Approval plate means a metal plate, the design of which meets MSHA's requirements, for attachment to an approved machine or accessory, identifying it as permissible for use in gassy mines or tunnels. Branch circuit means an electrical circuit connected to the main circuit, the conductors of which are of smaller size than the main circuit. Bureau means the U.S. Bureau of Mines. Certification label means a plate, label, or marking, the design of which meets MSHA's requirements, for attachment to a certified component identifying the component as having met the MSHA's requirements for incorporation in a machine to be submitted for approval. Component means an integral part of an electrical machine or accessory that is essential to the functioning of the machine or accessory.
Cylindrical joint means a joint comprised of two contiguous, concentric, cylindrical surfaces.
Distribution box means an enclosure through which one or more portable cables may be connected to a source of electrical energy, and which contains a short-circuit protective device for each outgoing cable. Experimental equipment means any electrical machine or accessory that an applicant or MSHA may desire to operate experimentally for a limited time in a gassy mine or tunnel. Fire-resistant as applied to conveyor belts means belting that will pass the flame tests hereafter specified. Flame-arresting path means two or more adjoining or adjacent surfaces between which the escape of flame is prevented. Flame resistant as applied to cable, hose, and insultating materials means material that will burn when held in a flame but will cease burning when the flame is removed.