MIL-DTL-432H
4.4.4 Low temperature compression set test. Low temperature compression
set shall be determined in accordance with ASTM D 1229. The specimens shall
be compressed 40 percent and exposure time shall be 94 ± 1/2 hour at -40°F
(-40°C). Readings shall be taken after the 30-minute recovery period.
4.4.4.1 Torsional modulus ratio (material for type III gaskets). The
torsional modulus ratio shall be determined in accordance with ASTM D 1053.
The material to be used for type III, class 1 gaskets shall be tested at
-40° ± 2°F (-40° ± 2°C). The material to be used for type III, class 2
gaskets shall be tested at -60° ± 2°F (-51° ± 2°C). The liquid coolant
shall be methyl alcohol, and exposure time shall be five minutes.
4.4.4.2 Torsional modulus ratio after solvent extraction (material for
type III gaskets). The gasket material shall be immersed in Reference Fuel
B, ASTM D 471, for 24 ± 1/4 hours at 73° ± 5°F (22.7° ± 1.6°C). The
extracted sample shall then be removed from Fuel B, placed on a wire screen
and dried with forced air for 24 ± 1/4 hours at 73° ± 5°F (22.7° ± 1.6°C).
The torsional modulus ratio shall be determined as specified in 4.4.4.1.
4.4.4.3 Low temperature compression set test (type III gaskets). The low
temperature compression set shall be determined in accordance with ASTM D
1229. The type III, class 1 gasket sample shall be compressed 40 percent and
exposure time shall be 94 ± 1/2 hours at -40° ± 2°F (-40° ± 2°C). The type
III, class 2 gasket sample shall be compressed 40 percent and the exposure
time shall be 94 ± 1/2 hours at 60° ± 2°F (-51° ± 2°C). Readings shall be
taken after the 30-minute recovery period.
4.4.4.4 Low temperature compression set after solvent extraction test
(type III gaskets). The gasket shall be immersed in Reference Fuel B, ASTM D
471, for 24 ± 1/4 hours at 73° ± 5°F (22.7° ± 1.6°C). The sample shall then
be removed from Fuel B, placed on a wire screen and dried with forced air
for 24 ± 1/4 hours at 73º± 5ºF (22.7º± 1.6ºC). The low temperature
compression set shall be determined according to 4.4.4.3.
4.4.5 Compression set test. The compression set test shall be performed in
accordance with ASTM D 395, method B, except that the sample specimen
thickness shall be the actual thickness of the gasket. Spacer bars shall be
the thickness required to compress the gasket 25 ± 3 percent of the original
gasket thickness. The test specimen shall be held compressed for 22 hours at
158º ± 2ºF (70º± .9ºC).
4.4.6 Endurance test (except type VII). A closure flange shall be
thoroughly wetted with the special testing fuel specified in 4.5.2, a gasket
placed on it, and a plug inserted. The plug shall be tightened to the torque
shown in table V with a torque wrench and loosened 30 times. An interval of
6 to 7 seconds shall be allowed between each tightening and loosening. The
plug shall then be tightened once more with a torque equal to 2-1/2 times
that indicated in table V.
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