What is a Lockout/Tagout?

Understanding Lockout/Tagout

Lockout/Tagout is a controlled method for stopping hazardous energy during service work. Hazardous energy includes electricity, compressed air, hydraulic pressure, steam, gravity, heat, and stored mechanical force. A shutdown switch may stop normal operation. It may not remove every energy source that can injure a worker.

Related glossary terms: Electrical Grounding, Line Voltage, Overcurrent.

The process uses an energy isolation device, a personal lock, and an identification tag. The lock keeps a disconnect, valve, breaker, or similar device safe. The tag identifies the worker. It warns others not to operate the equipment. A tag without a physical lock offers limited protection. This applies unless a specific procedure and authorized exception apply.

How Lockout/Tagout Works, Is Measured, or Is Used?

A typical procedure begins with an energy review and a shutdown notice. An authorized worker turns off the equipment. The worker disconnects every known energy source. The worker applies a lock and tag. The worker releases or blocks stored energy. Stored energy may remain in capacitors, elevated parts, rotating assemblies, pressurized lines, or heated components.

Verification is the critical final check before work starts. The worker attempts a normal start from the controls. The worker tests electrical circuits with properly rated test equipment. The worker confirms that movement, pressure, voltage, and other hazards are absent. The worker then returns controls to the off position. After service ends, each worker removes their own lock. They check that tools are clear and guards are restored. They also check that people are outside the danger area.

Complex work may require a lock box, group locks, or a written energy control procedure. A qualified person should identify every isolation point. They should use drawings, labels, field inspection, and equipment instructions. The procedure is measured by its accuracy and verification. It isn't measured by the number of locks used. A missing energy source can leave a system dangerous. This can happen when the main disconnect appears open.

Why Lockout/Tagout Matters?

Unexpected energization can cause electric shock, arc flash burns, amputation, crushing injuries, or fatal contact with moving equipment. Normal controls don't always stop automatic cycles, remote commands, backfeed, or stored system energy. Lockout/Tagout creates a physical barrier between the worker and the energy source.

Effective procedures also improve maintenance decisions. They show which disconnects, breakers, valves, and blocking points control the equipment. Records, training, and periodic inspections help an employer find weak steps. They can find these steps before an incident occurs. OSHA requires covered employers to establish energy control procedures. Employers must train affected workers. They must inspect procedures at least annually.

When Lockout/Tagout Matters Most?

Lockout/Tagout matters whenever a worker must remove a guard or enter a danger zone. It also matters when workers reach into equipment or replace wiring. It applies when workers open an electrical enclosure or service a circuit. The circuit could start unexpectedly. It applies to planned maintenance and many urgent repairs. Time pressure doesn't remove the need to identify and isolate energy.

Extra care is needed during troubleshooting, generator work, transfer switch service, industrial panel repairs, and repairs involving multiple crews. Testing may require temporary energization under a controlled procedure. Workers must de-energize equipment before physical work resumes. For electrical tasks, the worker must also account for backfeed, alternate supplies, batteries, capacitors, and live circuits. These circuits may stay live after one disconnect opens.