20158i Fire Protection

PETRONAS TECHNICAL STANDARDS DESIGN AND ENGINEERING PRACTICE

MANUAL

INSTALLATIONS AND DEPOTS PART 9 - FIRE PROTECTION

PTS 20.158I JUNE 1993

PREFACE

PETRONAS Technical Standards (PTS) publications reflect the views, at the time of publication, of PETRONAS OPUs/Divisions. They are based on the experience acquired during the involvement with the design, construction, operation and maintenance of processing units and facilities. Where appropriate they are based on, or reference is made to, national and international standards and codes of practice. The objective is to set the recommended standard for good technical practice to be applied by PETRONAS' OPUs in oil and gas production facilities, refineries, gas processing plants, chemical plants, marketing facilities or any other such facility, and thereby to achieve maximum technical and economic benefit from standardisation. The information set forth in these publications is provided to users for their consideration and decision to implement. This is of particular importance where PTS may not cover every requirement or diversity of condition at each locality. The system of PTS is expected to be sufficiently flexible to allow individual operating units to adapt the information set forth in PTS to their own environment and requirements. When Contractors or Manufacturers/Suppliers use PTS they shall be solely responsible for the quality of work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, the Principal will expect them to follow those design and engineering practices which will achieve the same level of integrity as reflected in the PTS. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the Principal or its technical advisor. The right to use PTS rests with three categories of users : 1) 2) 3)

PETRONAS and its affiliates. Other parties who are authorised to use PTS subject to appropriate contractual arrangements. Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) and 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards.

Subject to any particular terms and conditions as may be set forth in specific agreements with users, PETRONAS disclaims any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person whomsoever as a result of or in connection with the use, application or implementation of any PTS, combination of PTS or any part thereof. The benefit of this disclaimer shall inure in all respects to PETRONAS and/or any company affiliated to PETRONAS that may issue PTS or require the use of PTS. Without prejudice to any specific terms in respect of confidentiality under relevant contractual arrangements, PTS shall not, without the prior written consent of PETRONAS, be disclosed by users to any company or person whomsoever and the PTS shall be used exclusively for the purpose they have been provided to the user. They shall be returned after use, including any copies which shall only be made by users with the express prior written consent of PETRONAS. The copyright of PTS vests in PETRONAS. Users shall arrange for PTS to be held in safe custody and PETRONAS may at any time require information satisfactory to PETRONAS in order to ascertain how users implement this requirement.

Part 9 SECTION 15.00.00 - FIRE PROTECTION

INSTALLATIONS AND DEPOTS MANUAL Section List Part 1

Section 00.00.00 Section 01.00.00 Section 02.00.00

Introduction Master Development Planning Construction Projects

Part 2

Section 03.00.00

Sites and Layouts

Part 3

Section 04.00.00 Section 05.00.00

Building and Civil Engineering Tanks and Pressure Vessels

Part 4

Section 06.00.00

Pipelines

Part 5

Section 07.00.00 Section 08.00.00

The Design of Berthing Facilities for Tankers and Small Craft Heating and Insulation

Part 6

Section 09.00.00

Plant and Equipment

Part 7

Section 10.00.00 Section 11.00.00

Utilities Mechanical Handling

Part 8

Part 9

Section 12.00.00 Section 13.00.00 Section 14.00.00 Section 15.00.00

Maintenance and Workshops General Services Chemicals Handling Fire Protection

Part 10

Section 16.00.00

Electrical and Static Electricity Hazards

Section 17.00.00

Bibliography

15.00.00.

FIRE PROTECTION

15.00.01

Installations and Depots

15.00.02

Retail Outlets

15.00.03

Customer Sites

15.00.04

Public Fire Services

15.01.00.

FIRE PROTECTION SYSTEMS AND EQUIPMENT

15.01.01

Summary

15.01.02

Hand and Mobile Extinguishers

15.01.03

Water Supply, Fire Mains and Foam Systems

15.01.04

Fire Pumps

15.01.05

Fire Hoses and Accessories

15.01.06

Foam and Water Monitors

15.01.07

Sub-surface (Base Injection ) and Semi-subsurface foam For Storage Tanks

15.01.08

Foam Pourers For Floating Roof Tanks

15.01.09

Distinctive Colouring

15.01.10

Fire Alarms And Emergency Calls

15.02.00

LEVELS AND TYPE OF PROTECTION

15.02.01

Tank Farms

15.02.02

Bulk Vehicle Loading Gantries

15.02.03

Rail Tank Waggon Filling or Discharge Facilities

15.02.04

Berths And Jetties

15.02.05

Fires Involving Electrical Equipment

15.02.06

Protection Of Computer Facilities

15.02.07

Fires Involving Chemical Products

15.03.00

FIRE FIGHTING AGENTS

15.03.01

Types of Fire

15.03.02

Water

15.03.03

Foams

15.03.04

Carbon Dioxide

15.03.05

Dry Chemical Powders Appendix 15.0 1.01 Appendix 15.01.02 Appendix 15.01.03 Appendix 15.01.04 Appendix 15.01.05 Figure 15.01.06 Figure 15.01.07 Figure 15.01.08 Figure 15.01.09 Figure 15.01.10 Figure 15.01.11 Figure 15.01.12 Figure 15.01.13 Figure 15.01.14 Figure 15.01.15 Figure 15.01.16 Figure 15.01.17

Recommended 'First Aid' Fire Extinguishers Recommended Scale of Fire Equipment Planning and Provision of Extinguishers Limiting of Halon Emissions Fixed Cooling for Vertical Tanks Chubb Mobile CPC Dry Chemical Powder Extinguisher Chubb FL22 Mobile Foam Liquid Proportioner Unit Chubb Mobile Foam Units Flow Rates from Fire Hose Nozzles Pressure Loss in Fire Hoses Hydrant-fed Fire-fighting Equipment Typical Foam-Generating Fire-Fighting Equipment Typical Foam Concentrate Induction Instantaneous Hose Couplings and Accessories Typical Mechanical Foam Generators Chubb 'Jet-Master' Portable Mechanical Foam/Water Monitor Chubb Model 10A-30A High Back Pressure Foam Makers Chubb 'Jet-Master' Mechanical Foam Monitor with Adaptor for Base Injection

Figure 15.01.18 Figure 15.01.19 Figure 15.01.20 Figure 15.01.21 Figure 15.01.22 Figure 15.01.23 Figure 15.01.24 Figure 15.01.25 Figure 15.01.26 Figure 15.01.27 Figure 15.01.28 Figure 15.01.29 Figure 15.01.30 Figure 15.01.31 Appendix 15.02.01

Angus Variable Foam Inductor Distribution of Foam and Circulation of Tank Contents in Foam Base Injection Systems Semi Sub-surface Injection of Foam Semi-fixed base injection system Fixed base injection system Fixed base injection system Fixed base injection system Angus Fire Armour High-Back- Pressure Foam Generators (Series 2) Tank Inlet for Base Injection of Foam Single Foam Pourer for Floating Roof Foam Pourers for Floating Roof Tanks Foam Pourer Cover N2 Unit Alarm for 'Poly-flo' Line Detection Typical Dry Riser showing Connections Sub-Surface Foam Injection Design and Equipment - Protection

15.00.00.

FIRE PROTECTION

15.00.01

Installations and Depots At installations and most depots the fire protection systems would normally be based on a water main and hydrant system routed and equipped so as to be able to apply foam and/or water to all main fire targets such as storage tanks, loading gantries, pumphouses, warehouses, process/filling plants, jetties and buildings. Water supply should preferably be from a harbour, river, or other unlimited source or from municipal water mains supply. If such are not available, a water tank or reservoir will need to be provided. Where salt or brackish water is used it is recommended that the system be flushed with fresh water after use. Pumping capacity should be installed unless the local fire brigade or other outside resources are always readily available, and their participation in the site fire plan is organised and regularly rehearsed. The incorporation of sub-surface foam (base-injection) for tank Protection should be decided upon depending on considerations given in 15.01.07 to 15.02.01 below. The provision of more sophisticated fire protection equipment such as self-propelled fire trucks, continuously pressurised water mains either primed by jockey pump or static head, automatic or remote pump starting and control, automatic foam generating or deluge systems, though not always appropriate for other than the largest installations, should nevertheless be considered in the light of the size, complexity, manning level and accessibility of effective outside help. In view of the reduced availability of human intervention during these operations e.g. at unmanned terminals automatic fire detection coupled with an automatic fixed foam spray system is recommended for the bulk vehicle loading gantry. Dry fire mains are unsafe and if a slug of air is entrapped it can be a serious hazard to the fire fighter handling hoses, and therefore are not recommended. Also they are subject to internal corrosion. First-aid fire protection based on mobile and hand extinguishers may be appropriate for certain non-critical locations, though advantage should generally be taken of any nearby municipal or natural water source, since a water supply, however small, is always an asset. Finally, it is generally sound practice to liaise with neighbouring installations, depots, refineries etc. both in the provision of fire fighting equipment so as to share the cost, and in the development of emergency plans so as to increase the resources available. Naturally, joint fire emergency practices are crucial to the success of such arrangements.

15.00.02.

Retail Outlets Fire risks at retail outlets are regarded as comparatively minor since bulk flammable products are stored below ground, leaving a potential for small fires only. Protection against these is provided by a supply of hand extinguishers plus water which is usually available at retail sites. For details reference should be made to the Retail Image booklet, Part 2. The one exception to this is automotive LPG whose tanks may be installed above ground. Reference should be made to the LPG Manual, Part 6, Section 8, Fire Fighting and Safety. The most hazardous situation occurs during product delivery by bulk vehicles. Fire protection is provided by hand extinguishers deployed during discharge and the constant presence of a professional bulk vehicle driver trained in safe operational (and emergency) procedures including fire fighting.

15.00.03.

Customer Sites Provision of fire protection is usually in the hands of the customer though advice from PETRONAS is often sought, and should be offered. Hand extinguishers are normally adequate to be used to extinguish any small fires that may threaten customers' product storage tanks. Where larger bulk storage exists, for example at power stations, large factories etc., the provision of mobile extinguishers or even bulk water plus foam making equipment may be appropriate. As for retail, the presence of a trained driver provides the most effective protection during product deliveries.

15.00.04.

Public Fire Services Liaison with and participation by local public fire services must always be considered, though the value of such outside help may vary. Nevertheless fire protection planning must take into account the part to be played by any local fire services. It is worth remembering that what they may lack in experience of petroleum fires can be helped by training with PETRONAS employees, and is often supplemented by their greater experience in the art and skills of general fire fighting and containment.

15.01.00

FIRE PROTECTION SYSTEMS AND EQUIPMENT

15.01.01.

Summary The aim of any fire protection system is to provide two stages of fire fighting capability. Firstly, there must be an immediate action response based on own resources, using hand or mobile extinguishers by the people working at or those first to arrive at the scene of the fire. Secondly, there must be a back-up either from one's own resources or by in conjunction with outside assistance to undertake the larger scale and more prolonged fire fighting effort to contain the fire or extinguish, in the event that the immediate action is unsuccessful The scale and type of protection service provided depends not simply on whether the facility is an installation, depot, retail outlet, or other, but rather on the number, scale and type of the various activities that comprise the total operation, any of which may present unique problems, and all of which must be appropriately protected. By virtue of its size and importance in the distribution network, an installation would normally be expected either to have its own fixed facilities comprising water supply, pumping capacity, and fire main and hydrants system, or to have sufficient facilities (e.g. a pressurised main and hydrants system with access to water) for a nearby local fire service to use with its own manpower and equipment. By definition, depots (distribution and minor airfields) are vulnerable and therefore a reduced scale of fire protection may be acceptable. On the other hand, depots are often located in remote areas where outside help may be non-existent or of unreliable quality. If such a depot cannot be by-passed or take hospitality from a nearby competitor's depot, for instance and if it occupies an indispensable position in its area, then the results of a loss or lengthy period out of service have to be judged against both commercial and loss or lengthy period out of service have to be judged against both commercial and political repercussions. An additional factor to be taken into consideration is whether a fire (for example a tank fire) could pose a serious threat to adjacent property, particularly domestic. If such special factors indicate that a particular risk exists or in order to comply with local requirements, depots may in certain instances have to be treated as small installations, and their fire protection system must be designed and built accordingly.

15.01.02.

Hand and Mobile Extinguishers At every work place where a fire could possibly start, a supply of portable and/or mobile extinguishers should be readily accessible to enable the nearest person to mount an immediate first attack on the incipient fire. The value of being able to put out a fire in its early stages should not be underestimated. Efforts to ensure such units are plentiful, easily seen, kept in good condition, appropriate for the type of fire that might occur, and that people working in that vicinity are properly trained in their use, will be repaid many times over if just one fire is caught before serious injury or damage can occur. A scale of one 90/150-litre foam trolley or one 70 kg powder extinguisher unit at each main potential hazard such as pump manifold, double bay vehicle loading gantry, drum filling shed, etc., would normally be sufficient. Where a unit with rather longer fire fighting capability is thought necessary, a trolley unit carrying concentrated foam compound to which water is supplied by hose may be appropriate as these given up to 15 minutes foam application. For special hazards such as at vehicle loading bays, a 90-litre aqueous-film-forming foam (AFFF) mobile unit is an effective means of covering and sealing a spill caused by overfilling, or rapidly extinguishing any fire that may result. A supply of smaller hand extinguishers should be provided as supplementary to the larger units as well as for all other locations where minor fires can be expected. The distribution and location of these units should be such that every potential fire target has not less than two units readily accessible. This is particularly important where little or no back-up fire fighting support is available. See Figures 15.01.06 and 15.01.07 for examples of the many typical mobile units available.

Extinguishers should be positioned in the most conspicuous and accessible position (e.g. near entrances and exits, on staircase landings, etc.), with painted background if necessary to attract attention. They should be mounted on brackets at convenient height and not be left standing on the ground where they are subject to damage, splashing or rain and dirt, and are less obvious. An empty bracket is a convenient signal that a unit is missing. When mounted outside, extinguishers should be kept in or under weather protection in order to reduce deterioration. Where members of the public are involved, for instance at retail outlets thought must be given to ease of carrying and operating extinguishers; large, heavy units would be too difficult for many people to handle. Two important factors influencing the distribution of extinguishers are: (i)

The type and size of fire for which they are likely to be used. There are hand or mobile extinguishers which contain all of the common fire fighting agents. Section 15.03.00 gives information on the characteristics of different fire fighting agents to assist in selection of the best choice of extinguisher. Appendices 15.01.01 and 15.01.02 give data on different types of extinguishers and on the recommended scale to be held at different locations. Appendix 15.01.03 gives an extract from BS 5306 Part 3 on the new scheme for the planning and provision of extinguishers. This scheme makes it possible to specify the distribution of extinguishers in building, plants etc., according to extinguishing capability rather than by type and size or content. Extinguishers are marked with numbers and letters indicating the maximum size and type of fire they are capable of extinguishing (under tests set out in BS 5423). For example an extinguisher marked '13A' is capable of extinguishing a class A test fire (solid materials e.g. wood, paper, textiles) of size 13A; similarly an extinguisher marked '55B' is capable of extinguishing a class B test fire liquids or liquefiable solids) of size 55B. Extinguishers with both class A and class B capability are marked accordingly, e.g. 13A/55B. For more detailed explanation refer to BS 5306, of which extracts are given in Appendix 15.01.03.

(ii)

Requirements and availability of service and repair facilities. All extinguishers deteriorate with time and under the influence of atmospheric conditions. It is essential that they be at least visually inspected every six months and refilled every 12 months. This can either be done by PETRONAS staff properly trained or else contracted out to local agents or suppliers, provided they are competent, hold a good stock of spare parts and refills, and that their work is spot checked by company staff on a random basis so as to keep them up to standard. Makes of extinguisher with poor back-up supply of spares and refills should not be used and should be replaced by better serviced makes. In addition to the programme of formal inspections it should be part of the regular duty of supervisors and/or operators visually to check extinguishers at least monthly to make sure they are in their proper position, have not been discharged or lost pressure, suffered visible damage or deterioration, and are being regularly inspected. For this purpose the dates of inspection and refilling should be indelibly recorded on the extinguisher or on a firmly attached label. For details of inspection and testing of extinguishers see Plant Operating Manual Volume 1 Appendix 07.02.03.

15.01.03.

Water Supply, Fire Mains and Foam Systems The backbone of most fire protection systems is a properly designed water main, hydrant and pumping system. The recommended level of fire fighting equipment is based on the assumption that only one major fire will have to be fought at a time. The first step therefore must be to assess what might be the worst credible incident. Normally this has been regarded as the largest diameter tank containing Class I or II products in an installation or depot, but this decision should be taken only after assessing all other major fire possibilities, such as tank bunds, vehicle or rail loading gantries, jetties, warehouses etc, as well as the likely simultaneous cooling requirements. It should be realised that the biggest tank fire might not be related to the highest cooling demand for surrounding tanks. Depending on tank farm layout, a somewhat smaller tank fire might be in a situation requiring the highest flow of cooling water for surrounding tanks, such that the combination of the cooling, water required plus the water required for bottom injection, results in the total water requirement and therefore the one to be used for the overall design basis. Based on the worst case fire that might occur, the overall fire protection required should be made up of three elements: (i)

Water cooling of adjacent tanks or other facilities exposed to heat radiation from the major fire. (ii) Foam application to extinguish the major fire (storage tank or other). (iii) Supplementary foam (or water) to tackle any minor fire that may occur in the vicinity or to provide additional cooling. Supplementary protection by hose and monitor is vital particularly in locations where totally fixed foam and cooling systems are installed. The overall fire protection system must be designed to be adequate in three related aspects if it is to be effective: (i) Adequate water supply in the right places to provide cooling capacity and/or foam making for the necessary periods of time. (ii) Sufficient water flow rate to provide adequate cooling of exposed facilities to overcome the effect of heat from an adjacent fire and/or overcome the burning of a fire by a foam application. (iii) Sufficient water pressure at all hydrant outlets to operate foam making equipment and to reach high or distance fire targets. Deficiency in any one of the above may well result in failure to extinguish or contain a fire. The highest combination of foam making and cooling water must be used for the design basis. (a)

Water Supply A supply of either fresh or salt water is required at a minimum main pressure at distant hydrants of 7-10 bar gauge under full flow. Though higher pressures may be needed for sub-surface injection (refer 15.01.07) hose pressures should be restricted to a maximum of 12 bar, due to the difficulty and possible hazard of controlling hoses under high pressures. For this reason it is recommended that hand held hoses should be limited to 1½ inch diameter but fitted with 2½ inch couplings. Except where water supply is unlimited, e.g. from sea, harbour, rivers or other open sources, provision of a reservoir, tank or other water storage must be considered. This will necessitate carefully estimating what water stocks are necessary and practicable to hold. Methods for estimating the quantity of water needed for foam making are given under (c) below. For cooling purposes it is suggested a supply to permit at least 2 hours cooling be held, but every practicable means of supplementing this should be sought. Too much water application could be a problem during a real fire if the drainage system cannot cope. A flooded area might be a fire risk, due to product (fire) floating on excess water. Note: During water tank maintenance a back-up water supply must be arranged. The water volume depends upon the scope of the facilities to be protected and must be adequate for the highest combination of both the foam making requirements and the cooling of adjacent tanks or other structures. Water is also used for fires not involving petroleum products (i.e. offices, dry vegetation, etc.), however, quantities provided for fighting oil fires will normally be more than adequate for these other purposes. Provision for future expansion should be made where applicable.

The routing and extent of the fire main system plus the number and location of hydrants must be carefully chosen so as to provide water for foam making and cooling of adjacent tanks or facilities at all significant potential fire targets. Flushing connections to clear sediment should be provided at intervals not exceeding 75 m and should allow for a flushing velocity of 2.5 m/sec minimum. Water hydrants, each with two outlets, should be sited strategically throughout the installation, at distances of between 30 and 50 m from the items to be protected - allowing for the possibility that access to any fire may be restricted by prevailing winds and/or the fire situation itself being limited to only one avenue of attack. The aim should be to restrict hose strings to two or three standard (25 m) lengths in order to minimise pressure losses and the time taken to connect hoses. Selection of hydrant valves with low pressure drop will help conserve main water pressures. In tank farms hydrant off-take points should be positioned so as to be accessible in the event of all fire incidents, including bund fires. Water lines for tank cooling should be above ground inside the bund for ease of inspection and maintenance, also to prevent any damage from tank settlement. Previous editions of this manual advocate they should be buried, this is no longer the case. Block valves should be incorporated in the ring main where it may be considered useful to be able to isolate sections of the main, should it become damaged. (b)

Water Flow Rate - Cooling (Appendix 15.01.05) Fixed cooling is required for fixed roof tanks holding Class I, II (2) or III (2) products and, in addition, for tanks holding Class II (1) and III (1) products where these might become endangered by adjacent fires. Class I, II (2) and III (2) tanks should be fitted with water spray or deluge systems to provide immediate all-over cooling, whereas Class II (1) and III (1) tanks can be cooled using water hoses or monitors from the ground on the exposed sides only provided the reach of the equipment can cover the tanks, failing this a spray ring should be fitted to the tank shell. The term sprinkler system is normally applied to indoor systems in offices or buildings to combat Class 'A' fires and the water droplets are larger than a tank roof/Shell spray system. The design of a tank farm cooling system requires careful considerations of the several variables such as different combinations of tanks to be cooled, variation in size and type of fire, products involved, wind conditions, presence of possible fire in the bund, and changes that take place during a fire. No single water application rate will cater exactly for all fires but careful design and operation can approach the ideal. A critical point is that the total water supply has to be shared simultaneously with the demands of the foam making system used for fire fighting and for cooling where applicable. A manually activated (e.g. new project) fixed cooling water system with a minimum application rate of 1.7 litres/min/m² of exposed surface is recommended for tanks spaced in accordance with safety distances given in 03.05.06. This will give a heat barrier and cooling effect that can normally be turned on promptly thus leaving personnel free to carry out other fire fighting duties. (For LPG requirements see the LPG Manual). Depending on the development of a fire it may become a tactical requirement to supplement this basic level for a particularly exposed surface by reducing application to a less exposed surface during an actual fire. Such application would not necessarily require the total design cooling water rate to exceed 1.7 litres/min/m². It would be applied by utilising hoses and/or monitors wherever the amount of fixed spray water is inadequate, for example, on any part of a tank shell 'This would be evident if all cooling water on exposed shell or roof turns into steam, some parts of the shell are not receiving water, the shell metal is discolouring from the effect of heat, vapour and/or flames are seen issuing from roof pressure/vacuum valves, or total water flow and pressure are judged to be inadequate.

It takes careful design and operation to produce a tank farm spray system that gives close to 1.7 litres/min/m² on all possible combinations of tanks. One solution for setting and controlling spray flow rates is to fit pressure gauges downstream of each spray line control valve. The pressure gauge dial can be marked with the pressure reading known by previous trials to give the desired water flow rate to that particular tank. As flow and pressure conditions vary during a fire, the sprinkler spray control valves can be adjusted so as to maintain as closely as possible the various design flow rates. Such valves should of course be located behind a fire barrier/screen outside bunds in positions least likely to be engulfed by fire. For improved cooling compared with the goose-neck deluge design, the use of spray nozzles is recommended to be located on one or more tank top headers and round the top course of the tank shell. The minimum recommended spray orifice size is 6 mm (to avoid blockage) which will achieve the application rate of 1.7 litres/min/m² or more for tank roof and 17 litres/min/m of circumference of shell for tank walls. For design details reference should be made to Appendix 15.01.05. A cooling water system designed for storage tank protection will normally have more than sufficient capacity for handling cooling requirements for other installations or depot facilities, for which hoses, nozzles and monitors would be used. LPG facilities are likely exceptions to this refer LPG Manual. (c)

Water Flow Rate - Foam Making For foam making, the rate of application is related to the time taken to cover the entire burning surface with a blanket of foam. Because a proportion of the foam may be blown away by wind or heat updraft or deflected by obstructions and a further proportion of the foam that reaches the burning surface is continually being destroyed or consumed by the fire, there is a minimum or threshold application rate on the actual target which must be achieved to extinguish the fire at all. The application rate at the target depends on the distance of the equipment to the target i,e, the generation rate x efficiency. In the following guide-lines which are based on British Standard BS 5306 Section 6.1: •

Foam solution application rates (1/min/m²) are the minimum flow rates (in litres per minute per square metre of fire area) of foam solution on the fire (water plus concentrate but not yet aspirated) required to achieve extinction.

•

Efficiency to obtain from the equipment the application rate at target.

•

Minimum discharge times are the lengths of time foam must be applied at the minimum flow rates to achieve extinction. 3

Thus these three parameters dictate the supplies (in litres or m ) of water and foam concentrate that must be held in readiness in order to fight the different types of fire. Such systems are used to provide protection against: •

Small local fires in bunds.

•

Spill fires (see also (v) Foam spray systems).

•

Small storage tanks (not greater than 6 metres high or 9 metres diameter).

•

Supplementary protection for large tanks equipped with sub-surface foam (base injection) systems.

Minimum foam solution application rates: •

Small tank fires: 6.5 litres/min/m²

•

Other fires: 6.5 litres/min/m²

The above figures refer to quantities at the apparatus, it follows that a lesser amount will reach the target. Minimum application times: •

Tanks - Class I and II products: 60 minutes Class III products: 45 minutes

•

Bunds, all products: 60 minutes

•

Spills, all products: 15 minutes

Minimum number of supplementary branch pipes and discharge times:

Tank

No

Discharge

branch pipes (400 1/m)

times (mins)

Less than 10

1

10

10 to 20

1

20

20 to 30

2

20

30 to 40

2

30

Over 40

3

30

dia (m)

(ii)

Foam pourer systems Such systems are used for the protection of fixed and floating roof tanks by applying foam gently onto the liquid surface in the following ways: •

Against the internal shell of a fixed roof storage tank.

•

Into the seal area of a floating roof tank.

Minimum foam solution application rates: •

Fixed roof tanks or bunds 4.0 litres/min/m².

•

Into the seal area of a floating roof tank.

Minimum foam solution application rates: •

Fixed roof tanks or bunds 4.0 litres/min/m².

•

Floating roof tanks 20.0 litres/min/m².

Minimum discharge times: •

Tank - Class I and II products 45 minutes. Class III (white) products 30 minutes.

•

Tank roof seals 20 minutes.

• Bunds 60 minutes (area 10 m x 10 m). Minimum number of foam pourers for fixed roof tanks or bunds: Tank dia (m) Number of pourers Bund area (m²) Less than 24 1 450 24 to 36 2 1020 36 to 42 3 1380 42 to 48 4 1810 48 to 54 5 2290 Over 54 6 2380 (Foam pourers for bunded areas would normally be by portable branch pipe.) (iii)

Sub-surface foam systems (base injection) Such systems are used for the protection of fixed roof storage tanks in which foam is injected near the base of the tank, and rises to the surface through the product in the tank (see section 15.01.07 for further information). Minimum foam solution application rates: •

Class I, II and III products: 4.0 litres/min/m² (excluding black oils or bitumen)*. Minimum discharge times: •

Class I and II products: 45 minutes.

• Class III (white off) products: 30 minutes. *Fires in tanks containing black oils or bitumen can give rise to hot zones of over 100 °C which may cause boil over as foam passes through them.

Minimum number of foam inlets: Tank diameter (m) Up to 24 24 to 36 36 to 42 42 to 48 48 to 54 Over 54 (iv)

Class I, II products 1 2 3 4 5 6

Class III products 1 1 2 2 2 3

Semi-subsurface systems Such systems are used for the protection of fixed roof storage tanks containing foam destructive products by applying foam to the burning product surface via a flexible hose rising from near the base of the tank. As the foam is not in contact with the product until it reaches the surface, semi-subsurface systems are useful for protecting water soluble product such as alcohols, ketones or blends of gasolines with more than 10 per cent alcohols. Minimum foam solution application rates: •

Foam destructive products: 6.5 litres/min/m².

Minimum discharge times: •

Foam destructive products: 60 minutes.

Minimum number of foam inlets: • (v)

Same as for sub-surface systems.

Foam spray systems Such systems are used for the protection of flammable product spills at such facilities as bulk vehicle loading gantries by discharging a spray of foam (aspirated or non-aspirated) onto the spill. Minimum foam solution application rates*: •

All products:up to 10 m fall: 6.5 litres/min/m².

•

All products:over 10 m fall:8.0 litres/min/m².

Minimum discharge times: •

Bulk vehicle gantries 10 minutes plus 10 minutes back up.

•

Other:10 minutes.

Note: Items (c)(i) to (c)(v) above are selected extracts from BS 5306 Section 6.1:1988 which have particular application to PETRONAS marketing installations and depots. For fuller information on all aspects of low expansion foam systems reference should be made to the BS 5306 or to NFPA 11 which is roughly similar. (d)

Water Pressure Pressure is needed to propel water and/or foam through fire main systems and to throw water or foam high enough to reach the tops of tanks or far enough to reach targets too hot or inaccessible to approach. Foam making equipment (inductors, generators and mobile units) require minimum water pressures (specified by manufacturers) to operate effectively. Whether the water is taken direct from a city supply main or from own pump output, the design calculations must allow for pressure losses in all branches of the fire main, hydrants, hoses, etc., which are downstream of the outlet for the fire pumps. Figures 15.01.08 to 15.01.14, inclusive, give data on pressure losses as well as the flow and pressure requirements of various units of fire fighting equipment. As a guide the aim should be for a mains pressure of 7-10 bar gauge at the hydrant furthest from the pump discharge. This would give adequate pressure to operate normal fire fighting equipment. However, as it would create rather higher pressures at the hydrant outlets nearer to the pump discharge, care must be taken with the use and handling of hoses under such high pressures. A maximum of 16 bar nominal design pressure is recommended for hose systems. Alternatively, the pump discharge pressure should be reduced if only hydrants close to the pump are in use. Pressure gauges installed at suitable hydrants will facilitate this and avoid lowering pressures below that required.

15.01.04.

Fire Pumps Where water pumping has to be provided, but may be supplemented by outside help within reasonable time, it is recommended that the total water requirement be shared by at least two identical pumps each providing not less than 60 per cent of the total. Where no outside help is available then three pumps should be capable of providing 3 x 60 per cent of the full requirement. While the main pump may be electrically driven for quick starting, ease of operating and remote starting possibility, the second (stand-by) pump should have a separate power source, preferably a diesel engine, particularly where electric supplies may be unreliable. All wiring and switch gear should be independent of all other electrical circuits and protected so that the fire pumps remain unaffected in an emergency causing damage or necessitating the isolation of normal circuits.

*Rates apply to all types of foam concentrate(P, FP, FFFP and AFFFF) however only FFFP and AFFF concentrates can be used for non-aspirated spray system, at 4.0 and 6.5 litres/min/m² in place of the 6.5 and 8.0 rates above. Detailed and clearly printed instructions for starting and operating each fire pump should be displayed at the pump site. As many of the installation staff as may be required for an emergency should receive training in the use of the equipment. The site chosen for fire pumps should be strategic (note: prevailing wind), separated from each other, and safe from vandalism, sabotage and any foreseeable source of fire (e.g. drainage outlets). Particular care must be taken to provide separate pump suction intakes for each pump of adequate size for the design maximum flow rate, positioned so as to be always below lowest water/tide level, protected by a screen from damage or clogging with vegetation or other matter and, ideally, provided with a means to back-flush particularly in rivers or harbours. Manufacturers of diesel and electric-driven fire pumps sets usually offer certain models to meet accepted industry design standards. The standard laid down by the National Fire Prevention Association (NFPA 20) is particularly stringent and would certainly meet the operating requirements of marketing installations or the requirements of insurance companies (e.g. UL, Factory Mutual). 15.01.05.

Fire Hoses and Accessories Fire hoses and accessories such as stand pipes, branch pipes, water and foam monitors, inductors, generators, nozzles and couplings should be provided as necessary, see Figures 15.01.10 and Figure 15.04.13. Fire equipment boxes (hydrant boxes) should be distributed throughout the installation and should each contain sufficient equipment to enable an immediate initial hose attack to be mounted from the hydrants nearest to potential fire sites. Hose couplings should conform to local national standards. If such standards do not exist it is recommended use by made of the 2.5 inch instantaneous couplings described in MESC 96.22.10 and Figure 15.01.13. In any case, equipment should be compatible with that used by local fire services and other oil companies.

15.01.06.

Foam and Water Monitors These units (see Figure 15.01.11 for example) are normally chosen according to the desired capacity required. Most models are dual purpose - i.e. they can be used to throw water for cooling purposes or foam for fire fighting or blanketing product spillages. Smaller, portable units are usually more appropriate for marketing installations and depots as they can be man-handled by one or two men, and are relatively easy to set up in most locations. Larger units usually have to be mounted on wheeled trolleys which require some form of transport and therefore better means of access to targets, or they can be fixed e.g. at filling gantries.

15.01.07.

Sub-surface(Base Injection) And Semi-sub-surface foam For Storage Tanks (a)

General Description In the sub-surface foam system, fire fighting foam is injected through one or more inlets in the tank shell near the base of the tank. The injected foam then rises freely to the surface to form a stable fire-resistant blanket and in the process sets up circulation currents in the product which remove heat from the burning surface, see Figure 15.01.17. Unlike foam applied from the outside of the tank by branch pipe or monitors, which can be blown away by the wind or the hot up-draught of the fire or can be obstructed by a damaged roof structure, sub-surface foam suffers hardly any wastage and practically all of it reaches the product surface. A further advantage is that the inlets being at the bottom of the tank are relatively safe from damage. The following summary lists a number of advantages and limitations in using sub-surface (base injection) and semisurface foam in storage tanks: Advantages: •

Rapid response with minimum demand on resources, water supply, foam compound and manpower.

•

High resistance of the system to damage during tank explosion or fire.

•

Design application rates of foam are achieved with 100 per cent of the foam reaching the tank.

•

Circulation of cold fuel dissipates hot fuel layers near the burning surface and aids extinction.

•

The system is simple to operate and maintain.

•

Existing product pipelines into the tank can often be used as inlets for foam.

•

Suitable for unskilled operation or automatic initiating at a safe distance from the fire.

Limitations: •

Sub-surface cannot be used with polar solvents or water miscible liquids, in such cases semi-subsurface may be used.

•

Not suitable for open top floating roof tanks where foam distribution may be uneven, due to the configuration of the roof.

•

Foam inlets must be above any water layer in the tank.

•

Extra inlets to the base of the tank may be required if existing product lines cannot be used.

•

See also 15.01.07 (b) iii and 15.02.01 (h).

Sub-surface foam is not feasible for tanks containing: (i)

(ii)

Black oils or bitumen - because, if they burn for more than 5 to 10 minutes before injection of foam starts, hot zones with temperatures exceeding 100 °C are formed which are likely to convert the foam to steam and cause dangerous frothing or boil-over; for white oils the hot zones stay far enough below 100 °C for this not to occur. Water soluble chemical products - since water-based foam is destroyed as it bubbles through such products, and in addition the need for gentle application of alcohol resistant foams precludes application by base injection.

One possible solution to both these obstacles is semi-sub-surface foam in which foam is injected through a sealed container which is attached to the outside of the tank shell and which contains a folded hose (see Figure 15.01.20). The hose is forced out of the container by the foam/air pressure breaking the seal, and is pushed up through the product to the burning surface where it expels the foam to extinguish the fire. Thus the foam does not come into contact with the product until it reaches the product surface. PETRONAS experience with this device, available from two different suppliers has proved to be effective, and is recognised in both British and NFPA standards.

(b)

Recommendations Sub-surface injection is generally regarded as one of the most effective means of extinguishing white product petroleum fires in fixed roof tanks. Nevertheless, a decision whether or not to install such a system on one or more tanks in a tank farm should take account of the following: (i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

It is more difficult to extinguish fires by conventional means in largediameter and high tanks than in small and low tanks. To extinguish a fire in a large-diameter tank requires a high foam flow rate owing to the greater product surface area, and with high tanks there is the difficulty of throwing the foam sufficiently high. Sub-surface injection therefore offers greatest improvement over conventional methods of fire fighting for large-diameter, high tanks which are more difficult to tackle using hoses, branch pipes and monitors. Irrespective of tank diameter or height, sub-surface injection has the advantage that it is relatively safe from damage or obstruction should an explosion distort the roof or tank shell. Although properly fitted and maintained internal floating covers are an important means of reducing the risk of fires in fixed roof tanks, they are not regarded as sufficiently reliable or fire proof to allow dispensing with fixed fire protection. Therefore such tanks should be treated as if they had no internal floating cover except that the fitting of a minimum of two foam inlets reduces the risk of obstruction should a cover sink or become jammed. A fixed sub-surface injection system and to a lesser degree of semi-fixed system [see (c) below] require less manpower and time to start up and operate than conventional hose systems. This is a particular advantage in areas where municipal fire brigade support is either slow or inadequate, or own manning level is low. Only fluoroprotein (FP), film forming fluoroprotein (FFFP), or aqueous film forming foams (AFFF), or universal alcohol type concentrate (ATC) will tolerate severe mixing with the product sufficiently to be suitable for subsurface injection. FP and FFFP are preferred as they form a more stable blanket to seal the burning surface. Standard protein foam and alcohol resistant foam (ATC) is not suitable for sub-surface application. ATC foam requires gentle application through semi-subsurface injection. Where outside developments exist or have approached installation/depot boundaries such that, in spite of safety distances, there is an increased risk and consequence of fire, both to the installation/depot and to the outside environment, sub-surface injection may offer a practical and economic means to improve both the speed and effectiveness of response. In spite of the foregoing, there are locations where the risk of a fire starting and/or of consequential damage or operational disruption may be judged too small to warrant the cost of conversion of all or any tanks to subsurface injection, e.g. some up-country depots in isolated areas and at small storage points. However, consideration should be given to installing a connection on the tank product inlet line.

Careful appraisal of the above factors in relation to local circumstances is therefore warranted. If sub-surface injection is being seriously considered, money can be saved initially by fitting the necessary foam inlets and valves when constructing new tanks or emptying/cleaning existing ones with a view to conversion at a later date. Design of sub-surface injection systems, even for initial cost estimates, requires careful thought by competent engineers. A PCbased design package (SMTAFF) is obtainable from SIPC.

(c)

Type of System Sub-surface foam injection facilities can be installed either as a fixed system in which all equipment is permanently in place or as a semi-fixed system based on portable or mobile foam generating equipment and hoses brought and connected up at the time of the fire. With either system the foam can be injected either direct into the tank through dedicated foam inlets or via existing product lines. The choice of which system to use should be based on a cost versus benefit analysis of the alternatives taking into account the advantages and disadvantages given in the following descriptions. (i)

Semi-fixed System The fixed part of the system consists of the foam line which runs from outside the tank bund to the tank inlet(s) and is fitted with suitable valves and an inlet manifold to which the foam generators can be connected when needed. Since the tank valve has to be open to permit foam to enter, it must either be remotely operated or be left permanently open, in which case it is necessary to fit a second steel tank valve outside the bund and a bursting disc downstream between the tank valve and check valve to contain the tank contents. If manually operated the valve outside the bund must be located and protected such that an operator can get to it quickly and open it even when the tank and/or bund is on fire. A possible arrangement is shown in Figure 15.01.21. The foam concentrate, proportioners, and generators can be carried in a van or trailer and brought to a fire when required, for connection by hoses between the water supply hydrants and the foam lines. Foam generation is initiated by opening the water supply and foam line valves and maintaining adequate supplies of water and foam concentrate. The main advantage of the semi-fixed system is that only one set of generators, proportioners and foam concentrate is needed to cover perhaps several tanks or different groups of tanks. This however carries with it the main disadvantage of the system which is that it obviously takes time to connect and start foam injection, and in addition a means to transport the foam and equipment to the appropriate foam line manifold must be provided and kept in constant readiness. Furthermore, suitable and protected access to every foam line or manifold connecting point must be provided.

(ii)

Fixed System The foam line and valve requirements within the bund are much the same as for the semi-fixed system, but outside the bund all foam proportioners and generators plus a foam concentrate tank or supply line are installed as fixed parts of the system (see Figures 15.01.22 to 15.01.24 inclusive). An obvious advantage of the fixed system is the speed with which it can be operated, since there is no delay while bringing up foam and equipment, connecting hoses, etc. A disadvantage is the cost of the greater number of generators, proportioners and foam concentrate tanks that may be required. However, judicious layout design can minimise this by grouping tanks so that each battery of generators and related equipment will serve several different tanks. One, two or at the most three such batteries will normally be sufficient to cover most marketing tank farms. Generally, therefore, the fixed systems is to be preferred since the additional cost is not large compared with the longer delay and lower reliability of the semi-fixed system which requires more manpower and the need to maintain equipment in constant readiness.

(iii)

Separate Foam Inlet or via Product Line For either fixed or semi-fixed systems the choice lies between injecting foam through dedicated foam lines connected direct to the tank or via existing product (inlet) lines (see Figure 15.01.22). Use of the product outlet line is less attractive as it is more likely to be complicated with branches, pumpsets, etc. and better kept free for possible use to empty a tank in the event of a fire. Nevertheless provided that the product inlet line is of large enough diameter (see Appendix 15.02.01 l(iv) Velocity Restrictions) its use will usually be simpler and cheaper since the necessary pipeline modifications can be made without emptying and gas-freeing the tank. However, careful thought must be given to the location of the connection to the product line since the finished installation must allow for the tank valve being kept open or being operated in the event of a fire, and there must also be a valve upstream of the connecting point to prevent back-flow of foam in the wrong direction. Where the inlet line is not large enough to accommodate the full foam flow without exceeding design velocity limits, then an additional or alternative foam inlet line will be necessary. If it is decided to use separate foam inlet lines then again the tank valves must either be kept open or remotely operated in the event of a fire.

(vi)

General Arrangement Deciding on the disposition of the various system components (pumps, inductors or proportioners, generators, foam solution lines, finished foam, lines, valves/bursting discs, etc.) requires careful consideration of a number of factors. These relate primarily to the distance between the water supply pump and the tanks to be protected; the high back pressures on the system caused by the product heads in the tanks; the need for the foam inlet valves being open at the time of starting base injection; the inability for men to operate valves or replenish foam compound within intolerable heat radiation levels of tanks or bunds on fire, etc. To illustrate one typical problem area, the simplest system may be to group pump, foam compound inductors and foam generators together so that foam can be directed via a manifold to any one of a group of tanks. This necessitates pumping finished foam all the way from the pump outlet to the tank inlet. However, if the tank is high and relatively distant the pumping pressure to achieve this may be excessive. One answer would be to locate the generators further downstream, i.e. closer to the tanks since pressure losses of foam solution are lower than those of finished foam. Then the problem becomes one of opening valves closer to the tanks without exposing men to intolerable heat radiation. We therefore recommend designing a system using bursting discs which will blow open when foam pressure builds up behind them. Some suggested layouts are discussed in Appendix 15.02.01 (under 2, Design Notes). Operating companies who have design problems that are not covered here should consult PETRONAS for further advice.

(d)

Operating Factors To extinguish a fire successfully by sub-surface injection, three operational factors are particularly important: (i)

(ii)

(iii)

(e)

Foam solution must be supplied to the generators at or above the specified minimum flow rate continuously until the fire is extinguished. Application at a lower rate for a longer duration of time will not generally extinguish a fire. Additionally, if (perhaps through lack of foam concentrate), injection has to be stopped before the fire is totally extinguished, this will allow the flames to spread back across the product surface thus losing all that one has gained up to that time. It is therefore essential that the full requirement of foam compound is assembled or immediately available before sub-surface injection operations start. (See Appendix 15.02.01). The minimum inlet pressure specified for the high back-pressure generators used (7 bar) must be maintained continuously otherwise inferior quality foam may be produced leading to extended extinction time or even failure to extinguish the fire. It is important therefore that, during the actual foam injection operation, significant changes in demand on the water supply, (which could upset the flow/pressure supply to the base injection system) do not occur. This would require a minimum of 10 bar upstream of proportioners to compensate for pressure and friction losses. If variable foam inductors are considered necessary to permit the use of different concentrations of foam compound, they should preferably be set and sealed at the correct percentage. Alternatively, a clear sign should be posted directing the fire fighters to set the inductors at the correct percentage induction rate for the foam concentrate in use. If foam concentrate is induced too slowly, poor foam will result; if induced to fast stocks will be consumed wastefully and too little foam will be produced.

Design and Equipment Guidance on the design of sub-surface injection systems is given in Appendix 15.02.01. Examples of typical foam generators and foam inductors are shown in Figures 15.01.16 to 15.01.18. A sketch showing the recommended tank inlet for base injection is given in Figure 15.01.26. A PC-based computer programme SMTAFF (refer Appendix 15.02.01(d)) has been developed to carry out design calculations - given the necessary details of tank dimensions, layout, products stored, etc.

15.01.08.

Foam Pourers For Floating Roof Tanks Several types of proprietary foam pourers are available from suppliers, the current recommendation for group companies is illustrated in Figures 15.01.27 and 15.01.28. The number of foam pourers per tank will depend on the diameter of the tank. The location of the high pressure generator will depend on whether a wind girder is fitted to the tank. Where a wind girder is installed it should be located as illustrated in Figure 15.01.27. In such cases the dry riser should be located adjacent to the top landing of the staircase. Dry risers should be hot dip galvanised internally and externally and flanged. The foam generator should be located horizontally at the top of the dry riser. Foam concentrate can be injected through flexible hoses connected to the two 2½ inch connections at the head of the staircase or from connections outside the bunded area. If additional risers are required they should be positioned around the tank circumference at intervals not exceeding 30 m for Shell type nozzles. Other pourers of non 'Shell' design should be installed at locations not exceeding a pitch of 12 m. These should be installed as illustrated in Figure 15.01.27 with the high pressure generator installed outside the bunded area. Also, if the tank is not fitted with a wind girder this drawing should be followed. In either case the piping leading to the dry riser should be laid above ground and over the top of the bund and not through the bund wall. The equipment described above has proved to be effective in extinguishing actual rim fires in floating roof tanks even when the product level is low and the roof is in its near bottom location as illustrated in Figure 15.01.29. Rim fires are sometimes difficult to detect, particularly during daylight hours when the roof is in a low position or in unmanned installations. Self contained detection systems are available from suppliers, these are mounted on the roof of a floating roof tank. A polyethylene tubing is placed circumferentially around the rim of the seal, this tubing is charged with nitrogen from a cylinder mounted in a cabinet. If a fire breaks out in the rim seal area the plastic hose melts allowing the nitrogen to escape; this is detected by a sensor which in turn activates a visible/audible alarm (See Figures 15.01.30).

15.01.09.

Distinctive Colouring Fire fighting equipment should be painted distinctively. Red is the accepted basic colour (Shell standard colour number 11), but each type of extinguisher may be painted wholly or partly in other colours for the purpose of ready identification, and a suggested arrangement used by extinguisher suppliers is as follows: Water Red Foam Cream Carbon dioxide Black Dry chemical powder Blue Instruction labelling with black letters on a yellow background is generally more clearly visible than other colour combinations. Notices indicating the location of equipment should have white letters on a red background. Fire boxes containing hoses, branch pipes and other equipment should be painted red. Fire precautions notices have red letters on a white background, e.g. no smoking, etc. Notwithstanding the above colour coding, it is important that the appropriate extinguisher should be sited in the vicinity where it can be used on the hazard for its designed purposes.

15.01.10.

Fire Alarms And Emergency Calls Suitable audible alarms must be provided with actuating points (switches) located and clearly marked in strategic positions, e.g. loading gantries, jetties and berths, pump stations, dispatch office, etc. Such alarms must, of course, be audible (or visible) at all locations - particularly remote ones such as berths and jetties. There should be no restriction as to who may sound an alarm since delays in calling for help can be critical. A notice on which the telephone numbers of the fire and emergency services are clearly recorded should be displayed near the telephone at the gate house or other control centres. All personnel, including contractors, must know what to do in the event of a fire alarm (see Plant Operating Manual 01.04.05) and fire alarm equipment should be regularly tested, e.g. at monthly fire practices, to ensure they work and can be heard at all working locations.

15.02.00.

LEVELS AND TYPE OF PROTECTION

15.02.01.

Tank Farms The level and type of fire protection required for a tank farm depends on a number of factors including tank farm location, surroundings, size and number of tanks, strategic importance, overall storage capacity and classes of product stored. In the following guidance the requirements of each class of product and each type of tank are considered separately, since in many tank farms segregated product groups can be treated differently for convenience and cost effectiveness. Where products of different classes are stored in adjacent or intermingled tankage then naturally the impact of the most highly flammable (Class I) product must be given top priority. While the part to be played by any local fire service in the event of a fire must be taken into account, the type and scale of fixed or mobile facilities will depend on the following guidelines. (a)

Class III(1) Product Storage Fire risk is very low, however, at least sufficient hydrants (each 1 000 litres/min) for 2 litres/min/m² fog needs to be provided. Should storage contain highly critical strategic stocks then water may be provided for cooling and/or extinction using portable equipment (pumps, hoses and monitors) preferably provided by the local fire brigade. For black oil products sub-surface foam (base injection) is not recommended due to the hazard associated with hot zones of over 100 °C which can form within as little as ten minutes after a tank fire starting. Notwithstanding the above, gas oil tanks located adjacent to Class I storage, should be treated as Class I tankage to facilitate possible product changes in the future.

(b)

Class III(2) Product Storage High viscosity products stored at temperatures at or above their flash points (e.g. bitumens or fuel oils) present sufficient fire risk to justify a higher level of protection than required for Class III(l) products. Dependent on the strategic situation the ability to extinguish or contain a fire should be available. Foam, applied by hoses and monitors, provides a means of applying water in the finely divided state necessary, particularly for bitumen tank fires, to minimise the risk of boil over. Alternatively for less strategic stocks, containment can be achieved by applications of water to cool adjacent tankage; even for the burning tank itself provided it is not insulated, water applied to the shell can help to cool the contents and thus reduce the fire. As for Class III(1) (black oil) products sub-surface foam is not recommended.

(c)

Class II(1) Product Storage Due to their range of flashpoints (21 °C to 55 °C) Class II products can be fairly readily ignited at other than the coldest ambient temperatures and therefore consideration should be given to fixed foam facilities also taking into account strategic importance, environment adjacent to tanks, total quantity stored and tank sizes. In normal marketing installations and depots, fixed foam should be provided, though storage tanks less than 10 metres in height can be protected by mobile equipment provided sufficient, trained manpower is readily available. Where fixed foam pourers or sub-surface foam is installed, it is important that supplementary (back-up) protection (foam and water) be provided to combat any bund or spillage fires that could occur in the tank farm area. Fixed cooling systems should also be provided if there is risk of product temperatures being raised by radiation from an adjacent fire within or from outside the tank farm. In some less significant locations with minimal exposure to potential fires manual cooling using hoses and monitors could suffice.

(d)

Class I and II(2) Product Storage At all ambient temperatures these products produce flammable vapours and fixed fire fighting and cooling facilities should be provided. Sub-surface foam (base injection) is generally recommended as the most effective system for extinguishing Class I product fires, (see also Section 13.6.7). internal floating covers (IFC's), although they reduce vapour emission, are not regarded as offering sufficiently reliable security against fires to allow dispensing with fixed foam fire protection. To reduce the risk of sunken or damaged IFC obstructing foam application, the design of the foam system should include at least two foam inlets. Fixed cooling systems should also be provided to combat the effect of heat radiation from adjacent tanks or other facilities on fire. Manual cooling systems are not normally regarded as adequate protection for Class I and II(2) storage due to the time they take to get started, and the manpower required.

(e)

Mixed Class Tankage The type and level of protection are determined largely by the presence and proximity of Class I, II(2) and III(2) products. Separate compounds for Class In products may be treated separately provided they are not exposed to radiation from other tanks (Class I, II) on fire.

(f)

Floating Roof Tanks The most common fire in a floating roof tank is a seal or rim fire. A dry riser installed up the tank shell with top pourers to supply foam into the seal space can be used. An adequate alarm system should be provided (see 15.01.32 N2 unit for 'poly-flo' line detection).

(g)

Fixed Roof Tanks For tanks requiring fixed foam facilities, sub-surface foam (base injection) is preferred due to its greater reliability and speed. Section 15.01.07 details the advantages and limitations of sub-surface systems, whilst Appendix 15.02.01 addresses the design and equipment in sub-surface systems. A PC-based design package called SMTAFF and a PC program for heat radiation calculations is available from SIPC. (Refer Appendix 15.02.01 (d)). Top foam pourers can still provide effective protection for some less critical situations mentioned above, as well as for tanks containing foam destructive products [e.g. alcohols, ketones and gasoline blends with high (more than 10 per cent) oxygenate contents] which require gentle surface application of foam rather than the intimate contact inherent in sub-surface foam systems. An alternative system for foam-destructive products is semi-subsurface foam. In this system foam is injected through a hose fixed near the base of a tank whose outlet floats to the top of the product during operation thus keeping foam and product separate, prior to gentle application from the hose. See Figure 15.01.20.

(h)

Fixed Roof With Internal Floating Cover (IFC) Although an IFC reduces the vapour emissions in a fixed roof tank it is not considered sufficiently reliable or fire proof to enable any reduction in the level of fire protection required. Such tanks should therefore be treated as normal fixed roof tanks for fire protection purposes [see (g) above]. Though not recommended, where steel pan IFCs exist, sub-surface foam is not suitable, as a sunken pan could obstruct foam inlets. Any such tanks may be protected by top foam pourers.

15.02.02.

Bulk Vehicle Loading Gantries For loading bays handling Class I, II(2) or III(2) products, the fire main and hydrants system should run close enough (20 mm minimum) to permit application of foam and/or water from at least two directions. This is to facilitate access in the event of obstruction by abandoned vehicles, as well as difficulties caused by wind direction. At unmanned or low level manpower installations and depots consideration should be given to installing fixed foam or water deluge systems at loading gantries with more than four loading positions. The intensity of use (number of vehicles loading/waiting at peak times), the level of control of safe loading operations (proportion of PETRONAS to non-PETRONAS drivers), the effectiveness of emergency spillage/fire response, and of the standard design (refer the Loading and Discharge Manual - Road) are all factors which will influence the decision. Bottom loading gantries with overfill protection and other automated controls are considered less vulnerable, but fixed systems may be justified on the basis of strategic importance, large size of facility, local authorities' views and environmental considerations. The advent of unmanned depots is reducing the degree of human control and intervention to the extent that automatic response in the event of a fire is becoming a necessity. For this reason loading gantries in unmanned locations should be equipped with: •

An automatic fire detection system capable of: -

Quickly detecting flames in the gantry area. Turning off power on-site except emergency lighting, communications equipment and fire fighting facilities. Raising an alarm at the local fire service. Signalling to the main terminal/administration centre that a fire has been detected.

•

An automatic fixed foam sprinkler linked to the above system and capable of fire suppression by spraying foam over the gantry area.

•

An emergency stop valve at each loading bay as for conventional depots.

Note: Fire detectors should be mounted and located so that the entire area is under surveillance. Detectors should be highly resistant to deceptive phenomena, such as headlamps and reflected sunlight; however very sophisticated detectors (e.g. infra-red light beams) are not necessary for this purpose. As such automatic spray systems only cover the immediate gantry area, protection will still be needed to tackle possible fires that may occur or spread to parked vehicles and other facilities in the vicinity of the gantry. For fuller details of the requirements and design of gantry fire protection systems reference should be made to PETRONAS. For a small number of bays or filling points handling only Class II(1) or Class III(1) products, mobile wheeled units should give sufficient protection. 15.02.03.

Rail Tank Wagon Filling or Discharge Facilities Many of the same considerations apply as far as for road loading facilities (above), except that human involvement during loading/discharge operations is normally limited though they are normally PETRONAS staff. As a minimum the ability to lay down foam at any part of the area is a necessity at the rate specified for spills, (i.e. 5.0 litres/min/m² foam solution reference 15.01.03 above) plus separate application of cooling water on exposed railcars or other plant. As for vehicle facilities thought should be given to fixed/automatic systems at least for loading operations since the strategic importance of such facilities is likely to be high.

15.02.04.

Berths And Jetties (See International Safety Guide for Oil Tankers and Terminals ISGOTT). The type and quantity of fire fighting equipment should be based on an assessment of the total risk and be related to the size and location of the berth, the layout of the installation, the types and throughputs of product handled, and the hazard to and from adjacent or jointly operated facilities. The aim is to provide adequate protection for the jetty in the event of a shore or tanker fire, in particular the loading and unloading arms and hoses, and related pipework. Such a system should also be capable of providing assistance to a berthed tanker particularly in the area of its manifold. Fire on a berthed tanker can usually be fought more easily if the tanker is kept alongside the wharf or jetty, and at larger ports the harbour authorities should preferably provide sufficient floating fire fighting equipment to tackle a ship fire and/or supplement shore fire fighting efforts. For this, easily accessible hose connections should be provided to enable tugs' fire pumps to charge the installation fire main if necessary. At installations which have jetty/wharf berths handling Class I and II cargoes and accommodating ships of 18 000 tonnes and over, or receiving more than 60 ships per year with a throughput exceeding a half million tonnes per year, fire protection facilities should be provided as follows: (a)

Fire Mains A fire water main to each berth or jetty head, together with hoses and equipment. Water mains should terminate in double hydrants. There should be one double hydrant for each 60 m length of the largest ship which the jetty can accommodate. Hydrants and fire equipment must be sited to permit the main concentration of fire fighting to be aimed at the shore/ship manifold area, but at the same time providing some cover throughout the length of the berth. Accessibility and protection from exposure to fire must also be considered. Based on the maximum size of tanker acceptable at the berth, the water main should be capable of supplying 50m3/hour for each 30 m length of ship at a minimum pressure of 10 bar under full flow conditions at the most unfavourably 3 sited hydrants, up to a maximum total flow rate of 250 m /hour. This will permit the use of mechanical foam generators (see Figure 15.01.14 or high-pressure spray nozzles, see MESC 96.28.20. Hydrants should not be located too close to risk areas (20 m minimum). Fire towers are not normally recommended for marketing installations. Where fire towers have been erected, one or more branch lines should be installed to supply water to fixed monitors, installed on top of the tower. The monitors should preferably be dual controlled (local and remote) and should be able to throw jets of water over a distance equal to the beam of the largest tanker likely to use the berth, and should be capable of delivering water, fog or spray as required. Water jets are intended for dealing with fires on ship's superstructures until close range fire fighting can be carried out. Fog or spray jets are particularly useful for cooling purposes and to provide a protective curtain or water to assist personnel in gaining access to or escaping from the ship. Water supplies may be from the harbour or other open source, or from an extension to the installation fire water main. Where jetties or berths are remote from installations it may be necessary to install separate pumps or connections for the local fire service (shore or harbour) to connect their pumps. Where the jetty or berth is either shared or operated by third parties (other oil companies, harbour authorities) specific arrangements must be made to ensure a viable fire protection system, properly maintained and manned when required.

(b)

Stocks of Foam Compound Foam compound should be readily available either in bulk or on a mobile trailer for quick delivery to the fire site. Depending on the rate or application, an 3 appropriate quantity of foam concentrate would be 0.5m /30 m length of ship. For berths where chemical products are handled, consideration should be given to the different types of fire fighting equipment that may be required as well as various types of foam compound.

(c)

International Shore Fire Connection The purpose of the International Shore Fire connection is to connect the fire water supply from shore to ship's fire main or to interconnect the fire mains of two ships. Reference should be made to Appendix E of the International Safety Guide for Oil Tankers and Terminals.

(d)

Portable Fire Fighting Equipment In addition to the above fixed equipment, sufficient hand and mobile fire extinguishers should be provided at all berths or jetties to enable an immediate attack to be mounted on any small fire that may occur on or near the berth, see Appendices 15.01.01 and 15.01.02. Fire fighting equipment for small berths or those handling a few small vessels and/or barges, or those handling only Class III products. At small berths handling ships of less than 18 000 tonnes and at a frequency of less than 60 ships per year, or handling only Class III products, at least two 275 kg or four 150 kg dry chemical or equivalent foam units should be provided unless equivalent or better protection is already available on the jetty. For bulk barge traffic only, carrying Class I, II or III products, the number and size of mobile units may be reduced to a minimum of two 70 kg dry chemical (or equivalent foam) units provided such movements are infrequent and the risk of a fire spreading to neighbouring facilities is insignificant.

(e)

Escape routes Some types of berth and jetties can be particularly difficult to escape from the event of fire or other emergency and careful thought must go into providing more than one means of escape. A selection of the following should be considered: -

Access ways to and from and between off-shore berths/dolphins: personnel must not be left unattended on isolated dolphins. - Small boat with both motor and paddles in case oil spillage makes use of motor unsafe. - Fire protection blankets to enable men to escape to shore perhaps by running through flames. - Life belts in prominent and accessible positions. - Steel steps or ladders between berth deck and water level. Clear notices detailing actions to be taken in an emergency as well as indicating escape routes should be prominently displayed. 15.02.05.

Fires Involving Electrical Equipment Because of the risk of electrocution, water or foam are not safe to use on electrical equipment. Carbon dioxide extinguishers are preferred. Dry powder is also effective but should be used only when carbon dioxide units are not available since dry powder tends to corrode electrical switch gear, instruments, etc. For the protection of computer facilities see 15.02.06 below.

15.02.06.

Protection Of Computer Facilities In the past Halon was recommended for fire protection associated with computer facilities, this is not longer the case (see Appendix 15.01.04). It is now recommended that an early warning smoke detector is installed with a two or three level function. The first function to trigger an alert situation and the second a fire situation. In addition to any circuit breakers that are fitted to the computer equipment a second circuit breaker is recommended at a location removed from the computer complex so that the circuit can be deactivated without entry to the computer complex. With a three level system the first level is a staff alarm warning, the second an actual fire alarm and the third activates the fife extinguishing media. These systems have a capability of affecting protection and cut-out of the unit at risk without interference to other units concerned in a multiple installation. Where manual installations are involved a secondary escape route for personnel evacuation is recommended.

15.02.07.

Fires Involving Chemical Products At installations and depots where chemical products are stored, recommendations on fire fighting are as follows: (a)

Water Immiscible Solvents Fires involving solvents such as SBPS, benzene, toluene, xylene, white spirit, etc., can be extinguished using dry powder, fluoroprotein, or aqueous film forming (AFFF) foams. Foams can be applied in the same manner and the same time application rates as for fires involving petroleum products (see 15.01.03 (c)) including sub-surface methods (see 15.01.07).

(b)

Water Miscible Solvents Fires involving chemical solvents such as ketones, alcohols, IPA, etc. can be extinguished by the gentle application of. •

Special 'alcohol-resistant' or 'all purpose' type foams at foam solution flowrates of 4.1 to 9.8 litres/min/m² depending on the solvents. Advice should be sought from the foam supplier.

For fire involving blends of gasoline with not more than 10 per cent oxygenates (alcohol or ether), fluoroprotein foam can be used at an application rate of 6.5 litres/min/m²; note that application must be smooth and gentle. Spillages of alcohols can be rendered less flammable by flooding with water, e.g. alcohol mixed with more than 20 per cent water becomes equivalent to a Class II product; with more than 92 per cent water it is equivalent to a Class III product. Care must nevertheless be taken with run-off since very small percentages of alcohol in water are toxic to human/animal/plant life and normal oil/water interceptors will not separate solutions of alcohol in water. It is generally recommended that where the quantities of chemical solvents stored are small relative to oil products, fire fighting should be based on fluoroprotein foam rather than the special all purpose/alcohol resistant types. This avoids the complications of holding two types of foam concentrate and of organising fire fighting procedures to ensure the correct foam is used in the event of a fire. In addition, although chemical solvent tanks require three times the application rate, in most cases this will amount to a flow no greater than that provided for the larger oil product tanks. Where all purpose/alcohol resistant type foams are nevertheless considered necessary, they are obtainable from most foam suppliers, and can be applied using standard foam-making equipment but not by sub-surface injection (see below). As these foam concentrates tend to be slightly acidic, all equipment must be thoroughly washed after use and any bulk compound containers must be specially lined. Gentle application of universal/alcohol resistant foams to the burning surface of alcohols is essential to obtain control and extinction of a fire. This is because, to prevent foam breakdown, when the initial foam contacts the surface of the product, a polymer film is formed on the surface. This film acts as a physical barrier to prevent the breakdown of any further foam applied to the product surface and thus allows the foam layer to build up until extinction is achieved. If the foam is applied forcefully, the polymer film disintegrates and a foam layer cannot build up. The recommended technique is to direct the foam against any vertical or sloping surface and so allow it to run down onto the fire, or to bounce it off an adjacent flat surface. Although application by a sub-surface system is obviously not acceptable because of the intimate mixing of the foam with product as it rises through the product, an alternative system is semi-subsurface foam injection, which employs a flexible hose fitted to the foam inlet line inside the tank. As foam is pumped into the tank the hose unfolds, floats to the surface thus keeping foam and product separated from each other until the foam reaches the surface, see Figure 15.01.20. PETRONAS experience with this device has proved to be effective and is recognised in both British and NFPA standards. (c)

Other Chemical Products If fire protection has to be provided for chemical products outside the above two categories, advice may be found in the SICC 'Handling and Safety Manual', 'The Depot Manual', and the 'PETRONAS Guide to the Warehousing of Chemicals' and Pesticides - A Safety Guide'.

(d)

Toxicity Many agricultural products and some industrial and plastic products produce toxic vapours in a fire. Fire fighting personnel may therefore require breathing apparatus and protective clothing. Only personnel properly trained and experienced in the use of breathing apparatus should be so employed since inexperienced users may put themselves at considerable risk if they are not fully aware of the hazards and the means to overcome them. Water used for fire fighting may become contaminated by toxic products and must be prevented from escaping into public drainage systems or water courses by temporary bunding arrangements. If such bunded areas are to be made drainable then their drainage systems should be segregated and the collected drainage should be recoverable. Other precautions are to separate products presenting different fire hazards, e.g. toxicants and flammables and to minimise the use of water, as far as possible, by basing fire protection on dry powder or foam extinguishants. Reference is made to the PETRONAS publication 'The PETRONAS Guide to the Warehousing of Chemicals'.

15.03.00.

FIRE FIGHTING AGENTS

15.03.01.

Types of Fire Fires are classified as follows: A

Dry fires: Combustible solid materials such as paper, wood, textiles.

B

Oil/Grease fires: Liquids (hydrocarbons) or liquefiable solids. Foam is normally used to blanket these fires. The effect is to prevent oxygen from reaching the fire and to cool (by means of water in the foam) at the same time. Dry chemical or inert gas (extinguishers) can also be used, but they do not always blanket the liquid and flash-backs can therefore occur.

C

Gas fires: Methane, propane, butane, etc. Inhibiting agents such as dry chemical powders or inert gas are normally used, but such fires should usually only be extinguished after the gas supply has been turned off. Water sprays are also effective in reducing the intensity of gas fires.

D

Metal fires: Magnesium etc. These are not normally applicable to the oil industry.

If the fires involve electrical equipment of any kind and the current cannot be switched off, water and water based agents (i.e. foam) must not be used. 15.03.02.

Water Fresh or salt water can be applied in the form of jets, sprays or fog. Sprays and fogs are more effective than jets for hydrocarbon fires because the particles of water are more easily vaporised; the process of extraction of latent heat of vaporisation has a cooling and therefore dampening effect upon the fire. Normally jets of water should not be used as their effect is to spread hydrocarbon fires, the exception being if maximum throw is required, for example against strong winds. The main uses of water for fighting fires are: •

Extinguishing Class A fires (see Appendix 15.01.03).

•

Spray cooling of burning product surfaces and equipment adjacent to the fire.

•

Producing fire fighting foam.

•

Protection of personnel (sprays).

•

Directing pools of (burning) liquid.

•

Dispersion of escaping gases and vapours.

15.03.03.

Foams Mechanical foams are made from mixing foam concentrate with water and then aspirating the emulsion. Low expansion foams are normally used for Class B (liquid hydrocarbon) fires. Correctly applied foams form a sealing blanket, have a smothering effect on the fire, suppress flammable vapours and cool the product, by shedding water. Foams are not suitable for extinguishing LPG fires; reference should be made to the LPG Manual. Although protein-based foam compounds will gradually deteriorate during long-term storage, particularly in ambient temperatures above 21 °C, much can be done to preserve this valuable asset. Plant Operating Manual Volume 1, 07.02.02 (iii), describes measures that should be taken to prolong the shelf life of foam compounds. As a control measure compound containers should be date marked when received so that they can be used on a first-in first-out basis for fire training and fire drills. Notwithstanding the efforts taken there will be a need on occasion to test the quality of foam compound and a simple field test is described in Plant Operating Manual Volume 1, 07.02.02. The main types of foam are as follows: (a)

Fluoroprotein foam (FP) Fluoroprotein foam comprises protein foam concentrate with added fluorinated agents. It has largely replaced standard protein foam for fighting hydrocarbon fires because of its better performance, higher fluidity and greater resistance to fuel entrainment - particularly valuable for sub-surface injection into storage tanks, for which standard protein foam is unsuitable. Fluoroprotein foam can be used with fresh or sea-water. Alcohol resistant types of fluoroprotein foams are also available; they are not suitable for sub-surface injection.

(b)

Aqueous film forming foam (AFFF) Because of its high fluidity, AFFF gives a rapid knock down of fires. It forms a thin aqueous film on the fuel surface which acts as a barrier to exclude air and is capable of suppressing the development of vapours. However, it is less suitable for fires after long pre-burn times especially where protruding hot steel work may destroy the thin foam film. For high-risk areas such as vehicle loading bays, the use of AFFF provides both rapid knock down and a sealing layer. AFFF is effective for covering a spillage to prevent a fire from occurring. It can be used for sub-surface injection in the same way as fluoroprotein foam. It can be used with fresh or sea-water. Alcohol resistant universal types of AFFF (synthetic detergent-based) are also available, but are not suitable for sub-surface application or for application on aviation kerosine and therefore should not be used for this purpose.

(c)

Film Forming Fluoroprotein (FFFP) This combines the properties of FP and AFFF foams, thus giving rapid fire knockdown plus burnback resistance. It can be used with fresh or sea water, in all normal foam generating equipment, and is suitable for sub-surface application.

(d)

Alcohol Resistant Foam (ATC) This type of foam is of particular use for fires involving water miscible chemical products (e.g. chemical solvents, ketones, alcohols, etc.) It forms an insoluble membrane on the surface of the burning liquid, thereby preventing direct contact between foam and liquid. Gentle application is essential to avoid disturbing the membrane, and for this reason its use by sub-surface injection is not possible though it can be applied successfully by semi-subsurface injection.

15.03.04.

Carbon Dioxide Carbon dioxide being an inert gas extinguishes a fire by dilution or displacement of air. It is particularly effective in sheltered locations containing electrical switches, motors or other equipment. However, because of its suffocating effect it use in unventilated spaces should be avoided except by an automatic atmospheric flooding system for locations where nobody is present. Carbon dioxide is not normally used for computers or other sensitive electrical equipment (see 15.02.06).

15.03.05.

Dry Chemical Powders Dry powder generally provides the quickest means of extinguishing fires of flammable liquids, though it has little cooling effect and does not form a sealing blanket on the product surface. By interfering with the chain reaction of combustion, dry powder acts more rapidly than foam and is particularly suitable for dealing with fires of free-flowing liquids or fires which may spread to surrounding materials before a foam blanket could be formed over the burning liquid. Dry powder is a non-conductor of electricity and can safely be used on fires where there may be a risk of electric shock. It is not, however, the most suitable agent for computers or other sensitive electrical equipment as it leaves a residue. There are two main types of dry powder: (a)

(b)

Sodium or potassium bicarbonate powders - most suitable for Class B and C fires and therefore recommended for most product distribution applications. Monnex is a particular brand of potassium bicarbonate powder which, though expensive, is the best available for petroleum fires. Mono-ammonium phosphate powders - so called multi-purpose powders - which though suitable for Class A, B and C fires are not so effective on liquid hydrocarbon fires and therefore not so appropriate for marketing distribution facilities.

Appendix 15.01.01 : RECOMMENDED 'FIRST-AID' FIRE EXTINGUISHERS

Appendix 15.01.02 : RECOMMENDED SCALE OF FIRE FIGHTING EQUIPMENT INSTALLATIONS (INCLUDING LOBP- Note (7), AND CHEMICALS – Note (5) BUT EXCLUDING LPG PLANTS)

Appendix 15.01.03 PLANNING AND PROVISION OF EXTINGUISHERS The following extracts from BS 5306 (British Standard 'Code of Practice for Selection - Installation of Maintenance of Portable Fire Extinguishers'), Part 3 may help selection of correct type, size and number of extinguishers for different situations. For a more thorough treatment refer to BS 5306, Part 3. 1.

INTRODUCTION The scheme of classification and rating given in BS 5423 (specification for Portable Fire Extinguishers) makes it possible to specify the distribution of extinguishers in buildings according to extinguishing capability rather than by extinguisher type and size or content. According to this scheme, extinguishers are marked with numbers and letters indicating the relative maximum size and type of fire they are capable of extinguishing (under the conditions and procedures set out in BS 5423). For example, an extinguisher marked '8A' is capable of extinguishing a class A test fire of size 8A, and an extinguisher marked '13A' is capable of extinguishing a class A test fire of size 13A. Similarly an extinguisher marked '55B' is capable of extinguishing a class B test fire of size 55B. Extinguishers with both class A and class B capability are marked accordingly, e.g. 13A/55B.

1.1.

CLASS A FIRES (SOLIDS, WOOD, PAPER MATERIAL) Class A materials are generally present in all premises and occupancies. The basic scale of provision of extinguishers where these are the only primary first aid means of fire defence is that, on each storey, there should be at least two extinguishers sited in suitable positions. The total class A rating of all extinguishers on that storey should not be less than 0.065 x floor area of 2 storey (in m ), and in no case less than 26A (see note). This minimum requirement corresponds 2 to a floor area of 400 m . However, in the case of buildings in single occupancy with upper floor area not exceeding 100 m² the minimum aggregate rating required for these floors is 13A, and there need not be two extinguishers per floor on the upper floors. The extinguishers tests of BS 5423 are made under draught-free conditions. Class A fires are more difficult to extinguish and more liable to re-ignite, outdoors or indoors where there are air currents. Under such conditions powder, water or foam extinguishers are recommended. Note: The assumption is made that a 9 litre (2 gallon) water extinguisher can achieve a 13A rating.

1.1.1

Example - Minimum Provision for Class A Fires 2

For a single storey building of floor area 1 600 m the minimum aggregate class A rating is: 0.065 x 1 600 = 104A (see BS 5306 Part 3) This aggregate rating can be provided in one of a number of ways. For example: 8 x 13A extinguishers = 104A (2 x 27A) + (7 x 8A extinguishers) = 110A 4 x 27A extinguishers = 108A 3 x 43A extinguishers = 129A (1 x 43A) + (5 x 13A extinguishers) = 108A Note that the travel distance for any point on the floor to the nearest extinguisher should not exceed 30 m. This may mean that extinguishers additional to this minimum should be installed.

1.2.

CLASS B FIRES (LIQUIDS AND LIQUEFIABLE SOLIDS) Table 1 gives recommended minimum ratings for the selection of extinguishers for class B fires. It should be remembered that different types of extinguisher, of the same rating, have different characteristics which, in particular circumstances, may make one type preferable to another. Mass for mass, powders are probably the most effective medium against class B fires but they are not effective against fires in which part of the fuel surface is shielded from the powder discharge. Re-ignition of the fuel is possible once the powder discharge ceases; it is not possible to partially extinguish the fire. This applies also to carbon dioxide and halons where still installed. Foam is not effective against ' running' fires, but is effective against contained fires where it will provide semi-permanent protection. With foam it is possible to partially extinguish a fire which will not regain full intensity for some time until the foam over the surface is destroyed. Foam can be applied to liquids in tanks to shield them from ignition from another source, or to prevent the evolution of flammable vapours. Special types of foam are required for use against water-miscible liquids. Where both foam and dry powder extinguishers are installed, care should be taken to ensure compatibility of use. TABLE 1 : MAXIMUM AREA OF CLASS B FIRE (DEEP LIQUID)FOR WHICH EXTINGUISHERS ARE SUITABLE Maximum area for three extinguishers (foam extinguishers only )

Maximum area for two extinguisher

Maximum area for one extinguishers

m²

m²

m²

13B

0.26

0.16

0.09

21B

0.42

0.26

0.14

34B

0.68

0.42

0.23

55B

1.10

0.69

0.37

70B

1.40

0.88

0.47

89B

1.78

1.11

0.59

113B

2.26

1.41

0.75

144B

2.88

1.80

0.96

183B

3.66

2.29

1.22

233B

4.66

2.91

1.55

296B

5.92

3.70

1.97

377B

7.54

4.71

2.51

479B

9.58

6.00

3.19

610B

12.20

7.62

4.07

Extinguisher rating

1.2.1

Grouping of Class B Fire Risks To determine the minimum recommended provision of suitable extinguishers it is convenient to assess premises in the following manner: •

Each room or enclosure should be considered separately.

•

Fire risks more than 20 m apart should be considered separately.

•

Fire risks sited within 20 m of another fire risk should be assessed either as undivided groups or as divided groups. Note: Extinguishers should be sited as close as possible to the anticipated point of occurrence. It is undesirable to cover dispersed risks with the same extinguisher(s), with consequent excessive travel distances to reach the fire with an extinguisher. The distance apart of 0 m has been selected as reasonable in view of the danger of rapid spread inherent in class B fires.

1.2.2

Contained Fires Single open topped containers: The minimum class B rating of an extinguisher or extinguishers recommended for a single open-topped container of flammable liquid (e.g. mixing vessel, spillage in bunded area) can be read directly, from Table 1. The surface area of the container is used to determine the rating. Undivided group of containers: Containers less than 2 m apart should be considered as an undivided group, equivalent to a single container. The total surface area of all containers in the group is used to determine the recommended rating. The minimum class B rating recommended can be read from Table 1 using this value. Divided group of containers: Containers more than 2 m, but less than 20 m apart, should be considered as forming a divided group. The surface area of the largest container (or aggregate surface area of the largest undivided group) or one-third of the aggregate surface area of all the containers in the group, whichever is the greater, is used to determine the recommended rating. The minimum class B rating recommended can be read from Table 1 using this value. Spillage: The recommended minimum rating of extinguisher to cover spillage of flammable liquid is calculated from the anticipated volume of spillage as follows: Recommended minimum rating = 10 x volume (in litres) of spillage The volume of spillage should be assessed according to the particular circumstances. In the case of non-spillproof movable containers it should be assumed that the whole contents of the largest moveable container may spill. Large volume spillage into restricted areas such as bunds, silled rooms and gullies should not be assessed by the formula given in this clause, but should be regarded as a container fire of area equal to that of the restricted area.

1.2.3

Additional Provision of Extinguishers It should be borne in mind that the recommendations given in Table 1 are minima and are intended to cover the more common flammable liquids. Where liquids have a low flash point or are especially difficult to extinguish, such as diethyl ether and carbon disulphide, higher rated extinguishers should be provided. In areas protected by fixed systems, portable extinguishers should be provided to cover the risk of spillage or fires originating outside the range of the fixed equipment. Similarly, where high rated extinguishers are installed it is advisable to provide additional low rated extinguishers for use on small fires in preference to the higher rated extinguishers to reduce contamination, replacement costs, etc. and should be sited close to anticipated point of occurrence. These additional extinguishers should be selected according to the recommendations given in Table 1.

1.2.4

Examples: Minimum Provision for Class B Fires (Single Containers)

1.2.4.1 A single tank of surface area 1.0 m² is situated in a room. The recommended minimum rating is found from Table 1 as follows: •

If only one extinguisher is to be installed, 183B (from columns 4 and 1).

•

If two extinguishers are to be installed, 89B each (from columns 3 and 1).

•

If three extinguishers (foam only) are to be installed, 55B each (from columns 2 and1).

1.2.4.2 A vessel containing a maximum of 200 litres of flammable liquid is positioned within a bund 1.3 m x 1.9 m of suitable depth The recommended minimum rating is found from Table 1 as follows, using the area of the bund 1.3 x 1.9 = 2.47 m²:

1.3.

•

If only one extinguisher is to be installed, 377B (from columns 4 and 1).

•

If two extinguishers are to be installed, 233B each (from columns 3 and 1).

•

If three extinguishers (foam only) are to be installed, 144B each (from columns 2 and 1).

MIXED RATINGS Where both class A and class B materials are present in the same area extinguishers should be provided to meet both recommendations. The installation of a single type of extinguisher(s), with both class A and class B ratings is recommended in preference to two types, one class A the other class B, taking note of the limitations of the various types.

1.4.

RATING OF EXTINGUISHERS MANUFACTURED IN ACCORDANCE WITH OLD BRITISH STANDARDS Such extinguishers which comply with obsolete standards may be regarded as having ratings not higher than those given below. Extinguisher type

Rating (max)

9 litre water extinguisher

13A

9 litre foam extinguisher

34B

1.5 kg halon

21B

2 kg carbon dioxide

21B

4.5 kg carbon dioxide

34B

3 kg powder

55B

9 kg powder

144B

14 kg powder

233B

Sizes not listed may be regarded as having ratings in general accordance with these values.

Appendix 15.01.04 1.

LIMITING OF HALON EMISSIONS Halons are regarded as ozone damaging chemicals and many countries are now imposing restrictions on their use. The following is recommended for all PETRONAS marketing operations. The following approaches should be taken to reduce the emission of Halon 1301 and Halon 1211 into the atmosphere:

1.1.

1.2.

EXISTING SYSTEMS •

Stop all release of Halon during training (e.g. release from portable extinguishers); use an alternative such as CO2.

•

Generally phase out mobile and portable Halon 1211 extinguishers (replacing by 2 water/foam/CO /dry powder as appropriate).

•

Reduce any systems which are oversized (e.g. total room flooding where cabinet flooding would suffice, or enclosures which could be subdivided).

•

Reinforce maintenance procedures to detect leakage from existing systems.

•

Test fixed Halon systems without release of Halon 1301 or 1211 (this may require some modification of existing systems).

•

Immediately put all automatic Halon 1211 and 1301 total flooding systems at normally manned locations on manual release, to avoid spurious trips and to give the possibility of manual intervention using less (or alternative) extinguishing media. Detection systems, e.g. heat or smoke detectors, should be realistically tested for rapid response to the specific types of fire which may be expected, to minimise the additional damage which could result from this slower approach.

•

Generally remove the Halon 1211 bottles from floating roof tank systems, but ensure adequate detection and alarm. Install fixed or semi-fixed dry riser foam systems on all floating roof tanks which do not already have them (for continuous fire attack). Floating roof tanks in areas where there is a high risk of lightning strikes may require special consideration.

•

Generally phase out fixed Halon systems at times of major overhaul. For exceptional circumstances, where Halon is still considered to be essential, total flooding systems should be on manual release only, operated as a last defence, and should be refilled with safe disposal of the Halon, as soon as suitable alternatives become available.

NEW PROJECTS •

Do not install Halon 1211 mobile and portable extinguishers.

•

Do not install fixed Halon systems (possible alternative for unmanned rooms containing major electric/electronic equipment is to use water sprinklers in the room and ceiling void, and CO2 in underfloor areas, after electrical isolation). Protection of unmanned rooms should be based upon manual intervention, with automatic detection and alarm, as appropriate. For further information or advice please contact PETRONAS.

Appendix 15.01.05 1.

FIXED COOLING FOR VERTICAL TANKS

1.1

APPLICATION RATE For newly constructed tanks which require fixed cooling a minimum water application rate of 1.71/min/m² for the roof and 171/m length of shell circumference should be used (refer Section 15.02.01). For existing tanks, upgrading of fixed cooling facilities should also be considered. This will be dependent upon:

1.2.

•

Actual tank spacings and general layout.

•

Speed and reliability of back-up fire fighting support.

•

Strategic importance of the storage facility/possibility of arranging suitable exchange product liftings.

TANK SEGMENT COOLING Selective cooling of segments of the total circumference of large tanks may be achieved by installing two (or more) separate spray ring headers at the top of the tank Shell. Separate water delivery lines and valves will also be required. This arrangement will help to limit the required capacity of fire pumps and hydrant lines, and will also reduce the possibility of overloading of bund drainage facilities in the event of a major fire.

2.

SPRAY RINGS Tank cooling should be achieved using stainless steel spray nozzles located on one or more tank top headers as well as on the tank shell. The minimum spray orifice size should be 6 mm to avoid blockage. At this diameter, and at an application rate of 17 litre/m circumference, pressures of around 2.5 to 3.0 bar ex-hydrant will be required. Therefore a pressure reducing device (possibly a length of pipe of restricted diameter) will be needed. Hot dip galvanized mild steel pipe is recommended for the spray system and all connections should be flanged, which avoids the potential for rusting if screwed connections are used. A bucket type filter should be installed at each supply manifold with a stainless steel filter element with openings of 3 to 4 mm. Each tank should have a spray ring header installed at the top of the tank shell with nozzles located up to 450 mm out from the shell plates. Additionally one or more ring headers are to be installed on the roof, as follows: Tank diameter (m)

Number of roof headers

Up to 17.5

1

17.5 to 36

2

36 to 52

3

Numbers of spray nozzles on headers will depend on their flow rates and spray pattern characteristics. Including run-down of water from roof headers, all parts of the tank surface should receive 1.7 litres/min/m². Tanks located 40 m or more from other tankage, pumphouses, loading facilities, etc. do not require fixed cooling arrangements.

2.1.

TESTING OF WATER SPRAY SYSTEMS A major problem associated with water spray systems is blockage of spray jets. Some of the main causes of these blockages are known to be debris left inside the pipes during installation and repairs, gravel and debris carried by the water and corrosion products which originate in the feed lines. The pipes used in water spray systems are hot-dip galvanised and, to preserve their corrosion resistance properties, should only be connected by flanges. This requirement is, however, often neglected. Pipes are cut and welded and, as a result, complete layers of zinc/zinc oxide become detached from the inner walls and form blockages in the system. See Figure 15.01.31 for Typical Dry Riser showing surface and flushing test connections. The main cause of spray systems failure is, however, the gradual build-up of silt which, in time, hardens and then breaks into lumps large enough to block the nozzle. Frequent flushing of the lines helps to keep them clear but even well maintained systems can suffer blockages if the design of the system allows sediments to accumulate at critical points. The sediments usually enter the system through small, undetected leaks but the ingress of silt and small size gravel during water tests is thought to aggravate the situation. Blockages are often found where there are reductions in pipe diameter and in systems which utilise small bore (4 to 5 mm diameter nozzles). It is recommended that the dry riser and spray system should be smoke tested every year and fully water tested every three years. The smoke being hydrocarbon generated has a corrosion inhibiting effect in the dry riser and spray rings. Operation staff are not keen to test water spray systems with water for a number of reasons. In the first place, flooding an installation or depot with water grossly interferes with its normal functions. Even then it is considered a nuisance since all other work must be stopped and all delicate equipment must be protected. Full flow tests require large volumes of water which, in some installations or depots it means the introduction of back- up sea or brackish water into the service-water facility which therefore necessitates fresh water flushing. This can accelerate corrosion and wear in the system which, in the long term, increases the probability of blockages by corrosion products. Poorly drained sections will fill with water during a test and the standing water may subsequently freeze and block a complete section of the system. This problem may not exist in a well designed system but 'dead legs' can be introduced at any time when an installation undergoes repairs or modifications. In some installations or depots the service water is dirty and will deposit silt and debris in low flow sections of the network. When the demand grows, as when spray systems are water tested, these may be carried by the increased flow and cause blockages. It is claimed that the water coming out of the nozzles leaves dirty stains on painted tank walls, others admit that the whole operation is alien to the normal functions of the plant and, consequently, not very popular. The idea of being able to dry-test water spray systems appeals to those responsible for their maintenance. Dry tests can indeed be very useful especially where water tests are genuinely impossible or difficult to conduct. However, in most cases they can only be considered as a tool which may complement wet tests, not replace them. The latest development in testing spray systems by using smoke generating equipment produced by 'Acettain Ltd' of London, and is termed the 'PRO-MIST' package. Briefly the package comprises a smoke generator together with an electric motor driven for using mains current and when coupled to a connection in the spray piping can direct smoke over a distance of 150 metres to enable testing and detecting blocked jets in the system. The time taken from start up of the equipment until smoke reaches the jets is about 30 minutes. The overall dimensions of the equipment is 850 x 50 x 350 mm, weighing 40 kilos. It is not intrinsically safe and must be used accordingly. It is recommended only suitably trained and supervised personnel should use this apparatus. Further details are obtainable from PETRONAS.

FIGURE 15.01.06 CHUBB MOBILE CPC DRY CHEMICAL POWDER EXTINGUISHER

MODELS: CPC Features • • • • • • •

Fast knockdown, efficient discharge Highly manoeuvrable well balanced unit Suitable for use in locations with difficult access. Designed for one man operation Suitable for a variety of fire-fighting powders Neat easy-to-operate applicator D.O.T. Approved

General Description This mobile fire extinguisher is suitable for use with a range of Chubb fire-fighting powders and has been specifically designed for simple one man operation. Of large capacity and high discharge rate, it is ideally suitable for quick action against extensive areas of oil or spirit fires. Additionally, the CPC mobile extinguisher provides a wide degree of flexibility when fighting fires in locations with difficult access and fires of differing types.

The powders recommended for use with this unit are Chubb Fire FC Standard Dry, GPX and Monnex (see separate Data Sheets). These powders are capable of dealing with Class B flammable liquid fires or fires involving flammable gases such as methane, LPG etc. (Class C fires). GPX can also deal with Class A fires involving carbonaceous materials such as wood and paper. All powders listed can be applied to electrical fires.

FIGURE 15.01.07 CHUBB FL22 MOBILE FOAM LIQUID PROPORTIONER UNIT CHUBB MOBILE FOAM UNITS Total flow Operating pressure Range Foam Concentrate

Foam Concentrate Capacity Discharge time 6% Discharge time 3% Coupling Finish Weight Empty Full

Capacity: Water supply required: Operating pressure: Operating time:

Hosemaster

Hosemajor

451/min at 7 bar (10 gpm at 100 psi) 3 to 10 bar (45 to 150 psi) All fire fighting concentrates

451/min at 3 bar (10 gpm at 43 psi) 2.0 to 3.4 bar (30 to 52 psi) Hazmat 1 & 2 Masterfoam (A) Hex (S)

11 litres 4 minutes 8 minutes 3/4"BSPF Cream

11 litres 4 minutes 8 minutes 3/4"BSPF Dark Blue

5.6 kg 17.5 kg

5.6 kg 17.5 kg

100 litres (22 UK gal) foam compound (3% or 6%) 225 litres/min 3-10 bars 3% compound - 14 minutes 6% compound - 7 minutes

FIGURE 15.01.08 FLOW RATES FROM FIRE HOSE NOZZLES

FIGURE 15.01.09 PRESSURE LOSS IN FIRE HOSES

FIGURE 15.01.10 HYDRANT-FED FIRE-FIGHTING EQUIPMENT

FIGURE 15.01.11 TYPICAL FOAM-GENERATING FIRE FIGHTING EQUIPMENT

FIGURE 15.01.12 TYPICAL FOAM CONCENTRATE INDUCTION

FIGURE 15.01.13 INSTANTANEOUS HOSE COUPLINGS AND ACCESSORIES

FIGURE 15.01.14 TYPICAL MECHANICAL FOAM GENERATORS

FIGURE 15.01.15 CHUBB ‘JET-MASTER’ PORTABLE MECHANICAL FOAM/WATER MONITOR

Foam improver/nozzle section in which foam of correct consistency is formed and expelled as high-velocity rope jet. For water spray only, this section is removed

Total weight 34 kg (74.5 lb)

Foam generator section which combines water, foam liquid and air

Main body comprises two sections joined by quick action thread

Two legs, independently adjusted and lockable, support monitor at elevations between 40° to 70° Easily observed pressure gauge, recessed for protection

Carrying handle

Connection for aluminium foam compound pick-up tube/hose assembly or for 1½-inch hose from wheeled foam liquid tank Swept-elbow connector fitted with two 2½-inch instantaneous male couplings. (Other couplings can be fitted) Swivelling base plate allows alteration of elevation while the unit is operating

WATER FLOW : 1600 litres/min at 10.5 bars FOAM COMPOUND 3% or 6% by calibration

JET LENGTH JET HEIGHT - FOAM

: 40m at 10.5 bars : : 12m at 6.7 bars 23m at 10.5 bars - WATER : 30m

FIGURE 15.01.16 CHUBB RANGE OF HIGH BACK PRESSURE FOAM MAKERS

FIGURE 15.01.17 CHUBB ‘JET-MASTER’ MECHANICAL FOAM MONITOR WITH ADAPTOR FOR BASE INJECTION

FOAM SOLUTION FLOW RATE : 1600 litres/min (350 UK gal/min) FOAM OUTPUT: 6300 litres/min (1400 UK gal/min) DESIGN OPERATING PRESSURE: 10 bars Maximum Design Back Pressure – 25% of Inlet Pressure

FIGURE 15.01.18 ANGUS VARIABLE FOAM INDUCTOR

FIGURE 15.01.19 DISTRIBUTION OF FOAM AND CIRCULATION OF TANK CONTENTS IN FOAM BASE INJECTION SYSTEMS

FIGURE 15.01.20 SEMI-SUBSURFACE FOAM SYSTEM FOR FLAMMABLE AND COMBUSTIBLE LIQUIDS

FIGURE 15.01.21 SEMI-FIXED BASE INJECTION SYSTEM

FIGURE 15.01.22 FIXED BASE INJECTION SYSTEM Proportioners and generators near pump discharge located together multiple tanks short distance to foam station

FIGURE 15.01.23 FIXED BASE INJECTION Proportioners and generators near pump discharge

FIGURE 15.01.24 FIXED BASE INJECTION SYSTEM Generators separated for proportioner – multiple tank separate foam lines to each tank

FIGURE 15.01.25 ANGUS FIRE ARMOUR HIGH-BACK-PRESSURE FOAM GENERATOR (SERIES 2)

FIGURE 15.01.26 TANK INLET FOR BASE INJECTION OF FOAM

FIGURE 15.01.27 SINGLE FOAM POURER FOR FLOATING ROOF

FIGURE 15.01.28 FOAM POURERS FOR FLOATING ROOF TANKS

FIGURE 15.01.29 FOAM POURER COVERAGE

FIGURE 15.01.30 2

N UNIT FOR ‘POLY-FLO’ LINE DETECTION (Manufacturer – Saval Kronen0burg B.V. Prinsenbeck – Holland)

FIGURE 15.01.31 TYPICAL DRY RISER SHOWINGS SMOKE AND FLUSHING TEST CONNECTIONS

Appendix 15.02.01 SUB-SURFACE FOAM INJECTION - DESIGN AND EQUIPMENT - PROTECTION 1)

GENERAL DESCRIPTION The required capacity of a base injection system for fixed roof tanks is based on the minimum foam solution (water plus foam compound but not aspirated) flow rate required to extinguish a storage tank fire. The recommended minimum rates, based on BS 5306 - Section 6.1 are as follows: •

Class I and II products: -

4.0 litres/minute/m² of product surface to be protected. Sufficient foam compound and water should be available to permit continuous operation at this application rate for a period of 45 minutes.

•

Class III products (not normally required): Notwithstanding the above, gas oil tanks located adjacent to Class I storage, should be treated as Class I tankage to facilitate possible product changes in the future. -

Black oils - base injection not suitable.

The design of a sub-surface systems involves a sequence of steps as follows: (i)

(ii)

(iii)

(iv)

Calculating the minimum acceptable foam solution flow rate. When more than one tank is to be protected by the same system, the design flow rate is determined by the tank requiring the highest flow rate. Selecting the number, size and distribution of foam generators plus the general layout of water, foam solution and finished foam pipelines. Depending on the tank farm layout as well as the location and orientation of water supply, the combination and grouping of generators (and their related inductors) may vary from: (a) A single battery of generators to supply all needs via a foam distribution manifold. (b) A number of separate batteries of generators strategically located to serve different groups of tanks. The decision between semi-fixed and fixed systems will also have to be made at this point in the calculation. Selecting the number of foam inlets for each storage tank, which is governed by the diameter of the tank in accordance with the table given in Section 15.01.03 (c iii). An alternative arrangement using a single tank inlet and multiple foam outlet points is shown in Figure 15.01.28. Estimating the foam inlet diameters. Foam inlets must be sized so that the velocity of foam entering the tank is not greater than 3.0 m/second for volatile products (flash-point less than 21 °C) or 6.0 m/second for non-volatile products (flash-point equal to or greater than 21 °C). The correct attitude of the inlets is horizontal (not upwards or downwards); a 45° chamfer is acceptable, see Figure15.01.26. Foam velocities may be greater in the pipelines further upstream of the tank inlet (which permits the use of smaller pipelines) but pipelines must be increased to the correct inlet diameter at a distance of not less than 20 times the pipe diameter from the inlet to the tank. At no point should the foam velocity exceed 9.0 m/second in this section of pipeline. Further upstream the velocity is not critical but should not be too low so as to avoid drainage of water. The inlet diameters estimated at this stage will have to be checked at a later stage in the design depending on the ultimate hydraulics of the system.

(v)

Calculating systems pressure losses so as to derive the finished foam pipeline diameters downstream of the foam generators. This part of the design is governed by a number of parameters: - The design of foam generators is normally such that the maximum back pressure downstream of the generator outlets (caused by pipeline losses, elevation differences and static head of product in the tank) must not exceed 40 per cent of the inlet pressure to the foam generators (old type generators 25 per cent). This is the starting point of the hydraulics design and in situations with high tanks (i.e. high static head of product) and high foam flow rate requirements, can result in substantial pressure requirements. For this reason since pipeline pressure losses for water or foam solution are much lower than for finished foam, a guiding principle is to minimise the length of finished (aspirated) foam lines by positioning the foam generators as far downstream as practically possible so as to limit the distance finished foam has to be pumped before it enters the storage tank. - Foam generator inlet pressure requirements vary from 7 to 10 bar depending on make. Higher pressures can be used to give higher throughputs and/or to meet high downstream back pressures. - To allow full development of finished foam properties a foam line length of preferably 20 m is required before entering the tank, but 5 m is an absolute minimum without significant foam deterioration. (vi) Estimating the inlet pressures to the foam generators (i.e. three to four times the outlet back pressures derived from (v) above), thence calculating the foam solution pipeline sized between the pump discharge and the generator inlets (including all pressure losses sustained through the foam compound inductors, proportioners or other units). (vii) Estimating the volume of foam concentrate, water flow rate and water volume needed to provide base injection operation at the recommended application rate for a period of 45 minutes (or 30 minutes for Class III). From the above, the sub-surface injection system for one or more tanks can be calculated in isolation from the requirements for the rest of the fire-fighting system. Section C below describes the points to be considered to produce an overall tank farm firefighting protection system. 2)

DESIGN NOTES (i)

Foam pipelines should, whenever possible, run outside the bund area so as to be less exposed to fire. This may lead to longer lines which will add to pipeline friction losses. Where a foam line has to run inside the bund area flanges should be eliminated or minimised.

(ii)

Testing - once a sub-surface injection system has been installed (or changed or extended) it has to be tested in order to prove the equipment as well as to train personnel in its operation. This is straightforward if the tank is still empty and the injected foam can be removed from the tank. If, however, the tank contains product, a perfectly adequate test can be carried out if a full bore foam outlet/sample point with a back pressure to simulate a full tank is installed in the foam line upstream of the tank valve. The sample points do not have to be close to the storage tanks but may be more conveniently located near the foam generators subject only to the 20 m minimum distance necessary to permit full development of the foam properties. This will minimise consumption of foam compound during tests and fire practices, and will also facilitate flushing out the lines after such tests. A minimum slope of 1/240 with suitable drainage outlets will facilitate flushing and draining foam lines after testing or usage. Subsequently, periodic testing (during fire drills) is recommended plus routine dismantling and inspection (inside and outside) of equipment and quality testing of foam compound.

(iii)

Quick-action valves - all valves at the tank selection manifold should be quick-action (ball) valves. The size of the ball valves can be reduced to limit cost but to no less than 50 per cent of the pipeline cross-sectional area. In such a case however, the additional pressure lost through the valve must be allowed for in the back pressure calculations. The non-return valves should preferably be soft seated (but not spring-loaded). Accepted materials for the soft seat are nitrile rubber, Viton and Buna-N but not Neoprene. In the event that product passes the non-return valve and fills the line from the tank to the generator manifold, the aspirated foam is able to push the product back to the tank without significant deterioration. If soft seated non-return valves are not available, conventional non-return valves can be installed.

(iv)

A special bursting disk with suitable burst pressure should be used between the foam generator outlet and the non-return valve. This is to prevent product flow into the foam making system in case of non-return valve leakage. Conversely it presents water leaking from the foam system into water sensitive products such as aviation fuels.

(v)

As mentioned in 15.01.07(d) sufficient foam compound must be available or immediately accessible before injection operation begins. One way to minimise total stocks or foam compound held at any plant, is to keep part of the total requirement in a small bulk tank suitably located for sub surface injection purposes. The balance can then be stored in easily movable containers ready to be carried to any part of the site when needed. For 3 example, if the sub-surface injection requirement is 2.5 m of compound, and this is 3 estimated to be more than enough for any other possible fire, then 1.5 m could be stored in a small tank or trailer ready for immediate use in the injection system, and the 3 remaining 1 m kept in containers at the most strategic location for any other fire. The emergency fire plan should then be arranged so that should a tank fire occur, sub3 surface injection can start drawing on the 1.5 m supply of compound. Previously 3 detailed personnel would take the foam containers from the 1 m store to the bulk tank ready for decanting as the initial supply is consumed. If a fire occurs elsewhere, the portable containers can be taken to the site of that fire for use with the normal hoses and foam making equipment; if any further stocks of foam compound are needed these can be drawn from the compound tank. To minimise foam concentrate deterioration, the tank should be fitted with an expansion dome on top and the level of maintained within the dome. To protect the tank against internal corrosion the tank should be lined with bitumen or an 'EPIKOTE' resin based paint or non metallic/glass fibre reinforced polyester tank.

(vi)

The principle mentioned in Design Notes (v) above of converting foam solution into aspirated (finished) foam at the latest possible position in the supply line will help limit pressure losses/reduce pipe diameters. Against this saving will have to be offset the possible need for additional generators because rather than a single battery of generators to cover all needs, locating generators further downstream in the system may mean having to install more than one small battery of generators resulting perhaps in a greater total number of generators required. The relative economics of this must, of course, be assessed. Such a situation would probably not occur with a semi-fixed system which depends on a common store of generators which are taken to whichever is the appropriate foam inlet point at the time of the fire.

(vii)

Foam/foam solution distribution systems Depending on the number of tanks to be protected, as well as the size and layout of the site, various designs of distribution system can be employed as shown in Figure 15.01.21 to 15.01.24 inclusive, and described below. 1)

Fixed sub-surface injection system where tanks are only a short distance from fire pump/water supply permitting the foam station (foam compound tank, inductor(s), generator(s), etc.) to be positioned together near the pump discharge. (a)

This layout (see Figure 15.01.23) is appropriate for single tank protection, and shows how the product inlet may be used as one of the foam inlets. As the tank valves (Vo) must be kept open, a second valve (VT) (or bursting disc with gate valve to protect it when sampling foam) acts to contain any product that may pass the non-return valve in the foam lines. Valve (Vp) is to prevent backflow of foam in product line and will normally be closed.

(b)

This layout (see Figure 15.01.24) is for multiple tank protection, where the foam station is only a short distance from the tank farm and pressure losses are low enough to permit foam generation at the foam station close to the pump. As tank valves Vo remain open, valves VT outside the bund must either be quickly accessible (fire screen plus rapid access) or be remotely operable (reliable power) by a protected system.

2)

Fixed sub-surface injection system where for distance and/or pressure drop reasons the foam generators are separated from inductor/proportioner units. (a)

This layout (see top tank Figure 15.01.24) is appropriate for single tank protection. As the tank valve (Vo) is kept open, a bursting disc is all that is required outside the bund. A manual valve would not be suitable because of the time taken for someone to get to it and open it, but a remotelyoperated valve could be used provided that there is a reliable power supply. Foam sampling is best done by connecting a generator at the solution outlets shown. To sample downstream of the generators entails filling the whole pipeline with solution which is both costly and would necessitate a laborious draining and flushing operation afterwards.

3)

(viii)

(b)

This layout (see Figure 15.01.24) is for multiple tank protection with separate lines to each tank. A foam proportioner may be considered here since it will automatically induce the correct rate of foam concentrate depending on which foam control valve (Vo) is opened, and in addition has a much lower pressure drop compared with inductors. As this system permits manual control it is ideal where power supply (for remote valve operation) is unreliable. For foam sampling see the comments given in 2(a) above.

(c)

An alternative layout is to run a single foam solution line from the discharge side of the proportioner to a manifold positioned immediately upstream of the generators. In this case the control valves would have to be remotely operated, which means a reliable and protected power supply is essential. Bursting discs are necessary to contain product as tank valves are kept open. The same comment as in 2(a) above covers foam sampling.

Semi-fixed sub-surface injection system. A typical layout is shown (Figure 15.01.21) in which the foam inductor and generator are brought to the foam inlet point outside the tank bund and connected to the water supply by hoses. Foam sampling can be done in either way (1 or 2 above) depending on pipe lengths, layout, etc.

Equipment - all pipelines, valves and other standard fittings should be in accordance with the specification for normal installation operations given in the Installations and Depots Manual, 06.01.04. In addition, the following items of equipment have been developed especially for sub-surface injection: (a)

High back-pressure generators - these are required to produce foam with suitable properties for sub-surface injection; expansion two to four and a 25 per cent drainage time of 90 to 180 seconds. Models are available from different manufacturers for a range of foam solution flow rates or between about 50 and 2 250 litres/minute (10 and 500 UK gallons/minute) and which operate at inlet pressures ranging from 7 to 10 bar; examples are shown in Figure 15.01.16, 15.01.17 and 15.01.25. One supplier has produced an adaptor, see Figure 15.01.17 for use with the existing foam monitor shown in Figure 15.01.15.

(b)

Foam compound inductors and proportioners - most in-line inductors working on the venturi principle with a minimum induction rate of 3 per cent can be used. One of the models available is illustrated in Figure 15.01.18. The inductor unit suffers one major drawback in that pressure lost through it equals one-third of its inlet pressure. Thus to feed high back-pressure generators which require minimum inlet pressures of 7.0 bar, the inlet pressures to the inductor must be 10.5 bar. These pressure levels may be tolerable for relatively small or simple applications where back-pressures downstream of the generators can be kept to reasonable levels (or for non-subsurface injection applications) but for larger systems at higher pressure levels generally an alternative such as a variable-flow proportioner may be considered as it has a considerably lower pressure drop and inducts foam compound at a rate directly proportional to the water flow rate through it. However, the relative economics must be assessed before the choice is made.

3)

TOTAL TANK FARM PROTECTION Sections A and B have discussed the design of a sub-surface foam injection system for storage tanks in isolation, and have given a number of related design factors that must be taken into account. In order to complete the protection of a tank farm two further aspects must be considered: (i)

Supplementary protection Supplementary protection should be provided either to extinguish small ground fires within the bund or, elsewhere, or to enable extra cooling water to be directed at storage tanks if needed. For this, branch pipes with a water or foam solution flow rate of approximately 450 litres/minute (100 UK gallons/minute) plus supplementary foam compound should be provided as shown in the following table:

(ii)

Diameter of largest

Number of

Minimum operating

tank in m

branch pipes

time in minutes

Up to 10

1

10

10 to 20

1

20

20 to 30

2

20

30 to 39

2

30

Over 39

3

30

Water for cooling tanks and/or LPG vessels (see 15.03.02 or LPG Manual). The overall combination therefore of: •

The requirements for sub-surface foam injection,

•

The supplementary protection needed,

•

The tank cooling by spray rings (or sprinklers),

will result in a total demand for water flow rate and pressure necessary in the event of a storage tank fire. From this the pressure and flow specifications of the fire water pump(s) can be derived. A major practical element in the design of the system is the actual method of sharing, the total water supply between sub-surface foam injection, supplementary protection and tanks cooling. The first requirement is a centrifugal pump whose flow/head curve is reasonably flat particularly on the low head side of the design operating point. This will minimise variation in discharge pressure irrespective of the actual total demand. The following factors must next be considered: (a)

Cooling water for spray rings (or sprinklers) for product storage tanks. For very simple tank farms where the cooling water systems may comprise separate lines running from the pump discharge manifold to each tank, it may be possible to size the lines such that each tank receives close to the correct flow rate of water. However, for most systems operating from a ring main (complete with hydrants and base injection systems) the hydraulics are too complicated for such treatment. The recommended solution in such cases is to fit a simple but appropriate pressure gauge downstream of the cooling water offtake valve to each tank. From initial trials for each tank cooling line, the degree of valve opening that will give the correct cooling water flow rate can be determined. The corresponding pressure reading can then be taken and marked on the face of the gauge so that in future the correct flow rate to each tank can be set simply by adjusting each cooling line valve until the gauge reads the predetermined pressure. During actual usage, the setting of these valves will have to be back-checked and re-adjusted both at the time of initial opening to start the cooling, and subsequently at intervals since fluctuations in water demand will cause some pressure variations during the fire-fighting activity.

(b)

Supplementary protection These requirements are not so critical in terms of exact flow rates. If foam for attacking ground spill fires or additional water for cooling purposes are required, these can be provided by opening the necessary hydrant valve on the water ring main and the pump discharge will automatically adjust. If supplementary protection is not required then the mains capacity will remain available for other purposes.

(c)

Sub-surface injection Depending on which tank is on fire the demand for foam will vary from the maximum (design) flow rate to something less. The actual foam flow will be controlled on site by opening the requisite number of foam generators for the tank concerned. The generators are largely self-governing in that at design pressure they will pass the design flow rate but at higher pressures they will pass more in accordance with normal hydraulic flow criteria, i.e. that velocity is proportional to the square root of the pressure. If, therefore, a small tank is on fire, requiring only a proportion of the total number of foam generators to be opened, this will present to the pump a back pressure somewhat higher than its design. The pump will automatically adjust to these flow conditions which will result in an increased inlet pressure and flow rate through each generator such that the inlet velocity to the tanks may exceed the allowed limit (3 m/second or 6 m/second). If the pump (centrifugal) operating curve is flat enough such that the increase in pressure between the design point and the actual operating point is small enough, then the flow rate increase will also be relatively low and would not be expected to exceed the allowed limits significantly. To illustrate - if, for example, only opening 2 out of 3 available generators causes a pump discharge pressure increase of say 15 per cent above pump design point, this would lead to an increased flow rate, per generator, equal to the square root of 1.15 per cent which equals 1.07 per cent. Thus the flow velocity would be 7 per cent higher and whether this increase causes the tank inlet velocity to exceed the permitted limits can thence be checked during the design phase. In the same way the various downstream flow conditions (caused by opening all relevant combinations of foam generators) must be re-checked against the operating curve of any existing pump or new pump under consideration. Note: Another situation which does not have any adverse effect is when the product level in a tank is particularly low at the time of a fire. In such a case the back pressure downstream of the generator is reduced and it might be thought this would lead to an increase in flow rate and consequent tank inlet velocity problems. This does not occur in practice because the foam generator design is such that the foam throughput is only dependent on upstream flow conditions and is independent of downstream conditions as long as the 25 per cent back pressure maximum is not exceeded.

(d)

Result From the above considerations, it is possible, to design a total tank farm protection system which, given sufficient stocks of foam compound and water, will provide the total demand to meet most foreseeable tank farm fire situations. It must be realised however that the highest foam demand for a tank fire may not coincide with the highest cooling water demand for adjacent tanks. For this reason all combinations of tank foam plus adjacent cooling must be calculated to determine the maximum total demand on which the overall design should be based.

4)

SMTAFF COMPUTER MODEL FOR BASE FOAM INJECTION CALCULATIONS (a)

General SMTAFF runs on IBM compatible PC and comprises the following three calculation modules: -

Tanks base foam injection calculations to determine foam generators and inductors capacity based on specific flow rate, pipeline sizes, etc. 'Worst case' analysis of total water and foam requirements, including tanks cooling. Pipelines, pressure loss calculations for hydrant lines sizing.

A fourth module enables the user to edit or add to the pre-loaded SMTAFF 'standards' data. This consists of pipes data, fittings data, generators and inductors data, design parameters, (foam application rates, foam velocities, foam pipe lengths), tanks cooling specifications and equipment costs.

(b)

Tanks Base Foam Injection Calculations Steps necessary to complete the BFI calculations for each tank are as follows: (i)

Input tank identification, height, diameter, product name and density. Specify piping length and diameter from foam generator to tank, and all fittings. Increase in pipe diameter at foam inlet section is permitted. Specify, from standards data, generators required. Input piping between generators and inductors. Specify piping between inductors and water take-off point.

(c)

(ii)

Request calculation to check pressure losses and foam velocities in the configuration as defined. If the design is technically unacceptable, a list of errors will appear with suggested amendments.

(iii)

Edit initial input and repeat calculations as in (ii) above.

(iv)

Save data and request print-out. This lists all pipes and fittings, pressure losses and cost breakdown of materials.

(v)

If required, again edit initial input and re-run SMTAFF to find a lower cost design based on alternative generator configurations.

Worst Case Analysis Worst case analysis can be run as a separate exercise or it may follow on from tanks BFI calculations. For any group of tanks SMTAFF will compute the worst (i.e. maximum) cases of: -

Water pressure (based on BFI system requirements only). Water flow rate (for BFI and cooling). Water quantity. Foam quantity.

The SMTAFF computation checks resource requirements for every single tank fire and identifies worst case results accordingly. It cannot always be assumed that one tank will give risk to the worst case for all criteria above, since some tanks may need higher pressure at low flow rates, etc. (d)

Pressure Loss Calculations This module is provided to act as a simple aid in designing the fire main used to supply water to the fire fighting facilities. The module is capable of calculating the pressure loss along single pipeline carrying a specified flow of water. By using the module to investigate the likely loss along single branches of the fire main a simple capacity check/sizing exercise can be carried out. Pipeline identification, diameter, length, height difference along the length, fittings and water flow rate are entered, using pre-loaded standards data. Pipe runs which include more than one diameter can be accommodated.

(e)

Availability The SMTAFF package consists of three disks for IBM - PC, AT or XT, plus user manual.