Lockout/Tagout (LOTO) Procedure Guide

What is Lockout/Tagout?

Lockout/Tagout (LOTO) is a safety procedure that ensures dangerous machines are properly shut off and unable to be started up again before maintenance or servicing work is completed. It protects workers from the unexpected energisation or startup of machinery, or the release of stored energy, which can cause serious injury or death.

In Australia and New Zealand, LOTO is mandated by AS/NZS 4024.1603 (Safety of machinery — prevention of unexpected start-up). Similar requirements exist in the US under OSHA 29 CFR 1910.147 and in Europe under ISO 14118. Non-compliance can result in serious injury, fatalities, and legal penalties.

Step 1: Notify Affected Employees

Before shutting down equipment, notify all affected employees — operators, nearby workers, and supervisors — that the machine will be locked out. Explain what work is being done, how long it will take, and which alternative equipment they should use. This prevents confusion and ensures no one attempts to operate equipment that is under maintenance.

Step 2: Identify All Energy Sources

Identify every energy source that could potentially harm the worker. This goes beyond just the electrical supply — industrial equipment often has multiple energy sources:

• Electrical — main power, control circuits, backup power, UPS, capacitors (can hold charge after disconnect)
• Pneumatic — compressed air in lines, receivers, and actuators
• Hydraulic — pressurised fluid in cylinders, accumulators (can hold pressure for extended periods)
• Thermal — hot surfaces, hot fluids, steam (allow time to cool or verify temperature)
• Stored mechanical energy — springs, flywheels, counterweights, raised loads
• Potential energy — gravity (raised equipment that could fall), pressure (pressurised vessels)
• Chemical — process fluids, gases, residues in pipes that could be released
• Radiation — UV, infrared, microwave, nuclear (if applicable)

Step 3: Shut Down the Equipment

Shut down the equipment using the normal shutdown procedure specified by the manufacturer. Do not use emergency stops for routine shutdown — E-stops may not properly sequence the shutdown and could leave the equipment in an unsafe state. If the equipment is already stopped, verify it is in a safe position for maintenance (not mid-cycle, no suspended loads).

Step 4: Isolate All Energy Sources

Operate the energy-isolating devices for each identified energy source:

• Open the main electrical disconnect switch (not the start/stop button — the main isolator)
• Close block valves on pneumatic and hydraulic supply lines
• Open bleed/drain valves to release stored pneumatic/hydraulic pressure (verify pressure = 0 on gauges)
• Release mechanical stored energy — lower raised loads, release spring tension, allow flywheels to stop
• Block or restrain components that could move under gravity (raised ram, counterweight)

Step 5: Apply Locks and Tags

Each authorised worker applies their own personal padlock to each energy-isolating device. The lock must be uniquely keyed — no master keys, no shared keys. A tag identifying the worker, the date, and the work being done is attached to each lock.

Step 6: Verify Zero Energy

This is the most critical step — and the most frequently skipped. After all locks are applied, verify that the equipment is de-energised:

1. Attempt to start the equipment using the normal start controls. If it starts, you have missed an energy source — go back to Step 2.
2. Return the start control to the off/neutral position.
3. Test for voltage at the motor terminals using a verified voltage tester.
4. Verify zero pressure on all pneumatic/hydraulic gauges.
5. Verify the temperature of hot surfaces is below the safe threshold.
6. Verify no stored mechanical energy remains (springs relaxed, loads supported, flywheels stopped).

Restoring Equipment After Maintenance

Removing locks requires its own procedure to ensure no one is inside or near the equipment when it starts:

1. Ensure all tools, materials, and personnel are clear of the equipment.
2. Reinstall all guards, covers, and safety devices.
3. Close all drain/bleed valves that were opened for isolation.
4. Verify the equipment controls are in the off/neutral position.
5. Each worker removes their own personal lock(s). No worker may remove another worker's lock.
6. Notify affected employees that the equipment is being returned to service.
7. Restore energy sources one at a time, verifying correct operation.

Building a LOTO Programme

• Develop written machine-specific LOTO procedures for each piece of equipment — generic procedures are not sufficient.
• Train all authorised workers (those who apply locks) and affected workers (those who operate near locked-out equipment).
• Use standardised, uniquely keyed padlocks — colour-coded by department or worker type.
• Conduct annual audits of LOTO procedures to verify compliance and identify gaps.
• Maintain a master list of all authorised workers and their lock assignments.
• Never — under any circumstances — remove another worker's lock without following the emergency lock removal procedure (which requires contacting the worker, verifying their safety, and documenting the removal).