Fire Service Manual Volume 1 - Ukfrs

The performance of firefighting foams can begreatly influenced by:1.2 Historical Development ofFirefighting Foams The type of foam-making equipmentused and the way it is operated and maIntained.1877 - Chemical foam, first patented by a Britishscientist. The type of foam concentrate used. The type of fire and the fuel involved. The tactics of foam application. The rate at which the foam is applied. The quality of the water used. The length of pre-burn.The most effective and efficient use of firefightingfoam can only be achieved after full considerationhas been given to all of the above factors.This Volume of the Manual describes a11 aspects offirefighting foam and discusses the types of equipment typically used by the fire service to produceit. Topics covered include the properties of foamconcentrates, finished foams and foam equipment;application rates; and the classes of, and types of,fire for which foam can be used.Volume 2 of the Manual describes the operationaluse of foam including recommended minimumapplication rates and application techniques;practical scenario considerations; and the logistics involved in dealing with fires in storagetanks.At the rear of this Volume, there is a glossary ofterms used in this Manual and other terms thatmay be used in connection with firefightingfoams.It must be stressed that this Manual only givesgeneral information on the use of firefightingfoams. Incidents requiring the use of foam arevaried and preplanning in support of an effective risk assessment at the commencement of anincident is of the utmost importance to ensurethat the correct foams, equipment and tacticsare selected and employed.2Fire Service Manual1904 - First successful use of chemical foam.Used to extinguish an I I metre diameter naphthastorage tank fire in Russia. Foam produced frommixing together large quantities of two chemicalsolutions.1914 - Austrian engineers produce foam byintroducing a powder into running water.1920s - Protein foam concentrate first producedalong with equipment designed for the productionand delivery of this first 'mechanical' foam.1930s - Development of early chemical foamswith alcohol resisting properties. The concepts ofaspiration and proportioning were developed formechanical foam systems much as we know themtoday. Experimental work started on synthetictypes of foam concentrate.1940s - 3% Protein foam concentrates developedto offer space and weight savings over the existing 6% concentrates.1990s - Development of alcohol resistant foamconcentrates to produce versions that can be usedat 3% concentration on both hydrocarbons andwater-miscible liquids. Introduction of class Afoam concentrates.1.3 How Foams Extinguish FireFirefighting foam is much lighter (less dense) thanall liquid fuels and so it floats on their surfaces.The foam blankets that are formed help to knockdown and extinguish these fires in the followingways: By excluding air (oxygen) from the fuelsurface. By separating the flames from the fuelsurface. By restricting the release of flammablevapour from the surface of the fuel. By forming a radiant heat barrier whichcan help to reduce heat feedback fromflames to the fuel and hence reduce theproduction of flammable vapour. By cooling the fuel surface and any metalsuli'aces as the foam sol ution drains outof the foam blanket. This process alsoproduces steam which dilutes the oxygenaround the fire.1950s - Low, medium and high expansion foamscould now be produced from a single syntheticfoam concentrate. First water-miscible liquidresistant mechanical foam concentrate developed.water have been mixed together prior to arrivingat the foam-making equipment. Occasionally,premix solutions are produced by mixing the correct proportions of water and foam concentrate ina container, such as an appliance tank, prior topumping to the foam-making equipment. In addition, some types of foam-making equipment arefitted with a means of picking up foam concentrate at the equipment; these are known as 'selfinducing' with the mixing taking place in thefoam-making equipment itself.The second stage is the addition of air to the foamsolution to make bubbles (aspiration) to producethe finished foam. The amount of air addeddepends on the type of equipment used. Hand-heldfoam-making branches generally only mix relatively small amounts of air into the foam solution.Consequently, these produce finished foam withlow expansion (LX) ratios, that is to say, the ratioof the volume of the finished foam produced bythe nozzle, to the volume of the foam solution usedto produce it, is 20: 1 or less. Other equipment isavailable which can produce medium expansionfoam (MX) with expansion ratios of more than20: I but less than 200: 1, and high expansion foam(HX) with expansion ratios of more than 200: I andpossibly in excess of 1000: 1.The following Sections describe in more detailsome of the important factors of foam productionthat were introduced above.1.4.2Percentage Concentration1.4 Production of Fini bed Foam1960s - Fluoroprotein and AFFF (Aqueous Filmforming Foam) foam concentrates developed.Improved alcohol resistant foams developed.1970s - Further development of alcohol resistantfoam concentrates to produce mUlti-purpose foamsfor use at 3% on hydrocarbons and 6% on watermiscible liquids. "Hazmat" foams developed for thesuppression of vapour from hazardous materials.1980s - Development of alcohol resistant foamconcentrates to produce AFFF-AR (alcohol resistant AFFF). Development of fluoroprotein foamsto produce FFFP (Film-forming Fluoroprotein)and multi-purpose FFFP-AR (Alcohol ResistantFFFP) foam concentrates.1.4.1GeneralFinished foam is produced from three main ingredients; foam concentrate, water and air. There areusually two stages in its production. The firststage is to mix foam concentrate with water toproduce a foam solution. The foam concentratemust be mixed into the water in the correct proportions (usually expressed as a percentage) inorder to ensure optimum foam production andfirefighting performance. This proportioning isnormally carried out by the use of inductors (orproportioners) or other similar equipment. Thisresults in the production of a 'premix' foam solution. In other words, the foam concentrate andAll foams are usually supplied as liquid concentrates. These must be mixed with water, to form afoam solution, before they can be applied to fires.They are generally supplied by manufacturers aseither 6%, 3% or I % foam concentrates. Thesehave been designed to be mixed with water as follows: 6 % concentrates6 parts foam concentrate in 94 parts water, 3 % concentrates3 parts foam concentrate in 97 parts water, 1% concentratesI palt foam concentrate in 99 parts water.Firefighring Foam - Technical3

1% concentrate is basically six times as strong as 6% concentrate, and 3% concentrate is twice asstrong as 6% concentrate. However, the firefightingcharacteristics of finished foam produced from 1%.3% and 6% concentrates of a particular type ofmanufacturer's foam should be virtually identical.The lower the percentage concentration, the lessfoam concentrate that is required to make finished foam. The use of say 3% foam concentrateinstead of 6% foam concentrate can result in ahalving of the amount of storage space requiredfor the foam concentrate. with similar reductionsin weight and transportation costs, while maintaining the same firefighting capability. Not allfoam concentrates are available in the highly concentrated J % form, e.g. alcohol resistant and protein based foam concentrates. This is becausethere are technical limits to the maximum usageconcentrations of some of the constituents offoam concentrates.It is extremely important that the foam inductionequipment used is set to the correct percentage. If3% concentrate is induced by an induction systemset for 6% concentrate, then twice the correctamount of foam concentrate will be used creatinga foam solution rich in foam concentrate. Not onlywill this result in the foam supply being depletedvery quickly and an expensive waste of foam concentrate, but it will also lead to finished foam withless than optimum firefighting performance,mainly due to the foam being too stiff to flow adequately. Alternatively, using 3% foam concentratewhere the system is set for I % will result in a solution with too little concentrate to make foam withadequate firefighting performance. 1.4.3 As. it leaves the branch. As it travels through the air due to theturbulence produced by the stream. Fire Service Manualcan be advantageous if rapid film-formation on afuel is required (see Chapter 4, Section 4.4).Secondary aspirated foams generally have anexpansion ratio of less than 4: I.It is highly unlikely that a foam solution can beapplied operationally to a fire in such a way that noaspiration occurs. However, should such circumstances occur, then this would be referred to as anon-aspirated application. Some water additives,such as wetting agents, may be formulated so thatthey do not foam; use of these types of additivewould result in non-aspirated application, eventhrough purpose designed foam-making equipment.1.5.21.5 Foam Expansion Ratiost1.5.1When it strikes an object. This causesfUI1her turbulence and air mixing.Expansion ratioThere is sufficient air entrained by these processesto produce a foam of very low expansion (oftenwith an expansion ratio of less than 4: I).To more accurately describe the different types offinished foam produced. the terms 'primary' or'secondary' aspirated are preferred: 800 litresvolume of foam solution100 litres8This foam would also be referred to as having anexpansion of 8.Primary aspirated foam - finished foamthat is produced by purpose designed foammaking equipment.Typical firefighting foam expansion ratio rangesare:Secondary aspirated foam - finishedfoam that is produced by all other means,usually standard water devices.Secondary aspiration will normally result in a poorquality foam being produced, due to insufficientagitation of the foam/air mixture. That is to say, thefoam will generally have a very low expansionratio and a very short drainage time (see below).However. foam blankets with short drainage timesvolume of foam, t Equipment Used For GeneratingDifferent Expansion Ratio FoamsPrimary aspirated low expansion foams areusually produced by using purpose designed foammaking branches or mechanical generators.Secondary aspirated low expansion foams are usually produced by using standard water deliverydevices although some purpose designed largecapacity monitors have been produced for this particular type of application (see Volume 2).GeneralAs mentioned previously, finished foam is usuallyclassified as being either low, medium or highexpansion. The expansion, or more strictly theexpansion ratio, of a foam is the ratio of the volume of the finished foam to the volume of thefoam solution used to produce it. For example. if100 litres of foam solution were passed through afoam-making branch and 800 litres of foam wereproduced, then the expansion ratio of the foamwould be calculated as follows:AspirationOnce the correctly mixed foam solution has beendelivered to the end of a hose line, there are a number of forms in which it can be applied to the fire.Generally, foam application is referred to as beingeither' aspirated' or 'non-aspirated':4'Non-aspirated' implies that no aspirationof the foam solution has taken place.Consequently, the term 'non-aspirated foam' isoften used incorrectly to describe the product of afoam solution that has been passed through equipment that has not been specifica.lly designed toproduce foam, such as a water branch. However,the use of this type of equipment will often resultin some aspiration of a foam solution. This isbecause air is usually entrained into the jet or sprayof foam solution: It is also vely important to have compatibility offoam-making equipment and induction equipment,and just as importantly, foam induction equipmentmust be checked regularly to ensure that it is operating correctly and giving an accurate rate of induction.' Aspirated' foam is made when the foamsolution is passed through purposedesigned foam-making equipment, such asa foam-making branch. These mix in air(aspirate) and then agitate the mixturesufficiently to produce uniformly sizedbubbles (finished foam).Low expansionless than or equalto 20: IMedium expansiongreater than 20: Ibut less than orequal to 200: IHigh expansiongreater than 200: IMedium and high expansion foams are usually primary aspirated through special foam-makingequipment. This equipment produces foam byspraying the foam solution on to a mesh screen ornet. Air is then blown through the net or mesheither by entrainment caused by the spray nozzle,or by an hydraulic. electric or petrol motor drivenfan.1.5.3Foam ConcentratesThe amount that a foam solution can be aspiratednot only depends on the equipment, but also on thefoam concentrate that is used. For instance, synthetic detergent (SYNDET) foam concentrates arethe only type that can be used to produce low,medium and high expansion foams; protein foamconcentrates can only be used to produce lowexpansion foam and the remaining commonly usedfoam concentrates (i.e. AFFF, AFFF-AR, FP, FFFPand FFFP-AR. see Chapter 2) are mostly intendedfor use at low expansion. although they can also beused to produce medium expansion foam.For flammable liquid fuel fires, effective secondary aspirated foam can only be produced usinga film-forming foam concentrate.Chapters 2, 3 and 4 discuss in detail the varioustypes and properties of foam concentrates and finished foams.Firejighling Foam - Technical5[

F-refghtingTechnical1.5.4Typical Uses and Properties of Low,Medium and High ExpansionFinished FoamsThe various expansion ratios are typically used forthe following applications: Primary Aspirated Finished FoamsLow expansionLarge flammable liquid fires (i.e. storagetanks, tank bunds)Road traffic accidentsFlammable liquid spill firesVapour suppressionHelidecksJettiesAircraft crash rescuePortable fire extinguishersMedium expansion finished foam can only beprojected over small distances. However, withexpansions of between 20 and 200, large quantitiesof foam are produced from relatively smallquantities of foam solution. This, combined withits ability to flow relatively easily, makes mediumexpansion foam ideal for covering large areasquickly.High expansion finished foam flows directly outof the foam-making equipment and is not projected any appreciable distance. Its coverage of largeareas can also be slow but the immense quantity offoam produced (expansion ratios are sometimes inexcess of 1000: I) can quickly fill large enclosures.Often, flexible ducting is required to transport thefoam to the fire. Due to its volume and lightness,high expansion foam is more likely than low andmedium expansion foam, to break up in moderately strong wind conditions (Reference I).oam-Chapter 2 - Foam Concentrates2.1 Types of Foam Concentrate2.1.1 GeneralThere are a number of different types of foam concentrate available. Each type normally falls intoone of the two main foam concentrate groups, thatis to say, they are either protein based or syntheticbased, depending on the chemicals used to produce them.Medium expansionVapour suppressionFlammable liquid storage tank bundsSmall cable ductsSmall fires involving flammable liquids,such as those following road trafficaccidentsTransformer protectionHigh expansionKnockdown and extinction in, andprotection of, large volumes such aswarehouses, aircraft hangars, cellars, sh ips'holds, mine shafts, etc.Large cable ductsVapour suppression (including cryogenicliquids such as LNG/LPG) Secondary Aspirated Finished FoamsLarge flammable liquid fires (i.e. storage tanks,tank bunds)HelidecksAircraft crash rescuePortable fire extinguishersLow expansion finished foams can be projectedover reasonably long distances and heightsmaking them suitable in many situations for useagainst fires in large storage tanks.6Fire Service ManualThe equipment used to produce secondary aspirated foam is often standard water type branches andnozzles although there are some specificallydesigned large capacity nozzles available. Thefoam produced in this way is not well worked (seeChapter 4, Section 4.2), has a very low expansionratio and short drainage time, and tends to be veryfluid. These properties, combined with the filmforming nature of the foam concentrates used, canresult in a finished foam blanket that can quicklyknockdown and extinguish fires of some liquidhydrocarbon liquid fuels. This ability can makethem ideal for use in certain firefighting situationssuch as aircraft crash rescue. However, the foamblanket tends to collapse quickly, so providingvery poor security and resistance to burnback.Secondary aspirated foam can be thrown over agreater distance than is possible with primary aspirated low expansion foam. This has resulted inequipment being designed specifically to projectsecondary aspirated foam into large storage tankfires. Manufacturers of this equipment recommendthe use of film-forming foam concemrate types forsuch applications. They claim that the finishedfoam produced usually has an expansion ratio ofless than 4: I .h pter Protein based foam concentrates include:Protein (P)Fluoroprotein (FP)Film-forming f1uoroprotein (FFFP)Alcohol resistant FFFP (FFFP-AR) Synthetic based foam concentratesinclude:Synthetic detergent (SYNDET)Aqueous film-forming foam (AFFF)Alcohol resistant AFFF (AFFF-AR)The characteristics of each of these foam concentrates, and the finished foams produced from them,varies. As a result, each of them has particularproperties that makes them suitable for someapplications and unsuitable for others.For protein based foam concentrates, the basicchemical constituent is hydrolysed protein,obtained from natural animal or vegetable sources.It is the hydrolysed protein (the 'foaming agent')that enables bubbles to be produced.For synthetic based foam concentrates, the basicconstituents are detergent based foaming agents.To enhance the firefighting properties of thesebasic constituents, and hence produce the differentfoam concentrate types, chemicals are added.Various types of surface active agents (or surfactants) are added to many firefighting foam concentrates. These are used to reduce the amount of fuelpicked up by the finished foam on impact with fuel(i .e. they increase fuel tolerance) and to increasethe fluidity of the finished foam (i.e. they make iteasier for finished foam to flow over some fuelsand other surfaces).Surface active agents are also used as foamingagents because they readily produce foam bubbleswhen mixed with water. Consequently, hydrocarbon surface active agents, or as they are more commonly known, synthetic detergents, are the mainconstituents of synthetic based foam concentrates.Surface active agents are also used in some proteinbased foams.Surface active agents can help to reduce the surface tension of water. This not only helps in theformation of foam bubbles but also increases theability of the water to penetrate and spread. This isparticularly important when fighting class A firesbecau e it can help water to penetrate and cool theburning material.In film-forming foam concentrates, surface activeagents form an aqueous film of foam solutionwhich, in certain conditions, can rapidly spreadover the surface of some burning hydrocarbons toaid knockdown and extinction.Other chemicals may also be added to foamconcentrates. These include corrosion inhibitors,solvents (to reduce viscosity and to enhance foaming properties), preservatives (to prevent thegrowth of bacteria an

Fire Service Manual Issued under the authority ofthe Home Office (Fire and Emergency Planning Directorate) The Fire Service College * 0 0 0 7 2 9 57 U * e I (01608) 650831 Ext.2338 library@fireservicecollege.ac.uk THE FIRE SERVICE COLLEGE LIBRARY MORETON-INMARSH GLOUCESTERSHIRE GL560RH 2.5. 1 ·o't FIRE SERVICE COLLEGE LIBRARY .