[Code of Federal Regulations]

[Title 30, Volume 1]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 30CFR18.47]



[Page 109]

 

                       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.  18.47  Voltage limitation.



    (a) A tool or switch held in the operator's hand or supported 

against his body will not be approved with a nameplate rating exceeding 

300 volts direct current or alternating current.

    (b) A battery-powered machine shall not have a nameplate rating 

exceeding 240 volts, nominal (120 lead-acid cells or equivalent).

    (c) Other direct-current machines shall not have a nameplate rating 

exceeding 550 volts.

    (d) An alternating-current machine shall not have a nameplate rating 

exceeding 660 volts, except that a machine may have a nameplate rating 

greater than 660 volts but not exceeding 4,160 volts when the following 

conditions are complied with:

    (1) Adequate clearances and insulation for the particular voltage(s) 

are provided in the design and construction of the equipment, its 

wiring, and accessories.

    (2) A continuously monitored, failsafe grounding system is provided 

that will maintain the frame of the equipment and the frames of all 

accessory equipment at ground potential. Also, the equipment, including 

its controls and portable (trailing) cable, will be deenergized 

automatically upon the occurrence of an incipient ground fault. The 

ground-fault-tripping current shall be limited by grounding resistor(s) 

to that necessary for dependable relaying. The maximum ground-fault-

tripping current shall not exceed 25 amperes.

    (3) All high voltage switch gear and control for equipment having a 

nameplate rating exceeding 1,000 volts are located remotely and operated 

by remote control at the main equipment. Potential for remote control 

shall not exceed 120 volts.

    (4) Portable (trailing) cable for equipment with nameplate ratings 

from 661 volts through 1,000 volts shall include grounding conductors, a 

ground check conductor, and grounded metallic shields around each power 

conductor or a grounded metallic shield over the assembly; except that 

on machines employing cable reels, cables without shields may be used if 

the insulation is rated 2,000 volts or more.

    (5) Portable (trailing) cable for equipment with nameplate ratings 

from 1,001 volts through 4,160 volts shall include grounding conductors, 

a ground check conductor, and grounded metallic shields around each 

power conductor.

    (6) MSHA reserves the right to require additional safeguards for 

high-voltage equipment, or modify the requirements to recognize improved 

technology.