We have to remember that the isolation process will necessitate proving that the circuit is dead. Electrical circuits should be considered to be live until proven dead and therefore the hazard could still be present until this process is completed. Therefore, it is recommended that the prediction phase is completed before deciding how to safely prove circuits dead. Where very high incident energy levels are encountered, consider testing at downstream circuits first, using distance and of course PPE for residual risk. There is a large section on proving dead in Chapter 6: Process, Policies and Procedures which, if followed, will reduce the risk and help to eradicate the need for heavy PPE.
The service provider should always have their own rules and supporting procedures and not rely on the client policies in respect of electrical safety. This can sometimes lead to compatibility issues that will have to be dealt with by dialogue between contractor and client. I see the situation as being no different to a commercial contract between the same parties. The contractor would like to supply services to their terms and conditions and clients would like to procure those services under their terms and conditions. The most important point is that safety rules are agreed prior to work commencing. In most cases this can be a simple meeting of minds and an acknowledgement between the two parties of which rules take precedence. In other cases, it may necessitate the client handing over total control of an area or network to the service provider. Examples are assuming control of a high voltage network or working to Construction (Design and Management) Regulations.
Where it is necessary to undertake live work on a client’s site or premises, then the risk assessment must give justification and control measures which are detailed in previous chapters and also specifically for service providers below.
Work on or near live conductors needs to be controlled and it is worth highlighting those circumstances where such activities will definitely not be sanctioned by the rules. A non-exhaustive STOP list could be:
- Is there a justification for live working? (See Chapter 6: Process, Policies and Procedures for an explanation) - If the answer is NO then dead working is essential.
- Has the equipment been examined and found to be in good condition? Live work should never be permitted where there are any doubts about the safety of cables and electrical equipment being worked upon or adjacent to those being worked upon.
- Are test instruments, leads and tools approved, calibrated, correct specification for transient over-voltage levels and in good condition?
- Are test leads fused and in good condition?
- Is work at height required? Working at height whilst carrying out live work can create additional problems. Space is restricted and falls create another hazard.
- Is there confidence in the upstream protective device? Has it been adequately maintained?
- Is suitable accompaniment provided? Lone working should not be allowed.
- Are the workers competent and authorised for the task?
- Is the area free from ignition hazards?
Note that there is much more detailed information in Chapter 6: Process, Policies and Procedures.
The above bulleted list is something to consider. It is not exhaustive or mandatory but is an example of how rules can communicate clear boundaries on what is not acceptable practice. I would also suggest adding certain tasks to the list that would not be acceptable. Issues such as connecting and disconnecting cables into live equipment may be one such example unless specifically covered by rigorous safety rules.
Where the risk cannot be controlled by prevention or where there is a residual risk of injury then it may be necessary to consider mitigation to prevent injury to the worker. The provision of PPE should be used for electrical work where there is risk of injury from all hazards including the arc flash hazard. The requirements for the selection and use of arc rated PPE have been comprehensively covered earlier in this guide, not forgetting other hazards including electric shock.
In Chapter 8: Data Collection, there is a PPE selection model which will work for the service provider involved in inspection work. Otherwise, the 4-tier approach shown in the prediction section above, together with the prevention and policy sections can be used for determining the correct FR rating. As pointed out in the prediction section, severe burns can still be experienced at the hands which will usually be closer than 450mm to a possible arc when testing live circuits. For this reason, insulating gloves with leather over protectors are recommended for all work where the hands may be closer than 450mm, when testing circuits for instance.
10.3 What else can I do to manage the arc flash risk?
One of the most important things that you can do to prevent injury from the arc flash hazard is to provide awareness to any workers who may be involved with energised electrical equipment. From my experience, there are a disproportionately high number of arc flash incidents among contractors. In Chapter 6: Process, Policies and Procedures, there were various factors listed in the scope of technical knowledge or experience when defining competence. Among them was the need to have; an adequate understanding of the system to be worked on and practical experience of that class of system, an understanding of the hazards which may arise during the work and the precautions which need to be taken and an ability to recognise at all times whether it is safe for work to continue. A good risk assessment methodology will assist greatly in providing awareness, information and an understanding of the hazards. To have these principles enshrined in well written safety rules will enhance competence and safe working practices.
- Contractors appear to be high risk when it comes to arc flash.
- Do the risk assessment and know whether you are dealing with a raging tiger or a domesticated cat!
- Use the analytical tools that can be obtained with the guide.
- Follow the four Ps principle.
- Provide awareness of the hazard to your team.