FED-STD-228A
Method 6121.1
18 APRIL 2014
VOLTAGE WITHSTAND, INSULATION, FLEXING
1. SCOPE
1.1 This method is intended for use in determining the ability of insulated wire or cable to withstand a
limited amount of flexing without breakdown of the insulation. It is particularly applicable to varnished
cloth insulated wire and cable with or without metallic coverings.
2. SPECIMEN
2.1 The specimen should be a piece of the inspection unit at least 13 feet in length.
3. APPARATUS
3.1 The apparatus shall consist of a mandrel of the size specified in the detail specification.
4. PROCEDURE
4.1 The test voltage and the period of time of its application shall be as specified in the detail
specification.
4.2 Any covering shall be removed from the surface of the insulation of a single conductor specimen for a
distance of about 1 inch from each end. The ends shall be dipped into melted paraffin or other suitable
material to minimize the effect of moisture in reducing insulation resistance between the covering and the
conductor. In the case of multiple-conductor cable the conductors shall be separated at each end of the
specimen and the ends treated as described for single-conductor cable. In the case of lead-covered
cable the lead shall be stripped back for a distance of 3 or 4 inches at each end of the specimen.
4.3 A segment of length of the specimen shall be bent through an arc of 180° around a mandrel the
required diameter. The same segment of the specimen shall be straightened and bent through a 180° arc
in the opposite direction. The specimen shall be straightened again and the double bend cycle repeated,
making a total of 4 bends of the same segment. The specimen shall be so held that rotation about the
length axis of the segment does not occur during the bending operation. After the final bending operation
the specimen shall be left in the bent position. The entire bent portion of the specimen plus an additional
20 percent of the length of the unbent portion beyond each end of the arc shall be wrapped in metal foil or
other suitable conducting material (except when lead sheathed).
4.4 The bent specimen shall be subjected to the voltage withstand test as described in method 6111.
4.5 A flat twin cable shall be bent on the minor axis of its cross section only.
5. RESULTS
5.1 Unless otherwise specified in the detail specification, one specimen from each inspection unit shall
be tested.
5.2 Whether the insulation of the specimen withstood the specified test voltage without failure shall be
recorded.
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