and Dirty Ballast .1 General .2 Mandatory pre-wash water .3 Dirty ballast .4 Safety precautions during discharge of cargo slops into the sea .5 Management of slop tanks 7.6 Tank Cleaning Equipment .1 General .2 Fixed tank washing machines .3 Portable tank washing machines and hoses 7.7 Gas Freeing .1 Safe procedures for gas freeing after tank cleaning .2 Removal of sludge, scale and sediment .3 Opening up of cargo lines and handling equipment 7.8 Gas Detection Equipment
TANK CLEANING AND GAS FREEING
This chapter deals with the procedures for cleaning and gas freeing cargo tanks and other enclosed spaces after the discharge of a volatile product or of a non-volatile product that has been carried in a non-gas free tank, or when there is a possibility that flammable or toxic gas has entered a tank or space. Safety precautions to be taken are set out, and the implications of MARPOL Annexes I and II are taken into account. The ship's Procedures and Arrangements Manual explains the practical implementation of the MARPOL regulations under different conditions, including ventilation as an alternative to washing. It is expected that owners and operators of chemical tankers will provide guidance on their own established procedures. This chapter does not deal with the degree of cleanliness that may be required from tank cleaning, as that is considered to be a commercial matter related to the quality of subsequent cargoes. The potential for damage to cargo tank coatings by some washing procedures is also regarded as a commercial concern rather than a safety matter, although operators will need to be aware of coating limitations when planning cleaning operations. 7.1 INTRODUCTION 7.1.1 General Tank cleaning is essential on a chemical tanker, but it must be recognised as a potentially hazardous operation, and rigorous precautions should be observed throughout the process. Together with gas freeing, it is probably the most hazardous operation routinely undertaken on a chemical tanker. The additional risk created by cargo gases expelled from the tanks cannot be overemphasised. Depending on the most recent cargo carried in tanks that are to be cleaned, vapours that are toxic, flammable and corrosive should be expected to be released onto and around the cargo deck area. It is therefore of utmost importance that every possible care is exercised during all operations connected with tank cleaning and gas freeing, and that the operations are carried out using the approved procedures and arrangements for the ship. Personnel involved should be fully aware of the dangers and take necessary precautions, because the consequences of an inadvertent error can be very serious and far reaching. 7.1.2 Procedures and Arrangements Manual (P&A Manual) All ships certified to carry noxious liquid substances in bulk must be provided with a Procedures and Arrangements (P&A) Manual, approved by the flag administration, which addresses the marine environmental aspects of removal and disposal of residues from cargo tanks, and describes how to perform those operations. The Manual should be adhered to in all respects, including the performance of mandatory pre-wash requirements in accordance with MARPOL 73/78 Annex II.
7.2 SUPERVISION AND PREPARATION 7.2.1 Responsibility A responsible officer should supervise all tank cleaning and gas freeing operations. All stages of the operation should be performed in a safe manner appropriate to each individual chemical's physical characteristics, such as toxicity, corrosiveness and reactivity. 7.2.2 Pre-cleaning conference A pre-cleaning conference under the leadership of the responsible officer should be held prior to any tank cleaning or gas freeing operation. Other crew members involved should be identified by the responsible officer, and their role explained. The conference should take the opportunity to clarify that all personnel involved fully understand their duties during the forthcoming tank cleaning operation. The conference should confirm: • The tanks to be cleaned, and the cleaning sequence. • The type of cargo to be cleaned from each tank, and its characteristics. Cargo information sheets should be available so that personnel involved are familiar with the hazards. • The major risks during cleaning, such as toxicity, flammability, corrosiveness and reactivity. • The safety equipment and personal protective equipment to be available and ready for use throughout the operation and during connecting and disconnecting of hoses at the cargo manifold. • The cleaning instructions to be followed in each case. • The means of disposal of any cargo residues and the contaminated cleaning water. The relevant slop tank must be specified in each case.
• The precautions necessary to confirm that the cargo deck area is free from cargo vapours during tank washing and gas freeing operations. • That at regular intervals throughout the operation, checks will be made to ensure that tank washings containing cargo are not inadvertently being discharged into the sea. A written tank cleaning schedule should be drawn up and made available for reference by all personnel participating in the operations. An example of a suitable format will be found on page 71. 7.2.3 Preparations Before any tank cleaning or gas freeing operations begin, the responsible officer should confirm that all necessary equipment is available, and that adequate checks are made to establish that all equipment to be used is in good working condition. Both before and during tank cleaning and gas freeing operations, the responsible officer should be satisfied that the appropriate precautions set out in this chapter are being observed. All personnel on board should be notified that tank cleaning or gas freeing is about to begin, and only those personnel involved in the operations should be allowed into the cargo tank area. If other craft are alongside the tanker, their personnel should be notified that tank cleaning operations are about to commence, and their compliance with all appropriate safety measures should be confirmed. When gas freeing or tank cleaning while alongside at a terminal, the precautions for cargo handling in Chapter 5 should be observed where appropriate. Before starting, the permission of the port authority and terminal operator should be obtained, and the
Tank Cleaning Schedule/Checklist Tank No.
Slop tank No.
Prior to any tank cleaning operation, the following facts should be closely checked by the chief officer or a responsible person, to confirm that:
The tanks to be cleaned are empty
The tank cleaning hoses are correctly rigged and connected
The discharge hoses are correctly rigged and connected
The assigned slop tank is available and has sufficient capacity
Responsible person (Rank/Name)
To be kept on file for [6 months].
appropriate personnel ashore should be consulted to confirm that conditions on the jetty do not present a hazard, and to obtain agreement that operations can start. The following checks should be made before operations commence: • That essential protective clothing and respiratory protection equipment (as recommended in Chapter 9) are being worn if so required. • That fresh water shower and eyewash arrangements are ready for immediate use in the event of contamination of personnel. • That work not related to cargo operations, and not otherwise essential, is avoided in the cargo area during tank cleaning operations. • That cargo pipelines serving set of cargo tanks are isolated from the tanks to be cleaned or gas freed, unless all tanks in that set are to be cleaned. • That tanks served by a common vent system are properly isolated. • That cargo tank lids, tank washing openings, ullage openings and sighting ports in uncleaned tanks are kept closed until they are to be cleaned. • That all sea and overboard discharge valves connected to the cargo and ballast systems are shut and secured when not in use. • That pumproom precautions (see Section 5.3.2) are being observed and will continue to be observed throughout tank cleaning and gas freeing operations. • That fire fighting equipment is ready for immediate use. 7.3 CARGO TANK WASHING AND CLEANING 7.3.1 General Water is the most common washing medium for flushing the bottoms of cargo tanks, or for cleaning them using tank washing machines. It is readily available in large quantities, it is an efficient cleanser and on most chemical tankers the wash water can be heated when necessary. Nevertheless, it is sometimes necessary to use small quantities of chemical additives or detergents as a cleaning agent in order to improve the cleaning effect. However, in some situations water will not be used. Water must not be used in the case of chemicals that react with water, and a washing medium other than water may also be used for commercial reasons. It may be permissible to use ventilation to remove cargo residues and gas free a cargo tank after a highly volatile cargo has been carried. In every case, the full safety aspects of the operation should be considered. When tank cleaning in port, relevant regulations and limitations established by the port authority and terminal should be complied with. After carrying a low flash point cargo, a flammable vapour mixture should always be suspected until tests have established that the atmosphere is non-flammable. Equal care is necessary after carrying a non-volatile flammable cargo at a temperature above its flash point, or after discharge of any cargo or ballast that had been loaded into a tank that was not free of flammable vapour. Toxic vapour in harmful concentrations should also be assumed after unloading cargo which have a vapour inhalation hazard. Cargo vapour, toxic or flammable, should be suspected in cofferdams or any other space within the cargo area into which such cargoes may have leaked. 7.3.2 Tank washing atmospheres Tank washing may be carried out in one of the following atmospheres: • Inert - An atmosphere made incapable of burning by the introduction of inert gas, and thereby reducing the overall oxygen content. For the purposes of this guide, the oxygen content of an inert tank atmosphere should not exceed 8% by volume. • Non-inert - An atmosphere which is undefined.
7.3.3 Precautions when tank washing in an inert atmosphere Although the atmosphere in a properly inerted tank is incapable of burning, the following precautions should be observed: • When portable washing machines are used, all hose connections should be made up before the washing machine is introduced into the tank. Connections should not be broken until after the machine has been removed from the tank. However, to allow draining of a hose, a coupling may be partially opened and then re-tightened before the machine is removed. • The tank should be kept drained during washing. Washing should be stopped to clear any build-up of wash water. When there is a need to maintain an inert atmosphere during tank washing, the following points should be observed: • The purity and pressure of the inert gas being delivered during the washing process should be monitored. • Before each tank is washed, the oxygen level in the tank should be determined both at a point about 1 metre below the deck and at the middle level of the ullage space. At neither location should the oxygen level exceed 8% by volume. • If during washing the oxygen level in the inert gas supply exceeds 8% by volume or the pressure of the atmosphere in the tank is no longer positive, washing should be stopped until satisfactory conditions are restored. Some cargoes carried under an inert blanket are not flammable but the atmosphere is inerted for cargo quality reasons. In this case, gradual decay of the inert atmosphere during cleaning is acceptable. In all other cases, if the inert atmosphere is not maintained then the procedures used and precautions taken should be as for an undefined atmosphere. 7.3.4 Precautions when tank washing in an undefined atmosphere Most tank cleaning on chemical tankers is conducted in an undefined atmosphere. In all cases after carrying a flammable cargo, the atmosphere in an empty tank should be treated as flammable. The only way to guarantee that an explosion cannot occur during washing in an undefined atmosphere is to make certain that there can be no source of ignition. Good tanker practice will avoid all normal sources but, in addition, the following precautions should be taken if the risk from static electricity is to be eliminated: • Before washing, the tank bottom should be flushed with water and stripped. The piping system, including cargo pumps, crossovers and discharge lines, should also be flushed with water. The flushing water should be drained to the tank designated to receive slops. This operation may not be necessary if the ship is fitted with an efficient stripping system, and the cargo tank and pipelines have been stripped as detailed in the ship's Procedures and Arrangements Manual. If cargoes are highly water reactive this operation must not be carried out.
• When portable washing machines are used, all hose connections should be made up before the washing machine is introduced into the tank. Connections should not be broken until after the machine has been removed from the tank. However, to allow draining of a hose, a coupling may be partially opened and then re-tightened before the machine is removed. • Ropes made of synthetic fibres should not be used to support the tank cleaning machines. • No machine may have a throughput greater than 60m3 per hour, and no nozzle may have a throughput greater than 17.5m3 per hour. • The total water throughput per cargo tank should be kept as low as practicable and must in no case exceed 110m3 per hour. • The tank should be kept drained during washing. Washing should be stopped to clear any build-up of wash water. • Recirculated wash water should not be used, because it may increase the generation of static electricity. • Sounding rods and other equipment must be introduced through a sounding pipe
reaching close to the bottom of the tank and earthed to it. If a sounding pipe is not used then the additional precautions in paragraph 7.3.5 below should be followed. • No other material that may create a spark or static electricity should be lowered into the tank. • Steam should not be injected into the tank. Further information on electrostatic precautions during tank washing is given in Appendix D. 7.3.5 Precautions for sounding tanks when not using a sounding pipe If a sounding pipe is not used, it is essential that any metallic components of the sounding rod or other equipment are bonded and securely earthed until removal from the tank. This precaution should be observed during washing and for five hours afterwards, unless the tank is continuously mechanically ventilated after washing, in which case the delay period can be reduced to one hour. During the delay period: • An interface detector of metallic construction may be used if earthed to the ship by means of a clamp or bolted metal lug. • A metal rod may be used on the end of a metal tape which is earthed to the ship. • A metal sounding rod suspended on a natural fibre rope should not be used even if the end at deck level is fastened to the ship, because the rope cannot be completely relied upon to act as an earthing path. • Equipment made entirely of non-metallic materials may in general be used: e.g. a wooden sounding rod or float may be suspended on a rope without earthing. • Neither ropes made of synthetic polymers nor chains should be used for lowering equipment into cargo tanks. 7.3.6 Steaming of cargo tanks Because of the hazard from static electricity, steam should not be introduced into cargo tanks where there is a risk of the presence of a flammable atmosphere. It should be borne in mind that a non-flammable atmosphere cannot be guaranteed in all cases where steaming might be thought to be useful. 7.3.7 Cleaning of cofferdams or double bottom tanks If it is necessary to clean cofferdams or double bottom tanks into which cargo liquids or vapour could have leaked, the same precautions should be observed as when cleaning cargo tanks. 7.3.8 Free fall of wash water in slop tanks It is essential to avoid the free fall of slops or tank washing water in a receiving slop tank unless the tank is inerted (see Appendix D for the generation and control of static electricity). Washing water or slops should be transferred to the receiving tank through the cargo system. If a different arrangement is necessary, then to avoid splashing the receiving tank should be filled to a depth of at least 1 metre, or sufficient to ensure that the discharge inlet is well below the surface of the water. 7.4 SPECIAL CLEANING METHODS Water washing may be inadequate or inappropriate after the carriage of certain products, because tanks can only be adequately cleaned by special cleaning methods or cleaning agents. Where it is decided to use a special cleaning method, and well documented experience indicates that it is safe to do so, thorough company guidance should be provided that describes the procedures for the ship to follow. Where a special cleaning method is to be used in port, local authorities may impose additional safety or environmental requirements. Some cargoes may react with certain cleaning agents and produce large amounts of toxic or
flammable vapours, or render equipment such as pumps inoperable. The choice of a tank cleaning agent should be made with full knowledge of the cargo characteristics. If a special method involving cleaning agents is to be used, it may create an additional hazard for the crew. Shipboard procedures should ensure that personnel are familiar with, and protected from, the health hazards associated with such a method. The cleaning agents may be added to the wash water or used alone. The cleaning procedures adopted should not entail the need for personnel to enter the tank. If, however, the only practical means of cleaning involves personnel entering the tank then the precautions set out in Sections 3.3 and 3.6 should be strictly followed. No one should enter any cargo tank unless express permission to do so has been received from the responsible officer, and all appropriate precautions taken. The tank atmosphere should be safe for entry and an entry permit issued. Chemical absorption detectors should be used for detecting the presence of specific gases and vapours at TLV levels. In exceptional circumstances the requirement might arise for wiping down product residues from the tank walls by using a chemical solvent in a localised area. The amount used should be small, and the personnel involved should be aware that its use may modify the atmosphere. The introduction of the solvent into the tank might also generate additional risks such as toxicity or flammability. Such risks should be carefully evaluated before starting the operation, which should not be undertaken unless the personnel involved can be effectively protected from those risks. Data sheets for the chemical solvent used should be available on board. In addition, manufacturer's instructions or recommendations for the use of commercial products should be observed, and the resulting slops disposed of in accordance with the ship's P&A Manual. 7.5 ARRANGEMENTS FOR DISPOSAL OF TANK WASHINGS/ SLOPS AND DIRTY BALLAST 7.5.1 General During normal operations of a chemical carrier, the main need to dispose of chemical residues, slops or water contaminated with cargo will arise during or immediately after tank cleaning. Final disposal of slops or wash water should be in accordance with the ship's P&A Manual. Tank washings and slops may be retained on board in a slop tank, or discharged ashore or into barges. 7.5.2 Mandatory pre-wash water Mandatory pre-wash procedures should be conducted strictly in accordance with the ship's P&A Manual, and the resulting contaminated wash water should always be discharged to shore. The intention of MARPOL is that this should happen immediately following the cargo discharge operations, and in the same port. However, occasions do arise when adequate shore reception facilities for the washings are not provided, and the ship must retain the washings on board until arrival at another port. MARPOL addresses this matter, and the P&A Manual will provide guidance on the correct procedures for a particular ship. During such a voyage, the slops and tank washings should be given the same safety and environmental care as the original cargo. 7.5.3 Dirty ballast Dirty ballast, caused by ballasting into a cargo tank before the tank is cleaned, should be treated as slops, and must be disposed of in accordance with MARPOL and the ship's P&A Manual. 7.5.4 Safety precautions during discharge of cargo slops into the sea When discharge overboard is permitted, it should only be undertaken when the ship is at sea and proceeding en route at a speed of at least 7 knots. Discharges of chemical residues should
normally be below the waterline through an underwater discharge outlet on the side of the ship away from essential water inlet valves. In the interests of safety, this procedure should be adopted even when it is not a mandatory requirement. When any discharges are made above the waterline, care should be taken to avoid cargo vapour or liquid blowing back on board. If such a risk exists, discharge should be made below the waterline: if this is not possible, consideration should be given to altering the ship's course or speed to reduce the risk, and personnel on deck should wear appropriate protective clothing. 7.5.5 Management of slop tanks Compatibility of various cargo and cleaning chemicals should be considered just as carefully when handling slops as when handling the cargoes themselves. Particular care is needed when washing several tanks which have contained dissimilar cargoes, and compatibility should be taken into account when selecting the destination tank for stripped wash water. The following should be avoided: • Mixing of slops from Annex I (oil) cargoes with slops from Annex II- (chemical) cargoes. • Mixing of slops from incompatible cargoes. • Mixing of slops from vegetable oils or fats with chemical slops or petroleum oil slops. If the ship's cargo tanks are used as slop tanks, care should be taken to avoid introducing slops from cargoes which are incompatible with the tank coating. In this regard, some cargoes which are themselves compatible may, when mixed with water, form acids and thus damage a coating, e.g. slops from hydrolytic cargoes in a zinc coated tank. 7.6 TANK CLEANING EQUIPMENT 7.6.1 General Before any operations begin, the responsible officer should confirm that adequate checks are made to establish that all equipment to be used during tank cleaning operations is in good working order. 7.6.2 Fixed tank washing machines The installation of fixed tank washing machines within a cargo tank allows an inert atmosphere to be maintained during the washing operation, and thus permits cleaning in a closed mode in compliance with port regulations prohibiting release of noxious vapours. Their installation and use also reduces crew exposure to cargo vapours and inert gas. The design of fixed tank washing machines will have met all statutory requirements for safety as regards materials of construction, water flow rates and generation of static electricity. Any routine servicing should be performed in accordance with the manufacturer's instructions, but no on board modifications should be contemplated. 7.6.3 Portable tank washing machines and hoses The outer casing of portable machines should be of a material which will not generate an incendive spark on contact with the internal structure of a cargo tank. Hoses should be indelibly marked to allow identification. Bonding wires should be incorporated within all water hoses. Couplings should be secured to the hose in such a way that effective electrical bonding is assured from end to end of the hose. Hoses should be tested for electrical continuity in a dry condition prior to use and in no case should the resistance exceed 6 ohms per metre length. Such testing should not involve high voltages. A record should be kept showing the date and result of electrical continuity testing. The hose coupling arrangement should be such that effective bonding can be established between the tank washing machine, the hoses and the fixed tank cleaning water supply line. Washing machines should be electrically bonded to the water hose by means of a suitable connection or external bonding wire.
When suspended within a cargo tank, machines should be supported by means of a natural fibre rope and not left to hang from the water hose. Further information on electrostatic precautions during tank washing is provided in Appendix D. 7.7 GAS FREEING 7.7.1 Safe procedures for gas freeing after tank cleaning The following recommendations apply to cargo tank gas freeing in general. The IBC Code contains advice about cargo tank gas freeing for newer ships, but operators of older chemical tankers which are not subject to the IBC Code are urged to take account of this advice. It is essential to know what type of vapours can be expected: they may be flammable and/or toxic and/or corrosive: 1. Venting of toxic and flammable gas during gas freeing should be through the vessel's approved gas freeing outlets, and therefore the exit velocity should be sufficient to carry the vapours clear of the deck. No escape of cargo vapours should occur at deck level before the concentration within the tank has fallen below 30% LFL and the relevant TLV. Thereafter, final clearance of the vapour mixture may continue at tank deck level through other larger deck openings. 2. If portable ventilation equipment is to be used to blow air into a tank, tank openings should be kept closed until work on that tank is about to commence. 3. Where cargo tanks are gas freed by means of permanently installed fans, air is introduced into the cargo tank through the cargo lines. The entire line system should be thoroughly drained before venting to avoid any obstruction of the air flow or tendency for water or cargo residues to be blown into a cargo tank. Valves on the systems, other than those required for ventilation, should be closed and secured. The fans should normally be blanked or disconnected from the cargo tank system when not in use. 4. Fixed gas freeing equipment should not be used for gas freeing of a tank while simultaneously being used to ventilate another tank in which washing is in progress, regardless of the capacity of the equipment. 5. Portable fans should only be used if they are water driven, or hydraulically or pneumatically driven. Their construction materials should be, such that no hazard of incendiary sparking arises if, for any reason, the impeller touches the inside of the casing. The manufacturer's recommendations for maintenance should be followed. Guards should be in place to prevent accidental contact with fan blades. 6. Portable fans, where used, should be placed in such positions and the ventilation openings so arranged that all parts of the tank being ventilated are effectively and equally gas freed. Fans should generally be as remote as possible from the ventilation outlets. 7. Portable fans should be so connected to the deck that an effective electrical bond exists between the fan and the deck. 8. The wind direction may cause cargo vapours to pass near to air intakes for accommodation spaces or engine room ventilation, and necessitate additional precautions (see Sections 2.9 and 2.10). Central air conditioning or mechanical ventilation system intakes should be adjusted to prevent the entry of gas, if possible by using recirculation of air within the spaces. 9. If at any time it is suspected that gas is being drawn into the accommodation block, the central air conditioning and any mechanical ventilating systems should be stopped and the intakes covered or closed. It is unlikely that any ship now uses window-type air conditioning units which draw in air from outside the superstructure, but any which are still in use, or other plants which are not certified as safe for use in the presence of flammable gas, should be electrically disconnected and any external vents or intakes closed.
10. If the tanks are connected by a common venting system, each tank should be isolated to prevent the transfer of gas to or from other tanks. 11. When a tank appears to have been gas freed and all mechanical ventilation has been stopped, a period of about ten minutes should elapse before taking final gas measurements. This allows relatively stable conditions to develop within the tank space. Tests should then be made at several levels and, where the tank is sub-divided by a wash bulkhead, in each compartment of the tank. In large compartments such tests should be made at widely separate positions. If satisfactory gas readings are not obtained, the tank should be checked for cargo residues and then ventilation resumed. 12. On completion of all gas freeing and tank washing, the gas venting system should be carefully checked, particular attention being paid to the efficient working of the P/V valves and any high velocity vent valves. If the valves or vent risers are fitted with devices designed to prevent the passage of flame, these should also be checked, and cleaned if found necessary. Gas vent risers and their drains should be checked to ensure that they are free of any blockage. 13. On completion of gas freeing, attention should be given to all equipment that has been used, and to enclosed or partially enclosed spaces that can retain or contain cargo residues or vapours, so that no unsuspected dangerous pockets can remain. Places where such cargo traces may exist include cargo lines, cargo valves, cargo pumps, stripping lines and valves, venting lines and P/V valves, vapour return lines, ullaging or sounding arrangements, heating coils, cargo handling equipment store rooms, protective clothing store rooms and cargo sample store rooms. Additional considerations to take into account when the tank is inerted are set out in Section 6.5.7. 7.7.2 Removal of sludge, scale and sediment Scale and sediment build-up in a tank may adversely affect stripping of cargo and gas freeing, while gradual evaporation of entrapped cargo may cause subsequent regassing of the tank. Removal of such sludge should only be considered after gas freeing is complete, and the tank has been certified as safe to enter and the tank lid marked accordingly. Scale and sediment removed from the tanks should be disposed of as soon as possible. Equipment to be used for sludge removal should be made from materials which do not give rise to a risk of ignition. The responsible person and those entering a tank to perform such work should be aware of the potential for releasing traces of vapours when material is disturbed, and proper contingency plans should exist to ensure the safety of personnel. Chemical absorption detectors should be used for detecting the presence of specific vapours at TLV levels. 7.7.3 Opening up of cargo lines and handling equipment Cargo pipelines, manifold crossovers, vent lines etc. should be cleared of cargo residues, and should be cleaned and gas freed at the same time as the cleaning and gas freeing of the cargo tank. It should always be assumed that small residues of cargo may be released when opening up any section of a cargo pump, cargo pipeline, vent line or heating coil. Precautions should be taken accordingly. Recleaning and further gas freeing may be required. If it becomes necessary to open up cargo lines and handling equipment on deck or in a cargo tank or a cargo pumproom, the following precautions should be taken: • The task should be assessed and approved by a responsible officer, and a work permit issued before starting any work. • After gas freeing the space, the equipment and associated pipeline should be isolated as far as possible, and further ventilated. • After ventilation is considered to be complete, the atmosphere should be tested to confirm that its flammability as a percentage of LFL, and its toxicity relative to TLV, are within safe limits. • When opening up, air measurements for flammable and toxic vapours should be made in the vicinity of the working area. • Fire fighting equipment should be ready for immediate use.
7.8 GAS DETECTION EQUIPMENT In order to maintain a proper control of the tank atmosphere and to check the effectiveness of gas freeing, especially prior to tank entry, several different gas measuring instruments need to be available for use. Which one to use will depend upon the type of atmosphere being measured. Tank atmosphere sampling lines should be in all respects suitable for and impervious to the gases present, and should be resistant to the effects of hot wash water. Instruments themselves should be used in accordance with the manufacturers' instructions. A detailed description of instrument types is given in Appendix J. In addition to any fixed gas detectors, at least two of each of the following portable instruments should be held on the ship: • A flammable gas indicator capable of measuring gas to the lower flammable limit (LFL) and with the scale graduated as a percentage of this limit. A flammable gas indicator usually cannot read flammable gas concentrations in an inert atmosphere but, depending on the trade of a particular ship, it may be found appropriate to carry gas indicators capable of measuring percentage volume of flammable gas in an inerted atmosphere (thermal conductivity meters). • A toxic gas indicator capable of measuring concentrations in the human toxicity range and calibrated in parts per million. (The presence of some specified toxic vapours at very low concentrations can only be established by laboratory tests.) • An oxygen analyser capable of measuring percentage volume of oxygen in an atmosphere. During tank cleaning, consideration should be given to the possible effect of water on the efficiency of the gas measuring equipment.
EMERGENCY PROCEDURES 8.1 Introduction 8.2 Emergency Organisation 8.3 Emergencies .1 Chemical fires .2 Chemical cargo spills .3 Deck valve and deck pipeline leakage .4 Tank leakage within the ship 8.4 Emergency Discharge or Jettison of Cargo 8.5 Notification of Spillage into the Sea 8.6 Personnel Exposure 8.7 Action by Ships When an Emergency Occurs at Other Berths Nearby 8.8 Emergency Removal of a Tanker from a Berth
EMERGENCY PROCEDURES This chapter deals with the preparation of plans to meet any emergencies affecting chemical cargoes or cargo handling, as well as the immediate action to be taken in such an emergency. Particular attention is paid to the procedures needed in the event of a fire or an uncontrolled toxic liquid release, because these are potentially the most extreme types of emergency likely to be encountered. However, much of the guidance is applicable in other circumstances, including the control of pollution, and the chapter should be read with this in mind. Rescue from enclosed spaces is covered in Chapter 3, while additional information on fire fighting will be found in Appendix H. 8.1 INTRODUCTION This chapter gives general guidance on procedures for the most readily foreseeable emergencies in which chemicals are involved. It is impossible to predict the nature of every potential emergency that may occur on a chemical tanker. Standard emergency procedures should therefore be developed and kept available for immediate implementation, so that basic action can be taken quickly and decisions on how to tackle any additional problems can be made in an orderly manner. The ship's emergency contingency plan should align with a broader plan held by the company management- The procedures developed should anticipate and cover the types of emergency which might be encountered in the particular activities and trade of the tanker or at terminals regularly visited. The person who discovers an emergency situation should raise the alarm to alert the emergency organisation. Those on the scene should attempt immediate measures to control the incident until the emergency organisation takes effect. 8.2 EMERGENCY ORGANISATION Personnel on a chemical tanker must be prepared to tackle cargo-related emergencies, such as chemical fires, chemical reactions, toxic vapour release, leaks and spills, both at sea and in port. Personnel that will be directly involved in such emergencies must be familiar with emergency procedures and contingency plans. Drills and exercises should vary, so that the crew members become familiar with equipment throughout the ship, and the master and other officers can consider what they would do in the event of various types of emergency. In each emergency, the first stages of the contingency plan should be: • Raising the alarm. • Locating and assessing the emergency and the dangers involved, and identifying actions already taken. • Organizing manpower and equipment. • Arranging contingency evacuation for non-essential personnel. • Notifying proper authorities. • Notifying the ship operator's office in accordance with the company's contingency plan. The contingency plan, which should include emergency evacuation procedures, has to be as effective in port as at sea and therefore all procedures and arrangements have to be developed with this in mind. The master should take advantage of any opportunity for a combined emergency exercise with shore personnel at a terminal.
8.3 EMERGENCIES 8.3.1 Chemical fires Fire fighting cannot be successful unless all equipment is operational, and all personnel are trained in its use. Fires involving chemicals pose specific hazards which are addressed in Appendix H. There is no such thing as a minor fire involving chemical cargoes. The ship's general alarm should be raised and, if alongside, the terminal must be notified with regards to the chemicals involved. The terminal control room should be requested to summon any outside assistance such as the civil fire brigade, rescue launches, medical aid and ambulances, police, harbor authority and pilots. Any cargo handling, ballasting, tank cleaning or bunkering operations should be stopped immediately and all valves closed. Any craft alongside should be released. Decks, bulkheads and other structures in the vicinity of the fire, and adjacent tanks, which contain flammable cargoes or are not gas free, should be cooled with water. If at sea, the tanker should be maneuvered so as to restrict the spread of the fire and allow it to be attacked from a windward direction. It is anticipated that each ship or company will have its own fire emergency plan. The following list of points should be considered for inclusion: • Activate the alarm. • Stop cargo operations - close valves and hatches. • Organize fire fighting teams. • If alongside a berth, alert terminal staff and request them to alert port authorities. • If at anchor in port, alert the port authorities. • If other ships or craft are alongside, alert them and instruct them to depart immediately. • Identify the chemical or chemicals involved, and any chemicals that may be at risk if the fire spreads. • Select the fire fighting equipment and fire extinguishing agent to be used. • Be alert to the fact that toxic fumes may enter the accommodation, and an evacuation of non-essential crew may be necessary. 8.3.2 Chemical cargo spills The biggest risk of a cargo spill is during cargo handling operations, either because of equipment failure or improper handling procedures. Cargo spills are therefore most likely to happen in port. In the event of a spill, the following actions should be taken immediately: • Activate the alarm. • Stop all cargo operations and close valves and hatches. • If alongside a berth, notify the terminal staff of the chemicals involved and possible risk posed to personnel. • Notify local port authorities, usually through the terminal staff. • Prohibit smoking and use of naked lights throughout the ship. • Clear all non-essential personnel from the area. • Close all accommodation access doors, and stop all non-closed circuit ventilation. • Arrange for main engines and steering gear to be brought to stand-by. The primary factor affecting response will of course be the chemical or chemicals involved, but the action to be taken depends on the circumstances of the spillage, as well as its size and location. If there is a possibility of cargo or cargo vapour entering any accommodation or engine room air intake, appropriate preventive steps must be taken quickly. As a general rule, there should be a full initial response to any spill, the emergency party wearing the appropriate protective clothing and breathing apparatus. Safety of personnel and the ship should take priority over environmental care. If it is possible and safe to do so, the released liquid should be pumped or washed into a slop tank or other containment, or collected for safe disposal using absorbent material. However, if it is not safe or if there is any doubt, the spillage should be washed overboard with very large amounts of water. If at sea, the tanker should be maneuvered so as to disperse the vapour away from the ship's accommodation.
For small, localised and contained spills, it may not be necessary to implement all the action points in the ship's contingency plan. However, the master must always keep in mind the local circumstances, the nature of the chemical involved, and the potential harm to personnel, ship's structure and the environment. In most cases it is better to overreact than to delay action. The general advice for a corrosive cargo spillage on deck is to wash the spilled liquid overboard with large quantities of water from as far away as practicable. A fog nozzle should be used and not a direct jet of water. The emergency team should wear appropriate protection, approach the spill from upwind and direct the spray of water to the edge of the spill, gradually working towards the center. The use of water on a fuming acid and other strong acids will initially cause a vigorous reaction that will cause increased fuming. However, this will be temporary while the spillage will be dealt with rapidly. If at sea, the ship should be turned off wind. 8.3.3 Deck valve and deck pipeline leakage If leakage develops from a deck pipeline, deck valve, cargo hose or metal arm, operations through that connection should be stopped and the situation treated as an emergency until the cause has been identified and the defect remedied. Permanent means for the retention of any slight leakage at ship and shore connections should have been provided. Operations should not be restarted until the fault has been rectified and all hazards from the released cargo eliminated. If a pipeline, hose or arm bursts, or if there is an overflow, all cargo and bunker operations should be stopped immediately and the situation treated as a cargo spill. 8.3.4 Tank leakage within the ship Leakage from a cargo tank into void or ballast spaces may cause damage to materials or equipment, and may create an explosive atmosphere and a potential personnel risk. The actions to be taken may differ depending on the product involved and other circumstances such as the weather, but should as a minimum include the following: • Identify the products involved and the risks associated with them. • Clear the area of all non-essential personnel. • Identify the location of the leak. • Transfer the product in the leaking tank to an empty tank, if at all possible. • Consider notifying port and local authorities, and ship's operators. • Commence remedial measures. Spills in confined spaces such as pumprooms should, where practicable, be first contained and then treated and collected for safe disposal. Spills may be contained with dry sand, earth or proprietary chemicals. Acid residues can be neutralized with sodium carbonate (soda ash) or special chemicals. Untreated acid spillage must be prevented from entering mild steel areas of the ship as rapid corrosion can follow: in extreme cases the consequent hull corrosion has caused the ship to sink. Leakages from one cargo tank to another, or multiple leakages where there is a risk of mixing incompatible chemicals, should always be treated carefully. Where time allows, expert advice should be sought as to the possible risks involved. A non-cargo space that has had a chemical leaking into it should be treated as a cargo space, and the same precautions taken. It should be cleaned and gas freed before any attempt is made for repairs. Remedial measures should be decided upon after consultation with the operator. 8.4 EMERGENCY DISCHARGE OR JETTISON OF CARGO The jettison of cargo is an extreme measure, justified only in emergency as a means of saving life at sea or where the integrity of the ship is at risk. A decision to jettison cargo should not be taken until every alternative option has been considered in the light of available information on stability and reserve buoyancy.
If it is necessary to jettison cargo there will be a possibility of releasing large amounts of flammable or toxic vapours. The following precautions are recommended: • Engine room personnel should be alerted: depending on the circumstances prevailing at the time, consideration should be given to changing over engine room sea water intakes from high to low level. • Discharge should take place through a sea valve and where possible on the side opposite to the engine room intakes. • All non-essential inlets should be closed. • If discharge must be from the deck level, flexible hoses should be rigged to extend below the water surface. • All safety precautions relating to the presence of flammable or toxic gas in the vicinity of the deck must be observed. • A radio warning should be broadcast for the information of ships nearby. 8.5 NOTIFICATION OF SPILLAGE INTO THE SEA Any incident, accidental or deliberate and whether at sea or in port, that causes or will probably cause a release of oil into the sea should be reported to the proper authorities. Each ship will have its own Shipboard Oil Pollution Emergency Plan (SOPEP), which will give advice. From 2003, the same reporting requirements will apply to actual or probable releases of noxious liquid substances, and in the case of ships certified to carry such cargoes the SOPEP will become a Shipboard Marine Pollution Emergency Plan (SMPEP), covering spillage of noxious liquids. 8.6 PERSONNEL EXPOSURE Unplanned exposure of personnel to toxic or corrosive fumes or liquid should always be treated as an emergency. Sections A.3 and B.3 give an outline indication of appropriate care. In more serious cases, the rescue team should be mobilized and the rescue plan implemented. First aid should be administered as indicated in the product material data sheet. General advice is given in the Emergency Schedules (EmS) and the Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG). The master must evaluate the seriousness of the exposure and, if in doubt, seek medical attention and advice.
8.7 ACTION BY SHIPS WHEN AN EMERGENCY OCCURS AT OTHER BERTHS NEARBY On hearing the terminal alarm being sounded, or on being otherwise advised of an emergency at the terminal, a ship, which is not involved in the emergency, should be prepared for the situation to worsen. It may become necessary to shut down all cargo, bunkering and ballasting operations, withdraw personnel from the open deck, bring fire fighting capability to a state of readiness, and make engines, steering gear and unmooring equipment ready for immediate use. Contingency evacuation should be considered. 8.8 EMERGENCY REMOVAL OF A TANKER FROM A BERTH If an emergency that cannot be controlled occurs on a chemical tanker at a terminal, it may be necessary to consider removal from the berth. Planning for such an eventuality will require consultation between a representative of the port authority or harbor master, the responsible terminal official, the master of the tanker and the senior local authority fire officer. The plan should avoid hasty action, which might increase rather than reduce the danger to personnel, the tanker, the terminal, other ships berthed nearby and adjacent installations.
By the time it is necessary to remove a tanker, which is on fire, the circumstances may be such that the ship's crew is unable to assist. The decision whether to remove a tanker under controlled conditions or to retain it at the berth should, in the first instance, be based on the safety of life.
PERSONAL PROTECTIVE EQUIPMENT 9.1 Introduction 9.2 Respiratory Protection .1 General .2 Canister or filter type respirators .3 Self-contained compressed air breathing apparatus (SCABA) .4 Air line breathing apparatus .5 Emergency escape breathing apparatus .6 Maintenance .7 Training 9.3 Body Protection .1 General . 2 Types of chemical resistant clothing 9.4 Eye Protection 9.5 Hand Protection 9.6 Foot Protection
PERSONAL PROTECTIVE EQUIPMENT This chapter describes the main types of equipment available for protection of personnel from chemical cargoes, and the precautions that need to be followed, in their use. Brie/guidance on clothing that will provide protection from fires is given in Appendix H. 9.1 INTRODUCTION The importance of the proper use of protective clothing and equipment by personnel involved in the handling of hazardous chemicals cannot be overemphasised. But it should be remembered that protective clothing or equipment does not reduce the hazard: it provides a barrier against the hazard. The effectiveness of that barrier can be lost if the personal protective equipment is used incorrectly or is of the wrong type. Defective or ineffective protective clothing or equipment will not provide the necessary safeguards. It is therefore essential that all items of equipment are properly maintained at all times, and that the correct items are selected for use. The manufacturer's instructions should be kept with the relevant equipment, if possible, and referred to as necessary when maintenance is carried out, and before use. All personnel who may be required to use protective equipment should be properly trained in its use and advised of its limitations. The material of the suits, gloves, face shields, goggles, aprons and other items used should be suitable for the cargo. The IBC Code specifies certain personal protective equipment for individual cargoes. The protective clothing and equipment described here is in addition to the basic personal protection that is required on board for crew members and visitors, such as safety shoes, safety helmet, safety goggles etc. 9.2 RESPIRATORY PROTECTION 9.2.1 General Respiratory protection is of primary importance since inhalation is one of the major routes of exposure to toxic chemicals. Respiratory protection equipment (breathing apparatus) is designed to provide the user with an adequate supply of fresh air. It usually consists of a face piece connected to either an air source or an air purifying device (filter). The face mask must be checked and adjusted to ensure it is airtight. The presence of facial hair, such as large side whiskers or a beard, may adversely affect the mask's seal and, if it is impossible to achieve a satisfactory seal, then another person should be selected to wear the apparatus. 9.2.2 Canister or filter type respirators Canister or filter type respirators absorb toxic or poisonous elements but do not supply oxygen. Therefore such equipment should not be used in enclosed spaces where the oxygen content of the atmosphere may be insufficient to sustain life. In case of doubt, always use a self-contained compressed air breathing apparatus.
Canisters are available for absorption of a variety of different vapours, but the following precautions should be observed: • The correct type of canister should be fitted for the vapour concerned: it may be necessary to change canisters when changing cargoes. • Canisters should not be opened to the atmosphere until needed for use, because they may become gradually saturated and ineffective. • Canisters have a limited life once in use: they should be discarded and destroyed after use. • Canisters should not be used when the atmospheric concentration of the contaminants is known or suspected to be more than 0.1% (greater than 1,000 ppm). 9.2.3 Self-contained compressed air breathing apparatus (SCABA) Breathing apparatus should be used as necessary by personnel engaged in cargo operations involving toxic cargoes, by fire fighters, and when entering an unsafe space. Tanks or compartments which are not gas free, which are deficient in oxygen or which contain smoke should not be entered unless absolutely necessary. Breathing apparatus consists of a portable supply of compressed air contained in a cylinder or cylinders attached to a carrying frame and harness worn by the user. Air is provided to the user through a full face mask, which can be adjusted to give an airtight fit. Breathing apparatus should always be used in accordance with the manufacturer's instructions. Breathing apparatus should be stowed fully assembled in a place where it is readily accessible. Air bottles should be fully charged and the adjusting straps kept slack. Units should be located so as to be available for emergencies in different parts of the ship. 9.2.4 Air line breathing apparatus Air line breathing apparatus has been developed to enable compressed air equipment to be used for longer periods than would be possible using self-contained equipment alone. The apparatus consists of a face mask supplied with compressed air through a small diameter air hose. Air from a suitable source is filtered and its pressure reduced to the design pressure required to supply air to the face mask. An air line system may be fitted to cargo pumprooms. It is recommended that an additional and completely separate supply of clean air should be available under direct control of the user. The air line breathing apparatus should always be used in accordance with the manufacturer's instructions. 9.2.5 Emergency escape breathing apparatus Ships certified for the carriage of certain cargoes listed in the IMO Codes are required to be provided with respiratory and eye protection sufficient for every person on board for emergency escape purposes. Escape sets supply air for at least 15 minutes. The equipment is for emergency use only and should not be used for any other purpose. 9.2.6 Maintenance The IBC Code requires that breathing apparatus be inspected by a responsible officer at least once a month, and inspected and tested by an expert at least once a year. The expert may be one of the ship's officers who has received proper, recognised training in breathing apparatus maintenance. Defects must be corrected promptly. A record should be kept of inspections, tests and repairs. Air bottles should be refilled as soon as possible after use. Masks and helmets should be cleaned and disinfected after use. 9.2.7 Training Practical demonstrations and training in the use of all types of breathing apparatus should be carried out regularly to give personnel experience in its use. Familiarity gained through regular practice will lead to confidence in the equipment. Only trained personnel should use self-contained and air line breathing apparatus, since incorrect or inefficient use can endanger the user's life.
9.3.1 General Contact with any chemical substance or product should be avoided. All necessary care should be taken to prevent skin and eye contact. The skin needs protection against corrosive and dangerous chemicals. A garment with leakproof fastenings and manufactured from chemically resistant material constitutes the correct protection. Ideally, the clothing should combine the greatest degree of comfort with the maximum level of protection. Care and maintenance of the clothing is important. Contaminated clothing should always be washed or hosed down before the wearer takes it off. This ensures a longer service life for the coated fabric and prevents contamination the next time the clothing is worn. Used protective clothing should always be stored in a ventilated area outside the accommodation. A full protective suit should be used when entering areas contaminated with toxic products or areas where the cargo vapour is toxic, especially in conditions which cause perspiration and, therefore, the possibility of vapour penetrating the skin through the sweat. Boots and gloves should be permanently attached and either a full face breathing mask incorporated into the suit or the hood tailored for the fitting of a full face breathing mask. 9.3.2 Types of chemical resistant clothing The type and degree of protection required is dependent on the physical, chemical or toxic properties of the cargoes being handled, whether the job is continuous or intermittent, and the environmental conditions prevailing. The cargo data sheet should be consulted. For light duty, uncoated cotton is conventionally used in the form of overalls, coveralls, smocks etc., and is satisfactory for operators who are at only slight risk from chemicals and where there is the occasional danger of a splash from mild substances. Over time, personal working clothing might absorb small and otherwise harmless amounts of cargo vapours to the point where it becomes noticeable when worn into accommodation, particularly in public rooms or mess rooms. For medium duty, the apron provides protection. Aprons are made in a wide range of sizes, weights and thickness from natural rubber, synthetic materials such as nylon coated with polyvinyl chloride (PVC), and neoprene or polyurethane coated nylon. Heavyweight aprons produced from heavy base fabrics coated with PVC can be used for protection against most chemicals. PVC coated fabrics generally provide protection against a wide range of chemicals, including some of the most corrosive acids and alkaline substances. There are a few very strong organic solvents which can leach out the plasticisers from PVC, making it stiff and brittle. When handling organic solvents it is best to use protective clothing manufactured from polyuretfaane, chlorobutyl rubber or neoprene coated fabrics. The latter are also useful where resistance to mineral oils, vegetable oils and greases is required, although oil and fat resistance is built into some PVC coated fabrics. For heavy duty protection a wide range of chemical resistant clothing is available, including boiler suits, long surgical coats, bib and brace overalls, leggings and three-quarter length coats, all with machine stitched seams electronically welded to stop penetration, and generous over and under wraps. A wide range of protective head gear is also manufactured in the form of caps fitted with neck and shoulder covers. Visors are also fitted, with coated fabric attached for protection of the face and neck. PVC coated base fabrics woven from synthetic material such as nylon and terylene are used for contact with extremely hazardous and corrosive chemicals, because the base fabric substrates provide strength, tearresistance and improved impermeability. Neoprene coated and polyurethane coated materials are also available for protection against very strong solvents and some specific chemicals. The use of such heavy clothing is ideal for protection against possible continuous contact with hazardous chemicals, or even the possibility of deluge or spillage conditions. In the latter case, the correct clothing will provide the person concerned with
sufficient time to leave the affected area and either be hosed down or have the clothing removed before the PVC coating on the fabric is affected. 9.4 EYE PROTECTION Loss of eyesight is a devastating disability and results in total incapacitation for a long period. Eyes are particularly vulnerable to injury from corrosive and toxic liquids and vapours. It is therefore essential that they receive special consideration when assessing the need for personal protection. There is a wide range of eye protectors for chemical hazards. Care should be taken to evaluate the chemical hazard properly, guided by the cargo data sheet, and select the eye protector accordingly. There are three types of eye protectors to choose from: • Safety goggles give complete chemical and mechanical eye protection, and can generally be worn comfortably over most spectacles. • Face shields, usually combined with a safety helmet, provide eye and face protection from splashes of liquid and mechanical hazards, but not against vapour hazards. • Safety spectacles, with or without lateral protection (side shields), are available with different lens materials. Safety spectacles rarely fit properly over ordinary spectacles and therefore care should be taken to achieve an effective fitting. For protection against splashes of liquid and where there is doubt about the adequacy of protection provided, safety goggles or a face shield should be used.
9.5 HAND PROTECTION The number of hazards for which hand protection may be required can range from simple dust or vapour to protection against fuming nitric acid. Obviously the type of glove has to be selected carefully and it is important to understand the hazard or combination of hazards, which may be present. These could include corrosive chemicals, toxic chemicals that can be absorbed through the skin, and high temperature cargoes. Fortunately there is a wide choice of gloves which can adequately protect the hand against most hazards. PVC or rubber gloves are available in a range of thickness and weights, and the choice will depend on the cargoes being handled. Neoprene or nitrile rubber gloves have excellent resistance to solvents, petrol, oils and many chemicals. When choosing the correct gloves, as for body clothing, one should be guided by the cargo data sheet, the resistance of the gloves' fabrics or material to the chemicals, whether the working conditions are continuous or intermittent, and the environmental conditions. Generally, when only gloves are being worn, it is advisable for the gloves to have long cuffs which can reach over the sleeves of normal clothing. 9.6 FOOT PROTECTION Rubber or PVC boots need to be worn when there is a risk of coming into contact with corrosive or toxic chemicals. Boots that have reinforced toe-caps are preferable as they also give protection against solid objects.
TOXIC PRODUCTS A.1 General .1 Toxic substances .2 Toxic effects .3 Threshold limit value (TLV) .4 Precautionary principles .5 Toxic vapour detection and personal protective equipment A.2 IMO Code Requirements A.3 Medical First Aid .1 Basic documents .2 How to recognise poisoning .3 First aid and further care .4 Emergency treatment according to the route of exposure .5 MFAG tables A.4 Emergency Schedules (EmS)
This appendix describes the nature of toxicity in chemicals, and indicates how to avoid or limit exposure of crew members to their effects. It also briefly outlines ship design features and equipment intended to achieve protection. Where to find advice on treatment in the event of accidental exposure is included. The appendix does not repeat all the guidance on safe chemical tanker practices contained in the operational chapters. A.1 GENERAL A.1.1 Toxic substances A toxic substance is one, which is liable to cause either harm to human health, serious injury or death. Toxic means the same as poisonous. Toxicity is an intrinsic property of a chemical, which man cannot modify, and its effect is a function of exposure. In some cases, correct response to its effects after exposure can diminish its consequences. There are three common ways that a cargo can be toxic: swallowed (oral toxicity), absorbed through the skin, eyes and mucous membranes (dermal toxicity) or inhalation as a vapour or mist (inhalation toxicity). A chemical may be toxic by more than one of these routes: for example, toxic vapours and mists affect people most via the respiratory system but they can also be absorbed through the skin. The smaller the quantity (or dose) of the substance that is required to harm health, the more toxic a substance is. In some cases the toxic effect of a chemical can be countered by administering antidotes, but in most cases the hazard must be avoided by correct use of protective clothing, breathing apparatus and ventilation procedures. If there is no exposure to the chemical, or if exposure is reduced to safe levels, there can be no toxic effect. In tanker operations, contact with a liquid or inhalation of a vapour are the most likely forms of exposure. In general, proper procedures and proper use of. personal protective equipment will prevent exposure and thus the effects of toxicity. A.1.2 Toxic effects Toxicity can be acute, sub-acute and chronic. A substance has acute toxicity if a single exposure is sufficient to cause harm almost immediately. Substances commonly called poisons have extreme acute toxicity. A substance with sub-acute toxicity displays its effects after a person has had repeated exposures to doses too small to cause an acute effect. Examples are allergic sensitisers, which induce reactions to other substances. A substance has chronic toxicity if its effects appear after a period of continuous exposure to doses too low to cause any acute effect. Examples are carcinogens (cancer inducing), teratogens and mutagens (which affect reproduction). A.1.3 Threshold limit value (TLV) A threshold limit value for a given substance is the maximum concentration of its vapour in air to which it is believed that personnel may be exposed under certain circumstances without suffering adverse effects. Various governmental bodies publish TLVs. These should not be regarded as the
absolute dividing line between safe and hazardous conditions. It is good operating practice to keep all vapour concentrations to a minimum and a safe margin below the TLV. The best known list of TLVs is issued by the American Council of Governmental Industrial Hygienists (ACGIH). The values are updated annually in the light of new knowledge, so it is important to refer to the latest edition. The ACGIH defines three categories of TLVs: • TLV - TWA (Time Weighted Average): the concentration of vapour in air which may be experienced for an eight hour day or 40 hour week throughout a person's working life. This is the most commonly quoted TLV. • TLV - STEL (Short Term Exposure Limit): the maximum concentration of vapour in air allowable for a period of up to 15 minutes, provided that there are not more than four exposures per day and at least one hour between each. It is always greater than the TWA. It is not given for all vapours. • TLV - C (Ceiling): an absolute maximum which should never be exceeded. It is given only for fast acting substances. This is the highest of the three values for a given substance. A.1.4 Precautionary principles Containment is the first objective when any toxic substances are handled, by making sure that they stay inside the cargo system. Engineering and ship design features will provide a secure storage space. If there is no exposure there is no toxicity danger, however hazardous the chemical can be. Leakage of liquid or release of vapour must be prevented by keeping the cargo system closed unless it is absolutely unavoidable to open it. However, some operations inevitably involve opening the system; for example, disconnecting a hose from the ship's manifold after transfer of cargo. Although this is a routine operation, it should be regarded as comparable to opening up a cargo line elsewhere on deck, and operators must wear the necessary personal protective equipment. A.1.5 Toxic vapour detection and personal protective equipment Most chemical vapours are heavier than air and tend to flow along the deck and accumulate in low spots, for example below pumproom floor plates. Therefore atmosphere samples should always be taken in such low points where concentrations are likely to be highest. Vapour detection is covered in Section J.8. It is important that a full chemical suit is worn by personnel when: • inspecting pipelines and machinery for leaks; • dealing with accidental leaks and spillage; • connecting and disconnecting hoses and loading arms; • taking ullages and samples from tanks (where restricted gauging is permitted); • entering enclosed spaces such as pumprooms, cofferdams and tanks unless certified gas free; • opening up pumps and equipment (unless certified gas free). Personal protection is covered in Chapter 9. A.2 IMO CODE REQUIREMENTS The IBC Code specifies ways to limit exposure of personnel to toxic vapours while cargo is being handled, or during carriage at sea. First, it minimises toxic vapour emissions by controlling how cargo vapours are to be vented or returned to shore, and how tank contents are to be gauged. Virtually all toxic cargoes require closed or restricted tank gauges to prevent crews being exposed to unsafe concentrations of toxic vapours. Second, it specifies ventilation of working spaces such as pumprooms, requires the ship to carry equipment to detect vapours, requires the provision of personal protective equipment
and, to ensure that toxic vapours are diluted to safe concentrations before they can reach accommodation areas, requires that tank vent system outlets are located at a safe distance. (The safe distances specified depend on the severity of the toxic hazard.) Third, it reduces the likelihood of accidental overflow spills by specifying that all acutely toxic products and all allergic sensitisers are to be carried in tanks equipped with a visual and audible high level alarm (HLA). Tanks certified for the most severely acute toxic products must have a further overflow control system (see Section J.4). Finally, it specifies that cargo piping, including pumps, and venting systems of tanks carrying toxic cargoes are to be separated from those containing other products/ to prevent any leakage causing toxic contamination of non-toxic products and subsequent exposure of personnel unaware of the contamination. This is achieved on many chemical tankers by having separate pumps, pipelines and vents so that segregation is achieved by design, and on ships with common pipeline systems by the engineering principle of two physical stops, such as spectacle plates or a removable spool piece and blank flanges. Valve gland packing is the source of many small leaks. The correct packing material for the chemical being carried should always be used, and the glands correctly tightened. The IBC Code prohibits stowage of most toxic products adjacent to oil fuel tanks. The combustion of many otherwise non-toxic chemicals may produce toxic substances such as carbon dioxide and carbon monoxide, fumes of hydrochloric acid, hydrogen cyanide and nitrogen oxides. These may be present at some distance from the fire and may have no warning odour. Self-contained breathing apparatus should be used when dealing with chemical fires. The main danger from fume inhalation is asphyxia. Personnel affected by fumes should be removed rapidly to a fresh atmosphere, given oxygen and then treated appropriately as shown in the MFAG.
A.3 MEDICAL FIRST AID A.3.1 Basic documents The two fundamental guides for medical first aid on board ships, which give advice on dealing with exposure to toxic cargoes, are the International Medical Guide for Ships (IMGS) and the Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG). Both are published jointly by IMO, ILO (the International Labour Organization) and WHO (the World Health Organization). The IMGS gives guidance on common illnesses and is not solely concerned with chemical accidents. The MFAG is supplementary to the IMGS and contains advice for recognising and treating chemical poisoning, within the limits of the facilities available on board. The general rule is that if, during the handling of chemicals, any person shows symptoms that suggest poisoning, they should be treated in accordance with the MFAG and seen by a doctor as soon as practicable. Medical advice should be sought by radio, while still at sea. Assistance may also Be available from another ship with a doctor on board. A.3.2 How to recognise poisoning Section 4 of the MFAG gives directions on how to recognise the general symptoms of poisoning. Note that they may not appear for some time after exposure to the chemical. Symptoms to be alert to are unexpected headaches, nausea and vomiting, drowsiness, changes in mental behaviour, unconsciousness, convulsions, or pain. If the patient has a rapid but weak pulse, a greyish blue colour of the skin, severe breathing difficulty or remains unconscious for a prolonged period, severe poisoning must be suspected.
A.3.3 First aid and further care A first aider is not just a person with goodwill, but a person with training. MFAG Section 5 outlines immediate first aid, i.e. treatment for minor casualties, or to enable a victim to be moved so that further treatment can be administered. The key priorities to remember when reacting to a casualty are: • send for help and inform the master; • do not become the next victim yourself: if the response is too big for you alone, then wait for back-up; • remove the victim from the danger or vice versa; • use breathing apparatus if there is any suspicion of toxic gases or vapours in the area. The signs and symptoms of mild poisoning usually resolve after a few hours in the majority of incidents, particularly if the degree of exposure is small. However, if a greater amount is taken in, or the period of exposure is prolonged or the chemical is very toxic, symptoms may persist for much longer, even for some days. The patient's condition may continue to deteriorate even when clear of the source of the vapour, and systemic affects may appear. Finally, the warning is given that death may occur despite treatment. A.3.4 Emergency treatment according to the route of exposure In Chapter 8 of the MFAG, general advice can be found on the emergency treatment to be administered according to the way the chemical has entered the body, for example by skin or eye contact, ingestion or inhalation. If the chemical has affected both the skin and the eyes, the latter should get priority for attention. If the chemical has been ingested, the patient should not be made to vomit because the vomit may enter the respiratory system and add to the exposure problem. A.3.5 MFAG tables Appropriate reactions after exposure to the toxic cargoes listed in the IMO Codes are given by tables in MFAG Chapter 9. There are 12 group tables, but five chemicals require their own single substance tables, because they present particular combinations of toxic hazards (carbon disulphide, allyl alcohol, benzene, acrylamide and tricresyi phosphate). A.4 EMERGENCY SCHEDULES (EmS) The Emergency Schedules are an appendix to the IMDG Code and provide masters with advice on the immediate action to be taken in case of accidents such as spillage or leakage of toxic substances. , Operational guidance is given in Section 8.3. In brief, if it is safe to do so, spillage should be collected for subsequent disposal, but if there is any doubt, the spillage should be washed overboard with plenty of water, because the safety of the crew takes priority over pollution avoidance.
CORROSIVE SUBSTANCES B.1 General .1 Corrosive substances .2 Precautionary principles .3 Acids .4 Basic or alkaline substances .5 Personal protective equipment B.2 IMO Code Requirements B.3 Medical First Aid .1 Basic documents .2 Chemical burns .3 First aid and further care .4 MFAG tables B.4 Emergency Schedules (EmS)
This appendix describes the nature of corrosiveness in chemicals, and indicates how to avoid or limit exposure of crew members to its effects. It briefly outlines ship design features and equipment intended to achieve protection, and provides advice on treatment in the event of accidental exposure. The appendix does not repeat all the guidance on safe chemical tanker practices contained in the operational chapters. B.1 GENERAL B.1.1 Corrosive substances Corrosive substances destroy human tissue on contact (e.g. skin, eyes and mucous membranes in the mouth and the respiratory tract); metal or other material used in ship construction can also be corroded at an excessive rate. The most common corrosive liquids are acids and bases (or alkalis)/ and can be organic or inorganic. The most dangerous corrosives cause severe burns after a very short time. Some substances become corrosive only in the presence of water, or produce corrosive vapour when in contact with moist air. B.1.2 Precautionary principles Prevention of exposure is the most certain protection against the adverse effects of corrosives. Personnel should wear suitable and complete protective clothing when corrosive substances are being handled, with particular attention to eye protection. The ship itself also needs protection against corrosives. The safe containment of corrosive cargoes requires the use of corrosion resistant materials for the construction of cargo tanks and the handling system, including everything that is even remotely likely to come into contact with the cargo. Operators and crew must understand the danger of corrosion to normal ship steel if a concentrated acid leaks; there have been cases of ships being destroyed after such incidents. B.1.3 Acids In chemical terms, an acid is a substance containing hydrogen which, when dissolved in water, becomes dissociated and generates hydrogen ions. In high concentrations, many inorganic (or mineral) acids passivate mild steel rather than corrode it. But if the acid is diluted by-water then rapid corrosion will occur. The most corrosive concentrated acid cargoes include nitric acid, sulphuric acid, chlorosulphonic acid and chloropropionic acid. Formic acid and acetic acid are also highly corrosive in concentrations above 90%. Some acids are called fuming acids because of a characteristic appearance as they give off corrosive acid vapours, during which large quantities of acidic fumes are generated. Acids can also have other dangers. Nitric acid is a powerful oxidising agent. It can cause fire in contact with combustible materials; therefore materials such as sawdust and cloth should never be used to collect spilled nitric acid or other oxidising agents. Sulphuric acid and chlorosulphonic acid react violently with water; the reaction gives off large amounts of heat which causes the water to boil. Some acids are toxic as well as corrosive and can cause other damage to the body as well as the acid burn at the point of contact.
Chlorosulphonic acid, dichloropropionic acid, hydrochloric acid and oleum are toxic by inhalation; chloroacetic acid is toxic by ingestion. Acetic acid and acetic anhydride are flammable. Most other acids are themselves non-flammable but, in general, acids react with metals to evolve hydrogen which is highly flammable. Some acids have a relatively high freezing point, and need to be heated for sea transport to prevent solidiflcation. Examples are acetic acid, oleum (whose freezing point varies with its concentration) and super-phosphoric acid. B.I.4 Basic or alkaline substances Basic or alkaline substances are those which contain the oxidrile group OH-. When dissolved in water, basic substances get dissociated and generate OH- ions. Basic solutions contain such OH- ions in higher concentration than pure water. For example sodium hydroxide (caustic soda, NaOH) is a basic substance; dissolved in water it gets dissociated into Na+ and OH-ions. Common inorganic alkalis such as potassium hydroxide and sodium hydroxide are corrosive to aluminium, zinc, galvanised steel and mercury, so those materials must not be used in the cargo containment system when carrying such chemicals. Other corrosive alkalis are aliphatic and alicyclic amines, pyridines, sodium sulphide solutions and ammonium sulphide solutions, which have corrosiveness as either the primary risk or the secondary risk after flammability. Acid and basic substances react together to form salts and water, often with a violent emission of heat. For example sodium hydroxide and sulphuric acid react to form sodium sulphate and water. B.1.5 Personal protective equipment As already indicated, the principal protection is to avoid exposure by absolute containment inside the cargo system. However, protection is also needed against accidents. Normal fabric clothes and leather footwear provide no barrier against corrosive liquids. Therefore suitable protective equipment must be worn when corrosive liquids are being handled, with particular attention to protection of the eyes. Personal protective equipment is in many instances the only practical means of isolating the crew from the cargo, particularly in emergency situations. However, it is not a substitute for safe working practices and correct operational procedures. Personnel must wear adequate protective clothing when opening equipment which may contain acids, for example when ullaging and sampling, connecting and disconnecting hoses, opening sighting ports, working in the manifold area, entering pumprooms and tanks, investigating leaks and dealing with incidental spillages on deck. . Crew should receive training in the proper use and maintenance of the personal protective equipment aboard their ship. A full description of personal protective equipment is contained in Chapter 9. B.2 IMO CODE REQUIREMENTS The IBC and BCH Codes specify certain measures with regard to construction and equipment, intended to ensure safety for personnel and ship when carrying acids. The Codes require secure containment of the cargo inside a cargo system either constructed of suitable corrosion resistant materials, or fully lined or coated with stable corrosion resistant material, or having a sufficient margin of excess material to allow for corrosion. The Codes give detailed notes on these construction materials. The Codes control the location in which corrosives may be carried. Acids must not be carried in tanks where any boundary is formed by the ship's shell plating. The tank type is specified. Because other parts of the ship's structure may come into contact with a corrosive cargo as a result of a leak, arrangements must exist to detect a leak into spaces adjacent to the cargo
system. Control of leaks on the cargo deck is also addressed. Spray shields are required for cargo manifold connections, to prevent cargo spraying onto surrounding structure. The Codes prevent any cross-contamination of the fuel oil system with a corrosive cargo, by stipulating that the two liquid handling systems are fully segregated. A few acid cargoes are flammable but the non-flammable acids can react with metals to produce hydrogen. Therefore it is prudent to treat acid cargoes as though they were flammable liquids. A flammable atmosphere must be suspected inside the cargo system, in void spaces around cargo tanks, in cargo pumprooms etc. Electrical equipment in such spaces must comply with flammable atmosphere requirements for hydrogen-air mixtures. B.3 MEDICAL FIRST AID B.3.1 Basic documents The two fundamental guides for medical first aid on board ships, which give advice on dealing with exposure to corrosive cargoes, are the International Medical Guide for Ships (IMGS) and the Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG). Both are published jointly by IMO, ILO and WHO. The IMGS gives guidance on common illnesses and is not solely concerned with chemical accidents. The MFAG is supplementary to the IMGS and contains advice for recognising and treating chemical bums/ within the limits of the facilities available on board. The general rule is that if, during the handling of chemicals, any person shows symptoms that suggest chemical burning, they should be treated in accordance with the MFAG and seen by a doctor as soon as practicable. Medical advice should be sought by radio, while still at sea. Assistance may also be available from another ship with a doctor on board. B.3.2 Chemical bums Specific advice for the first aid treatment of chemical bums is given in sub-section 6.7 of the MPAG. Chemical burns are very similar to fire or electrical burns but with the added risk that the chemical may be absorbed through the damaged skin and cause further damage through poisoning. Three symptoms are described to help recognise (diagnose) bums: • burning pain, with redness at the point of contact (though sometimes only an irritating rash); • in severe cases, blistering, loss of skin and underlying tissue; • nausea, vomiting, headache, breathing difficulties and confused mental state: unconsciousness implies poisoning complications. The basic recommendation is to check the chemical data sheet immediately and radio for medical advice. B.3.3 First aid and further care MFAG Section 5 outlines immediate first aid, i.e. treatment for minor casualties, or to enable a victim to be moved so that further treatment can be administered. The key priorities must be remembered when reacting to a casualty: • send for help and inform the master; • do not become the next victim yourself: if the response is too big for you alone, then wait for back-up; • remove the victim from the danger or vice versa; • use breathing apparatus if there is any suspicion of toxic gases or vapours in the area. In case of contact with the skin, the victim should immediately be put under an emergency shower, to wash off the corrosive with very large quantities of water. The victim's clothing and shoes should be removed while under the shower. If even a minute quantity of acid has entered the eye, it must be irrigated immediately with plenty of water for a minimum of 15 minutes, or more if necessary. Use an effective eye irrigation fountain.
First aiders must always wash their own hands and forearms and then use sterile materials for treatment/ as burns may easily develop into infections. Cotton wool or other linty materials should not be used for cleaning burns, as they are likely to leave bits in the burn. Blisters should be left intact. Vaseline gauze dressing should be used to cover burns, however small, so that the dressing does not stick to the damaged flesh. B.3.4 MFAG tables First aid advice concerning groups of corrosive chemicals or single chemicals is given in a number of tables in MFAG Chapter 9. Group table 700 covers acids, including those subject to the special requirements of the IBC Code. Table 610 applies to nitric acid in concentrations not lower than 70%, as it is likely to give off nitrogen oxides which are highly toxic to the lungs. Ammonium nitrate solutions are covered by table 235, the group table for nitrates and nitrites. B.4 EMERGENCY SCHEDULES (EmS) The Emergency Schedules are an appendix to the IMDG Code and provide masters with advice on the immediate action to be taken in case of accidents such as spillage or leakage of corrosive substances. The response to a spillage will depend on where the spillage occurs, the quantity involved and if remedies other than water are available. If it is safe to do so, spillage should be collected for safe disposal but, if there is any doubt, the safety of the crew takes priority over pollution avoidance. Dispersal of corrosives should not be delayed.
REACTIVE CHEMICALS AND RELATED PRECAUTIONS C.1
C2 Unstable Chemicals .1 Reaction characteristics .2 IMO Code requirements C3 Chemicals which React with Oxygen .1 Reaction characteristics .2 IMO Code requirements C.4 Chemicals which in Contact with Water Emit Dangerous Gases .1 Reaction characteristics .2 IMO Code requirements C.5 Incompatible Chemicals .1 Reaction characteristics .2 IMO Code requirements .3 The USCG compatibility chart C.6 Guidance in the Absence of Adequate Reactivity Data
REACTIVE CHEMICALS AND RELATED PRECAUTIONS This appendix describes the phenomenon of important chemical reactions, and indicates the particular safety hazards to ships' crews. It gives an outline of the ship design features and equipment intended to provide protection against such reactions, as well as guidance on safe procedures for dealing with them. C.1 INTRODUCTION In general, chemicals carried by sea are stable and, provided proper and appropriate care is taken, can be loaded, stored and discharged satisfactorily. Some chemicals, however, need special care to ensure that they remain in the same condition as loaded. They may be intrinsically unstable or they may react with air, water or other materials. The reaction changes the composition of the mixture. Some chemicals react with each other when mixed together under suitable conditions. Dangerous reactions are those emitting heat, and those that generate hazardous vapours and gases. A reaction which produces heat is called an exothermic reaction. The speed of reaction varies widely depending on the chemicals involved but, as heat is generated, reaction rates increase. A very fast reaction may cause an explosion. A chemical reaction that must absorb heat to proceed is called endothermic. This does not usually present any hazard in bulk chemical shipping. For the sake of clarity in this appendix, reactive chemicals are divided into: • unstable or self-reacting chemicals, either decomposing or polymerising; • chemicals capable of reacting with oxygen in the air, either forming peroxides or liable to putrefaction; • chemicals which react with water to emit dangerous gases; • incompatible chemicals, which react dangerously if mixed together. C. 2 UNSTABLE CHEMICALS
. C.2.1 Reaction characteristics Unstable chemicals react within their own mass, without other chemicals participating in the reaction. Unstable chemicals either decompose or they polymerise. Substances that decompose do so into lighter and more volatile substances, and while doing so generate heat and evolve toxic and flammable gases. The decomposition is often initiated by carriage at too high a temperature, or by contact with small amounts of other chemicals (impurities) acting as catalysts. A catalyst accelerates the reaction without taking part in it. The most common decomposition catalysts are acids, alkalis and metals. Acids are often the catalysts in the decomposition of corrosive substances, which yield toxic gases. The main danger of exothermic decomposition is an increase in pressure, in addition to the emission of toxic and flammable gases and vapours. Decomposition is prevented by adding a stabiliser, which neutralises the catalyst, and by controlling the transport temperature. Substances which polymerise form complex aggregates, called polymers, by the combination of two or more identical molecules from the original chemical, which is called the monomer. Polymers are heavier and more viscous liquids than the monomers. A polymerisation reaction
is exothermic. If polymerisation can start spontaneously, the substance is called self-polymerising. Although spontaneous polymerisation can occur at ambient temperature, it is more often initiated by an excessively high transport temperature. A spontaneous polymerisation of the cargo presents two kinds of dangers. First, heat is generated during the reaction, which may result in overpressure inside the tank, with consequent rupture of the containment. Second, while the monomer is often a light and volatile liquid, as polymerisation proceeds it produces heavier and more viscous liquids, or even solids, which may block the tank vents so that the pressure inside the tank increases even further. Moreover, if the problem is not detected in time, the tank may implode while being unloaded. Self-polymerisation is prevented by the addition of a sufficient amount of an appropriate inhibitor to the cargo and by controlling the temperature of carriage. C.2.2 IMO Code requirements The IBC Code specifies the precautions to be taken against spontaneous decomposition and polymerisation by the use of additives (stabilisers and inhibitors) uniformly distributed in the mass of the product, and by control of the carriage temperature. The Code makes the manufacturer of the unstable chemical being carried, who is not necessarily the shipper, responsible for providing the ship with a number of critical safety instructions concerning the additive in the form of a certificate showing: • what additive has been or should be introduced into the product, and how much; • when the additive was or should be introduced, and for how long it is expected to be effective; • the temperature conditions to be met in order to preserve the effectiveness and lifetime of the additive; • whether oxygen must be present in the liquid for an inhibitor to be effective; • what action should be taken if the voyage lasts longer than the effect of the additive. A tank should not be inerted if it is to carry a product protected by an additive that needs oxygen to be effective. Most inhibitors are not themselves volatile, so they do not vaporise with the cargo and are unlikely to be present in cargo vapours. Therefore, where cargo vapours condense/ for instance inside vent valves and flame arresters, polymerisation may occur. Local solidification of polymerising cargoes, sometimes referred to as crystallisation, within a cargo system should be prevented, as it may affect the uniform distribution of the additive within the mass of the cargo and therefore allow self-polymerisation to start in part of the cargo system. The IBC Code also contains provisions against the exposure of cargo to excessive heat. The preventive measures include prohibition from carriage in tanks or pipelines close to those used for products whose temperature is high enough to initiate a reaction in the unstable chemical, and controls on heating coils and use of deck tanks. The tank should be equipped with a high temperature alarm. C.3 CHEMICALS WHICH REACT WITH OXYGEN C.3.1 Reaction characteristics Some chemicals react with oxygen even without any input of additional energy. One group of such substances reacts slowly with oxygen in the air and with oxygen dissolved in the mass of the liquid, to form unstable peroxides. In another group, mainly natural products, the oxygen in air allows a process of decomposition called putrefaction, usually by the action of bacteria.
Organic peroxides, once formed, are thermally unstable, and the main danger is that at normal or elevated temperatures, they are liable to exothermic, self-accelerating decomposition. The decomposition can be initiated by heat, contact with impurities (e.g. acids, heavy metal compounds and amines), friction or impact. Some organic peroxides may decompose explosively, particularly if confined. The key precaution to prevent the formation of organic peroxides while carrying such cargoes is to exclude air from contact with the product by inerting the cargo system and making sure it remains inert. Temperature control is also important. When putrefying, vegetable and animal oils and greases are slowly oxidised in contact with air by the action of bacteria. A cargo which has suffered putrefaction is said to have gone off, due to the foul odours evolved. There are two dangers associated with this process. Not only are the foul vapours and gases ultimately toxic, but also the consumption of oxygen in the tank atmosphere means that it can no longer support life. A great many lives have been lost, unnecessarily, through lack of attention to these dangers (see Section 5.11.3 and Chapter 3). The control of temperature is an important step to prevent putrefaction, particularly since the products liable to suffer such fate are normally not transported in an inert atmosphere. C.3.2 IMO Code requirements For cargoes susceptible to formation of peroxides, the IBC Code specifies measures to control the environment or atmosphere inside cargo tanks, including inerting. Inert gas with a very low level of oxygen is needed, and nitrogen is preferred. The Code requires sufficient inert gas to be available to purge air out of the cargo system before loading, to achieve a positive overpressure in the loaded tank, to compensate for losses during transport (thus it must be available when at sea), and to maintain the inert atmosphere during unloading. The cargo handling system for each of these cargoes should be independent of all others, and accidental cross connections should not be possible. C.4 CHEMICALS WHICH IN CONTACT WITH WATER EMIT DANGEROUS GASES C.4.1 Reaction characteristics The reaction of some chemicals with water, including the humidity of air, generates gases which are flammable, or toxic, or both. One group of such chemicals is those containing the di-isocyanate group (for example toluene di-isocyanate), which react with water to form carbon dioxide, an asphyxiant gas. Before entering any space where such cargoes have been carried or into which cargo leakage may be suspected, the precautions for entry into enclosed spaces (see Chapter 3) should be carefully observed. C.4.2 IMO Code requirements Products which in contact with water emit dangerous gases should be kept totally separated from water, and in a dry atmosphere. The Code requires a double separation between water-reacting substances and water. The cargo should not be carried in tanks adjacent to water tanks or permanent ballast tanks unless those tanks are empty and dry, nor adjacent to other tanks containing water, such as slop tanks and cargo tanks with water solutions in them. The same level of double separation requires that pipelines containing water (such as slop or ballast lines) should not pass through the tank, unless encased in a tunnel. If temperature control is required, neither steam nor hot water should be used to heat the cargo. The entire cargo system (tank, pump, lines and vents) should be completely segregated from other cargo and ballast systems, and pressure/vacuum relief valves should discharge at least 2 metres above the weather deck. A particular safety hazard is presented by tank cleaning after carrying these products. The tank should not be
cleaned with water unless the shipper of the product or the shipowner has specified a safe procedure for doing so. Either different washing means should be employed, or the procedure used must assume that dangerous gases will be emitted and correct measures stipulated to avoid exposing personnel to danger or the ship to harm. C.5 INCOMPATIBLE CHEMICALS C.5.1 Reaction characteristics Chemicals belonging to certain families are known to react with those of other families when in contact with each other. Such reactions can be hazardous. Generation of toxic gases, heating of the liquids, overflow and rupture of cargo tanks, and fire and explosion are possible consequences. At the very least the cargoes will have changed their nature, and require reassessment. The classic case of incompatibility is that between an acid and an alkali, which neutralise each other to form a salt plus water. Sulphuric acid is incompatible with every other group. Nitric acid is generally compatible with other acids, except sulphuric. There is some compatibility between organic acids on the one hand and amides and aromatic amines on the other. Among alkalis, aliphatic amines are a sensitive group as they are incompatible with all other groups except other alkalis. C.5.2 IMO Code requirements Incompatible chemicals must of course be kept strictly separated from each other throughout the entire cargo containment and handling system, in order to avoid accidental mixing. Separation should be achieved by having two barriers between the containment systems of the incompatible chemicals. The tanks should be separated by a cofferdam, an empty tank, a void space, a tank containing a mutually compatible cargo, or a piping tunnel. The piping or venting systems for incompatible cargoes should be separated by removing a valve or spool piece and blanking off the exposed pipe ends, or installing two spectacle flanges with a bleeder or equivalent means to detect leakage in the pipe between the spectacle flanges. Cleaning a tank and the related cargo handling system should be performed thoroughly if consecutive cargoes are incompatible. C.5.3 The USCG compatibility chart Several authoritative bodies have divided chemical cargoes into groups, denning criteria for incompatibility between groups, and have published lists of incompatible cargoes. The most familiar is published by the US Coast Guard. According to this source, a mixture of two chemicals is considered hazardous (and the chemicals in question declared incompatible) when, under specified test conditions, the temperature rise of the mixture exceeds 25 °C or a gas is evolved. The compatibility guide assigns each bulk chemical cargo to one of 22 Reactive Groups and 14 Cargo Groups. Reactive Groups contain those chemicals which are the most reactive, so that dangerous reactions can be identified between members of different Reactive Groups and between members of Reactive Groups and Cargo Groups. Chemicals assigned to Cargo Groups are much less reactive, and do not react dangerously together. Whether cargoes within a pair of groups are incompatible is indicated in a table, known as the Compatibility Chart. It is important to note that, while the table gives general indications, the footnotes and data sheets for two particular cargoes should always be consulted because there are a number of exceptions to the Compatibility Chart.
C.6 GUIDANCE IN THE ABSENCE OF ADEQUATE REACTIVITY DATA It cannot be stressed too strongly that parcels of chemicals should not be accepted for shipment or loaded onto a ship unless positive assurance is available that the various chemicals are compatible within the segregation capability of the vessel. Those responsible for soliciting, scheduling and loading parcels of chemicals should always satisfy themselves that the various parcels scheduled for any given voyage of any given ship are mutually compatible and can be safely loaded and carried within the normal segregation capabilities offered by the ship. The ultimate responsibility for the safety of the ship lies with the master, who should ensure that the cargo distribution proposed for a voyage provides proper segregation or compatibility, using the data sheets of all the chemicals to be loaded. If the data sheets fail to provide the necessary information, the master should defer loading the cargo until consultation with the owner or other authority has produced satisfactory assurance that the proposed segregation plan for cargoes to be loaded is safe.
D.1 Introduction D.2 Description of the Process 1 Generation of electrostatic charge inside a ship's tank .2 Electrostatic field, charge relaxation and surface voltage .3 Charge accumulation and relaxation in liquids .4 Generation of charged mists .5 Potential electrodes for sparks to jump from D3 Control of Static Electricity .1 General .2 Turbulence .3 Safe pumping rate .4 Presence of water .5 Gas bubbling up through the filled tank .6 Relaxation time downstream of filters .7 Unearthed conductors .8 Projections and probes in tanks .9 Gauging and sampling of tanks .10 Washing of tanks .11 Steaming .12 Bonding and earthing
This appendix outlines the process by which static electricity is generated, and ways to reduce or avoid such generation. In view of the prevalence of undefined atmospheres in the cargo tanks of chemical tankers, it is of paramount importance to avoid all sources of ignition. D.1 INTRODUCTION Static electricity is generated by friction that occurs between different materials during relative motion. Electrostatic charges can then accumulate in materials which are poor conductors of electricity or which are good conductors but are insulated. If two such bodies with accumulated static electricity charges are brought close together, and if the difference of potential is great enough, the accumulated charge will jump between them. Anyone who has received a mild shock when touching a doorknob after walking across a carpeted room has experienced such a phenomenon. In such cases the individual has become charged by friction between the carpet and the soles of the shoes and the potential accumulated in the body is discharged to the knob. This, though annoying, is harmless. But if a strong discharge of static occurs as a spark where a flammable atmosphere is present, there is a risk of igniting the atmosphere. The process whereby this may happen in a chemical tanker consists of five steps: 1. An electrostatic charge is generated in the liquid as it flows turbulently through the loading pipeline into the ship's tank. m most liquids the charge is released instantaneously to earth* because the liquid conducts it. 2. But in some cases, the charge is accumulated in the liquid because the liquid has a low electrical conductivity. Such liquids are called static accumulators, and are generally found among more highly refined products. An electrostatic field is formed inside the tank. 3. A non-bonded projecting object, or something introduced into the tank, can become a potential electrode or spark promoter, collecting the charge from the liquid. 4. When close enough to an earth* the spark promoter instantaneously releases its charge in a spark through the atmosphere of the tank. 5. Such a spark will almost certainly have enough energy to ignite a flammable vapour. In chemical tanker operations, a flammable atmosphere may be unavoidable. It is the sequence of those five steps which must be prevented. D.2 DESCRIPTION OF THE PROCESS D.2.1 Generation of electrostatic charge inside a ship's tank The liquid flowing into the tank can be charged by friction with the loading pipeline and within the mass of the liquid, particularly if it is passed through a micropore filter, where the contact surface is large. If the liquid is allowed to fall freely into the tank (splash filling), friction with the air through which it falls adds further charge to it. When the liquid is not * The word 'ground' is sometimes used. In this context, earth and ground are synonymous.
miscible with water but contains water droplets, friction occurs when those droplets settle by gravity through the liquid in the tank. Similarly, if the liquid contains an undissolved gas, the liquid is charged when the gas bubbles rise through it. In order of importance, the principal charging mechanisms during filling of ships' cargo tanks are line filtering, splash filling and the settling of water droplets. D.2.2 Electrostatic field, charge relaxation and surface voltage When a charged liquid flows into a ship's tank, it attracts a charge of the same size as, but of opposite polarity to, the inner surface of the tank wall. Simultaneously a charge equal to that in the liquid (in magnitude and polarity) is repelled to the external surface of the tank wall, where it is immediately neutralized because the ship is earthed through the water. Inside the tank a difference in voltage exists between the charge on the wall and that in the liquid. The voltage at the earthed wall is zero. The voltage in the liquid increases with the distance from the wall. There is a voltage distribution in the tank space, called an electrostatic field. In time, the charge in the liquid migrates to the wall of the tank, where it combines with the charge of the opposite sign on the inner surface, the electrostatic field decreases and ultimately disappears. This process is called charge relaxation. Its speed depends upon the conductivity of the liquid. When water droplets or other charged particles (impurities) settle by gravity through the liquid in the ship's tank, a vertical electrical current is established and a high voltage may result at the surface of the liquid, called surface voltage. D.2,3 Charge accumulation and relaxation in liquids In the mass of the liquid, charge generation competes with charge relaxation: if the former is faster, charge is accumulated. The higher the conductivity of a liquid, the faster it relaxes electrostatic charges. Electrical conductivity is a property of a given liquid. It is measured in picosiemens per metre. Charge accumulation does not occur in liquids having conductivity well above 10 picosiemens per metre. Such liquids are called nonaccumulators. At conductivity below 10 picosiemens per metre, however, the accumulation of charge may be significant. Liquids of low conductivity are called static accumulators. For safety, the border is conventionally put at 50 picosiemens per metre. Charged foam, generated when splash filling some liquids, may retain its charge much longer than the bulk liquid, because the thin film in the foam bubbles provides only a very narrow path for the flow of the charge relaxation. D.2.4 Generation of charged mists Steam issuing from a nozzle can form a charged cloud of water droplets. A charged mist is also formed during the washing of tanks with high velocity water jets. Strong friction takes place at the nozzle, along the jet and by impact against the tank wall. Mists can remain charged much longer than bulk liquids: relaxation occurs only as fast as the droplets agglomerate and settle, since air is practically a non-conductor. Such high voltages can be produced that sparks can occur even in air. D.2.5 Potential electrodes'/or sparks to jump from When an insulated or unearthed electrode is immersed into an electrostatic field, it becomes charged through the same mechanism described for the tank wall, but the charge has no path to earth, A spark can then jump from the electrode to the tank wall. If the voltage is sufficient and if the atmosphere is flammable, ignition will occur. Examples of such objects are a metal sampling can lowered by a rope, or a thin metal scrap buoyed by foam. If the voltage is big enough, the same process can take place even if the object is a non-metallic solid. At high surface voltages a spark can jump to the liquid surface itself. This is called a brush discharge. Long slugs of water produced by the high capacity washing machines once used in VLCCs are thought to have caused incendive discharges to tank structures in past accidents.
D.3 CONTROL OF STATIC ELECTRICITY D.3.1 General Controlling any one of the first three steps listed in Section D.1 can eliminate ignition due to electrostatic sparks. The flammable atmosphere is assumed to be accepted. D.3.2 Turbulence Splashing and spraying of static accumulators should generally be avoided/ as they lead to the formation of charged mists or foams. A charged mist can be ignited even if the temperature does not reach the flash point: so splash filling and spraying are a danger even with relatively high flash point cargoes. Filling of a ship's tank should normally be through a pipeline which ends near the bottom of the tank so that, in the early stages of loading, the liquid is gently laid on the bottom. When the rising liquid covers the pipeline outlet, turbulence in the tank is considerably reduced and fewer static charges are generated. D.3.3 Safe pumping rate The faster the liquid flows through the pipeline to the ship's tank, the higher is the electrostatic charging. To avoid excessive turbulence within a static accumulator cargo, the velocity of liquid entering a tank should be very low until the inlet is well covered (see Section 5.3.5). Low velocity also limits any mixing with water that might be present in the tank bottom. After the inlet has been submerged, the flow velocity may be increased, but it should still minimise turbulence and avoid breaking the liquid surface. D.3.4 Presence of water Most static accumulators are not miscible with water. The presence of water produces two sources of static electricity. First, friction occurs at the surface of the water droplets dispersed within the cargo liquid, so far more static charges are generated than if the cargo liquid did not contain the water. Second, the charged droplets settle through the liquid and gather at an interface, producing a high voltage at the liquid surface. This process may continue even after tank filling has ceased. D.3.5 Gas bubbling up through the filled tank After loading, pipelines are often blown through using air, nitrogen or other gases. When the gas enters the tank from the bottom it will rise through the liquid in small bubbles, generating a high voltage at the surface. If it is necessary to blow through after loading a static accumulator, the amount of gas allowed to enter the ship's tank should be kept to a practical minimum. D.3.6 Relaxation time downstream of filters Micropore filters made of paper, cloth, felt, chamois or a metal grid, particularly if deep and thick, are prolific generators of electrostatic charges. Strainers such as perforated metal baskets are not. The liquid is highly charged when it leaves the filter in the loading line. For such charge to be relaxed, the liquid has to flow quietly in the pipeline for some time, before entering the ship's tank. Practical experience has shown that 30 seconds is sufficient. Filters are usually located ashore so the transit time is adequate, but if the distance between the filter and the ship's tank is not great enough, either the flow rate should be reduced, or the pipe length increased or its diameter enlarged, or a relaxation tank should be provided in between the filter and the storage tank.
D.3.7 Unearthed conductors A conductor having no electrical contact with earth can become charged and rise in voltage through induction (without physical transfer of charges) and collection (with physical transfer). An unearthed conductor floating on the surface of a charged liquid actually collects charges from it. A conductor located in a charged mist becomes charged to approximately the same voltage as the mist, even though it cannot collect any charge. In summary, a rise in voltage is possible without charge transfer to an unearthed conductor. If a spark then jumps between the unearthed conductor and an earthed metal surface all the energy the former has accumulated flows instantly into the spark, which therefore has a higher chance of being incendive. Avoiding the presence of unearthed conductors in ships' tanks is of fundamental importance to prevent incendive sparks, because they provide the electrode from which a spark can jump. The following are examples of unearthed conductors which might be present inside a ship's tank: • thin metal scraps, including rust: they do not float, but can be buoyed up by charged foam; • a metal coupling at the end of a non-conductive cargo hose used for filling the tank; • a metal rod or the tube on a gas sampling meter; • a metal sampling can or thermometer holder lowered on a non-conductive rope; • a tank washing machine on the end of a hose having a broken bonding cable, particularly when the hose is empty; • dropped tools falling through a tank filled with a charged mist from water washing: the mist might be invisible. D.3.8 Projections and probes in tanks Tanks are sometimes equipped with sounding pipes which extend down from underdeck towards the liquid surface. Other examples of projections and probes are high level alarms, spraying nozzles and fixed tank washing machines. If the liquid being loaded is at a high surface voltage, an incendive brush discharge to an unbonded projection may take place. The need to avoid such a situation will have been taken into account during the design of fixed projections inside a cargo tank, and all requirements for safety as to materials of construction, earthing, insulation and static electricity generation will have been checked while the ship was being built. It is important that any routine servicing should be performed in accordance with manufacturer's instructions, but no on board modifications to the equipment itself should be contemplated. D.3.9 Gauging and sampling of tanks Whilst loading a static accumulator cargo, conductive objects which are not bonded to the ship's structure such as metal sampling cans, gauge tapes and thermometers should not be lowered into a tank. A period of 30 minutes should elapse after filling has stopped for the charge to be relaxed before any unbonded metallic or other conductive equipment is introduced. A metal sounding rod, suspended on a rope, will not be earthed. The metal becomes charged when it is immersed in the charged liquid and, when it is then lifted, a metal to metal spark may jump between the rod and the rim of the tank opening, with a high probability of being incendive. If the surface voltage of the liquid is very high, it is possible to get an incendive brush discharge to the equipment when it first approaches the surface of the liquid during lowering. Completely non-conductive equipment could in theory be used, but in practice it is difficult to ensure that such material remains non-conductive because it is habitually exposed to dirt and moisture. It is therefore better strictly to observe the waiting time in all cases. The restriction of this waiting time may be avoided only if the gauging and sampling equipment is lowered inside a sounding pipe that extends all the way down and is connected to the bottom of the tank, because the voltage inside the sounding pipe is small. It is important to note that a shorter sounding pipe is not safe.
D.3.10 Washing of tanks During tank washing, a charged mist is produced and is present throughout the space. Such mist persists for a few hours after washing has come to an end. If an unearthed conductor is lowered into the charged mist, it becomes charged to a voltage which may be high enough for an incendive spark to jump to some part of the tank structure. The limitations on water flow rate per nozzle, per machine and per tank have been established by extensive research (see Section 7.3.4), and should not be exceeded. If the water contains cleaning additives or is recycled, or the washing medium is other than clean water, washing should be conducted in a non-flammable atmosphere: i.e. the tank should be made inert. The practical aspects of tank washing are therefore important to observe. The operational precautions are fully described in Chapter 7, where emphasis is placed on use of a sounding pipe for dipping. D.3.11 Steaming Steam issuing from a nozzle will generate a mist of charged water droplets. Therefore steam should never be injected into a tank that may contain a flammable atmosphere. D.3.12 Bonding and earthing A spark cannot jump between two conductors which are either electrically bonded together or both earthed, because they are kept at the same voltage. Effective bonding is achieved by connecting a metal cable between objects. The cable is sometimes permanently fixed to one conductor and bolted or clamped to the other. At the removable end, contact should be metal to metal and care should be taken to make sure paint, dirt or rust does not hamper it. The cable should be strong enough to have good resistance to wear and tear. Bonding and earthing cables should be inspected periodically and their resistance checked with a meter. Many hoses used in marine operations are made electrically conductive. A pair of flanges bolted together can be relied upon for being electrically continuous, as can flexible joints of metal loading arms, so bonding or jumping wires around them are not needed. A different electrical phenomenon is experienced when a tanker is connected to a shore installation by a conductive hose or a metal loading arm. Ship, hose, dock and water form the elements of a battery and a large current can flow through the low resistance hose, even if the voltage difference between ship and shore is small. But this is not static electricity. When the hose is disconnected the current is suddenly interrupted and an electrical arc can be formed between the flanges. There is a risk of igniting a flammable atmosphere existing at the manifold. To prevent such a hazard, the ship has to be insulated from the shore pipeline by means of an insulating flange or a length of non-conductive hose, as described in Section 2.11.1. This keeps the circuit of the battery open, and prevents a spark. However, there is no need to connect a tanker to the dock by a bonding cable, since both are earthed by the water. The operational practicality of bonding cables is addressed in Section 2.11.2.
INERT GAS SYSTEMS E.1 Introduction E.2 Quality E.3 Gaseous Nitrogen Supplied from Shore E.4 Compressed Nitrogen Stored on Board E.5 Liquid Nitrogen Stored on Board E.6 Pressure Swing Adsorption (PSA) Nitrogen Generators E.7 Membrane Separation Nitrogen Generators E.8 Oil Fired Inert Gas Generators
INERT GAS SYSTEMS This appendix outlines the systems available on chemical carriers for inerting or padding cargo tanks. Chapter 6 of this guide provides safety advice about operational aspects of using inert gas and inert gas systems. E.1 INTRODUCTION In the context of chemical tanker operations and chemical cargoes/ an inert gas system may have three distinct uses: preventing a fire, preventing a chemical reaction or maintaining cargo quality. Flammable gases normally encountered in chemical tankers cannot bum in an atmosphere which is deficient in oxygen, and an inert gas is understood to be a gas used to produce such an atmosphere by displacing air. SOLAS specifies the standards necessary to do this. It may be achieved by using either nitrogen or oil fired flue gas, with a portable or fixed piping arrangement to supply the inert gas to the cargo tanks and, if applicable, the places surrounding the cargo tanks. Mandatory safety requirements for tank atmosphere control are given in the IBC Code; for example the system must be able to compensate for normal transportation losses and maintain an overpressure of at least 0.07 bar gauge at all times. There are several types of inert gas systems that can be used on chemical carriers. The most common are: • stored compressed nitrogen; • stored liquid nitrogen; • gaseous nitrogen supplied from shore; • nitrogen generators using pressure swing adsorption (PSA); • nitrogen generators using membrane separation; • oil fired inert gas generators. There are occasions when inerting is not appropriate for safety reasons, because exclusion of oxygen could create hazardous situations with a number of chemicals when shipped in monomer form. Such chemicals (e.g. acrylic acid, styrene and vinyl acetate) have added inhibitors to prevent polymerisation during transportation. In order to be effective, the inhibitors require the presence of oxygen dissolved in the monomer, and that oxygen is obtained from the air in the ullage space. Inhibited monomers must therefore be carried in tanks where the atmosphere has an oxygen level sufficient for the inhibitor to fulfil its purpose. E.2 QUALITY Most nitrogen used as inert gas on chemical tankers is not used for safety reasons but for cargo quality control. Shippers often have their own special requirements to ensure cargo quality, which can require inert gas of extreme purity, and may specify that nitrogen for initial inerting of cargo systems prior to loading a cargo will be supplied from the loading terminal. Smaller amounts of pure nitrogen can come from compressed or liquid nitrogen containers stored on board, and refilled from shore when required, but a very high quality can be produced on board by nitrogen generators based on membrane separation, or swing adsorption generators. When using an oil fired inert gas generator, an oxygen level of less than 5% can generally be obtained, depending on the quality of combustion control and the load on the boiler. The gas must be cooled and scrubbed with water to remove soot and sulphur acids before being supplied to the cargo tanks. But certain cargoes, for instance chemically reactive cargoes, are sensitive to oxygen concentrations as low as 2.0% by volume. Some cargoes react with carbon dioxide in Hue gases. Other cargoes are highly sensitive to moisture, or are liable to discoloration. For these reasons oil fired flue gas systems are rarely used on chemical carriers when carrying chemical cargoes, because demands for strict control of atmosphere
standards cannot be met. The following is an indication of potential problems that may occur: • acid catalyzed hydrolysis (e.g. with esters, acetates or acrylates); • acid catalyzed polymerisation (e.g. with allyl chloride); • formation of carbonates (e.g. with amines); • increased acidity (e.g. contamination of toluene and xylene by carbon dioxide); • reaction with water (e.g. with acetone or ethanol); • de-activation of polymerisation inhibitors (e.g. with vinyl acetate); • sulphur contamination (e.g. with methanol); • high chloride ion levels (e.g. because of sea water carry over from the scrubber/water seal which could affect the catalyst in subsequent reactions). Because of these real and potential problems with such cargoes, charterers now prefer that dry nitrogen is used for inerting a tank, and when preparing a tank atmosphere for loading. E.3 GASEOUS NITROGEN SUPPLIED FROM SHORE Supplies of pure nitrogen, for initial inerting of cargo tanks prior to loading a cargo, will generally be provided direct from the loading terminal. Occasionally, shore supplied nitrogen is also used for maintaining an inert gas overpressure while unloading. Such nitrogen is in gaseous form, and can be provided at high flow rates, greatly exceeding normal liquid flow rates. Although the operation is an important stage in cargo handling, it is also potentially hazardous because high pressure gas is being introduced into a tank not designed to withstand internal pressure, and the structure of the tank may fail due to overpressure. For the associated risks of the operation, see Section 5.7. E.4 COMPRESSED NITROGEN STORED ON BOARD High pressure gaseous nitrogen can be stored in steel cylinders; the common size is 50 litres capacity, pressurised to 200 bar, which will supply 10m3 of gaseous nitrogen. It can be used to compensate for normal transportation losses and to maintain the required overpressure. A typical installation on a ship consists of a number of such cylinders connected in parallel to form a battery, which uses a pressure regulator that is set to maintain the required positive pressure in the cargo tanks without lifting the tank pressure relief valve. Compressed nitrogen can be obtained in several grades of purity.
E.5 LIQUID NITROGEN STORED ON BOARD Nitrogen can be stored on board in liquid form, at the cryogenic temperature of -196°C. It is stored in insulated tanks made from cold-resistant material, usually stainless steel pressure vessels. The cryogenic tank has an outer casing of steel, protected by several layers of anti-corrosion paint. The space between the inner and outer tanks is kept under vacuum and is filled with a non-flammable, high efficiency insulation which allows nitrogen to be stored over extended periods without appreciable losses. Liquid nitrogen storage tanks fitted on chemical tankers are refilled in port from shore resources. When gaseous nitrogen is required for use in cargo tanks, the liquid is converted back to gas using a finned tube evaporator that obtains the necessary heat for vaporisation from the ambient air.
nitrogen of the purity required - typically with an oxygen content variable between 0.1% and 2% by volume, with water and carbon dioxide contents below 5ppm. Oxygen enriched air is vented as a waste gas, which must be exhausted to a safe area. E.8 OIL FIRED INERT GAS GENERATORS Oil fired inert gas is generally acceptable for use with petroleum products but it has been found that the quality of the inert gas generated by this type of system is not suitable for use with many chemical products, because it can affect the cargo quality. It is therefore recommended that when inerting or padding is required by the IBC Code for a particular cargo, nitrogen is used to inert or pad that cargo unless the shipper or supplier has stated that oil fired inert gas is acceptable for such purposes. The basic principle of oil fired plants is that the oxygen content of the air is converted to carbon dioxide by combustion of oil while the nitrogen content remains largely unchanged. The oil fuel is burnt in a combustion chamber and the combustion (or flue) gas is passed through a water tower (or scrubber) to cool it and remove most of the sulphur dioxide, particulates and impurities. This requires contact between the flue gas and large quantities of sea water. The gas may then be dried by being passed either through a cooler or an alumina bed dryer (or even both). Chemical tankers are usually fitted with two non-return valves in series as an equivalent to a deck water seal, thereby avoiding the risk of water carry over into the cargo. As a further safeguard against backflow, there is usually an isolating valve or a spool piece at each branch connection. The inert gas produced by oil fired generators depends on the quality of the fuel oil and the efficiency of the combustion and scrubbing processes. These factors influence, for example, the amount of sulphides in the inert gas produced - which is why the sulphur content of the fuel is limited in the plant specification. Likewise, inefficient combustion can cause soot, which clogs the scrubber and, in particular, the dryer system, thereby producing wet and dirty inert gas. If the plant is efficiently burning good quality fuel, the inert gas can be expected to have approximately the following composition: Carbon dioxide
Oxides of nitrogen
Sulphur dioxide and sulphur trioxide
ELECTRICAL EQUIPMENT AND INSTALLATIONS IN HAZARDOUS AREAS F.1 Introduction F.2 Certified Safe Electrical Equipment .1 Intrinsically safe equipment .2 Explosion proof or flame proof equipment F.3 General Precautions F.4 Electrical Maintenance and Repairs
ELECTRICAL EQUIPMENT AND INSTALLATIONS IN HAZARDOUS AREAS
F.l INTRODUCTION The electrical equipment and installations on chemical tankers are subject to requirements of the flag administration, classification societies, IMO and the International Electrotechnical Commission (IEC). The purpose of these requirements is to ensure that the electrical equipment is designed and fitted so as to minimise the risk of fire. Areas and spaces are classified as 'gas safe' or 'gas dangerous' depending on the risk of cargo vapour being present. Ashore, the definition of gas dangerous places takes account of whether continuous or intermittent presence of gas is expected. On ships, there is no such distinction and a place is continuously either gas safe or gas dangerous. Electrical equipment installed in a place regarded as dangerous (on ship or ashore) has to be of special construction, and certified safe for the area and the vapour concerned. Portable equipment taken into the areas should also be certified safe. One of the main considerations aboard chemical tankers is to ensure that the surface temperature of any electrical equipment does not exceed the auto-ignition temperature of any cargo that the ship may carry. Although there are a number of recognised certification authorities around the world that have slightly different test procedures and ways of grouping the surface temperature categories, the IBC Code specifies the temperature groups, and equipment must be installed and maintained in compliance with these requirements. F.2 CERTIFIED SAFE ELECTRICAL EQUIPMENT F.2.1 Intrinsically safe equipment Intrinsically safe equipment relies on low power circuits to limit the maximum energy available to less than that necessary to ignite a flammable mixture under normal conditions and certain fault conditions. The use of intrinsically safe systems is limited to instrumentation, control and alarm systems because of the very low energy levels to which they are restricted. F.2.2 Explosion proof or flame proof equipment The terms 'explosion proof equipment' and 'flame proof equipment' are synonyms and the one chosen depends on the country of origin or approval of the device. The equipment is designed with air gaps (sometimes called flame paths) between covers or removable parts and the enclosure. The air gaps are closely controlled, and are narrow enough to ensure that if an ignition were to occur in the equipment the resulting hot gases or flame would emerge at such velocities that surrounding flammable gas would not be ignited by the explosion. The concept is applicable to motors, junction boxes, circuit breakers and a wide range of other electrical equipment. A certificate for the integrity of the equipment is issued after laboratory testing. Care is essential in the maintenance and re-assembly of this type of equipment to ensure that the design features are not destroyed. In particular, the flame path should be kept dry and
should never be filled with jointing compound. The correct seals must be fitted at cable penetrations as these contribute to the explosion proof integrity of the equipment. F.3 GENERAL PRECAUTIONS Secure electrical bonding of the ship's structure, including independent cargo tanks, will have been arranged during its design. However, it may be appropriate to check that removable equipment, such as electric motor housings, located in any of the hazardous zones remains electrically bonded to the hull. Alarm or shutdown circuits which are working correctly should never be by-passed, overridden or isolated; such action could endanger the safety of the ship. Defective circuits may be by-passed temporarily in case of an emergency, but this action should only be taken with the full agreement of the responsible officer, and the decision should be recorded. The defect should be rectified and the circuit repaired as soon as possible, and the by-pass removed. Completion of the work should also be recorded. F.4 ELECTRICAL MAINTENANCE AND REPAIRS Certified safe equipment should be carefully maintained, preferably by qualified personnel; advice from the manufacturer should be sought in case of doubt. Equipment and installations should be regularly inspected. Electric light fittings are often made with a temperature expectation within a group that depends on the power of the lamp (bulb) installed. Great care must be taken to replace the defective lamp with one of the same power. Fitting a higher power lamp than the original can alter the temperature group of the fitting - with consequent restrictions on the cargoes that the ship may carry. When equipment in a gas dangerous area is disconnected for servicing, the associated wiring and conductors should be correctly terminated or adequately insulated. If it is necessary for the purpose of repairs or alterations to use soldering apparatus or other means involving heat or flame, or to apply voltage to apparatus for testing, the area must be made safe and certified gas free by an authorised person, and then maintained in that condition for as long as the work is in progress. When such hot work is considered necessary on a tanker berthed at a terminal, or on a terminal when a tanker is alongside, the joint agreement of the terminal and tanker should first be obtained and a hot work permit issued (see Section 2.12).
PRESSURE SURGE G.1 Introduction G.2 Generation of Pressure Surge G.3 Other Surge Effects
PRESSURE SURGE G.1 INTRODUCTION A pressure surge is generated in a pipeline system when there is any change in the rate of flow of liquid in the line. The surge can be dangerous if the change of flow rate is too rapid. Pressure surges are most likely to be created during cargo transfer as a result of one of the following actions: • closure of an automatic emergency shutdown (ESD) valve; • rapid closure or opening of a manual or power-operated valve; • slamming shut of a non-return valve; or • starting or stopping of a pump. If the total pressure generated in the pipeline exceeds the strength of any part of the pipeline system upstream of the valve which is closed, there may be a rupture leading to an extensive spillage. There are similar risks if a valve is opened rapidly to fill a downstream system. G.2 GENERATION OF PRESSURE SURGE The pressure at any point in the cargo transfer system while liquid is flowing under normal conditions has three components: • the hydrostatic pressure; • the vapour pressure of the product if the tank is closed, or atmospheric pressure if the tank is open; • the pressure generated by the pump, which is highest at the pump outlet but falls steadily with distance along the line due to frictional losses. The first two pressure components are constant and will be referred to as the static component. The three components of the normal flow are shown in Diagram I of figure G.1. Rapid closure of a valve superimposes an additional transient pressure. This is due to the sudden conversion of the kinetic energy of the moving liquid into strain energy by compression of the fluid and stretching of the pipe. The stop in the flow of liquid is propagated back along the pipeline at the speed of sound and as each part of the liquid comes to rest the pressure is increased. It is this disturbance that is known as a pressure surge. The height of the surge depends on the density of the liquid, the rate of its deceleration and the velocity of sound through it. The surge pressure is greatest if the valve closes instantaneously. The sequence of events after instantaneous valve closure is illustrated in Diagrams II-VI in figure G.1, and is described below. Diagram II shows the development of the surge as the valve shuts. Diagram III shows that upstream of the surge the liquid continues to move forward and still has the pressure distribution applied to it by the pump. Downstream of the surge, the liquid is stationary and its pressure has been increased at all points by a constant amount. There continues to be a downstream pressure gradient behind the surge, but a continuous series of pressure adjustments takes place in this part of the pipeline to equalise the pressure throughout the stationary liquid. These pressure adjustments also travel through the liquid at the speed of sound.
When the surge reaches the pump (Diagram IV) the flow through the pump ceases. The pressure at the pump outlet (leaving aside the static component) becomes approximately equal to the sum of the surge pressure and the output pressure of the pump at zero throughput. The process of pressure equalisation continues downstream of the pump. If not relieved in any way, the pressure throughout the whole length of stationary liquid reaches approximately the sum of the surge pressure, the pump outlet pressure at zero throughput and the static component. The final pressure adjustment to achieve this correlation leaves the pump as soon as the original surge arrives, and travels back to the valve at the speed of sound. The time required for the whole process is therefore ^ from the instant of valve closure, where L is the length of the line and a is the speed of sound in the liquid; this is known as the 'pipeline period'. Therefore, if the valve closes instantaneously, the liquid upstream in the line experiences an abrupt increase in pressure followed by a slower (but still rapid) further increase until the pressure reaches approximately the sum of the surge pressure, the pump outlet pressure at zero throughput and the static component. In practical circumstances the valve closure is not instantaneous and there is then some relief of the surge pressure through the valve while it is closing. The pressure front is less steep and as a result the height of the pressure surge is less than if closure had been instantaneous. The pressure rise created will be less and the reflected pressure rise will be relieved through the partially open valve. At the upstream end of the line some pressure relief occurs through the pump and this also serves to lessen the maximum pressure reached; however if a check valve is fitted it may aggravate the surge. If the effective closure time of the valve is several times greater than the pipeline period then surge pressure alleviation may be significant. Loss of pressure through the pump continues after the lapse of the time interval until the pressure throughout the line between the pump and the closed valve is reduced to the pump output pressure at zero throughput. This is the situation that would have resulted from a very slow closure of the valve, but the pressure surge would not then have occurred. Downstream of the valve an analogous process is initiated when the valve closes, except that as the liquid is brought to rest there is a fall of pressure, which travels downstream at the velocity of sound. However, the pressure drop may be relieved by vapour evolution from the liquid although the subsequent collapse of the vapour bubbles may generate shock waves; for example, if the downstream liquid flows up and down through the transfer arm or hose. G.3 OTHER SURGE EFFECTS The description above refers to the simple case of a single pipeline. In practical cases the design of a possibly complex system should be taken into account. For example, the combined effects of valves in parallel or in series have to be examined. In some cases the surge effect may be increased. For instance, with two lines in parallel the closure of a valve in one line can increase the flow in the other line before this line in its turn is shut down. However, correct operation of valves in series in a line can minimise surge pressure. The maintenance and regular testing of valve closure times is an important safety procedure.
FIRE FIGHTING - THEORY AND EQUIPMENT H.1 Introduction H.2 Theory of Fire Fighting
H.3 Fire Fighting Media .1 General .2 Water .3 Carbon dioxide and vaporising liquids .4 Dry powder .5 Foam .6 Inert gas system H.4 Fire Fighting Practice .1 General .2 Foam monitors .3 Fire fighting clothing .4 Training and equipment preparedness
FIRE FIGHTING -THEORY AND EQUIPMENT Guidance on operational procedures/or dealing with emergencies will be found in Chapter 8. This appendix describes the tools that may be used to extinguish fires on a chemical tanker, especially fires involving chemicals, and includes advice on some additional dangers of which the crews of chemical tankers should be aware. However, it does not go into details for each chemical that might be involved, nor discuss or recommend a correct fire extinguishing medium. General fire fighting theory is included in the International Safety Guide for Oil Tankers and Terminals. H.1 INTRODUCTION If a fire occurs, the action taken in the first few moments is vital. The man on the spot should raise the alarm and assess the situation. The emergency plan should be implemented (see Chapter 8). The minimum requirements for any ship's fire fighting equipment are laid down by the flag administration. The regulations are generally based on the principles of the International Convention for the Safety of Life at Sea (SOLAS) and, for ships certified to carry dangerous chemicals, on the IMO Bulk Chemical Codes. It is essential to maintain equipment to a high standard. Specialist training for crew members, in particular as required for chemical endorsement of officers' professional certificates, should be supplemented by regular drills on board.
H.2 THEORY OF FIRE FIGHTING Fire requires a combination of three elements: fuel, oxygen and heat or a source of ignition, and chemicals need the same combination in order to burn. The principal means of controlling and extinguishing a fire is to remove one or more of the elements, either by removal of the fuel, by cooling, or by excluding a supply of oxygen (air). But in chemical fires, the source of ignition may be heat from a reaction within the chemical itself or from a reaction after mixing chemicals, A supply of oxygen may be released from the chemical through heating by the fire. So fire fighting will be made more difficult. Without doubt, the best course is to prevent any fire occurring. Some liquid chemicals have properties which necessitate fire fighting techniques that differ from those used on simple oil fires. The following list indicates some of these properties: • some chemicals are soluble in water and at certain concentrations may be flammable; • chemicals which are soluble in water will generally destroy normal foam, so alcohol resistant or dual purpose foam is required; • some chemicals are heavier than, and insoluble in, water: they can be smothered by a blanket of water, provided application is gentle; • some chemicals react with water to produce heat and thus give off increased amounts of flammable (and in some cases toxic) gases; • some chemicals evolve large volumes of toxic vapours when heated; • some chemicals form otherwise unexpected toxic vapours when burning; • the comparatively low auto-ignition temperature of some chemicals increases the chance of re-ignition. The cargo data sheet for a chemical will draw attention to these unusual properties and indicate the correct fire fighting medium and special precautions for fire fighters.
H.3 FIRE FIGHTING MEDIA H.3.1 General Chemical tankers normally have two main fire fighting media available: water and either dry powder or an alcohol-resistant foam system. The minimum capacity and coverage of these systems is stipulated in SOLAS and the IMO Codes. In addition, some chemicals have properties that require special fire fighting equipment such as a water sprinkler system. The ability to deal with a fire in unusual chemicals is a criterion for gaining the Certificate of Fitness to carry those cargoes. The best way of dealing with a cargo fire in a tank is by means of a smothering agent, such as foam, carbon dioxide, or in some cases dry chemical powder, if possible coupled with sealing off the tank and cooling adjacent areas or spaces. H.3.2 Water Water is the most common cooling medium, but has limited effect on most chemical fires. If used, water should be applied as a spray or water fog, or in foam. Its use should primarily be for cooling down the chemical itself and surrounding structure, for cooling hot bulkheads and tank walls, and for reducing the concentration of vapours. It can also provide protection for the fire fighters by making a screen between the fire fighter and the fire. Water should not be used in the form of a jet directly onto the fire as that may spread the burning liquid by splashing or overflow, or through agitation of the liquid caused by violent boiling of the water. Non-volatile chemical fires which have not been burning for long can be extinguished by water fog or water spray if the whole of the burning surface is accessible. The heat in the surface of the liquid is transferred rapidly to the water droplets which present a very large cooling surface, and the flame can be extinguished with advancing and oscillating sweeps of fog or spray across the whole width of the fire. Any liquid fire which has been burning for some time is more difficult to extinguish with water, since the liquid will have been heated to a progressively greater depth and cannot readily be cooled to a point where it ceases to give off gas. H.3.3 Carbon dioxide and vaporising liquids Carbon dioxide is an excellent smothering agent for extinguishing fires when used in conditions where it will not be widely diffused. However, it has poor cooling qualities and the possibility of re-ignition by hot surfaces should be borne in mind. Due to the possibility of static electricity generation, carbon dioxide should not be injected into any space containing a flammable atmosphere which is not already on fire. Carbon dioxide is asphyxiating and cannot be detected by sight or smell. Halogenated hydrocarbons are vaporising liquids which have a flame inhibiting effect, similar to dry chemical powder, and also have a slight smothering effect. The different liquids available are identified by a system of halon numbers. The environmental disadvantages of halons are well known, and modem ships are not fitted with them. But where fitted, their use in emergency may be necessary and appropriate to save lives or the ship. As with carbon dioxide, halons and other chemical fire extinguishing gases are most effective in enclosed spaces, where they will not be widely diffused. All halons are considered to be toxic to some degree because contact with hot surfaces and flame causes them to break down, yielding toxic substances. After a fire has been extinguished, it is necessary to use suitable breathing apparatus to enter the space. H.3.4 Dry powder Dry powder is an effective fire fighting medium, which works by decomposing under heat into non-flammable gas. It is important that the powder is not damp or compacted.
Discharged from an extinguisher as a free-flowing cloud it can be effective in dealing initially with a fire resulting from a liquid spill on deck or in a confined space. It is especially effective on burning liquids such as liquefied gas, or liquids escaping from leaking lines and joints, and on vertical surfaces, for example diesel equipment fires. It is a non-conductor and thus suitable for use in dealing with electrical fires. It must be directed into the flames. Dry powder has a negligible cooling effect and so may not give protection against possible re-ignition from a hot surface. Certain types of dry powder can cause a breakdown of a foam blanket, and only those known to be compatible with foam should be used in conjunction with foam. H.3.5 Foam Chemical tankers built to the IBC Code have foam as the main fire fighting medium, and most use an alcohol-resistant or multi-purpose foam. The correct type of foam concentrate will be important in determining the range of cargoes that can be carried under the Certificate of Fitness. Foam forms a coherent smothering blanket over the burning liquid that cuts off the oxygen supply from air. Foam also has some cooling effect on the surface temperature of the liquid. Foam conducts electrical current and should not be used where high voltage current is involved, unless the electricity supply has been shut off. During the application of any foam, water fog may be used to protect fire fighters from radiant heat to permit closer approach to the fire. Care should be taken to prevent water falling onto the foam and reducing its effectiveness. H.3.6 Inert gas system The purpose of an inert gas system is to prevent cargo tank fires or explosions, and to separate the cargo from the air. It is not intended as a fixed fire fighting installation, but in the event of a fire the system may be of assistance in extinguishing it. H.4 FIRE FIGHTING PRACTICE H.4.1 General A fire involving chemicals is most likely to occur in a cargo tank or on the tank deck. However, in the case of a spill or tank overflow, or a side shell rupture, the fire may spread to the surface of the water surrounding the ship. H.4.2 Foam monitors Foam monitors are dedicated devices for delivering very large volumes of foam quickly. Large capacity monitors would normally be on a fixed mounting or on a mobile unit. As a principal fire fighting tool in the event of a fire in the cargo area, the operational readiness of foam monitors is essential. Every opportunity should be taken to practise their use; this is especially so for remotely controlled monitors. H.4.3 Fire fighting clothing All clothing gives some protection against heat and consequently from bums but, because it is not fire proof, it will be scorched if exposed to flame. Although immediate containment measures can be initiated in ordinary working clothes, fire extinguishing parties should be appropriately dressed. The most effective fire protective clothing currently available is made of lightweight fire-resistant fabric incorporating an aluminium covering, and is sometimes referred to as a fire proximity suit. However, this type of suit is not suitable for direct entry into fire areas. Heavier weight suits, known as fire entry suits, permit personnel wearing breathing apparatus to enter the actual fire area. Fire suits made of asbestos are now not recommended. Fire resistant clothing must be approved by the administration.
All protective clothing should be kept serviceable and dry, and should be properly fastened while being worn. Protective clothing should be stowed near lockers that contain breathing apparatus. It is of the utmost importance that personnel directly involved in fighting a chemical fire wear correct personal protective equipment. Many chemicals will release toxic fumes when burning, and breathing apparatus should be worn by fire fighters to guard against inhaling toxic vapours or dense smoke. Advice on personal protective clothing for chemical hazards is contained in Chapter 9. H.4.4 Training and equipment preparedness There are several important factors involved in fire fighting, the most significant being fire prevention, crew training and the condition and readiness of fire fighting equipment. Company regulations will be tailored to individual ships, and will cover organisation and training of personnel, and maintenance of fire fighting equipment. Fire fighting cannot be successful unless all equipment is operational and all personnel are well trained in its use and in emergency procedures. Practice makes perfect, and provides opportunities for consideration of various situations.
J.1 Introduction J.2 Alarms and Shutdown Circuits
J.3 Liquid Level Gauges .1 General .2 Float gauges .3 Radar, ultrasonic or microwave gauges .4 Pressure gauges .5 Tape gauge systems J.4 Overfill Detection Systems .1 High level alarms .2 Tank overflow control systems J.5 Pressure Indicating Devices .1 General .2 Bourdon tubes .3 Capacitive pressure transmitters .4 General precautions J.6 Temperature Monitoring Equipment . .1 General .2 Types of thermometers .3 General precautions J.7 Oxygen Analysers .1 General .2 Level of oxygen in air .3 Electrolytic sensors .4 Paramagnetic sensors .5 Selective chemical liquid absorption sensors .6 Personal oxygen monitors J.8 Cargo Vapour Detection Equipment .1 General .2 Combustible gas detectors .3 Thermal conductivity meters .4 Infrared detectors .5 Chemical detector tubes .6 General precautions J.9 Air Supply to Instruments and Controls
INSTRUMENTATION A wide range a/instrumentation may be fitted on a modern chemical tanker. Only an outline is given in this appendix, providing guidance on the safe and efficient operation of the equipment. T.1 INTRODUCTION Much of the monitoring and measurement during cargo operations on chemical tankers remains reliant on human interpretation of information, and subsequent decisions are made on the basis of training and experience. Those factors will continue to be fundamental to safe carriage of chemicals by sea. Modern measurement instrumentation has achieved an improved flow of information at a consistent standard, and modern control technology permits exact management of operations. However, in order to be able safely to take full advantage of the gains available, there is a need to understand the capability of the instruments and, equally, their limitations. The best source of detailed information about a particular system can be found in the manufacturer's advice, in particular regarding calibration or maintenance requirements.
J.2 ALARMS AND SHUTDOWN CIRCUITS An important feature of many modem measurement and control instruments is the ability to signal a particular situation. This can be a main operational alarm that gives an indication of a pre-set situation such as liquid level in a tank, or a malfunction alarm indicating a failure within a sensor's own operating mechanism. The designs and purposes of alarm and shutdown circuits vary widely, and their operating system may be pneumatic, hydraulic, electrical or electronic. Safe operation of plant and systems depends on the correct operation of these circuits and a knowledgeable reaction to them. The following precautions should be observed: • where provided, test facilities should be used before cargo operations commence, to check that the circuits and their alarms are operating: any instrument fault should be rectified; • wiring inside and outside cabinets should be checked for chafing, condensation, insulation deterioration, bad connections etc; • watchkeepers should be instructed how to distinguish between each audible alarm and what action is necessary; • the accuracy of all inputs to alarm circuits should be checked; • if an alarm is activated, the cause must be investigated and necessary remedial action taken; • if an alarm circuit becomes defective during cargo operations, it should be repaired as soon as possible. Defective circuits may be by-passed temporarily in case of an emergency, but this action should only be taken with the full agreement of the responsible officer and the decision should be recorded. Completion of the repair work should also be recorded. J.3 LIQUID LEVEL GAUGES J.3.1 General The accuracy required of chemical carrier level gauges is high because of the nature and value of the cargo. To limit personnel exposure to chemicals or their vapours while cargo is being handled, or during carriage at sea, the IBC Code specifies three methods of gauging the level of a liquid in a tank - open, restricted or closed - according to the health hazard of the product. Many chemical cargoes may not be gauged by manual dipping because to do so requires an opening to the atmosphere during operation. The use of completely closed gauging systems is necessary, so that no vapour is emitted. Examples of closed systems are float gauges or radar systems. Indirect measuring methods such as flow metering may also be used. Many more chemicals, although still hazardous, do not require quite such rigorous controls, and restricted gauging accepts that a very small amount of vapour may escape during gauging. An example is using a sounding pipe that reaches right into the liquid. Virtually all toxic cargoes require either restricted gauging or closed gauging. However, other cargoes can be gauged through openings in the ullage space. This is called open gauging. J.3.2 Float gauges These are closed gauges, and consist of a float which rises vertically on the liquid. It is attached by a tape to an indicating device for local reading, with provision for a drive mechanism for remote read-out. Particular attention is drawn to the following: • floats should be secured when at sea, except briefly during measurement of tank contents. If the float remains unsecured at sea it will almost certainly be damaged due to sloshing of the cargo; • remote and local readings should be compared frequently to determine discrepancies; • readings may need to be corrected to allow for tape and tank expansion or contraction, and ship trim and heel. Tables are normally provided for this purpose; • tapes should be checked regularly for free vertical movement of the float, and if damaged, should be replaced. Particular care is necessary with the rewind mechanisms which are carefully balanced: if obstructed, the gauge readings will be inaccurate;
• when tapes are renewed, or a gauge reassembled after maintenance, allowance should be made for the level at which the float begins to lift. Manufacturer's instructions should be consulted; • parts should be securely assembled: special care is necessary with tape-to-float and tape-to-reel attachments. Other designs of gauges use floats that rise and fall on the outside of a closed pipe which penetrates the main deck. Inside the pipe are fixed magnets and a series of switches that transmit a signal to a display unit, usually in the cargo control room.
J.3.3 Radar, ultrasonic or microwave gauges
These are also closed gauges, and work on the principle used by a radar set or an echo sounder. Pulses are transmitted from the top of the tank and the time taken for them to be reflected back is measured, and displayed as an ullage or depth. Special arrangements may be made to reduce interference by internal tank structure
Radar gauges are generally reliable, and most maintenance can be performed from outside, with the tank in the closed condition. Particular care is necessary to protect the delicate transmitters and receivers, and when calibrating this type of gauge. J.3.4 Pressure gauges Pressure gauges make use of the difference between atmospheric pressure and the pressure in the liquid near the tank bottom. Sometimes an additional sensor is mounted near mid-depth in a tank to improve accuracy and reliability. In some cases a system can adjust for cargo density by use of sensors at known levels, and in other cases a correction factor associated with specific gravity is necessary. A thermometer is usually included in the sensors, but a disadvantage of pressure gauges is that the cargo temperature may vary widely in a tank and, because correct density is dependent on temperature, an error in readings may develop. The delicate nature of sensors and their susceptibility to cargo leakage makes regular servicing essential.
J.3.5 Tape gauge systems These systems use a tape to check the level of cargo in a tank. The measuring probe may be inserted into the tank through a small diameter pipe with a ball valve at the end, and portable units can be attached or released from this valve by a screwed adapter to minimise the amount of cargo released. They sometimes have an interface detector, and a temperature sensor built in, with appropriate indicators in the displays. A system employing this type of connection can also be used to take cargo samples.
J.4 OVERFILL DETECTION SYSTEMS J.4.1 High level alarms Certain cargoes require the designated tank to be fitted with a separate high level alarm to give warning before the tank becomes full. The alarm may be activated by either a float operating a switch device, a capacitive pressure transmitter, or an ultrasonic or radioactive source. The activation point is usually pre-set at 95% of tank capacity. The high level alarm must be independent of the normal gauging system. High level alarms must be maintained according to maker's instructions and tested as required before cargo operations begin. J.4.2 Tank overflow control systems A better name for this would be a tank overflow prevention system. It is required for particular cargoes designated in the IBC Code. The system should come into operation when the normal operational procedures fail to stop the tank liquid level exceeding the normal full condition. The activation point is usually set at 98% of tank capacity. Operation of the system is required to be independent of the high level alarm described above. On activation, the system should give a visual and audible alarm, and a signal in sufficient time to permit sequential shutdown of onshore pumps and/or valves, and the ship's valves. The shutdown can be dependent or independent of the intervention of operators. Particular care must be exercised with regard to automatic shutdown systems that are independent of operator intervention. Express approval for their use is required from both the flag administration and the port state authorities. Automatic shutdown systems are normally designed to shut the main cargo tank filling valve if the liquid level rises above the maximum level permitted. Great care should be taken to ensure that the activation point is set accurately, and that the operation of the device is checked by simulation whenever the system is recommissioned. If the ship and shore shutdown circuits are to be linked their operation should be checked before cargo transfer begins; if not, the terminal should be informed of the closing rate of the ship's valves. (See Appendix G on pressure surge.)
J.5 PRESSURE INDICATING DEVICES J.5.1 General Pressure gauges are fitted at various points in the cargo system, on pumps, in pipelines and in tanks, some of which are specified in the IMO Codes. They may be used to indicate pressure in a liquid being pumped into or out of a tank, or static pressure such as inert gas overpressure. They can indicate negative as well as positive pressure, and can be linked to shutdown or alarm systems. It is important that procedures exist for ensuring that pressure gauges are checked and calibrated in accordance with manufacturer's instructions. J.5.2 Bourdon tubes These instruments measure pressure by the movement of a coiled or helical tube, the amount being directly proportional to the applied pressure. The movement is used to drive a pointer for local readings, or to control a gas pressure valve or to alter a variable resistance that will serve indirect readings. Indirect readings may be necessary to avoid direct connection between safe and dangerous areas. The following precautions should be observed: • the indicator should be periodically checked for zero calibration; • the gauge should not be used to consistently indicate pressures beyond 75% of its maximum reading if the expected pressure is steady, or 60% if it is fluctuating; • Bourdon tubes may be damaged by vibration or by excessive pressure pulsations; the latter can be eliminated by the use of a flow restrictor. J.5.3 Capacitive pressure transmitters Pressure in vapour spaces of cargo tanks (and elsewhere) can be monitored by measuring the effect of the existing pressure on sealed units that have a known internal pressure. By establishing the reference atmosphere in the sealed units at a low pressure, for example 0.8 bar absolute or 800 millibars, it is possible to continue to measure modest underpressure within a tank as well as overpressure. Deflection of the sealed unit is measured by an internal capacitor, which sends an electronic signal to a remote display. An external measurement of atmospheric pressure is necessary for the display to show gauge pressure. Alarm levels can be set as desired.
The physical size of the sensors is quite small, and when used for inert gas monitors the devices are often incorporated into housings of other sensors, such as radar ullage gauges. Similar units can be used to indicate higher pressures in liquids. J.5.4 General precautions The following precautions apply to all pressure sensing equipment: • materials of construction should be compatible with the cargo. For example, brass must not be used for pressure gauge internals for amine cargoes such as ethylenediamine. The IBC Code gives guidance on cargoes where special attention must be paid to materials of construction; • before measurements are taken, all valves in the direct line should be opened and all cross-connections shut; • no pressure gauge should be subjected to violent pressure change; • in ships carrying cargoes which can solidify or form polymers (e.g. phenol or styrene respectively) it may be necessary to flush gauge lines and sensor chambers; • if sensor lines are temporarily disconnected during maintenance they should be blanked. J.6 TEMPERATURE MONITORING EQUIPMENT J.6.1 General Temperature sensors are fitted so that the temperature of the cargo can be monitored, especially where required by the IBC Code. It is important to know the cargo temperature in order to be able to calculate the weight of cargo on board, and because tanks or their coatings often have a maximum temperature limit. Many cargoes are temperature sensitive, and can be damaged by overheating or if permitted to solidify. Sensors may also be fitted to monitor the temperatures of the structure around the cargo system. J.6.2 Types of thermometers Liquid/vapour thermometers rely on the expansion or contraction of liquid in a very fine-bore calibrated tube or capillary. The liquids most commonly used are mercury, ethanol or xylene. It is important to ensure that the liquid column in the instrument is continuous, otherwise the reading will be inaccurate. Liquid filled thermometers have a metal bulb containing a fluid which changes volume with temperature change. The changes are transmitted via capillary tubing to an indicator or recorder. The system is sealed under considerable pressure to overcome the effects of vapour pressure from the liquid. Mercury filled thermometers should not be used with aluminium and certain other materials. Bi-metallic thermometers consist of two metals with different coefficients of expansion which are welded together to form a bi-metallic strip. When heated, the strip will bend because of the unequal expansion, and the flexing movement can be used to drive a pointer in a similar manner to be Bourdon tube. Bi-metallic thermometers are susceptible to vibration and should only be installed in positions free from this effect. Thermocouples rely on heat applied to the junction of two dissimilar metals generating a very small voltage which can be measured. A change will indicate a change in temperature. Normally the voltage is sensed electronically and the read-out is remote. Resistance thermometers use the fact that the electrical resistance of certain materials changes with temperature, and that if it is measured it will indicate temperature. The material normally used in resistance thermometers is fine platinum wire. Its resistance is measured by means of an electrical resistance bridge connected to an indicator or recorder, normally by electronic means, and the read-out is remote.
J.6.3 General precautions The following precautions should be observed with all temperature indicating devices: • the thermometers used should be suitable for the complete range of temperatures expected; • the sensor should make good thermal contact with the material whose temperature is to be measured; • if readings do not change when expected, the instrument should be checked; • thermometers are easily damaged, especially those with capillary tubes. They should be handled with care and protected from mechanical damage and extremes of temperature beyond their scales/ otherwise they may become inaccurate; • when a fixed thermometer is removed from its working location, care should be taken to avoid loosening or removing its pocket, especially if the system is pressurised; • when a thermometer is replaced in a working location, care should be taken that it does not bottom in its pocket when screwed in, as this could cause damage. If the thermometer is slack in the pocket a material with high thermal conductivity (such as a suitable lubricating oil) can be used to ensure accurate readings; • electrical connections should be clean, tight and correct. Care should be taken to see that intrinsically safe leads are not cross-connected with ordinary power sources. J.7 OXYGEN ANALYSERS J.7.1 General Oxygen analysers are normally used to determine the oxygen level in the atmosphere of an enclosed space: for instance, to check that a cargo tank can be considered fully inerted, or whether a compartment is safe for entry. The use of oxygen detectors for checking the atmosphere before entry to enclosed spaces is discussed in Chapter 3. There are several types of oxygen analysers. In each case it is of vital importance that they are carefully maintained and tested, and that correct checks are made before use. When oxygen detectors are calibrated it is essential to use clean and uncontaminated air. If used strictly in accordance with the manufacturer's instructions, these instruments can be regarded as reliable. J.7.2 Level of oxygen in air Throughout this guide the percentage of oxygen in air is referred to as 21%, since most instrumentation in use on ships has a gauge or scale which reads to 21%. Strictly, however, the percentage of oxygen falls several hundredths of a percent below that figure, variously quoted between 20.85% and 20.95%. Modern instrumentation with digital indicators can measure so accurately that the full 21% may be impossible to obtain. If an instrument capable of such accuracy is in use, the maker's instructions should be carefully read and understood, so that proper interpretation of the readings can be made. It may be appropriate for the ship operator's instructions to make reference to the level of accuracy obtainable. J.7.3 Electrolytic sensor Analysers of this type measure the output of an electrolytic cell that is exposed to a sample of the atmosphere being tested. The current flow is related to the oxygen concentration in the sample, and the scale is arranged to give a direct indication of the oxygen content. The readings may be affected by the presence of certain chemical vapours. It is important that the manufacturer's advice is followed. An indicator which may be reliable for measuring the oxygen content of a space after thorough ventilation may not be suitable for checking the oxygen content in a mixture of air, inert gas and cargo vapour.
J.7.4 Paramagnetic sensors Paramagnetic instruments measure the deflection of a magnet pivoted in a symmetrical non-uniform magnetic field. The magnet is suspended in a chamber into which the gas sample is introduced; the deflection is directly proportional to oxygen concentration. These instruments can be used for detecting oxygen in mixtures of other vapours. It should be noted that some other gases, notably oxides of nitrogen, have comparable paramagnetic properties to oxygen. This technique cannot therefore be used if such other gases might be present in more than trace amounts. J.7.5 Selective chemical liquid absorption sensors In liquid absorption instruments a known volume of the atmosphere to be sampled is passed through a liquid which absorbs the oxygen, causing a volume change in the liquid. The final volume is measured on a scale which indicates the oxygen content of the original sample gas. J.7.6 Personal oxygen monitors Small instruments are available which are capable of continuously measuring the oxygen content of the atmosphere. They can be attached to clothing or sometimes are supplied with an armband. They should automatically provide an audible and visual alarm when the atmosphere becomes deficient in oxygen, so as to give the wearer adequate warning of unsafe conditions. J.8 CARGO VAPOUR DETECTION EQUIPMENT J.8.1 General The provision and use of vapour detection equipment is required by the IBC Code for a number of functions, including: • measuring concentrations of gas in or near the flammable range; • detecting low concentrations of cargo vapour in air and in inert gas, or in the vapour of another cargo; • measuring concentrations of oxygen in inert gas or cargo vapour, or in enclosed spaces. Personnel should fully understand the purpose and limitations of different vapour detection equipment, whether fixed or portable. J.8.2 Combustible gas detectors Combustible gas detectors are very common and are used to detect and measure combustible gases, usually within the concentration range of 0-100% LFL; that is, up to the point of flammability. Equipment can be fixed or portable. A sensor containing a filament of a special metal is heated electrically and a sample of gas is passed over it. Any combustible gas in the sample is oxidised catalytically. The heat given out alters the electrical resistance of the filament in proportion to the gas concentration, and this effect is displayed on a suitably marked meter. The filament can easily be de-activated by materials such as silicones, halogenated gases, acids, water, oil and lead. Filters may therefore be required in the sample lines. The equipment needs oxygen to operate, and can only be relied upon to detect combustible gas in air atmospheres, not in inerted atmospheres. If a mixture of inert gas and cargo vapour has to be tested, either an infrared or thermal conductivity meter must be used, or a sample must be mixed with air before a combustible gas detector can be used. A combustible gas detector will not indicate a safe atmosphere if a toxic vapour is involved: in such a case a different type of instrument should be used. The instruments are calibrated against a known gas, called a span gas. Performance in use may be affected if the gas sampled is different from that used for calibration, and an appropriate conversion factor may have to be applied to the readings.
Portable combustible gas detectors are frequently used to confirm the state of atmospheres believed to be free of cargo vapours/ such as prior to tank entry or hot work. When used for this purpose, readings should be taken by or under the supervision of a responsible officer who should be satisfied that the instrument readings are correct, and are accurately interpreted, before allowing the safety of personnel to depend upon them. The calibration should be confirmed, and readings should be taken from the top or bottom of a space depending on the vapour density of the cargo. Readings will be inaccurate if inert gas is present in the sample. When using the instrument every reaction of the meter is important, and not just the final resting position. The first movement indicates the presence of combustible vapour, while the final rest position indicates the concentration, as follows: • a final rest position within the scale indicates a gas concentration below LPL, expressed as a percentage of LFL; • a final rest position beyond 100% LFL indicates a concentration within the flammable range; • a needle movement first above 100% LFL and then to a final rest position of zero indicates a concentration above UFL. It is therefore strongly recommended that when a space is being checked the responsible officer should not be satisfied that an atmosphere is safe until consistent zero readings are obtained. Fixed gas detectors working on this principle have the same limitations as portable ones. Personal combustible gas detectors, capable of continuously sampling an atmosphere to detect the presence of small amounts of combustible gas, are also available. They should automatically provide an audible and visual alarm when the level of combustible gas reaches a set level, to give the wearer adequate warning of unsafe conditions. J.8.3 Thermal conductivity meters These instruments work by measuring thermal conductivity of samples of gas. They are sometimes called catharometers. Electrical power is applied to a heater filament which is used as the sensing element: the filament temperature stabilises at a value depending on the thermal conductivity of the gas around it. Any variation in the concentration of the gas affects the filament temperature, resulting in a change in electrical resistance which is in turn indicated by a meter. The principle is similar to that of the combustible gas detector, but the filament temperatures are lower and the instruments can be used to detect concentrations of gas from 0100% by volume (compared to 0-100% LFL). The filament may be mounted so that the sampled gas flows directly over it or diffuses into it. The direct flow type responds more quickly to concentration changes but is dependent on flow rates. The diffusion type gives a slower response but is less flow sensitive. It is important to note that changes in operating conditions (e.g. filament voltage or gas flow rate) may alter the filament temperature. The maker's handbook for the instrument should be checked. A thermal conductivity meter can be set to detect cargo vapour mixed with inert gas. The meter must be calibrated to suit the gas being tested, or manufacturer's correction curves used. Reference should be made to the manufacturer's instructions before every occasion of use. Note: The roles of combustible gas detector (J.8.2) and thermal conductivity meter (J.8.3) can be combined into one instrument, although the two functions - measuring percentage of LFL and concentration of vapour by volume respectively - remain distinct. In some ships, fixed gas detection equipment uses this combination technique. J.8.4 Infrared detectors Organic gases such as butane, methane and petroleum absorb infrared radiation. This property is used in fixed or portable equipment to detect such gases in concentrations over the range 0-100% LFL or 0-100% volume. Infrared radiation is passed through two tubes, one containing a known concentration of gas, the other containing the sample to be measured.
The extent of absorption is in proportion to the gas concentration, and the output from the two tubes is compared electronically. The electronic signal can be used to drive an indicating meter or a pen recorder, or to trigger other equipment such as an alarm. Calibration of the instrument is set for each gas to be measured. Infrared detectors will not reliably detect chemical gases, and are not commonly used on chemical tankers. J.8.5 Chemical detector tubes These instruments, often referred to as Draeger tubes, normally function by drawing a sample of the atmosphere to be tested through a proprietary chemical reagent in a glass tube. The detecting reagent becomes progressively discoloured if a contaminant vapour is present in the sample. The length of the discoloration stain gives a measure of the concentration of the chemical vapour which can be read from the graduated scale printed on the tube. Detector tubes give an accurate indication of chemical vapour concentration, whatever the oxygen content of the mixture. It is important that the correct volume of atmosphere sample, according to the manufacturer's instructions, is passed through the tube, otherwise the measurement will not be accurate. Too small a sample volume will give a low value. With some instruments the length of hose is a critical factor in obtaining a correct reading. The presence of a second gas may affect readings and cause inaccuracies. Chemical detector tubes are specific for particular gases or vapours, which need not have flammable or combustible properties - for example, oxygen or water vapour (to establish dewpoint). The tubes are designed to measure low vapour concentrations accurately, and are probably the most convenient and suitable equipment to use. They should always be used when the cargo vapour presents a serious inhalation hazard, e.g. acrylonitrile. The storage life of these tubes is usually limited, and it is necessary to ensure that out of date tubes do not remain available for use. J.8.6 General precautions Vapour detection is a means of measuring vapour concentrations, and great care is necessary to ensure that the readings are accurate, especially when the lives of personnel depend upon them. The following precautions should be observed: • the maker's handbook should be studied before calibration or use; • zero points should be checked regularly and reset if necessary before an instrument is calibrated. Great care should be taken when the zero is being set to ensure that the sample is free from any gas that would otherwise give a reading: .pure nitrogen should be used if necessary; • the instrument should be calibrated as often as recommended by the makers. The concentration and composition of the gas used for calibration (known as span gas) should be accurately known. Re-calibration should be recorded on or near the instrument; • the same precautions must be observed when handling span gas which is toxic or flammable as would apply if the chemical was carried as cargo; • tubes or liquids for equipment using the chemical absorption or reaction principles have a limited life with an expiry date. They should be replaced before expiry, otherwise readings may be inaccurate; • all sample lines should be clean, unobstructed, leak-tight and connected to the correct point; • all sample lines should be made of the correct material as specified by the maker. Incorrect tubing may absorb gas from the sample and cause misleading readings; • if upper or lower sample points are provided (for lighter than air or heavier than air vapours respectively) the correct position should be used for the cargo; • pumps, filters, flame screens and other components of the system should be well maintained to ensure accurate readings; • for fixed instruments, remote and local read-outs should be compared to detect discrepancies;
• performance of most fixed instruments depends on flow rate, and fluctuations can cause inaccuracy. Flows should be kept steady, and flows from separate points should be balanced; • the battery voltage of portable instruments should be checked frequently to ensure an instrument will provide accurate readings. J.9 AIR SUPPLY TO INSTRUMENTS AND CONTROLS The performance of instruments and control systems that depend upon a supply of clean, dry air can be degraded very quickly if the air supply is degraded or depleted. Water is a common contaminant which can give rise to corrosion and equipment malfunction. Lubricating oil can also cause problems. Both should be drained off regularly. Air supply pipes should be leak-tight, and filters and dryers should be checked frequently.
CARGO HOSES K.1 Introduction K.2 Certification, Marking and Testing K.3 Cargo Compatibility K.4 Handling, Connection and Use K.5 Ship/Shore Insulation, Earthing and Bonding K.6 Storage and Maintenance K.7 Example Format for Cargo Hose Form
CARGO HOSES K.1 INTRODUCTION
A modern cargo hose represents skilled engineering and, unless wrongly used, can be relied upon to contain the cargo. Nevertheless, it should always be treated as the weakest link in the cargo containment and transfer system, so correct handling and use of hoses is important. Use and handling may differ from type to type of hose, or by manufacturer. The types of hoses normally encountered are either metallic, composite, FTFE (polytetrafluorethylene) or polypropylene. A ship's own cargo hoses are frequently used on board chemical tankers, during loading and discharge of cargo at a terminal, during cargo transfers between ships and during tank cleaning. A ship should have on board appropriate manufacturers' material describing the hoses carried, and specifying any limitations in their use. K.2 CERTIFICATION, MARKING AND TESTING A ship's own cargo hoses must be tested and certified as required. The minimum requirements for the construction and testing of ships' cargo hoses are specified in the IMO Codes. All cargo hoses are required to be designed for a bursting pressure not less than 5 times the maximum pressure that the hose will be subjected to during cargo transfer operations. New lengths of cargo hose, before being placed in service, should be hydrostatically tested at ambient temperatures to a pressure not less than VA times its specified maximum working pressure, but not more than two fifths of its bursting pressure. A manufacturer's test certificate will provide information about the hose's construction method, its performance range and its nominal sizes. While in service, hoses should regularly be visually inspected, and they should be pressure tested at least annually. Test results should be recorded in a cargo hose condition log book. An example format for such a log is given in Section K.7. Cargo hoses are required to be marked with their specified maximum working pressure, which should not be less than 10 bar gauge. Hoses used in the transfer of cargoes at other than ambient temperature should be marked with the applicable minimum and maximum service temperature range. K.3 CARGO COMPATIBILITY Hoses used for the transfer of chemical liquids and vapours during cargo handling operations should be compatible with the nature and temperature of the chemical. Any limitations of the cargo properties and temperatures listed by the hose manufacturer should always be observed.
K.4 HANDLING, CONNECTION AND USE When a hose is being moved about the ship it should always be lifted and carried. It should not be dragged over the ship's fittings such as pipework or walkways, or rolled in a manner that twists the body of the hose, nor hoisted on a crane or derrick using a single wire strop
about its mid-length. Hoses should not be allowed to come into contact with hot surfaces such as steam pipes. Before connection, cargo hoses should be examined for any possible defects that may be visible inside the hose or on the outer covering. These may include signs of blistering, abrasion, flattening or evidence of leaks. Hoses with any damage should be assessed and a positive decision made on whether they can continue to be used safely. Seriously damaged or leaking hoses should not be used. Gaskets used between hoses and at the ship's manifold should be checked for suitability before use. Flanges on both the hose and manifold should be checked for cleanliness and good condition. Bolts and nuts used should be of the correct size and material, with a bolt fitted to every hole in the flange and tightened correctly. When in use, a cargo hose should be properly supported along its length to avoid excessive bending of the hose or its weight hanging from the manifold connection. This is especially important when significant tidal or draught variations can cause the relative heights of the ship and shore manifolds to alter a great deal, and the hose support to require frequent adjustment. Fendering, stools or chocks can be used to provide support under the hose, particularly at the manifold and at the shipside rail. When a hose is supported from above, bridles and saddles should be used to spread the load, and may require more than one supporting point. A single wire strop should not be used to support a cargo hose near its mid-length. Protection should be provided at points along the hose where chafing or rubbing could occur. Hoses should not be subjected to pumping pressures that exceed the rated working pressure. If this happens, the hose should be replaced by another, and retested before any further use. After use, hoses should be depressurised and drained before disconnection. K.5 SHIP/SHORE INSULATION, EARTHING AND BONDING It is essential that the cargo hose does not provide the primary path for static electricity between the ship and the jetty, otherwise there is a possibility of a static electricity discharge at the manifold when offering up the hose for connection or when breaking the connection after the cargo transfer. The necessary electrical discontinuity should be achieved with an insulating flange or a single length of non-conducting hose in the hose string between the ship and the shore. For a full explanation see Section 2.11 and Appendix D. K.6 STORAGE AND MAINTENANCE After they have been used for cargo transfer, hoses should be washed out, drained and dried. They should be stored horizontally on solid supports. If hoses are stored in the open, they should be protected from direct sunlight. No attempt should be made on board to repair damaged or leaking hoses.
K.7 EXAMPLE FORMAT FOR CARGO HOSE FORM
Cargo Hose Record Name of ship IMO number Hose identification Maximum working pressure
(This should be stencilled or marked on the hose)
Maximum and minimum working temperatures
(These should he stencilled or marked on the hose)
Suitable for cargoes of
(Any limitations on use, or in its chemical resistance, should be marked on the hose)
Test pressure and procedure
(This should give the method of pressurization and the method of inspection - e.g. measure extension or visually examine for leaks, and any precautions to be taken)
Date of test
SHIP/SHORE SAFETY CHECKLIST Introduction Ship/Shore Safety Checklist Guidelines for Completing the Ship/Shore Safety Checklist
SHIP/SHORE SAFETY CHECKLIST This appendix comprises the Ship/Shore Safety Checklist (Parts A & B), a joint declaration and guidelines relating to completion. INTRODUCTION Before liquid dangerous substances in bulk are pumped into or out of any ship/ or into a shore installation, the master of the ship and the berth operator should: • agree in writing on the handling procedures including the maximum loading or unloading rates; • complete and sign, as appropriate, the Ship/Shore Safety Checklist, showing the main safety precautions to be taken before and during such handling operations; • agree in writing on the action to be taken in the event of an emergency during handling operations. While the Ship/Shore Safety Checklist has been developed with cargo handling operations in mind, it is recommended that the same mutual examination, using the Checklist as appropriate, be carried out when a tanker presents itself at a berth for tank cleaning after carriage of liquid dangerous substances in bulk. The following guidelines have been produced to assist berth operators and ship masters in their joint use of the Ship/Shore Safety Checklist. The Mutual Safety Examination A tanker presenting itself to a loading or discharging terminal needs to check its own preparations and its fitness for the safety of the intended cargo operation. Additionally, the master of a ship has a responsibility to assure himself that the terminal operator has likewise made proper preparations for the safe operation of his terminal. Similarly, the terminal needs to check its own preparations and to be assured that the tanker has carried out its checks and has made appropriate arrangements. The Ship/Shore Safety Checklist, by its questions and requirements for exchange of written agreements for certain procedures, should be considered a minimum basis for the essential considerations which should be included in such a mutual examination. Some of the Checklist questions are directed to considerations for which the ship has primary responsibility, while others apply to both ship and terminal. All items lying within the responsibility of the tanker should be checked personally by the tanker's representative and similarly all items which are the responsibility of the terminal should be checked personally by the terminal's representative. However, in carrying out their full responsibilities both representatives should, by questioning the other, by sighting of records and, where felt appropriate, by joint visual inspection assure themselves that the standards of safety on both sides of the operation are fully acceptable. The joint declaration should not be signed until such mutual assurance is achieved. Thus all applicable questions should result in an affirmative mark in the boxes provided. If a difference of opinion arises on the adequacy of any arrangements made or conditions found, the operation should not be started until measures taken are jointly accepted.
A negative answer to the questions coded T' on the Checklist does not necessarily mean that the intended operation cannot be carried out. In such cases, however, permission to proceed should be obtained from the port authority. Items coded 'R' should be re-checked at intervals not exceeding that agreed in the declaration. Where an item is agreed to be not applicable to the ship, to the terminal or to the operation envisaged, a note to that effect should be entered in the 'Remarks' column. Variation of Conditions The conditions under which the operation takes place may change during the process. The changes may be such that safety can no longer be regarded as guaranteed. The party noticing or causing the unsafe condition is under an obligation to take all necessary actions to re-establish safe conditions, which may include stopping the operation. The presence of the unsafe condition should be reported to the other party and, where necessary, co-operation with the other party should be sought. Tank Cleaning Activities The questions on tank cleaning are provided in the Checklist in order to inform the terminal and the port authority of the ship's intentions regarding these activities.
Ship/Shore Safety Checklist
Ship's Name:.............................................................................................................................................. Berth:....;................................................................. Port: ......................................................................... Date of Arrival:.................................................... Time of Arrival: ..................................................... Instructions for completion The safety of operations requires all questions to be answered affirmatively by clearly ticking (b) the appropriate box. If an affirmative answer is not possible, the reason should be given and agreement reached between the ship and the terminal on appropriate precautions to be taken. Where any question is considered to be not applicable, then a note to that effect should be inserted in the remarks column. A box in either or both of the columns 'Ship' and 'Terminal' indicates that checks should be carried out by the party concerned. The presence of the letters A, P or R in the column 'Code' indicates the following: A - Any referenced procedures and agreements should be in writing in the remarks column of this checklist or other mutually acceptable form. In either case, the signature of both parties should be required. P - In the case of a negative answer the operation should not be carried out without permission of the port authority. R - Items to be re-checked during the operation at intervals not exceeding that agreed in the declaration.
Part A Bulk Liquid General General 1 Is the ship securely moored?
2 Are emergency towing wires correctly positioned?
3 Is there safe access between ship and shore?
4 Is the ship ready to move under its own power?
5 Is there an effective deck watch in attendance on board and adequate supervision on the terminal and on the ship?
6 Is the agreed ship/shore communication system operative? 7 Has the emergency signal to be used by the ship and shore been explained and understood? 8 Have the procedures for cargo, bunker and ballast handling been agreed?
AR A AR
9 Have the hazards associated with toxic substances in the cargo being handled been identified and understood? 10 Has the emergency shutdown procedure been agreed?
11 Are fire hoses and fire fighting equipment on board and ashore positioned and ready for immediate use?
12. Are cargo and bunker hoses/arms in good condition, properly rigged and appropriate for the service intended? 13 Are scuppers effectively plugged and drip trays in position, both on board and ashore?
14 Are unused cargo and bunker connections properly secured with blank flanges fully bolted? 15 Are sea and overboard discharge valves, when not in use, closed and visibly secured? 16 Are all cargo and bunker tank lids closed? 17 Is the agreed tank venting system being used?
18 Has the operation of the PA/valves and/or high velocity vents been verified using the checklift facility, where fitted? 19 Are hand torches of an approved type? 20 Are portable VHF/UHF transceivers |of an approved type? 21 Are the ship's main radio transmitter aerials earthed and radars switched off? 22 Are electric cables to portable electrical equipment disconnected from power? 23 Are all external doors and ports in the accommodation closed?
24 Are window type air conditioning units disconnected? 25 Are air conditioning intakes which may permit the entry of cargo vapours closed? 26 Are the requirements for the use of galley equipment and other cooking appliances being observed?
Remarks Stop cargo Disconnect Unberth
at kts wind vel. at kts wind vel. at kts wind vel.
27 Are smoking regulations being observed?
28 Are naked light regulations being observed? 29 Is there provision for an emergency escape?
30 Are sufficient personnel on board and ashore to deal with an emergency? 31 Are adequate insulating means in place in the ship/shore connection? 32 Have measures been taken to ensure sufficient pumproom ventilation? 33 If the ship is capable of closed loading, have the requirements for closed operations been agreed? 34 Has a vapour return line been connected?
35 If a vapour return line is connected, have operating parameters been agreed? 36 Are ship emergency fire control plans located externally? If the ship is fitted with an inert gas (10) system which is to used, the following questions should be answered: 37 Is the inert gas system fully operational and in good working order? 38 Are deck seals or equivalent in good working order? 39 Are liquid levels in P/V breakers correct?
P R R
40 Have the fixed and portable oxygen analysers been calibrated and are they working properly? 41 Are fixed IG pressure and oxygen content recorders working? 42 Are all cargo tank atmospheres at positive pressure with an oxygen content of 8% or less by volume?
R R PR
43 Are all the individual tank IG valves (if fitted) correctly set and locked?
44 Are all the persons in charge of cargo operations aware that in the case of failure of the inert gas plant, discharge operations should cease and the terminal be advised?
A Are tank cleaning operations planned during the ship's stay alongside the shore installation?
B If so, have the port authority and terminal authority been informed?
Delete Yes or No as appropriate.
Part B Bulk Liquid Chemicals Chemicals
1 Is information available giving the necessary data for the safe handling of the cargo and, where applicable, is a manufacturer's inhibition certificate available? 2 Is sufficient and suitable protective equipment (including self-contained breathing apparatus) and protective clothing ready for immediate use? 3 Have counter measures in the event of accidental personal contact with the cargo been agreed? 4 Is the cargo handling rate compatible with the automatic shutdown system, if in use?
5 Are cargo system gauges and alarms correctly set and in good order? 6 Are portable vapour detection instruments readily available for the products to be handled? 7 Has information on fire fighting media and procedures been exchanged? 8 Are transfer hoses of a suitable material, resistant to the chemical action of the cargoes? 9 Is cargo handling being performed with permanent installed pipelines?
10 Where appropriate, have procedures been agreed for receiving nitrogen supplied from shore, either for inerting or purging ship's tanks or for line clearing into the ship?
JOINT DECLARATION Declaration We the undersigned have checked, where appropriate jointly, the items on this Checklist and have satisfied ourselves that the entries we have made are correct to the best of our knowledge. We have also made arrangements to carry out repetitive checks as necessary and agreed that those items with the letter 'R' in the column 'Code' should be re-checked at intervals not exceeding ______ hours. For Ship
Name:________________________Name:________________________ Rank:________________________Position:_______________________ Signature:_____________________Signature:_____________________ Date:______________________ Time:______________________
GUIDELINES FOR COMPLETING THE SHIP/SHORE SAFETY CHECKLIST
PART A BULK LIQUID GENERAL 1. Is the ship securely moored? In answering this question, due regard should be given to the need for adequate tendering arrangements. Ships should remain adequately secured in their moorings. Alongside piers or quays, ranging of the ship should be prevented by keeping all mooring lines taut: attention should be given to the movement of the ship caused by wind, currents, tides or passing ships and the operation in progress. Wire ropes and fiber ropes should not be used together in the same direction (i.e. breasts, springs, head or stern) because of the difference in their elastic properties. Once moored, ships fitted with automatic tension winches should not use such winches in the automatic mode. The wind velocity at which loading arms should be disconnected, cargo operations stopped or the vessel unberthed should be stated. Means should be provided to enable quick and safe release of the ship in case of an emergency. Irrespective of the mooring method used, the emergency release operation should be agreed, taking into account the possible risks involved. In ports where anchors are required to be used, special consideration should be given to this matter. Anchors not in use should be properly secured. 2. Are emergency towing wires correctly positioned? Emergency towing wires (fire wires) should be positioned both on the off-shore bow and quarter of the ship. At a buoy mooring, emergency towing wires should be positioned on the side opposite to the hose string. There are various methods for rigging emergency towing wires currently in use. Some terminals may require a particular method to be used and the ship should be advised accordingly. 3. Js there safe access between ship and shore? The access should be positioned as far away from the manifolds as practicable. The means of access to the ship should be safe and may consist of an appropriate gangway or accommodation ladder with a properly secured safety net fitted to it. Particular attention to safe access should be given where the difference in level between the point of access on the vessel and the jetty or quay is large or likely to become large. When terminal access facilities are not available and a ship's gangway is used, there should be an adequate landing area on the berth to provide the gangway with a sufficient clear run of space and so maintain safe and convenient access to the ship at all states of tide and changes in the ship's freeboard.
Near the access ashore, appropriate life-saving equipment should be provided by the terminal. A lifebuoy should be available on board the ship near the gangway or accommodation ladder. The access should be safely and properly illuminated during darkness. Persons who have no legitimate business on board, or who do not have the master's permission, should be refused access to the ship. The terminal should control access to the jetty or berth in agreement with the ship. 4. Is the ship ready to move under its own power? The ship should be able to move under its own power at short notice, unless permission to immobilise the ship has been granted by the port authority and the terminal manager. Certain conditions may have to be met for permission to be granted. , 5. Is there an effective deck watch in attendance on board and adequate supervision on the terminal and on the ship? The operation should be under constant control both on ship and shore. Supervision should be aimed at preventing the development of hazardous situations; if however such a situation arises, the controlling personnel should have adequate means available to take corrective action. The controlling personnel on ship and shore should maintain an effective communication with their respective supervisors. All personnel connected with the operations should be familiar with the dangers of the substances handled. 6. Is the agreed ship/shore communication system operative? Communication should be maintained in the most efficient way between the responsible officer on duty on the ship and the responsible person ashore. When telephones are used, the telephone both on board and ashore should be continuously manned by a person who can immediately contact his respective supervisor. Additionally, the supervisor should have a facility to override all calls. When RT/VHF systems are used the units should preferably be portable and carried by the supervisor or a person who can get in touch with his respective supervisor immediately. Where fixed systems are used the guidelines for telephones should apply. The selected system of communication, together with the necessary information on telephone numbers and/or channels to be used, should be recorded on the appropriate form. This form should be signed by both ship and shore representatives. The telephone and portable RT/VHF systems should comply with the appropriate safety requirements. 7. Has the emergency signal to be used by the ship and shore been explained and understood? The agreed signal to be used in the event of an emergency arising ashore or on board should be clearly understood by shore and ship personnel. 8. Have the procedures/or cargo, bunker and ballast handling been agreed? The procedures for the intended operation should be pre-planned. They should be discussed and agreed upon by the ship and shore representatives prior to the start of the operations. Agreed arrangements should be formally recorded and signed by both ship and terminal representatives. Any change in the agreed procedure that could affect the operation should be discussed by both parties and agreed upon. After agreement has been reached by both parties,
substantial changes should be recorded in writing as soon as possible and in sufficient time before the change in procedure takes place. In any case, the change should be recorded in writing within the working period of those supervisors on board and ashore who reached the agreement. The operations should be suspended and all deck and vent openings closed on the approach of an electrical storm. The properties of the substances handled, the equipment of ship and shore installation, the ability of the ship's crew and shore personnel to execute the necessary operations and to control the operations sufficiently are factors which should be taken into account when ascertaining the possibility of handling a number of substances concurrently. The manifold areas both on board and ashore should be safely and properly illuminated during darkness. The initial and maximum loading rates, topping off rates and normal stopping times should be agreed, having regard to: • the nature of the cargo to be handled; • the arrangement and capacity of the ship's cargo lines and gas venting systems; • the maximum allowable pressure and flow rate in the ship/shore hoses and loading arms; • precautions to avoid accumulation of static electricity; • any other flow control limitations. A formal record to this effect should be made as above. 9. Have the hazards associated with toxic substances in the cargo being handled been identified and understood? Many tanker cargoes contain components which are known to be hazardous to human health. In order to minimise the impact on personnel, information on cargo constituents should be available during the cargo transfer to enable proper precautions to be adopted. In addition, some port states require such information to be readily available during cargo transfer and in the event of an accidental spill. The information provided should identify the constituents by chemical name, name in common usage, UN number and the maximum concentration expressed as a percentage by volume. 10. Has the emergency shutdown procedure been agreed? An emergency shutdown procedure should be agreed between ship and shore, formally recorded and signed by both the ship and terminal representatives. The agreement should state the circumstances in which operations have to be stopped immediately. Due regard should be given to the possible introduction of dangers associated with the emergency shutdown procedure. 11. Are fire hoses and fire fighting equipment on board and ashore positioned and ready for immediate use? Fire fighting equipment both on board and ashore should be correctly positioned and ready for immediate use. Adequate units of fixed or portable equipment should be stationed to cover the ship's cargo deck and on the jetty. The ship and shore fire main systems should be pressurised, or be capable of being pressurised at short notice. Both ship and shore should ensure that their fire main systems can be interconnected in a quick and easy way, using the international shore fire connection if necessary.
12. Are cargo and bunker hoses/arms in good condition, properly rigged and appropriate/or the service intended? Hoses should be in a good condition and properly fitted and rigged so as to prevent strain and stress beyond design limitations. All flange connections should be fully bolted and any other types of connections should be properly secured. It should be ensured that the hoses/arms are constructed of a material suitable for the substance to be handled, taking into account its temperature and the maximum operating pressure. Cargo hoses should be properly marked and identifiable with regard to their suitability for the intended operation. 13. Are scuppers effectively plugged and drip trays in position, both on board and ashore? Where applicable all scuppers on board and drain holes ashore should be properly plugged during the operations. Accumulation of water should be drained off periodically. Both ship and jetty manifolds should ideally be provided with fixed drip trays; in their absence portable drip trays should be used. All drip trays should be emptied in an appropriate manner whenever necessary but always after completion of the specific operation. When only corrosive liquids or refrigerated gases are being handled, the scuppers may be kept open, provided that an ample supply of water is available at all times in the vicinity of the manifolds. 14. Are unused cargo and bunker connections properly secured with blank flanges fully bolted? Unused cargo and bunker line connections should be closed and blanked. Blank flanges should be fully bolted and other types of fittings, if used, properly secured. 15. Are sea and overboard discharge valves, when not in use, closed and visibly secured? Care should be taken to ensure that sea and overboard discharge valves are closed and visibly secured as an important pollution avoidance measure on ships where cargo lines and ballast systems are interconnected. Remote operating controls for such valves should be identified in order to avoid inadvertent opening. If appropriate, the security of the valves in question should be checked visually. 16. Are all cargo and bunker tank lids closed? Apart from the openings in use for tank venting (refer to question 17) all openings to cargo tanks should be closed and gas-tight. Correct cargo gauging procedures will control which ullaging and sampling points may be opened for the short periods necessary for ullaging and sampling. Closed ullaging and sampling systems should be used where required by international, national or local regulations and agreements. 17. Is the agreed tank venting system being used? Agreement should be reached, and recorded, as to the venting system for the operation, taking into account the nature of the cargo and international, national or local regulations and agreements. There are three basic systems for venting tanks: • open to atmosphere via open ullage ports, protected by suitable flame screens; • fixed venting systems (which includes inert gas systems); • to shore through other vapour collection systems.
18. Has the operation of the P/V valves and/or high velocity vents been verified using the checklift facility, where fitted? The operation of the P/V valves and/or high velocity vents should be checked using the testing facility provided by the manufacturer. Furthermore, it is imperative that whilst doing so, an adequate visual or other check is made to ensure that the checklift is actually operating the valve. On occasion a seized or stiff vent has caused the checklift drive pin to shear and the ship's personnel to assume, with disastrous consequences, that the vent was operational. 19. Are hand torches of an approved type? and 20. Are portable VHF/UHF transceivers of an approved type? Battery operated hand torches and VHF radio-telephone sets should be of a safe type which is approved by a competent authority. Ship/shore telephones should comply with the requirements for explosion proof construction except when placed in a safe space in the accommodation. VHF radio telephone sets may operate in the internationally agreed wave bands only. All such equipment should be well maintained. Damaged units, even though they may be capable of operation, should not be used. 21. Are the ship's main radio transmitter aerials earthed and radars switched off? The ship's main radio station should not be used during the ship's stay in port, except for receiving purposes. The main transmitting aerials should be disconnected and earthed. Satellite communications equipment may be used normally unless advised otherwise. The ship's radar installation should not be used unless the master, in consultation with the terminal manager, has established the conditions under which the installation may be used safely. 22. Are electric cables to portable electrical equipment disconnected from power? The use of portable electrical equipment on wandering leads should be prohibited in hazardous zones during cargo operations, and the equipment preferably removed from the hazardous zone. Telephone cables in use for the ship/shore communication system should preferably be routed outside the hazardous zone. Whenever this is not feasible, the cable should be so positioned and protected that no danger arises from its use. 23. Are all external doors and ports in the accommodation closed? External doors, windows and portholes in the accommodation should be closed during cargo operations. These doors should be clearly marked as being required to be closed during such operations, but at no time should they be locked. 24. Are window type air conditioning units disconnected? and 25. Are air conditioning intakes which may permit the entry of cargo vapours closed? Window type air conditioning units should be disconnected from their power supply. Air conditioning and ventilator intakes which are likely to draw in air from the cargo area should be closed. Air conditioning units which are located wholly within the accommodation and which do not draw in air from the outside may remain in operation. 26. Are the requirements for the use of galley equipment and other cooking appliances being observed? Open fire systems may be used in galleys whose construction, location and ventilation system provides protection against entry of flammable gases. In cases where the galley does not comply with the above, open fire systems may be used
provided the master, in consultation and agreement with the terminal representative, has ensured that precautions have been taken against the entry and accumulation of flammable gases. On ships with stem discharge lines which are in use, open fire systems in galley equipment should not be allowed unless the ship is constructed to permit their use in such circumstances. 27. Are smoking regulations being observed? Smoking on board the ship may only occur in places specified by the master in consultation with the terminal manager or his representative. No smoking is allowed on the jetty and the adjacent area except in buildings and places specified by the terminal manager in consultation with the master. Places which are directly accessible from the outside should not be designated as places where smoking is permitted. Buildings, places and rooms designated as areas where smoking is permitted should be clearly marked as such. 28. Are naked light regulations being observed? A naked light or open fire comprises the following: flame, spark formation, naked electric light or any surface with a temperature that is equal to or higher than the minimum ignition temperature of the products handled in the operation. The use of open fire on board the ship, and within a distance of 25 metres of the ship, should be prohibited, unless all applicable regulations have been met and agreement reached by the port authority, terminal manager and the master. This distance may have to be extended for ships of a specialised nature, such as gas tankers. 29. Js there provision/or an emergency escape? In addition to the means of access referred to in question 3, a safe and quick emergency escape route should be available both on board and ashore. On the ship it may consist of a lifeboat ready for immediate use, preferably at the after end of the ship. 30. Are sufficient personnel on board and ashore to deal with an emergency? At all times during the ship's stay at a terminal, a sufficient number of personnel should be present on board the ship and in the shore installation to deal with an emergency. 31. Are adequate insulating means in place in the ship/shore connection? Unless measures are taken to break the continuous electrical path between ship and shore pipework provided by the ship/shore hoses or metallic arms, stray electric currents, mainly from corrosion prevention systems, can cause electric sparks at the flange faces when hoses are being connected and disconnected. The passage of these currents is usually prevented by an insulating flange inserted at each jetty manifold outlet or incorporated in the construction of metallic arms. Alternatively, the electrical discontinuity may be provided by the inclusion of one length of electrically discontinuous hose in each hose string. It should be ascertained that the means of electrical discontinuity is in place and in good condition, and that it is not being by-passed by contact with an electrically conductive material. 32. Have measures been taken to ensure sufficient pumproom ventilation? Pumprooms should be mechanically ventilated and the ventilation system, which should maintain a safe atmosphere throughout the pumproom, should be kept running throughout the operation.
33. If the ship is capable of closed loading, have the requirements/or closed operations been agreed? It is a requirement of many terminals that when the ship is ballasting, loading and discharging, it operates without recourse to opening ullage and sighting ports. Such ships will require the means for closed monitoring of tank contents, either by a fixed gauging system or by using portable equipment passed through a vapour lock, and preferably backed up by an independent overfill alarm system. 34. Has a vapour return line been connected? If required, a vapour return line may have to be used to return flammable vapours from the cargo tanks to shore. 35. If a vapour return line is connected, have operating parameters been agreed? The maximum and minimum operating pressures and any other constraints associated with the operation of the vapour return system should be discussed and agreed by ship and shore personnel. 36. Are ship emergency fire control plans located externally? A set of fire control plans should be permanently stored in a prominently marked weathertight enclosure outside the deckhouse for the assistance of shoreside fire fighting personnel. A crew list should also be included in this enclosure. If the ship is fitted with an inert gas (IG) system which is to be used, the following questions should be answered. 37. Is the inert gas system fully operational and in good working order? The inert gas system should be in safe working condition with particular reference to all interlocking trips and associated alarms, deck seal, non-return valves, pressure regulating control system, main deck IG line pressure indicator, individual tank IG valves (when fitted) and deck P/V breaker. Individual tank IG valves (if fitted) should have easily identified and fully functioning open/close position indicators. 38. Are deck seals or equivalent in good working order? It is essential that the deck seal arrangements are in a safe condition. In particular, the water supply arrangements to the seals and the proper functioning of associated alarms should be checked. 39. Are liquid levels in P/V breakers correct? Checks should be made to ensure the liquid level in the P/V breaker complies with manufacturer's recommendations. 40. Have the fixed and portable oxygen analysers been calibrated and are they working properly? All fixed and portable oxygen analysers should be calibrated and checked as required by the company and/or manufacturer's instructions. The in-line oxygen analyser/recorder and sufficient portable oxygen analysers should be working properly. 41. Are fixed IG pressure and oxygen content recorders working? All recording equipment should be switched on and operating correctly.
42. Are all cargo tank atmospheres at positive pressure with an oxygen content of 8% or less by volume? Prior to commencement of cargo operations, each cargo tank atmosphere should be checked to verify an oxygen content of 8% or less by volume. Inerted cargo tanks should at all times be kept at a positive pressure. 43. Are all the individual tank IG valves (if fitted) correctly set and locked? For both loading and discharge operations it is normal and safe to keep all individual tank IG supply valves (if fitted) open in order to prevent inadvertent under or over pressurisation. In this mode of operation each tank pressure will be the same as the deck main IG pressure and thus the P/V breaker will act as a safety valve in case of excessive over or under pressure. If individual tank IG supply valves are closed for reasons of potential vapour contamination or de-pressurisation for gauging etc., then the status of the valve should be clearly indicated to all those involved in cargo operations. Each individual tank IG valve should be fitted with a locking device under the control of a responsible officer. Chemical tankers may be fitted with an alternative and equivalent means of control for isolating each tank. The status of such control means should be checked. 44. Are all the persons in charge of cargo operations aware that in the case of failure of the inert gas plant, discharge operations should cease, and the terminal be advised? In the case of failure of the IG plant, cargo discharge, de-ballasting and tank cleaning should cease and the terminal be advised. Under no circumstances should the ship's officers allow the atmosphere in any tank to fall below atmospheric pressure. Tank cleaning A. Are tank cleaning operations planned during the ship's stay alongside the shore installation? B. If so, have the port authority and terminal authority been informed? These questions are intended to inform the terminal and port authority of the ship's intention regarding tank cleaning activities. PART B BULK LIQUID CHEMICALS
1. Is information available giving the necessary data for the safe handling of the cargo and, where applicable, is a manufacturer's inhibition certificate available? Information on the product to be handled should be available on board the ship and ashore before and during the operation. This information should include: • a cargo stowage plan; • a full description of the physical and chemical properties, including reactivity, necessary for the safe containment of the cargo; • action to be taken in the event of spills or leaks; • counter measures in the event of accidental personal contact; • fire fighting procedures and fire fighting media; • procedures for cargo transfer, tank cleaning and gas freeing. When cargoes required to be stabilised or inhibited are to be handled, information about them should be exchanged between ship and terminal. 2. Is sufficient and suitable protective equipment (including self-contained breathing apparatus) and protective clothing ready for immediate use? Suitable protective equipment (including self-contained breathing apparatus and protective clothing), appropriate to the specific dangers of the product handled, should be readily available both on board and ashore in sufficient quantity for operational personnel.
3. Have counter measures in the event of accidental personal contact with the cargo been agreed? Sufficient and suitable means should be available to neutralise the effects and remove small quantities of spilled products. However, it is possible that unforeseen personal contact may occur. To limit the consequences, sufficient and suitable countermeasures should be taken. Information on how to handle such contact with regard to the special properties of the products should be studied and available for immediate use. A suitable safety shower and eye rinsing equipment should be fitted and ready for instant use in the immediate vicinity of places on board and ashore where operations regularly take place. Measures should be taken to ensure that the equipment is operable in all ambient conditions. 4. Is the cargo handling rate compatible with the automatic shutdown system, if in use? Automatic shutdown valves may be fitted on the ship and shore. The action of such valves is automatically initiated when a certain level is reached in the tank being loaded either on board or ashore. In cases where such systems are used, the cargo handling rate should be so adjusted that a pressure surge evolving from the automatic closure of any such valve does not exceed the safe working pressure of either the ship or shore pipeline system. Alternative means, such as a recirculation system and buffer tanks, may be fitted to relieve the pressure surge created. A written agreement should be made between the ship and shore supervisors indicating whether the cargo handling rate will be adjusted or alternative systems will be used. The safe handling rate should be noted in this agreement, and also in the formal record for cargo, bunker and ballast handling referred to in Part A, question 8. 5. Are cargo system gauges and alarms correctly set and in good order? Ship and shore cargo system gauges and alarms should be checked regularly to ensure they are in good working order. In cases where it is possible to set alarms to different levels, the alarm should be set to the required level. 6. Are portable vapour detection instruments readily available for the products to be handled? Equipment provided should be capable of measuring, as appropriate, flammable and/or toxic levels. Suitable equipment should be available to calibrate those instruments capable of measuring flammability, and any necessary calibration should be carried out before the cargo handling operation commences. 7. Has information on fire fighting media and procedures been exchanged? Information should be exchanged on the availability of fire fighting equipment and the procedures to be followed in the event of a fire on board or ashore. Special attention should be given to any products being handled which may be water-reactive or require specialised fire righting procedures. 8. Are transfer hoses of a suitable material, resistant to the chemical action of the cargoes? Each transfer hose should be indelibly marked to show the products for which it is suitable, its specified maximum working pressure, the test pressure and the most recent date of testing at this pressure and, if used at temperatures other than ambient, its maximum and minimum service temperatures.
9. Is cargo handling being performed with permanent installed pipelines? During cargo operations where the use of portable cargo lines on board or ashore is unavoidable, care should be taken to ensure that these lines are correctly positioned and assembled so that no additional danger exists from their use. Where necessary, the electrical continuity of these lines should be checked. Non-permanent cargo lines should be kept as short as possible. The use of non-permanent equipment inside tanks is not generally permitted unless the approval of the port authority has been obtained. 10. Where appropriate, have procedures been agreed for receiving nitrogen supplied from shore, either for inerting or purging ship's tanks, or for line clearing into the ship? Ship and shore should agree in writing on the inert gas supply, specifying the volume required and the flow rate in cubic metres per minute. The sequence of, operating valves before beginning the operation and after completion should be agreed, so that the ship remains in control of the flow. Attention should be given to the adequacy of open vents on a tank in order to avoid the possibility of overpressurisation. The tank pressure should be closely monitored throughout the operation. The ship's agreement should be sought when the terminal wishes to use compressed nitrogen or air as a propellant, either for a line scraper to clear shore lines into the ship or to press cargo out of shore containment. The ship should be informed of the pressure to be used and the possibility of receiving gas into the cargo tank.
EXAMPLE OF CARGO INFORMATION FORM (DATA SHEET)
EXAMPLE OF CARGO INFORMATION FORM (DATA SHEET)
This appendix contains a model form for provision of the essential safety information required by the ship's crew to deal successfully with emergency situations that may occur. There are mandatory provisions that must be complied with by the shipper, but the intent of this model form is to achieve safety. It is an IMO requirement for the shipper of a liquid chemical cargo in bulk to supply a data sheet to ensure that ships have the information necessary for safe containment of the cargo, and the emergency action that should be taken in case of fire, spills, leaks or personal contact with the liquid. In the case of cargoes that are stabilised or inhibited, the ship should have sufficient details of the stabiliser or the inhibitor, and its effectiveness. Those supplying the information should bear in mind that cargo related emergencies may occur when the ship is at sea as well as in port. It is therefore not sufficient to advise that the crew call the local fire brigade in case of fire, or send a casualty to hospital in case of personal contact. Realistic and helpful but succinct advice is needed. It is recognised that different manufacturers are likely to have different styles of presenting technical chemical data about a product, often associated with a defined market or trading region, and there is no intention of recommending a change in those styles. However, it should be a priority to present ships with the essential safety guidance in a uniform manner which the crew can refer to immediately in the event of an emergency. The layout of the model form may be found to provide a helpful guide.
Cargo Information Form or Data Sheet Name of Chemical
Colourless mobile liquid.
Sweet and pungent.
1234 MFAG Table: 678
The Main Hazards:
TOXIC, FLAMMABLE, CORROSIVE, REACTIVE
Synonyms alpha beta gamma delta
Emergency Procedures: Fire
Liquid in eye
Stop liquid flow. Fire fighters should wear breathing apparatus and full protective clothing. Poisonous gases are produced in fires. Extinguish with alcohol-resistant foam or water spray. Do not use water jet. Cool surrounding areas with water spray. Do not delay. Flood eye gently with clean fresh water, forcing eye open if necessary, for at least 15 minutes. Obtain medical advice or assistance as soon as possible.
Liquid on skin
Do not delay. Remove contaminated clothing. Flood affected area with water but do not rub affected area. Obtain medical advice or assistance as soon as possible.
Remove victim to fresh air. If breathing has stopped or is weak, give oxygen or (mouth to mouth/nose) resuscitation using separation device. Remove any contaminated clothing. Obtain medical advice or assistance as soon as possible.
Stop the flow. Avoid contact with liquid or vapour. Emergency team should wear breathing apparatus and full protective clothing. All other people should leave the area. Contain spillage and allow to evaporate. Inform port authorities or coastal state of spillage.
Cargo Information Form or Data Sheet continued Health Data: Effect of liquid:
Odour Threshold: 25 ppm TLV: 400ppm On eyes: Irritation, no permanent damage. On skin: Cooling effect due to rapid evaporation. Redness and irritation. No long term effect from accidental exposure. By skin absorption: Of no consequence. By ingestion: Moderate local irritation and coupling. May cause intoxication or loss of
Consciousness. Effect of vapour: On eyes: Irritation at high concentrations. No permanent damage. On skin: Nil. When inhaled: Acute effect - Irritation of throat, nose and mouth; possible nausea and confusion but recovery is usually complete and without permanent effects. High concentrations will result in unconsciousness. When inhaled: Chronic effect - May cause bronchitis after repeated exposures over many years. Fire and Explosion Data:
Flash point 55°C (132°F) Moderate hazard of fire, when exposed to heat or flame.
Conditions of Carriage:
Materials of Construction:
Notes and Special Requirements:
EXAMPLE OF AN INHIBITED CARGO CERTIFICATE
Inhibited Cargo Certificate Issued by (Name of shipper, manufacturer, refinery, etc.) Port
Terminal or berth
This is to certify that, on *this day (or date) SS/MV* loaded a cargo of into cargo tanks Nos The above cargo was inhibited on the (date) Inhibitor Name of inhibitor The inhibitor is/is not oxygen dependent* Concentration of inhibitor in cargo Duration of effectiveness of inhibitor Temperature limitation qualifying the inhibitor's effective lifetime Expected duration of the voyage Action to be taken if the duration of the voyage exceeds the expected life of the inhibitor
Cargo received on board Date
Port and berth . Master/Chief Officer
Shore inspector Items marked thus * delete as appropriate
EXAMPLE OF A HOT WORK PERMIT
Hot Work Permit This permit relates to any work involving temperature conditions which are likely to be of sufficient intensity to cause ignition of combustible gases, vapour or liquids in or adjacent to the area involved. Before completing this form, the guidance notes below and in Section 2.12 of this Guide should be referred to. This permit is valid
Location of hot work:
Has an enclosed space entry permit been issued? Yes / No Reason if “No”
Description of hot work:
Personnel carrying out hot work: Officer responsible for hot work: Officer responsible for safety: Guidance notes for hot work permit • Starting and finishing times must not exceed the authorised signatory or responsible officer 's working hours. • Accurate location of hot work to be given. • Description of hot work to include type of equipment to be used. Section 1. Applies to all hazardous work not involving naked flame or continuous spark production, and would include use of electrical equipment, use of air driven rotary equipment, sand or grit blasting, hammering and mechanical chipping and movement of equipment or materials over or near to machinery that is operating. Section 2. Applies to all hot work involving high temperatures, open flame, electric arc or continuous source of sparks, etc. This type of work includes but is not limited to welding, burning and grinding. Tests for the presence of combustible gas should be carried out immediately before commencement of hot work, after each break, and at frequent intervals as long as the work is in progress.
Hot Work Permit continued Section 1
1.1 Has the hot work area been checked with a combustible gas indicator for the presence of flammable vapours? Yes
No 1.2 Has the surrounding area been made safe?
No Section 2 2.1 Has the hot work area been checked with a combustible gas indicator for the presence of flammable vapours?
2.2 Has the equipment or pipeline been gas freed?
2.3 Has the equipment or pipeline been blanked?
2.4 Is the equipment or pipeline free of liquid?
2.5 Is the equipment isolated electrically?
2.6 Is the surrounding area safe?
2.7 Is additional fire protection available? 2.8 Special conditions or precautions:
In the circumstances, it is considered safe to proceed with this hot work. Master: Person in charge of hot work team: Section 3 The work has been completed, and all persons under my supervision, and all materials and equipment, have been withdrawn. Officer responsible for hot work: (time)
First copy for display at work site Second copy for ships records or terminal records
EXAMPLE OF AN ENCLOSED SPACE ENTRY PERMIT
Enclosed Space Entry Permit This permit relates to entry into any enclosed space as described in Chapter 3 Ship's Name Identification of Enclosed Space Reason for Entry This permit is valid
^ (time) (time)
Pre-Entry Preparations (To be completed by the master or responsible officer) 1. Has the space been isolated to prevent inadvertent contamination? 2. Has the space been cleaned where necessary? 3. Has the space been thoroughly ventilated? 4. Do pre-entry atmosphere tests meet required levels? Oxygen - 21% by volume ________________Hydrocarbon - Less than 1 % of LFL________ Toxic Gases___________ ppm (specify gas & TLV) ________________________________ 5. Will frequent atmosphere checks be made while the space is occupied? 6. Will the space be continuously ventilated during the period of entry and during work breaks? 7. Is adequate illumination provided? 8. Is rescue and resuscitation equipment prepared and ready for immediate use? 9. Will a trained person be in constant attendance at the entrance to the space? 10. Is the Officer of the Watch (bridge, engine room, or cargo control room) aware of the planned entry? 11. Has a means of communication between persons entering the space and those at the entrance been agreed and tested? 12. Are emergency and evacuation procedures established and understood? 13. Is there a system for recording who is in the space? 14. Have all persons entering the space been trained in enclosed space entry procedures, and in safety and emergency procedures? 15. Is the space marked as safe for entry? ENCLOSED SPACE ENTRY PERMITTED Signature of master or responsible officer
Signature of responsible person supervising entry
THIS PERMIT BECOMES INVALID IF VENTILATION OF THE SPACE IS INTERRUPTED OR IF ANY OF THE CONDITIONS NOTED IN THE CHECKLIST CHANGE