MIL-DTL-81716A
4.5.2.10 Crush. Nine SAE AS33931, MS3393-16 packings shall be used in this test. Three
shall be unaged, three shall be air aged (see 4.4.2), and three shall be oil aged (see 4.4.3 and
4.4.3.2). The packing shall be tested in a test setup similar to Figure 3. The packings shall each be
twisted (inside out) one-half turn about the cross section and laid between rigid steel plates which
have a surface finish of 40 to 60 microinches (1 to 1.5 micrometers) obtained by sandblasting a
commercial grind finish as suggested in Figure 3. The air-aged packings shall be laid together in
one layer, the oil aged in a second layer and the unaged in a third layer. The stack shall then be
subjected to a constant axial compression load of 16,800 pounds (7630.35 kg), or 5600 pounds
(2540.11 kg) for each packing in a layer (number of layers does not affect the applied load). The
stack shall be left in the compressed state for 68 hours and then each ring shall be removed and
inspected immediately for cracking or disintegration. The packings shall be stored at room
temperature in a free condition and the permanent set of seal cross-section determined at the end
of 20 hours. No cracking or disintegration shall be evident. The cross sectional area of the packing
shall not have been reduced in permanent set more than 25 percent of the "as manufactured" size.
4.5.2.11 Extrusion. Nine SAE AS33931, MS3393-16 packings shall be used for this test.
Three shall be used unaged, three air aged (see 4.4.2), and three oil aged (see 4.4.3 and
4.4.3.1). The nine packings shall be installed one each on SAE AS5169-16 fittings, and the
fittings shall then be installed in AND10050 bosses of applicable size (SAE AS5193-16 boss
fittings may be used). The fittings shall be screwed into the bosses so that an .012 inch feeler
gage can be inserted between the flat boss-face and the adjacent face of the SAE AS5169 fitting
(this allows .012 inch extrusion gap around the test packings). Hydrostatic pressure of 3000 ±
100 psi (20.68 ± .69 MPa) shall be maintained constantly on the inside of the SAE AS5169 fittings
and bosses, and the assemblies shall be maintained at 275 ± 2F (135 ± 1C) for 72 hours.
During this period there shall be no evidence of excessive extrusion of packing or leakage of fluid,
and at the termination of the test the packings shall show no cracking, disintegration or other
failure. The packings may remold to the shape of the confining cavity. A small undeteriorated
ridge at the extrusion point of the packing shall not be considered cause for rejection.
4.5.2.12 Impulse. Standard SAE AS33931 packings in quantities and sizes specified in
Table I shall be used for this test. The unaged packings shall be installed on standard fittings in
accordance with MS21344, sheets 2 and 3, which shall, in turn, be installed in a test fixture as
shown in Figure 4. The test fixture shall be installed in a test set-up similar to Figure 5. Impulse
pressure (see Figure 6) shall be applied at a rate of 35 ± 10 cycles per minute through the range
of 0 to 3000 psi (20.68 MPa) with a peak pressure of 150 percent of 3000 psi (20.68 MPa) at the
start of each pressure cycle for a total of one million cycles. There shall be no leakage at any
time when the packing assembly is subjected to the following schedule (shown graphically on
Figure 7):
(a)
Conduct a static leak check at 5 psi (.03MPa), 3000 psi (20.68 MPa), and 4500 psi
(31.03 MPa).
(b)
50,000 cycles at room temperature, followed by a static pressure leak check at 5 psi
(.03MPa), 3000 psi (20.68 MPa), and 4500 psi (31.03 MPa).
50,000 cycles at 65 ± 5°F (-54 ± 3C), followed by static leak check.
(c)
(d)
Static leak check at room temperature.
Static leak check at 275 ± 5F (135 ± 2.5C).
(e)
200,000 cycles at 275F (135C), followed by static leak check at 275F (135C), room
(f)
temperature and -65F (-54C).
200,000 cycles starting at -65°F (-54C ) and increasing temperature to 275F (135C)
(g)
followed by static leak check at 275F (135C), room temperature and -65F (-54C).
(h)
Repeat paragraph (g) until a total of 1,100,000 impulse cycles have been completed.
4.5.3 Conformance. All specimens used in conformance inspection shall be unaged (except
those used for volume change).
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