From Electrical Review – Arc Flash danger
Blown Fuse – Why are we happy to work in the minefield?
WEB EXCLUSIVE Before embarking on this month’s rant, let me state I am not in favour of the nanny state. I object to traffic calming measures, other than around schools and hospitals; I find it facile that ofcom demands that TV shows can only depict car thieves if they’re shown driving off wearing their seatbelts; and I don’t think playground conkers is a blood sport!
However, while to the best of my knowledge there have been few, if any, conker related fatalities I have been drawn to a statistic that is frankly alarming. About ten people a day in the UK suffer severe injuries, or worse, as a result of electrical crossovers – I still prefer the term arc flash. This figure is appalling, but may not even be accurate since that estimate is drawn only from victims reporting to major burns units. How many more minor injuries and near misses go unreported is anybody’s guess.
I know that some jobs are hazardous. Miners, construction workers, civil engineers, oil and gas riggers all carry risks that are well known to those employed in those industries. Of course electrical engineers also work within high risks, but these risks are largely predictable and with due care, attention and training the dangers can be militated for. Not so in the case of arc flash it seems.
While most Review readers are aware of arc flash, it’s worth highlighting the nature of this hazard. Typically arc flash temperatures reach 3,000oC but in large equipment they can reach nearly 20,000oC – and that’s four times hotter than the surface of the sun! In such extremes injuries can be caused up to 10m from the flash. At the same time, super heated gases burn the throat, lungs and other internal organs. Such is the acceleration of the ionised air that fiery plasma erupts as a fireball. Metals in the immediate vicinity are vapourised (and breathed in), while other more distant metal objects may be blasted into high speed shrapnel. Injuries can be horrific and fatalities can be long and painful. Coupled with the unpredictability of arc flash incidences, some electrical engineers are working in the industrial equivalent of minefields.
Now, the problem seems to lie in the relative looseness of regulations covering those working in the potentially hazardous areas where arc flash can occur. Regulation 14 of the Electricity at Work Regulations 1989 makes clear (sic) three conditions that must be met for live working to be permitted. These conditions are: it is unreasonable in all the circumstances for the conductor to be dead; it is reasonable in all the circumstances for that person to be at work on or near that conductor while it is live; suitable precautions (including where necessary, the provision of personal protective equipment) have been taken to prevent injury. It strikes me I could dream up any number of reasons compliant with the Regulations.
Don’t get me wrong, I fully appreciate in the real world risks are sometimes unavoidable. My concern is what constitutes a reasonable and acceptable risk is not defined at all!
Naturally manufacturers whose equipment is most subject to potential arc flash – such as switchgear makers – are often reluctant to discuss the risks. However, this surprises me since the best of them now have remedies built into their latest equipment. The UK’s biggest switchgear manufacturer claims to have a really innovative arc quenching solution using volcanic rock, but when I asked to write about it I was forbidden from doing so. This suggests to me that either the system isn’t 100% reliable or that the company believes that by flagging up the risk it might jeopardise sales.
One would imagine if working practice legislation doesn’t work – remember there are ten casualties a day – it would be relatively straightforward to at least regulate the specifications of all new equipment. Surely, if equipment makers have suitable arc suppressors, they would welcome and lobby for such a move.
I struggle to think of any walk of life in Britain, where 3000 extremely serious casualties a year fail to bring about preventative or at least protective government action. It seems we worry more about the welfare of our conker players more than we do the electrical engineers that keep our business, industry, commerce and infrastructure running.
John Houston can be contacted on 01797 364366 or by e-mail at firstname.lastname@example.org