MIL-PRF-25675C
4.6.3
Surge flow. The valve shall be disassembled and inspected for cracks, bulges, gouges, and other deformations
and then reassembled. Pressure shall be applied to the valve and the valve pressure stabilized at 3,000 psi.
Twenty-five flow cycles shall be applied to the valve. After completion of the 25 flow cycles, the valve again shall be
disassembled. Any evidence of damage or deformation is a cause for rejection.
4.6.4
Leakage. The valve shall be held in both the horizontal and vertical positions and a reverse-flow pressure
shall be applied to the valve for 30 minutes in each position. The leakage measurement period shall begin 2 minutes
after pressure is applied, and the internal leakage shall not exceed the amounts indicated in Table I. Any evidence of
external leakage throughout the pressure range, except a slight wetting at the seals insufficient to form a drop, is a
cause for rejection.
4.6.5
Vertical leakage. The valve shall be held in the vertical position. Each pressure specified in Table I shall be
applied in the reverse-flow direction for 5 minutes. The valve poppet shall be unseated between each pressure
application. In each case, the leakage measurement period shall consist of the last 3 minutes of the 5-minute period.
The rate of internal leakage shall not exceed the amounts specified in Table I. Any evidence of external leakage
throughout the pressure range, other than a slight wetting at the seals insufficient to form a drop, is a cause for
rejection.
4.6.6
Checking time. The valve shall be held in the vertical position and the valve poppet shall be mechanically
actuated to its full open position against a test fluid static head of 5 psi. The valve then shall be allowed to check
before the test fluid static head decreases to 1 psi. The checking time shall not exceed 1.5 seconds.
4.6.7
Cracking pressure. Pressure shall be applied gradually at the valve inlet in the free-flow direction beginning
at 0 psi. Cracking pressure shall be between 2 and 8 psi.
4.6.8
Pressure drop. The valve shall be installed at a distance of 4-tube diameters downstream from a piezometer
pressure pickup and a distance of 15-tube diameters upstream from the return pressure pickup. Pressure drop through
the valve shall be measured at the rated flow. The temperature of the test fluid shall be maintained at 100° ± 5°F. The
pressure drop through the valve shall not exceed 15 psi.
4.6.9
Low temperature. The valve shall be connected to a test fluid static head of 1 to 3 feet in the reverse-flow
direction. If the valve contains nonmetallic parts other than static seals, the valve shall be maintained at a temperature
not warmer than -65°F for 72 hours. If all parts of the valve except static seals are metallic, this period shall be
reduced to 24 hours. After this period, the poppet shall be actuated mechanically at least twice. At the end of this test,
the valve shall be subjected to tests specified in 4.6.5 through 4.6.8.
4.6.10 Intermediate temperature. The valve shall be actuated by reverse-flow pressure at increments of 40°F to
demonstrate that the valve operates satisfactorily across the test fluid temperature range of -65°F to 450°F.
4.6.11 High temperature. With the temperature of the valve maintained at 450° ± 10°F, a test fluid static head of 1
to 3 feet on the valve, and the valve in the reverse-flow direction, the poppet shall be actuated mechanically at least
twice. At the end of this test, the valve shall be subjected to tests specified in 4.6.5 through 4.6.8.
4.6.12 Endurance. While maintaining temperature of the test fluid at 450° ± 10°F, the valve shall be subjected to
50,000 impulse cycles at the rate of 30 to 100 cpm. During the 50,000 cycles, the peak pressure during pressure
application in each cycle shall be 4,500 ± 150 psi. Upon completion of the cycling, tests in 4.6.4, 4.6.6, and 4.6.7
shall be conducted. The temperature of the test fluid and valve shall then be lowered to -65°F and the valve soaked for
5 hours. The valve again shall be subjected to tests in 4.6.4, 4.6.6, and 4.6.7.
4.6.13 Burst pressure. With the outlet port plugged and temperature of the test fluid at 450° ± 10°F, pressure shall
be applied in the free-flowing direction at a maximum rate of 25,000 psi per minute until 7,500 psi is reached. The
valve shall withstand 2 minutes at 7,500 psi. The valve shall neither rupture nor leak externally.
6
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business