MIL-DTL-3533C
4.4.5 Permanent set (Type I only). Permanent set on three O-Rings shall be made by
measuring the ID and then stretching over a tapered cone (lubricated with ASTM No. 1 oil) until the
ID of the seal has been stretched 150% (if the ID measures .984 inch (25 mm), the ring shall be
stretched to 2.460 inches (62.484 mm) ID). The ring shall be held in this stretched state for ten
minutes, removed from the cone, and the ID determined after ten minutes rest. Permanent set
shall be calculated from the as-measured ID before and after the test. Any breaking or cracking of
the test samples shall be cause for rejection.
4.4.6 Temperature retraction (Type I only). This test shall be in accordance with ASTM D1329
except that O-Ring samples (Size No. 214 of SAE AS568) shall be used and three samples tested.
After installation, samples shall be elongated 50% as determined by the rod markings and the rate
of warming shall be 1F (.6C) per minute. The temperature retraction 50/10 reading of these seals
shall be determined and recorded.
4.4.7 Low temperature flexibility (Type II only). This test shall be in accordance with ASTM
D746 except that the thickness of the samples shall be .075 ± .005 inch (1.905 ± .127 mm). The
test temperature for exposure of the samples shall be 1.4 ± 4F (-17 ± 2C).
4.4.8 Adhesion and corrosion. Specimens shall be tested in accordance with Method 14211 of
Federal Test Method Standard No. 601. For Type I material, the actual O-Ring shall be used for
the test specimen in place of the one inch square specimen.
4.4.9 Air aging. Air aging shall be conducted in accordance with ASTM D573.
4.4.10 Aging in liquids. Specimens shall be aged in accordance with Method 6001 of
Federal Test Method Standard No. 601 using Medium No. 1 for the oil and synthetic sea water for
the water medium. Tests shall be conducted for a period of 168 ± 1 hour at a temperature of 158
± 4F (70 ± 2C).
4.4.10.1 Synthetic sea water. The synthetic sea water used in the aging tests shall be
formulated as follows:
Sodium Chloride
23 gr
Sodium Sulfate
8 gr
Decahydrate
Stock Solution
20 ml
Distilled Water
To make 1 liter
4.4.10.1.1 Stock solution. The stock solution used in formulating the synthetic sea water
shall have the following composition:
Potassium Chloride
10 gr
Potassium Bromide
45 gr
Magnesium Chloride
550 gr
Sexahydrate
Calcium Chloride
110 gr
Sexahydrate
Distilled Water
To make 1 liter
4.4.10.2 Tensile strength and ultimate elongation. Tensile strength and ultimate elongation
property determinations after liquid aging shall be performed in accordance with Method 6121 of
Federal Test Method Standard No. 601 except that a recovery period of twenty hours in the
original test liquids will be allowed.
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