Electrical safety
‘European approach’ to arc flash risk DuPont claims that electrical arc, and the resulting “arc flash”, are among the deadliest, least understood hazards of electricity”, and can potentially occur in many industrial and other applications, including hospital plant rooms. Technical and engineering personnel from DuPont Engineering Technology, DuPont Personal Protection, and external independent experts, have thus collaborated to develop “a European approach to electrical arc risk assessment”. The resulting free online resource, the DuPont Arc-Guide, sets out key steps to minimise serious arc flash incident risk, and details a range of optional, paid-for tailored risk assessment services, and an accompanying secure web portal, offering more in-depth guidance on this important, but apparently often overlooked, issue. HEJ editor Jonathan Baillie reports.
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ccording to DuPont – which held a “webinar” recently to highlight the new guide’s launch – while European legislation requires businesses and other organisations to perform regular risk assessments for all work activities and tasks, “electrical arc is often overlooked because most people are unsure how to assess and manage the hazard effectively”. The resulting danger is that the potential risks of an arc hazard incident which, at the very least, can cause second degree burns to those working on electrical equipment, and, at worst, may lead to a sizeable explosion and death or serious injury (see panel on page 38), are often underestimated, and even ignored, until too late. It is hoped, therefore, that the new freeto-access online guide, and (for those that sign up to pay to use them), an optional accompanying pre-assessment service, plus access to a secure portal providing further tools and information, will help duty holders and building owners including hospital estates and facilities teams, as well as external contractors undertaking electrical work on site, to “understand, evaluate, and reduce, the severities and consequences of electrical arc hazards”. Among the many instances where electrical arc hazard may be present highlighted by the guide are: r Testing. r Visual and infrared inspections. r Manipulation of live conductors. r Switching/racking breakers. r Installation of cables into energised equipment.
r Removal and replacement of live components. r Replacement of fuses and links. r Live underground cable jointing. r Inadvertent energised equipment penetrations. “Risk enhancing situations”, meanwhile, include: r Poor equipment maintenance. r Poor/“old” equipment design and installation. r Poor equipment commissioning and initial inspection. r Poor worker competence. r Human error. r Lack of concentration and distraction.
A ‘four-pronged approach’ At the guide’s core is a four-stage approach to minimising and, where possible, eradicating, electrical arc flash hazard, based on what DuPont dubs “the 4Ps” – “Predict, Prevent, Protect and Publish.” (see Fig. 1) The dedicated guide “public” website, www.arcguide.dupont.com, explains, and gives information and brief guidance on, subjects including: what constitutes an arc flash, the key contributory factors, and the circumstances when incidents are likely to have the most severe consequences. The site makes clear that, alongside the more obvious consequence – injury (see panel) and death to workers – these consequences can include the need to pay heavy fines or compensation, and severe damage to equipment. Detailing the fundamentals of the “4P” preventative approach, the site
An electrical arc occurring. emphasises that DuPont believes the best way to minimise the risk of, or eliminate, arc flash hazard, is via robust risk assessment. Thus, in addition to clearly and concisely setting out on the public site some of the key information on how to address arc flash hazard, the company can now also offer a “pre-assessment module”, on payment of pre-arranged fees, to, say, a hospital estates team wishing to obtain a clearer picture of the existing electrical arc hazard risks on its site, and how to minimise them. This package will include: r A personalised one-day visit by an arc Health Estate Journal November 2011
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Electrical safety flash risk assessment expert, who will review the arc flash hazards associated with the site in relation to which workers are likely to be affected (e.g. contractors/direct staff, site-based, or field-based, personnel). r An examination and identification of in which types of working environments, and during which tasks, the hazard is likely to be predominant. r Examination of the complexity of on-site electrical distribution networks. Also included as part of the “module” are: r A presentation to management staff and other “stakeholders” on arc flash and “the European approach”, including initial feedback on any on-site findings. r Personal feedback and advice during the day on questions raised, or observations made, during the visit. r A summary report recommending a path forward which will detail “the most cost-effective solutions and choices in order to effectively carry out risk assessments for the electrical arc hazard”.
Ongoing, paid-for support A further option, for those organisations wishing to obtain ongoing help and support in assessing and controlling arc flash hazard risk over a longer period, (including access to calculation software and tools that will allow them to accurately calculate the risks with any piece of electrical equipment), is a range of paid-for contracts. These afford a limited number of user licenses within the organisation for, say, one or two years. The licences allow authorised personnel to access a secure portal (which is not available to the wider public) that provides further, more in-depth, technical and practical information and tools to simplify arc flash risk assessment and, where these are deemed necessary, facilitate the task of putting in place preventative measures. Further information on the various options is
YES Re-evaluate
Predict severity
Results
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Health Estate Journal November 2011
Predict
Prevent
Publish
Protect
NO
Residual risk
Publish results and training
Apply protection measures
Figure 1: DuPont’s “4Ps”-based approach to minimising arc flash risk. available via the DuPont Arc-Guide Support Desk, details of which are on the public website. The recent webinar focussed on both the public site, and the secure paid-for portal, and explained the different levels of guidance available through them. DuPont says in its pre-amble on the public site: “Risk assessment is defined by the European Agency for Safety and Health at Work as the process of evaluating risks to workers’ safety and health from workplace hazards. It is a systematic examination of all aspects of work that considers: r What could cause injury or harm. r Whether the hazards could be eliminated and, if not, r What preventive or protective measures are, or should be, in place to control the risks.” Referring to the preventative approach it advocates, DuPont goes on to say:
Common injuries from arc flash Of the types of injury that can result from arc flash, DuPont says: “Arc flash injury can include external burns to the skin, internal burns from inhaling hot gases and vaporised metal, hearing damage, eye damage such as blindness from the ultraviolet light of the flash, as well as many other devastating injuries. Depending on the severity of the arc flash, an explosive force known as an arc blast may also occur, which can result in pressures of over 100 kiloPascal (kPa), launching debris as shrapnel at
Can we apply further prevention techniques?
speeds of up to 300 metres per second (m/s). “Survivors of such injuries may require extensive treatment and rehabilitation, and the cost of these injuries can be extreme, physically, emotionally, and financially. While legislation requires businesses to perform risk assessments for all work activities, electric arc risk is often overlooked, because most people are unsure how to assess and manage this hazard effectively.”
“At DuPont, we use the ‘4P’ approach to risk assessment: r Predict: Safeguard your workers by predicting the severity of arc flash hazard so that you can assess and manage risk more effectively. r Prevent: Look at ways to prevent arc flash from occurring and endangering your workers. r Protect: When prevention is not enough, protective measures such as PPE may be required. r Publish: Employ training measures, produce risk assessment forms, and publish EU-compliant labels to warn workers of high levels of incident energy and risk of arc flash injury.”
A collaborative effort Speaking during the webinar as the guide was launched, Mike Frain, managing director of Sheffield-based Electrical Safety UK, a specialist company “concerned with the safety of workers who carry out electrical work”, which advises industrial and commercial organisations and utility service providers on electrical safety, writes procedures and rules, and trains staff and contractors, and which worked with DuPont to develop the guidance, said: “The team that produced this guide, including a number of representatives from academia, collaborated for over two years to put it together. “It not only clearly explains what arc flash hazards are, and the potential consequences of an incident, but also looks at key elements such as the incident energy level, which, in conjunction with factors including how far a worker is from the centre of the arc flash, the amount of current that flows
Electrical safety into the arc, and the time of r Helping users “match the exposure, will determine the level of residual thermal likely degree of injury and/or risks with the rated damage to equipment. performance of a PPE to “Using the tools provided, optimise protection and those responsible for major comfort for workers”. electrical installations can r Enabling co-workers calculate the arc flash risk worldwide to have up-tofrom equipment such as date information online, switchgear, motor control as well as access to the centres, and electrical calculation database. panels and cables, consider r Providing access to how they might best reputable arc flash risk mitigate them and, where assessment partners. there is no opportunity to A lack of specific eradicate the risk altogether, legislation how, for example, they can Mike Frain, MD of field label particular Sheffield-based Electrical Mike Frain was at pains to equipment to ensure that Safety UK, which worked point out that one of the workers are aware of the main reasons why DuPont with DuPont to develop risk and take whatever had felt the guide was the guidance, said: “The preventative measures they team that produced this needed was that, although, can (such as wearing the guide, including a number EU Directive 89/391/EEC correct personal protective of representatives from requires employers to equipment) to afford perform (regular) risk academia, collaborated themselves maximum assessments for all hazards, for over two years to put it together.” protection.” there are currently no As DuPont puts it, the specific regulations Guide should be “an invaluable tool” to all governing arc hazard risks. He explained those charged with electrical safety in: that one of the difficulties facing r Giving guidance that will help avoid engineers and electrical installers when worker injuries, equipment damage, seeking to evaluate the risk of arc flash and legal fines, via putting in place from any particular “kit” was that one “appropriate control measures” for the piece of electrical equipment that severity level of electrical arc hazard. appeared, overtly, to all intents, very r Enhancing understanding of electrical similar to another, could pose very arc hazard, risk prevention, and different degrees of risk. mitigation concepts. In addition to helping to protect those r Assisting users to easily locate, identify, working on electrical installations out in and engineer out, serious danger. the field, DuPont is keen that the guide be
used by design engineers to help them design out arc flash risk in any new equipment wherever possible. Explaining briefly during the webinar the fundamentals of what makes an arc flash incident happen, Mike Frain said: “An electrical arc is an electrical breakdown of a gas (e.g. air) which produces an ongoing plasma discharge, resulting from a current flowing through normally non-conductive media such as air. It can occur where there is sufficient voltage in an electrical system, and is usually caused by a short circuit of energised conductors. This initial short circuit is very often caused accidentally by electrical workers.”
From ‘inconsequential’ to disastrous Emphasising the potential severity of such an occurrence, the DuPont Arc-Guide website states: “An arc flash caused by an electrical arc with 1,000 amperes or more can cause substantial damage, fire, or injury. The massive energy released in the fault rapidly vaporises the metal conductors involved, blasting molten metal, and expanding plasma outwards with extreme force. A typical arc flash incident can be inconsequential, but could conceivably easily produce a more severe explosion. The violent event can cause destruction of equipment involved, fire, and injury, not only to the worker, but also to nearby people. Forces may exceed 100 kPa, and debris is spread up to 300 metres/second, with temperatures of up to 20,000˚C.” The “public” site goes on to add that, “in addition to the explosive blast of such a fault, destruction also arises from the intense radiant heat produced by the arc. The metal plasma arc produces tremendous amounts of light energy – from far infrared to ultraviolet. Surfaces of nearby people and objects absorb this energy, and are instantly heated to vaporising temperatures, with the effects of this seen on adjacent walls and equipment; they are often ablated and eroded due to the radiant effects. The thermal incident energy dissipated onto the worker can cause severe skin burns, or have health consequences.”
Risk of loss of service
ARCBAN clothing from JK Ross incorporating DuPont Nomex. This layering method of protective clothing is, DuPont says, “recommended for correct arc flash protection”. It adds: “As a result of an arc flash study, the potential severity or incident energy level of an arc flash will be better understood, and therefore the amount of protection needed for any person working in this area can be determined. However, PPE is the last line of defence, and, if worn, the level of protection must always exceed the potential risk.”
In addition, of course, to the potential serious threat to employees, healthcare estates teams could also potentially face significant problems should, for example, a generator or other key electrical appliance serving a hospital be out of action for any length of time, placing further emphasis on the need to ensure that the arc flash risk from any given equipment is properly identified, and that, where feasible, appropriate measures to minimise the chances of an incident occurring are taken. ✚ Health Estate Journal November 2011
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