30 CFR § 75.2 - Definitions.

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§ 75.2 Definitions.

The following definitions apply in this part.

Act. The Federal Mine Safety and Health Act of 1977.

Active workings. Any place in a coal mine where miners are normally required to work or travel.

Adequate interrupting capacity. The ability of an electrical protective device, based upon its required and intended application, to safely interrupt values of current in excess of its trip setting or melting point.

Anthracite. Coals with a volatile ratio equal to 0.12 or less. The volatile ratio is the volatile matter content divided by the volatile matter plus the fixed carbon.

Approval documentation. Formal papers issued by the Mine Safety and Health Administration which describe and illustrate the complete assembly of electrical machinery or accessories which have met the applicable requirements of 30 CFR part 18.

Certified or registered. As applied to any person, a person certified or registered by the State in which the coal mine is located to perform duties prescribed by this part 75, except that in a State where no program of certification or registration is provided or where the program does not meet at least minimum Federal standards established by the Secretary, such certification or registration shall be by the Secretary.

Circuit-interrupting device. A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically at a predetermined overcurrent value without damage to the device when operated within its rating.

Coal mine. Includes areas of adjoining mines connected underground.

Filter Self-Rescuer (FSR). A type of gas mask approved by MSHA and NIOSH under 42 CFR part 84 for escape only from underground mines and which provides at least 1 hour of protection against carbon monoxide.

Ground fault or grounded phase. An unintentional connection between an electric circuit and the grounding system.

Low voltage. Up to and including 660 volts, medium voltage means voltages from 661 to 1,000 volts; and high voltage means more than 1,000 volts.

Motor-starter enclosure. An enclosure containing motor starting circuits and equipment.

Nominal voltage. The phase-to-phase or line-to-line root-mean-square value assigned to a circuit or system for designation of its voltage class, such as 480 or 4,160 volts. Actual voltage at which the circuit or system operates may vary from the nominal voltage within a range that permits satisfactory operation of equipment.


(1) As applied to electric face equipment, all electrically operated equipment taken into or used inby the last open crosscut of an entry or a room of any coal mine the electrical parts of which, including, but not limited to, associated electrical equipment, components, and accessories, are designed, constructed, and installed, in accordance with the specifications of the Secretary, to assure that such equipment will not cause a mine explosion or mine fire, and the other features of which are designed and constructed, in accordance with the specifications of the Secretary, to prevent, to the greatest extent possible, other accidents in the use of such equipment. The regulations of the Secretary or the Director of the Bureau of Mines in effect on March 30, 1970, relating to the requirements for investigation, testing, approval, certification, and acceptance of such equipment as permissible shall continue in effect until modified or superseded by the Secretary, except that the Secretary shall provide procedures, including, where feasible, testing, approval, certification, and acceptance in the field by an authorized representative of the Secretary, to facilitate compliance by an operator with the requirements of § 75.500 within the periods prescribed in § 75.500.

(2) As applied to equipment other than permissible electric face equipment: (i) Equipment used in the operation of a coal mine to which an approval plate, label, or other device is attached as authorized by the Secretary and which meets specifications which are prescribed by the Secretary for the construction and maintenance of such equipment and are designed to assure that such equipment will not cause a mine explosion or a mine fire. (ii) The manner of use of equipment means the manner of use prescribed by the Secretary.

Qualified person. As the context requires:

(1) An individual deemed qualified by the Secretary and designated by the operator to make tests and examinations required by this part 75; and

(2) An individual deemed, in accordance with minimum requirements to be established by the Secretary, qualified by training, education, and experience, to perform electrical work, to maintain electrical equipment, and to conduct examinations and tests of all electrical equipment.

Respirable dust. Dust collected with a sampling device approved by the Secretary and the Secretary of Health and Human Services in accordance with part 74 - Coal Mine Dust Personal Sampler Units of this title. Sampling device approvals issued by the Secretary of the Interior and Secretary of Health, Education, and Welfare are continued in effect.

Rock dust. Pulverized limestone, dolomite, gypsum, anhydrite, shale, adobe, or other inert material, preferably light colored, 100 percent of which will pass through a sieve having 20 meshes per linear inch and 70 percent or more of which will pass through a sieve having 200 meshes per linear inch; the particles of which when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air; and which does not contain more than 5 percent combustible matter or more than a total of 4 percent free and combined silica (SiO2), or, where the Secretary finds that such silica concentrations are not available, which does not contain more than 5 percent of free and combined silica.

Secretary. The Secretary of Labor or the Secretary's delegate.

Self-Contained Self-Rescuer (SCSR). A type of closed-circuit, self-contained breathing apparatus approved by MSHA and NIOSH under 42 CFR part 84 for escape only from underground mines.

Short circuit. An abnormal connection of relatively low impedance, whether made accidentally or intentionally, between two points of different potential.

Working face. Any place in a coal mine in which work of extracting coal from its natural deposit in the earth is performed during the mining cycle.

Working place. The area of a coal mine inby the last open crosscut.

Working section. All areas of the coal mine from the loading point of the section to and including the working faces.

[57 FR 20913, May 15, 1992, as amended at 60 FR 30401, June 8, 1995; 67 FR 11001, Mar. 11, 2002]

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