FED-STD-228A
Method 4131.1
18 APRIL 2014
RESISTANCE TO LIGHT, INSULATION AND SHEATH
1. SCOPE
1.1 This method is intended for use in determining the comparative resistance of rubber and rubber-like
insulation and sheaths of insulated wire and cable to deterioration when exposed to light having a
frequency range approximating that of sunlight but having a greater intensity in the ultra-violet range than
sunlight. The method is not applicable to hard or semihard rubbers. The deterioration resulting from the
exposure is determined by observing the nature and degree of cracking and checking and by comparing
the tensile strength and elongation of the exposed specimen with that of unexposed specimen taken from
the same piece of material. The specimen is exposed in the stretched condition. The quantity of
radiation to which the specimen is exposed is measured by means of the decomposition of uranyl oxalate
solution.
2. SPECIMEN
2.1 The specimen should be a piece of the insulation or sheath taken from the inspection unit. It should
be not less than 5/8 inch in width and 6 inches in length, and should be buffed to a uniform thickness of
0.35 ± 0.005 inch. If the size of the insulation is too small to permit preparation of a specimen of the
above dimensions, a tube specimen six inches in length may be used.
3. APPARATUS AND REAGENTS
3.1 The apparatus and reagents shall be as follows:
3.1.1 A light source consisting of a vertical ventilated, flaming carbon are designed to accommodate two
or three pairs of carbons, number 22 upper and number 13 lower; the arc to burn between only one pair
of carbons at a time. The carbons shall be of the cored type sunshine carbons (of the National Carbon
Company or equal) designed to duplicate as closely as possible the spectral distribution of sunlight. The
arc shall operate on 60 amperes and 50 volts across the arc on alternating current or on 50 amperes and
60 volts across the arc on direct current.
3.1.2 Unless otherwise specified in the detail specification, the arc shall be surrounded by Corex D filters
or other enclosure having equivalent absorbing and transmitting properties. Each Corex D panel shall be
5/64 to 1/16 inch in thickness. Filters shall be replaced after 8000 hours of service.
3.1.3 A cylindrical rotating framework designed to carry specimen holders in such a way that the surface
of the specimens are 18 ½ inches ± ½ inch from the center of the arc. The frame work shall rotate around
the arc at a uniform speed of one complete revolution every 2 hours.
3.1.4 Specimen holder suitable for mounting the specimen vertically while it is rotated about the carbon
arc to provide uniform distribution of light. The holders shall be designed to accommodate either one
specimen 2 by 6 inches or two specimens each 1 by 6 inches in size and to stretch them to any
elongation up to 20 percent. A suitable holder is shown on figure 4131A.
3.1.5 A cylindrical drum of corrosion-resisting material for enclosing the lamps and framework. The
cylinder shall be equipped with a protective cover for shielding the operator from radiation from the arc,
and overflow for carrying away the water from a spray, and a sliding door to permit access to the
specimens.
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