FED-STD-228A
Method 5021.1
18 APRIL 2014
HEAT DISTORTION, INSULATION
1. SCOPE
1.1 This method is intended for use in determining the distortion of insulating materials. It is particularly
applicable to thermoplastic insulation.
2. SPECIMEN
2.1 Conductors No. 0000 AWG and smaller. The specimen should consist of a right cross section of the
inspection unit 1 inch in length from which any covering over the insulation has been removed.
2.2 Conductors larger than No. 0000 AWG. The specimen should consist of a piece of the insulation 1
inch in length and 9/16 ± 1/16 inch in width taken from the inspection unit and buffed, method 3011, to
0.050 ± 0.010 inch in thickness.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 A dial micrometer with a flat anvil not less than 0.375 inch in diameter and a flat presser foot 0.375
± 0.01 inch in diameter. The presser foot shall be equipped to support added weights, table I, for applying
force to the specimen. The surfaces of the anvil and presser foot shall be parallel to within 0.0001 inch.
The micrometer shall be graduated to read in mils or 0.0001 inch.
3.1.2 Weights as required in table I.
TABLE I. Gage loads
Conductor size (AWG)
Load on
gage
(grams)
No. 18 - - - - - - - - - - - - - - - - - - - - - - -
300
No. 16 - - - - - - - - - - - - - - - - - - - - - - -
400
Nos. 15 to 8, inclusive - - - - - - - - - - - -
500
Nos. 7 to 1, inclusive - - - - - - - - - - - - -
750
Nos. 0 to 0000, inclusive - - - - - - - - - -
1,000
Nos. larger than 0000 - - - - - - - - - - - -
2,000
3.1.3 A circulating air oven capable of maintaining the specimen at the required temperature within ± 1°C
(2°F).
4. PROCEDURE
4.1 Unless otherwise specified in the detail specification, the specimen shall be subjected to a
temperature of 121° ± 1°C (250° ± 2°F) for a period of 1 hour under the weight required in table I.
4.2 Conductors size 0000 AWG or smaller.
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