Chris Ross explains the principle themes to the Arc Flash Protection Programme from J & K Ross
Electric arc is one of the most deadly and least understood hazards of electricity. The outcome of an arc flash can be disastrous but most people are unsure how to deal with the risks effectively.
An electric arc is an ongoing plasma discharge through normally non-conductive media such as air and occurs when there is a short circuit through the air between conductors or conductors and the ground, resulting in hazards including exposure of workers in front of the electric arc to extremely high temperatures, ultra violet light, toxic smoke and fumes and fast moving debris. This can result in burns, blindness, lung damage, hearing damage and death to not only the people working on the electrical equipment but also to people located nearby. J & K Ross has developed the Arc Flash Protection Programme to help companies assess the potential risks of arc flash, carry out the necessary checks and implement improved procedures if necessary. This may include the implementation of personal protective equipment (PPE).
People working in the vicinity of or at energised parts of electrical systems need to be protected against the effects of possible electric arcing. All such work needs, first of all, to be subjected to a risk assessment. This will enable the risk from arc flash to be identified, determine who might be harmed and form the foundation of the next steps.
The severity of the thermal effect of an arc flash is defined as incident energy, which may arrive at the worker at a given distance from the electric arc, and is measured in calories/centrementre² (cal/cm²); it is the energy that a victim, at a given distance from the electric arc, could receive to the surface of their clothing. In cases where the clothing is not sufficiently protective against the heat and radiation generated by an electric arc, the victim may suffer serious skin burns. An arc flash study will tell you the incident energy likely to occur due to the flashover, or in simple terms - how big is the bang? Following a risk assessment it may be necessary to carry out an arc flash study to establish the potential incident energy and then suitable risk control measures can be explored. Most importantly, there will be an evaluation that will highlight the cases of low risk, those which will need other protective measures and those areas where there is a great danger to workers who engage in live working activities or are working on or close to energized electrical equipment.
Based on the outcome of the risk assessment and arc flash study, control measures need to be implemented to remove, eliminate or reduce the risk. These measures should adhere to the following hierarchy of risk controls:
1. Elimination- de-energise equipment before beginning work
2. Minimisation - investigate trip times or fuse ratings and explore possibilities for faster disconnection times.
3. Information and training - educate workers to ensure their competence
4. Control the risk - properly maintain equipment and substations to ensure safe working systems
5. PPE - issue as a last line of defence to help prevent burn injury to workers
If it is still necessary to protect workers, providing all other practicable measures have been taken to minimise the risk, adequate PPE should be issued as a last line of defence. PPE can help protect against the thermal effects of an arc flash but it doesn't prevent the accident from happening in the first place.
Flame resistant (FR) clothing can be rated based on its Arc Thermal Performance Value (ATPV) in cal/cm2. To properly protect a worker, the ATPV rating of the FR clothing must exceed the calculated prospective incident energy caused by an arc flash onto the worker at a given distance from the electric arc. J & K Ross, in conjunction with DuPont Personal Protection, has developed ARCBAN® a range of CE certified arc flash protective garments made from Nomex®. The ARCBAN® range of garments are designed to be layered to offer the relevant level of protection when required for different jobs with different possible incident energies and ensure that the worker is not restricted or compromised with cumbersome clothing, which would have been selected based on being appropriate for the worst case situation. Layering the garments can help to increase the ATPV levels due to the air gaps in between the garment layers. It can also help with matching the hazard and risk with the appropriately designed PPE resulting in the wearer having more fit for purpose and comfortable solutions for the relevant hazardous environment.
The ARCBAN® range incorporates DuPontTM Nomex®, an inherently flame resistant meta-aramid fibre that does not melt, drip or support combustion in the air. The thermal behaviour of Nomex® is due to its molecular structure and not by applying a flame retardant chemical substance to the fabric, yarn, fibre or polymer. This means that Nomex® offers permanent protection that cannot be washed or worn away. The ARCBAN® range offers head to toe solutions providing various levels of electric arc protection.
DuPontTM and Nomex® are registered trademarks or trademarks of E.I. du Pont de Nemours and Company or its affiliates.ARCBAN® is a registered trademark of J & K Ross.
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