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12870 Lpm (300-3400 gpm). In consideration of the limited number of manufacturers, prudent
design requires basing the design on the one with the more limited nominal flow range.
10.2.5.3.3 Proportioner Size. Determine required proportioner size based upon detailed
hydraulic calculations because flow rates above or below the manufacturers' specified nominal
flow range are apt to result in the foam solution being too lean or too rich. The resulting foam
solution can lack the necessary qualities to produce effective fire fighting foam. Therefore, assure
that design utilizes proportioners of the size capable of proportioning for the calculated foam-
water demand for the system or systems involved. With few exceptions, a 150 mm (6-in)
proportioner will be appropriate for sprinkler system applications.
10.2.5.3.4 Test Header. Provide a test header for handling test flows of foam solution. The test
header connection must be downstream of each proportioner and must permit flowing foam
solution through the proportioner at various flow rates. Concurrent with flowing foam solution,
samples of solution are taken and analyzed to verify that the minimum concentration level of 3%
concentrate by volume is being produced by the proportioner. Size the test connection to
accommodate the largest anticipated test flow, which will be the design flow in most cases. For
most applications, particularly those with 150 mm (6-in) proportioners, a test header with four 65
mm (2-1/2-in) hose valves will be adequate. For sprinkler systems, provide an OS&Y gate valve
for the test connection as well as one for system isolation. (Refer to NFPA 16A, Figure A-6.1).
Do not provide a flow meter similar to those used for fire pump applications unless specifically
required by applicable design criteria.
10.3 Foam-Water Sprinkler Systems.
10.3.1 System Type. With few exceptions, automatic sprinkler systems provided in DoD aircraft
storage and servicing areas will be of the closed-head, foam-water type. Where the threat of
freezing is minimal or non-existent, wet-pipe systems will be provided. As outlined in applicable
design criteria, preaction systems will be provided where certain climatic conditions exist. Do not
provide supervisory air for preaction sprinkler piping systems even though such is otherwise
required by NFPA 13, Automatic Sprinkler Systems.
10.3.2 Sprinklers. Use standard sprinklers. Do not use air-aspirating foam water sprinklers.
With few exceptions, sprinklers will be nominal 15 mm (1/2-in) orifice. Avoid use of either small
orifice or large orifice sprinklers except such design requirements cannot be achieved otherwise.
Specify sprinklers to be quick response type with 790C (1750F) temperature rating unless
otherwise required by applicable design criteria.
10.3.3 System Size. Configure foam-water sprinkler systems so each covers an area
approximately the same as each other system. Limit the area covered by a single system to less
than 1393 m2 (15,000 ft2).