MIL-DTL-38359E
4.6.4.1 Insulation thickness test. The average thickness of the insulation shall be determined by
measuring the diameter over the insulation and subtracting from it the diameter of the conductor and
shield. The difference shall then be divided by two, and the result taken as the thickness of the insulation.
Five sets of measurements shall be obtained along the length of a 10-foot sample and the average of the
five sets of measurements determined. Each set of measurements shall consist of the determination of
the maximum and minimum diameters at the cross-section measured. Measurements shall be made with
a micrometer caliper having flat surfaces on both the anvil and end of the spindle, and graduated to read
directly in mils, or with a dial micrometer having an anvil, the pressure foot .078 inch wide and .375 inch
long, and exerting a force of 10 grams on the pressure foot. If the results of measurement by such
methods are in doubt, the optical method shall be used. The optical method utilizes a micrometer
microscope accurate to at least .0002 inch (0.01 mm). Measurements of the diameter shall be made at a
section halfway between the ends of the sample and at sections 1 inch (25.4 mm) on each side of the
midpoint. The average of the maximum and minimum diameters at each section shall be determined,
and the lowest of the three averages shall be used as the diameter of the sample in calculating the
thickness of the insulation.
4.6.5 Continuity test. Each length of finished cable shall be tested for continuity of the conductor.
4.6.6 Moisture absorption tests. The moisture absorption tests shall be in accordance with part 6 of
NEMA WC 71. The test temperature shall be a minimum of 75 ºC.
4.6.6.1 Surface resistivity (dc potential). The samples shall be subjected to the tests specified in
4.6.6.2 Surface resistivity (ac potential). Using the same test specimens, similar electrodes spaced 3
inches (76.2 mm) apart shall be attached over the central test section. A 60-cycle ac potential increasing
uniformly to 20,000 volts in 20 seconds shall be applied between the electrodes and maintained for 1
minute without flashover or damage to the cable.
4.6.6.3 U-bend discharge. The samples shall be subjected to the tests specified in NEMA WC 71
except that the test potential shall be 150 volts per mil of nominal thickness.
4.6.7 Ozone resistance test. Samples of finished cable shall show no damage after exposure for 3
hours to an ozone concentration of not less than 0.025 percent and not more than 0.030 percent (by
volume) according to the ozone-resistance tests specified in NEMA WC 71.
4.6.8 Cold bend test. A sample of the finished cable shall be placed in a cold temperature chamber
and maintained at a temperature of -40 ºC or below for 24 hours. While still in the cold chamber, the
sample shall be given five tight turns around a mandrel whose diameter is five times that of the finished
cable. There shall be no visible evidence of cracking. The rate of winding shall be approximately five
turns per minute.
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