MIL-DTL-25531F
4.5.3 Lubrication. No lubrication or other servicing of the coupling or mating nipple shall
release tests.
4.5.4 Test nipple. In all tests where a nipple is required, the nipple shall be in accordance with
MS33740.
4.5.5 Ducting. Where ducting is attached to the coupling for test purposes, the hose end fitting
shall conform to MS17833 and the ducting shall conform to MIL-D-22706.
4.6 Test methods.
4.6.1 Examination of product. The coupling shall be examined to determine compliance with
respect to materials, workmanship, dimensions and markings.
4.6.2 Engagement and release. The coupling shall engage a nipple when a maximum force of 25
pounds or a maximum torque of 25 lb.-ft, as applicable, is exerted. The coupling shall release
from the nipple by the secondary method when a force of 10 to 40 pounds is exerted. The
coupling shall disconnect from the nipple when the lanyard release is pulled with a force of 10 to
40 pounds within a minimum cone angle of 30 degrees.
4.6.3 Pressure. The coupling, mounted on a test nipple, shall be pressure tested at the pressures
listed below. Each pressure shall be held for 5 minutes. Leakage shall not exceed 1 pound per
minute (pm). The coupling shall be capable of normal operation after completion of this test.
a. Operating pressure - 112 psia at 600°F
b. Proof pressure - 200 psia at 600°F.
4.6.4 Pressure drop. Pressure drop through the coupling, when attached to the nipple, shall not
exceed 0.9 psi when 450°F air is supplied at 55 psi static pressure and 120 pm flow.
4.6.5 Temperature operation. The coupling shall be engaged and disengaged with a nipple at the
following temperatures. Failure to successfully engage and disengage a total of five consecutive
times for each temperature condition shall be cause for rejection.
a. Nipple and coupling at -65°F
b. Nipple at -65°F and the coupling at +600°F internal surface temperature
c. Nipple at 400°F and coupling at 600°F internal surface temperature.
4.6.6 Drop tests. The coupling, while attached to ducting, shall be engaged with a nipple
mounted in a horizontal position 6 feet above a concrete surface as measured from the centerline
of the nipple. The internal surface temperature of the coupling shall be raised to 600°F. The
coupling shall be disconnected by the handling ring or by tripping the lanyard release and
allowing it to fall on the concrete surface. This cycle shall be repeated 125 times with the
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