MIL-DTL-62265C(AT)
element is obtained. Subsequent to the test, the filter element shall be inspected for indications of
collapse and subjected to and pass the bubble point test of 4.9.1.2. The bubble point value
obtained shall not be less than the minimum value established during hydraulic fluid preproduction
or initial production testing.
4.9.8 Flow fatigue test. The assembly shall be blocked and the temperature of the
hydraulic fluid shall be 275°F minimum. The assembly shall be subjected to pressure flow cycles
with the fluid flow being increased to a minimum of 30 percent of rated flow, and then shall be
decreased to zero flow to complete one cycle. A cycle shall consist of increasing the differential
pressure across the assembly from zero the maximum specified and back to zero by first
increasing and then decreasing the flow through the filter element. The filter element shall be
progressively loaded with fine dust (AC), or equivalent, to raise the differential pressure
(pressure drop) as specified in table V. Peak pressure shall be reached within 25 percent of the
cycle and held for at least 50 percent of the cycle. The cycling rate shall be 100 cpm maximum
and the number of cycles at each differential pressure shall be in accordance with table V. Upon
completion of this test, the filter element shall be bubble point tested in accordance with 4.9.1.2.
The value obtained shall not be less than the minimum value established during hydraulic fluid
preproduction or initial production testing as in 4.9.1.2.
4.9.9 Relief valve testing (see 3.4.9).
4.9.9.1 Cracking pressure determination. The filter element media shall be blocked and
the assembly installed in a suitable housing. Pressure shall be applied to the inlet port of the filter
housing beginning with a pressure of 40 psi and increasing in increments of 20 psi, or less, until
cracking pressure of the relief valve in the assembly being tested is reached. At each increment,
the pressure shall remain constant for 5 minutes. At each pressure increment, valve opening shall
not be considered until the beginning of the third minute. The leakage rate during the last
3 minutes of each pressure increment shall be noted. Cracking pressure shall be considered as the
pressure at which the leakage rate through the relief valve amounts to the value specified in
table VI.
4.9.9.2 Flow capacity determination. This test shall be conducted in conjunction with
4.9.9.1. Pressure shall be increased beyond the cracking pressure, until the flow rate of table VI
through the relief valve is obtained. A pressure differential between the inlet and outlet ports shall
not exceed the pressure specified in table VI.
4.9.9.3 Reseat pressure determination. This test shall be conducted in conjunction with
4.9.9.1. The pressure shall be reduced in 10 psi increments until leakage through the relief valve
does not exceed the rate specified in table VI. The resulting pressure shall be considered the relief
valve reseating pressure and shall occur at a pressure of not less than that specified in table VI.
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