[Code of Federal Regulations]
[Title 30, Volume 1]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR18.37]

[Page 100-101]
 
                       TITLE 30--MINERAL RESOURCES
 
  CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR
 
PART 18--ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES--Table of Contents
 
             Subpart B--Construction and Design Requirements
 
Sec. 18.37  Lead entrances.

    (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.

[[Page 101]]

    (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.

[33 FR 4660, Mar. 19, 1968, as amended at 57 FR 61210, Dec. 23, 1992]