#81 Uncontrolled Sources of Energy

Unprotected sources of stored energy can be very hazardous to mechanical construction workers. Examples of stored energy that might be encountered on a jobsite are:

  • Electrical (such as panel boxes)
  • Mechanical (such as mechanical jacks)
  • Hydraulic (such as an aerial lift)
  • Pneumatic (such as an air compressor)
  • Thermal (such as steam lines)


Workers can be protected from these hazards if the sources of energy are locked out and tagged out. “Lockout” means that the source of energy cannot be turned on because a locking device has been placed on the switch, lever, and valve, etc. “Tagout” means there is a warning tag attached to the energy source controls to stop others from turning on the source of energy.


If a mechanic has to perform maintenance or repair on any machinery, equipment or process with stored energy, it should be locked out and tagged out. Only qualified mechanics should engage in lockout/tagout operations.


Electricity should be locked out or tagged out at the panel box.


Steam, hydraulic and air-line systems should be shut off and bled out. Otherwise, even when the valves are in the off position, there is still hazardous energy stored in the pipes. The valves should be locked out and tagged out.


Only the mechanic who locked out or tagged out a source of energy should remove the lock and tag.


Always make sure the procedures comply with the company’s lockout/tagout problem.