The agency said that three separate incidents at mines have resulted in miners being sent to the hospital, and all have occurred in a two-month period.

In the first, an electrician was shocked and burned while attempting to repair a damaged continuous miner cable with the circuit breaker closed and the cable coupler connected to the receptacle, and the second miner was shocked while hanging a feeder cable during a belt and power move.

“The cable, mine floor, and the miner’s gloves were wet,” MSHA said of the second event. “The feeder cable’s outer jacket and insulation were damaged.”

In the third incident, the worker was shocked while handling a roof bolter cable while the cable, mine floor and miner’s gloves were damp. Investigators found that the cable had a small hole in the outer jacket as well as a damaged conductor.

In hopes of preventing similar such events at other operations, MSHA is stressing that mines not perform any electrical work until circuits are de-energized, locked and tagged out, and that all workers be knowledgeable of the hazards of electricity and never touch any ungrounded electrical component until is it confirmed it has been de-energized.

Additionally, operations should identify all hazards in their respective mine, then develop and follow a safe plan to perform the work. Electrical measurements should also be conducted to test for unwanted electrical power, especially in areas that are wet or muddy.

Other best practices, according to the agency:

  • Always handle de-energized cable instead of energized cable, or wear properly rated and well-maintained electrical gloves when handling energized cables.
  • Conduct complete and thorough examinations on all electrical equipment to include hand-over-hand examinations of de-energized electrical cables.
  • Protect electrical cables from damage by mobile equipment and falling roof. When cable damage is suspected, immediately notify a qualified electrician so a potentially dangerous condition can be corrected.
  • Install sensitive ground fault relays with instantaneous trip setting of 125 mA or less on all face equipment. Use trailing cables with a grounded metallic shield.

A complete version of the alert is available on MSHA’s website.