Isolate, de-energise, lockout and tagout plant

Workers can suffer serious injuries or die when plant accidentally activates or stored energy releases. To help keep workers safe, employers must isolate, de-energise, lockout and tagout plant before maintenance work or repairs.



This information about the need to isolate, de-energise, lockout and tagout plant aims to help workplaces develop safe isolation procedures to reduce the risk of death or injury during plant inspections, repairs, maintenance, assessments, adjustments or cleaning.

This information considers the specific legislative duties applying to employers, contractors, self-employed people, employees and people in control of workplaces or people in control of access to workplaces.

Preventing death and injuries

Plant is a general name for equipment, machinery, appliances, tools and implements. Every year, people at work are injured, sometimes fatally, when plant inadvertently activates or stored energy releases during inspection, repair, maintenance or cleaning. Introducing and following effective isolation procedures can prevent these injuries.

Plant isolation procedures

An isolation procedure is a set of steps to be followed to keep plant and its components from being set in motion or to prevent the release of stored energy, including electricity, heat, steam and fluids.

When developing plant isolation procedures, employers should consult with health and safety representatives (HSRs), plant operators and people who adjust, clean, maintain, repair or inspect the plant. If possible, plant manufacturers, suppliers and people who designed and installed the plant should also help develop the procedure. If a workplace does not have the expertise to develop procedures, the employer should engage qualified people to do so.

The effectiveness of isolation procedures relies on:

  • Having the isolation procedure documented and accessible to the relevant people in the workplace.
  • Providing information, instruction and training to workers involved with the plant.
  • Appointing a person as a supervisor to make sure the workplace strictly follows isolation procedures.

Requirement to conduct a risk assessment

Lockout and/or tagout for the isolation of plant for inspections, repairs, maintenance, assessments, adjustments or cleaning should not be undertaken until a risk assessment is completed. The risk assessment will confirm whether plant can be substituted, or whether permanently fixed guards, an interlocked system or other non-administrative guarding systems are reasonably practicable methods to remove all sources of energy from the plant to make it safe. If those methods are not reasonably practicable, then a lockout and/or tagging out is an option for the isolation of plant for inspections, repairs, maintenance, assessments, adjustments or cleaning.

Requirement for interlocked guarding

For effective isolation, de-energising, lockout and tagout of plant, the plant should, where reasonably practicable, be interlocked in accordance with the guarding hierarchy of controls outlined in the Occupational Health and Safety Regulations 2017 (OHS Regulations 2017). See the Compliance code: Plant for more information about the guarding hierarchy.

Interlocked guards

An interlocked guard - 'the interlock' - is a barrier connected to the plant's power or control system. The interlock prevents the plant from operating unless the guard is closed. The interlocking system may be mechanical, electrical, hydraulic, pneumatic or a combination of these systems.

Where reasonably practicable, interlocked guards should be part of a plant's isolation controls.

Interlock guards work with an interlocking device so that, together with the plant's control system, they can have a number of the following functions:

  • The hazardous areas covered by the guard cannot operate until the guard is closed.
  • If the guard is opened while hazardous plant functions are operating, a stop command will either shut off the power to the guarded area, or effectively isolate the area being guarded.
  • The interlocking system incorporates 'run-down' guards that close and lock and remain locked until the risk associated with the guarded hazardous function has disappeared. This type of interlocking guard is recommended when moving parts take time to come to rest.
  • When the guard is closed, the hazardous machine functions covered by the guard can operate, but closing the guard does not by itself start the hazardous plant function. In this case the plant must be manually restarted via appropriate operator controls.

Interlocked guards are ideal for situations where regular operational access to the guarded area is required, for example, to clear jammed material or loading materials into a machine, as long as:

  • The interlocking system is reliable or has a back-up system.
  • The interlocking system is designed to be 'fail safe'. If there is a failure in the interlocking system, the machine cannot operate.
  • Where the guarded danger areas take time to come to rest, the interlocking system prevents access to the danger area until any moving parts have stopped.

Where guards are power operated, the employer should consider any hazards introduced by the powered movement of the guard.

Isolation procedure

Isolation procedures in each workplace may vary because of differences in plant, power sources, hazards and processes. However, every isolation procedure should include the following basic steps:

If plant isolation is not practicable

There may be plant that can only be cleaned, maintained, repaired or adjusted by moving components slowly under power. In this case, the plant should be fitted with controls that allow safe, controlled movement. Employers must develop safety procedures in consultation with HSRs, people who adjust, clean, maintain, repair or inspect the plant and the plant operators. Employers should make sure procedures are strictly followed.

Legal requirements

Employers have responsibilities under the Occupational Health and Safety Act 2004 to ensure they provide a work environment that is safe and without risks to health, so far as is reasonably practicable. The OHS Regulations require that hazards associated with the use of plant be identified and actions taken to control risks. The legislation also places duties on designers, manufacturers and suppliers of plant.

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