FED-STD-228A
4.2.1 The thickness of the insulation shall be determined as described in method 1011 and the value
recorded as T1.
4.2.2 The oven shall be heated to the required temperature and maintained throughout the test. The
thickness gage, 3.1.1, the weight required in table I, and the specimen shall be placed in the oven and
allowed to remain for a period of 1 hour.
4.2.3 At the end of the pre-heating period, the specimen shall be placed directly under the foot of the
gage and the weight applied to the gage. The gage with specimen in position shall remain in the oven for
the required time. At the end of the heating period, the diameter of the specimen shall be read from the
gage and recorded as D1.
4.2.4 The insulation shall be removed from the conductor and the diameter of the conductor of the
specimen determined as described in method 1431 and the value recorded as D2.
4.3 Conductors larger than size 0000 AWG.
4.3.1 The thickness (diameter) of the specimen shall be determined with the gage described in 3.1.1 with
no added load on the presser foot, and the value recorded as T3.
4.3.2 The oven shall be heated to the specified temperature and maintained throughout the test. The
thickness gage, 3.1.1, the weight required in table I, and the specimen shall be placed in the oven and
allowed to remain for a period of 1 hour.
4.3.3 At the end of the pre-heating period, the specimen shall be placed directly under the foot of the
gage and the weight applied to the gage. The gage with specimen in position shall remain in the oven for
the required time. At the end of the heating period, the thickness of the specimen shall be read from the
gage and the value recorded as T4.
5. RESULTS
5.1 Calculation. The distortion of the insulation of the specimen shall be calculated as follows:
5.1.1 Conductor sizes 0000 AWG and smaller.
T2 = D1-D2
2
where:
T2=the thickness of insulation after heat distortion, inch
D1=the diameter of the specimen after heating, inch
D2=the diameter of the conductor from the specimen, inch.
Change in thickness of insulation, percent =T1-T2 x 100
T1
148
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