FED-STD-228A
Method 8121.1
18 APRIL 2014
COVERAGE, BRAID, METAL ARMOR
1. SCOPE
1.1 This method is intended for use in determining the coverage of braided metal armor of insulated wire
and cable.
2. SPECIMEN
2.1 The specimen should be a piece of the inspection unit at least 12 inches in length from which any
covering over the armor has been removed.
3. APPARATUS REAGENTS
3.1 The apparatus and reagents shall be as described in the methods referenced in 4.
4. PROCEDURE
4.1 The number of picks per inch in the specimen shall be determined as described in method 8011 and
the value recorded as P.
4.2 The number of wires per carrier shall be determined as described in method 8021 and the value
recorded as N.
4.3 The angle of the braid shall be determined as described in method 1631 and the value recorded as
A.
4.4 The diameter of the individual braid wires shall be determined as described in method 1421 and the
value recorded as d.
4.5 The diameter of the cable under the armor shall be determined as described in method 1111 for
diameter over the braid and the value recorded as D.
5. RESULTS
5.1 Calculation. The coverage of the braided metal armor of the specimen shall be calculated as follows:
2
Coverage, percent=(2F-F ) x 100
where:
F=N*P*d.
sin A
A=the angle of braid with axis of cable; Tan. A is 2š DP/C.
d=the diameter of individual braid wires, inch.
C=the number of carriers.
D=the diameter of cable under armor, inches.
N=the number of ends per carrier.
P=the number of picks per inch of cable length.
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