MIL-DTL-5516D
4.5.2 Physical properties after aging.
4.5.2.1 Change in tensile strength, elongation, permanent set, and hardness. Air aging of
samples (see tables I and III) shall be conducted as specified in ASTM D573. Oil aging shall be
accomplished by immersing in Specification MIL-PRF-5606 hydraulic oil, for a period of 7 days at
70° ± 1°C (158° ± 2°F). The tensile strength, elongation, permanent set, and hardness shall be
determined on the aged specimens in accordance with 4.5.1. The percentage difference
between aged and unaged values for tensile strength and elongation (table I), and the actual
values for change in hardness and permanent set (table I) shall be recorded.
4.5.2.2 Volumetric change. Swelling shall be determined as specified in Federal Test Method
Standard No. 601, Method 6211, except the specimens shall be first article sample packings or
gaskets of the sizes and quantities listed in table III. The period of immersion shall be 7 days.
The fluid shall be hydraulic oil conforming to Specification MIL-PRF-5606, as specified in 4.4.4.4,
maintained at a temperature of 70° ± 1°C (158° ± 2°F). The volumetric change shall not exceed
the value specified in table I.
4.5.3 Corrosion and adhesion. Packings or gaskets of the type required for first article tests, in
quantities and sizes specified in table III, shall be prepared for corrosion testing by inserting
sufficient quantities of the seals in a desiccator or similar humidity chamber maintained at 92
percent minimum relative humidity and at 24± 2°C (75° ± 5°F), temperature for 72 hours
minimum. Metallic plates of the metals listed below shall be polished to a surface roughness of 5
to 15 microinches rms finish. The edges shall also be polished to reduce the formation of edge
corrosion. Plates shall be washed with precipitation naphtha, as specified in ASTM D91, or similar
degreasing agent. The metals used shall be as follows:
(a)
Aluminum alloy: Specification SAE-QQ-A-250/4
(b)
Brass: Specification ASTM B36/B36M
(c)
Phosphor bronze: Specification ASTM B139/B139M
(d)
Steel: Specification SAE-AMS6345
The humidified seals and the metallic plates shall be immersed in Specification MIL-PRF-6083
type I fluid and drained to the drip point. The seals and plates shall then be so laid together in a
stack that at least two seals contact each specified metal. The stack shall be held together with a
pressure of 20 to 30 pounds and placed in a desiccator which is maintained at not less than 92
percent relative humidity at 24° ± 3°C (75° ± 5°F). (Di-potassium acid phosphate, K2HP04, when
placed in distilled water in sufficient quantity to produce a concentrated solution, will maintain
approximately 92 percent humidity in a sealed desiccator at 20°C (68°F) temperature). Time of
immersion for this portion of test shall be 96 hours minimum for all acceptance tests and 14 days
minimum for all first article test analyses. No more than 15 minutes should elapse between the
time the test samples are removed from the prehumidifying chamber and placed in the stacked
condition in the second humidity chamber. At the termination of this test, the procedure outlined
below shall be followed:
(1) The surfaces of the plates which were in contact with the seals shall be inspected for
discoloration, deposits, pitting, etc. If any exists, the surfaces of the plates shall be washed in
precipitation naphtha. Deposits determined as rubber compounds or elements therefrom, which
can be removed by this process and which do not occur on the separate control plates, shall be
construed as adhesion.
(2) Any pits or eroded marks remaining after this process shall be construed to be
corrosion. Discoloration or staining (marks which do not physically affect the surface of the plates
and which easily wash or buff off) shall not be considered detrimental. If any doubt should arise
about the presence of pitting, erosion, or corrosion on the metal plates, a microscope of
approximately 10- to 15-power magnification shall be used to determine the actual condition.
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