MIL-DTL-24630A(SH)
4.5.1.3 Interchangeability. The internal parts of both valves shall be interchanged and the valves shall then be
reassembled and each shall be mechanically opened three times and visually examined to ensure the valve closes
after each opening. If the valves fail to conform to the examination or the interchangeability requirement of 3.6, the
valves shall be rejected and no further testing shall be conducted. If, in order to fabricate specimens with adverse
tolerances, a part is made outside tolerances, the interchangeability test of that part shall be waived. The internal
components shall then be reassembled in the original valve bodies as received.
4.5.1.4 Maintainability demonstration. The maintainability requirements specified in 3.4.3.2 shall be
demonstrated. The demonstration shall include MTTR and ease of disassembly/assembly. Failure to comply with
any or all of the specified requirements shall result in rejection.
4.6 Tests.
4.6.1 Pressure drop at rated flow. Pressure drop through the check valve shall be measured at a flow equal to
the rated flow capacity. The fluid flow shall be accurately maintained. A manometer connected across the check
valve may be used for accurate measurement of the pressure drop. The pressure drop through the valve shall not
exceed the values specified on the applicable specification sheet. The valve shall not exhibit surging or chattering
on the seat during this test.
4.6.2 Proof pressure.
4.6.2.1 Proof pressure (qualification). A proof pressure of 4,500 lb/in² shall be applied in both the free- and
reverse-flow directions at least two successive times in each direction and held for 2 minutes for each pressure
application. For the reverse-flow direction, the valve shall be opened mechanically between applications of the
proof pressure. There shall be no measurable external leakage, failure, or permanent set.
4.6.2.2 Proof pressure (acceptance). The proof pressure of 4,500 lb/in² shall be applied in both the free- and
reverse-flow directions and held 2 minutes for each pressure application. For the reverse-flow direction, the valve
shall be opened mechanically between applications of the test pressure. There shall be no evidence of external
leakage, failure, or permanent set.
4.6.3 Leakage.
4.6.3.1 Leakage (qualification). This test shall be performed with the valve in the horizontal position and
repeated with the valve held in the vertical position as specified in 4.4.3. The valve shall be tested for internal
leakage by applying the pressures listed in table I. The pressure shall be applied in the direction of reverse-flow, and
the valve shall be mechanically opened between pressure applications. The leakage measurement period shall be at
least 3 minutes but not more than 10 minutes in duration and shall begin within 1 minute after application of the
required pressure. The internal leakage shall not exceed the amount shown in table I with a fluid at a temperature
which results in a viscosity of 50 cSt or less at atmospheric pressure. There shall be no external leakage during this
test.
4.6.3.2 Leakage (acceptance). This test may be performed with the valve in any position. The valve shall be
tested for internal leakage by applying pressures of 5 and 3,000 lb/in² in the reverse-flow direction. The valve shall
be opened mechanically between pressure applications. The leakage measurement period shall begin with 1 to
3 minutes of pressure application. The internal leakage shall not exceed the amounts shown in table I with a fluid at
a temperature which results in a viscosity of 50 cSt or less at atmospheric pressure. There shall be no external
leakage during this test.
4.6.4 Operational test. Operational tests shall consist of checking time and cracking pressure tests. These tests
shall be conducted within a temperature range required to maintain fluid viscosity at 100 cSt. When included as part
of another test, the temperature describing such test shall apply.
4.6.4.1 Checking time. The valve shall be in the vertical position defined in 4.4.3. The valve shall be
mechanically actuated to the full-open position against a static fluid head of 5 lb/in² maximum applied in the
reverse-flow direction; it shall then be allowed to check before the static head of fluid decreases to 1 lb/in²
minimum. The time between the release of the closing mechanism and the cessation of fluid flow shall be the
checking time and shall not exceed 1½ seconds.
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