Lockout is the process of isolating equipment from every energy source and securing those isolation points with personal locks so the equipment cannot start or release energy while someone is working on it. Tags identify who applied the lock and why, but a tag alone does not stop anyone. Every province requires hazardous energy to be controlled before work on machinery or equipment, and CSA Z460 sets out good practice.
Why it matters
Unexpected start-up or release of stored energy during maintenance causes amputations, crushing injuries, burns, electrocution and deaths. Many of these happen during routine tasks: clearing a jam, cleaning a conveyor, changing a belt. The worker assumes the machine is off because the switch is off, or because someone said it was.
Know all the energy sources
Electricity is the obvious one, but equipment often has several sources, some of them stored:
- Electrical: supply circuits, control circuits, capacitors, batteries.
- Mechanical: moving parts, flywheels, springs under tension, raised loads.
- Hydraulic and pneumatic: pressurized lines, accumulators, cylinders that can drift.
- Thermal: steam, hot water, hot surfaces.
- Chemical: process lines carrying hazardous materials.
- Gravity: parts that can fall or move when supports are removed.
Our guide to compressed air system safety covers one of the energy sources people most often forget.
The steps of a lockout
- Prepare. Identify the equipment and every energy source, using the equipment-specific procedure. Know how each will be isolated and how stored energy will be released.
- Notify. Tell operators and others affected that the equipment is being shut down and locked out.
- Shut down using the normal stopping procedure.
- Isolate every energy source at its isolating device: disconnect switch, breaker, valve, blank or blind. Control circuits and push buttons are not isolating devices.
- Apply locks and tags. Each worker applies their own personal lock, directly or through a group lockout box. Only the person who applied a lock should remove it.
- Release stored energy. Bleed pressure, block or lower raised parts, discharge capacitors, let moving parts come to rest, drain lines.
- Verify. Confirm the equipment is at zero energy. Try the start controls with everyone clear, test for absence of voltage with a suitable tester by a qualified person, check gauges. Return controls to off afterwards.
- Do the work.
- Restore. Remove tools, replace guards, check that everyone is clear, notify affected people, then remove locks in the proper order and re-energize.
Verification is the step that saves lives. Mislabelled breakers, shared feeds and backfeeds are common. Never assume isolation worked; prove it before anyone touches the equipment.
Program elements
A lockout program usually includes:
- A written policy and general lockout procedure
- Equipment-specific procedures, with isolation points identified and labelled
- Personal locks, keyed individually, issued to each worker, with tags
- Group lockout procedures for jobs involving many workers or isolation points
- Rules for shift changes, so protection is never interrupted
- A controlled process for removing a lock when its owner is not available
- Training for authorized workers and awareness for affected workers
- Periodic review and audit of procedures in use
Situations that need extra care
Group lockout
When many workers are protected by the same isolation, a group lockout box lets each person apply their own lock to the box holding the keys to the isolation locks. Nobody is protected unless their own lock is on.
Contractors
Contractors must follow your lockout rules or an agreed equivalent, and everyone must understand whose locks go where. See managing contractor safety.
Work where energy is needed
Some testing, adjustment and troubleshooting cannot be done with the equipment fully de-energized. These tasks need alternative safe work procedures, and for electrical work, the energized work requirements of CSA Z462, which covers arc flash and shock hazards. Only qualified workers should do such work.
Lock removal by someone else
If a worker leaves the site with their lock on, removal should follow a written procedure: confirm the worker is not on site, make sure the equipment is safe, have an authorized person remove the lock, and tell the worker before they return to work.
How ehZee can help
ehZee helps employers write and review lockout programs and equipment-specific procedures, with input from our building systems inspection work on mechanical and electrical equipment. See safety program development and review.
Common questions
Is a tag enough if a lock will not fit?
Tags alone give much weaker protection. Most rules require a lock wherever the isolating device can accept one, using adaptors such as breaker lockouts and valve covers. Where a lock truly cannot be applied, your provincial rules and procedure set out what additional measures are needed.
Can a supervisor lock out for the whole crew?
Generally each worker should apply their own personal lock so they control their own protection. Group lockout methods allow this without each person locking every isolation point.
Does unplugging a cord-connected tool count?
Unplugging can be an acceptable isolation for cord-and-plug equipment when the plug stays under the exclusive control of the person doing the work. Check your procedure and provincial rules.