30 CFR § 75.604
Permanent splicing of trailing cables.
When permanent splices in trailing cables are made, they shall be:
(a) Mechanically strong with adequate electrical conductivity and
(b) Effectively insulated and sealed so as to exclude moisture; and
(c) Vulcanized or otherwise treated with suitable materials to provide
flame-resistant qualities and good bonding to the outer jacket.
(d) Made using splice kits accepted or approved by MSHA as flame resistant.
[57 FR 61223, Dec. 23, 1992]