FED-STD-228A
4. PROCEDURE
4.1 Conductor No. 1 AWG and smaller.
4.1.1 The circumference of the specimen shall be determined as described in method 1441.
4.1.2 The surface of the insulation shall be cleaned of all fibers and particles of foreign material by
means of the cloth and ethyl alcohol. The specimen shall then be dried in a vacuum (pressure of
approximately 20 mm of mercury) over calcium chloride at a temperature of 70° ± 2°C (158° ± 4°F) for 24
hours, cooled to room temperature in a desiccators over calcium chloride, and weighed to the nearest
milligram within 3 minutes after removal from the desiccators. The drying and weighing shall be
continued at 24-hour intervals until the weight is constant within 1 milligram in two consecutive weighings
or until any one weight is greater than the previous weight. The lowest weight shall be recorded as W1.
4.1.3 The specimen shall be bent in the form of a U around the mandrel which shall have a diameter four
times that of the specimen. Each end of the specimen shall be inserted through a hole in the cover plate
of the water bath so that 10 inches of the U-shape of the specimen shall be exposed below the plate. If
the specimen does not fit the holes tightly, accurately drilled, closely fitting, nonferrous metal washers
shall be used to complete the enclosure of the holes in the cover plate, and to assist in holding the
specimens tightly in place.
4.1.4 The water bath shall be filled with distilled water and the cover with the specimen in place shall be
placed over the bath with the U-portion of the specimen immersed in the water. The water level shall be
maintained flush with the under side of the cover plate during the test, care being taken that no water
comes in contact with the ends of the specimen.
4.1.5 The specimen shall be exposed in the water bath for a period of 166 hours at a temperature of 70°
± 2°C (158° ± 4°F) after which the cover plate with the specimen shall be removed from the bath and
transferred to a similar vessel filled with distilled water at a temperature of 24° ± 3°C (75° ± 5°F). The
specimen shall be allowed to remain in this bath for not less than 5 minutes nor more than 15 minutes.
The washers shall then be carefully removed from the specimen. The specimen shall be removed from
the bath and shaken to remove the loose water. The remaining surface water shall be removed by
blotting the specimen lightly with clean, lintless, absorbent gauze. The specimen shall then be weighed
to the nearest milligram within 3 minutes after removal from the water. This weight shall be recorded as
W2.
4.1.6 The specimen shall be dried in the vacuum, 4.1.1, over calcium chloride at a temperature of 70° ±
2°C (158° ± 4°F) for 24 hours, cooled to room temperature in a desiccators, and weighed to the nearest
milligram within 3 minutes after removal from desiccators. The drying and weighing shall be continued at
24-hour intervals until the weight is constant within 1 milligram in two consecutive weighings, or until any
one weight is greater than the previous weight. The lowest weight shall be recorded as W2.
4.2 Conductor No. 0 AWG and larger.
4.2.1 The buffed specimen shall be cleaned, cooled, and the thickness determined as described in
method 1124. The value shall be recorded as T.
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