MRO Magazine

Stop the Power: Tips for energy control


September 14, 2001
By PEM Magazine

It’s 3:00 a.m. on Tuesday morning and Tom, the night-shift millwright in the maintenance department of an automotive parts supplier manufacturer, receives a call from a line supervisor. A section of a conveyor line has stopped working, and product is backing up. In his troubleshooting task, Tom has determined that there is a faulty chain drive which is coupled to a three-phase motor. He informs the line supervisor that an entire section of the line will be shut down while he performs the necessary repair. While Tom performs the work, a line worker who is unaware of the problem energizes the disconnect switch supplying the conveyor — and ends up requiring hospitalization for the resulting injuries to his right hand.

Uncontrolled energy sources kill or seriously injure hundreds of Canadian workers every year. The above accident didn’t just happen as a result of failure to communicate between the maintenance worker and the line supervisor, or between the line supervisor and the other worker. It happened because of the lack of a comprehensive, effective lockout-tagout program.

A proper electrical and mechanical lockout-tagout procedure will ensure that the equipment or machinery requiring servicing is de-energized, isolated and locked out from all sources of energy prior to any repair or maintenance work being conducted. It also prevents the inadvertent start-up of the equipment or machine. The control or release of any stored energies must also be applied.

There are two common misconceptions of lockout?±tagout, one being that it only involves the electrical system, and the other that lockout-tagout procedures only pertain to the maintenance department — the electricians, millwrights or industrial mechanics. Many workers are aware that they have to shut the power off on a machine before working on it (this involves the physical interruption of the line conductors feeding the motor, a stop pushbutton or an interlock are not acceptable means). However, that machine may be supplied by pneumatic, hydraulic or steam energy, all of which can be as lethal as electricity. Gravity, too, is a source of potential energy capable of causing injury.


Lockout-tagout programs involve more than just the maintenance department. Other workers such as operators, tool set-up, sanitation and mixing room workers need to know:

  • The characteristics of the machine or equipment;
  • How it operates;
  • What hazards are involved;
  • What specific steps to follow when something breaks down; and
  • What not to do before, during and after a shutdown.

Some companies have adopted a "six-step procedure" (Prepare for shutdown; equipment shutdown; isolate equipment from energy sources; apply lockout-tagout devices; control or release stored energy; verify). Unfortunately those six steps are not specific enough to provide adequate protection to the worker. An energy control lockout-tagout procedure must be adapted to each piece of equipment in the plant. This lists the sources of energy, the magnitude, the location of the isolating device(s), the method of lockout-tagout and how to verify. An energy control lockout-tagout placarding system is an excellent method for providing a visual aid coupled with online instructions on how to safely isolate and lock out the piece of equipment.

Under OSHA Regulations — CFR 1910-147, an energy control placarding system is mandatory on every piece of equipment in the plant that has multiple primary energy sources (two or more), or equipment where the main electrical disconnect switch is not within the "line of sight."

A circuit breaker lockout-tagout device is shown above. Section 42 (1) Regulation 851 ?± Industrial Establishments requires that the power supply to electrical installations, equipment or conductors be disconnected, locked out and tagged before any work is conducted.

Devices such as the gate valve lockout-tagout device make lockout-tagout more convenient for the worker.


  • Must be made by a reputable manufacturer and provided by the employer. This is to preclude workers from using inferior locks, which can be tampered with or opened by other keys.
  • Combination locks or locks with duplicate keys are not recommended.
  • Locks used for lockout-tagout purposes must be used for that purpose only — not for tool boxes, lockers or storage sheds.
  • Should be checked when purchased to ensure that no two or more locks can be opened by the same key.
  • May issue each authorized employee their own personal lock(s) imprinted with their name, lock number or department.
  • Some companies may have the company name or insignia stamped on it.
  • Standardized shape and size. Colour coding may vary from department to department.

Len Cicero is a master electrician and president of Lenco Enterprises. This article first appeared in the March/April 2001 issue of Canadian Occupational Safety.