The water supply shall be evaluated to determine if surge suppressors will be
necessary to prevent damage from water hammer.
Provide double basket duplex or wye strainer(s) for the AFFF system. The type of
strainer and location of the strainer(s) will be determined by the NAVFAC cognizant Fire
Protection Engineer. Strainer baskets shall be stainless steel with a mesh size no greater than 1/16
-inch (1.59 mm).
The flow switch (pressure switch) for the overhead sprinkler system in the aircraft
storage and service area shall not cause the low-level fire suppression system to activate.
The control panel for the building fire alarm and releasing panel for the AFFF shall be
combined only if more than 75% of the detection devices in the building are for the AFFF
Provide separate power disconnects for the fire pumps and foam pumps (if foam
pumps are provided).
LOW-LEVEL FIRE SUPPRESSION SYSTEM
Provide a low-level AFFF system utilizing the Viking Grate NozzleTM, Model GN 200
or equivalent that is acceptable to NAVFAC's Chief Fire Protection Engineer for this use. The
nozzles shall be located in the trench drains with spacing between nozzles not exceeding 25-foot
intervals (7.6 m). The distances between grate nozzles and hangar door openings shall be
20 feet (6.1 m). The distances between grate nozzles and walls that separate aircraft
storage/servicing area from administrative, shop or similar occupied areas of the hangar shall be
20 feet (6.1 m). These distances are intended to minimize the amount of foam
discharged beyond the trenches.
Provide a supply of 3% AFFF concentrate meeting Military Specification MIL-F-
24385F, Fire Extinguishing Agent, Aqueous Film-Forming Foam (AFFF) Liquid Concentrate,
for Fresh and Seawater, to support a 10-minute discharge at the water flow rate based on the
supply calculation method and 3.9% concentration.
The grate nozzle pressure shall be maintained at 40 psig to 45 psig (275 kPa to 310
kPa) for all nozzles. The use of flow control valves for this application is required. The flow
control valves shall be equipped with the automatic re-closing feature and speed control settings.
The AFFF delivery time from time of detection to discharge from the most remote
nozzle shall not exceed 30 seconds.
The foam proportioner shall be provided with a by-pass in order to facilitate flushing
of the system (see Figure 3).
Each foam proportioner shall be provided with a test connection (see Figure 3) to
allow for the connection of hose lines in order to test the foam proportioners. Provide a
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19 January 2005