fixed or semi-fixed foam fire protection systems for storage tanks - NIFV
fixed or semi-fixed foam fire protection systems for storage tanks - NIFV
fixed or semi-fixed foam fire protection systems for storage tanks - NIFV
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Chemguard to establish recommended applicationrates. The minimum discharge durationis 55 min.The following chart indicates the minimumoperating time of the supplementary hosestream(s) f<strong>or</strong> various size <strong>tanks</strong>.Diameter of LargestTankMinimum OperatingTimeUp to 35 ft. ( 10.5 m ) 10 min.35 to 95 ft. ( 10.5 to 28.5 m ) 20 min.Over 95 ft. ( 28.5 m ) 30 min.Equipment List using a Foam Pump Skid Assy.f<strong>or</strong> a 150 ft. dia. tank containing gasoline.1 x Atmospheric Foam Concentrate St<strong>or</strong>ageTank 3,100 Gallons1 x Electric powered Foam Pump Prop<strong>or</strong>tioningskid with prepiped 6" ratio controller ( FoamChambers ) and prepiped 2 1/2" ratiocontroller ( Supplementary Hose Lines )4 x Model FC4 <strong>or</strong> FC6 Foam Chambers3 x 50 gpm Hand Line nozzles3,051 x Gallons 3% AFFF ( plus any additionalf<strong>or</strong> testing of the system )NOTE:When protecting multiple st<strong>or</strong>age <strong>tanks</strong> the <strong>foam</strong>system is to be sized to protect the single largesthazard.Fig. 9 depicts a manual <strong>foam</strong> pump skid <strong>systems</strong>howing all necessary piping, valves, dischargedevices, ratio controller, <strong>foam</strong> pump and <strong>foam</strong>st<strong>or</strong>age tank f<strong>or</strong> the above system.Fig. 10 shows a Cone Roof St<strong>or</strong>age Tank with aSemi-Fixed Foam System.The following example shows the <strong>foam</strong> systemrequirements f<strong>or</strong> seal <strong>protection</strong> of a 150 ft.diameter open top floating roof tank.Type of Tank - Open Top Floating Roof TankDiameter of Tank - 150 ft.Type of Fuel - GasolineFoam Dam installed on roof - Yes - 2 ft. fromtank wall and 2 ft. in heightSq. ft. area of annular ring - 930 sq. ft.Application Rate - .30 gpm per sq. ft. ( PerNFPA 11).30 x 930 sq. ft. = 279gpm of <strong>foam</strong> solution required.Type of Discharge Device - Foam MakersDischarge Duration - 20 min.279 x 20 = 5,580 gallons of <strong>foam</strong> solution - x.03 ( 3% AFFF ) = 167.4 gallons of <strong>foam</strong>concentratedQuantity of Foam Makers Required ( Per NFPA11) 6 required.Add supplementary hose lines per example f<strong>or</strong>Cone Roof Tank with Foam Chambers.NOTE:The number of <strong>fixed</strong> <strong>foam</strong> discharge points on anopen top floating roof tank is determined by thecircumference of the tank.The maximum spacing between discharge pointsis 40 ft. ( 12.2 m ) of tank circumference whenusing a 12" ( 305 mm ) high <strong>foam</strong> dam and every80 ft. ( 24.4 m ) of tank circumference when usinga 24" ( 610 mm ) high <strong>foam</strong> dam.In acc<strong>or</strong>dance with NFPA 11Foam Dam Design - The <strong>foam</strong> dam should becircular and constructed of at least No. 10 USStandard Gage Thickness ( .134 in./3.4 mm )steel plate. The dam is to be welded <strong>or</strong> otherwisesecurely fastened to the floating roof. The <strong>foam</strong>dam is designed to retain <strong>foam</strong> at the seal area ata sufficient depth to cover the seal area whilecausing the <strong>foam</strong> to flow laterally to the point ofseal rupture.Dam height is to be at least 12" ( 305 mm ) andshould extend at least 2" ( 51 mm ) above anymetal secondary seal <strong>or</strong> a combustible secondaryseal using a plastic <strong>foam</strong> log.It is to be at least 2" ( 51 mm ) higher than anyburnout panels in metal secondary seals.