MIL-DTL-5516D
4.5.5 Endurance tests.
4.5.5.1 Cycling tests of aged ring. The same packings as were used in the performance test
(4.5.5) shall be reinstalled in a test cylinder conforming to figure 5. The cylinder shall be installed
in a test apparatus conforming or equivalent to figure 4 (only the portion of figure 4 deleting
temperature apparatus is applicable to this test). This test machine shall be so constructed that
during the filling stroke of the inboard end of the cylinder (at which time the piston rod is
retracting), the fluid pressure shall be atmospheric or less (5 to 14.7 psi (.034 to .101 Mpa)
absolute pressure). Test conditions shall be as follows:
Oil: Specification MIL-PRF-5606
Temperature: 49° ± 6°C (120° ± 10°F).
Stroke: 4 inch (101.6mm) minimum
Operating pressure: 1,100 to 1,500 psi (7.58 to 10.34 Mpa) driving, and 1,500 psi (10.34
Mpa) minimum loading.
Rate of cycling: 30 cycles per minute minimum, total 70,000 cycles minimum with thick
(nonbreathing) cylinders used.
Standby period: Internal pressure of 1,500 psi (10.34 Mpa) shall be applied statistically for
at least a 17-hour period after every second days' cycling. Standby pressure shall be 5
to 10 psi (.034 to .096 Mpa)during all other periods. In no case, however, shall more
than 10,000 cycles be made between two standby periods
All test data shall be recorded
4.5.5.1.1 Leakage during entire cycling test, including standby, shall not exceed an average of
1cc per 1,000 cycles of operation (approximately 2 drops per 100 cycles) per gland. Leakage
over the last 5,000 cycles of operation shall not exceed 10 cc. The leakage shall be recorded.
4.5.5.2 Cycling tests of new rings. A second set of new packing rings (as molded with no aging)
shall be installed in a life test cylinder in accordance with figure 5, as used in the cycling tests of
aged rings and cycled under identical conditions of pressure, temperature, stroke and speed of
cycling, standby, and total number of cycles, except that the O-ring adapters shall be V-grooves
as noted in figure 5. All test data shall be recorded.
4.5.5.2.1 Leakage of the new rings shall not exceed the rate allowed under endurance cycling of
aged packings. The leakage shall be recorded.
4.5.5.2.2 The right is reserved by the Services to conduct cycling tests on air-aged rings in
rectangular grooves and on oil-aged rings in V-grooves if additional data is considered necessary
by the Services to evaluate the manufacturer's product.
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