MIL-DTL-23953D(SH)
4.4.8 Poppet seat test. The valve shall be filled with water. Water shall flow through valve until all air has
been completely bled from valve before valve is checked for leakage. Water pressure shall be applied to the outlet
port and leakage shall be checked at the inlet port at 5 psig, 25 psig, 100 psig, 600 psig, 900 psig, and 4,500 psig.
Pressure shall be held at each increment for 3 minutes to allow the unit to stabilize before checking for leakage. The
inlet port shall be observed for leakage for 5 minutes at each increment. No leakage shall be allowed. At
completion, the valve shall be examined as specified in 4.4.3.
4.4.9 Low-pressure function test. Air pressure shall be applied to the inlet port of the valve, with a flow meter
connected to the outlet port and open to atmosphere. Pressure on the inlet shall be changed slowly from 0 psig to
50 psig. Cracking pressure of the main poppet shall be verified to be 20 psig maximum. The valve seat shall be
considered cracked when air flow measured at the outlet exceeds 0.1 cubic feet per hour (cfh). Pressure on the inlet
shall be changed slowly from 50 psig to 5 psig. The reseat pressure of the main poppet shall be verified to be 7 psig
minimum. The valve seat shall be considered reseated when air flow measured at the outlet falls below 0.1 cfh.
Pressure on the inlet shall be held for 3 minutes to allow unit to stabilize. Air flow at the vent and leakage at the
outlet shall be checked. No leakage shall be allowed.
4.4.10 External leakage test. With the outlet port capped off, 4,500 psig of air shall be applied to the valve
inlet. Leakage shall be checked using bubble fluid or by submerging the valve in water.
4.4.11 Check feature flow capacity test. The valve shall be connected to a 25 ft³ reservoir. A 2-inch ball valve
shall be installed between the reservoir and the vent-check valve. The piping used shall have an internal diameter of
1¾ inches. The length of piping in the flow capacity test setup shall be as follows: 8 inches between the reservoir
outlet and the ball valve inlet, 24 inches between the ball valve outlet and the vent-check valve inlet, and 24 inches
at the vent-check valve outlet. Initial reservoir pressure shall be between 1,650 and 1,850 psig and initial reservoir
temperature shall be between 70 and 90 °F. Flow shall be initiated through the test valve, and reservoir pressure
versus time shall be plotted with a continuous pressure recorder. The time required for pressure to drop from
1,500 psig to 500 psig shall not exceed that specified in table III.
4.4.12 Vent feature flow capacity test. With the check poppet blocked closed, and the outlet port capped off to
prevent leakage, a blow down test shall be conducted to verify capacity of the vent feature. Vent capacity shall be as
specified in 3.6.3.
4.4.13 Operational test. The vent-check valve shall be flow cycled 5,000 times. The following conditions shall
be produced: during the flow portion of each cycle, pressure at the valve inlet shall be at least 1,300 psig and
pressure at the valve outlet shall not exceed 1,000 psig; during the check portion of each cycle, pressure at the valve
outlet shall exceed the pressure at the valve inlet by at least 600 psig. After 2,500 cycles and again after completion
of 5,000 cycles, the valve shall be tested as specified in 4.4.7 through 4.4.9 and examined as specified in 4.4.3.
4.4.14 Low-temperature operational test. The vent-check valve shall be cycled 1,000 times as specified in
4.4.13, except that the valve shall be maintained at a temperature not exceeding -50 °F during the test. To measure
the temperature of the vent-check valve, a thermocouple shall be placed on the valve body. At the completion of
this test, the valve shall be tested as specified in 4.4.7 through 4.4.9 and examined as specified in 4.4.3.
4.4.15 Low-flow stability test. The valve shall be operated for a minimum of 2 minutes at the flow rate
specified in 3.6.6. Flow shall then be increased to approximately 50 percent of required valve capacity in 100 scfm
increments. Flow shall be held for a minimum of 15 seconds at each increment. There shall be no instability or
cycling during this test.
4.4.16 Valve poppet vent test. The poppet of the vent-check valve shall be tested to verify its integrity under
conditions of rapid depressurization. The valve poppet may either be removed from the valve and placed in a test
chamber, or may be blocked in the open position in the valve for this test. The poppet shall be pressurized to
4,500 psig for not less than 5 minutes. The pressure around the poppet shall then be released to zero psig over a
period of 3 seconds or less. This sequence shall be repeated 12 times. At the completion of 12 cycles, the valve
shall be examined and tested as specified in 4.4.7 through 4.4.9 and 4.4.3. There shall be no damage or degradation
to the seating insert.
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