LOTO (Lock Out, Tag Out)

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“To prevent accidents, it is essential to disconnect power from machinery and equipment before performing non-routine tasks, and to clearly indicate that work is in progress by following the LOTO (Lock Out, Tag Out) procedure.”

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LOTO Compliance: A Requirement, Not an Option

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Robots, conveyors, and other machinery widely used in industrial sites provide high efficiency and convenience.

However, during cleaning, maintenance, or repair work, workers are often injured—or even killed—by becoming caught in or struck by machines. Such accidents have been consistently reported every year.

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For example:

• A worker cleaning a conveyor in a metal manufacturing plant was caught and injured.

• Another worker in a metal press shop was crushed to death while removing scrap near a scrap compactor.

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The root causes were work being performed while machinery was still running, or unexpected start-up of stopped equipment. To effectively manage these hazards and prevent accidents, it is critical to cut off all energy sources and apply LOTO procedures before starting non-routine tasks.

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“LOTO is a safeguard that prevents a wide range of accidents such as entrapment, electric shock, fire, and explosion during non-routine work.”

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What is LOTO?

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LOTO is a safety procedure that isolates hazardous energy during non-routine work on machinery or equipment and communicates the work status to ensure worker safety.

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LOTO consists of two main parts:

1. Lock Out – Physically shutting off energy sources and installing lockout devices on switches, valves, or disconnect points to prevent accidental start-up.

2. Tag Out – Attaching warning tags that clearly display hazard information, work details, worker’s name, and expected completion time, alerting others not to operate the equipment.

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LOTO is more than a simple safety routine; it is grounded in technical principles. Machinery energy sources include electricity, mechanical force, hydraulics, pneumatics, chemicals, and thermal energy. Each requires specific technical measures to achieve complete isolation.

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Technical Principles of LOTO

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1. Energy Isolation and Lockout Devices

• Electrical systems: Turn off the power switch and open the circuit breaker to cut all current flow.

• Hydraulic systems: Switch off the hydraulic pump and close valves to block hydraulic pressure.

• Pneumatic systems: Shut off compressed air supply and release pressure from air tanks.

• Thermal systems: Cut off the heat source and allow equipment to cool down to a safe temperature.

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Lockout devices must be installed on circuit breakers, hydraulic valves, pneumatic shutoff valves, and heat supply units to prevent accidental restart or operation.

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2. Tagging .

During non-routine tasks, tags must be attached to lockout points with clear warnings such as “Do Not Operate – Under Inspection.” Tags should also include the worker’s name, task details, expected completion time, and warning messages to prevent unauthorized operation.

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3. Procedures and Documentation

The technical meaning of LOTO goes beyond locks and tags—it requires systematic and standardized procedures.

• Document operating procedures adapted to specific machinery and work environments.

• Ensure all workers follow LOTO consistently.

• Provide training so workers understand the importance of the procedure and can perform it correctly.

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