MIL-PRF-23256C
4.5.11.1 General. The vibration tests specified herein shall be performed in each of three
mutually perpendicular axes in the order listed below (see 4.5.11.2 to 4.5.11.5). All testing shall
be performed in one axis prior to testing in the next axis. The seal valve assembly shall be
checked for proper operation after each test (see 3.5.4).
4.5.11.2 Seal valve assembly operation. The seal valve assembly shall be mated to the test
fixtures (see 4.4.4), with the control valve closed. While subjected to vibration, the inlet of the
seal valve assembly shall be pressurized to 3,000 ±100 psig. After each axis of vibration is
completed, the seal valve assembly shall be visually inspected and shall meet the requirements
specified in 3.5.11. The seal valve assembly shall then be subjected to and shall meet the
requirements of the leakage and operating pressure tests (see 4.5.3 and 4.5.4).
4.5.11.3 Mounting techniques. The seal valve assembly shall be attached to the vibration
exciter table by means of the fixture described in 4.4.4. The control valve shall be closed. The
vibration input shall be measured on the fixture at a point adjacent to the mounting point of the
seal valve.
4.5.11.4 Sinusoidal test level. The seal valve assembly shall be subjected to sinusoidal
vibration along each of three mutually perpendicular axes. The frequency shall be ±2 percent and
the amplitude shall be ±5 percent. The test shall consist of sweeping for 60 minutes in each axis
from 5 to 2,000 Hz at one octave per minute in accordance with table V.
TABLE V. Sinusoidal test level.
Frequency
Displacement or acceleration
5 - 20 Hz
0.100 inch 1/
20 - 33 Hz
±2.0 g's
33 - 74 Hz
0.036 inch 1/
74 - 2,000 Hz
±10.0 g's
1/ = Double amplitude
4.5.11.5 Random test level. The seal valve assembly shall be subjected to a random
vibration along each of three mutually perpendicular axes. The instantaneous random vibration
acceleration peaks shall be limited to three times the root mean square (rms) acceleration level.
The power spectral density (PSD) of the test control signal shall not deviate from the specified
requirements by more than +100,-50 percent (±3 dB) between 20 Hz and 2,000 Hz, except that
deviations as large as +300,-75 percent (±6 dB) shall be allowed over a cumulative bandwidth of
100 Hz, maximum, between 500 and 2,000 Hz.
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