Electrical Safety Week: Lock Out Tag Out
According to Safe Work Australia, four work-place related fatalities occurred as a result of electrocutions in 2017. A percentage of these fatalities occurred as a direct result of individuals working on or near exposed live parts including testing.
This is an alarming unnecessary loss which as occurred due to unawareness of electrical safety.
Master Electricians Australia is working with the industry to create awareness and provide access to tools like safety guidelines and procedures to avoid future risks and fatalities.
Every State and Territory in Australia has Work Place Health & Safety and Electrical legislation in place to protect workers from becoming another statistic.
Codes of Practice and Compliance Codes are guidelines that help to achieve standards set out in Acts and Regulations. Below are the Codes of Practice appropriate to isolation, safety tag and lockout procedures:
- How to Manage Work Health and Safety Risks – ACT, NSW, NT, QLD, SA, and TAS
- Managing Electrical Risks in the Workplace – ACT, NSW, QLD, SA, and TAS
- Safe Low Voltage Work Practices by Electricians
Risk Assessment and Awareness
At any workplace, risks must be assessed before the commencement of onsite tasks or activities. The Electrical Safety Legislation requires that the electricity supply must be isolated from an installation or equipment prior to work commencing unless an unacceptable risk is imposed on a worker or the community by isolating the electricity supply.
Examples of the only risks that will enable live work are:
- Non-conclusive test results are obtained when the electrical supply is cut off from the installation or equipment. Thus, live testing would be required.
- Live work deemed necessary in the interests of safety, for example, maybe a major risk to the community over and above the risks that the worker would be exposed too.
- Any tasks that could result in a widespread outage – this risk is generally used by electricity entities.
The risk control hierarchy used when isolating supply (Source: QLD Code of Practice for Managing Work Health and Safety Risks 2011):
Elimination – Removal of the electrical energy which has the potential to cause ventricular fibrillation of the heart and burns to the skin
Isolation – creating a gap in the electrical circuit, which prevents electrical energy from reaching the isolated parts
Engineering – Use of a secure locking device, individually keyed and of robust construction
Administration – Application of a tag to the isolation device warning others of the potential risk if the device is closed and conducting a written risk assessment prior to work commencing
PPE – Use of appropriate personal protective equipment.
Eliminating Electrical Energy and Proving De-Energised
If the electrical supply to equipment must be eliminated for the task to be performed, the electrical safety legislation dictates that the Employer/PCBU (person conducting a business or undertaking) must ensure the electrical equipment is tested by a competent person to determine whether or not the equipment is energised.
The equipment must be treated as if it is energised until the electrical energy is isolated and tested to prove it is not energised.
Testing to prove de-energised is live work and therefore a Safe Work Method Statement (SWMS) must be developed for the work, a site risk assessment must also be completed before the work commences.
No worker should ever assume the isolated electrical equipment will stay de-energised throughout the entire duration of electrical work. Safety precautions should always be carried out to ensure the full protection of equipment and staff.
Safety Precautions include:
- Full PPE (such as flame-retardant clothing)
- Suitable eye protection
- Rubber mats
- Insulating tools and gloves.
If there is still a moderate risk, appointing a suitably trained and competent safety observer is always the recommended precaution.
Guidance can be found in AS/NZS4836: Safe Working on or Near Low Voltage electrical installations and equipment.
After leaving the work site for prolonged periods, lunch breaks, overnight, or change of shifts. Retesting the equipment to ensure it is still de-energised is another safety measure that must be followed.
The Isolation Process
To eliminate electrical energy an electrician must operate an isolation device, this could be a switch, circuit breaker, or the removal of a fuse. After the device is operated it must be rendered inoperable. This may be achieved by having the isolation device under the worker’s sole control all of the time. In this case, the worker would be prohibited from leaving the site where the device is situated until the work is completed and all electrical risks are removed. If a fuse is removed, additional activities such as removing the circuit wiring from the fuse base or placing a lockable cover over the fuse base are required to prevent someone from replacing the fuse into the fuse base. Keeping a fuse in a worker’s pocket would not be sufficient.
If a switch or circuit breaker is opened a locking device must be applied to the switch mechanism to secure the switch or circuit breaker in the open position.
The Isolation Process – Complex Installations and Isolation Permits
Isolation permits are an important document for group isolation procedures involving complex switching. This permit documentation should enhance the risk assessment process and provide robust isolation for the safety of workers. For more complex networks or equipment, isolation or switching sheets should be developed in consultation with a line or schematic electrical drawings. Some examples of complex networks may include:
- Control equipment in association with the main supply. Other energy sources from air, fluid, vacuum or weighs and other stored energy
- Motor generator units
- Photovoltaic systems
- Uninterruptable Power Supply systems (UPS)
- Capacitors and Emergency backup supplies
The Isolation Process – Multiple Locks
When multiple devices have been operated or multiple workers are working under one isolation, a lockbox-type device must be used as part of the isolation process.
The lockbox has multiple locks, generally keyed alike. Once all locks have been applied to the isolation devices the keys are placed in the secure box. All workers can then apply their individual personal locks to the box lid to prevent it from being opened. This prevents the isolation from being reversed until all workers from the site have removed their personal locks and ensure both the safety of workers and reduction of the level of risk.
Isolation Device Safety Signage and Danger Tags
An isolation device must also have robustly constructed signage, securely attached to it in a prominent position. The sign must include appropriate safety warnings for example “Danger Do Not Operate”. This may also be referred to as a danger tag. The information on the tag or sign may also include:
- The Worker’s name
- Contact details
- Estimated time of supply restoration
- Any other relevant information
Testing After Isolation
After the isolation has been performed, tests must be conducted to prove the isolation is effective and eliminated the electrical energy from the circuit and/or equipment.
When testing for dead, the worker must ensure suitable attachment points for the test instrument probes are established.
When isolating 3-phase systems, testing between phases may not identify a defective switch where 1 phase may have remained energised. Proper test points must be identified and testing between each phase, neutral and earth is vital.
When conducting tests for dead, the worker must prove on a known supply that the test equipment is operating correctly. The operation of the test equipment must be proved immediately before and immediately after the test for dead.
In addition, the worker must:
- Select the correct range on the voltmeter whether testing for direct current or alternating current voltages
- Visually confirm that the test equipment is fit for the purpose
- Check the test equipment has been tested (calibrated) in accordance with manufacturers’ instructions
- Check the test equipment is appropriate for the location of the tests, for example Cat iii or Cat iv
- Check the instrument has fused leads and the insulation of the leads shows no damage.
Risks When Conducting the Work
There is a possible risk that parts or conductors may become live while you’re working on site.
This risk will most likely occur when:
- Breaking circuit neutral conductors
- Breaking Earth conductors
- Voltages from other circuits are induced which may not be significant to produce lethal currents but may cause the worker to lose concentration or balance leading to other injuries, example falling from a height
- Conductive building parts may provide a return path to earth for the electrical current. Isolation from these parts will provide additional safety precautions under both normal and fault conditions
- Induced or residual voltages may remain after isolating the supply. If this could occur shorting and earthing of the conductors may be required.
Final Testing Examination
Section 8 of AS/NZS 3000 provides the mandatory verification required when work is complete. Appropriate inspections and tests must be conducted to ensure the electrical equipment is electrically safe and will operate in all circumstances expected.
The testing may require evacuating all workers from the work area who are not necessary for the testing process. When live tests are to be performed, the exclusion of these workers will enhance on-site safety.
There are a number of control measures that should be carried out to ensure heightened safety for all workers, some of these include:
- Good lighting
- Clear pathways and work areas
- Removing distractions
- Evacuating unnecessary staff
- Install barricades.
For further guidance and information on Isolation (Lock Out Tag Out) contact your State or Territory regulator.
Master Electricians have unlimited access to the MEA Safety, Technical, and Employer Advice hotlines. Phone direct on 1300 889 198 to speak to the experts.