30 CFR § 7.408 Test for flame resistance of signaling cables.
(a)Test procedure. (1) Prepare 3 samples of cable each 2 feet
long.
(2) Prior to testing, condition each test specimen for a
minimum of 24 hours at a temperature of 70 ±10 °F (21.1 ±5.5 °C) and relative
humidity of 55 ±10 percent. These environmental conditions shall be maintained
during testing.
(3) Center the test specimen horizontally in the test
chamber on the three rods. The three rods shall be positioned perpendicular
to the longitudinal axis of the test specimen and at the same height, which
permits the tip of the inner cone from the flame of the gas burner, when
adjusted in accordance with the test procedure, to touch the test specimen.
The specimen shall be maintained at this height for the duration of the flame
test. The two outermost rods shall be placed so that 1 inch of cable extends
beyond each rod. The third rod shall be placed at the midpoint of the cable.
The specimen shall be free from external air currents during testing.
(4) Adjust the gas burner to give an overall blue flame 5
inches high with a 3-inch inner cone. There shall be no persistence of yellow
coloration.
(5) Apply the tip of the inner cone from the flame of the
gas burner for 30 seconds directly beneath the specimen centered between
either and support and the center support.
(6) After subjecting the test specimen to external flame
for the specified time, fully remove the flame of the gas from beneath the
specimen without disturbing air currents within the test chamber.
(7) Record the amount of-time the test specimen continues
to burn after the flame from the gas burner has been removed. The duration of
burning includes the burn time of any material that falls from the test
specimen after the flame from the gas has been removed.
(8) Record the length of burned (charred) area of each
test specimen measured longitudinally along the cable axis.
(9) Repeat the procedure for the remaining two
specimens.
(b)Acceptable performance. Each of the three test specimens shall
meet the following criteria:
(1) The duration of burning shall not exceed 60
seconds.
(2) The length of the burned (charred) area shall not
exceed 6 inches.
