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Warehouse Foam System

It is often necessary to install a fixed foam fireprotection system to protect warehouse facilitieswhere flammable liquids are stored or used during amanufacturing process. Listed below are twodifferent methods of supplying fire protection:

1. Foam-Water Sprinkler System

Closed Head

Open Head/Deluge

2. High Expansion Foam System

Design of the foam-water sprinkler system generally

falls under one or more of the following:

NFPA 13: Installation of Sprinkler Systems

NFPA 16: Installation of Deluge Foam-WaterSprinkler and Foam-Water SpraySystems

NFPA 30: Flammable and Combustible LiquidsCode

AHJ: Authority Having J urisdiction.Some authorities have their designcriteria for both closed head anddeluge type systems.

Design Example:

Type System: DelugeDesign Standard: NFPA 16Dimensions: 80' x 50'Stored Product: Assortment of Polar Solvent and

Hydrocarbon based liquidsFoam Concentrate: 3% AR-AFFF (suitable for use

on both Hydrocarbons and Polar Solvents)Warehouse Area: 80 x 50=4,000 sq. ft.Application Rate: .16 gpm per sq. ft.

The application rate may be higherdepending on types of polar solvent liquidsstored.

Flow in GPM of foam solution: .16 x 4,000=640Discharge Duration: 10 minutes 640 x 10 = 6,400

gallons of foam solutionFoam Concentrate: 6,400 x .03 =192 gallonsNumber of sprinkler heads: 40 (extra hazard

occupancies, approx. 100 sq. ft. persprinkler)

MAJOR FOAM SYSTEM COMPONENTS

1 x 200 Gallon vertical style bladder tank

1 x 4" between flange style ratio controller (Flowrange with AR-AFFF type concentrate is 400 -1,500 gpm)

The above design criteria could also apply to anysystem designed in accordance with NFPA 16However, many times with a closed head foamsprinkler system, the Authority Having J urisdiction

over the system approval will require an applicationrate in excess of .16 gpm per sq. ft. over a specificarea. Application densities ranging from .20 to .40gpm per sq. ft. are often used. Before the finasizing of the foam system, establish with theAuthority on what design density will be requiredover what area. For example, an insurance carriemight require an application rate of .30 gpm per sqft. over 1,500 sq. ft. depending on the sprinklehead used. NFPA 30 requires a similar applicationrate over 1,500 sq. ft. when using high temperaturesprinkler heads or .30 gpm per sq. ft. over 2,550 sqft. when using ordinary temperature sprinkle

heads.

DISCHARGE APPLICATION AREA

The area to be protected must be determined focorrect sizing of the foam system. The area canvary according to which NFPA standard oAuthority Having J urisdiction guideline the systemis designed. NFPA 16 requires that the system bedesigned to flow foam over the entire risk areaNFPA 16 requires the system demand area to bebased on 5,000 sq. ft. unless occupancy standardsspecify a different demand area. NFPA 30 requires

the system design to be based on 2,000 sq. ftwhen used to cover solid pile or palletized storageof flammable liquids. If the system is to include anin-rack foam-water sprinkler system, the overheadmay be based on 1,500 sq. ft. for high temperatureheads and 2,550 sq. ft. if ordinary temperaturesprinkler heads are used. The in-rack system isbased on three sprinkler heads per level beingdischarged multiplied by the number of levels high.

CHEMGUARD204 S. 6

thAve Mansf ield, Tx 76063 (817) 473-9964 FAX (817) 473-0606

www.chemguard.comDATA SHEET #D10D03150REVISION: 09/2005


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DISCHARGE DURATION

NFPA 16 requires discharge duration of 10 minutes.NFPA 30 requires discharge duration of 15 minutes.Many Authorities Having J urisdiction may requiredischarge duration of 20 minutes.

Design Example:

Type System: Wet PipeDesign Standard: NFPA 30Dimensions: 80' x 50'Stored Product: Assortment of Polar Solvent and

Hydrocarbon based liquidsFoam Concentrate: 3% AR-AFFFWarehouse Area: 80 x 50 =4,000 sq. ft.Application Rate: 0.30 gpm per sq. ft. over 2,000

sq. ft.Flow in GPM of Foam Solution: 0.30 x 2,000 =600Foam concentrate required: 600 x .03 =18 gpmDischarge Duration: 15 minutes

Foam Concentrate: 18 x 15 =270 gallons

There is one major difference between a delugeand a closed head system when using foam. With adeluge system, when the system operates, allheads receive foam solution. Only those headsactuated will receive foam solution on a closedhead system. THIS will only happen WHEN thelow-end flow rate (gpm) of the selected ratiocontroller is reached. In the above example, a 4"ratio controller is being used so there must be aminimum flow of 400 gpm before foam isgenerated.

With each sprinkler head discharging approximately16 gpm, at least 25 heads must open to ensurecorrect operation of the foam system. This is amajor disadvantage when using a bladder tank witha closed head foam sprinkler system.

A solution to this issue is to use an Ultra-wideproportioner instead of a ratio flow proportioner.

The Ultra-wide proportioner will proportion correctlyat a minimal flow of 20 gpm which is typically onesprinkler head discharging.

Many installations are using In-line BalancedPressure Proportioning Units (ILBP) in conjunctionwith positive displacement foam pumps in lieu ofbladder tanks. The major advantage is that with afoam pump system, mixing of the foam concentrateand water to form the foam solution will take placeat lower rates through the same size ratio controllerthan with a bladder tank. With the foam pump, theconcentrate has a slight positive pressure over the

water at the ratio controller; therefore, it is forcedinto the water stream even at low flow rates throughthe ratio controller. If using a 3% concentrate, theratio mix may be 4-6% at low flows.

In a closed head foam water sprinkler system, it is

better to have a rich foam solution being dischargedthrough the activated sprinkler heads when the flowis below the range for the ratio controller. A bladdetank may not proportion foam concentrate at flowrates below the minimum U.L. Listed flow range

This occurs because the flow through the controlleis insufficient to create the low-pressure area, whichallows the foam concentrate from the bladder tankto flow into the ratio controller.


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