systems utilizing microcomputer, minicomputer, or programmable logic
controllers.
2.2
DESIGN OF FOAM SYSTEMS
Design of fuel tank fire extinguishing foam systems shall be by hydraulic
calculations for uniform distribution of AFFF solution over the protected
area and shall conform to the NFPA standards listed above and to the
requirements as specified herein.
2.2.1
Tankside Foam Chambers
Provide chamber(s) as required by NFPA 11. Provide each chamber with a
manufacturer-approved diaphragm or rupture disk to prevent entrance of fuel
vapors into system piping. Upon discharge of AFFF, diaphragm or disk shall
rupture, allowing foam to flow into the tank. Chamber shall be
air-aspirating type with screened air intake and hinged or removable
inspection cover. [Rupture disk or diaphragm is not required for open top,
floating roof tanks].
2.2.2
Deluge Valves
Valves shall be operated by a detection system listed for releasing service
and independent of the fire alarm system. [Deluge valve clappers shall
incorporate a latching mechanism that will not be affected by changes of
pressure in the water system.] If 150 mm 6 inch valves are used in 200 mm
8 inch risers, provide smoothly tapered connections. In addition to
automatic operation, arrange each valve for manual release at the valve.
Provide pressure gages and other appurtenances at the deluge valves as
required by NFPA 13. Provide a detection device at the end of each
actuation circuit to test the circuit and mount the device between 1.80 and
2.40 meters 6 and 8 feet above the finish floor or grade. Label each
testing device to indicate the valve it activates. [Provide remote manual
releases [at [_____]] [where shown].]
2.2.3
AFFF Solution Distribution
Distribution shall be essentially uniform from all foam chambers on any
single tank.
2.2.4
AFFF Solution Application Density
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NOTE: Refer to MIL-HDBK-1008 and NFPA 11 governing
the particular hazard to determine the density
required.
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Size system to provide the specified density when the system is discharging
the specified total maximum required flow. Application to tanks being
protected shall be [_____] mL/sec per sq meter gallons per minute (gpm) per
square foot over the discharge area [with foam hose stream requirements of
[_____] mL/sec gpm] [, and with outside water hose stream [and monitor
nozzle] requirements of [_____] mL/sec gpm].
2.2.5
Foam Chamber Discharge Area
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NOTE: Select first bracketed option for fixed roof
SECTION 13957N
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