MIL-PRF-87260B(USAF)
d. Minimum instrumentation shall include: pressure rise, combustion temperature
indication, and visual, photographic, or photocell indication of flame penetration downstream of
arrestor.
e. Combustion relief area shall be 80.0 percent of cross-sectional area or greater. The
material used for the testing shall be taken from a given bun that has been sufficiently tested to
establish its air pressure drop (porosity) and density characteristics. The material shall always
be oriented in the test apparatus to permit flame penetration in the direction of porosity testing
(direction of rise or bun height).
f. Where practical, the material used shall be in the lower half of the air pressure drop
range. For example: Grade I shall be between 0.150 and 0.200 inch of water and Grade II shall
be between 0.260 and 0.310 inch of water.
4.5.18.1 Material sizing.
The material shall always be slightly oversized, 2.0 percent maximum, when installed and
restraints used to avoid arrestor movement during testing. The combustible mixture on each
test shall be verified by bomb sampling and shall meet the following minimum criteria for
pressure rise:
Pmin = (8P0) x 0.7, where P0 = initial pressure of system in psia
The following definitions shall apply (see FIGURE 3).
psid = differential pressure rise starting point maximum overpressure point during the
combustion process.
Va = arrestor volume
Vc = combustion (ignition volume)
Vr = relief volume = Va + Vv
Vt = total volume of apparatus = Vc + Vr
Vv = void volume downstream of arrestor
Tm = minimum arrestor thickness required to prevent flame propagation Vc to Vv
4.5.18.2 Additional tests.
The following testing shall be conducted and all data shall be reported for each test condition
(see FIGURE 3 for typical flame arrestor orientation).
25
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business