The Mine Safety and Health Administration, or MSHA, has an established list of procedures to be used when working on electrical equipment in mines and mine related industries. These regulated procedures have been put in place to decrease the risk of accidental electrical injury and death. MSHA is a federal government agency and the compliance with its procedures is regulated by law. Disregard of the lock-out procedures is grounds for dismissal in most mines and plants.
These steps are to be followed before performing any electrical work:
1. Determine the location of the disconnecting means for the circuit to be worked on
2. Carefully de-energize the circuit
3. Each employee working on the circuit should place his/her own lock and tag on the disconnecting device
4. The circuit to be worked on should be tested for voltage to ensure no electricity is present
Additionally, the following step is recommended by MSHA as a safety net in case someone accidentally removes a lock.
5. Ground all the phase conductors to the equipment grounding conductor with a jumper
The on/off switch for most industrial equipment is a lever arm. The locks are applied in a way so that the lever cannot be moved from the off position to the on position without first removing the lock. Thus, when an electrician applies his lock onto the drive of a machine, he can be assured of his own safety because power cannot be restored to the equipment until his personal lock is removed. This is important because the drives are often located far away from the actual equipment, protecting them from the harsh plant environment, but also keeping them out of sight of the electrician.