Lockout and tagout: preventing hazardous energy release

Proper lockout and tagout procedures can prevent the unexpected startup or release of stored energy in machines and equipment.

Construction sites contain powerful sources of hazardous energy—many of them found in the equipment, machines, and systems workers use every day. Energy is often present in the form of electricity, of course, but there’s also the energy created by pressurized air or liquid in pneumatic and hydraulic equipment, the mechanical energy of moving parts, the energy of chemical reactions, and more.

If this energy is released unexpectedly while a worker is cleaning, maintaining, or servicing equipment, they could be seriously injured or killed.

An effective way to prevent the release of hazardous energy is with lockout and tagging, which ensures de-energized equipment can’t be returned to operational service without the approval and action of authorized workers.

What is lockout and tagout?

Before an energized machine, piece of equipment, or system can be maintained or repaired, its energy must be isolated— that is, disconnected from its source. Lockout is the act of placing a physical lock or locks on the energy-isolating device: while the lock is engaged, the equipment can’t be turned on.

Tagout (a.k.a. tagging) involves attaching a warning label to the locked-out equipment to tell others who performed the lockout and why. Note that tagging on its own does not control hazardous energy release: simply applying a cautionary tag to equipment doesn’t guarantee that it’s isolated from its energy source. Always perform tagging with lockout.

Lockout/tagout regulations and standards

Both the Regulation for Construction Projects (O. Reg. 213/91) and the Regulation for Industrial Establishments (R.R.O. 1990, Reg. 851) specify various requirements for controlling hazardous energy in the industries IHSA serves.

Section 190 of O. Reg. 213/91, for example, lists requirements for lockout and tagging. Among them is the need for employers to have written procedures that protect workers from electrical shock and burn. A copy of those procedures must be made available to workers on site.

Additionally, the Canadian Standards Association standard, CSA Z460-20: Control of hazardous energy – lockout and other methods, outlines how to identify hazardous energy sources and their risks.

Because multiple types of hazardous energy can be present in equipment, being able to identify them is very important. Consider an excavator, which may have electrical energy (battery and ignition system), hydraulic energy (to move the boom, arm, and bucket), and mechanical energy (moving parts and suspended loads). Before servicing that machine, workers need to ensure all hazardous energy is controlled—by isolating, locking out, and releasing stored energy—to prevent unexpected startup or movement.

Lockout and tagout steps

There are a handful of steps to planning and performing a lockout:

1. Locate the work area and identify the equipment.
2. Identify all energy sources affecting the equipment. Consider both direct and indirect energy sources and all possible types of energy (e.g., electrical, pneumatic, thermal, etc.).
3. Identify the parts to be locked out. Include all systems affected by the work, including primary, backup, and emergency systems. Confirm the location of any energy-isolating devices, such as switches, power sources, controls, and interlocks. Consider whether any equipment or system components operate on an automated timer.
4. Determine lockout methods. Confirm that the lockout of all energy sources is possible. In some cases, equipment can’t be completely shut down because it supplies power to other systems. Identify these connections when planning the lockout.
5. Notify affected personnel. Inform all workers, shifts, and trades who might plan to operate the locked-out system. Jobsites with a large number of workers may need to establish a formal system to ensure lockouts are consistently communicated and understood.
6. Shut down the equipment. A qualified person (or persons) must shut down the equipment, machinery, or system and physically disconnect—or otherwise isolate—all energy sources.
7. Install lockout devices. Each worker involved in the lockout must apply their own personal lock to the isolating device. Each worker must keep their own personal key. Locks should be high-quality pin-type, key-operated, and numbered to identify their owner. Only the person who supplied the locks and tags can remove them.
8. Tag the lockout devices. Tags are visual reminders to all workers that the locked-out equipment must not be energized or operated. Each tag must specify the name and employer of the person who applied the lock, as well as the date and reason for the lockout. Tags must also be made of non-conductive material, clearly visible, and secured so they won’t fall off.
9. Verify zero-energy state. Before work can begin on the locked-out machine, equipment, or system, you must confirm that stored energy has been released and the machine cannot be reenergized. With all personnel clear of the equipment, try to start it manually. If no movement or function is observed, it should be safe to carry out the work.
10. Service the equipment and safely restart. Always follow the manufacturer’s procedures for safely restarting the equipment.

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