Lock-Out / Tag-Out (LOTO)

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Overview

LOTO positively isolates every energy source and proves it dead before work.

Energy types to isolate

Electrical — breakers and disconnects.
Mechanical & rotating — drives, conveyors.
Pressure — hydraulic, pneumatic, process.
Thermal and chemical.
Stored — springs, raised loads, capacitors.

The six LOTO steps

Prepare — identify the equipment and all energy sources.
Shut down using the normal stop procedure.
Isolate — physically separate each source.
Lock and tag each isolation point.
Release/restrain stored energy.
Verify zero energy (try-to-start, test for dead).

Group isolation & restoration

Each worker applies their own lock.
Use a group lock box for many workers.
Re-energize only when all locks are removed and area is clear.

Roles & responsibilities

Role	Responsibility
Authorized isolator	Carries out and documents isolations.
Each worker	Applies/removes their own lock only.
Supervisor	Confirms zero-energy verification.

Common mistakes to avoid

Tagging without locking.
Forgetting stored energy.
Skipping the zero-energy verification.

Legal requirements (Thailand)

Occupational Safety, Health and Environment Act B.E. 2554 (2011) — the governing workplace-safety law in Thailand.
Ministerial Regulation on OSH for machinery, cranes and boilers B.E. 2564 (2021).
Ministerial Regulation on OSH for electrical work B.E. 2558 (2015).

Frequently asked questions

What is Lock-Out / Tag-Out (LOTO)?

The most dangerous moment in maintenance is when stored or supply energy is released without warning. LOTO is the disciplined process that makes equipment safe to work on by positively isolating every energy source and proving it is dead before hands go near it.

Who is responsible?

Authorized isolator: Carries out and documents the isolations.; Each worker: Applies and removes their own lock — no one else may.; Supervisor: Confirms zero-energy verification before work starts.

What are the most common mistakes to avoid?

Tagging without locking — a tag alone does not prevent re-energization. Forgetting stored energy (trapped pressure, raised loads, capacitors). Skipping the try-to-start / test-for-dead verification.

References — Company isolation procedure; control of hazardous energy; Thai OSH Act B.E. 2554.