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) for various size tanks.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.for a 150 ft. dia. tank containing gasoline.1 x Atmospheric Foam Concentrate StorageTank 3,100 Gallons1 x Electric powered Foam Pump Proportioningskid with prepiped 6" ratio controller ( FoamChambers ) and prepiped 2 1/2" ratiocontroller ( Supplementary Hose Lines )4 x Model FC4 or FC6 Foam Chambers3 x 50 gpm Hand Line nozzles3,051 x Gallons 3% AFFF ( plus any additionalfor testing of the system )NOTE:When protecting multiple storage tanks the foamsystem is to be sized to protect the single largesthazard.Fig. 9 depicts a manual foam pump skid systemshowing all necessary piping, valves, dischargedevices, ratio controller, foam pump and foamstorage tank for the above system.Fig. 10 shows a Cone Roof Storage Tank with aSemi-Fixed Foam System.The following example shows the foam systemrequirements for seal protection 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 foam solution required.Type of Discharge Device - Foam MakersDischarge Duration - 20 min.279 x 20 = 5,580 gallons of foam solution - x.03 ( 3% AFFF ) = 167.4 gallons of foamconcentratedQuantity of Foam Makers Required ( Per NFPA11) 6 required.Add supplementary hose lines per example forCone Roof Tank with Foam Chambers.NOTE:The number of fixed foam 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 foam dam and every80 ft. ( 24.4 m ) of tank circumference when usinga 24" ( 610 mm ) high foam dam.In accordance with NFPA 11Foam Dam Design - The foam 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 or otherwisesecurely fastened to the floating roof. The foamdam is designed to retain foam at the seal area ata sufficient depth to cover the seal area whilecausing the foam 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 or a combustible secondaryseal using a plastic foam log.It is to be at least 2" ( 51 mm ) higher than anyburnout panels in metal secondary seals.
Foam dams are to be at least 1 ft. ( 0.3 m ) butno more than 2 ft. ( 0.6 m ) from the edge of thefloating roof.Foam solution & rain water is to be drained by,slotting the bottom of the dam on the basis of 0.04sq. in. of slot area per sq. ft. (278 mm sq./sq. m)of diked area while restricting the slots to 3/8 in.(9.5 mm) in height. Excessive dam openings fordrainage should be avoided to prevent loss offoam through the drainage slots.SUB-SURFACE SYSTEM( Sub-surface injection of foam is generally notrecommended for fuels that have a viscositygreater than 2,000 ssu ( 440 centistokes ) at theirminimum anticipated storage temperature ).Example of a Sub-Surface Base Injection SystemCone Roof Tank - 80 ft. diameterFuel - GasolineFoam Concentrate - 3%-6% AR-AFFFSurface Area - =40' x 40' x 3.1417 = 5,026.7 sq. ft.App. Rate - .10 gpm per sq. ft..10 x 5,027 sq. ft. = 502.7 gpm of foam solutionDischarge Duration - 55 min.Quantity of Foam Concentrate required -503 (502.7 ) x 55 x .03 = 829.95 gallonsDischarge Device - Qty. 1 High Back PressureFoam Maker ( " Foam generator " )Number of Discharge outlets inside tankQty. 1 (Tank 80 ft. or less) (Per NFPA 11)Supplementary hose lines per example for ConeRoof Tank.The following chart shows the number of dischargeoutlets required inside the tank.Tank DiameterNumber of Discharge Outlets RequiredFlash Point below Flash Point 100 o F100 o F (38 o C) (38 o C) or HigherUp to 80 ft. ( 24 m ) 1 1Over 80 to 120 ft. ( 24 - 36 m ) 2 1Over 120 to 140 ft. ( 36 - 42 m ) 3 2Over 140 to 160 ft. ( 42 - 48 m ) 4 2Over 160 to 180 ft. ( 48 - 54 m ) 5 2Over 180 to 200 ft. ( 54 - 60 m ) 6 3Over 200 ft. ( 60 m ) 6 3Plus 1 outlet forPlus 1 outlet foreach additionaleach additional5,000 sq. ft. 7,500 sq. ft.(465 sq. m) (697 sq. m)Equipment list for the above example using abladder tank foam supplied foam system.• 1 x 900 Gallon vertical style bladder tank.• 1 x 4" Between flange style ratio controller.• 1 x 2 1/2" Threaded type ratio controller ( forsupplementary hose lines ).• 1 x Model CFM500 High Back Pressure FoamMaker ( HBPFM ).• Supplementary hand line nozzles and foamconcentrate.Determining Number of Discharge Outlets forSubsurface Base Injection.The number of discharge outlets required is basedon the tank diameter and the flash point of thefuel as shown in the above chart.FOAM MONITORS AND HANDLINESMonitors are not to be considered as the primarymeans of protection for fixed roof tanks over 60 ft.in diameter. Foam handlines are not to beconsidered as the primary means of protection fortanks over 30 ft. in diameter or those over 20 ft. inheight.Application Rates Using Monitors orHandlinesThe minimum foam solution application rate isbased on the assumption that all discharging foamwill reach the area being protected. In consideringactual solution flow requirements, considerationshould be given to potential foam losses fromclimatic conditions and thermal updraft of the fire,etc.The following chart shows application density andduration for monitors and handlines on tankscontaining hydrocarbons.Hydrocarbon Type Minimum MinimumApplication Rate Dischargegpm/ft 2 (L/min.)/m 2 Time(min.)Flash point between100 o F and 140 o F(37.8 o C and 93.3 o C) 0.16 6.5 50Flash point below 100 o F(37.8 o C) or liquids heatedabove their flash points 0.16 6.5 65Crude Petroleum 0.16 6.5 65
Page 1 and 2: FIXED OR SEMI-FIXEDFOAM FIRE PROTEC
Page 3 and 4: SUB-SURFACE BASE INJECTIONThe sub-s
Page 5: Discharge device - Foam Chamber, Qt
Page 9 and 10: STORAGE TANKPROTECTION WITH HIGHFLO
Page 11 and 12: Cooling of adjacent tanks is best a
Page 13 and 14: TABLE 1WATER FLOW RATE TO PRODUCE 3
Page 15 and 16: TABLE 3FRICTION LOSS PER 100 FEET /
Page 17 and 18: FIG. 10SEMI-FIXED FOAM SYSTEM WITH
Page 19 and 20: TYPICAL OUTLETS FOR SUB-SURFACE INJ
Page 21 and 22: EXPANDED FOAM VELOCITY vs PIPE SIZE
Page 23 and 24: 50FOR SI UNITS1gpm=3.785 l / min.1p
Page 25 and 26: InternalFloatingRoofFOAM CHAMBER TO
Page 27 and 28: EXAMPLES OF TYPICAL TOP AND BELOW S
Page 29 and 30: DikeMonitor(Typical)WaterSupplyTANK
Page 31 and 32: TYPICAL ARRANGEMENT FOR SUB-SURFACE
Page 33 and 34: STORAGE TANK PROTECTION SUMMARYFixe

fixed or semi-fixed foam fire protection systems for storage tanks - NIFV

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