FED-STD-228A
Method 5011.1
18 APRIL 2014
HEAT SHOCK, INSULATION
1. SCOPE
1.1 This method is intended for use in determining the effect of heat on insulating materials in the bent
form. It is primarily applicable to thermoplastic insulation. It is applicable to single conductor insulated
wire or cable.
2. SPECIMEN
2.1 The specimen should consist of a piece of the inspection unit of sufficient length to be tested as
described in section 4, from which any covering over the insulation has been removed.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 A mandrel of the size required in column 3 of table I.
3.1.2 A circulating air oven capable of maintaining the specimen at the required temperature within ±1°C
(2°F).
TABLE I
Mandrel size, equals
the nominal outside
Size of conductor AWG or circular mils
Number of adjacent turns
diameter of the
insulated wire
multiplied by the
following factor
No. 8 and smaller
6
1
No. 7 to No. 2, inclusive
6
2
No. 1
1
2
180° bend
2
No. 0 to 0000
225,000 circular mils and over
180° bend
5
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.
4.2 The specimen shall be wound around the mandrel (if size 1 AWG or smaller) or given a 180° bend
around a mandrel (if size 0 or larger) as specified in table I. While in the wound or bent condition, the
specimen shall be exposed to circulating air at the required temperature for the required period of time.
At the end of the exposure period, the specimen shall be examined for cracking of the insulation both on
internal and external surfaces by axially splitting the specimen at two axes 180° apart and carefully
removing the semi-tubes from the connector.
4.3 Flat twin cable shall be bent on the minor axis of its cross section only. The minor diameter shall be
used in determining the size of the mandrel.
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