MIL-PRF-2940D
4.6.3.2 Low temperature. Place the snubber in an environmental chamber
and pressurize the snubber to 250 + 10 psi for a class L snubber and 1500 + 50
psi for a class H snubber. Decrease the chamber temperature from ambient to
40 + 5°F in not less than 1 hour. Adjust the pressure as necessary to
maintain the required pressure. Maintain the pressure and temperature
conditions for not less than 4 hours. Increase the chamber to ambient
temperature in not less than 1 hour. Remove the snubber from the chamber and
allow it to remain at ambient temperature for not less than 1 hour. The
snubber shall meet the requirements of 3.4.3.
4.6.3.3 Temperature cycling. Place the snubber in an environmental
chamber. The snubber shall remain unpressurized during the temperature
cycling. The test shall consist of 4 complete cycles (steps 1 through 4), as
shown in table IV. After completion of the 4th cycle, the snubber shall be
removed from the chamber and allowed to stabilize at ambient conditions for
not less than 1 hour. The snubber shall meet the requirements of 3.4.3.
TABLE IV.
Temperature cycle.
Step
Temperature condition
Duration
1
Increase temperature 1/ from 75 + 5°F
1 hour
to 150 + 5°F
2
Constant temperature of 150 + 5°F
22 hours 3/
3
Decrease temperature to -10 + 5°F
2 hours
4
Constant temperature of -10 + 5°F
22 hours 3/
5
Increasing temperature to 75 + 5°F 2/
1 hour
1/ Ambient temperature for the first cycle.
2/ Ambient temperature for the last cycle.
3/ Minimum duration.
4.6.4 Vibration. The snubber shall be tested in accordance with type I
(environmental) vibration of MIL-STD-167-1 except that the upper frequency
shall be 175 hertz (Hz); the amplitude of vibration shall be as specified in
table V; and for the variable frequency portion, the vibration level shall be
maintained for 2 minutes at every integral value of frequency. If no
resonances are observed, the 2-hour endurance test shall be conducted at 175
Hz. If a particular snubber is determined to be axisymetric, then the
vibration test need only be conducted along the two mutually perpendicular
axes. The snubber shall be pressurized to 250 + 10 psi for a class L snubber
and 1500 + 50 psi for a class H snubber and monitored throughout the test.
The snubber shall meet the requirements of 3.4.4.
TABLE V.
Vibratory displacement criteria.
Frequency range
Table displacement (inches peak to peak)
(Hz)
Exploratory Variable frequency
5
to
20
0.020
+
0.004
0.060
+
0.012
21
to
50
0.010
+
0.002
0.040
+
0.008
51
to
100
0.003
+
0.0006
0.020
+
0.004
101
to
175
0.001
+
0.0002
0.003
+
0.0006
10
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