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DESCRIPTION

The Chemguard High Expansion (Hi-Ex) FoamGenerator is one component in a High ExpansionFoam Fire Suppression System. It requires noexternal power other than foam solution to ensurecorrect operation.

It is recommended by Chemguard that the Hi-ExFoam Fire protection system be installed by acontractor having previous experience in installingfixed fire protection foam systems.

The Hi-Ex Foam Fire Protection System must bedesigned and installed in strict accordance withNFPA 11A, the Standard for High ExpansionFoam Systems and any guidelines established bythe Authority having Jurisdiction or Insurance Car-rier.

The output of a Chemguard Hi-Ex Foam Gene-rator in a fixed installation depends on whichgenerator is selected. These generators areavailable in a wide flow range ( in cubic feet permin. ) at various foam solution inlet pressures.

When multiple units are used an almost limitlessoutput can be achieved.

The Hi-Ex Foam System is suitable for use for fireextinction of solid fuel or flammable liquid fires inareas where the expanded foam can be contain-ed. Examples:

• Ship holds• Aircraft hangars• Hazardous material/waste storage areas• Flammable liquid packaging areas• Flammable liquid drum storage• Warehouse areas such as: Rolled paper, tire

storage, in rack storage of combustible mate-rials and boat storage.

High Expansion Foam Systems have been instal-led as added protection for Liquid Natural Gasfacilities where it is used as a fire suppressantand for controlling any vapors released from anaccidental LNG spill. Blanketing such spills with

HIGH EXPANSION FOAM

SYSTEMS

Hi-Ex Foam is an effective method to help reduceand control fire intensity and to decrease LNGvapor generation.

METHOD OF OPERATION

High Expansion Foam concentrate and water aremixed in the correct proportion by variousmethods to form a foam solution. This solutionflows to the Hi-Ex generator where it isdischarged through nozzles onto a fine mesh

screen. A rotating fan, driven by the incomingfoam solution, is incorporated into the generator.This fan forces large volumes of air through thefine mesh screen at the same time as the foamsolution is sprayed onto it. The air mixes with thefoam solution to form a large discharging mass ofstable bubbles at a rate of up to 1,000 gallons ofexpanded foam for each gallon of foam solution.This clean highly expanded foam mass quicklyfills large areas flowing around obstacles andflooding every void quickly and effectivelysmothering any fire.

METHOD OF EXTINGUISHMENT

When the Hi-Ex foam is discharged into a firecompartment, three extinguishing mechanismshappen.

• The large mass of the discharging foam fills allvoids and seals the area involved in the fireand prevents fresh air from reaching the baseof the flames. The foam mass maintains anoxygen deficient area until the fire isextinguished.

• The steam generated is a result of the radiantheat from the fire evaporating the water in thefoam blanket. This conversion to steamabsorbs a large quantity of heat and theresulting steam-air mixture is well below theoxygen level that is required to supportcontinued combustion.

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• The cooling effect of the Hi-Ex foam occurs asthe bubbles break and release water onto anyhot surfaces. The surface tension of the drain-ing water is lowered and the cooling andwetting effect of the draining water penetratesany Class A type materials more rapidly than

water. This cools the burning material tobelow its ignition temperature.

INSTALLATION

The installation of the Hi-Ex Generator systemcomponents should be located and arranged sothat any recharging, inspection, testing or generalmaintenance will cause a minimum disruption tothe fire protection system. The Hi-Ex generators

may be installed in either a vertical or a horizontalposition.

When mounting the generator in a fixed location,care should be taken so as not to distort the cylin-der section of the generator housing as this couldinterfere with the rotation of the fan/motor assem-bly. The generator should be supported from thebottom not the top and both the front and the rear.It is imperative that the generator be firmly bracedto ensure there is no flex or movement when thesystem is in operation.

PIPING MATERIALS

304, 316 stainless and schedule 40 black steelpipe are suitable for use with foam solutions. Theschedule 40 pipe is not recommended for use withfoam concentrates unless the pipe is kept floodedat all times. The stainless steel pipe is suitable foruse with the foam concentrates at all times.Galvanized pipe cannot be used with foamconcentrate. Galvanized pipe is suitable for use

with foam solution only.

It is recommended that where threaded pipe jointsetc. are in contact with the foam concentrate orthe foam solution, a quality TeflonTM  based pipe

 joining compound and a quality TeflonTM  tape inaccordance with MIL-T-27730 are both used toensure leak tight screw fittings.

DESIGN INFORMATION

TOTAL FLOODING SYSTEMS

A total flood system is a fixed foam fire protectionsystem consisting of the Hi-Ex generator(s),proportioning system, foam concentrate, watersupply and necessary interconnecting piping. Thistype system is designed to discharge theexpanded foam into an enclosed space or aroundthe hazard. The total flood system is suitable foruse where there is a permanent enclosure aroundthe hazard that is capable of holding the requiredamount of foam for the designed duration.

For adequate protection there should be sufficientfoam concentrate to allow the system a dischargerate sufficient to cover the hazard to an effective

depth before any unacceptable damage occurs.

The minimum total depth of foam is to be not lessthan 1.1 times the height of the highest hazardbeing protected but in no case can it be less than2 ft. above that hazard.

Submergence time for Hi-Ex foam varies with thetype of building construction and whether thebuilding does or does not have a sprinkler system.

Fig. 25 provides maximum submergence times inminutes for high expansion foam measured from

the start of foam discharge. The chart does notinclude submergence times when used on watermiscible/polar solvent type fuels or flammableliquids having a boiling point less than 100oF(38oC). These products may require higherapplication rates. Please check with the engi-neering department at Chemguard for Applicationguidelines. When used in tire storage areas, thesubmergence time shown reflects the area alsohaving sprinkler protection. When certaincombustible products are stored 15 feet or higher,fire spread may still be rapid and the dischargetimes in the submergence chart may not be

suitable. A faster submergence time may bemore appropriate.

The foam discharge rate is to be sufficient tosatisfy the foam depth requirements and submer-gence times allowing compensation for normalfoam shrinkage, foam leakage and breakdowneffects of any sprinkler discharge.

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The factor for compensation for normal foamshrinkage is 1.15.

The factor for compensation for loss of foam dueto leakage around doors, windows and throughunclosable openings is determined by the designengineer after proper evaluation of the structure.This factor cannot be less than 1.0. Dependingon foam expansion ratio, sprinkler operation andfoam depth, this factor may be as high as 1.2 fora building with all openings normally closed.

The factor (Rs) for compensation of breakdown bysprinkler discharge is determined by the followingformula or by test.

  Rs = S x Q where:

  S = Foam breakdown in cfm per gpm of  sprinkler discharge. S is to be 10 cfm /   gpm ( 0.748 cu m / min. / L / min. )  Q = Estimated total discharge from maximum  number of sprinklers expected to operate  - gpm ( L / min. )

The following is the formula for calculating theminimum rate of foam discharge or total generatorcapacity allowing for compensation of normalfoam shrinkage, foam leakage and breakdowneffects of sprinkler discharge.

  R = ( V/T + Rs ) x Cn x Cl where:

  R = rate of discharge - cfm ( cubic meters  per min. )  V = submergence volume - cubic feet ( M

3 )

  T = submergence time - minutes  Rs = rate of foam breakdown by sprinklers  - cfm ( M

3 / min. )

  Cn = compensation for normal foam shrinkage  Cl = compensation for leakage

All openings such as doorways, windows, etc.

below the design filling depth shall closeautomatically before or during foam dischargewhen the system is activated.

Discharge duration: There shall be sufficient highexpansion foam concentrate and water to allowcontinuous operation of the system at the designdensity for 25 minutes OR generate 4 times thesubmergence volume.

The following is a typical High Expansion FoamSystem for an unsprinkled building.

Building - Light steel, not sprinkled,100 ft. x 30 ft. x 10 ft.

Products Stored - Low density combustibles 7 ft.in height.

Cubic area to be protected -100 x 30 x 9(2 ft. above height of combustibles) = 27,000 cu. ft.

Fill Time - Per NFPA 11A, 3 min.

Formula for system without sprinklers

R = (  V/T ) x Cn x Cl

V = 27,000 cubic feet

T = 3 minutes

Cn = 1.15

Cl = 1.1 ( slight leakage )

R = ( 9,000 ) x 1.15 x 1.1 = 11,385 cfm

11,385 cfm is required for the above building.

EQUIPMENT LIST

1 x Model 12,000 High Expansion Foam Genera-tor. 12,000 CFM / 59 psi / 170 gpm

1 x 3" Between flange style, Ratio Controller, Flowrange 70 - 750 gpm.

1 x 50 Gallon vertical style bladder tank.(170 gpm x .02 - 3.4 gpm of Xtra Hi High expansion foam concentrate

(2% mix ratio) x 15 min. = 51 gallons of foam concentrate)

55 x Gallons Xtra Hi High expansion foam concentrate  (51 gallons system fill, 4 gallons system test).

Plus miscellaneous swing check and ball valves.

LOCAL APPLICATION SYSTEM

This type of system consists of a fixed foamgenerating device complete with the necessarypiping and foam concentrate proportioning

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equipment. The system is designed to protect aspecific piece of equipment or discharge directlyonto a potential hazard area. Local applicationsystems can be used to protect hazards locatedindoor, outdoor or in partly sheltered areas.When used outdoors or in partly sheltered areas,

provisions should be made to compensate for theeffects of wind or other climatic conditions.

FIG. 25

MAXIMUM SUBMERGENCE TIME (MINUTES) FOR HIGH EXPANSIONFOAM MEASURED FROM START OF ACTUAL FOAM DISCHARGE

Heavy or ProtectedLight or Unprotected or Fire-Resistive

Steel Construction ConstructionHazard  _______________________________________________ 

Not NotSprinklered Sprinklered Sprinklered Sprinklered

 ______________________________________________________________________________________ 

Flammable liquids [flash points below 100oF (38oC)]having a vapor pressure not exceeding 40 psia(276 kPa)** 3 2 5 3

Combustible liquids [flash points of 100oF (38oC)and above]** 4 3 5 3

Low density combustibles (i.e., foam rubber, foamplastics, rolled tissue, or crepe paper) 4 3 6 4

High density combustibles (i.e., rolled paper kraftor coated banded) 7 5 8 6

High density combustibles (i.e., rolled paper kraftor coated unbanded) 5 4 6 5

Rubber tires 7 5 8 6

Combustibles in cartons, bags, fiber drums 7 5 8 6

 ______________________________________________________________________________________ 

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