MIL-DTL-24643C
4.8.24 Halogen content. The halogen content of the cable jacket or fillers shall be determined by X-ray
fluorescence or analytically following an inspection and analyses of the chemical composition of all ingredients
used.
4.8.24.1 Observation. Specimen failure shall be construed if the halogen content is greater than that specified
(see 3.1).
4.8.25 Smoke index. The smoke index shall be measured as specified in NES 711 with exceptions and
4.8.25.1 Specimen:
a. Jacket. Each specimen shall consist of a sufficient number of 75 mm long strips cut from the cable jacket
to completely cover the face area of the sample holder. To prevent excessive buckling and distortion of the
specimen during test, a wire mesh, manufactured from either a 1.0 mm diameter stainless steel wire with a spacing
of 12.5 mm and a square mesh configuration or a 40 mil stainless steel wire 2 mesh screen (2 openings per inch),
shall be placed inside and across the face of the sample holder. The specimen shall be fabricated by placing the
specimen holder (with wire mesh) test face down onto a flat surface and positioning each 75 mm length in the
holder in a parallel arrangement so that when the holder is in the test position the strips will be vertical. An
insulating block 10 mm thick completely wrapped in aluminum foil shall be placed on top of the strips followed by a
tension spring and locking pin.
b. Insulation. The test specimen shall be a 1 meter length of 22 AWG finished wire with a nominal wall
thickness of 0.020 inch of insulation material.
c.
Fillers and sealants.
(1) Non fibrous. The test specimen shall be 3 by 3 inches of 0.070±0.010 inch thick block of the same
material used in the cable.
(2) Fibrous. The test specimen shall consist of as many 75 mm lengths of 0.070±0.010 inch diameter
strands necessary to fill the 3 by 3 inch test specimen holder one layer deep and as closely spaced as possible. The
test specimens shall be prepared as described in 4.8.25.1.a.
4.8.25.2 Special procedures. Special procedures shall include the following:
a.
Only the use of propane gas shall be allowed.
b.
The Radiometer shall be used to calibrate the heat flux at the initial start of each test period.
c. The test chamber shall be calibrated using a NIST CELLULOSE standard at the initial start of each test
period.
d.
The chamber shall be inspected to assure air tightness. Seals and gaskets shall be replaced as needed.
e. The test shall be run using a minimum of three specimens. If test values are below the limits specified, (see
3.1) test is complete. If one test value deviates from the median value by more than 20 percent two additional tests
shall be performed. The high and low-test values shall be discarded and the remaining three averaged.
4.8.25.3 Observation. Specimen failure shall be construed if any smoke index is greater than that specified (see
4.8.26 Immersion tests. Specimens of the cable jacket material (see 4.8.19.1) shall be immersed in the fluids
shown in table XIV for 24 hours (except for MIL-PRF-17331which shall be immersed for 18 hours) at the
temperatures specified. The specimens shall then be removed, blotted to remove excess fluid, then suspended in air
at room temperature for not less than 3½ nor more than 4½ hours. Each specimen shall be tested as specified in
48
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business