What is a Lockout Tagout (LOTO) procedure? Steps and hazards

Lockout/tagout (LOTO) is a procedure for isolating and securing a machine’s hazardous energy sources before servicing or maintenance. It prevents unexpected start-up or the release of stored energy while someone is working on the equipment. Switching a machine off is not the same as isolating its energy.

This guide covers energy isolation, verification, maintenance and return to service. It is an overview, not a machine-specific work instruction: trained, authorised personnel must follow their employer’s approved procedure and the rules that apply to the equipment and location.

What is a Lockout Tagout procedure?

Lockout/tagout (LOTO) is a set of procedures that are used to ensure that equipment is shut down, inoperable, and (where relevant) de-energised. This allows maintenance and repair work on the system to be performed safely. Any workplace scenario involving equipment that could lead to the inadvertent release of hazardous energy requires the use of lockout/tagout procedures. In this context, “hazardous energy” includes not only electricity but other forms of energy such as pneumatic pressure, hydraulic pressure, and gas. The purpose of LOTO procedures is both to prevent direct exposure to this energy, as well as to prevent harm caused by any machinery or objects that could be moved by that energy (e.g., a pneumatic press accidentally being activated).

Lockout vs. tagout: what is the difference?

Lockout physically secures an energy-isolating device in a safe position. The energy-isolating device can be a manually operated disconnect switch, a circuit breaker, a line valve, or a block. Push buttons, emergency-stop buttons and other control-circuit switches are not energy-isolating devices. A lock on a control button is not a substitute for isolating the energy supply.

Tagout attaches a warning tag to the energy-isolating device. The tag identifies the person responsible and warns against operating the device; it does not physically prevent operation. Under OSHA 1910.147(c), lockable devices generally require lockout unless the employer demonstrates that a tagout system provides full employee protection. A tag alone is not an equivalent replacement for a lock.

LOTO procedure steps: isolation through return to service

The eight stages below cover the full workflow. OSHA 1910.147(d) separates six energy-control application steps from the later release-from-lockout process in paragraph (e). There is no universal eight-step OSHA requirement. The approved equipment-specific procedure determines the actual isolation points and verification methods.

1. Prepare and notify. Trained, authorised personnel identify every energy source on the machine—electrical, pneumatic, hydraulic, mechanical, thermal, chemical, gravity—and where each one is isolated. Tell the operators and anyone else affected that the machine is being shut down.
2. Shut down. Stop the machine with its normal stopping procedure.
3. Isolate all energy sources. Open the main disconnect, close the supply valves, disconnect other supplies. Every source, not only the main switch.
4. Apply locks and tags. Each person working on the machine puts their own personal lock on each isolation point (or on a group lock box when many people are involved), with a tag showing name, date and reason.
5. Release or restrain stored energy. Follow the approved method to relieve, disconnect, restrain or otherwise render stored energy safe. This may involve bleeding pressure, discharging capacitors or blocking raised parts. If energy can reaccumulate, continue verifying isolation until the work is complete or the risk no longer exists.
6. Verify isolation before work. Use the verification methods specified for every energy source. A controlled start attempt may be part of this check; return controls to off afterwards. Electrical testing must be carried out by appropriately qualified personnel with suitable equipment. A machine that does not start, or a gauge reading zero, is not by itself proof that every hazardous energy source is controlled.
7. Do the work.
8. Restore equipment to service. Follow the approved release procedure: remove nonessential items, refit guards and check that equipment is operationally intact and everyone is safely positioned. Normally, each person removes their own lock; removal by someone else requires the employer’s specific documented exception procedure. Notify affected employees after devices are removed and before restarting. Restore energy and return the equipment to service according to the approved procedure.

What should a machine-specific LOTO procedure include?

A useful procedure identifies the exact equipment, the task and the people authorised to perform it. Record:

• Every hazardous energy source, its type and magnitude, and the exact isolation device and location.
• The shutdown sequence and the devices needed to lock or secure each isolation point.
• How to control stored energy and any risk of energy reaccumulating.
• How isolation is verified for each source, including required test equipment and qualifications.
• Responsibilities for group work, contractors and shift changes, where applicable.
• The checks and notifications required before removing locks and restoring service.

Photographs or video can make an isolation point easier to identify, but the procedure must still specify the safety actions and verification criteria. Have the employer’s safety specialist review it before use.

Example LOTO verification checklist

Adapt this outline to an approved equipment-specific procedure; it is not permission to start maintenance.

• Equipment identifier, task, procedure version and authorised personnel recorded.
• Affected employees notified and normal shutdown completed.
• Every listed energy source isolated and the required locks and tags applied.
• Stored energy controlled and reaccumulation checks established where needed.
• Isolation verified for every source; method, result, person and time recorded.
• Before return to service: equipment checked, guards restored and people safely positioned.
• Locks removed under the approved procedure and affected employees notified before restart.

A completed checklist records checks; it does not replace physical isolation, training or verification.

Why is LOTO important?

The use of lockout/tagout procedures is considered a critical aspect of workplace safety in any occupational setting in which workers come into direct contact with machinery or workplace equipment. In a machine shop, the size, number of moving parts, high-speed motion and sharp cutting tools of the equipment make maintenance and setup work especially risky. Accidents which can be prevented by LOTO procedures include:

• Crushing and pinch points: presses, moving axes and raised parts that drop under gravity
• Amputation: saws, power presses, shaping and bending machines that start unexpectedly
• Cuts and lacerations: rotating cutting tools and spindles
• Electric shock and electrocution: live parts in cabinets and drives
• Burns: hot surfaces, heated tools and fluids under pressure
• Fires and explosions
• Chemical exposure: coolants, solvents and pressurised lines that are opened

LOTO does not cover every machine shop hazard. Flying chips and swarf, fumes and oil mist, and repetitive strain need eye protection, extraction and good workstation design, and belong in the machine’s other work instructions.

Safety devices such as barrier guards or guarding devices are installed on systems to maintain worker safety while these systems are being operated. When activities such as maintenance, repair, or set-up; or the removal of jams, clogs or misaligned feeds are performed, these safety devices may be removed if there are other controls in place to reduce or eliminate the hazards. Having a lockout/tagout programme and procedures for these scenarios will reduce the risk of injury due to the unintended or inadvertent release of hazardous energy.

What the law requires

Requirements differ by country and activity. In the US, OSHA 1910.147 — The control of hazardous energy covers specified servicing and maintenance activities in general industry, with scope exclusions and exceptions. It requires an energy-control programme, employee training and periodic inspections; an article or checklist does not establish compliance. In the EU there is no single LOTO regulation: the employer’s obligations come from national health and safety law, which transposes EU directives such as the Use of Work Equipment Directive (2009/104/EC). Machine builders design the isolation and energy-dissipation means in line with machinery safety standards such as EN ISO 14118 on the prevention of unexpected start-up. Check the rules that apply in your country with your safety specialist.

Making LOTO stick: a video guide and a verification checklist

Written LOTO procedures often fail at the point of use: the isolation points are hard to find, or the person has not done it on that machine for months. Two things help:

• A video guide per machine that shows where each isolation point is, how to lock it and how to release stored energy. Seeing the actual valve or disconnect is clearer than a text description.
• A verification checklist completed every time: each isolation point locked (yes/no), stored energy released, zero energy verified and how, name and time. The checklist records what the person confirmed; it does not replace the lock.

Where REWO fits

In REWO, the LOTO procedure for each machine can be a video guide opened from a QR code on the machine, and the verification checklist a Form that records who completed it and when. When the procedure changes, the new version goes through approval and replaces the old one everywhere.

Read next: Work instructions for preventive maintenance · REWO Forms · REWO for metals