MIL-PRF-9050G
is encountered when vibration is applied along any one axis, vibration at each of these resonant
frequencies shall be sustained for the time shown in the applicable portion of the vibration test
schedule. If more than four resonant frequencies are encountered when vibration is applied along
one axis, the four most severe resonant frequencies shall be chosen for test.
4.6.9.2 Cycling test. The valve shall be vibrated in accordance with the vibration test schedule
in table III. The frequency shall be varied between 5 and 500 Hz and then returned to 5 Hz in 15
minute intervals at an applied double amplitude of 0.036 inch or an applied acceleration of
±10.0g, whichever is the lower g value. The rate of change of frequency shall be logarithmic.
TABLE III. Vibration test schedule
Number of resonances
0
1
2
3
4
Total resonance test
-
30
60
90
120
vibration time (min) (see
note)
Cycling test time (hr)
3
2.5
2
1.5
1
Note: 30 minutes at each resonance
4.6.10 Endurance. The inlet pressure of the valve shall be cycled from below the minimum
operating pressure to the maximum operating pressure of the valve and back to below the
minimum operating pressure. The valve shall seat at the end of each cycle when the minimum
operating pressure is reached. This pressure endurance cycling shall be repeated 5,000 times. The
valve shall then be subjected to the leak and capacity tests in 4.6.4 and 4.6.5.
4.6.11 Overpressure cycling. The valve shall be subjected to 25 overpressure cycles. The inlet
pressure of the valve shall be increased to a minimum of 50 psig above the maximum operating
pressure and maintained for at least 10 seconds. The inlet pressure shall then be turned off,
allowing the internal pressure to decrease to the minimum operating pressure at which point the
valve seats. This shall constitute one overpressure cycle. After the 5th, 15th, and 25th cycles, the
leakage rate after the seating shall not exceed 0.01 LPM.
4.6.12 Orientation. The valve shall be subjected to the leak and capacity tests in 4.6.4 and 4.6.5
while the valve is mounted in each of the following orientations:
a. Centerline of the inlet horizontal.
b. Centerline of the inlet vertical and the inlet down.
c. Centerline of the inlet vertical and the inlet up.
4.6.13 Salt fog. Unless waived (see 6.2), the valve, with inlet and outlet plugged, shall be
subjected to the salt fog test in ASTM B117 for 50 hours. There shall be no visible damage to the
valve. The valve shall be subjected to the leakage and capacity tests in 4.6.4 and 4.6.5.
4.6.14 Ozone resistance. Unless waived (see 6.2), samples of elastomer and seating materials
shall be tested in accordance with ASTM D1149. The test samples shall be elongated 20%,
placed in an ozone-free atmosphere for 24 hours, and then subjected to an ozone environment.
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