Lockout/Tagout procedures: controlling hazardous energy and correct use of locks and tags

Lockout/Tagout, often shortened to LOTO, is an essential safety procedure for maintenance, repair and servicing work. It is used to control hazardous energy before work starts, so equipment, piping or vessels cannot unexpectedly start, move, release pressure or expose workers to dangerous substances.

Hazardous energy is not limited to electricity. It can also include mechanical movement, hydraulic pressure, pneumatic pressure, steam, chemicals, heat, stored pressure or gravity. In process environments, piping and vessels can contain energy even after equipment has been shut down. This is why isolation, verification and clear communication are critical parts of safe work preparation.

Why Lockout/Tagout matters

The main purpose of Lockout/Tagout is to create a controlled condition before work begins. This is often referred to as a zero energy state. Reaching this condition means that all relevant energy sources have been identified, isolated, locked, tagged and checked before anyone starts the task.

A written procedure helps prevent assumptions. It makes clear which equipment is involved, which isolation points must be used, who is authorized to apply locks and tags, and how the system may be returned to service. Occupational health and safety guidance identifies lockout/tagout as part of controlling hazardous energy and highlights the need for procedures to protect workers from energized circuits and unexpected energy release.

Locks provide physical control

A lockout device is used to physically prevent equipment or an energy isolation point from being operated. This can apply to a valve, switch, breaker, blind, disconnect or another isolation device.

Each authorized worker should have personal control over their own lock. This is important because the lock represents direct protection for that person. The lock should only be removed according to the approved procedure, normally by the person who applied it. When several people work on the same system, group Lockout/Tagout arrangements may be needed so every worker remains protected throughout the job.

Correct use of locks is not just a technical action. It is also a communication step. A lock shows that work is in progress and that the equipment must not be operated.

Tags provide clear warning

A tagout device warns others that equipment, piping or an isolation point must not be operated. Tags usually show who applied the tag, why it was applied and what equipment or system it relates to.

Tags are important, but they do not provide the same physical protection as locks. A tag communicates a warning; a lock prevents operation. For this reason, tags must be clear, securely attached and used as part of a wider energy control procedure. Everyone involved in the work must understand what the tag means and what actions are prohibited.

Verification is the critical step

One of the most important parts of Lockout/Tagout is verification. Shutting down equipment is not enough. Workers must confirm that hazardous energy has actually been isolated, released, blocked or controlled.

In piping and vessel isolation, this can include checking pressure, draining or venting lines, confirming valve positions, installing blinds or other isolation controls, and ensuring that stored energy cannot return during the work. A system should not be treated as safe until the isolation has been verified.

This step is especially important during shift changes, group work and work involving contractors. If responsibility is transferred without clear communication, there is a risk that locks, tags or isolation points are misunderstood.

Returning equipment to service

Lockout/Tagout does not end when the maintenance task is finished. Returning equipment to service also requires control. Tools and materials must be removed, guards and covers must be replaced where applicable, workers must be clear of the danger area, and all locks and tags must be removed according to the site procedure.

Only after these checks should equipment, piping or vessels be re-energized or returned to operation. This controlled restart helps prevent incidents after the work has been completed.

Training supports safe performance

Lockout/Tagout procedures depend on people understanding their responsibilities. Workers need to know when LOTO is required, how hazardous energy is identified, how locks and tags are applied, and how isolation is verified. Supervisors and maintenance teams also need to understand how the procedure fits into permits, shift handovers and restoration to service.

FMTC offers the Lockout Tagout Piping and Vessel Isolation E-learning course for personnel who need to understand hazardous energy control in relation to process equipment, piping and vessel isolation. FMTC’s knowledge structure describes e-learning as a fully digital training form, while the wider OSHA and General HSE course category is positioned around workplace safety and compliance in industrial environments.

Practical next step

Lockout/Tagout is only effective when it is applied consistently. Before starting work, make sure the correct isolation points are known, locks and tags are used correctly, and the zero energy state is verified.

For more information or to arrange training, view the FMTC course: Lockout Tagout Piping and Vessel Isolation E-learning.