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) PETRONAS and its affiliates.
2) Other parties who are authorised to use PTS subject to appropriate contractual arrangements.
3) 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 Introduction
Section 01.00.00 Master Development Planning Section 02.00.00 Construction Projects
Part 2 Section 03.00.00 Sites and Layouts
Part 3 Section 04.00.00 Building and Civil Engineering Section 05.00.00 Tanks and Pressure Vessels Part 4 Section 06.00.00 Pipelines
Part 5 Section 07.00.00 The Design of Berthing Facilities for Tankers and Small Craft Section 08.00.00 Heating and Insulation
Part 6 Section 09.00.00 Plant and Equipment Part 7 Section 10.00.00 Utilities
Section 11.00.00 Mechanical Handling
Part 8 Section 12.00.00 Maintenance and Workshops Section 13.00.00 General Services
Section 14.00.00 Chemicals Handling Part 9 Section 15.00.00 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 Recommended 'First Aid' Fire Extinguishers Appendix 15.01.02 Recommended Scale of Fire Equipment Appendix 15.01.03 Planning and Provision of Extinguishers Appendix 15.01.04 Limiting of Halon Emissions
Appendix 15.01.05 Fixed Cooling for Vertical Tanks
Figure 15.01.06 Chubb Mobile CPC Dry Chemical Powder Extinguisher Figure 15.01.07 Chubb FL22 Mobile Foam Liquid Proportioner Unit Chubb
Mobile Foam Units
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 Figure 15.01.16 Chubb Model 10A-30A High Back Pressure Foam Makers Figure 15.01.17 Chubb 'Jet-Master' Mechanical Foam Monitor with Adaptor for
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 Sub-surface Injection of Foam Figure 15.01.21 Semi-fixed base injection system Figure 15.01.22 Fixed base injection system Figure 15.01.23 Fixed base injection system Figure 15.01.24 Fixed base injection system
Figure 15.01.25 Angus Fire Armour High-Back- Pressure Foam Generators (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 Cover
Figure 15.01.30 N2 Unit Alarm for 'Poly-flo' Line Detection Figure 15.01.31 Typical Dry Riser showing Connections
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.
Thus these three parameters dictate the supplies (in litres or m3) 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
Tank dia (m) No branch pipes (400 1/m) Discharge 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
(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) Class I, II products Class III products Up to 24 1 1 24 to 36 2 1 36 to 42 3 2 42 to 48 4 2 48 to 54 5 2 Over 54 6 3
(iv) 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:
• Same as for sub-surface systems.
(v) 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 semi-surface 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) 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.
(ii) 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) It is more difficult to extinguish fires by conventional means in large-diameter 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.
(ii) 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.
(iii) 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.
(iv) 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.
(v) 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 sub-surface 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.
(vi) 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.
(vii) 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 sub-surface 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 PC-based 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) 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).
(ii) 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.
(iii) 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. (e) 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.
