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MSHA -  Title 30 CFR

30 CFR § 75.831
Electrical work; troubleshooting and testing.


    (a) Trailing cable and continuous mining machine electrical work procedures. Prior to performing electrical work, other than troubleshooting and testing, on the high-voltage trailing cable or the continuous mining machine, a qualified person must de-energize the power center and follow procedures specified in paragraph (1) or (2):

   (1) If a trailing cable disconnecting switch is provided:

   (i) Open and ground the power conductors, lock out and tag the disconnecting switch; and

   (ii) Lock out and tag the plug to the power receptacle.

   (2) If a trailing cable disconnecting switch is not provided and a cable coupler is used as a disconnecting device:

   (i) Remove the plug from the power receptacle and connect it to the grounding receptacle;

   (ii) Lock out and tag the plug to the grounding receptacle; and

   (iii) Place a dust cover over the power receptacle.

   (b) Troubleshooting and testing the trailing cable. During troubleshooting and testing, the de-energized high-voltage cable may be disconnected from the power center only for that period of time necessary to locate the defective condition. Prior to troubleshooting and testing trailing cables, a qualified person must perform the following:

   (1) If a trailing cable disconnecting switch is provided:

   (i) Open and ground power conductors and lock out and tag the disconnecting switch;

   (ii) Disconnect the plug from the power receptacle;

   (iii) Lock out and tag the plug; and

   (iv) Place a dust cover over the power receptacle.

   (2) If a trailing cable disconnecting switch is not provided and a cable coupler is used as a disconnecting device:

   (i) Remove the plug from the power receptacle and connect it to the grounding receptacle to ground the power conductors;

   (ii) Remove the plug from the grounding receptacle and install a lock and tag on the plug; and

   (iii) Place a dust cover over the power receptacle.

   (c) Troubleshooting and testing limitations. Troubleshooting and testing energized circuits must be performed only:

   (1) On low- and medium-voltage circuits;

   (2) When the purpose of troubleshooting and testing is to determine voltages and currents;

   (3) By qualified persons; and

   (4) When using protective gloves in accordance with the following table:

Circuit voltage Type of glove required
Greater than 120 volts (nominal) (not intrinsically safe) Rubber insulating gloves with leather protectors.
40 volts to 120 volts (nominal) (both intrinsically safe and non-intrinsically safe) Either rubber insulating gloves with leather protectors or dry work gloves.
Greater than 120 volts (nominal) (intrinsically safe) Either rubber insulating gloves with leather protectors or dry work gloves.


   (d) Power center electrical work procedures. Before any work is performed inside any compartment of the power center, except for troubleshooting and testing energized circuits as specified in paragraph (c) of this section, a qualified person must:

   (1) De-energize affected circuits;

   (2) Open the corresponding disconnecting switch, lock it out, and tag it to assure the circuit is isolated;

   (3) Visually verify that the contacts of the disconnecting switch are open and grounded; and

   (4) Discharge all high-voltage capacitors and circuits.

   (e) Locking out and tagging responsibilities.

   (1) When more than one qualified person is performing electrical work, including troubleshooting and testing, each person must install an individual lock and tag. Each lock and tag must be removed only by the persons who installed them.

   (2) If the person who installed the lock and tag is unavailable, the lock and tag may be removed by a person authorized by the operator, provided that:

   (i) The authorized person is a qualified person; and

   (ii) The mine operator assures that the person who installed the lock and tag is aware that the lock and tag have been removed.