DESIGN AND INSTALLATION OF FIXED FOAM FIRE EXTINGUISHING SYSTEM

Foam for fire fighting purposes is essentially an aggregate of gas filled bubbles, formed from an aqueous solution of a suitable foaming agent or concentrate. The gas used is normally air, but in certain applications, inert gases have been used.

Foam is produced by mixing a foam concentrate with water to the appropriate concentration, and aerating and agitating the solution to form the bubble structure. The ratio of the volume of the made foam to that of the solution from which it is made is defined as the expansion. Other important foam properties are also defined. One of these is the critical shear stress, a measure of the stiffness of the foam and hence an inverse measure of its ability to flow readily over a fuel surface and around solid obstructions. Another is its drainage time, a measure of the stability of the foam, which relates both to its stiffness and ability to resist destruction by the radiant heat of the flames.

Foams are arbitrarily subdivided into three ranges of expansion, these ranges corresponding broadly to certain types of usage which are described below.

The three ranges are approximately:

(LX) Low expansion foam—expansion up to 20

(MX) Medium expansion foam—expansion 20 to 200

(HX) High expansion foam—expansion 200 to 1000

Low expansion foams are generally used for the extinction of fires in flammable liquids by the formation of a blanket over the surface of the liquid, thereby reducing the rate of release of flammable vapours to the combustion zone below that which is necessary to maintain burning. The fires may include pool or spill fires, or fires in tanks and similar containers.

Low expansion foams may be applied directly to the surface of the burning liquid (surface application) or may be applied in the case of tank fires, below the surface so that they float to the surface under their own buoyancy (subsurface application). Low expansion foams may also be applied by a semi sub-surface method. For gasoline and light crude oils, AFFF should be used.

Low expansion foams may be used for the suppression of vapour emission from spillages of flammable liquids. They can also be used to protect other risks from radiant heating, providing the foam layer is regularly replenished, and they can have a limited usefulness in the extinction of surface fires in solid combustibles.

Limitations on the use of low expansion foams are as follows:

1. They are not generally suitable for the extinction of running fuel fires, that is, fuel running from a leaking container or from damaged pipework or pipe joints.
2. Since all fire fighting foams are made from aqueous solutions, they may be 1ineffective or dangerous to use on flammable liquids with temperatures much in excess of 100°C, particularly where these fires are in liquids of considerable depth of in-tank fires. Drainage of the water from the foam may result in the formation of steam which can cause frothing or slop-over of the burning liquid unless due precautions are taken to avoid this. Foams may, however, sometimes be used to cool the surface layers of a flammable liquid below the fire point, provided the temperature is not greatly in excess of 100°C.
3. Most aqueous foams are not suitable for use on water-miscible flammable liquids, which can cause rapid breakdown of the foam by extraction of the water from the bubble walls. For these flammable liquids, specially stabilized foam concentrates are used.
4. Foams are not suitable for use on fires involving gases, or liquefiable gases with boiling points below 0°C, or cryogenic liquids.
5. Because foams are made from aqueous solutions they may be dangerous to use on materials which react violently with water, such as metallic sodium or potassium. They can, however, sometimes be used with care on magnesium fires to help restrict burning by cooling the residual metal.
6. Low expansion foam is a good conductor and should not be used on energized electrical equipment.
7. Certain wetting agents and some extinguishing powders may be incompatible with foams, causing a rapid breakdown of the latter. Only agents which are substantially compatible with these foams should be used in conjunction with them, in such cases AFFF should only be used.
8. Only certain types of foam concentrates are suitable for storage in the diluted or pre-mixed condition. AFFF can be kept in premixed condition up to 1 year. Protein base foams are unsuitable for keeping in premixed condition.
9. Simultaneous use of water jets or sprays may adversely affect a foam blanket, and their use should not be envisaged in conjunction with these foams unless it has been shown that this will not occur.

The following types of low expansion foam concentrates:

1. Protein Foam Concentrates (P) These are liquids containing hydrolized protein materials with the addition of certain salts to improve stability and storage properties. Protein foam concentrates are usually manufactured for use in concentration of 3 percent and 6 percent. Foams produced from these concentrates are relatively stable, have low rates of liquid draining, are relatively stiff and have good heat resistance. Protein foams are not suitable for use in sub-surface systems in fuel storage tanks but may be, however, applied by a semi-surface method.
2. Fluoroprotein Foam Concentrates These are made from protein-based concentrates by the addition of fluorinated and other types of surface active agents. An effect of adding these surfactants is to give a foam of lower shear stress whilst retaining satisfactory heat resistance. This results in the foam flowing more quickly than protein foams across the fuel surface and around any obstructions giving faster control and extinction. The improved flow properties and the higher surface activity gives the foam self sealing properties, that is, if the foam blanket is broken the foam will flow readily to reform a complete blanket. A further advantage of fluoroprotein foams over protein foams is that they are far less vulnerable to contamination by hydrocarbon fuels, and are suitable for use in sub-surface systems. These foam concentrates are usually available for use in 6 percent concentrations. Fluoroprotein foams exhibit good sealing against hot metal edges.
3. Aqueous Film Forming Foam Concentrates (AFFF) These foam concentrates, which may also be referred to as fluorochemical foam concentrates, are based on fluorinated surface active materials in combination with other surface active agents and stabilizers. The foams produced are more fluid than fluoroprotein foams, having low critical shear stress values and also short drainage times. They give very quick control and extinction, but the fast drainage means that they do not have high heat resistance and they may have less burnback resistance than protein and fluoroprotein foams. A feature of these foams is that the solution draining out of the foam is capable of forming a floating film on the surface of some liquid fuels. This can give protection against re-ignition and give re-sealing properties should the foam blanket be broken. These concentrates are usually available for use in 6 percent concentrations. They may be used for sub-surface systems.

LOW EXPANSION FOAM SYSTEMS FOR SURFACE APPLICATION

Systems producing foams with expansions up to 20, in which the foam is applied directly to the surface of the burning fuel by means of fixed nozzles, sprayers, pourers or monitors. The usual expansion range for such systems is between 6 and 12.

Rate of Application of Foam Solution

Requirement

The system should provide a minimum application rate of foam solution per unit area, when tested in accordance with the method of test given .

Method of Test

Apparatus

Install a pressure gauge adjacent to the discharge point in the hydraulically most remote location, with respect to the main foam solution supply line to the system. It is essential that the K factor of each nozzle is known

Procedure

Discharge the system and record the steady state discharge pressure (P) at each of the nozzles. Visually examine all discharge points to see that they are operating satisfactorily.

NOTE—Water may be used instead of foam solution to avoid the need for extensive cleaning of the system after test.

The discharge point may be a nozzle, sprayer, pourer or monitor, but for simplicity will be referred to here as a ‘nozzle’.

Calculation

Q = K/P

where

Divide Q by the area a (in square metres) designed to be covered by that nozzle, that is, Q/a. Compare the value of Q/a with the minimum acceptable value.

Foam Distribution

A full-scale foam discharge test should be conducted to ensure that the system is capable, in accordance with the design requirements, of producing and maintaining an even foam blanket over the surfaces to be protected.

Particular attention should be paid to the possible effects of wind, and of obstructions such as pipework, pumps, motors, vessels, etc, so as to ensure that there are no areas of reduced foam coverage where fuel can burn unhindered.

LOW EXPANSION FOAM SYSTEMS FOR SUB-SURFACE APPLICATION

General

The system should provide a minimum application rate of foam solution per unit area, when tested in accordance with the method application rate.

Method of Test

Apparatus

The foam supply and test lines and their associated valve arrangements and if the system has

more than one injection point per generator then the foam should be sampled on the line leading to the most remote point. It is essential that the foam generator discharged should be known.

Calculation

Using the formula Q = K/P

where Q is the foam solution flow rate—l/min

and P is steady state inlet pressure-bar

Divide Q by the area (in square metres) protected by the injection point under test.

Foam Distribution

A check should be made to ensure that the foam injection points are hydraulically balanced.

BASIC TYPES OF FOAM SYSTEM

General

A foam system consists of an adequate water supply that can be pressurized, a supply of foam liquid concentrate, a device to proportion correctly the water and foam concentrate and pipework or hose connected to equipment designed to produce and to distribute foam over the risk.

Self-contained systems are those in which all components including water and foam concentrate are contained within the system. Such system often have water and foam concentrate stored as a premix solution in a tank which is pressurized by compressed gas when operated or

 

the foam concentrate can be stored and pressurized separately.

There are three basic types of systems and each may be used inside or outside buildings:

1. Installed, fixed or semi-fixed;
2. Portable; and
3. Mobile.

Installed Systems

Fixed:

This type has permanent steel pipework connected from the water supply via the fire water pump (if fitted) and foam liquid proportioning device to the foam maker(s) which protect the hazard.

Semi-Fixed :

Permanent steel pipework is employed from an area adjacent to the risk, from which it is considered safe for personnel to conduct fire fighting operations, to the foam maker(s) which protect the hazard. This pipework may include the proportioning device, and has provisions for water supply hoses to be connected. The water supply is usually pumped and foam concentrates provided by mobile fire appliances.

Portable:

This includes foam-producing units that can be carried by one or more men and connected via fire hose to a pressurized water or premixed solution, supply, so as to produce foam jets, or sprays that can be applied to the risk.

Mobile:

This includes foam-producing units mounted on wheels, and which may be self-propelled, towed by a vehicle or pushed by hand. These units may be connected to a suitable water supply or may utilize a premixed foam solutions. They can produce foam jets or sprays to cover the risk.

FOAM SYSTEM DESIGN

General

The system should be designed to suit the particular hazard and the following points should be considered:

1. Full details of the flammable liquid, its storage, handling and location need to be known before any foam system is considered.
2. The most suitable foam-making concentrate (P, FP, AFFF) in the appropriate concentration.
3. The most suitable solution application rate.
4. Most suitable equipment for making and delivering foam.

NOTE—The selection may depend upon the available water pressure.

1. System operating time.
2. Quantity of foam concentrate required for extinction.
3. Most suitable proportioning method(s).
4. Pipework sizes and pressure losses.
5. Water supply requirements, quantity, quality and pressure so that suitable pumps may be selected.
6. System operation and any fire or gas detection equipment.
7. Any special considerations such as the use of electrical equipment in areas where flammable vapours may be present.
8. Reserve foam concentrate supply.
9. Drainage and bunds.

Automatic Operation

In conditions where the onset of a fire may lead to a rapid escalation, the use of fixed foam systems designed for automatic operation should be considered.

This will apply particularly to a risk situated in a building where any heat generated by fire cannot disperse as readily as in a similar outdoor risk. It is therefore desirable that indoor fixed foam systems be designed for automatic operation, supplemented by auxiliary manual operation.

WATER SUPPLIES, PUMPS AND DRAINAGE OF FOAM SYSTEM

Water OF FOAM SYSTEM

The quantity and flow rate of the water supply should be adequate to provide not only for the foam system but also for any other fire-protective systems which may be used simultaneously with it, for the specified discharge times, the details of which are given in IS 9668: 1980.

The water supply to foam systems may be hard or soft, fresh or salt, provided this has no adverse effects on foam formation or foam stability. Particularly care should be taken to ensure adequate foam quality where the water supply has been treated or otherwise contaminated.

Where solids of sufficient size to obstruct openings in the foam equipment may be present, strainers should be provided.

The recommended water temperature for foam production is between 5°C and 38°C. Outside this temperature range foam performance may be impaired. Precautions should be taken to prevent freezing taking into account the combined effect of low temperature and high wind.

Water Pumps OF FOAM SYSTEM

Pumps providing a water supply to foam equipment need to be correctly sized and should be capable of operating satisfactorily following long periods of inactivity. These should conform to relevant Standard. There should not be any sluice or shut-off valve in the suction line. The pumps with valve arrangement should be tested at least once per month.

The pressure supplied by the pump to the inlet of the foam system under required flow conditions should lie within the range for which the system has been designed.

For a single pump installation, a suitable alternative water supply should be available. In general, multiple pump arrangements are preferred to improve reliability. Emergency connection should be provided for connection of fire hoses from trailer pump, etc.

Diesel engines are preferred to electric motors for driving pumps, unless stand by electric power can be relied upon to be available in emergency.

The use of one diesel-driven and one electrically-driven pump of appropriate size is an acceptable arrangement. Operation of the foam equipment, whether by automatic or manual means should cause the automatic operation of the pump or pumps. In addition, arrangements for starting the pumps manually should be provided.

When pumps are electrically-driven, it is essential that the electrical supply be maintained to the pumping set. It is therefore necessary to ensure that an alternative power supply is always available for the motor.

Switches on the power feed to the motor should be clearly labelled in white letters on a red background for following, according to:

1. Fire equipment,
2. Pumps motor supply, and
3. Not to be switched off during fire emergency.

The lettering should be in upper and lower case with a minimum lower case letter height of 15 mm.

The electricity supply circuit should have an adequate short circuit protection.

Drainage of Bunds OF FOAM SYSTEM

Drains and interceptors of bunded areas should be of adequate capacity to carry the anticipated drainage of water used in firefighting. The bund for an oil tank should be with a slope to the rain outlet not too close to the group of product pipes.

FOAM CONCENTRATE SUPPLIED, PUMPS AND PROPORTIONING SYSTEMS

Storage

Storage of foam concentrate or premix solution should be in an accessible location not exposed to the hazard they protect. The material of construction of any housing should comply with the requirements of relevant Standard.

The tanks or containers should be made from materials suitable to store the concentrate for long periods without risk of corrosion to the tanks or abnormal deterioration of the media—like glass fibre reinforced polyester.

Means should be provided to ensure that the concentrate or premix solution is kept within its design operating temperature range. The storage temperature range should be as per relevant Standard.

Clear markings should be provided on storage vessels to identify the type of concentrate and its concentration in solution. Many materials are not suitable for continuous immersion in foam concentrates because either the material or the concentrate may be adversely affected. The protein foam should be tested after its shelf life.

Storage tanks should have capacities to accommodate the required quantities of foam concentrate or premix solution with adequate ullage for thermal expansion. For tanks at atmospheric pressure this may be achieved by means of a closed vertical riser or expansion dome. Where storage tanks require to be vented to atmosphere, the air/liquid interface should be of the minimum practical area in order to minimize the possibility of interior tank corrosion and sludge formation. A pressure vacuum vent valve may also be provided. Foam concentrate outlets from tanks should be raised above the bottoms of the tanks to provide adequate sediment pockets. The capacities of tank sediment pockets should be excluded in determining the effective capacity of the tank.

Pipework systems should be designed to be either charged or dry, to minimize situations when there may be an air/liquid interface in a line or valve.

Tanks should be equipped with access for inspection and cleaning of interior tank surfaces, outlet connections and testing lines; protected sight gauges or other contents measuring devices and filling, draining and sampling connections. Pressure tanks should have a means of filling, a means to measure the contents available, a drain valve and access for internal inspection and cleaning.

Reserve Supply for FOAM SYSTEM

It is essential that a reserve supply of the correct foam concentrate should be available to enable the system to be put back into service

within 24 hours of operation. This supply may be stored in separate tanks, in drums or cans on the premises, or be available from an outside source.

Adequate loading and transportation facilities should be assured at all times.

Other equipment which may be necessary to re-commission the system, such as bottles of nitrogen or carbon dioxide for premix systems, should also be readily available.

Foam Concentrate Pumps OF FOAM SYSTEM

Pumps used for foam concentrates should be as reliable as fire pumps. They should be centrifugal type self-priming, and driven by any suitable prime mover conforming to relevant Standard.

Materials of construction should be suitable for use with the type and grade of foam concentrate without risk of corrosion, foaming or sticking. Special attention should be paid to the type of steel used. Stainless steel pumps are preferred.

Pumps should have adequate capacities to meet the maximum system requirements. To ensure positive injection, the discharge pressure rating at design discharge capacity should be sufficiently in excess of the maximum water pressure likely under any condition at the point of injection of the concentrate.

Pumps should be provided with adequate means of pressure and flow relief from the discharge to the suction side of the circuit to prevent excessive pressure and temperature.

Pumps which are arranged to stand dry should have means provided for flushing with clean water after use. They should be provided with a drain down cock.

PIPEWORK DESIGN OF FOAM SYSTEM

Pipes, Connections and Valves

Wherever possible, valves and connections in the pipework to the risk should be located outside the hazard area.

Outside the Hazard Area

Pipes, connections and valves should be suitable for normal water use to the appropriate pressure specification.

Inside the Hazard Area

Pipe should be of steel or other alloy suitable for the pressure and temperature involved. Connections should be welded, flanged for screwed with a taper thread. Where gaskets are required they should be fabricated from a material which is non-combustible when tested in accordance with relevant Standard.

Foam concentrates have a lower surface tension than water, and they may cause internal pipe scale or sediment to loosen, with the risk of blockage of sprayers, proportioning equipment, etc. Pipes and fittings should be carefully cleaned before assembly, and any loose jointing material should be removed.

Pipe Size, Run and Supports of foam system

The pipework for each system should be hydraulically calculated and sized in order to ensure that pressure losses are kept within design limits and that a reasonably uniform distribution is obtained. In this way, the cost will be kept to a minimum while ensuring that each foam generator works most efficiently.

In locations where pipework may be exposed to fire or explosion, it should be coated to afford the best protection against damage. This can be accomplished by running it close to major structural members. In such locations, special consideration should be given to the spacing and type of pipe supports used. Use of cover pipe and where required pipework may be encased in suitable resisting material.

Drainage of foam system

All dry piping should be arranged to drain and should have a minimum pitch towards the drain of 1 in 120.

Drain valves should be provided for premix or finished foam lines at low points in piping, whether below or above ground.

Corrosion Protection of foam system

Internal Protection

Pipework should be of a type, or have a protective lining, which is compatible with the concentrate or premix being used.

Dry foam system pipework may be galvanized providing that it is well washed thoroughly after use. Alternatively, it may be protected internally by a suitable coating.

Wet foam pipework should not be galvanized as this may adversely affect the foam concentrate or premix solution. Corrosion resistant material such as certain plastics or stainless steel may be used, or the pipework may be protected with a suitable coating. Unlined steel or cast-iron pipework may not be suitable for wet use unless flushed periodically.

External Protection

System pipework should be of a type which is resistant to corrosion, such as certain

plastics or stainless steels, or should be protected externally by red oxide primer, undercoat and two top coats of paint suitable for exterior use in the prevailing atmosphere of the risk.

The use of dissimilar metals should be avoided, and an inert insulating means should be used to limit electrolytic action.

Colour Coding of Pipework

The pipes should be colour coded in accordance with relevant Standard.

Flushing Of Foam System

Provision should be made in the design to permit the flushing with clean water after the use of any lines which are normally empty but which have contained foam concentrate, premix solution or made foam.

Water supply mains, both underground and above ground, should be flushed thoroughly at the maximum practicable rate of flow, before connection is made to system piping, in order to remove foreign materials which may have entered during installation.

The minimum rate of flow for flushing should be not less than the water demand rate of the system, as determined by the system design and the available water supply. The flow should be continued for a sufficient time to ensure thorough cleaning. Flushing water should be disposed of outside the system. All foam system piping should be flushed after installation, using its normal water supply with foam-forming materials shut off, unless the hazard cannot be subjected to water flow. Where flushing cannot be accomplished, pipe interiors should be carefully examined for cleanliness during installation.

Pipework scale traps should be provided in the line upstream of foam making equipment. Strainers should be inspected and cleaned after each use.

Tanks and pipes which are normally filled with liquid should be protected against freezing where appropriate.

OPERATION OF FOAM SYSTEM:

Method

Foam system should be operated manually or automatically, dependent upon the type and location of the risk. In general, the choice will be governed by the likely rate of fire development, the potential spread to other risks, and the likely life hazard.

Operating Instructions and Training

The operating instructions for any system, whether manual or automatic, should be located at the control equipment itself, and also at the plant of fire control centre. All persons who are authorized to operate the system should be thoroughly trained in its function and method of operation at least once in a month.

Manually-Operated Systems

Controls for these systems should be located in an accessible place sufficiently removed from the hazard zone to permit them to be safely operated in emergency, yet close enough to ensure that the operator knows the fire-ground conditions. The location and purposes of the controls should be plainly indicated, and should be related to the operating instructions.

All operating devices whether manual or automatic should be suitable for the service conditions they will encounter. They should not be readily rendered inoperative, nor be susceptible to inadvertent operation by environmental factors such as high or low temperature, atmospheric pollution, humidity, or marine environments.

Automatically-Operated Systems of foam system

Automatic systems should be operated by a detection system which shall give a local alarm as well as an alarm at the plant or fire control centre.

They should incorporate a manual operating device capable of overriding the automatic control (but not the alarm signal) if required. The manual override should be relayed to the plant or fire control centre.

Where foam is used for total flooding of an area in which personnel are normally present, the system should be locked-off from automatic operation unless a suitable delay period is arranged between alarm and system operation, so that personnel may evacuate the effected area before foam is discharged.

All operating devices whether manual or automatic should be suitable for the service conditions they will encounter. They should not be readily rendered inoperative, nor be susceptible to inadvertent operation, by environmental factors such as high or low temperature, atmospheric pollution, humidity, or marine environments.

Requirements and Recommendations for Fire Detectors, Alarms and Controls of foam system

1. Detection and alarm equipment may be electrical, pneumatic, hydraulic or mechanical like link, line type.
2. Other than link/line systems, automatic detection and control equipment should be designed to give a positive warning of any fault or abnormality which may render the system inoperative like loss of power.
3. Automatic detection and control equipment should comply with relevant Standards
4. Automatic detection equipment should provide a local alarm at the control point of each automatic system, as well as at the plant or central control point.

COMMISSIONING AND PERFORMANCE TESTS OF FOAM SYSTEM

General

The completed system should be inspected and tested to determine that it is properly installed, and that it will function as designed. A commissioning test programme should be submitted by the installer.

Inspection

A visual inspection should be conducted to ensure that the system has been installed correctly. Inspection should include conformity with design drawings and specifications, continuity of pipework, checking, removal of temporary blinds, accessibility of valves, control and gauges, and proper installation of foam-makers, vapour seals, and proportioning devices. All equipments should be checked for correct identification and operating instructions.

Pressure Tests

All pipework, except that handling expanded foam for other than base injection application, should be subjected to a hydrostatic pressure test at 14 bar or 1·5 times the maximum pressure anticipated, whichever is the greater for a period of 2 hours. All normally dry horizontal pipework should be inspected for drainage.

Component Inspections

All operating devices and equipments should be inspected for proper functioning and a record should be made to indicate that the required performance will be met.

Discharge Tests

Whenever possible, flow and distribution tests should be conducted to ensure that the hazard is fully protected in conformity with the design specification, and to determine the running pressure, actual discharge rate, consumption rate of foam concentrate, man power requirements and other operating characteristics. Wherever possible the foam discharged should be inspected and preferably tested to ensure that it is satisfactory for the intended purpose performance.

System Restoration

After completion of the performance tests, the system should be flushed and restored to operational condition.

MONITORS AND FOAM BRANCH PIPE SYSTEMS

General

This systems in which the foam is applied through fixed, portable, or mobile or portable foam branch pipes to provide primary protection for flammable liquid spills, bund areas and storage tank fires.

NOTE—Portable foam, branch pipes are also suitable for extinguishing rim fires in floating roof tanks.

System Design

General

Consideration should be given to the advantages and limitations when selecting one of many variations of this type of systems

Possible Advantages

1. Foam can be projected under favourable circumstances, over considerable distances and to significant heights.
2. Portable and mobile monitor systems may be housed out of the weather, are more likely to be kept in a serviceable condition, will be unaffected by explosion or flame exposure before firefighting commences and are available for use in all parts of the complex to be protected. They may also be set up in the most favourable upwind position.
3. Oscillating monitors discharge foam evenly over very large areas, automatically.
4. Fixed monitors may be remotely controlled from considerable distances thus rendering them suitable, for example, in oil jetty protection and fire tug use.

Possible Limitations

1. Foam discharge may be affected by any wind and fires up draught resulting in discharge outside the affected area.
2. Tanks having ruptured roofs with only limited access for foam are not easily extinguished by monitor application from ground level.
3. Uniform foam distribution may not be achieved easily.
4. Fixed automatically-operated monitors applying foam horizontally into a fire area may be obstructed by equipment positioned temporarily.
5. Portable foam branch pipes are not suitable for the primary protection of storage tanks of over 9 m diameter and 6 m height. 9
6. Foam monitors are not generally suitable for the primary protection of fixed roof storage tanks of over 20 m diameter.
7. Monitor systems are not generally suitable for floating roof tank rim fires.
8. Where mobile or portable equipment is used the time required to set up the equipment may increase the fire preburn period and may make extinction more difficult.

Application Rates

Systems should be designed to deliver not less than the minimum foam solution rates

Duration of Discharge

If the system discharges at a rate above the minimum specified then the operating time may be reduced proportionately, but should not be less than 70 percent specified discharge time.

Supply of Foam Concentrate

The minimum quantity of foam concentrate which should be held in immediate readiness is determined by the following formulae:

Minimum quantity of foam concentrate

The risk requiring the greatest quantity of foam concentrate should be used to determine the amount to be held at immediate readiness.

Allowance should be made for the quantity of foam concentrate needed to fill the feed lines installed between the source and the most remote monitor or branch/pipe. Where it is desired to continue the water supply after the foam concentrate is exhausted, in order to displace the solution or concentrate in the feed lines, no additional concentrate need be provided.

There should be a reserve supply of foam-producing materials readily available.

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