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Lock Out And Tagging Of Plant

  • Document Type: Guidance Note
    Keycode: web only
    Industry: General, Synthetics manufacturing, 
    Category: Plant, 
    Division Author: Manufacturing & Agriculture
    Publication Date: 06 June 2005
    Date First Published: 21 November 2003
    Summary: This guidance note provides information on the development of safe isolation procedures to reduce the risk of injury while plant is being inspected, repaired, maintained, assessed, adjusted or cleaned.

This Guidance Note assists people at workplaces to develop safe isolation procedures to reduce the risk of injury while plant is being inspected, repaired, maintained, assessed, adjusted or cleaned.

This Guidance Note has been developed having regard to 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.


Plant is a general name for equipment, machinery, appliances, tools and implements. It can include things as diverse as a press in a factory or a computer in an office and it can range from electric drills to lifts and escalators; from tractors to hand trolleys; cranes to commercial fishing nets and arc welding gear. Every year people at work are injured, sometimes fatally, when plant is inadvertently activated or stored energy is released during inspection, repair, maintenance or cleaning activities. These injuries can be prevented by introducing and following effective isolation procedures.


An isolation procedure is a set of predetermined steps that should be followed to keep plant and its components from being set in motion or to prevent the release of stored energy, in order to protect the safety of persons during plant inspection, repair, maintenance or cleaning activities.
Example of tagged safety lockout hasp
Example of tagged safety lockout hasp

The development of procedures should be done in consultation with relevant health and safety representatives, plant operators, people who are doing adjustments, cleaning, maintenance, repairs or inspections of the plant and, if possible, with plant manufacturers, suppliers and people who designed and installed the plant. If the appropriate expertise does not exist at the workplace for the development of procedures, the employer should engage the services of a suitably qualified person or persons.

The effectiveness of isolation procedures relies on:

  • having the isolation procedure documented and accessible to the relevant people in the workplace
  • the provision of information, instruction and training of workers involved with the plant; and
  • appointing a person who through supervision ensures isolation procedures are rigorously applied.

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

  1. Shut the plant down
  2. Identify all energy sources and other hazards
  3. Identify all isolation points
  4. Isolate all energy sources
  5. De-energise all stored energies
  6. Locking out all isolation points
  7. Tag plant controls, energy sources and other hazards
  8. Test by "trying" to re-activate the plant, without exposing the tester or others to risk. This ensures that the isolation procedures are effective and all stored energies have been dissipated.

If 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. Written safety procedures must be developed in consultation with relevant health and safety representatives, people who are doing adjustments, cleaning, maintenance, repairs or inspections of the plant and plant operators and those procedures should be followed.


Shut the plant down
Plant that has a single energy source can usually be shut down by the operation of a single control such as a switch or valve. More complex plant may have to be shut down in a certain sequence, e.g. one conveyor before another, or by shutting down several energy sources, e.g. electricity, hydraulics, pneumatics, petrol, oil, steam, LPG, LNG, coal etc.

Identify all energy sources and other hazards
All energy sources likely to re-activate the plant, and place people doing the work at risk, should be identified. The energy sources include:

  • electricity (mains, solar and by generator)
  • fuels
  • heat
  • steam
  • fluids under pressure (such as water, air or hydraulic oil)
  • stored energy
  • gravity
  • radiation.

If original designer and installer "as built" diagrams of plant installations are not available, new diagrams/photographs showing location and details of various plant components, isolation points, switches, valves, energy lines, pipes, power sources, and control points (including computers) need to be developed as part of the isolation procedures. These diagrams/photographs can then also be used, along with written procedures, for information and training of workers.

Shutting the plant down may require other hazards to be identified and the risk of injury eliminated or minimised. For example, associated equipment may need to be locked-out to prevent re-activation, or valves on pipes and lines carrying gases or fluids may need to be locked shut or blanked off.

Depending on the type of plant, other hazards may include:

  • hazardous substances, such as gases, acids, alkalis and solvents
  • falls
  • burns
  • asphyxiation
  • impact.

Identify all isolation points
All plant of a type that could require an isolation procedure should be designed with appropriate isolation points for all energy sources to enable work on the plant to be carried out safely.

It is important to identify all isolation points in a system, as it may be necessary to use a local isolator to shut down a specific part of the machine (e.g. a motor) while the remainder of the associated plant remains in operation.

Emergency stop buttons, lanyards and similar stop devices on their own will not necessarily achieve isolation. It is extremely dangerous to rely solely on emergency stopping devices, as they are not designed for frequent use, cannot be locked out in all cases and may allow energy to be inadvertently re-activated. They may also allow control circuits to remain live. Remote control rooms and process computers should be considered when identifying isolation points.

Isolate all energy sources
The person in control of the workplace should also appoint a person (or persons) who knows and understands the complexities of the plant to coordinate the isolation of all energy sources and hazards to those working on the plant.

Care should be taken to ensure all electricity sources are identified and isolated, bearing in mind some plant will have several control stations and sections of plant may have independent electricity sources. If programmable logic devices are used to control the equipment, then it is essential to use local isolating switches as the means to achieve secure and safe isolation. It is not acceptable to rely on the controls of the programmable logic devices for the isolation of equipment, unless the device has been certified as a safety PLC which can reliably isolate equipment by activating its controls.

Except in the case of equipment connected via a plug and socket, a competent person such as an electrician should isolate and disconnect all electricity supply to an item of plant (not just the control circuit) so that equipment cannot be inadvertently energised via another source or control system.
Examples of circuit breaker lockouts
Examples of circuit breaker lockouts

De-energise all stored energies
Take any of the following steps that are necessary to guard against energy left in the plant after it has been isolated from its energy sources.

  • Inspect the plant to make sure all parts have stopped moving
  • Install ground wires
  • Relieve trapped pressure
  • Release the tension on springs, or block the movement of spring-driven parts
  • Block or brace parts that could fall because of gravity
  • Block parts in hydraulic and pneumatic systems that could move from the loss of pressure
  • Bleed the lines and leave vent valves open
  • Drain process piping systems and close valves to prevent the flow of hazardous material
  • If a line must be blocked where there is no valve, use a blank flange
  • Purge reactor tanks and process lines
  • Dissipate extreme cold or heat, or provide protective clothing
  • If stored energy can re-accumulate, monitor it to make sure it stays below hazardous levels.

Locking out all isolation points
Lock out devices
A wide range of devices is available for locking out energy sources and other hazards that could pose a risk to people working on plant. These include switches with a built-in lock, and lockouts for circuit breakers, fuses and all types of valves.

Also readily available are chains, safety lockout jaws (sometimes called hasps), accommodating a number of padlocks, and sets of robust safety padlocks. Only devices that incorporate a lock or can accommodate one or more padlocks are suitable lockout devices.

One person, One lock
If more than one person is working on the same plant, each person should attach their own lock to prevent the isolator being opened before all locks have been removed or opened. The isolation procedure should identify common lock out points to ensure energy cannot be restored while someone is still working on the plant.

If two or more people are working on plant that is isolated through several lockout points, each person should attach a lock and tag to each lockout point.

To avoid the need for multiple locks on each lockout point, a lock box may be used. Under this system each lockout point is locked by only one lock and the keys to the locks of the plant's lockout points are placed inside a box which is locked by all the individual locks of people working on the same plant.

One lock, One key
Each person working on the plant should have their own lock, key and tag. There should be no duplicate key available for any lock, except a master or duplicate key for use in an emergency that is secured and not readily available.

During inspection, repair, maintenance, cleaning or adjustment of the plant, the one key to each person's lock should be held only by that person, who is responsible for both locking and unlocking the lockout device.

Multiple energy sources
If more than one energy source or hazard has to be locked out to enable safe shutdown of the plant, the single key to each lockout device should be held by the same person.

A tag is not in itself an effective isolation device. A tag acts only as a means of providing information to others at the workplace. A lock should be used in preference to a tag, as an isolation device.

Warning tags normally used are:

  • personal danger tags: Personal danger tags should be restricted to employees who will be working on equipment. A personal danger tag on the isolation devices of an item of equipment is a warning that the equipment is in an unsafe condition and that operation of that equipment may endanger the person who attached the tag. All personal danger tags of the disposal type should be destroyed after use.
  • out of service tags: An out of service tag is a notice that distinguishes appliances or equipment out of operation for repairs and alteration, or plant that is still being installed. While an out of service tag is attached to the appliance or equipment, it should not be operated. Out of service tags should not be relied upon to provide personal protection.

Personal danger tags and out of service tags should not be used together on the same item of equipment because they relate to different circumstances. An out of service tag should be removed when a personal danger tag is added, and vice versa. On completion of maintenance, cleaning, etc works, remove the tags before the plant is returned to operational status. Tags should only be removed by those people who tagged the controls.

Personal danger tags A personal danger tag should be attached to an isolator in a visible position whenever the isolator is used to lock out an energy source to allow work to be done. It should accompany each lock used in an isolation procedure and should identify the person who put the tag and lock in place, the time and date this occurred and the item of plant being isolated.

The person doing the work should personally fasten their personal danger tag on all lockout devices involved in the isolation procedure. If more than one person is involved in the work, each person should attach their own lock and personal danger tag to the lockout device. Locks are available that have a personal danger tag incorporated to ensure that the tag cannot be removed by any person other than the person who attached it.

A personal danger tag should be removed only by the person whose name is written on the tag. Removal of a personal danger tag from an isolating device should be carried out as soon as possible after completing the work. In every case a personal danger tag should be removed prior to leaving the worksite at the end of the shift. The isolation procedure should include the action to be taken should a person fail to remove a personal danger tag before leaving the worksite.

Where work on plant is not completed by the end of a working shift and the plant is required to remain isolated, arrangements should be made for out of service tags to be placed on each isolating point before personal danger tags are removed. If work on the plant is to continue during the next shift there should be a "hand over" briefing by the shift leaving the site to those taking over the work. The briefing should include the status of the work and the removal or replacement of personal danger tags and locks.

Out of service tags An out of service tag on an item of plant indicates that the plant is unserviceable and should not be used. It can be attached to non-powered plant such as ladders, jacks and trolleys as well as powered plant and should be attached to the main controls if possible, or to a prominent part if there are no controls (such as in the case of a damaged ladder).

Out of service tags should be attached by a competent person having specific knowledge relating to the plant and, where applicable, be placed on devices which isolate energy sources, only when those devices are set in the 'off' or 'safe' position.

Prior to attaching an out of service tag all required details on the tag should be clearly entered in the spaces provided, with emphasis given to the reason for placing the tag. Tags should be securely fixed, so as to be clearly visible.

Except in an emergency, out of service tags should be removed only by a person who is both familiar with the plant and fully conversant with the reason that the tag was placed.

In the absence of any personal danger tag or lock, removal of an out of service tag effectively releases plant for use, and should not be done prior to ensuring that:
  1. all people known to have been working on the plant are clear of the plant; and
  2. an inspection of the plant indicates that all machinery guards are in place, that all protective devices are functional, that all maintenance tools and aids have been removed, and that the equipment is safe for normal use.
Example of equipment out of service tag
Example of equipment out of service tag

Out of service tags are intended to convey a clear DO NOT OPERATE warning, and that failure to comply may result in damage to the equipment and may cause injury to a person. It is essential that isolating mechanisms with out of service tags attached are not switched, manipulated, or interfered with in any way while these tags are in place.

Testing isolation procedure
After plant has been shut down, locked out and tagged, all isolated power sources should be tested first with appropriate instruments and then by trying to activate the plant, before any person attempts to start work on the plant. This should be done by a person who understands the complexity of the plant (or parts of the plant, including control stations and computers remote from the plant).

It is not safe to assume an isolator has locked out an electricity source simply because it is in an open position. While normally this should open an air gap between contact points, it is possible for contact points to become welded together by the passage of electricity, and remain so even when the isolator appears to be open.

Work on the plant should not begin until tests have confirmed it is safe to do so. The calibration of any instruments required to test isolation procedure should be checked before use.


Employers have responsibilities under the Occupational Health and Safety Act 2004 to ensure that a work environment is provided that is safe and without risks to health, so far as is reasonably practicable. The Occupational Health and Safety (Plant) Regulations 1995 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, importers and suppliers of plant.


Acts & Regulations

Occupational Health and Safety Act 2004
Occupational Health and Safety (Plant) Regulations 1995

If you only want to view the legislation you can use the Parliament of Victoria web site; go to,
click on "Victorian Law Today" and scroll down to the "Search" window.

The following references may be helpful in meeting legal responsibilities:

WorkSafe Victoria

Plant (Code of Practice No.19, 1995)

Copies of publications can be obtained by contacting WorkSafe Victoria on 03 9641 1555, or your local WorkSafe Victoria office.


Much of the text in this Guidance Note was sourced from the WorkSafe Western Australia publication Isolation of Plant, and has been reproduced courtesy of the WorkSafe Western Australia Commission.

Acts and Regulations

Acts and regulations are available from Information Victoria on 1300 366 356 or order online at

View the legislation at Victorian Law Today at

Standards Australia

Copies of standards can be obtained by contacting Standards Australia on 1300 654 646 or by visiting the web site at

Further information

Special Note on Codes of Practice: Codes of Practice made under the Occupational Health and Safety Act 1985 provide practical guidance to people who have duties or obligations under Victoria's OHS laws. The Occupational Health and Safety Act 2004 allows the Minister for WorkCover to make Compliance Codes which will provide greater certainty about what constitutes compliance with the OHS laws.

Codes of Practice will continue to be a practical guide for those who have OHS duties and WorkSafe will continue to regard those who comply with the topics covered in the Codes of Practice as complying with OHS laws. WorkSafe will progressively review all Codes of Practice and replace them with guidance material and in appropriate cases, with Compliance Codes.

Note: This guidance material has been prepared using the best information available to WorkSafe Victoria. Any information about legislative obligations or responsibilities included in this material is only applicable to the circumstances described in the material. You should always check the legislation referred to in this material and make your own judgement about what action you may need to take to ensure you have complied with the law. Accordingly, the Victorian WorkCover Authority extends no warranties as to the suitability of the information for your specific circumstances.