(a) Insulated cable(s), which must extend through an outside wall of
an explosion-proof enclosure, shall pass through a stuffing-box lead
entrance. All sharp edges that might damage insulation shall be removed from
stuffing boxes and packing nuts.
(b) Stuffing boxes shall be so designed, and the amount of packing
used shall be such, that with the packing properly compressed, the gland nut
still has a clearance distance of 1/8 inch or more to travel without meeting
interference by parts other than packing. In addition, the gland nut shall
have a minimum of three effective threads engaged. (See Figures 8, 9, and
10 in Appendix II.)
(c) Packing nuts and stuffing boxes shall be secured against
loosening.
(d) Compressed packing material shall be in contact with the cable
jacket for a length of not less than 1/2. inch.
(e) Special requirements for glands in which asbestos-packing
material is specified are:
(1) Asbestos-packing material shall be untreated, not less
than 3/16-inch diameter if round, or not less than 3/16 by 3/16 inch if
square. The width of the space for packing material shall not exceed by more
than 50 percent the diameter or width of the uncompressed packing
material.
(2) The allowable diametrical clearance between the cable
and the holes in the stuffing box and packing nut shall not exceed 75 percent
of the nominal diameter or width of the packing material.
(f) Special requirements for glands in which a compressible material
(example--synthetic elastomers) other than asbestos is specified, are:
(1) The packing material shall be flame resistant.
(2) The radial clearance between the cable jacket and the
nominal inside diameter of the packing material shall not exceed 1/32-inch,
based on the nominal specified diameter of the cable.
(3) The radial clearance between the nominal outside
diameter of the packing material and the inside wall of the stuffing box
(that portion into which the packing material fits) shall not exceed
1/32-inch.
