IC4_v1.3b

NEBOSH International Diploma in Occupational Health and Safety Please be advised that the course material is regularly reviewed and updated on the eLearning platform. SHEilds would would like to inform students downloading these printable notes and using these from which to study that we cannot ensure the accuracy subsequent to the date of printing. It is therefore important to access the eLearning environment regularly to ensure we can track your progress and to ensure you have the most up to date materials. Version 1.3b (25/11/2013)

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Element - IC4: Storage, Handling & Processing of Dangerous Substances. Substances. Learning outcomes. On completion of this element, candidates should be able to:

1. Outline the main physical and chemical characteristics of industrial chemical processes. 2. Outline the main principles principles of the safe storage, handling and transport of dangerous substances. 3. Outline the main main principles of the design design and use of of electrical systems and equipment equipment in adverse or hazardous environments. 4. Explain the need for emergency planning planning and the typical organisational arrangements needed for emergencies. Relevant Standard Standard:: 

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United Nations, Recommendations on the Transport of Dangerous Goods: Model Regulations, 14th edition, UN Publications, 2005. ISBN: 9211391067.

International Labour Office, Safety in the Use of Chemicals at Work, an ILO Code of Practice , ILO, 1993. ISBN: 9221080064.

Minimum hours of tuition 7 hours. ho urs.

1.0 - Main Physical & Chemical Characteristics of Industrial Chemical Processes.

In chemical reactions, the process will undoubtedly involve a change of energy. The rate of the change of energy in many ways relies on the temperature. As a rough guide, 10°C is enough to double the rate of the reaction. High pressure contained within systems is also another factor which relates to the accident. The buildup of pressure within the walls of tankers and containers must be considered, preferably at the design stage. Pressure release valves are a way of helping to keep the pressure to its operational best, but consideration must be given to the release of vapour built up in the vessel/tank i.e. not to be released in to the atmosphere. A catalyst as applied in this instance can be defined as:

"Something that makes a chemical reaction happen more quickly without itself being changed." This 'something' can be any agent, in either a small or large quantity, which - when added to the reaction - will cause the reaction to strengthen.

1.1 - Endothermic, exothermic and runaway reactions.

In Chemistry, an endothermic reaction is one in which the reactants have less energy than the products, and thus a net input of energy, usually in the form of heat, is required. Endothermic reactions are often described as reactions that "feel cold", and contrast with exothermic reactions in

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Element - IC4: Storage, Handling & Processing of Dangerous Substances. Substances. Learning outcomes. On completion of this element, candidates should be able to:

1. Outline the main physical and chemical characteristics of industrial chemical processes. 2. Outline the main principles principles of the safe storage, handling and transport of dangerous substances. 3. Outline the main main principles of the design design and use of of electrical systems and equipment equipment in adverse or hazardous environments. 4. Explain the need for emergency planning planning and the typical organisational arrangements needed for emergencies. Relevant Standard Standard:: 



United Nations, Recommendations on the Transport of Dangerous Goods: Model Regulations, 14th edition, UN Publications, 2005. ISBN: 9211391067.

International Labour Office, Safety in the Use of Chemicals at Work, an ILO Code of Practice , ILO, 1993. ISBN: 9221080064.

Minimum hours of tuition 7 hours. ho urs.

1.0 - Main Physical & Chemical Characteristics of Industrial Chemical Processes.

In chemical reactions, the process will undoubtedly involve a change of energy. The rate of the change of energy in many ways relies on the temperature. As a rough guide, 10°C is enough to double the rate of the reaction. High pressure contained within systems is also another factor which relates to the accident. The buildup of pressure within the walls of tankers and containers must be considered, preferably at the design stage. Pressure release valves are a way of helping to keep the pressure to its operational best, but consideration must be given to the release of vapour built up in the vessel/tank i.e. not to be released in to the atmosphere. A catalyst as applied in this instance can be defined as:

"Something that makes a chemical reaction happen more quickly without itself being changed." This 'something' can be any agent, in either a small or large quantity, which - when added to the reaction - will cause the reaction to strengthen.

1.1 - Endothermic, exothermic and runaway reactions.

In Chemistry, an endothermic reaction is one in which the reactants have less energy than the products, and thus a net input of energy, usually in the form of heat, is required. Endothermic reactions are often described as reactions that "feel cold", and contrast with exothermic reactions in

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which heat is released.  Although the process of bond-breaking bond-break ing amongst reactants in a chemical process requires an initial input of energy (the activation energy), in the case of an endothermic reaction, the energy released when bonds are formed to create reactants is less than that required to break the bonds in the products; bonding electrons in the products are therefore at a higher energy than the reactants. Heat energy from the the material surrounding the reactants is usually what breaks their bonds, so as heat energy is transferred from the surroundings to the reactants, the surroundings get colder. This is often summarised in a chemical equation as follows: Reactants + Energy → Products

Figure 1. Exothermic Reaction.

Figure 2. Endothermic Reaction. Reaction.

1.2 - Examples of endothermic processes.

Examples of endothermic processes:   

Melting ice cubes. Melting solid salts. Evaporating liquid water.

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     

Making an anhydrous salt from a hydrate. Forming a cation from an atom in the gas phase. Splitting a gas molecule. Separating ion pairs. Cooking an egg. Baking bread.

Examples of endothermic reactions:      

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Reactions within food when cooking. Respiration reaction. The polymerisation of ethene to polythene. The reduction of silver ions to silver. Electrolysis - energy is provided in the form of electricity. The mixing of barium hydroxide and ammonium thiocyanate causes a powerful endothermic reaction that causes the products to become so cold that the moisture from the air forms a layer of frost on the outer surface of the beaker. Reactions in an aqueous solution, where heat energy is transferred from the water to the reactants. In this way, the temperature of the solution falls.

1.3. - Examples of exothermic processes.       

Freezing water. Solidifying solid salts. Condensing water vapour. Making a hydrate from an anhydrous salt. Forming an anion from an atom in the gas phase.  Annihilation of matter E=mc2. Splitting of an atom.

1.4 - Thermal runaway.

 An exothermic reaction can lead to thermal runaway, which begins when the heat produced by the reaction exceeds the heat removed. The surplus heat raises the temperature of the reaction mass, which causes the rate of reaction to increase. This in turn accelerates the rate of heat production. An approximate rule of thumb suggests that reaction rate - and hence the rate of heat generation doubles with every 10°C rise in temperature. Thermal runaway can occur because, as the temperature increases, the rate at which heat is removed increases in a linear fashion but the rate at which heat is produced increases exponentially. Once control of the reaction is lost, temperature can rise rapidly, leaving little time for correction. The reaction vessel may be at risk from over-pressurisation due to violent boiling or rapid gas generation. The elevated temperatures may initiate secondary, more hazardous runaways or decompositions.

1.5 - Effects of thermal runaway.

 A runaway exothermic reaction can have a range of results, from the boiling over of the reaction mass to large increases in temperature and pressure that lead to an explosion. Such violence can cause SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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blast and missile damage. If flammable materials are released, fire or a secondary explosion may result. Hot liquors and toxic materials may contaminate the workplace or generate a toxic cloud that may spread off-site. There can be serious risk of injuries, even death, to plant operators, and the general public and the local environment may be harmed. At best, a runaway causes loss and disruption of production. At worst, it has the potential for a major accident, as the incidents at Seveso and Bhopal have shown.

1.6 - Effect of scale.

The scale on which you carry out a reaction can have a significant effect on the likelihood of runaway. The heat produced increases with the volume of the reaction mixture, whereas the heat removed depends on the surface area available for heat transfer. As scale and the ratio of volume to surface area increase, cooling may become inadequate. This has important implications for scale-up of processes from the laboratory to production. You should also consider it when modifying a process to increase the reaction quantities.

1.7 - Causes of incidents. An analysis of thermal runaways in the UK has indicated that incidents occur because of:    

Inadequate understanding of the processes of chemistry and thermochemistry. Inadequate design for heat removal. Inadequate control systems and safety systems. Inadequate operational procedures, including training.

1.8 - Methods of control of temperature and pressure. The following HSE leaflet gives good information which is li nked to the control of temperature and pressure: Introduction.

In the chemical industry there has been a number of major incidents in which loss of containment of a hazardous substances could not be isolated quickly enough. Installations which can cause this major type of incident should have emergency arrangements for the safe and effective shutdown of plant and equipment in a controlled manner. This information sheet considers the general principles of isolation of hazardous inventories to prevent or minimise loss of containment. It is aimed at designers and manager of chemical manufacturing and onshore oil processing operations. The advice given here in relevant when considering preventive and mitigation measures, mainly at a process plant, but also at storage tanks and long pipe runs containing hazardous substances and where there is potential to cause a major accident. It does not give detailed guidance on preventive measures for process control, pressure relief arrangements, or emergency shutdown systems in general. Measures taken to isolate inventories are part of a whole range of means available to manufacturers to ensure that they can take appropriate action in an emergency. Sites may well have different combinations of preventive and mitigation measures.

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Risk assessment.

Emergency isolation arrangements are not only needed at those sites subject to specify major hazards legislation. All operations of chemical plant capable of causing a major accident must carry out a risk assessment as required by the Management of Health and Safety at Work Regulations 1992. you must be able to demonstrate that you have adequate arrangements for preventing a major accident and for limiting the consequences of those which do occur. These include the means to stop or substantially reduce release rates by psychically isolating large inventories of hazardous substances. Manufactures should be able to demonstrate that they have considered a hierarchy of measures. ie inherent safety followed by measures to prevent, control and minimise the consequences of loss of containment incidents. Inherit safety and safe operation.

 Any active safety shutdown system or procedure should not be used to rectify or mitigate a potentially hazardous situation brought about by poor plant design. A major objective in the design of any plant should be to make the plants integrity safe, as far as possible by designing out the hazards, so reducing reliance on protective systems. At the initial design stage manufacturers should actively consider using, for example.    

 A safer and/or simpler process. Less hazardous materials. Reduced pressures and temperatures. Reduced inventories.

It is also important that such matters are reviewed regularly during the plants life, particularly if there is any change, for example introducing a new process or manufacturing system. Risks arising from the site operations should be controlled by good design and plant integrity and effective safety management systems. However, even following these principles, there may still be situations whee loss of containment of a dangerous substance could cause a major accident. Emergencies may be dealt with in a number of ways. The most appropriate measures should be determined by risk assessments. Emergency shutdown arrangements.

Emergency shutdown arrangements should provide protection against those potentially hazardous conditions remaining in the final plant deisgn and be considered as part of the formal process hazard review. The action of an emergency shutdown system should be to bring the plant to a safe state. You could do this by:  

Closing valves. Removing power from motors etc.

or it may be more complex involving:  

The venting of process systems simultaneously or in a predetermined sequence. Providing pressure, cooling systems. purging etc.

 All of these options will depend on the nature of the processes and foreseeable plant conditions. Isolation of hazardous inventories. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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in an emergency, rapid isolation of vessels or process plant is one of the most effective means of preventing loss of containment or limiting its size. The extent of isolation provision should be designed to ensure a safe process state and minimise loss of containment. Emergency isolation facilities and procedures for all significant inventories should be included in emergency plans. Giving information and training to operations and maintenance staff is important. Site personal should know the contents of the plan, included specific action they should take in an emergency. Systems for achieving emergency shutdown are given here. The range is not exhaustive. Manually operated valves.

Manual valve isolation may be acceptable in some cases where more rapid emergency isolation is not necessary for preventing a major accident. Manually operation valves should be readily accessible and clearly marked, consideration the difficult and confusing circumstances in which emergency shutdown will probably take place. You should not use them in situations where the operator effecting the isolation would be placed in any danger. This will be a major factor in deciding when to use remotely operated shut-off valves (ROSOVs). However , manual valves will often have been fitted mainly for maintenance work and might not provide the safest or most effective way of achieving emergency isolation. Any mitigation function need to be specifically recognised and separately considered. Automatic process trips or shutdown valves.

Valves which are activated by process measurement sensor and close automatically on detection of abnormal process or equipment conditions, such as increased pressure or temperature, normal function as part of a trip or shutdown systems. They can designed with an additional function in mind, IE a role in some circumstances in emergency isolation. However this needs careful consideration, as the valves may need to be capable of providing tight shut-off. Fire proofing may also be necessary to ensure they continue to function in emergency situations. Remotely operated shut-off valves.

Risks from a major accident hazard can be reduced more effectively by fitting pipework with ROSOVs which can be closed quickly in an emergency. They should be installed if a foreseeable release of a dangerous substance from a section of pipework or associated plant could cause a major accident and consequences could be significantly reduced by rapid isolation. Although ROSOVs are the preferred option other measures can demonstrate that they can give a similar level of protection. ROSOVs may be manually activated through push-buttons located at some distance from the valve. Leak detection may trigger an alarm, usually both on the plant and in the control room, to which the operator can respond by operating the ROSOVs and other systems as necessary. The advantages of manually activation include: 

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The valve of an operators assessment regarding the most appropriate measures for dealing with the leak, including isolation.  Avoidance of spurious trip.  Avoidance of the potential failure of an automatic device.

Manual activation should be justifiable and the location of push-buttons must not endanger the operator. They should be accessible and in a safe and suitable place in relation to the emergency which may occur. There should normally be at least two activation points, one of which should be in the plant area. The control room would normally be the best place. Activation points should be readily indefinable both on plant and in operating instructions. A more immediate response to potential danger can be provided ROSOVs which can be activated by a detection system (for example, detectors for toxic or flammable gas or smoke, situated around critical plant.)

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Advantages of such automatic activation include:   

Elimination of potential operator error. More rapid isolation. Reduction in calculated releases for risk assessment purposes and consequent off-site effects.

Facilities for the manual activation of ROSOVs should be provided as a back-up to automatic activation, which may result in a faster response in some circumstances, for example , on emergency escape route from plant. Design consideration for ROSOVs.

Emergency isolation systems should be planned to suit the plant system design and operating practices. ROSOVs may be needed at process vessels, pumps and other ancillary equipment and pipework, taking into account likely points of release such as equipment joints and fittings and rotating equipments for example pump seals. they should be installed as close as possible to the vessel or plant and be accessible for routine testing and maintenance. Generally, valve closure should be as quick as is possible bearing in mind system design limitations. On complex or interconnecting plant the location or ROSOVs requires careful considerations due to the potential for 'boxing-in' of inventories. This can lead to, for example, over pressurisation of the pipework at increased temperatures. the possible effects of spurious trips should also be considered.  A formal assessment such as a hazard and interoperability study (HAZOP) should consider these aspects. Generic assessment based on sound site standards for isolation and other mitigation measures is acceptable. However, it is important to recognise that release scenarios may be specific. ROSOV selection feature.

There are some important features to be considered in selecting an appropriate ROSOV. The valves should be: 

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Be classed as 'safety critical'  valves and be subject to appropriate inspection and maintenance requirements. Regular testing is required, especially where valve operation is infrequent. Companies should determine the frequency and nature of testing based on design and use. In the absence of this assessment, a minimum of three-monthly intervals is recommended. Only perform a dual function (IE control and emergency isolation) in special circumstances and their role in emergency isolation of inventories must be recognised and justified by design. Employ fail-safe principles. ROSOVs are generally configured to fail closed. Back-up power/air supplies should be provided if closure on failure of plant systems is not acceptable. Remain in the fail-safe position once operation until manually reset. Be protected against external hazards such as fires or explosions, where there major accident hazard is a fire or explosion risk, for example where the valve could e subject to flame impingement.

1.9 - Mechanical and systems failures to major accidents. Flixborough.

 At 4.53 pm on 1st June 1974, there was an explosion at a chemical factory owned by Nypro (UK) Ltd at Flixborough in Lincolnshire. It was equivalent to about 15 tons of TNT; 26 employees were killed and 36 injured. There were 53 reported injuries to people outside the plant and many unreported. Smoke rose to a height of over 6,000 ft (1,800 m) so aircraft had to be diverted; some debris was found 12 miles (19.3 km) away and many fires were started within a radius of 3 miles. The 60-acre site was devastated, together with over 2,000 houses, factories and shops around the plant. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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The plant oxidised cyclohexane which, when heated to 155°C at a pressure of 126 psi (8.8 bar) produced caprolactam, a substance used in the manufacture of nylon. According to the chemical inventory, the plant stored large quantities of benzene, toluene, naptha and gasoline, all of which are very highly flammable materials. The process consisted of six reactors in series, containing a total of 120 tons of cyclohexane and a small amount of cyclohexanone. The final reactor in the process contained 94 per cent cyclohexane. There was a massive leak followed by a large unconfined vapour cloud explosion and fire. It was estimated that 30 tons of cyclohexane was involved in the explosion. The accident occurred on Saturday; on a working day, casualties would have been much higher; estimates of five hundred have been put forward. The chain of six reactors (retorts), each lined with stainless steel, were linked to each other by a 28 inch (711 mm) diameter pipe, and there was a set of bellows at each end of the pipe to allow for expansion. No. 5 retort had developed a 6 ft (1.8 m) crack and in order to take it out of use, a bypass pipe 20 inch (508 mm) in diameter had been fitted between Nos. 4 and 6 retorts. As each retort was 14 inches (350 mm) below the next, a 'dog's hind leg' had to be welded into the pipe; this pipe was fabricated from material on the site and not from the same material as specified by the original manufacturers. The use of expansion joints (bellows, in this case), which were improperly installed, may have been a principal reason for the accident. This provides additional reasons not to use expansion joints (except in special exceptional circumstances). When re-commissioning the modified plant, it was considered that the working pressure on the pipe and bellows would have been 38 tons; a straight pipe would have withstood this pressure but the dog-leg did not. During the inquiry, it was observed that the post of Works Manager was vacant and that the other chemical engineers on site were not capable of solving engineering problems. The replacement pipe was not to the standards laid down in British Standards BS 3511:1971; also, the instructions as to how to fit the bellows had not been read. The chemical inventory exceeded the quantities allowed by the licence by 51 times. Several new metallurgical observations were made during the inquiry. First, that in the presence of zinc, stainless steel can become embrittled and suffers cracking when under heat and stress. Only small quantities of zinc are necessary and they could be found in the galvanised plating on walkways, sheets of galvanised iron and fittings; the zinc need only be near the stainless steel. When nitrates are added to the cooling water, it can cause nitrate stress corrosion in the steel of the reactors. A third observation was that stainless steel can produce creep cavitation when subjected to a small fierce fire, which can cause a fracture in a pipe within a matter of minutes. Causes of the accident :

The immediate cause was determined as failure of a pipe which was replacing a failed reactor, leading to the release of a large vapour cloud of cyclohexane that ignited. There were, however, many contributory factors: (a) The reactor failed without an adequate check on why (metallurgical failure). (b) The pipe was connected without an adequate check on its strength, and on inadequate supports. (c) Expansion joints (bellows) were used on each end of pipe in a dog-leg without adequate support,

contrary to the recommendations of the manufacturer. (d) There was a large inventory of hot cyclohexane under pressure. (e) The accident occurred during start-up. (f) The control room was not built with adequate strength, and was poorly sited. (g) The previous works engineer had left and had not been replaced. According to the Flixborough SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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report, "there was no mechanical engineer on site of sufficient qualification, status or authority to deal with complex and novel engineering problems and insist on necessary measures being taken." (h) The plant did not have a sufficient complement of experienced people, and individuals tended to be overworked and liable to error. Management deficiencies:   

 A lack of experienced and qualified people. Inadequate procedures involving plant modifications. Regulations on pressure vessels that dealt mainly with steam and air and did not adequately address hazardous materials.

 A process with a very large amount of hot hydrocarbons u nder pressure and well above its flashpoint, installed in an area that could expose many people to a severe hazard. The cost of this disaster is estimated to have been in the order of £27 million for damage to the factory and £1.6m for the repair of shops and houses, at 1975 prices. It is a typical example of the causes and sub-causes all adding up to a major disaster. By coincidence, very shortly afterwards the Health and Safety at Work Act came into force.

1.10 - Hydrocracker Explosion and Fire, Grangemouth, 22nd March 1987.

Hydrocracking is an exothermic refinery process involving the breakdown of low-grade waxy products and thick viscous oils by subjecting them to hydrogen gas at high temperatures and pressures in the presence of a catalyst to form high-grade light oils, petroleum spirits and liquid petroleum gas (LPG). The hydrocracker unit at the refinery consisted of a series of four fixed-bed vertical reactors, operating in an atmosphere of hydrogen at 155 bar (2250 psig) and 350°C. Waxy distillates were continuously fed through the reactors. The temperatures of the reactor beds were monitored and at 425°C temperature cut-outs (TCOs) would operate to stop the input of wax feed and hydrogen. From the reactors, the hydrogenated liquid/gas mixture passed forward through a series of heat exchangers and a fin fan cooler into a vertical high-pressure separator (V305) at a temperature of about 50°C. In V305, the hydrogen and light gases were separated from the liquid and passed to the inlet of centrifugal compressor C301 to be recycled to the reactors. This compressor vibrated at high differential pressures and, although it gave reliable service, it was crucial to the operation of the plant so vibration was closely monitored to prevent breakdown. Events leading to the incident:

On 13th March, the hydrocracker unit was taken out of service for essential repairs. Late on Saturday 21st March, it was being recommissioned. At the start of the nightshift at 2200 hours, production was steady, but at about 0130 hours on Sunday, alarms sounded in the control room. The plant tripped and a number of pumps and compressors shut down automatically; feed to the reactors was interrupted and the system started to depressurise. One of the TCOs on V303 had caused the plant trip. The hydrocracker appeared satisfactory and the TCO was thought to be spurious. No overtemperature condition was found and the TCO trip was overridden, enabling hydrogen circulation to be re-established. The instrument section verified the reactor temperature control circuits, confirming that they were working. At about 0200 hours, the night shift operators started to bring the plant up to working pressure and to stabilise reactor bed temperatures preparatory to start up. From then until the time of the incident, the plant was being held on standby with no feed coming through. There was nothing of special note in the operation except for a slightly higher than usual vibration from C301. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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The incident:

 At 0700 hours, there was a violent explosion followed by an intense f ire. The explosion was heard and felt 30 km away. A contractor who had just left the mess room was killed. V306 had disintegrated and large fragments were projected considerable distances. Difficulties in fighting the fire arose because waxy material from ruptured pipework blocked drains, causing fire water to accumulate. Leaking petroleum spirit spread over a large area of the resultant water surface and five hours after the explosion, it ignited. A number of other process units in the hydrocracker complex were enveloped in flames. The potential consequences of the incident could have been much greater. It occurred on a Sunday morning when few people were on site. Investigation by HSE:

Initial fire and explosion evidence suggested there had been an explosive pressure vessel failure involving V306, followed by release of the gas and liquid contents as a cloud or mist. This produced not only a fireball but also blast effects due to the semi-confined nature of the plant. Operators denied taking action or making adjustments which could explain the incident. However, all the evidence suggested that valve LIC 3-22 had been opened and closed on manual control at least three times after the shift changeover at 0600 hours. Liquid level in V305 fell, and when LIC 3-22 was opened again just prior to the incident, all remaining liquid drained away, allowing high-pressure gas to break through. LIC 3-22 did not close automatically because its trip solenoid was disconnected. The investigation established that the pressure relief valve on V306 was not of sufficient capacity to relieve the maximum potential flow of high-pressure gas to prevent over-pressure. Also, too much reliance was placed on operators for the safe control of flow from high-pressure plant into a lowpressure system. The refinery had procedures for routine monitoring of interlocks, alarms and trips, but on the checklist for the hydrocracker, some were omitted. Preventative measures that could have been taken to avoid the incident: (a) V306 should have had a high-integrity automatic safety system to protect against gas

breakthrough and also pressure relief provision to cater for maximum anticipated gas flow rates. The safety shut-off system should have included a secondary shut-off valve in the line from V305, in addition to the control valves. Dual extra-low level detection should also have been fitted on V305 to provide independent shut-off trips. (b) The trip systems and alarms as installed should nevertheless have been connected and in full operational order. They should have been included in comprehensive testing schedules. Defects should have been reported, recorded and acted upon. (c) Changes to plant should only have been made after full consideration of the possible safety consequences. (d) Control room practices should have been monitored to detect possibilities for malpractice or error. Ergonomic factors in the design and layout of controls should have been periodically reassessed. (e) The problem of wax blockages in the level detection system on V305 and the associated smallbore pipework should have been fully analysed. Steps should have been taken to reduce the likelihood of blockage by, for example, the use of larger-bore pipework and monitored trace heating. The identification of blockages could have been assisted by dual-level detectors and more sophisticated-level instrumentation. (f) Wax blockages in the lines could have been prevented by lagging and trace heating. (g) A full analysis of the dangers and potential consequences inherent in the operation of the hydrocracker should have been carried out and documented. Adequate safeguards should have been provided and all concerned should have been made aware of the potential dangers and necessary

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precautions.

1.11 - Piper Alpha.

The Piper Alpha oil platform stood 100 feet above some of the fiercest waters in the North Sea. The accommodation block was designed to hold over 200 men, and gantries held aloft a burning torch, a symbol of the thousands of tons of oil it was pumping back to shore. Occidental Petroleum was getting around £3.5m a day from its operation. At its peak, Piper Alpha accounted for 10% of the UK's North Sea oil production. But in just a few hours on July 6th, 1988, the rig was reduced to a blackened, smoking stump. Most of it melted and fell into the sea. Of the 224 men on board, 165 died. Two crew members of a rescue boat were also killed. Thirty bodies were never recovered. The catastrophe shocked the oil industry into realising that the dangers on a rig like Piper Alpha were worse than they had possibly imagined. The public enquiry also made it clear that it was not an 'accident'. They held the Occidental management directly responsible for a series of preventable failings and errors. Bad communication and organisation of the paperwork allowed a pump to be turned on while it was in the process of being fixed. The sequence of events was: 

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 A permit had been issued to remove the safety valve on pump A. The jo b was unfinished and a blanking plate was fixed; the permit was returned to the supervisor but was subsequently lost. Pump B failed, and the supervisor cancelled a second permit for a maintenance shutdown on pump A. The cap on pump A blew, causing a gas explosion. The explosion was, experts say, survivable for most of the men, apart from the one or two who were probably killed instantly. But there were no blast walls around this area, just fire walls, and so an oil fire quickly took hold. The controls were knocked out and the rig shut down. Two other rigs feeding into the same oil export line did not shut down until one hour after the initial mayday, which meant oil from these rigs flowed back towards Piper and fuelled the fire. The fire escalated out of control. Gas pipelines ended in the area where the oil fire had started. They were eventually ruptured in the heat and the explosion engulfed the rig in thousands of tons of burning gas.

Occidental had known about this danger; it was highlighted 12 months earlier in a report. But no changes had been made and no protection was given to these vulnerable areas, which were a result of the rig having been converted to pump gas as well as oil.  A nearby rescue vessel was too slow to reach Piper Alpha. The thick black smoke prevented evacuation by helicopter from the helideck. Dozens of men were trapped in the accommodation block - the routes to the lifeboats were blocked, and there was no message over the public address system telling them what to do. The rig was falling to pieces in front of their eyes. Most stayed where they were until smoke and gas fumes overcame them. The only survivors disobeyed all their (minimal) training and jumped 100 feet into the sea. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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The rig melted in temperatures of 1,000°C. The only part to survive above water was the drilling platform (supposedly the most high-risk area). Lord Cullen's report concluded that Occidental had "adopted a superficial attitude" to safety. One expert on off-shore safety commented, "There is an awful sameness about these incidents. They are nearly always characterised by lack of forethought and lack of analysis, and nearly always the problem comes down to poor management." The accident was caused by lack of management control in design, procedures, training, communications; all these failures had existed for some time.

1.12 - Explosions And Fire At Allied Colloids - July 1992. Background.

 Allied Colloids at Bradford produces various speciality chemicals and is a top-tier major hazard site under the Control of Major Accident Hazards Regulations 1999 (COMAH). The layout of the raw materials warehouse (RMW) and surrounding area in July 1992 is shown in Figure 'Allied Colloids':

Figure 1. Ground Plan of 'Allied Colloids'.

To the east of the RMW were two external chemical drum storage areas known as X-Bay and J-Bay and the finished goods warehouse. To the south was the 'fire block' where drums of flammable liquids were stored. The RMW abutted the site boundary fence and was only 100 m from the nearest SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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housing. In one corner of the RMW were two fire-resisting storerooms known as the oxystores. These had block work walls. The roof consisted of PVC-coated galvanised sheet steel with a 60mm inner glass wool insulation lining. The joint between the block work walls and the underside of the roof was sealed by 1.5 m slabs of a low-density vermiculite-type fire insulation material. Both oxystores had louvered ventilation grilles in the rear wall to provide high and low-level ventilation. No. 2 oxystore was originally designed for frost-sensitive products so it had a steam heating system consisting of a six metre long radiant panel type heater installed at high level. This was supplied with steam at around 4 bar through a 40 mm line with an isolation valve and a 40 mm solenoid piston valve controlled by a flameproof thermostat mounted on the right-hand door pillar. The condensate return line was in 20 mm pipe and ran along the left-hand wall five metres above floor level, i.e. corresponding to a pallet load on the top shelf. During heater operation, the temperature of this unlagged pipe was calculated to be 90° +/- 5°C. Entry to No. 2 oxystore was through two independent roller-shutter doors, giving an aggregate fire resistance of six hours. The doors were designed for forklift truck entry; the inner door was normally left raised, thereby reducing the effective fire resistance to three hours. Neither of the doors had a fusible link closure device to automatically close them in the event of fire. In the main warehousing area of the RMW, there were a number of steam heater blower units. None of them were located in the oxystores. The Incident.

On 21st July 1992, No. 2 oxystore contained large amounts of AZDN (azodiisobutyronitrile), ammonium persulphate (APs) and sodium persulphate (SPs) plus nitrates and some other chemicals.  At 9 am, an order was received for four kegs of AZDN and se ven bags of SPS. The warehouseman fulfilled this order from the stocks in No. 2 oxystore and closed the roller-shutter door. Earlier it had been raining and the warehouse floor had become wet from movement of lift trucks. An electrician was asked to switch on the steam-heated blower heaters in the RMW. After looking at the control panel, he left, having failed to override the thermostat. Although the contractor for the heating system in No. 2 oxystore was in the same panel, the electrician said he had not touched it.  At around 1.30 pm a lift truck operator noticed 'white smoke ' coming from the lower vent of No. 2 oxystore, and set off the fire alarm. The internal fire team turned out, together with five senior managers, including the safety manager. A member of the fire team raised the electric roller-shutter door slightly and saw that two or three kegs of AZDN had ruptured, spilling their contents and creating a dust cloud.  After referring to the supplier's hazard datasheet for AZDN, a d ecision was made to use a type H vacuum cleaner for toxic dusts; there was a delay while confirmation was sought from the suppliers by telephone and a vacuum cleaner was obtained. At around 2.10 pm some employees in the office block saw 'white smoke' issuing from the ventilators at the rear of RMW - probably a further AZDN keg had ruptured and dust was leaking out.  Around 2.15 pm the shift chemist looked into the store t hrough the roller-shutter door and heard a loud hissing noise. A plume of smoke or vapour was coming from a bag of SPS located below the split  AZDN kegs. Before he could get a hose to douse it with water, the plume of vapour ignited, followed SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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by a flash and an explosion. An intense fire broke out in the storeroom, with thick black smoke. The fire spread rapidly to the remainder of the warehouse and external chemical drum storage. None of the company employees were injured but 33 people, including three residents and 30 fire or police officers were taken to hospital, primarily for smoke inhalation. 2,000 local residents were confined to their houses and residents in eight properties immediately adjacent to the raw materials warehouse were evacuated. Fire water run-off caused significant river pollution. The fire service finally stood down 18 days later, because of the on-going risk of re-ignition during the cleaning-up operations. HSE Investigation.

The oxystores were not being used solely for their original purpose. No. 1 oxystore contained not only organic peroxides (which possess oxidising properties and can undergo violent decomposition) but also VAZO 67, a flammable solid with similar properties to AZDN. No. 2 oxystore contained nearly 21 tons of persulphates, which are oxidising agents, stored together with 1.9 tons of AZDN, which is thermally unstable and can undergo violent decomposition at relatively low temperatures (the selfaccelerating decomposition temperature for a 25 kg package is 50°C). It is a flammable solid, and the ignition of a dispersion of the dust in air can result in an explosion. AZDN (and other flammable solids) and oxidising agents such as persulphates are incompatible and should not be stored together. Despite the original intention that X-Bay was intended for non-flammable materials, in practice it contained a large quantity of combustible materials in drums. The incident started when two or three kegs of AZDN ruptured. These were stored on the top shelf of the racking, close to the steam condensate return line. A malfunction of the steam heating system or operator error probably caused the condensate pipe to be hot. If the AZDN had been stored separately from oxidising substances, it is unlikely that the incident would have developed further. Powder from the ruptured kegs was scattered over the lower shelves. Knives were used for quality control sampling and for removing outer shrink wrapping from bags of oxidising substances; persulphate may have spilled from inadequately resealed or accidentally-cut bags. AZDN in contact with persulphate is likely to have been ignited by impact, possibly from a lid from one of the damaged AZDN kegs falling onto a bag, or to the floor. A keg lid falling from the top shelf would create sufficient impact energy in theory to ignite the mixture.  After the ignition, there was probably a small dust explosion followed by a second, larger dust explosion. The roof was lifted and the fire transferred quickly to No. 1 oxystore where organic peroxide was stored with VAZO 67. This generated an extremely intense fire which rapidly spread, assisted by the open outer door of oxystore No. 2, the lack of a closure device on the inner roller-shutter door, and mixed dusts on ledges and wall tops that may have ignited, causing a linear spread of flame. No fire protection sprinklers were provided. Examination of the oxystore blockwork walls after the fire showed they had not been fully keyed into the building support pillars; in one place adjoining X-Bay, a sizeable area of infill wall section had fallen out. This and the presence of stored chemicals against the warehouse wall added to the rapid spread to X-Bay. Most of the materials on J-Bay were of low combustibility but a parked lorry loaded with n-butyl acetate (highly flammable) was ignited at an early stage which contributed to the fire spread to J-Bay. The main mechanism of fire spread was direct ignition, assisted by the strong wind and radiated heat. One feature of the fire was a slow-moving flaming river of molten chemicals originating from the RMW SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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and augmented by material from X and J-Bays, which flowed downhill towards the centre of the site. Conclusions. (a) The crucial error was the incorrect categorisation of AZDN and its storage with oxidising agents

with which it was chemically incompatible. The same mistake was made with VAZO 67. Although a written segregation policy for packaged chemicals existed, there was no record or plan of where chemicals with particular hazardous properties were stored. There was also a failure to implement HSE advice published in 1986, The storage of packaged dangerous substances, which contained guidance resulting from investigations of other major warehouse fires. (b) The identity of the logistics department was unrecognised in corporate policies. Job descriptions in

the department were incomplete and outdated, so it was impossible to appraise the performance of individual managers against them. The department was treated as a Cinderella in terms of health and safety resources for improvements. No system existed for monitoring safety performance in the logistics department, despite a general recognition that there were serious deficiencies in safety standards throughout the raw materials storage areas. Targets were not set for improved safety performance nor were action plans drawn up for health and safety improvements despite the recommendations of highly critical insurance company reports. (c) Steam heating pipes and panels in No. 2 oxystore were not effectively isolated from the steam

supply after the main purpose of the storeroom was changed from frost-sensitive flammable products. Positive action to provide suitable protected electrical equipment, temperature monitoring equipment and smoke detectors had not been taken. (d) Flawed as it was, the segregation policy for chemicals was not effectively implemented. -

Warehouse staff was unaware of the policy, and training and instruction did not cover the segregation of the incompatible chemicals. (e) 50 minutes elapsed after the initial rupturing of AZDN kegs, before the emergency services were

called. Although companies need their own facilities for dealing with minor incidents, spillages and leaks, it is important that if there is a risk of the incident getting out of hand, the emergency services are called without delay. (f) Allied Colloids had a siren, but there were delays in its sounding which meant that members of the

public were not alerted to the risk as soon as they could have been. The question also arose as to who should sound the siren; the emergency services took charge of managing the emergency but they did not have the authority to order the sounding of the siren. The siren operated for about 50 minutes, until power to the site was cut off. (g) During and after the fire, there was considerable debate about the toxicity of the smoke, and a lack

of accurate advice for residents, farmers and others directly affected. (h) Tens of millions of litres of water were needed to extinguish the fire, and this mixed with chemicals

released from ruptured containers. Most of the contaminated run-off found its way into water courses causing serious environmental effects. (j) Concern was expressed by emergency authorities and members of the public about the SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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consequent congestion of the site, together with the danger of escalation if the fire had spread to production facilities and chemical storage areas.

1.13 - Fire At Hickson & Welch - September 1992.

Hickson & Welch in Castleford, West Yorkshire manufactures organic chemicals. Nitrotoluene production is carried out in one area of the site, in plants called Meissner I and II, which face a control building and the main office block.  At the time of the incident a process vessel known as '60 still base', used to distil an organ ic liquid in batches, was being raked out to remove an accumulation of semi-solid sludge (see Figure 12.4):

Figure 1. 60 Still Base.

Before raking, heat was applied for about three hours to the residues through an internal steam coil. This started an exothermic runaway reaction in the sludge leading to deflagration and a jet flame. The flame cut through the nearby control building, killing two people immediately and fatally injuring two more. It then struck the four-storey office block, shattering windows and setting rooms on fire. All the employees in this building managed to escape except for one, who was overcome by smoke in a second floor toilet; she died later. The HSE drew the following conclusions from this investigation: 

The accident arose following an attempt to remove accumulated sludge in a still base. This sludge, which was heated to make it soft, was thought to be affecting the efficiency of the

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plant. Materials processed in the vessel were known to be highly energetic but no attempt was made to monitor residue accumulation. The view of the management was that the level of residue in the still base ebbed and flowed with successive distillations. On 21st September 1992, the Area Manager (AM) authorised removal of sludge from 60 still base without any attempt to identify this material or the hazards involved. The residue contained organic nitrocompounds; it is well-known that these can undergo exothermic decomposition at elevated temperatur es, leading to thermal runaway. Several days before the accident, 60 still base was used to vacuum out a thick residue from two whizzer oil storages. This operation was not authorised at an appropriate level by management. Transfer of material from the still base into a waste tank proved difficult after the vacuuming operation, which was then followed by two batch distillations that were completed by 20 September. 60 still base had not been opened for cleaning in the previous 30 years and operating procedures for the plant were old. They had not been revised following a process change in 1988, and they made no reference to maintenance and clean-out. Formal cleaning procedures requiring water jetting were available for other still bases used at the factory. Preparatory work for removal of residue from 60 still base was authorised by newly-designated team leaders following a brief discussion with their AM. He authorised application of heat through the bottom steam battery without previously checking that the temperature of this residue could be monitored. He assumed that the still base thermometer probe would record its temperature but was not aware of the limitations of this system for that purpose. The issue of permits for the activities that followed involved a team leader who had recently been relocated back to the Meissner plant. He had not received refresher training but was allowed to authorise removal of the still base manlid and the fitting of a blanking plate using the company's permit-to-work procedure. The permits issued were not checked by the AM and a permit was not issued to cover the use of a metal tool for the raking out operation. Other elementary mistakes were made. The atmosphere inside the still base was not tested for flammable vapour and the sludge was not sampled and analysed. The fatal mistake was the application of heat through the bottom steam battery. The hazards were not assessed and the  job was not planned. The AM was dealing with several other problems which required his attention, and one of his manufacturing controllers was on holiday. The newly- appointed team leaders therefore assumed most of the responsibility for the task. The Meissner control building housed lockers, showers, offices and some control equipment. Its lightweight structure offered no protection from the heat and blast of the fire. Formal assessment of the risks to the building and those who used it from surrounding plant had never been carried out, and the possibility of exposure to a jet fire had not been foreseen. A limited amount of technical guidance is available to industry on this subject and can be used to form the basis for assessment of control building design and location. Examination of the means of escape from the main office building revealed breaches in the fire-resisting structure of a protected route on the second floor. These breaches above a false ceiling led to smoke-logging of the means of escape and probably caused smoke-logging in an adjacent toilet. Inspection following alterations, and regular monitoring of performance standards prescribed in the firm's fire certificate, should have been carried out to ensure that the integrity of escape routes was maintained. Furthermore, although the company had formal procedures to provide and record 'fire training' (required by their fire certificate) there was no written confirmation that the fifth fatality of a temporary office worker had been trained. In the confusion following the incident, and because many staff were absent for lunch, there were problems with carrying out roll calls at designated locations. Within 10 minutes of evacuating the office block, it was established that someone was missing. The fire officers entered the building with no idea of the casualty's likely location.

1.14 - Video: Buncefield.

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1.15 - Icmesa chemical company, Seveso, Italy. 10th July 1976. Accident summary.

The industrial plant was owned by the company ICMESA (Industrie Chimiche Meda Società  Azionaria), a subsidiary of Givaudan which in turn was a subsidiary of Hoffmann-La Ro che (Roche Group). The f actory building had been built many years earlier and it was not viewed by the local population as a potential source of danger.  At approximately 12:37 on Saturday 10th July 1976, a b ursting disc on a chemical reactor ruptured. Maintenance staff heard a whistling sound and a cloud of vapour was seen to issue from a vent on the roof. A dense white cloud of considerable altitude drifted offsite. The release lasted for some twenty minutes. About an hour after the release, the operators were able to admit cooling water to the reactor.  Among the substances of the white cloud released was a small deposit of 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD), a highly toxic material. The nearby town of Seveso, located 15 miles from Milan, had some 17,000 inhabitants. Over the next few days following the release, there was much confusion due to the lack of communication between the company and the authorities in dealing with this type of situation. No human deaths were attributed to TCDD but many individuals fell ill. A number of pregnant women who had been exposed to the release had abortions. In the contaminated area, many animals died. Failings in technical measures: 

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The production cycle was interrupted, without any agitation or cooling, allowing a prolonged holding of the reaction mass. Also, the conduct of the final batch involved a series of failures to adhere to the operating procedures. The original method of distillation patent specified that the charge was acidified before distillation. However, in the plant procedures, the order of these steps was reversed. Operating Procedures: Safe operating procedures. The bursting disc was set at 3.5 bar, and was to guard against excessive pressure in the compressed air that was used to transfer the materials to the reactor. Had a bursting disc with a lower set pressure been installed, venting would have occurred at a lower and less hazardous temperature. Relief Systems / Vent Systems: Venting of excessive pressures, sizing of vents for exothermic reactions The reactor control systems were inadequate both in terms of the measuring equipment for a number of fundamental parameters and also in the absence of any automatic control system. Control Systems: Sensors.  Alarms / Trips / Interlocks: Loss of cooling, agitator failure. The company was aware of the hazardous characteristics of the principal exotherm. However, studies showed that weaker exotherms existed that could lead to a runaway reaction. Reaction / Product Testing: Calorimetry methods, thermal stability. There was no device to collect or destroy the toxic materials as they vented. The manufacturer of the bursting disc recommended the use of a second receiver to recover toxic materials. No such vessel was fitted. Design Codes - Plant: Nature of hazardous releases. Secondary Containment: Catchpots. Information on the chemicals released and their associated hazards was not available from the company. Communication was poor and failed both between the company and the local authorities and within the regulatory authorities. Emergency Response / Spill Control: Safety management system, site emergency plan.

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On 9th December 1996, the EU passed Council Directive 96/82/EC on the control of major-accident hazards involving dangerous substances (as amended). This is a European Union law aimed at improving the safety of sites containing large quantities of dangerous substances. It is also known as the Seveso II Directive, after the Seveso disaster References.

Lees, F.P., 'Loss Prevention in the Process Industries - Hazard Identification, Assessment and Control', Volume 3, Appendix 3, Butterworth Heinemann, ISBN 0 7506 1547 8, 1996.

1.16 - Chernobyl - 26th April 1986. Chernobyl Accident: 

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The Chernobyl accident in 1986 was the result of a flawed reactor design that was operated with inadequately trained personnel and without proper regard for safety. The resulting steam explosion and fire released at least five percent of the radioactive reactor core into the atmosphere and downwind. 28 people died within four months from radiation or thermal burns, 19 have subsequently died, and there have been around nine deaths from thyroid cancer apparently due to the accident: total 56 fatalities as of 2004.  An authoritative UN report in 2000 concluded that there is no scientific evidence of any significant radiation-related health effects to most people exposed. This was confirmed in a very thorough 2005-06 study.

The April 1986 disaster at the Chernobyl nuclear power plant in the Ukraine was the product of a flawed Soviet reactor design coupled with serious mistakes made by the plant operators in the context of a system where training was minimal. It was a direct consequence of Cold War isolation and the resulting lack of any safety culture.

Figure 1. Chernobyl.

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Figure 2. Reactor Diagram. Reactor diagram.

The accident destroyed the Chernobyl-4 reactor and killed 30 people, including 28 from radiation exposure. A further 209 on site and involved with the clean-up were treated for acute radiation poisoning and among these, 134 cases were confirmed (all of whom apparently recovered). Nevertheless 19 of these subsequently died from effects attributable to the accident. Nobody off-site suffered from acute radiation effects. However, large areas of Belarus, Ukraine, Russia and beyond were contaminated in varying degrees. The Chernobyl disaster was a unique event and the only accident in the history of commercial nuclear power where radiation-related fatalities occurred.* However, its relevance to the rest of the nuclear industry outside the then Eastern Bloc is minimal. *There have been fatalities in military and research reactor contexts, e.g. Tokai-mura. The accident.

On 25th April, prior to a routine shut-down, the reactor crew at Chernobyl-4 began preparing for a test to determine how long turbines would spin and supply power following a loss of main electrical power supply. Similar tests had already been carried out at Chernobyl and other plants, despite the fact that these reactors were known to be very unstable at low power settings.  A series of operator actions, including the disabling of automatic shutdown mecha nisms, preceded the attempted test early on 26th April. As flow of coolant water diminished, power output increased. When the operator moved to shut down the reactor from its unstable condition arising from previous errors, a peculiarity of the design caused a dramatic power surge. The fuel elements ruptured and the resultant explosive force of steam lifted off the cover plate of the reactor, releasing fission products to the atmosphere. A second explosion threw out fragments of SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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burning fuel and graphite from the core and allowed air to rush in, causing the graphite moderator to burst into flames. There is some dispute among experts about the character of this second explosion. The graphite there was over 1200 tons of it - burned for nine days, causing the main release of radioactivity into the environment. A total of about 14 EBq (1018 Bq) of radioactivity was released, half of it being biologically-inert noble gases. Some 5000 tons of boron, dolomite, sand, clay and lead were dropped on to the burning core by helicopter in an effort to extinguish the blaze and limit the release of radioactive particles.

Figure 3. The Damaged Chernobyl Unit 4 Reactor Building. Immediate impact.

It is estimated that all of the xenon gas, about half of the iodine and caesium and at least 5% of the remaining radioactive material in the Chernobyl-4 reactor core (which had 192 tons of fuel) was released in the accident. Most of the released material was deposited close by as dust and debris , but the lighter material was carried by wind over the Ukraine, Belarus, Russia and to some extent over Scandinavia and Europe. The main casualties were among the firefighters, including those who attended the initial small fires on the roof of the turbine building. All these were put out in a few hours, but radiation doses on the first day were estimated to range up to 20,000 millisieverts (mSv), causing 28 deaths in the next four months and 19 subsequently. The next task was cleaning up the radioactivity at the site so that the remaining three reactors could be restarted, and the damaged reactor shielded more permanently. About 200,000 people ("liquidators") from all over the Soviet Union were involved in the recovery and clean up during 1986 and 1987. They received high doses of radiation, on average around 100 millisieverts. Some 20,000 of them received about 250 mSv and a few received 500 mSv. Later, the number of liquidators SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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swelled to over 600,000 but most of these received only low radiation doses. The highest doses were received by about 1000 emergency workers and on-site personnel during the first day of the accident. Initial radiation exposure in contaminated areas was due to short-lived iodine-131; later caesium-137 was the main hazard. (Both are fission products dispersed from the reactor core, with half lives of 8 days and 30 years respectively. 1.8 Ebq of I-131 & 0.085 Ebq of Cs-137 were released.) About five million people lived in areas contaminated (above 37 kBq/m2 Cs-137) and about 400,000 lived in more contaminated areas of strict control by authorities (above 555 kBq/m2 Cs-137). On 2nd-3rd May, some 45,000 residents were evacuated from within a 10 km radius of the plant, notably from the plant operators' town of Pripyat. On 4th May, all those living within a 30 kilometre radius - a further 116 000 people from the more contaminated area - were evacuated and later relocated. About 1,000 of these have since returned unofficially to live within the contaminated zone. Most of those evacuated received radiation doses of less than 50 mSv, although a few received 100 mSv or more. Reliable information about the accident and resulting contamination was not available to affected people for about two years following the accident. This led to distrust and confusion about health effects. In the years following the accident, a further 210,000 people were resettled into less contaminated areas, and the initial 30 km radius exclusion zone (2,800 km2) was modified and extended to cover 4,300 square kilometres. This resettlement was due to application of a criterion of 350 mSv projected lifetime radiation dose, though in fact radiation in most of the affected area (apart from half a square kilometre) fell rapidly so that average doses were less than 50% above normal background of 2.5 mSv/yr.

1.17 - Three Mile Island. Three Mile Island, 1979: 

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In 1979, a cooling malfunction caused part of the core to melt in the number 2 reactor at Three Mile Island in USA. The reactor was destroyed. Some radioactive gas was released a couple of days after the accident, but not enough to cause any dose above background levels to local residents. There were no injuries or adverse health effects from the accident.

The Three Mile Island power station is near Harrisburg, Pennsylvania in USA. It had two pressurised water reactors. One PWR was of 800 MWe and entered service in 1974. It remains one of the bestperforming units in USA. Unit 2 was of 900 MWe and almost brand new.

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The accident to unit 2 happened at 4 am on 28th March 1979 when the reactor was operating at 97% power. It involved a relatively minor malfunction in the secondary cooling circuit which caused the temperature in the primary coolant to rise. This in turn caused the reactor to shut down automatically. Shutdown took about one second. At this point a relief valve failed to close, but instrumentation did not reveal the fact, and so much of the primary coolant drained away that the residual decay heat in the reactor core was not removed. The core suffered severe damage as a result. The operators were unable to diagnose or respond properly to the unplanned automatic shutdown of the reactor. Deficient control room instrumentation and inadequate emergency response training proved to be root causes of the accident The chain of events.

Within seconds of the shutdown, the pilot-operated relief valve (PORV) on the reactor cooling system opened, as it was supposed to. About 10 seconds later, it should have closed. However, it remained open, leaking vital reactor coolant water to the reactor coolant drain tank. The operators believed the relief valve had shut because instruments showed them that a "close" signal was sent to the valve. However, they did not have an instrument indicating the valve's actual position. Responding to the loss of cooling water, high-pressure injection pumps automatically pushed replacement water into the reactor system. As water and steam escaped through the relief valve, cooling water surged into the pressuriser, raising the water level in it. (The pressuriser is a tank which is part of the primary reactor cooling system, maintaining proper pressure in the system. The relief valve is located on the pressuriser. In a PWR like TMI-2, water in the primary cooling system around the core is kept under very high pressure to keep it from boiling.) Operators responded by reducing the flow of replacement water. Their training told them that the pressuriser water level was the only dependable indication of the amount of cooling water in the system. Because the pressuriser level was increasing, they thought the reactor system was too full of water. Their training told them to do all they could to keep the pressuriser from filling with water. If it filled, they could not control pressure in the cooling system and it might rupture. Steam then formed in the reactor primary cooling system. Pumping a mixture of steam and water caused the reactor cooling pumps to vibrate. Because the severe vibrations could have damaged the pumps and made them unusable, operators shut down the pumps. This ended forced cooling of the reactor core. (The operators still believed the system was nearly full of water because the pressuriser level remained high.) However, as reactor coolant water boiled away, the reactor's fuel core was uncovered and became even hotter. The fuel rods were damaged and released radioactive material into the cooling water.  At 6:22 am, operators closed a block valve between the re lief valve and the pressuriser. This action stopped the loss of coolant water through the relief valve. However, superheated steam and gases blocked the flow of water through the core cooling system. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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Throughout the morning, operators attempted to force more water into the reactor system to condense steam bubbles that they believed were blocking the flow of cooling water. During the afternoon, operators attempted to decrease the pressure in the reactor system to allow a low pressure cooling system to be used and emergency water supplies to be put into the system. Cooling Restored.

By late afternoon, operators began high-pressure injection of water into the reactor cooling system to increase pressure and to collapse steam bubbles. By 7:50 pm on 28th March, they restored forced cooling of the reactor core when they were able to restart one reactor coolant pump. They had condensed steam so that the pump could run without severe vibrations. Radioactive gases from the reactor cooling system built up in the makeup tank in the auxiliary building. During March 29th and 30th, operators used a system of pipes and compressors to move the gas to waste gas decay tanks. The compressors leaked, and some radioactive gas was released to the environment. The Hydrogen Bubble.

When the reactor's core was uncovered, on the morning of 28th March, a high-temperature chemical reaction between water and the zircaloy metal tubes holding the nuclear fuel pellets had created hydrogen gas. On the afternoon of 28th March, a sudden rise in reactor building pressure shown by the control room instruments indicated a hydrogen burn had occurred. Hydrogen gas also gathered at the top of the reactor vessel. From 30th March to 1st April, operators removed this hydrogen gas "bubble" by periodically opening the vent valve on the reactor cooling system pressuriser. For a time, regulatory (NRC) officials believed the hydrogen bubble could explode, though such an explosion was never possible since there was not enough oxygen in the system. Cold Shutdown.

 After an anxious month, on 27th April operators established natural convection circulation of coolant. The reactor core was being cooled by the natural movement of water rather than by mechanical pumping. The plant was in "cold shutdown" The Clean-up.

The cleanup of the damaged nuclear reactor system at TMI-2 took nearly 12 years and cost approximately $973 million. The cleanup was uniquely challenging technically and radiologically. Plant surfaces had to be decontaminated. Water used and stored during the cleanup had to be processed.  And about 100 tons of damaged uranium fuel had to be removed from the reactor vessel -- all without hazard to cleanup workers or the public.  A cleanup plan was developed and carried out safely and successfully by a team of more than 1000 skilled workers. It began in August 1979, with the first shipments of accident-generated low-level radiological waste. In the cleanup's closing phases, in 1991, final measurements were taken of the fuel remaining in inaccessible parts of the reactor vessel. Approximately one percent of the fuel and debris remains in the vessel.  Also in 1991, the last remaining water was pumped from the TMI-2 reactor. The cleanup ended in December 1993, when Unit 2 received a licence from the NRC to enter Post Defuelling Monitored Storage (PDMS). SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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Early in the cleanup, Unit 2 was completely severed from any connection to TMI Unit 1. TMI-2 today is in long-term monitored storage. No further use of the nuclear part of the plant is anticipated. Ventilation and rainwater systems are monitored. Equipment necessary to keep the plant in safe longterm storage is maintained. Defuelling the TMI-2 reactor vessel was the heart of the cleanup. The damaged fuel remained underwater throughout the defuelling. In October 1985, after nearly six years of preparations, workers standing on a platform atop the reactor and manipulating long-handled tools began lifting the fuel into canisters that hung beneath the platform. In all, 342 fuel canisters were shipped safely for long-term storage at the Idaho National Laboratory, a programme that was completed in April 1990. TMI-2 cleanup operations produced over 10.6 megalitres of accident-generated water that was processed, stored and ultimately evaporated safely. In February 1991, the TMI-2 Cleanup Program was named by the National Society of Professional Engineers as one of the top engineering achievements in the U.S. completed during 1990.

1.18 - Bhopal, 3rd December 1984. Accident summary.

In the early hours of 3rd December 1984, a relief valve on a storage tank containing highly toxic methyl isocyanate (MIC) lifted. A cloud of MIC gas was released which drifted onto nearby housing. Prior to this, at 23.00 hrs on 2nd December, an operator noticed the pressure inside the storage tank to be higher than normal but not outside the working pressure of the tank. At the same time, a MIC leak was reported near the vent gas scrubber (VGS). At 00.15hrs, a MIC release in the process area was reported. The pressure inside the storage tank was rising rapidly so the operator went outside to the tank. Rumbling sounds were heard from the tank and a screeching noise from the safety valve. Radiated heat could also be felt from the tank.  Attempts were made to switch on the VGS but this was not in o perational mode.  Approximately 3,000 people died within a short period and t ens of thousands were injured, overwhelming the emergency services. This was further compounded by the fact that the hospitals were unaware as to which gas was involved or what its effects were. The exact numbers of dead and injured are uncertain, as people have continued to die of the effects over a period of years. It is believed that as many as 15,000 have died in the intervening years. The severity of this accident makes it the worst recorded within the chemical industry. In June 2010, eight former employees of Union Carbide's Indian facility were convicted of 'death by negligence' and were fined 100,000 rupees each. Warren Anderson, the CEO of Union Carbide at the time, absconded on bail shortly after the incident and has never been brought to trial. Failings in technical measures: 

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The flare system was a critical element within the plant's protection system. However, this fact was not recognised as it was out of commission for some three months prior to the accident. Plant Modification / Change Procedures: HAZOP, identification of safety critical elements. Hazards associated with runaway reactions in a chemical reactor are generally understood. However, such an occurrence within a storage tank had received little research.

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Reaction / Product Testing: Laboratory testing. The ingress of water caused an exothermic reaction with the process fluid. The exact point of ingress is uncertain, though poor modification/maintenance practices may have contributed. Design Codes - Plant: Ingress of unwanted material. Maintenance Procedures: Training and competence levels. Plant Modification / Change Procedures: HAZOP. The decommissioning of the refrigeration system was one plant modification that contributed to the accident. Without this system, the temperature within the tank was higher than the design temperature of 0°C. Plant Modification / Change Procedures: HAZOP, decommissioning procedures. The emergency response from the company to the incident and from the local authority suggests that the emergency plan was ineffective. During the emergency, operators hesitated over when to use the siren system. No information was available regarding the hazardous nature of MIC and what medical actions should be taken. Emergency Response / Spill Control: Site emergency plan, emergency operating procedures/training.

2.0 - Principles in the Safe Storage, Handling & Transport of Dangerous Substances.

Dangerous substances are any substances used or present at work that could, if not properly controlled, cause harm to people as a result of a fire or explosion. They can be found in nearly all workplaces and include such things as solvents, paints, varnishes, flammable gases such as liquid petroleum gas (LPG), dusts from machining and sanding operations and dusts from foodstuffs. Dangerous substance means:

1. A substance or preparation which meets the criteria in the approved classification and labelling guide for classification as a substance or preparation which is explosive, oxidising, extremely flammable, highly flammable or flammable, whether or not that substance or preparation is classified under the CHIP Regulations. 2. A substance or preparation which, because of its physicochemical or chemical properties and the way it is used or is present at the workplace, creates a risk, not being a substance or preparation falling within subparagraph (a) above. 3. Any dust, whether in the form of solid particles or fibrous materials or otherwise, which can form an explosive mixture with air or an explosive atmosphere, not being a substance or preparation falling within subparagraphs (a) or (b) above.

Figure 1. Explosive Atmosphere. Regulation 7 introduces a duty on the employer to identify areas within the workplace where explosive atmospheres will, or may, exist. These must be classified into zones, as per Schedule 2 of DSEAR and a suitable warning sign must be displayed (yellow warning triangle with EX in it).

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2.1 - The hazards presented and assessment of risk. The Risk assessment process is outlined in the Dangerous Substances and Explosive Atmosphere Regulations as: (1) Where a dangerous substance is, or is liable to be, present at the workplace, the employer shall

make a suitable and sufficient assessment of the risks to his employees which arise from that substance. (2) The risk assessment shall include consideration of: (a) The hazardous properties of the substance. (b) Information on safety provided by the supplier, including information contained in any relevant

safety data sheet. (c) The circumstances of the work including: (i) The work processes and substances used and their possible interactions. (ii) The amount of the substance involved. (iii) Where the work will involve more than one dangerous substance, the risk presented by such

substances in combination. (iv) The arrangements for the safe handling, storage and transport of dangerous substances and of

waste containing dangerous substances. (d) Activities, such as maintenance, where there is the potential for a high level of risk. (e) The effect of measures which have been or will be taken pursuant to these Regulations. (f) The likelihood that an explosive atmosphere will occur and its persistence. (g) The likelihood that ignition sources, including electrostatic discharges, will be present and become

active and effective. (h) The scale of the anticipated effects of a fire or an explosion. (i) Any places which are or can be connected via openings to places in which explosive atmospheres

may occur. (j) Such additional safety information as the employer may need in order to complete the risk

assessment. (3) The risk assessment shall be reviewed by the employer regularly so as to keep it up to date and

particularly if: (a) There is reason to suspect that the risk assessment is no longer valid. (b) There has been a significant change in the matters to which the risk assessment relates, including

when the workplace, work processes, or organisation of the work undergoes significant changes, extensions or conversions; and where, as a result of the review, changes to the risk assessment are required, those changes shall be made. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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(4) Where the employer employs five or more employees, the employer shall record the significant

findings of the risk assessment as soon as is practicable after that assessment is made, including in particular: (i) the measures which have been or will be taken by him pursuant to these Regulations; (ii) sufficient information to show that the workplace and work processes are designed, operated and

maintained with due regard for safety and that, in accordance with the Provision and Use of Work Equipment Regulations 1998 (a) adequate arrangements have been made for the safe use of work equipment; and (b) where an explosive atmosphere may occur at the workplace and subject to the transitional

provisions in regulation 17(1) to (3), sufficient information to show: (i) those places which have been classified into zones pursuant to regulation 7(1). (ii) equipment which is required for, or helps to ensure, the safe operation of equipment located in

places classified as hazardous pursuant to regulation 7(1). (iii) that any verification of overall explosion safety required by regulation (4) has been carried out. (iv) the aim of any coordination required by regulation 11 and the measures and procedures for

implementing it. (5) No new work activity involving a dangerous substance shall commence unless: (a) An assessment has been made. (b) The measures required by these Regulations have been implemented.

2.2 - Storage methods and bulk quantities. Storage Areas.

Storage areas should be separate from manufacturing, accommodation, public access, garages and equipment which may produce a fire hazard. When it is not practicable for the store to be outside, it should be carefully sited within the building, well away from evacuation routes. The stores should have at least two access points to allow a means of escape. The stores should be single-storey, made of non-combustible materials. There should be explosion panels, designed so that the panel will give and not the whole building; they may be in the roof of the store. Ventilation is important for both gases and fumes, which may be either lighter or heavier than air. Stores for flammable gases should, ideally, be of wire mesh so that air can circulate freely. The floor should be of concrete or some other impervious material so that moisture will drain away and not rust the containers. Security should also be considered; the sign of the skull and crossbones is a challenge to children, who may not realise that it means danger. Thus the doors, locks and hinges all need to be strong and intrusion-proof. If there has to be a window then, unless this is an escape route, it should be secure, may be of bulletproof glass or have bars across. In the entrance there should be a sill or ramp which will contain a spillage; this may cause problems with the access of vehicles. Doors and gates (solid or mesh) to storage areas should be shut whenever they are not required to SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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allow the passage of goods. They should also be locked when they are not in use. Consider whether solid or mesh doors should be used. Segregation:

Different types of goods (e.g. packets, drums, cylinders) should be in different areas. This is of particular importance where hazardous materials are stored, e.g. oxidising agents. Stacked goods - the following points are important when stacking materials:    

Keep the stacks as small as is practical. Keep stacks away from walls and off the floor by using pallets. Stacks should not be close to lights, alarm points, fire-fighting equipment or sprinklers. Stacks should not block drains or scuppers.

Housekeeping - the store should be inspected regularly. Waste and debris should not be allowed to accumulate. Good housekeeping involves:      

 A good management attitude and effective supervision. Cleanliness and tidiness; safe disposal of scrap and waste. Unobstructed access in the workplace.  Adequate space and proper layout. Fire and safety equipment in good condition. Planned maintenance.

 All electrical equipment within the area should be of a standard related to the risk (zoned).

2.3 - Guidelines for the storage and handling of drums and intermediate bulk containers.

The incorrect storage and improper management of containers which are designed to store various liquids can lead to incidents of pollution. These guidelines relate to containers whose maximum volume is no greater than 1000 litres. Specific liquids have additional guidelines with regard to their storage and handling. Container Volumes Covered by the Guidelines.

Standard containers may range in volume from a few litres up to 205 litres for drums and then up to 1000 litres. The term Intermediate Bulk Container (IBC) normally refers to a storage vessel with a volume of 1000 litres (1m3). It is envisaged that these containers are not permanently connected to a process or system and are frequently delivered on site and then removed when used, or for further distribution. Labelling of Containers and Storage Facilities.

The materials contained should be stored in accordance with all relevant legislation which includes Health and Safety guidelines. The containers must display the material stored. If the materials contained are hazardous, then they must be clearly labelled as such with the nature of the hazard displayed. Access to the storage facility or area should also display the hazards which the materials being stored may pose. Movement and Use of Containers.

The movement and use of containers storing hazardous substances must be assessed under the Control of Substances Hazardous to Health (COSHH) Regulations. These regulations require that an assessment of the health risks encountered by the employees when using the containers is made and any steps required to reduce these risks are taken. For example, the dispensing of the material contained may lead to minor leaks or spillages which the employee may come into contact with. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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 Another example may involve the use of heavy lifting machinery to move containers around a site. COSHH regulations require any potential risks identified to be dealt with so that they may be eliminated or reduced, with the required actions introduced should specific incidences take place.  A large proportion of incidents of pollution occur when containers a re being delivered or moved around site. It is these instances when drums or containers are most likely to be damaged or punctured, with their contents being released as a result. To minimise the likelihood of an incident of pollution, the delivery and storage areas for the containers should be designated and marked. These areas should be isolated from the surface water drainage system with the use of ramps, sleeping policemen, sumps and drainage shut-off valves to contain any spills. If at all possible, the delivery and storage areas should be covered to alleviate the problems of surface water drainage. The proper training and guidance should be used to ensure that the delivery, storage and movement of containers is carried out with the minimal risk of spills and leakage occurring. Drum carriers, drum taps and funnels should be used when transferring the contents of one container to another. Primary Containment Systems.

It is important to routinely check the integrity of the primary containers to ensure that they have not been damaged or show signs of wear and tear. Drums, if stored outside, can rust and the contents may become contaminated. Plastic containers can age and, if exposed to extreme temperatures, may become brittle and crack. For these reasons, if at all possible, the primary containers should be stored inside a building or protected from the elements. Secondary Containment Systems.

Secondary containment involves the installation and use of drip trays, kerbs and bunds which are designed to contain leaks and spillages should the primary containers fail. The design of the secondary containment facilities will depend on the materials being stored and the volumes contained. General guidelines suggest that the secondary containment facility should be capable of retaining 25% of the total volume of the containers being stored or 110% of the largest container being stored, whichever is the greater. For specific chemicals, greater volumes are recommended and in some instances required by law. Examples of these are chemicals such as pesticides and agrochemicals. It is therefore important to carefully check the specific containment requirements of the materials being stored. For large external stores which are open to the elements, 25% of the total volume may leave the containment walls very low and leaks may 'jet' over the containment walls and gain access to surface water drains. In these cases, additional freeboard is recommended or some form of resistant sheeting device to ensure that any jets are deflected safely back into the bund. Drip trays are normally prefabricated units designed to hold 25% of the containers volume. Secondary containment systems must be designed and built so that they will contain a spill of the material which they are designed to contain. With this in mind the material from which the containment system is constructed must be resistant to whatever is stored within it. Most external containment systems are formed from concrete. It is beneficial to design containment systems with a sloping floor and a sump where spillages and rainwater can be collected and removed. There should however be no permanent drainage outlet from the containment system. It is important to ensure that any proprietary systems which may be composed of plastics or metals are completely resistant to the materials placed within them. Monitoring and Inspection Procedures.

Containment systems should be monitored and regularly inspected to ensure their integrity. Bunds should be checked to ensure they are not full of rainwater and that drip trays are cleaned and emptied regularly with any liquids disposed of safely and correctly. Records of inspections and maintenance undertaken should be kept to ensure that any persistent problems are identified and can be dealt with quickly. Drums and Barrels.

These should be stored outside on an impervious surface (concrete) which is no closer than 4m to any risk, bund or open boundary. If the boundary is an imperforate wall of at least one hour's fire resistance, drums may be stored against it to within 1m of the top. This area should be ramped to SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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contain spills. No container should be stored within 2m of any door, plain glazed window, or escape route of a process building. The storage distances may be reduced if the liquids are stored in a fireresisting store. Small containers in work rooms may be stored, provided that:  

The total quantity does not exceed 50 litres. When not being used, they are kept in a store of non-combustible construction.

2.4 - Segregation requirements and access. When segregating stored dangerous substances, the following safety points should be borne in mind:  

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There must be a way allowing safe access and egress in the event of a fire or emergency. The idea of segregation is to keep incompatible chemicals apart in order to prevent their mixture. Prevention of different process areas becoming too close. Prevention of a rapid fire spread. Prevention of smoke and gases from escalating into a fire or explosion. Prevention of oxidising agents - so as to avoid the likelihood of explosions. Prevention of chemicals releasing their explosive properties when heated. Prevention of damage by physical properties such as fork-lift trucks and pallet trucks etc.

2.5 - Leakage and spillage containment.

 A variety of toxic and flammable chemicals are frequently stored and transported in dr ums and cylinders. Although individual containers hold relatively small inventories, a single cylinder of a compressed or liquefied toxic gas can present a significant hazard to personnel. Additionally, large quantities of drums and cylinders are often stored together, giving rise to potentially large inventories of hazardous materials. The movement and connection/disconnection of drums and cylinders to process plant requires the direct involvement of operating personnel, giving rise to the potential for human error to cause incidents. General principles. Storage location.

Both the hazards of the material and the size of the inventory need to be considered in determining where a store should be located. Considerations should include the distance from other stored materials, process plant, traffic routes and occupied buildings. Guidance on separation distances is provided in various HSE Codes of Practice such as HS(G)51 Storage of flammable liquids in containers and HS(G)40 Safe handling of chlorine from drums and cylinders. Where separation distances are inadequate, measures such as firewalls can be employed to reduce the impact of incidents (see Technical Measures Document Active / Passive Fire Protection). The operator should demonstrate that the storage location and design has taken into account site-specific security requirements and the potential for vandalism. Ventilation.

The preferred location for the storage of drummed flammable liquids and compressed/liquefied gases is in the open air, to allow vapours to be dispersed effectively. When located in buildings, the operator should demonstrate that there is an adequate level of ventilation achieved by either the presence of a SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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sufficient size and number of permanent openings such as louvres, or mechanical ventilation. If stored indoors, flammable gases such as LPG may only be stored in purpose-built compartments or buildings constructed with fire-resistant walls and explosion relief. Compatibility with other stored materials.

Toxic, flammable or self-reactive materials should not, in general, be stored in the same location (see Toxic, Technical Measures Document Se Segregation gregation of Hazardous Materials) Materials). The operator's risk assessment should demonstrate the compatibility of the substances stored and the suitability of the arrangements. HS(G)71 Chemical warehousing: the storage of packaged dangerous substances gives guidance on storage arrangements for warehouses and storage compounds. Layout. Drums and cylinders should be stored in a safe manner. Both the height and method of stacking should take into account the hazard of the material stored and the construction of the container. Racking or freestanding multi-layer stacks can be used for drummed materials storing low hazard liquids. Consideration should be given to the detection of leaks from containers and the method for collection and disposal of such spills to reduce the possibility of cross-contamination and domino effects. Training should be provided to operators on dealing with spills and emergency procedures.  Adequate access for forklift trucks should be provided. Pressurised cylinders and drums should be stored with their valves uppermost in a secure manner. The size of any particular stack should be limited, and separation distances should be provided between stacks. Drums should not be filled or emptied within the storage area. On-site transportation.

Whilst drums containing flammable liquids can be transported securely on a simple pallet, cylinders and drums containing compressed or liquefied gases require special care and appropriate means of transport such as cylinder trolleys or purpose-designed attachments for fork lift trucks should be used at all times. The operator should maintain records demonstrating that personnel involved in the movement of drums and cylinders have received training in the hazards involved in handling them, and in the operation of any machinery involved such as cranes and fork lift trucks. Connection and discharge to process.

Drums containing flammable substances should be adequately earthed prior to discharge (see Technical Measures Document on Earthing Earthing)). All containers should be secured in position before connection to process plant. A procedure should be in place for making the connection and all employees should have received adequate training in the use of the procedure. The materials used in making the joint, such as gaskets and lubricants, should be strictly controlled and an appropriate leak test should be carried out when the joint has been made. The pipework to which the container is connected should be designed to an appropriate standard. Where installations contain fluids at greater than 0.5 bar gauge pressure, they will usually be subject to the Pressure Systems Safety Regulations 2000 and such systems will usually be required to be subject to periodic examination at regular intervals. Design and maintenance of container.

Drums and cylinders should be designed and constructed to an appropriate standard. The operator should be able to demonstrate that an appropriate inspection and maintenance programme is in place in accordance with the relevant Regulations. The Regulatory framework is complex, with Transportable Pressure Vessels Regulations 2001( 2001(TVPR) and schedule 8 of Carriage of Carriage of Dangerous Goods (Classification, Packaging and Labelling) and Use of Transportable Pressure Receptacles Regulations 1996( 1996(CDGCPL2) currently applying in parallel. Essentially, CDGCPL2 applies to all types of transportable pressure receptacle, but there is currently a choice between complying with CDGCPL2 or TPVR in respect of cylinders, tubes and cryogenic receptacles (but not pressure drums).  As such, periodic inspection should be done at appropriat e intervals as required under CDGCPL2 or where inspection is in accordance with TVPR, at the intervals specified in RID and ADR (European Directives covering transport of dangerous goods by rail and road). SHEilds Ltd www.sheilds.org www.sheilds.org   eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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Containment of spills.

Suitable precautions should be in place for the containment of leaked materials. Where liquids are handled, suitable spillage containment such as bunding and drainage sumps should be in place.  Arrangements should be in place for the routine drainage of rainwater from sumps. Where materials that react with water are stored outdoors, the operator's risk assessment should demonstrate the suitability of the arrangements arrangements (see Case Study Staveley Chemicals Ltd - Derbyshire (27/6/1982)) (27/6/1982)). For the storage of toxic gases, location of the containers in a purpose-designed indoor store will reduce the rate at which gas is released to the environment. Control of ignition sources.

Where flammable liquids or gases are stored, the area should be subject to hazardous area classification for the control of ignition sources. This requirement should be reflected both in the equipment installed and in the control of operational and maintenance activities in the location. The movement of drums and cylinders often involves the use of forklift trucks, which can provide a source of ignition for flammable vapours. Any vehicle operating in a zoned area should be protected to an appropriate standard. Industry applications - Flammable liquids.

Containers should be stored in the open air where practical but if stored inside, five air changes per hour is considered a sufficient ventilation rate. Standard 205-litre metal drums should be stacked no more than three high and preferably on pallets or racking. The maximum stack size should be 300,000 litres with at least 4 metres between stacks. Storage should be on an impervious surface such as concrete and be bunded with drainage towards a sump or other suitable handling system. LPG cylinders.

Cylinders should be stored preferably in the open air on a concrete or load-bearing surface. Flammable liquids, combustible, corrosive, oxidising materials, toxic materials or compressed g as cylinders should be kept separate from LPG containers in general. Containers should be stored with their valves uppermost. The maximum size of any stack should not exceed 30,000 kg. For storage indoors, no more than 5,000 kg may be stored in each purpose-designed building compartment and a maximum of five compartments may exist in a single sing le building. Chlorine cylinders.

The vast majority of chlorine cylinder and drum stores are located indoors and should be solely used for storing chlorine. Access doors should fit closely to help contain any leak. These stores should be protected from any nearby radiant heat hazards. The store should be at least 5 m from any roadway.  A cylinder store should be at least 20 m from the site boundary and a drum store 60 m. Chlorine gas detectors / alarms should normally be provided. Risk assessments should be carried out to consider hazards arising from mishandling (dropping of containers in transport/handling), incorrect operation of valves and failure to connect correctly, maintenance errors and damage by external sources (domino, vehicle impacts, etc.).

2.6 - Storage of toxic and corrosive substances. substances. Toxic substances are defined in detail as: "Poisonous substances known or believed to be harmful to people's health, often producing chronic, irreversible physical problems and possibly harming subsequent generations."  Examples are:  

 Acrylonitrile.  Arsenic.

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 Asbestos.  Asbestos. Benzene. Beryllium. Cadmium. Chloroform. Chromates. EDB (ethylene (ethylene dibromide). Ethylene oxide. Mercury. PCBs PCB s (polychlorinated biphenyls).

Corrosive Substances are defined in detail as: "...substances which possess the property of severely damaging living (in particular human) tissue and of attacking other materials such as metal and wood."  The most common definition of 'corrosives' is: "... substances which, by chemical action will cause severe damage when in contact with living tissue or, in the case of leakage, will materially damage or even destroy, other freight or the means of transport; they may cause other hazards." 

2.7 - The implications for storage on incompatible materials and their segregation. Toxic Materials.

These are materials which, under either normal or disaster conditions or both, can be dangerous to living things around them. Carbon tetrachloride (tetrachloromethane), for example, if stored in a poorly-ventilated place under standard conditions, can evolve enough vapour to render the storage area toxic. Under disaster conditions of high temperature, if carbon tetrachloride is decomposed, it can form significant quantities of the highly toxic phosgene. It is nearly impossible to seal containers perfectly, so it is realistic always to expect that some of any volatile materials stored will escape into the atmosphere of the storage area. Also, air and atmospheric moisture will come into contact with the contents of imperfectly-sealed containers. Some initially well-sealed containers will build up enough internal pressure to break a seal or even burst the sealed unit. Materials which are toxic because of their radioactivity are also included in this category. These are dangerous if allowed to become airborne, or to be ingested or inhaled into the body. Under normal storage conditions, small amounts of radioactive materials may escape their containers and contaminate the atmosphere; disaster conditions such as high temperatures, severe shocks or floods can burst containers and volatilise, scatter or spread much larger quantities of radioactive materials. Sources of radiation enclosed in lead shielding can become dangerous in a disaster if conditions are such as to melt the shield or volatilise a radioactive material. Corrosive Materials.

Corrosive materials include acids, acid anhydrides and alkalis. Such materials often destroy their containers and get into the atmosphere of a storage area; some are volatile, others react violently with moisture. Acid fumes react to evolve toxic fumes with sulphides, sulphites, cyanides, arsenides, tellurides, phosphides, borides, silicides, carbides, fluorides, selenides; they liberate hydrogen upon contact with metals and hydrides. Alkalis may liberate hydrogen upon contact with aluminium, etc.  Acid mists or fumes corrode structural materials and equipment and are toxic to personnel. Such SHEilds Ltd www.sheilds.org www.sheilds.org   eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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materials should be kept cool, but well above freezing points. Acetic acid, for instance, can freeze in an unheated room and, due to differential expansion, crack a glass container. 

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There should be sufficient ventilation to prevent accumulation of fumes; there must also be regular inspection. Containers of corrosive materials should be carefully handled, kept closed, and labelled.  All exposed exposed metal in the vicinity of such storage should be painted and checked for weakening by corrosion. Corrosive materials should be isolated from materials noted above (cyanides, etc.), reaction with which can produce highly toxic fumes. Strong acids and alkalis will cause serious burns and eye damage to personnel; adequate protection in the form of gloves, aprons, goggles etc. should be worn when handling them into and out of storage areas. If hydrogen can be evolved, the building should be so constructed that possible hydrogen pockets are eliminated.

The main risks from the keeping and storage of hazardous substances include:   

Personal injury or ill-health caused by exposure to escaping substances. Fire and explosion involving flammable or unstable substances in the containers. Fire and explosion involving flammable or unstable substances as escaping liquid, gas or vapour.

These risks may also arise if incompatible substances are incorrectly stored together and an incident causes them to come into contact. Other factors that influence risk include: i nclude:  

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Durability of the container (e.g., fragility of glass bottles). The state in which the substance is kept (e.g., high pressure of compressed gases or low temperature of liquefied gases). The temperature of reactive instability. The greater the quantity of hazardous substance, the greater the risk from these hazards. Other agents such as heat and sources of fire and ignition increase risk.

By storage is meant the facility at which substances in sealed containers and compressed gas containers are kept but not used within that place. Storage includes tanks, cabinets, bins, open air compounds and walk-in buildings. For most substances, unless the substance is released or used, it does not present a risk to health and safety. A well-designed and properly used storage facility, and the segregation and separation of incompatible hazardous substances, should therefore present a very low risk. Gases, vapours, mists and dusts can give rise to explosive atmospheres. Areas where there is the potential for an explosive atmosphere to form must be classified as hazardous places under the DSEAR Regulations. For example, the interior of a highly flammable liquids store or cabinet should be regarded as a zone 2 hazardous place. Small quantities of hazardous substances may be kept within laboratories and other workrooms in suitable cabinets or bins. These amounts must be kept within the specified limits and not be excessive in relation to the rate of usage.

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2.8 - Handling of d angerous substances. substances. Explanation of flow through pipelines.

The movement of gases, liquids and solids etc. is a necessary evil. The substance has to be moved from A to B and however this is achieved, there needs to be a careful examination of the hazards and risks that are presented. Oil pipelines are an example of how substances are moved in vast quantities across the country (indeed, across continents). The health and safety issues connected with the use of pipelines such as this can be explained below: Pressure .

Pressure has to be applied in order for the quantity being pushed through the pipeline to maintain a correct flow. The pressure is required - yet can have an adverse effect on joints and flanges of the pipeline structure, making these areas vulnerable to overdue weakness (and failure). Static Electricity. Electricity.

Static electricity can build up, and discharge of the flow rate of the substance in the pipe is not correct (either too much or too little). Static is built up when molecules of materials that are not similar come into contact. Blockages.

Pipes can become blocked with foreign bodies - pressure then builds up or falls, and the system fails. Fire and explosion.

The spark from static electricity can ignite a fire and thus cause an explosion. Earth bonding systems are therefore required as a safety measure. Further information on pipeline safety can be found on the HSE website. However, a small extract of the information is outlined below: Introduction.

The Pipeline Safety Regulations 1996 (PSR) place a duty on operators of MAH Pipelines to provide certain information to HSE at various stages in the lifecycle of a MAH pipeline. Notifications should be sent to HSE at Lord Cullen House, Aberdeen for MAH pipelines in Scotland and Scottish Waters and to Thorpe Road, Norwich for all other onshore and offshore MAH pipelines; see full Notification addresses. These duties are covered in the following Regulations:   

Regulation 20: Notification before construction. Regulation 21: Notification before use. Regulation 22: Notification in other cases (e.g. change of pipeline operator or major

modifications to existing pipelines). These requirements only apply to MAH Pipelines. Regulation 20: New MAH Pipelines.

Regulation 20 requires that the construction of a new MAH Pipeline should not start until the operator has notified HSE, at least six months prior to the start of construction. PSR Schedule 4 lists the particulars required which includes the name and address of the operator. This notification may form the first contact between the pipeline operator and HSE for that pipeline. The intention is that this notification should be made at the 'end of the concept design' stage and hopefully before major SHEilds Ltd www.sheilds.org www.sheilds.org   eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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expenditure has been committed to by the duty holder. Operators often approach HSE in advance of regulation 20 requirements to discuss plans and designs. If an operator is in any doubt as to whether HSE is aware of its identity and/or its MAH Pipeline(s) it should contact HSE (see full Notification addresses). Multiple Construction Sites: under regulation 20 if construction of a MAH Pipeline occurs at more than one location (e.g. onshore, offshore or a combination of both) and in more than one stage, notification to HSE should occur at least 6 months before the first stage begins. An example is where a pipeline bundle intended for offshore use is constructed on land and is then taken for final assembly and connection to an offshore installation. Construction of the pipeline under these circumstances is deemed to start at the first stage on land, not at the subsequent phase offshore. Regulation 21: Notification before use/re-use.

Under regulation 21, HSE requires 14 days' prior notification of the intention to bring a MAH Pipeline into use, so that it has the opportunity of a final inspection before a dangerous fluid is first introduced into the pipeline. This regulation also applies where a pipeline is to be brought back into use after it has been taken out of commission (other than where the circumstances were routine maintenance, planned or emergency repair). PSR Regulation 22(1): Change of MAH Pipeline Operator.

The operator of a MAH pipeline may change at any time throughout the life of a pipeline. Under regulation 22(1), any change of operator must be notified to HSE within 14 days of the change. If a pipeline is transferred from one operator to another, there must be sufficient information passed to the new operator so that all the relevant duties can be complied with. The onus is on the new operator to ensure that it has sufficient information to comply with PSR, and to enable proper decisions to be made about the integrity and safety of the pipeline. Regulation 22(2): Other Cases.

Regulation 22(2) requires notification in other cases. The notification period for this Regulation is at least three months. Regulation 22 concerns significant changes to the pipeline which can affect the level of risk. Examples include:   

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Major modifications/remedial work to the pipeline. Changes in safe operating limits e.g. when changing from one pressure to another. Changes in fluid composition or type. Pipelines may be designed to operate with dry gas but changes to the status of offshore installations may only be achieved if the gas can be transported in a wet state - this may have a significant effect on the integrity of those pipelines and downstream facilities. End of use of a pipeline. This notification should set out the steps to be taken to decommission, dismantle or "abandon" a pipeline. It is envisaged that a notification will comprise a timetable indicating when the pipeline is to be taken out of service, how long the line is to remain decommissioned and a description of how the line is to be made permanently safe. Changes in pipeline materials and equipment. This may comprise no more than a map or chart showing where the changes are to take place and a brief description of the material and/or

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dimensional changes. Re-routing of pipelines e.g. in proximity to offshore installations which could have an effect on the safety of the installation. Re-routing of pipeline risers on offshore installation, which may then pass closer to living quarters or other vulnerable areas. The repositioning of Emergency Shut Down Valves (ESDVs) on pipeline risers.

2.9 - Outline of safety principles in filling and emptying containers. Overfilling:

Overfilling of containers must be avoided. Ensuring the correct quantity of substance is only used when filling the container is a priority. A safe system of work must be in place in order to give clear instructions etc. as should emergency arrangements in place to deal with any spillages or first aid requirements. Suitability:

The container(s) must be suitable for the purpose. This means making sure that the container being used can 'house' the substance being put into it without interfering with its structural integrity. Clean and Empty:

The container must be empty of all traces of what was previously in it, and it must be thoroughly cleaned in order to ensure that substances are not inadvertently mixed. Hazards to be aware of when cleaning and emptying containers include:   

Spillage of substance. Escape of vapour. Electrostatic charges.

Marking:

The correct marking of suitable containers is required in order to ensure the correct substances are identified.

2.10 - The safety principles in dispensing spraying and disposal of flammable liquids. Dispensing Flammable Liquids: 

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Ensure that the area where flammable liquids are dispensed has mechanical ventilation from floor level to the outdoors. Ensure that there are no ignition sources (sparks, hot surfaces, torches, open flames, pilot lights) in the dispensing area. Mark entrances to dispensing areas with suitable warning signs. When opened for dispensing, flammable liquid drums should be fitted with pressure-relief venting.  Acceptable transfer pumps or self-closing safety taps must be used during the d ispensing of flammable liquids. The self-closing safety taps should be equipped with drip-proof, replaceable O-rings and flame arrestors. Containers and dispensing equipment must be bonded and grounded when flammable liquid is being dispensed.

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In the case of non-conducting containers, ensure that measures are taken to minimize the potential for static charge to develop, for example:   

Use a grounded nozzle extension to the bottom of the container. Limit the distance that the liquid falls. Slow the rate at which the liquid is transferred.

Ensure that portable containers used for dispensing flammable liquids in a work area:   

 Are made of material suitable to provide for the safety of all employees. Have spring-loaded caps. Have flame arrestors.

Hazards of spraying flammable liquids.

In many cases, employers and employees at these workplaces are not fully aware of the potential risks to the health and safety of their employees from exposure to chemicals used in the spray painting process. Without the proper control measures in place, prolonged exposure to these chemicals over a period of time may lead to serious injury or illness. There are two main hazards associated with spraying of flammable liquids:  

Fire and/or explosion - due to the flammable nature of the substances used. Hazards to health - depending on the hazardous nature of the substance, the potential health effects may be short term and/or long term.

Fire risks. Fire or explosion may occur if:  

Vapours of flammable liquids accumulate to high enough concentrations, and There is an ignition source present.

The ignition source can be:     

Static discharge from poorly-earthed equipment. Sparks from electrical switches and equipment. Naked flames (e.g. welding or cutting, lit cigarettes, heaters). Portable battery-powered equipment (e.g. radios, mobile phones). Hot surfaces, the hot filament from a broken light, etc.

Health risks.

There may be various health effects associated with the use of flammable liquids. Depending on the substance being sprayed, the length of time exposed and frequency of exposure, these substances can cause:    

Difficulty in breathing. Skin and eye irritation. Drowsiness. Nausea.

Sensitisation.

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Specific information on the health hazards of the flammable liquid being sprayed can be found in the Material Safety Data Sheet (MSDS) for that substance. The MSDS is available from the manufacturer, importer or supplier of the substance and should be read prior to the substance being used. Eliminate the hazard.

The simplest way to avoid being exposed to a fire or health risk is to not use the potentially harmful product; i.e. eliminate the hazard. This might not be practicable in situations where there is no suitable method to eliminate the harmful substance. However, hazards can still be eliminated by changing the process. For example, consider using a physical fastening system instead of a solvent-based glue. If eliminating the hazard is not practicable, reducing exposure to harmful chemicals and reducing the risk of fire and explosion can be achieved by using effective control measures. Controlling the risk.

When developing and implementing risk control measures at a workplace, it is important to consult with health and safety representatives and employees, as they are a valuable resource for determining the suitability of control measures. Employers should develop suitable risk control measures in the following order:   

Substitution or isolation or engineering controls.  Administrative controls. Personal protective equipment.

Often effective control of the risks involves using a combination of the above measures. Risk control through substitution. Substitution is a process of using a chemical that is less hazardous or using a chemical in a less hazardous form. Consider :   

 Applying the substance with a brush or roller in a sufficiently ventilated place. Using water-based paints instead of solvent-based paints. Using lead-free paints instead of lead-containing paints.

Before a new product is used, an assessment should be carried out to ensure that other hazards are not introduced. Risk control through isolation. Isolation involves separating people from the substance being sprayed, usually by distance or using physical barriers. For example:  

Erecting a fully enclosed spray booth (also considered to be an engineering control). Designating a dedicated spray area, such as a shed or an isolated room.

If a designated spray area is established, additional administrative controls will be required, such as:

1. Ensuring there is restricted access to spray areas. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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2. Ensuring that the spray area is adequately ventilated after spray painting, before allowing any entry without respiratory protection. 3. Ensuring that no ignition sources are within the hazardous area, or electrical wiring/equipment has been installed to an appropriate standard. In some circumstances, atmospheric monitoring will be required to ensure workers are not being exposed to air borne contaminants above the relevant exposure standards. Risk control through administrative controls. Administrative controls include safe work practices or systems of work aimed at reducing the risk of using the flammable liquid. Examples of administrative controls include: 

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Ensuring touch-up work using a spray gun takes no longer than 5 minutes in any 60 minute period (where this work is performed outside a spray booth). Setting up safe working and emergency procedures (refer to the MSDS), such as restricting access to painting areas to staff who need to be there and installing portable fire extinguishers appropriate to the products being stored and handled. Ensuring ignition sources are not introduced into the proximity of flammable liquids being handled or stored; e.g. not having electrical equipment such as scales, microfiche readers or computers in paint mixing and handling areas, or bringing radios into spray booths. Maintaining good housekeeping practices, such as cleaning up spills immediately, keeping lids on containers of solvent-based products when not in use, and disposing of solvent-soaked rags promptly. Not storing flammable liquids in spray booths. Store only minimum amounts of flammable liquids on site and use proper fire-rated cabinets or, for larger quantities, fire-rated store rooms. Posting appropriate safety signs. Prohibiting eating, drink and smoking around chemicals. Developing a health surveillance program for certain substances.

Risk control through use of personal protective equipment.

Personal protective equipment (PPE) is the least preferred option in the hierarchy of risk control and should never be solely used to control risk. With any use of PPE:   

Employees should be trained and supervised in the correct wearing of the PPE. There should be a program of regular maintenance of PPE. Records should be kept of the above activities.

Disposal of Flammable Liquids:

This should happen in suitably closed containers that are compatible with the substances in them. Wastes must not be mixed. The Environment Agency must be consulted if you have any questions or concerns.

2.11 - Explanation of the dangers of electricity in hazardous areas. Zones are established in the BS 5345 and are reproduced below: Zone.

Description.

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A place in which an explosive atmosphere is present continuously for long

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1 2

periods. A place in which an explosive atmosphere is likely to occur in normal operation occasionally A place in which an explosive atmosphere is not likely to occur in normal operation, but if it does occur, will persist for a short period only Table 1. Zones.

In relation to electrical equipment, it can be seen that the zones are of utmost importance. Areas outside these zones are classed as 'non-hazardous zones'. The table below gives further detailed guidance as taken from the Institute of Petroleum publication - 'Model Code of Safe Practice pt15'. Item.

Area.

 Above-ground tanks.

(a) Vertically from ground level to the height of the bund wall and horizontally from the tank shell to 1 m outside the bund wall. (b) Within 2 m of the tank shell. Underground tanks. Within any manhole chamber containing filling connections. Tank connections (all tanks). Within a horizontal radius of 4 m from tank filling connections and vertically from ground level up to 1 m above the connections.  All tanks. Within the vapour space. Vent pipes. (a) Within a radius of 3 m in all directions of the open end of any vent pipe. (b) The area below the Zone 1 area of any vent pipe, for a radius of 3 m around the discharge point and down to ground level. Pumps and sample points. Within a horizontal radius of 4 m and vertically from ground level to 2 m above the unit. Road and rail tankers (at (a) Within 300 mm in any loading/unloading points). direction of any opening on the tanker and down to ground level (b) Within 2 m of the shell of the tanker. (c) Within a horizontal radius of 4 m from tanker discharge connections and vertically from ground level up to 1 m above the connections. (d) Within a radius of 1.5 m of any opening on the tank top and down to ground level. (e) On the top of the tank within the valence.

Classification.

Zone 2.

Zone 2. Zone 0. Zone 2.

Zone 0.  A) Zone 1. B) Zone 2.

Zone 2.

 A) Zone 1. B) Zone 2. C) Zone 2. D) Zone 1. E) Zone 1.

Table 2. 'Model Code of Safe Practice pt15'. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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2.12 - Transport of dangerous substances. Introduction. The main piece of legislation for th is area (which is complex) is:

The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2004 (as amended).  ADR - European Agreement Concerning the International Carriage of Dangerous Goods Regulations by Road.  An example Dangerous Goods Policy is outlined below. Although the document applies to a University, its content shows you the complexity of the subject: Transport of dangerous goods by road in vehicles.

 A number of departments transport chemicals and other h azardous materials over the public roads. The Regulations which cover the transport of dangerous goods by road are complex and can be somewhat difficult to understand and interpret. There are, however, quantity thresholds below which many of the legal requirements do not apply. Departments will often transport only limited quantities of chemicals and should be able to take advantage of these quantity thresholds to simplify compliance with the Regulations. This guidance note provides a simple outline of the legal requirements for the transport of dangerous goods by road. Its main purpose to enable departments to determine the quantity thresholds which apply so they can take advantage of them. For more details, departments should contact the Safety  Adviser. 1.Are the goods being carried deemed to be "dangerous goods"?

Chemicals which are explosive, toxic, corrosive or flammable will usually be regarded as dangerous goods. Any materials shown on a supplier's health and safety data sheet as being in packing group or transport category 1, 2 or 3 should be regarded as being dangerous goods for transport purposes. In addition the Health and Safety Executive publish a list called the "Approved carriage list" which identifies chemicals deemed to be dangerous goods for transport purposes. (Contact the Safety  Adviser if you want to consult a copy of the list.) 2. Packing the goods.

Many of the regulations covering the packing of dangerous goods do not apply to small quantities. The table below gives some of the exceptions. Goods.

Flammable liquid. Flammable solid. Substance which emits flammable gas on contact with water. Oxidising substance. Organic peroxide - solid. Organic peroxide - liquid. Toxic substance - solid. Toxic substance - liquid. Corrosive substance - solid.

Maximum quantity per receptacle.

1 litre in metal packaging 500 ml in glass or plastic packaging. 500 g 500 g 500 g 100 g 25 ml 500 g 100 ml 1 kg

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Corrosive substance - liquid.

500 ml (but glass receptacles must be enclosed in compatible and rigid intermediate packaging) Environmental hazardous substance not 5 Kg elsewhere specified - solid. Environmental hazardous substance not 5 litres elsewhere specified - liquid. 'Table 1'

Chemicals in quantities above these amounts are not exempt from the packaging requirements. They must be classified and then packed to a standard consistent with that classification. The classification details can be obtained from the supplier's safety data sheet but it is likely that departments will then need expert assistance to determine what packaging will be necessary. However, if chemicals were obtained from a reputable supplier then a simple way to find out how they should be packed is to look at how they were packed when they were delivered to the department. If at all possible, the same packaging should be used for the onwards journey by road in the vehicle. 3) Labelling the package.

The package containing the dangerous goods must be labelled with the shipping name of the goods and the UN number, both of which can be obtained from the supplier's safety data sheet. The appropriate hazard warning diamond must also be attached to the package. Again, as with packaging, the best way to find out how goods should be labelled is to look at how they were labelled when they were delivered to the department and to use the same labelling for the onwards journey. If the goods are in receptacles below the quantity thresholds in (2) above, then the hazard warning diamond is not required. 4) What information must to be given to the driver and how should the vehicle be marked?

 As with packaging and labelling, there are quantity thresh olds below which the legal requirements relating to the operation of the vehicle carrying the dangerous goods on the road do not apply. The quantity thresholds are based on the transport category which can be obtained from the supplier's safety data sheet. (The packing group as detailed on the data sheet will usually be equivalent to the transport category.) Transport category.

Mass or volume per individual package (kg or litres).

Total mass or volume of packaged dangerous goods carried on the vehicle (kg or litres).

1 2 3

1 10 25

20 200 500

'Table 2'

Where goods of different transport categories are carried in the same load, all the dangerous goods should be deemed to belong to the most hazardous (lowest) transport category for the purposed of determining the quantity threshold for the complete load. Departments are strongly advised to ensure that any load containing dangerous goods carried on a vehicle is below both of the quantity thresholds indicated above. If either of the thresholds will be exceeded, the Safety Adviser should be contacted for advice before the journey is undertaken. If neither threshold is exceeded, there are no requirements to formally provide information to the driver or to mark the vehicle. (Note that the plain reflective orange panels which are often seen displayed on vehicles carrying dangerous goods should not be displayed unless the quantity threshold for the total mass/volume on the vehicle is exceeded.) SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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5) What about liquid nitrogen?

The main hazard when transporting liquid nitrogen is that of asphyxiation within the enclosed space of the vehicle. BOC's health and safety data sheet for liquid nitrogen states "Avoid transport on vehicles where the load space is not separated from the driver's compartment". Departments should not transport liquid nitrogen by road in vans where the load space is connected to the driver's cabin. 6) Other matters to be considered.

If a load falls below the quantity thresholds, a consignment will be exempted from may of the specific regulations which apply to movements of dangerous goods by road. Nevertheless we will still have general duties under health and safety law to ensure that we do all that is "reasonably practicable" to ensure that the consignment is safe and will not endanger the health and safety of the driver or other persons. Departments should consider the following points when arranging for the transport by road of any dangerous goods in any quantities: 

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Dangerous goods should not be given to Estates mail delivery staff or porters for transportation by road. Goods should always be accompanied by staff from the department who have a knowledge of the goods concerned and the action to be taken if there were a spillage. Chemicals should always be packed in a secondary container which would reduce the likelihood of any leakage and also minimise the risk of damage to the primary container. Packages should be loaded into the vehicle so that there will be no tipping, sliding or other movement while in transit. Packaging should be suitable to prevent damage due to jolting of the vehicle when passing over speed bumps, potholes etc. If two chemicals which are being carried could react, as much segregation as possible should be provided. Packages of dangerous goods should always be labelled as to their contents. (Consider a situation in which an accident had left the driver of the vehicle unconscious and the emergency services were attempting to determine the nature of the load in the vehicle.) Vehicles being used to transport dangerous goods should never be left unattended unless absolutely necessary. If a vehicle must be left for a short time, it should always be locked.

UN numbers.

The assignment of UN numbers, packing group and hazard class is based on the criteria as laid down in the Recommendations on the Transport of Dangerous Goods Model regulations as published by the United Nations, 13th edition (so-called 'Orange Book'). The assigned UN-number is a recommendation, which should be used to verify detailed differences between the various modes of transport, such as: air, sea and land (land transport can be separated into road, rail and inland water ways). 'Where needed, the EU hazard classification of the substance is supplemented with the ADR-rules, including the links to the EU-DSD and DPD. '

 Also, for transport, due account should be given to any national deviations from the rules applied here.

2.13 - Video: Transportation of dangerous substances.

http://www.sheilds-elearning.co.uk/file.php/4/videos/C4_TransDangSubs.flv

2.14 - Outline of key safety principles in loading and unloading of tankers and tank

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containers. ISO tanks or portable tanks (conforming to ISO 1496-3) are held in boxes on the back of tankers like this:

Figure 1. ISO Tank.

 As demonstrated above, the container is locked into the framework and t he complete fixture is transported. Transport Emergency Cards (TREM card). Transport Emergency Cards (Instructions In Writing).

Transport Emergency Cards (Tremcards) are automatically produced for any product that is classified with a UN number. ChemSoft Transport Emergency Cards are fully compliant with current legislation and can be printed in any of the languages listed in the ADR regulations. Companies who ship hazardous goods throughout Europe need to provide the driver with Transport Emergency Cards (Instructions in Writing). These emergency instructions must be written in the language the driver can understand and of those countries through which the load will travel.

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Figure 2. Example Trem (Transport Emergency) Card.

2.15 - Outline of labelling of vehicles and packaging of substances.

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The following diagram shows the signs and marking required on tankers and their containers:

Figure 1. Tankers and their Signs & Markings. In more detail: 2W = Emergency Action Code 1832 = The UN Number

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Transporting in packages:

If the dangerous goods are transported in packages, then the package should be in suitably-marked containers etc. displaying a smaller diamond-shaped hazard warning sign and the UN Number (preceded with the letters 'UN').

2.16 - Driver training and role of Dangerous Goods Safety Advisers. Driver Training:

 Anyone involved in the carriage of dangerous goods by roa d has to make sure that they and any of their employees who have any responsibility for such carriage are appropriately trained. This requirement covers, for example, loaders and un-loaders, personnel in freight-forwarding agencies, and drivers who do not require specialised driver training. The training must include:  



 Awareness training, covering the general requirements of ADR. Function-specific training, covering the detailed requirements of ADR and (where relevant) other modes of transport. Safety training, covering the hazards and dangers presented by dangerous goods and awareness of safe handling and emergency response procedures, commensurate with the degree of risk of injury or exposure arising from an incident involving carriage of dangerous goods.

Details of all training should be kept by the employer and employee. Training must be verified when starting a new job, and there should be periodic refresher courses taking account of changes in the law. Driver training requires drivers of:   

Vehicles with a permissible maximum mass exceeding 3.5 tonnes carrying dangerous goods. Tank vehicles. Vehicles carrying Class 1 dangerous goods, or certain Class 7 (radioactive) material.

To hold a certificate ('VTC' or vocational training certificate) issued by the Department of Transport, stating that they have attended appropriate training courses and passed an examination on the requirements to be met during carriage of dangerous goods. The main objectives of training (which must include theoretical courses, individual practical exercises and appropriate refresher and specialist training) are to:   

Make drivers aware of hazards arising in the carriage of dangerous goods. Give them basic information to minimise the likelihood of an incident taking place. Enable them to take necessary measures for their own safety and that of the public and the environment, to limit the effects if an incident does occur.

Drivers of vehicles carrying dangerous goods must, on request, produce their VTC to the police or any goods vehicle examiner. Drivers not requiring a VTC are still covered by the general training requirements of ADR. Dangerous Goods Safety Advisers (DGSAs) :

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and related loading (but not unloading), or filling, to appoint one or more dangerous goods safety advisers (DGSAs). Their overall duty is to make sure that carriage of dangerous goods and related activities are conducted in accordance with requirements and in the safest possible way. They advise on, and ensure compliance with ADR requirements for:    

Identification of dangerous goods. Equipment used in connection with carriage and loading. Training of employees and maintenance of training records. Emergency procedures to be taken in the event of any accident or incident that may affect safety.

DGSAs are also responsible for preparing for management an annual report on relevant aspects of the carriage of dangerous goods by the organisation, and for ensuring that an accident report is prepared whenever an incident involving the carriage of dangerous goods affects people, property or the environment. DGSAs have to be capable of performing their duties. They must undergo training, sit an examination and hold a vocational training certificate (valid for five years) to become a DGSA. The requirement to appoint DGSAs does not apply to organisations: 



Whose activities involve the carriage of dangerous goods in quantities per transport unit below those referred to in ADR 1.1.3.6. Whose main or secondary activity is not the carriage or loading of dangerous goods, but which occasionally engage in the domestic carriage or related loading of dangerous goods posing little danger or risk of pollution.

3 - Hazardous Environments.

The UK's Electricity at Work Regulations, Regulation 6 covers details of the ways in which electrical equipment can be affected by adverse or hazardous environments and the methods that can be employed to guard against these hazards. Electrical equipment which may reasonably foreseeably be exposed to: (a) Mechanical damage. (b) The effects of the weather, natural hazards, temperature or pressure. (c) The effects of wet, dirty, dusty or corrosive conditions. (d) Any flammable or explosive substance, including dusts, vapours or gases, shall be of such

construction or as necessary protected as to prevent, so far as is reasonably practicable, danger arising from such exposure. The regulation draws attention to the kinds of adverse conditions where danger could arise if equipment is not constructed and protected to withstand such exposure. The regulation requires that electrical equipment should be suitable for the environment and conditions of use to which it may reasonably foreseeably be exposed so that danger which may arise from such exposure will be prevented so far as is reasonably practicable. Effects.

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The conditions at which the regulation is directed are those occurring naturally as well as those resulting from human activities, including the following: (a) Mechanical damage including impact, stress, strain, abrasion, wear, vibration and hydraulic and

pneumatic pressure. (b) Effects of the weather, which include both short-term (e.g. wind, ice and snow, lightning) and longterm (e.g. temperature cycling) effects. (c) Natural hazards, which are those resulting from other than man's activities and include animals, trees and plants, tides and solar radiation etc. (d) Temperature and pressure. (e) Liquids which include water and other liquids and their effects, including humidity, condensation, flooding, splashing, or immersion in these, cleaning with liquids, hosing down and solvent and solvent vapour action (electrically conducting and non-conducting liquids may present different aspects of electrical danger). (f) Dirty conditions which include all contamination as a result of liquids or solids (electrically conducting and non-conducting dusts may present different aspects of electrical danger). (g) Corrosive conditions which include all chemical action and reactions and electrochemical effects. (h) Flammable substances including flammable dusts and flammable vapours. (i) Explosive substances which include both any mixture of solids, liquids or gases which is capable of exploding and substances intended to be explosive (ie explosives). In gauging the suitability of equipment for particular environments or conditions of use it is necessary to consider only those effects or exposure which are reasonably foreseeable. Mechanical damage.

The mechanical damage to which electrical equipment may be subjected varies considerably from one environment to another. For example, equipment designed for use in an office is unlikely to be suitable, without further protection or careful siting, in a workshop or farm environment. The effects covered by regulation 6(b), (c) and (d) may also impose mechanical stresses on electrical equipment. For example, ice and wind loading, or loss of mechanical strength due to expansion and contraction resulting from temperature changes, can give rise to mechanical damage. This regulation requires the mechanical protection, if necessary, of the insulation which is required under regulation 7(a). Further suitable protection in addition to basic insulation may be necessary to form the physical protection necessary to ensure the continuing integrity of basic insulation, e.g. conduits or a trunking for single insulated conductors or the armouring or tough external sheathing of composite or multi-core electric cable. Weather, natural hazards and extreme conditions.

Precautions which are taken to protect a site, structure or building from natural hazards and extreme weather conditions may give some protection to the associated electrical installation, but additional protection or precautions may be necessary. Extremes of temperature, pressure or humidity may result either from climatic conditions or from adjacent plant or from the use of the electrical equipment itself. Standards frequently quote the range of service conditions for electrical equipment, including temperature limits, and users should consider these when selecting equipment. Corrosive effects.

If substances are present in the environment which either alone, in combination, or in the presence of moisture can cause accelerated corrosion of metallic enclosures or fittings, special mate rials or surface treatments may be necessary. In these cases it would be recommended that much of the electrical equipment, e.g. motors, be of a type which is totally enclosed by an appropriate corrosionresistant housing, ie not ventilated to the atmosphere. Insulating materials and other materials used in electrical equipment may be affected by chemical agents or solvents. Cubicles housing electrical control equipment in hostile environments may need to be kept purged or pressurised with clean air or, in special cases, inert gas.

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Dirt and dusts.

Most industrial enclosures for electrical equipment do not resist the entry of fine dusts. Equipment should be constructed so as to resist the entry of dust and dirt where this may give rise to electrical and mechanical failures. Regular inspection and cleaning as necessary is recommended where dirt and dusts are likely to accumulate. A particular example is that of portable motor-driven equipment incorporating ventilation slots which can give rise to the accumulation of potentially hazardous layers of dirt and dust. Combustible dusts.

In cloud form, some dusts create an explosion hazard, while layers of combustible dust on electrical equipment can give rise to fire hazards. The selection, construction or installation of the equipment so exposed to combustible dust should be such as to guard against the possibility of ignition. The maximum temperature attainable on the surface of any electrical equipment where these dusts may be deposited should be considered in the selection of the equipment. The temperature of such surfaces should always be below the temperature at which any charring or smoking of dust takes place. However, appropriate dust control measures and general cleanliness which minimise the problem at source are to be preferred. Potentially explosive atmospheres.

If electrical equipment is used where a flammable or explosive atmosphere is likely to occur the equipment shall be so constructed that it is not liable to ignite that atmosphere. The selection and installation of equipment for use in potentially explosive atmospheres should be guided by the recommendations contained in the HSE guidance and British Standards on the subject. Existing installations complying with the recommendations of earlier standards should be acceptable for continuing service, subject to proper maintenance. It is recommended that the choice of electrical equipment be from that which has been certified as being in conformity with an appropriate standard. Uncertified electrical equipment should not be used unless it will provide at least an equivalent level of safety to that provided by appropriately certified equipment. Some manufacturing processes, for example electrostatic paint spraying, make use of the characteristics of static electricity and the design of electrical equipment needs to be such that the ignition of solvents, vapours or particulate substances is prevented. The maintenance and repair of explosion-protected equipment is a specialised field of work and should be undertaken only by those who have the necessary training and experience. Other flammable substances.

Much electrical equipment generates heat or produces sparks and this equipment should not be placed where either the heat emitted or the occurrence of sparking is likely to lead to the uncontrolled ignition of any substance. The construction of the equipment should either exclude the substances from any part of the equipment which may be a source of ignition (e.g. by suitable enclosure) or should ensure that the equipment operates at sufficiently low temperature and energy levels as not to be a source of ignition under likely conditions of use and fault. Classification system of ingress protection (IP rating).

There is an internationally recognised system of classifying the degree of protection provided by enclosures against the ingress of solid objects and moisture, and the protection afforded against contact with any live parts within the enclosure for all types of electrical equipment. The system is commonly known as the IP rating system (IP = Index of Protection).

3.1 - Wet Environments - Corrosion, Degradation and Damage.

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 All water intrusion events have similar impacts on electronic, electrical and mechanical systems, differing only with the types of secondary contaminants dissolved within the water along its leakage path and the types of metals used in the systems. In many water damage events, where a large volume of water is involved without passing through ceilings or walls, secondary contaminants are essentially negligible. The impact of water on metal surfaces is highly dependent on the metal type, contact time, and most importantly whether the metal was powered (directly or indirectly) at the time of the event. Water impact to exposed metallic surfaces may be defined within five categories (in increasing level of impact):      

Water residue deposition. Hygroscopic dust activation. Oxidative corrosion. Galvanic corrosion. Electrolytic corrosion. Short-circuiting, heating and arcing.

The impact of water residue on a metallic surface, where corrosion has yet to occur, is simply that the deposited material may make the surface more susceptible to future corrosion during a high humidity event, particularly if the deposited materials contain any hygroscopic ("moisture absorbing") salts. Deposited residue should always be removed from metallic surfaces after a water intrusion event, when it is safe and non-disruptive to do so, both to avoid any potential long-term corrosion concern, as well as to easily identify the impact of any future water ingress or condensation problem. Equipment that is already contaminated with sub-micron particles, deriving from outdoor ventilation air in particular, can experience current leakage and shorts when the relative humidity rises above the deliquescence point of salts contained in the pre-existing "dust" deposited on sensitive electronic circuits, such as those in telecommunications central offices and data centres. This mechanism is commonly referred to as "hygroscopic dust failures". The hygroscopic dust failure mechanism remains an important concern after a water leakage or high humidity event. The cleaning of electronic circuit boards and backplanes of telecommunication switches and data centre computer electronics is often recommended after such events because of this reason. Oxidative corrosion is the most common impact of water (and moisture) on metallic surfaces, with the rusting of iron (forming ferric oxide) as the prime example. The degree of oxidative corrosion is highly dependent on the time that the water is in contact with the metal, the type of metal (iron is easily oxidised, aluminium is much less susceptible) and the amount of time that the wet surface is exposed to air before complete drying. The impact of oxidative corrosion may be measured by the amount of metal that is oxidized or more simply the depth below the surface that has been oxidised. Of importance to damage assessment is that oxidative corrosion tends to be a self-limiting chemical reaction (as opposed to galvanic and electrolytic corrosion or acidic gas contamination from a fire involving PVC). As a surface becomes oxidised, there are less metal molecules exposed to the air and available for further oxidation. Thus, surface oxidation of some metals (e.g., stainless steel) actually is a beneficial "surface passivation" mechanism that inhibits corrosion deep into the material. In other metals, such as copper, oxidative corrosion may take several different forms. In the presence of common atmospheric pollutants (sulphur oxides), copper will form copper sulphate, providing a "patina" green colour that is often a desirable architectural feature. Under other circumstances copper will form cupric oxide ("copper tarnish"), a black non-conductive material that in electrical systems may SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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make it difficult to gain a low resistance connection to copper buss bars. Fortunately, copper tarnish is readily removable by solvent or abrasive cleaning and further tarnish may be prevented through the application of an anti-oxidant coating to the copper surface. Galvanic corrosion is actually a form of corrosion that may occur without direct water damage but is highly enhanced in the presence of water. Galvanic corrosion is essentially an electrochemical process that causes the removal of surface metal molecules (at the anode metal) when a low level current flow is created by contact between two dissimilar metals. Every metal has a unique electrical potential in the "galvanic series". Contact of dissimilar metals will allow a low level cu rrent to flow between the metals, depending upon the difference in potential between the metals. The anode of the metal pair is the sacrificial metal, loosing ions that are deposited on the cathode. The presence of water speeds up galvanic reactions in two ways. First, water may bridge dissimilar metals that are not normally in contact, creating a galvanic cell. Secondly, water contact may act as an electrolyte, enhancing the current flow between dissimilar metals that may already be in contact. The impact of galvanic corrosion often is limited to delicate electronics and occasionally the aesthetics of ductwork and other galvanised surfaces. It is interesting to note that the purpose of "galvanising" steel surfaces (air duct sheet metal, conduits, and electrical panel encasements) is that the zinc plating is meant to act as a sacrificial anode to protect the underlying steel. For short length of exposures, galvanic corrosion is often not a factor involved in water leakage losses, except as related to the long-term exposure of galvanised conduit, electrical connector boxes and electrical panel interiors. Electrolytic corrosion occurs as a result of water contacting powered metallic surfaces. The presence of water on powered equipment results in the creation of a continuous leakage pathway from the powered surfaces to ground. In a DC current system, this electrical leakage occurs from th e battery providing continuous DC current, resulting in the immediate start of electrolytic corrosion. Electrolytic corrosion or "electrolysis", which produces a metal-carbonate (e.g., the blue-green coloured copper carbonate), will continue until the power is eliminated. The continued creation of electrolytic corrosion for even a few minutes often results in non-repairable damage to circuitry and components of powered DC systems (e.g., fire and security alarm panels). In AC powered systems, electrolytic corrosion is much less rapid a nd often results in much less damage due to the voltages involved and the thickness ("bulk") of the metals used in common AC powered building applications (e.g., switchgear, electrical panels, cabling and connectors). While electrolytic corrosion is devastating to microelectronics, since it oft en irreparably removes protective surface metals exposing base metals to rapid corrosion, it is often easily removable from  AC electrical systems through simple abrasion of the corroded surface. This assumes that the corrosion product is fully removed, that the power was removed shortly after the system was impacted by water, and that no arcing damage has occurred as a result of shorts to ground. If the corrosion product is allowed to remain on powered surfaces, particularly within connectors where it is difficult to see, the surface will continue to corrode. If left unattended, electrolytic corrosion will result in electrical failure due to high electrical resistance that develops at connectors. This resistance promotes heating at connectors or even within the current carrying member itself. Under worse case conditions, this heating can result in a fire. It is for this reason that electrolytic corrosion must be removed from all current carrying surfaces.  A more common concern with water intrusion into powered electronic systems that can occur at the time of the event is hard failures due to electrical short-circuiting. Short-circuits form when water bridges normally isolated conductors. Continued current flow produces electrolytic corrosion products SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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that may also result in the bridging of isolated conductors. This can lead not only to electrical failure but also to arcing and fire if the current draw remains below the fusing current, causing excess heat to be generated. It should be noted that electrical systems, electrical connectors, wires, conduit and most metallic and polymeric surfaces will not be damaged by non-condensing moisture in the air even at high relative humidities, assuming the lack of significant dust contamination. Clean electrical systems require condensed phase water to cause electrolytic corrosion. Galvanized metal, such as used for electrical conduit, is a specifically chosen material for high humidity conditions. The one concern with electrical systems in the presence of a moist environment is when they have been heavily soiled with airborne contaminants that are hygroscopic (water absorbing) in nature. Such contaminants often are deposited on indoor surfaces and derive from insufficiently filtered outdoor air used for ventilation. Such dust could impact systems that have been in place for numerous years. However, for new installations that have only been exposed to construction and renovation related dust (wallboard, concrete and common soil particles), damage to such surfaces would not be expected to occur solely due to high humidity. For an environment that contains steam, such as within boiler rooms, condensing moisture is a significant corrosion issue for electronics and electrical systems. The degree of corrosion associated with such a steam environment would be significant (up to 2.2 mm depth per year for unprotected low carbon steel), making discrimination between water leakage or flood loss related and long-term ambient corrosive damages difficult to determine. However, there are several methods or pieces of evidence that makes this discrimination possible. For iron containing materials (sheet metal panels, screws, pipe, etc.), the colour of the surface oxidation layer (i.e. rust) is often a distinguishably different colour (more orange) for more recent water exposure than for rusting from the normal environment. For submergence events, we also look for evidence of standing water in unsealed electrical (e.g., light fixtures or electronic components such as relays). This evidence may include remaining standing water or an obvious water line within the components.  A final piece of evidence often evaluated is the presence of electrolytic corrosion, indicting direct water contact while under power (as discussed above). Although electrolytic corrosion may be pre-existing to some extent, there is again colour discrimination between recent (green) and longer term exposures (blue-green). In moulded case circuit breakers and switches, direct water exposure can affect the overall operation of the mechanism through corrosion, through the presence of foreign particles, and through removal of lubricants. The condition of the contacts can be affected and the dielectric insulation capabilities of internal materials can be reduced. Also, some moulded case circuit breakers are equipped with electronic trip units and the functioning of these trip units might be impaired. For fuses, the water may affect the filler material. A damaged filler material will degrade the insulation and interruption capabilities. These components are listed as required replacement when submerged in water. The same holds true for motor control switches.

3.2 - Classification of Hazardous Areas and Zoning.

Regulation 7 of the UK's Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) requires employers to classify places at the workplace where explosive atmospheres may occur into hazardous and non-hazardous areas. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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Hazardous areas are classified into zones. These are: 





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Zone 0: A place in which an explosive atmosphere consisting of a mixture with air of

dangerous substances in the form of gas, vapour or mist is present continuously or for long periods or frequently. Zone 1: A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapour or mist is likely to occur in normal operation occasionally. Zone 2: A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only. Zone 20: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously or for long periods or frequently. Zone 21: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally. Zone 22: A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

The hazardous area zone classification and corresponding equipment categories are:   

Zone 0 or zone 20: Category 1 equipment. Zone 1 or zone 21: Category 2 equipment. Zone 2 or zone 22: Category 3 equipment.

Hazardous areas are defined in DSEAR as "any place in which an explosive atmosphere may occur in quantities such as to require special precautions to protect the safety of workers". In this context, 'special precautions' is best taken as relating to the construction, installation and use of apparatus, as given in BS EN 60079 -101.  Area classification is a method of analysing and classifying the environment where explosive gas atmospheres may occur. The main purpose is to facilitate the proper selection and installation of apparatus to be used safely in that environment, taking into account the properties of the flammable materials that will be present. DSEAR specifically extends the original scope of this analysis, to take into account non-electrical sources of ignition, and mobile equipment that creates an ignition risk. Hazardous areas are classified into zones based on an assessment of the frequency of the occurrence and duration of an explosive gas atmosphere, as follows: 

 

Zone 0: An area in which an explosive gas atmosphere is present continuously or for long

periods. Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation. Zone 2: An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time.

Various sources have tried to place time limits on to these zones, but none have been officially adopted. The most common values used are:   

Zone 0: Explosive atmosphere for more than 1000h/yr. Zone 1: Explosive atmosphere for more than 10, but less than 1000 h/yr. Zone 2: Explosive atmosphere for less than 10h/yr, but still sufficiently likely as to require

controls over ignition sources.

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Where people wish to quantify the zone definitions, these values are the most appropriate, but for the majority of situations a purely qualitative approach is adequate. When the hazardous areas of a plant have been classified, the remainder will be defined as nonhazardous, sometimes referred to as 'safe areas'. The zone definitions take no account of the consequences of a release. If this aspect is important, it may be addressed by upgrading the specification of equipment or controls over activities allowed within the zone. The alternative of specifying the extent of zones more conservatively is not generally recommended, as it leads to more difficulties with equipment selection, and illogicalities in respect of control over health effects from vapours assumed to be present. Where occupiers choose to define extensive areas as Zone 1, the practical consequences could usefully be discussed during site inspection.

3.3 - The Use of Permits to Work in Hazardous Environments.

Hazardous environments pose particular dangers to those who need to carry out work in them. In most cases, a permit-to-work (PTW) system should be used to control maintenance operations in areas where dangerous substances are stored or are likely to be encountered. PTWs are formal management documents. They should only be issued by those with clearly assigned authority to do so, and the requirements stated in them must be complied with before the permit is issued and the work covered by it is undertaken. Individual PTWs need to relate to clearly defined individual pieces of work.  A permit-to-work system is a formal written system used to control certain types of work that are potentially hazardous. A permit-to-work is a document which specifies the work to be done and the precautions to be taken. Permits-to-work form an essential part of safe systems of work for many maintenance activities. They allow work to start only after safe procedures have been defined and they provide a clear record that all foreseeable hazards have been considered. PTWs should normally include:  

    

The location and nature of the work intended. Identification of the hazards, including the residual hazards and those introduced by the work itself. The precautions necessary, for example, isolations. The personal protective equipment required. The proposed time and duration of the work. The limits of time for which the permit is valid. The person in direct control of the work.

Information. Is the permit-to-work system fully documented, laying dow n:    



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How the system works. The jobs it is to be used for. The responsibilities and training of those involved. How to check its operation? Is there clear identification of who may authorise particular jobs (and any limits to their authority)? Is there clear identification of who is responsible for specifying the necessary precautions (e.g.

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   

isolation, emergency arrangements, etc.)? Is the permit form clearly laid out? Does it avoid statements or questions which could be ambiguous or misleading? Is it designed to allow for use in unusual circumstances? Does it cover contractors?

Selection and training: 

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 Are those who issue permits sufficiently knowledgeable concerning the hazards and precautions associated with the plant and proposed work? Do they have the imagination and experience to ask enough 'what if' questions to enable them to identify all potential hazards? Do staff and contractors fully understand the importance of the permit-to-work system and are they trained in its use? Description of the work. Does the permit clearly identify the work to be done and the associated hazards? Can plans and diagrams be used to assist in the description of the work to be done, its location and limitations? Is the plant adequately identified, e.g. by discrete number or tag to assist issuers and users in correctly taking out and following permits? Is a detailed work method statement given for more complicated tasks?

Hazards and precautions: 

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Does the system require the removal of hazards and, where this is not reasonably practicable, effective control?  Are the requirements of The Control of Substances Hazardous t o Health Regulations 1999 (COSHH) and other relevant legislation known and followed by those who issue the permits? Does the permit state the precautions that have been taken and those that are needed while work is in progress? For instance, are isolations specified and is it clear what personal protective equipment should be used? Do the precautions cover residual hazards and those that might be introduced by the work, e.g. welding fume and vapour from cleaning solvents? Do the Confined Spaces Regulations 1997 apply? If so, has a full risk assessment identified the significant risks and identified alternative methods of working or necessary precautions?

Procedures: 

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Does the permit contain clear rules about how the job should be controlled or abandoned in the case of an emergency? Does the permit have a hand-back procedure incorporating statements that the maintenance work has finished and that the plant has been returned to production staff in a safe state?  Are time limitations included and is shift changeover dealt with?  Are there clear procedures to be followed if work has to b e suspended for any reason? Is there a system of cross-referencing when two or more jobs subject to permits may affect each other? Is the permit displayed at the job?  Are jobs checked regularly to make sure that the relevant permit-to-work system is still relevant and working properly?

3.4 - Principles of Pressurising and Purging.

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It is accepted world-wide (using European Standards, NFPA or IEC Standards) and is relatively straightforward to comprehend. Explosion protection is achieved by keeping the potentially explosive atmosphere away from any source of ignition (thermal or electrical). The potentially ignition capable apparatus is mounted inside an enclosure, the enclosure is then pressurized to a positive pressure relative to the atmospheric pressure (a positive pressure of 0.5mbar is all that is required).  As long as this positive pressure is maintained, no gas (or even dust) will be able to enter the enclosure, hence the internal equipment can not be exposed to a potentially explosive gas. There is however a chance that an explosive gas mixture may have entered the enclosure prior to the positive pressure being achieved. To ensure that the enclosure is pressurized with a non-explosive gas (i.e.  Air or Nitrogen) the enclosure is 'purged' to flush out the existing contents and e nsure that all areas of the enclosure contain only the purging gas (purging of internal dusts have not yet been considered). It normally takes between 5 and 10 volume changes to ensure that the enclosure is 'purged'. (In Europe the first edition purge standard defined five air changes as a minimum, in North America the minimum is defined as 10 air changes). It is a condition of certification for Zone 1 equipment that power can not be applied to the equipment until the 'purging' (a specified flow of purging gas for a specified time) has been completed. To ensure continuity in the effect of the purging, the maximum leakage rate for the enclosure is also specified. When the purging has been completed, power can still not be applied until the specified positive pressure (at least 0.5 mbar) has been achieved. In the event of a failure to complete the purging cycle (drop in flow or incomplete duration) or if the enclosure pressure drops below the specified positive pressure, power to the equipment shall be removed (for Zone 1) or an alarm indication shall be given (Zone 2). In the event either of these conditions, the entire purging cycle starts again with the full purge time duration. The control of the automatic purging and pressurization is normally by a 'Purge Control Unit' (PCU). The PCU is required to measure flow and pressure, and must fail-safe in all conditions. The enclosure that houses the equipment to be purged must have sufficient physical integrity to withstand impacts and overpressures. The enclosure should also be designed to facilitate the free flow of air. As enclosure integrity is required to a level of IP40 (no holes greater than 1mm), any nonmetallic material must be tested for durability and longevity (against effects of heat and light etc.). External considerations, such as the surface temperature of the equipment or static from plastic parts, must be considered. To ensure incandescent particles can not be vented from the equipment, a spark arrestor must be fitted (or the vented gas must be ducted to a safe area). This technique is virtually unlimited particularly in physical size or power rating of the apparatus being protected. Purge control Units:

Purge control units must be able to measure and act on the following information:    

Pressure (pressurisation). Flow (purging). Time (Purging). The operations performed by the PCU must be 'failsafe' by virtue of test and assessment with one fault (i.e. a valve failing), this is even more prevalent with the advent of the ATEX Directive. Failure modes of components must be considered; even relays can fail open or short-circuit (normally open relays can 'arc-weld' in to a closed position). Purging timers must always re-set to zero if they are interrupted during the purging cycle or after a purge failure.

There are two basic types of control:

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

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Constant Flow (CF): The air flow for the purging and pressurization stages are the same. The

flow is left as a constant after it is set, and power is applied after a set period of time. Leakage Compensation (LC): After purging, the air flow is reduced to a figure just above the leakage level to maintain the pressurization. The PCU is required to switch from an initial high flow rate (often referred to as fast purge) to a much lower flow rate on completion of the purge time.

CF systems are simpler to design, but are more expensive (in air or nitrogen) to run. There are other examples of hybrid systems (CF/LC) but in reality they are just variations on the two basic types. PCUs are normally either pneumatic or electrical. If the PCU is mounted in the safe area only the operation will require verifying (unless it contains intrinsically safe outputs). PCUs mounted in the potentially explosive atmosphere will require certifying both as safety systems and as potential ignition sources (although sources of ignition from pneumatic systems were not considered until the ATEX Directive). Each STATE of the system is defined in response to the inputs of the monitoring devices. The states are required to be unique. The logical conditions for the occupation of each state are required to be uniquely defined by BOOLEAN logical expressions. All possible combinations of input conditions are required to be shown in a table. For maintenance purposes, it is necessary to work on the apparatus within the enclosure while the purge is off and the enclosure is open. Naturally, this is done under a gas clearance or hot work permit for safety but there are other safety implications which have to be taken into account. Once the enclosure has been opened the pressure switch will, via the control unit, cause the power to be isolated from the enclosure. Naturally power must be on so some means are required to by pass this function of the control system. One way of achieving this is to wire a keyoperated switch in parallel with the pressure switch. It must be ensured that the purge cycle reinitiates before power is applied again. Standards and Certification:

The methodology for designing and testing a purged and pressurized enclosure has been defined in many Standards and specific industry codes of practice. The two most commonly used Standards are: CENELEC Purge Standard:

The standard in Europe for the last 20 years has been the CENELEC standard EN 50016: 1977 which in turn is based on a part of IEC-79 published in 1975. The significant features of this standard are:    



 Automatic initial purge. Verification (by test or assessment) of initial purge by flow and time. Manual operation of the purging system is not permitted (it is in the IEC Standard).  A replacement standard for what has become known as 't he first edition' purge standard was issued in 1996. This is now the standard that is used for certification. BS EN 50016:1996.

The new standard for pressurized apparatus is far more substantial than the 'first edition' and contains more mandatory requirements. The key changes are:

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     

Static pressurization. Purge control requirements (including flow measurement, truth tables etc.). Source or release covered. Purge testing is mandatory and the test is defined.  A minimum of 5 volume changes is no longer mandatory. Leakage tests are required.

This 'Second Edition' Standard is currently being used for European Certification, although the vast majority of certified purged equipment is only certified against the requirements of the 'First Edition'.

Zoning Requirements. 

 

The European pressurisation standard does not indicate the zone of use of the purged apparatus. This is defined in the 'Code of Practice'. Purge can be used in Zone 1 or Zone 2. Zone 1: Power must be automatically removed if pressurization fails. Zone 2: An alarm must be raised (as a minimum) if pressurisation fails.

Most commercially available purge control units have options for 'alarm' and 'alarm and trip' so that the user can select the appropriate measures. Practical implementation: Enclosures:

 A standard IP54 enclosure may not be suitable for use as a pressurized enclosure because the sealing is in the wrong direction. The standard enclosure is designed to prevent the external environment entering the enclosure which means that they are generally unsuitable for retaining internal pressure. For this reason enclosures from suppliers of pressurized systems are not generally the same as general-purpose enclosures. Also, the enclosure must be able to maintain the pressure, on large enclosures the unit can be seen to deform even with relatively low pressures. Additional hinges and cover bolts may be required when the pressure is acting on a large surface area. Plastic parts (e.g. switches) should not penetrate the housing walls. Plastic parts may be used externally if, when the plastic is removed, metal parts remain that provide an ingress protection rating of IP40 (no objects greater than 1 mm can penetrate the enclosure). No live (or potentially live) parts should be exposed outside of the purged area. As switches are normally sealed devices that contain sparking contacts, it is preferable to either use certified switches or mount the switches inside the purged enclosure. Plastic ducting should not be used if the plastic part failing does not create a fail-safe condition, e.g. on the secondary purge system. Supply and Return of Purging Medium:

Special precautions are needed where the pressurization method uses a fan or blower. It is generally undesirable to put the fan in a hazardous area because this means that the ducting, which extends to a non-hazardous area, will be below atmospheric pressure and, unless it is completely leak tight, may draw in flammable gases. The other advantages of putting the fan in the non- hazardous area is that it does not need to be suitable for use in hazardous area itself and the ducting is under positive pressure which prevents ingress of flammable gas. The use of compressed air is the normal method of supplying purge air, it must be noted that several purged enclosure on one supply line may drop the operational pressure to below working levels for the SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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pneumatic logic, if such a system is used. The exhausted air from a purged enclosure may contain small particles that have been heated by the internal sources of the enclosure. To prevent these particles being vented into the potentially explosive atmosphere the following methods are used:  

Spark arrestors on the air outlet. Ducting (to a safe area) on the air outlet.

Pressurisation:

The minimum pressure required is 0.5 mbar (50 Pa or 0.2" w.g.) and this should be achieved with the lowest possible flow of pressurizing gas. The pressure measurement has to at least raise an alarm if the pressure falling below this level so that the working pressure will be above this. The enclosure has be tested to prove it will withstand 1.5 times its normal working pressure (minimum 200 Pa) for 2 minutes without distortion, a figure of 10 mbar is not uncommon as a working pressure. Purging: Effective purging of the enclosure and its contents has to be provided. As a guideline, 5 volume changes are generally sufficient if the enclosure has been designed to a few basic guidelines:    

 Avoid air traps (pockets).  Avoid 'channelling' of the purging air. Create turbulence.  Avoid sealed volumes.

Temperature Classification:

Since the flammable gas is prevented from entering the enclosure the exterior of the enclosure determines the temperature classification. It is to be noted, however, that internal hot surfaces will remain hot even after the power has been removed. A full assessment of the thermal properties of hot parts of a purged enclosure must be conducted. Internal Energy Storage:

For things such as capacitors in power supplies this often means either waiting until the charge has leaked away before the enclosure is opened or fitting bleed resistors to ensure it happens. Batteries cannot be dealt with in this w ay and invariably have to be protected by one of the other methods, a draft standard for batteries in purged equipment outlines the methodology:   

Test the battery to get the 'worst case' output parameters. Ensure the output is non-incendive.  Assess the capacitance and inductance to which the battery is connected.

Pressurized and Purged Enclosure with Internal Source of Release:

The primary objective here is to prevent a flammable atmosphere from occurring within the enclosure. This can be achieved either by continuous dilution or by the use of inert gas. If the quantity of the internal source of release can be defined and controlled, dilution can be used. If the quantity of release can not be defined, inert gas must be used. In either case an initial purge is still required; SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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where air is the purging medium the intent is to dilute any flammables below the lower flammable limit. In the case of inert gas the intent is to render the interior of the enclosure non-flammable by the removal of oxygen. For obvious reasons, apparatus capable of igniting a flammable gas must not be located in the dilution zone of a possible release. Certification and Testing:

Pressurized equipment can be 'self certified' for Zone 2. If the pressurized equipment is designed to be used in a Zone 1 atmosphere then it must be certified through a European Notified Body. The certification process involves an assessment of the sample against the provided drawings (to ensure that the constructional requirements have been met and that the sample is a representative test sample) and a series of tests. The exact nature and type of testing conducted will vary from product to product, but will typically be as indicated below. Test Standard:           

Impact test on enclosure EN50 014. Impact test on glass (x3) EN50 014. Thermal shock on glass EN50 014. Purge test (Argon and Helium) EN50 016. Overpressure test EN50 016. Leakage test EN50 016. Low pressure test EN50 014. Temperature rise test EN50 014. Thermal decay test EN50 014. Secondary purge test EN50 016. Dilution test EN50 016.

The level of 'impact' for the impact test can vary depending on the material and the risk of impact. Plastic materials require pre-conditioning before impacting, and the impact test is conducted with the plastic parts at high and low temperatures. Plastic parts that penetrate the enclosure may also require resistance to light testing. Purge Verification Tests:

The test is normally conducted by filling the enclosure with representative test gasses (Argon and Helium are used to represent heavy and light explosives gasses) and physically measuring the removal from the enclosure when the inert purge gas is applied. The actual gas that will be present where the equipment will be used can be used, but Argon and Helium are normally used as they cover all possible flammable gas atmospheres. The test is carried out by positioning small bore tubes in the purge cabinet at positions likely to 'pocket' and measuring the actual content of test gas. Initially the cabinet must be at least 70% full of the test sample to be removed. The test sample is then removed by air purging until acceptable levels (based on the LEL) have been reached. The time taken to remove the test gasses from the enclosure is referred to as the 'purge time', and will be marked on the certification label and conducted prior to pressurizing the enclosure and applying power. The purge time will be dependent on the rate of flow of purging gas and internal geometry of the enclosure to be purged. By ventilation and a considered approach to the internal configuration, purge SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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times can be greatly reduced (reducing the downtime of equipment before power can be applied). There is not a linear relationship between purge times and purge flow rate, i.e. doubling the air flow will not necessarily half the purge time. Other types of pressurization: Static Pressurization: 

  



 

Static pressurization relies on the enclosure being pressurized with an inert gas and having a sealed enclosure to maintain the pressurization. The protective gas shall be inert. Internal sources of release of flammable substances are not permitted. The pressurized enclosure shall be filled with inert gas in a non-hazardous area using the procedure specified by the manufacturer. Two automatic safety devices shall be provided to operate when the overpressure falls below the minimum value specified by the manufacturer. The automatic safety devices shall only be capable of being reset by the use of a tool or a key. The purpose for which the automatic safety devices are used (i.e. to disconnect power or to sound an alarm or otherwise ensure safety of the installation) is the responsibility of the user.

Pressurized and Purged Enclosure with People Working Inside (Purged rooms):

Naturally inert gas cannot be used and compressed air is not generally recommended. In addition, emergency facilities for the personnel are required. Lighting and means of escape are of prime importance. The lighting is required under all circumstances and hence must be protected by some other suitable means such as flameproof. Kick-out panels or crash bars on doors usually provide for escape.

3.5 - Intrinsically Safe Equipment.

Intrinsically safe equipment is defined as "equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmosphere mixture in its most easily ignited concentration" In simple terms this means that intrinsically safe equipment and wiring limits electrical and t hermal energy to a level below that required to cause an explosion. Intrinsic-safety equipment operates on lower power levels so there is no shock hazard due to excess thermal energy and arcing. Safety barriers are grounded to be effective under fault conditions, intrinsic safety is provided through voltage and current limiters. Zener diodes and resistors that provide this limiting are usually mounted away from hazardous areas. Failure to replace enclosure covers or bolts will not imperil protection. Intrinsically safe systems tend to be small and do not require expensive, bulky accessories such as explosion-proof enclosures, seals and rigid metallic conduits, a design that generally makes easy handling and installation. Explosion-proof enclosures and conduit are no longer necessary, so labour and material costs are lower. Equipment can be calibrated and maintained without disconnecting power, which means easier maintenance and decreased down time. Field instruments may be maintained and calibrated with power applied, thereby minimising downtime. Since properly installed intrinsic-safety circuits and equipment reduce the probability of explosion to SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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practically zero, insurance rates tend to be lower; especially where local ordinance requires hazardous facilities to carry special liability insurance. The principle of an intrinsically safe fire detection system are virtually identical to those of regular detection systems and may include smoke detection devices as well as special-purpose detectors such as flame detectors, heat detectors, air sampling etc. Intrinsically safe wiring must be separated from non-intrinsically safe wiring by at least 2 inches in order to prevent the transfer of unsafe levels of energy to the hazardous area and it is vital therefore that planning and installation of such systems are undertaken with utmost care and attention. Intrinsically safety can be compromised after initial installation due to improper maintenance or repair and it is important to ensure such works are always carried out by specialists. Flameproof : 





Code d: This type of equipment will have a CENELEC Hexagon followed by apparatus group

and Safety Category. This means that the equipment is robust can stand an explosion from within, without transmitting the flame to the outside. Equipment has flameproof gaps (max 0.006" propane /ethylene, 0.004" acetylene /hydrogen). It can be used in Zone 1 if gas group & temperature class are correct, and in motors, lighting and junction boxes.

Non Incendive: 

Code n: This type of equipment is now CENELEC recognised, so it will have a hexagon



followed by apparatus group and Safety Category. The equipment is non-incendive or non-sparking and can be used in Zone 2. It is used in motors, lighting, junction boxes and electronic equipment.

Increased Safety: 

Code e: This type of equipment will have a CENELEC Hexagon followed by apparatus group



and Safety Category. This type of equipment is very robust and components are made to a high quality. It is used in motors, lighting and junction boxes.

3.6 - The ATEX Directive.

The ATEX directive consists of two EU directives describing what equipment and work environment is allowed in an environment with an explosive atmosphere. ATEX derives its name from the French title of the 94/9/EC directive: 

 Appareils destinés à être utilisés en ATmosphères EXplosibles.

Directives:

The CE mark which should be attached to EU certified equipment. As of July 2006, organisations in the EU must follow the directives to protect employees from explosion risk in areas with an explosive atmosphere.

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There are two ATEX directives (one for the manufacturer and one for the user of the equipment): 

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The ATEX 95 equipment directive 94/9/EC, Equipment and protective systems intended for use in potentially explosive atmospheres. The ATEX 137 workplace directive 99/92/EC, Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.

Employers must classify areas where hazardous explosive atmospheres may occur into zones. The classification given to a particular zone, and its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does.  Areas classified into zones (0, 1, 2 for gas-vapor-mist and 20, 21, 22 for dust) must be protected from effective sources of ignition. Equipment and protective systems intended to be used in zoned areas must meet the requirements of the directive. Zone 0 and 20 require Category 1 marked equipment, zone 1 and 21 required Category 2 marked equipment and zone 2 and 22 required Category 3 marked equipment. Zone 0 and 20 are the zones with the highest risk of an explosive atmosphere being present. Equipment in use before July 2003 is allowed to be used indefinitely, provided a risk assessment shows it is safe to do so. The aim of directive 94/9/EC is to allow the free trade of 'ATEX' equipment and protective systems within the EU by removing the need for separate testing and documentation for each member state. The regulations apply to all equipment intended for use in explosive atmospheres, whether electrical or mechanical, including protective systems. There are two categories of equipment I for mining and II for surface industries. Manufacturers who apply its provisions and affix the CE marking and the Ex marking are able to sell their equipment anywhere within the European union without any further requirements being applied with respect to the risks covered being applied. The directive covers a large range of equipment, potentially including equipment used on fixed offshore platforms, in petrochemical plants, mines, flour mills and other areas where a potentially explosive atmosphere may be present. In very broad terms, there are three preconditions for the directive to apply: the equipment a) must have its own effective source of ignition; b) be intended for use in a potentially explosive atmosphere (air mixtures); and c) be under normal atmospheric conditions. The directive also covers components essential for the safe use and safety devices directly contributing to the safe use of the equipment in scope. These latter devices may be outside the potentially explosive environment. Manufacturers/suppliers (or importers, if the manufacturers are outside the EU) must ensure that their products meet essential health and safety requirements and undergo appropriate conformity procedures. This usually involves testing and certification by a 'third-party' certification body (known as a Notified Body e.g. Baseefa, Sira, Lloyd's, TUV) but manufacturers/suppliers can 'self-certify' Category 3 equipment (technical dossier including drawings, hazard analysis and users manual in the local language) and Category 2 non-electrical equipment but for Category 2 the technical dossier must be lodged with a notified body. Once certified, the equipment is marked by the 'CE' (meaning it complies with ATEX and all other relevant directives) and 'Ex' symbol to identify it as approved under SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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the ATEX directive. The technical dossier must be kept for a period of 10 years. Certification ensures that the equipment or protective system is fit for its intended purpose and that adequate information is supplied with it to ensure that it can be used safely. There are four ATEX classification to ensure that a specific piece of equipment or protective system is appropriate can be safely used in a particular application:    

Industrial or Mining Application. Equipment Category.  Atmosphere. Temperature.

Effective ignition source:

Effective ignition source is a term defined in the European ATEX directive as an event which, in combination with sufficient oxygen and fuel in gas, mist, vapour or dust form, can cause an explosion. Methane, hydrogen or coal dust are examples of possible fuels. Effective ignition sources are:   

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Lightning strikes. Open flames. This varies from a lit cigarette to welding activity. Mechanically generated impact sparks.  For example, a hammer blow on a rusty steel

surface compared to a hammer blow on a flint stone. The speed and impact angle (between surface and hammer) are important; a 90 degree blow on a surface is relatively harmless. Mechanically generated friction sparks. The combination of materials and speed determine the effectiveness of the ignition source. For example 4.5 m/s steel-steel friction with a force greater than 2 kN is an effective ignition source. The combination of aluminium and rust is also notoriously dangerous. More than one red hot spark is often necessary in order to have an effective ignition source. Electric sparks. For example a bad electrical connection or a faulty pressure transmitter. The electric energy content of the spark determines the effectiveness of the ignition source. High surface temperature. This can be the result of milling, grinding, rubbing, mechanical friction in a stuffing box or bearing, or a hot liquid pumped into a vessel. For example the tip of a lathe cutting tool can easily be 600 degrees Celsius (1100 °F); a high pressure steam pipe may be above the autoignition temperature of some fuel/air mixtures. Electrostatic discharge.  Static electricity can be generated by air sliding over a wing, or a non-conductive liquid flowing through a filter screen. Radiation. Adiabatic compression. Air is pumped into a vessel and the vessel surface heats up.

4 - Emergency Planning. Definition of an emergency: 'An event which necessitates a rapid and more or less complex response in order to minimise losses.' 

Other useful definitions are as follows: 

Incident: Any undesired event or occurrence.

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

Accident: Any incident that leads to personal injury. We can distinguish the idea of an



accident. from those incidents that 'only' cause damage or loss to plant or equipment or part of a building. Crisis: The time during which there is intense difficulty or danger. Disaster : An accident or natural catastrophe that causes great damage or loss of life. Catastrophe: A type of crisis, but of greater severity.

 

Emergency planning requires: 





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Identification of the events which could lead to an emergency and identification of the activities required by way of a response to the emergency and the time-scales for these activities. Major emergencies that cause serious injuries to many people, or perhaps damage to a building are thankfully extremely rare in most organisations. That this is so is partly a matter of luck and partly because many serious risks can be anticipated. Business as a whole has both a moral and a legal duty to have in existence contingency plans to cope with foreseeable emergencies. The Health and Safety at Work Act 1974 requires the employer to do everything it can to protect its staff and members of the general public against foreseeable hazards. There are other, more specific requirements given in Regulations under the Act. Regulation 8 of the Management of Health and Safety at Work Regulations requires organisations to, 'establish procedures to be followed in the event of serious and imminent danger to persons at work'. There are similar obligations under the Control of Substances Hazardous to Health Regulations 2002 and the Dangerous Substances and Explosive Atmospheres Regulations 2002 that are specific to work with chemical and biological hazards.

In summary, what organisations are required to do is:      

 Assess the potential for 'serious and imminent danger'. Take steps to minimise the likelihood of this danger being realised. Plan for credible eventualities. Train staff to cope or evacuate. Rehearse the coping strategy so its efficacy can be determined, and improve it if necessary. Pass on vital information to the Emergency Services.

Further information regarding Regulation 8 of the Management of Health and Safety at Work Regulations 1999 is as follows: Management Regulation 1999: 

Regulation 8: Procedures for serious and imminent danger and for danger areas.

(1) Every employer shall: a). Establish, and where necessary give effect to, appropriate procedures to be followed in the event

of serious and imminent danger at work in his undertaking. b). nominate a sufficient number of competent persons to implement those procedures in so far as they relate to the evacuation from premises of persons at work in his undertaking. c). ensure that none of his employees has access to any area occupied by him to whom it is necessary to restrict access on grounds of health and safety unless the employee concerned has received adequate health and safety instruction. (2) Without prejudice to the generality of paragraph (1)(a), the procedures referred to in that sub-paragraph shall:

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a) So far as is practicable, require any persons at work who are exposed to serious and imminent

danger to be informed of the nature of the hazard and of the steps taken or to be taken to protect them from it. b) Enable the person concerned (if necessary by taking appropriate steps in the absence of guidance or instruction and in the light of their knowledge and the technical means at their disposal) to stop work and immediately proceed to a place of safety in the event of their being exposed to serious, imminent and unavoidable danger. c) Save in exceptional cases for reasons duly sustained (which cases and reasons shall be specified in those procedures), requires the persons concerned to be prevented from resuming work in any situation where there is still a serious and imminent danger. (3) A person shall be regarded as competent for those purposes of paragraph (1) where he has sufficient training and experience or knowledge and other qualities to enable him properly to implement the evacuation procedures referred to in that sub-paragraph.

4.1 - Identification of Events. Events that could be construed as an emergency will have one or more of the following: 





They require the rapid deployment of resources that would not normally be provided as part of the core activities of the organisation. They require the use of competencies which would not normally be provided as part of the core activities of the organisation. They require a rapid series of concerted actions that it would not be realistic to work out within the time-scales required.

1. They require the rapid deployment of resources that would not normally be provided as part of the core activities of the organisation: Such as:    

Spillage kits. Emergency Showers. Fire fighting equipment. Special arrangements and training would be required in order to 'rapidly deploy' such equipment in an effective and controlled manner.

2. They require the use of competencies which would not normally be provided as part of the core activities of the organisation. Competencies can be:    

Knowledge of evacuation procedures. Knowledge of dealing with major spillages. Dealing with public relations.  Again, special arrangements and training need to be considered in order to have these competencies.

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Any such actions would include:    

Evacuation of personnel. Evacuation of members of the public. Keeping relevant people informed. Special arrangements must be made so that these actions can be planned for in advance.

4.2 - Emergency Plans. An organisation's emergency plan can be divided into several phases: Area

Notes

Risk assessment.

This is the process of examining the hazards inherent in a place, activity or substances(s), and deciding if the safeguards are sufficient, or if more needs to be done.

Prevention.

While some risks can be eliminated, others cannot. Thereafter, we must suppress the adverse outcome(s) or reduce these effects by warning people nearby.

Preparation.

The emergency plan can then be prepared to address identified risks. The main elements of the plan should cover: Communication: Call-out procedures for key

personnel and subsequently all those affected by the emergency. Co-ordination: The reporting structures during the emergency period and ownership of the plans Control: The leadership personnel, their roles, responsibilities and objectives at each phase of the emergency Resources:  Where these are located; if these are not readily obtainable, it may be necessary to preposition these in readiness Testing and Training: Senior management and those with key responsibilities. Response.

For example, the response process will be critical and a simple plan can be used to assign actions to the following elements: 

Detection.

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 Alarm. Evacuation. Containment. Restoration.

If the emergency is very minor or localised, restoration might be immediately effective in returning activities to normal. For example, after a false fire alarm, the Fire Brigade could inspect the site and confirm the nature of the alert and declare re-entry to the building safe.  All that is required here is to make this precondition for restoration of conditions clear to all. In more serious emergencies, considerable planning may be necessary before normal working can resume.

Recovery.

This can involve:     

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Clearing away of debris. Removal and treatment of casualties. Cordoning off any damaged areas. Cleaning affected areas. Testing, and if necessary restoring, environmental and engineering services. Investigating the cause(s) of the incident.

In order to complete this, the employer needs to understand the significance of Regulation 5 of the Management of Health and Safety at Work Regulations 1999.

4.3 - Management Regulations 1999. Regulation 5: Health and Safety Arrangements: (1) Every employer shall make and give effect to such arrangements as are appropriate, having

regard to the nature of his activities and the size of his undertaking, for the effective planning, organisation, control, monitoring and review of preventative and protective measures. (2) Where the employer employs five or more employees, he shall record the arrangements referred to in paragraph (1)(above). Notes to Regulation 5: 

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This regulation requires employers to have arrangements in place to cover health and safety. Effective management of health and safety will depend upon, amongst other things, a suitable and sufficient risk assessment being carried out and the findings being used effectively. The health and safety arrangements can be integrated into the management system for all other aspects of the organisation's activities. The management system adopted will need to reflect the complexity of the organisation's activities and working environment.

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Where the work process is straightforward and the risks generated are relatively simple to control, then very straightforward management systems may be more appropriate.  Although the principles of the management arrangemen ts are the same, irrespective of the size of an organisation, - the key elements of such effective systems can be found in HSG65 or BS8800.

A successful health and safety management system will include all the following elements: Planning:

Employers should set up an effective health and safety management system to implement their health and safety policy that is proportionate to the hazards and risks. Adequate planning includes: A: Adopting a systematic approach to the completion of a risk assessment.

Risk assessment methods should be used to decide on priorities and to set objectives for eliminating hazards and reducing risks. This should include a programme, with deadlines for the completion of the risk assessment process, together with suitable deadlines for the design and implementation of the preventative and protective measures that are necessary. B: Selecting appropriate methods of risk control to minimise risks. C: Establishing priorities and developing performance standards both for the completion of risk assessments(s) and the implementation of preventative and protective measures, which at each stage minimise the risk of harm to people. Wherever possible, risks are eliminated through selection and design of facilities, equipment and processes. Organisation: This includes: A: Involving employees and their representatives in carrying out risk assessments, deciding on

preventative and protective measures and implementing those requirements in the workplace. This may be achieved by the use of formal health and safety committees where they exist, and by the use of team-working, where employees are involved in deciding on the appropriate preventative and protective measures and written procedures etc. B: Establishing effective means of communications and consultation in which a positive approach to health and safety is visible and clear. The employer should have adequate health and safety information and make sure it is communicated to employees and their representatives, so informed decisions can be made about the choice of preventative and protective measures. Effective communication will ensure that employees are provided with sufficient information so that control measures can be implemented effectively. C: Securing competence by the provision of adequate information, instruction and training and its evaluation, particularly for those who carry out risk assessment and make decisions about preventative and protective measures. Where necessary this will need to be supported by the provision of adequate health and safety assistance or advice.

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Control: Establishing Control includes: A: Clarifying health and safety responsibilities and ensuring that the activities of everyone are well

coordinated. B: Ensuring everyone with responsibilities understands clearly what they have to do to discharge their responsibilities, and ensure they have the time and resources to discharge them effectively. C: Setting standards to judge the performance of those with responsibilities and ensure they meet them. It is important to reward good performance as well as to take action to improve poor performance. D: Ensuring adequate and appropriate supervision, particularly for those who are learning and who are new to a job. Monitoring:

Employers should measure what they are doing to implement their health and safety policy, to assess how effectively they are controlling risks, and how well they are developing a positive health and safety culture. Monitoring includes: A: Having a plan and making adequate routine inspections and checks to ensure that preventative

and protective measures are in place and effective.  Active monitoring reveals how effectively the health and safety management system is functioning. B: Adequately investigating the immediate and underlying causes of incidents and accidents to ensure

that remedial action is taken, lessons are learnt and longer-term objectives are introduced. In both cases, it may be appropriate to record and analyse the results of monitoring activity, to identify any underlying themes or trends which may not be apparent from looking at events in isolation. Review: Review involves: A: Establishing priorities for necessary remedial action that were discovered as a result of monitoring

to ensure that suitable action is taken in good time and is completed. B: Periodically reviewing the whole of the health and safety management system, including the elements of planning, organisation, control and monitoring to ensure that the whole system remains effective. Consulting employees or their representatives about matters to do with their health and safety is good management practice, as well as being a requirement under health and safety law. Employees are a valuable source of information and can provide feedback about the effectiveness of health and safety management arrangements and control measures. Where safety representatives exist, they can act as an effective channel for employee's views. Safety representatives' experience of workplace conditions and their commitment to health and safety means they often identify potential problems, allowing the employer to take prompt action. They can also have an important part to play in explaining safety measures to the workforce and gaining SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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commitment.

4.4 - Minimisation of Consequences via Emergency Procedures.

Emergency procedures are not just a business risk management function; they are also a legal requirement. The Management of Health and Safety Regulations 1999, Regulation 7, calls for health and safety assistance and sets out minimum requirements and standards to be met: Regulation 7: Health and Safety Assistance: (1) Every employer shall, subject to paragraph (6) and (7), appoint one or more competent persons to

assist him in undertaking the measures he needs to take to comply with the requirements and prohibitions imposed upon him by or under the relevant statutory provisions and by the Regulatory Reform (Fire Safety) Order 2005. (2) Where an employer appoints persons in accordance with paragraph (1), he shall make

arrangements for ensuring adequate co-operation between them. (3) The employer shall ensure that the number of persons appointed under paragraph (1), the time

available for them to fulfil their functions and the means at their disposal are adequate, having regard to the size of his undertaking, the risks to which his employees are exposed and the distribution of those risks throughout the undertaking. (4) The employer shall ensure that: a) Any person appointed by him in accordance with paragraph (1) who is not in his employment.

Is informed of the factors known by him to affect, or suspected by him of affecting, the health and safety of any other person who may be affected by the conduct of his undertaking, and has access to the information referred to in regulation 10 (Information for employees) b) Any person appointed by him in accordance with paragraph (1) is given such information about any person working in his undertaking who is: Employed by him under a fixed term contract of employment, or employed in an employment business as is necessary to enable that person properly to carry out the functions specified in that paragraph. (5) A person shall be regarded as competent for the purposes of paragraphs (1) and (8) where he has

sufficient training and experience, or knowledge and other qualities to enable him properly to assist in undertaking the measures referred to in paragraph (1). (6) Paragraph (1) shall not apply to a self-employed employer who is not in partnership with any other

person where he has sufficient training and experience or knowledge and other qualities properly to undertake the measures referred to in that paragraph himself. (7) Paragraph (1) shall not apply to individuals who are employers and who are together carrying on

business in partnership where at least one of the individuals concerned has sufficient training and experience or knowledge and other qualities: 

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Properly to undertake the measures he needs to take to comply with the requirements and prohibitions imposed upon him by or under the relevant statutory provisions, and Properly to assist his fellow partners in undertaking the measures they need to take to comply

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with the requirements and prohibitions imposed upon them by or under the relevant statutory provisions. (8) Where there is a competent person in the employer's employment, that person shall be appointed

for the purposes of paragraph (1) in preference to a competent person not in his employment. Notes: 

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Employers are solely responsible for ensuring that those they appoint to assist them with health and safety measures are competent to carry out the tasks they are assigned, and are given adequate information and support. In making decisions on whom to appoint, employers themselves need to know and understand the work involved, the principles of risk assessment and prevention, and current legislation and health and safety standards. Employers should ensure that anyone they appoint is capable of applying the above to whatever task they are assigned. Employers must have access to competent help in applying the provisions of health and safety law. In particular, they need competent help in devising and applying protective measures, unless they are competent to undertake the measures without assistance.  Appointment of competent people for this purpose should be included among the health and safety arrangements recorded under regulation 5(2). Employers are required by the Safety Representatives and Safety Committees Regulations 1977 to consult in good time on arrangements for the appointment of competent assistance. When seeking competent assistance, employers should look to appoint one or more of their employees, with the necessary means, or themselves, to provide the health and safety assistance required. If there is no relevant competent worker in the organisation, or the level of competence is insufficient to assist the employer in complying with health and safety law, the employer should enlist an external service or person.

In some circumstances a combination of internal and external competence might be appropriate, recognising the limitations of the internal competence. Some regulations contain specific requirements for obtaining advice from competent people to assist in complying with legal duties. For example, the Ionising Radiation Regulations requires the appointment of a radiation protection adviser in many circumstances, where work involves ionising radiation. Employers who appoint doctors, nurses or other health professionals to advise them of the effects of work on employee health, or to carry out certain procedures, for example health surveillance, should first check that such providers can offer evidence of a sufficient level of expertise, or training in occupational health. Registers of competent practitioners are maintained by several professional bodies, and are often valuable. The appointment of such health and safety assistants or advisers does not absolve the employer from responsibilities for health and safety under the Health and Safety at Work Act 1974 and other relevant statutory provisions and under the Regulatory Reform (fire Safety) Order 2005 It can only give added assurance that these responsibilities will be discharged adequately. Where external services are employed, they will usually be appointed in an advisory capacity only. Competence in the sense it is used in these Regulations does not necessarily depend on the possession of particular skills or qualifications. Simple situations may require only the following: 

 An understanding of relevant current best practice.

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 An awareness of the limitations of one's own experience a nd knowledge. The willingness and ability to supplement existing experience and knowledge, when necessary by obtaining external help and advice. More complicated situations will require the competent assistant to have a higher level of knowledge and experience. More complex or highly technical situations will call for specific applied knowledge and skills which can be offered appropriately qualified specialists.

Employers are advised to check the appropriate health and safety qualifications (some of which may be experienced-based and/or industry-specific), or membership of a professional body or similar organisation (at an appropriate level and in an appropriate part of health and safety) to satisfy themselves that the assistant they appoint has a sufficiently high level of competence.

4.5 - Development of Emergency Plans. Integrated Emergency Management :

The basis of emergency planning and response is now known as Integrated Emergency Management. Under the principles of integrated emergency management, the response to an emergency should concentrate on the effects rather than the cause of the disaster and, wherever possible, should be planned and undertaken as an extension of normal day-to-day activities. The underlying aim of the planning process should be to develop flexible arrangements which will enable agencies to deal with any crisis, whether foreseen or unforeseen. Integration in emergency management must be applied at every stage if it is to be fully effective, although the practical arrangements at each stage may vary. The main stages usually identified are as follows: Prevention:

This phase encompasses measures which are adopted in advance of an emergency, and which seek to prevent it occurring or to reduce its severity. Preparedness:

This is "the insurance policy" consisting of preparation to respond to known hazards and risks as well as to unforeseen events. Planning can be underpinned by training and exercises. Response:

The initial response is normally provided by the statutory emergency services, supported as necessary by the appropriate local authorities, public and private agencies and voluntary organisations. The basic objectives of the response, which will vary according to the circumstances of the event, will be to preserve life, property and the environment; to reduce to a minimum the harmful effects of the event, to prevent its escalation; and to facilitate criminal investigations and other inquiries; all without prejudicing as rapid as possible a return to normal life. Recovery:

This encompasses those activities necessary to provide a rapid return to normality, both for the community and for those supporting and serving it.  As regards response to disaster, there is no one model; the respo nse will need to vary just as the nature and effects of the disaster will vary. Nevertheless, any response has to be an integrated operation, and certain other features will be common in the response to many disasters. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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Some key features addressed in this chapter are: 

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The core of the initial response will normally be provided by the emergency services, supported by the appropriate local authority or authorities, public and private agencies and voluntary organisations. The basic objectives of the integrated response will be similar on each occasion. The same basic management structure will be applicable. There will be a need to ensure that essential records are kept for debriefings, formal inquiries and disseminating information about the lessons learnt.

The initial response to a disaster is usually provided by the emergency services. They can provide a rapid response and alert local authorities and other services as soon as possible.  All organisations which need to respond quickly to a disaster should have arrangement s that can be activated at short notice. These arrangements should be clearly established and promulgated. Single service guidance documents have already been produced by, or for, a number of services. This chapter draws on them to offer guidance on how the procedures and operations of each of the organisations involved can be integrated to provide an efficient and effective response to disaster.

4.6 - Service/Agency Disaster Roles and Functions. The Police Service.

The police co-ordinate the activities of all those responding at and around the scene (except insofar as the fire service has such responsibility within the inner cordon - see below). Unless a disaster has been caused by severe weather or other natural phenomenon, the area concerned must be treated as the scene of a crime and preserved accordingly. The police oversee any criminal investigation. They also facilitate inquiries carried out by the responsible accident investigation body, such as the Health and Safety Executive, Railway Inspectorate or the Air or Marine Accident Investigation Branch. The police process casualty information and have responsibility for identifying and arranging for the removal of the dead. In this task they act on behalf of the Coroner (Procurator Fiscal in Scotland) who has the legal responsibility for investigating the cause and circumstances of deaths arising from a disaster. The Fire Service.

The concerns of the fire service are the saving of life in conjunction with other emergency services, the rescue of trapped casualties, tackling fire and, as necessary, released chemicals or other hazards, and assisting the police and ambulance services with casualty handling and recovery of bodies. The fire service is also normally best placed to advise on the safety of personnel of all agencies involved within the inner cordon; and it will gather information on chemical hazards via the UK databases - Chemdata and Chemnet. NHS.

The ambulance service provides the first NHS response at the scene. Immediate care for the injured and their evacuation to hospital are its tasks, together with the mobilisation of further NHS resources required at the scene. These will include a Medical Incident Officer and such other doctors, nurses and equipment as the situation demands. Overall co-ordination of NHS activity, whether at the scene, in hospitals or elsewhere in the community to meet healthcare needs arising from the emergency is the responsibility of the Health Board. SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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HM Coastguard.

HM Coastguard Agency comprises two main elements: HM Coastguard and the Marine Pollution Unit. The primary responsibility of HM Coastguard is to initiate and co-ordinate civil maritime search and rescue. This includes mobilising, organising and dispatching resources to assist people in distress at sea, or in danger on the cliffs or shoreline. The Marine Pollution Unit is r esponsible for dealing with pollution at sea and for co-ordinating the shoreline clean-up. Local Authorities.

In the immediate aftermath of a disaster, the principal concerns of local authorities include support for the emergency services, support and care for the local and wider community, use of resources to mitigate the effects of the emergency and co-ordination of the response by organisations other than the emergency services.  As time goes on, and the emphasis switches to recovery, the local authority will take a leading role in rehabilitating the community and restoring the environment. Industry/Commercial Organisations and Utilities.

It should be remembered that industrial or commercial organisations, and the utilities, may play a direct part in the response to disaster if their personnel, operations or services have been involved. Other industries or commercial organisations may provide support through local partnerships in which, for example, they provide equipment, services or specialist knowledge. The Community.

The community can contribute to a wide range of activities, either as members of a voluntary organisation or as individuals. Military.

Military assistance may be used in support of local response. This has been an important part of many disaster responses in the past. The roles and responsibilities of the organisations/agencies described have to be set in the context of the objectives of the disaster response. All services and agencies responding to a disaster should be working, notwithstanding their particular responsibilities, to these common objectives. They are:     

To preserve life, property, and the environment. To reduce to a minimum the harmful effects of an emergency and prevent its escalation. To facilitate criminal investigations and judicial, public, technical or other inquiries. To bring about a swift return to normal life. Simultaneously to maintain normal services at an appropriate level.

4.7 - The Response to Disaster at a Single Site.

Within the UK, there is ample experience of disasters occurring within the bounds of relatively small areas. Many of the principles which emerge can also be applied to more widespread disasters. The scene immediately after disaster has struck is likely to be confused. To bring some order to this confusion, it is important that the emergency services establish control over the immediate area and co-ordinate the contributions to the response. Experience has shown that an effective response depends on good communications and mutual understanding. It is generally accepted that the first member of the emergency services to arrive on the scene should not immediately become involved with rescue, but should make a rapid assessment of the disaster SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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and report to that service's control. Such information as is immediately available should be provided about the nature of the disaster and its location; the number of dead, injured and uninjured; hazards actual and potential; access to the site and possible rendezvous points; and which emergency services are present or required.  Additionally, each of the emergency services has its own requirements. For example, in the case of the fire service, the number of appliances and personnel likely to be needed. The emergency services control centre which receives the initial message should immediately, and in accordance with established plans, alert the other emergency service control rooms, the local authorities and (where appropriate) the commercial, industrial or other organisation(s) involved.  At the scene, it is vital that the emergency services establish control and co-ordination arrange ments at the earliest stage. Each service needs to establish its own control arrangements, but continuing liaison between the various controls throughout the response is essential. The underlying principle is that the police assume the role of overall co-ordination, thus enabling the other services to concentrate on their specific tasks.  A pre-arranged, coordinated management scheme for ag encies involved in responding to a disaster will ensure that resources are used to best effect, and will avoid situations where, for example, resources may be called upon simultaneously by different agencies. This is particularly the case with incidents that occur near or across administrative boundaries. Arrangements which may have to be made at the scene of disasters include: 

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Setting up an inner cordon to secure the immediate scene and provide a measure of protection for personnel working within the area.  All those entering the inner cordon must report to the relevant Co ntrol Post. This ensures that they can be safely accounted for should there be any escalation of the incident and affords opportunity for briefing about other issues of which they need to be aware. Persons leaving the cordon must also register their departure.  Assigning the control of specific functions to one of the emerg ency services or other agencies, taking account of the circumstances of the disaster, the professional expertise of the emergency services and other agencies and any statutory obligations. The location of a rendezvous point or points for the emergency services, and non-emergency services personnel. The location of internal traffic routes for the emergency services and other vehicles (including a one-way system where appropriate) and the location of a marshalling area. The location of a collection point for survivors before they are taken to a survivor reception centre; The location of a casualty clearing station to which the injured can be taken; and an ambulance loading point for those who need to be taken to hospital. The location of a body holding area and temporary mortuary; and The location of a media liaison point.

4.7.1 - The Response to Disaster at a Single Site cont'd.

The Management of Health and Safety at Work Regulations 1999 also place further expectations upon employers with regards to the contact of external services in times of emergency: Regulation 9: Contacts with external sources:

Every employer shall ensure that any necessary contacts with external services are arranged, particularly as regards first aid, emergency medical care and rescue work.

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Notes:

Employers should establish procedures for any worker to follow if situations presenting serious and imminent danger were to arise, e.g. a fire, or for the police and emergency services an outbreak of public disorder. 

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Emergency procedures should normally be written down as required by regulation 5(2), clearly setting out the limits of actions to be taken by employees. Information on the procedures should be made available to all employees (under regulation 10), to any external health and safety personnel appointed under regulation 7(1), and where necessary to other workers and or their employers under regulation 12. Induction training, carried out under regulation 13, should cover emergency procedures and should familiarise employees with those procedures. Work should not be resumed after an emergency if a serious danger remains. If there are any doubts, expert assistance should be sought, e.g. from the emergency services and others. There may, for certain groups of workers, be exceptional circumstances when re-entry to areas of serious danger may be deemed necessary, e.g. police officers, fire fighters and other emergency service workers, where, for example, human life is at risk. When such exceptional circumstances can be anticipated, the procedures should set out the special protective measures to be taken (and the pre-training required) and the steps to be taken for authorisation of such actions. The procedure for any worker to follow in serious and imminent danger has to be clearly explained by the employer. Employees and others at work need to know when they should stop work, and how they should move to a place of safety. In some cases this will require full evacuation of the workplace; in others, it might mean some or the entire workforce moving to a safer part of the workplace. The risk assessment should identify the foreseeable events that need to be covered by these procedures. For some employers, fire (and possibly bomb) risks will be the only ones that need to be covered. For others, additional risks will be identified. Where different employers (or self-employed people) share a workplace, their separate emergency procedures will need to take account of everyone in the workplace, and as far as is appropriate the procedures should be coordinated.

Danger Areas: 

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 A danger area is a work environment which must be entered by an employee where the level of risk is unacceptable without taking special precautions. Such areas are not necessarily static in that minor alterations or an emergency may convert a normal working environment into a danger area. The hazard involved need not occupy the whole area, as in the case of a toxic gas, but can be localised, e.g. where there is a risk of an employee coming into contact with bare live electrical conductors. The area must be restricted to prevent inadvertent access. This regulation does not specify the precautions to take to ensure safe working in the danger area - this is covered by other legislation. However, once the employer has established suitable precautions, the relevant employees must receive adequate instruction and training in those precautions before entering any such danger area.

Contacts with external services:

The employer should ensure that appropriate external contacts are in place to make sure there are effective provisions for first aid, emergency medical care and rescue work, for incidents and accidents which may require urgent action, and/or medical attention beyond the capabilities of on-site personnel. This may only mean making sure that employees know the necessary telephone numbers and, where there is a significant, risk that they are able to contact any help they need. This requirement does not in any way reduce employers' duty to prevent accidents as the first priority. Where a number of employers share a workplace and their employees face the same risks, it would SHEilds Ltd www.sheilds.org  eLearning: www.sheilds-elearning.co.uk NEBOSH International Diploma v 1.3c (15/11/2013)

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be possible for one employer to arrange contacts on behalf of themselves and the other employers. In these circumstances, it would be for the other employers to ensure that the contacts had been made. In hazardous and complex workplaces, employers should designate appropriate staff to routinely contact the emergency services to give them sufficient knowledge of the risks. They need to take appropriate action in emergencies, including those likely to happen outside normal working hours. This will help these services in planning for providing first aid, emergency medical care and rescue work, and to take account of risks to everyone involved, including rescuers. Contacts and arrangements with external services should be recorded, and should be reviewed and revised as necessary, in the light of changes to staff, processes and plant, and revisions to health and safety procedures.

4.8 - Why plan for emergencies? Major :

Major accident scenarios can and do happen, and there are a number of examples from which to choose, such as Piper Alpha or, more recently, the Buncefield Oil Depot. The control of such major accidents is regulated by the Control of Major Accident Hazards Regulations 1999, or COMAH for short. The following text is derived from a Health and Safety Executive leaflet outlining the requirements of the regulations and the need for, and importance of, a Major Accident Prevention Policy: The Control of Major Accident Hazards Regulations 1999 (COMAH) Introduction: 

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The Control of Major Accident Hazards Regulations 1999 (COMAH) are the most far-reaching set of regulations to apply to 'major hazard' premises for many years. This sheet provides information to those who control the operation of establishments where COMAH applies - referred to as operators in the regulations. It explains the requirement for 'lower-tier' establishments to prepare and keep a Major Accident Prevention Policy document, or MAPP document for short. Such a document sets out your policy with respect to the prevention of major accidents. COMAH applies to establishments where specified quantities of dangerous substances are present, or likely to be present. This includes sites where dangerous substances might be generated due to the loss of control of an industrial chemical process. The COMAH Regulations include lists of specified quantities of dangerous substances that are used to determine whether an establishment is top or lower-tier. Some of the duties imposed by COMAH do not apply to lower-tier establishments. The HSE publication L111 A guide to the Control of Major Accident Hazards Regulations 1999 will help you decide if the Regulations apply, and whether your establishment is top-tier or lower-tier. The reference list at the end of the information sheet includes full details of this guide, together with other publications on COMAH. The COMAH Regulations are enforced by a Competent Authority made up of the Health and Safety Executive (HSE) acting jointly with either the Environment Agency (EA) or the Scottish Environment Protection Agency (SEPA).

What's new?

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COMAH introduced several new duties on operators of lower-tier sites, the main ones being a notification requirement and a duty to prepare a MAPP. Every operator of an establishment to which COMAH applies must have a MAPP document, regardless of whether the establishment is lower-tier or top-tier. However, for top-tier establishments, the MAPP may be included in the safety report, and in this case a separate document is not required. Lower-tier establishments do not have to produce a safety report and therefore need to prepare a separate MAPP document.

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The requirement for a MAPP document builds on the duties under existing legislation, but focuses on major accident hazards, and the document should show that you have a safety management system in place for implementing the MAPP. Existing legislation will continue in force, such as the Health and Safety at Work Act 1974 and associated legislation, including the Management of Health and Safety at Work Regulations 1999, together with current environmental legislation. Much of this legislation is concerned with the provision of integrated management systems for controlling the risks to health, safety and the environment.  Advice on management systems is available from a variety of sources. You may have seen the HSE publication HSG65 Successful health and safety management which provides a guide on how to manage health and safety in organisations. Many companies now use environmental management systems such as ISO 14001 as part of their business. The Environment Agency's IPC Guidance to the chemical industry contains an overview of the aspects to be considered from an environmental management viewpoint. Although these approaches are the ones referred to by HSE and the Agencies, you may, if you choose, use another management approach, as long you achieve compliance with your legal duties and a good standard of control. Further relevant guidance is produced by the Environment Agencies in the Pollution prevention series.

What is a MAPP? 

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Your MAPP document should set out your policy on the prevention of major accidents: in other words, a statement of general intent which includes the aims and the principles you plan to adopt. The MAPP document doesn't need to contain a detailed description of your safety management system (the organisation and arrangements for implementing the policy to ensure the control of major accident risks). However, it should give sufficient detail to show you have systems in place to cover all the aspects listed later in the section 'What should go in your MAPP document?'. Your MAPP document must address the management of the major accident hazards at a particular establishment, and should be specific to that establishment.

A MAPP document is similar in approach to a health and safety policy document, but with two important additions:   

It must deal specifically with major accident hazards. It must include measures to protect the environment. You can adapt your existing health, safety and environmental policy statement to include the MAPP information, or you may prefer to produce a separate document. A senior person in your organisation should sign your MAPP document.

When does your MAPP document have to be ready?

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The requirement for MAPPs was introduced when COMAH came into force. If your establishment was operating before this date, and is now a lower-tier site, you need to prepare your MAPP document as quickly as possible, and you should discuss the timescale with the Competent Authority. If your establishment did not exist before COMAH was introduced, you need to produce your MAPP document by the time the Regulations apply to your establishment.

Who will need to see your MAPP document? 

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Inspectors from HSE or the Agencies will probably ask to see a copy of your MAPP document, and you need to provide them with a copy if they ask for it.  As your MAPP document supplements your health, safety and environmental policies, you should make it available to those who need to see these policies, including employees, employee representatives and contractors. There is no specific duty under COMAH for you to consult your employees on what is in your MAPP document, as this duty is imposed by other legislation (The Health and Safety (Consultation with Employees) Regulations 1996). These Regulations require employers to enable employees to take part fully in consultation and to understand what the likely risks and hazards arising from their work are, and how these are eliminated or controlled. Similarly, much environmental legislation contains the requirement for employees to be given an understanding of the environmental risks of their workplace, and how these are avoided or controlled.

What should go in your MAPP document? 

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Your MAPP document should contain at least the information listed in the following sections. The amount of detail should be proportionate to the level of the hazards present - the greater the hazards, the more detail you will have to provide. For most establishments, the MAPP document will be relatively short and simple. You probably already have much of the information such as training records, your own internal site inspection records, audit reports, operating procedures, risk assessments, etc. and can simply refer to it in your MAPP document. Regulation 5 and Schedule 2 to COMAH specify the information that should go into the MAPP document.

The information is in two parts: 

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Your policy, or statement of intent, setting out your aims and principles of action with respect to the prevention of major accidents; and  A description of your safety management system for achieving the stated aims. The most important aspects of a safety management system for controlling major accident hazards are described in Schedule 2 of COMAH, and summarised in the following sections.  Accident scenarios can and do happen, and there are a number of examples from which to choose, such as Piper Alpha or, more recently, the Buncefield Oil Depot. The control of such major accidents is regulated by the Control of Major Accident Hazards Regulations 1999, or COMAH for short.

4.9 - Roles and Responsibilities of Persons at all levels.

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aspects to be covered. Organising. 

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You probably already have this information in your safety policy, but you need to ensure it refers specifically to the key roles for the management of major hazards. These roles are listed in the following paragraphs, from both a safety and an environmental point of view. Training: Arrangements for selecting personnel and providing training to ensure they are competent to work with a major hazard.

Arrangements for the involvement of employees. Organising: 

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Your MAPP document only needs to discuss those aspects that are relevant to a major hazard. It should outline your system for addressing these issues. This includes how you identify training needs, and the follow-up you carry out, i.e. your training policy and your system for ensuring effective communication with, and involvement of, employees, and where necessary subcontractors. The MAPP document does not need to include detailed records, but should refer to them. Hazard identification and risk assessment. (Planning and implementing). Your MAPP document should describe your overall aims, approach and policy for hazard identification and risk assessment. You need to describe how the results are used, e.g. your policy on eliminating hazards. You should not include detailed reports or results in the MAPP. Guidance on environmental assessment can be found in the EA/SEPA publication Guidance on environmental risk aspects of COMAH safety reports. Further help on major accidents to the environment is given in the publication from the Department of the Environment, Transport and the Regions (DETR) Interpretation of major accidents to the environment.

Procedures and instructions for safe operation. Organising, Planning and implementing: 

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Your MAPP document should record how you ensure you have adequate management arrangements, workplace precautions and control measures in place for safe operation. It should outline your system for developing, reviewing and revising procedures, and describe how you make sure the procedures are properly communicated. You do not need to include details of the procedures, although you may wish to mention where the details are located. For example, your MAPP document could say that you use a permit-to-work system for certain tasks, or an inspection and maintenance system for ensuring the integrity of safety and environmental critical control systems, but it does not need to include details of how these systems work.

Design and modifications of installations. Planning and implementing, Measuring and Review: 

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Your MAPP document needs to state how you modify procedures (including management arrangements) and plant. It also has to show how you ensure that any new plant on site is designed, constructed,

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installed and maintained to relevant standards. It is important that your MAPP document shows you have a workable system for identifying, assessing, and authorising modifications.

Identification of foreseeable emergencies and the preparation, test and review of emergency procedures. Planning and implementing: 

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This section overlaps with your policy for hazard identification and risk assessment described previously. Your MAPP document needs to detail your policy on identifying possible major accidents, and to show that you have plans in place to respond. It should indicate the types of major accidents you have identified and considered. You may find it useful to refer to the definition of a major accident in COMAH regulation 2. Unlike top-tier sites, lower-tier sites do not have to prepare full on- and off-site emergency plans. However, because lower-tier sites could cause a major accident, it is important that you identify how such accidents could occur and establish adequate emergency arrangements for dealing with them. Some documentation of these arrangements is normally required. You need to consider the possible involvement of people in neighbouring premises (both residential and commercial) and the emergency services. Your MAPP document should include your policy on reviewing and testing the emergency procedures. However, the COMAH regulations do not state how often the reviewing and testing should take place. The HSE publication HSG191 Emergency planning for major accidents is useful, but was written primarily for top-tier sites.

Measuring compliance. Measuring: 

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You need to have a system for assessing whether your site continues to meet the objectives in your MAPP document, and whether the standards you set are being maintained. Your MAPP document should describe how this assessment takes place, and how you would correct any deficiencies. This part of the document also needs to include your system for reporting and investigating accidents and near misses, and to explain how you make sure that the lessons learned are implemented.

Review and audit.

You need to have a system for making sure your management systems and procedures continue to be correct, and that they are being followed. Your MAPP document needs to describe how you use audit and review to maintain the validity of both the MAPP document and your safety management system. When should I update it?

In addition to the requirement on you to review your MAPP and safety management system after audit, you also need to review them if you make any modifications that could have significant repercussions in respect of the prevention of major accidents, including changes to:  

Your establishment. The type or amount of dangerous substances used.

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How you process and/or store them. It is good practice to review your MAPP, and the safety management system for implementing it, after any accidents or near-misses, as well as on a regular basis, although this is not specifically required by the Regulations. Regular reviews and updates will make sure your MAPP remains correct and relevant. What do I need to do next? Once you have prepared your MAPP, the next step is to implement it. Inspectors from the Competent Authority will want to verify not only that you have a MAPP and a suitable safety management system, but also that you have implemented them.

4.10 - Video - Disasters and Emergency Management.

Video Missing.

Question 1.

Which phase change is endothermic? Multiple Choice (HP)

 Answer 1: gas --> solid Response 1: Sorry that is Incorrect, Please Try Again! Jump 1: This page  Answer 2: gas --> liquid Response 2: Incorrect, Please Try Again! Jump 2: This page  Answer 3: liquid --> solid Response 3: Incorrect, Please Try Again! Jump 3: This page  Answer 4: liquid --> gas Response 4: That is the Correct, Well Done! Jump 4: Next page

Question 2.

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 A place in which an explosive atmosphere is not likely to occur in normal operation, but if it does occur, will persist for a short period only, is an example of a zone Multiple Choice (HP)

 Answer 1: 0 Response 1: Jump 1: This page  Answer 2: 1 Response 2: Jump 2: This page  Answer 3: 2 Response 3: Jump 3: Next page  Answer 4: 3 Response 4: Jump 4: This page  Answer 5: 4 Response 5: Incorrect, Please Try Again! Jump 5: This page

Question 3.

Please Choose the Correct Answer from the List. Examples of endothermic processes include: Multiple Choice (HP)

 Answer 1: All of these Response 1: Jump 1: Next page

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 Answer 2: Melting ice cubes Response 2: Jump 2: This page  Answer 3: Melting solid salts Response 3: Jump 3: This page  Answer 4: Evaporating liquid water Response 4: Jump 4: This page  Answer 5: Making an anhydrous salt from a hydrate Response 5: Jump 5: This page  Answer 6: Forming a cation from an atom in the gas phase Response 6: Jump 6: This page

Question 4.

The basis of emergency planning and response is now known as Integrated Emergency Management. True/False (HP)

 Answer 1: True Response 1: Jump 1: Next page  Answer 2: False Response 2: Jump 2: This page

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