MIL-PRF-87260B(USAF)
and two each shall be identified for the fuel retention test specified herein and the water
retention test specified in 4.5.10.2. A porosity test specimen shall be taken directly above and
below the retention specimen and tested per 4.5.4. All retention and porosity (air pressure
drop) specimens shall be properly labeled on the top surface and submitted to the coordinating
activity. One fuel retention specimen from each of the three test locations shall be tested in
accordance with the following procedure, and all applicable data shall be recorded:
a. The specimen shall be preconditioned at a temperature of 72 ±5°F for a minimum of
30 minutes, weighed to the nearest 0.1 gram, and the dimensions measured in accordance with
ASTM D3574. The test fluid shall be pre-filtered through an 0.8-micron filter as specified in
4.5.14 and then adequately preconditioned at the test temperature. Just prior to use, the fluid
shall be tested for specific gravity (density) and temperature.
b. The retention test apparatus shall be sized to approximately 7 inches x 7 inches x 10
inches and shall have a means of draining the fuel from the bottom at the rate of 500 ±50 cubic
centimeters/minute. The draining drop rate in this particular apparatus should approximate 0.5
inch per minute. The test fluid shall be charged into the container to a level that corresponds to
approximately 0.5 inch above the top of the specimen.
c. The specimen shall then be slowly placed into the container such that the specimen is
oriented in the direction of rise (bun height) and supported off the bottom of the container by two
glass rods and spaced 0.5 inch from all sides of the container. Fuel shall then be drained at the
prescribed rate until flow ceases and the specimen is then allowed to drain in this position for an
additional 2 minutes.
d. The specimen shall then be carefully removed from the container and weighed to the
nearest 0.1 gram. Care should be taken not to spill the fluid from the bottom surface of the
specimen when removing from the test rig. Using the specimen weights before and after fluid-
wetting in grams, specimen volume in cubic centimeters, and fuel density in grams per cubic
centimeter, the percent volume retention shall be calculated as follows:
( w et sp ecim en w eig h t - d r y sp ecim en w eig h t ) X 1 0 0
Per cen t r et en t ion =
sp ecim en v olu m e X d en sit y of f u el
e. All values, including test fluid temperature and porosity values (top/bottom) shall be
reported. The above procedure shall then be repeated, using the same specimens, and report
results.
4.5.10.2 Water retention test.
Using one unused water retention specimen specified in 4.5.10.1, the volume percent retention
shall be determined using the same procedure. This shall be repeated for at least one other
porosity location. The test fluid shall be unused distilled water that has been tested for
temperature and density just prior to use. CAUTION: Do not run more than two tests per batch
of water.
4.5.10.3 Test data and sample requirements.
Report test data on all samples tested including the air pressure drop of the specimens directly
above and below the retention samples. A minimum of three specimens from various locations
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