FED-STD-228A
Method 4031.1
18 APRIL 2014
AIR OVEN TEST, INSULATION AND SHEATH
1. SCOPE
1.1 This method is intended for use in determining the effect of elevated temperatures and air at normal
atmospheric pressure on rubber and rubber-like insulation and sheaths of insulated wire and cable.
2. SPECIMEN
2.1 The specimen should be as described in methods 3021 and 3031 or other method of test required for
determining the amount of deterioration, 4.2.
3. APPARATUS
3.1 The apparatus shall be as follows:
3.1.1 The equipment listed in 3.2 may be used where air is employed as the heating medium. Apparatus
in 3.3 may be used where the heating medium consists of a liquid bath.
3.2 Air as a heating medium.
3.2.1 A circulating air oven with provisions for suspending specimens without crowding and without
touching each other or the sides of the oven. The volume should not be less than 12 x 12 x 12 inches
and not more than 36 x 36 x 48 inches.
3.2.2 A source of heat, which is optional, shall be located outside of the aging chamber proper.
3.2.3 A thermo-regulator for automatic temperature control of the heating medium.
3.2.4 Equipment for complete circulation of the heating medium so as to keep the temperature of the air
throughout the oven within ± 1°C (2°F). The following precautions shall be taken: (a) If a motor-driven
fan is used, the air in the oven shall not come in contact with the fan motor-brush discharge because of
danger of ozone formation, (b) baffles shall be used as required to prevent local overheating and dead
spots, and (c) the thermostatic control shall be so located as to give accurate temperature control of the
heating medium. The preferred location is adjacent to the recording thermometer.
3.2.5 Recording thermometers located in the heating medium to record the actual aging temperature in
various parts of the oven.
3.3 Liquid as a heating medium.
3.3.1 Apparatus employing a liquid heating medium consisting of several small aging containers
submerged in a thermostatically-controlled liquid bath. The equipment shown on figure 4031 has been
found suitable for the purpose.
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