ARC FLASH FEATURE MINIMISING THE THREAT


Carlo Granata of Honeywell explains the important role that arc flash protection plays in keeping electrical engineering as the backbone of modern industry


PPE perspective. PPE should be the last line of defence and


T


he versatility of electricity means it can be put to an almost limitless set


of applications. However, with this versatility comes some significant risks. And, when it comes to human interaction with electricity, there are two inherent risks - electric shock and arc flash. Carlo Granata of Honeywell Safety


Products, commented, “In work environments particularly, electrical risk is highly managed from hazard analysis and the adoption of specific safe working practices, through to the provision of insulating personal protective equipment (PPE), such as rubber gloves, or insulating protective equipment (IPE), such as tools, where the risk cannot be eliminated through other controls.” Arc flash is an explosive condition associated with the release of energy caused by an electric arc and can include a broad spectrum of electromagnetic energy including heat, flame, fragments and spray of molten materials. Arc flash temperatures can reach or exceed 319,400°C at the arc terminals. The massive energy released in the fault rapidly vaporises the metal conductors involved, blasting molten metal and expanding plasma outward. Common injuries caused by the force of the explosion and intense heat are external and internal burns, concussion, collapsed lungs, hearing loss and fractures. The injuries can be extremely serious and, in some cases fatal, with the worker’s body, face and hands at most danger and therefore the key focus from a


worker contact with any electrical installations needs to be minimised to the fullest through established working practices. There will however, be times when human contact is necessary - often during maintenance schedules. The most obvious way to remove the hazards associated with an arc flash is to de-energise the electrical equipment whenever anyone will be coming into contact with it. However de-energising electrical equipment is in itself an arc flash hazard and needs to be managed from a PPE perspective. Given the key threat areas to workers and the hazards of heat, fire, flame and electrical blast, the provision of specialist protective equipment is essential - specifically designed to provide protection against these risks.


SELECTING THE RIGHT PROTECTION There are currently two ways that PPE is tested against arc flashes to give it a protection rating - the box test method (developed in Germany and based on two classes according to the amperage) and the ATPV (arc thermal performance value) which creates a number based on the performance on which a material is evaluated. The box test standard defines two test


conditions, namely Class 1 and Class 2: l


and arc duration of 500ms. l


Class 1 tests at an arc current of 4kA


Class 2 tests at an arc current of 7kA and arc duration of 500ms. Concerning clothing, properly selected arc rated products will offer the wearer adequate protection but it is essential that users liaise with specialist manufacturers to ensure the protective clothing they are selecting meets the performance demands they need to properly protect against the arc flash risk levels. The arc rating performance of clothing


is the number of calories that the garment is expected to ‘absorb’ if exposed to an electric arc. Arc rating is the level of protection provided to the wearer and is measured in calories. The engineer will be protected from an electric arc if their clothing has a higher calorie arc rating than the calories of


/ ELECTRICALENGINEERING


Right: PPE should be the last line of defence and worker contact with any electrical installations needs to be minimised to the fullest through established working practices. There will however, be times when human contact is necessary – often during maintenance schedules


Above: Carlo Granata, business manager, Electrical Safety EMEAI, for Honeywell Safety Products


Left: whilst electric shock risks are well known, arc flash is probably a less well known risk and can all too often be easily underestimated – with potentially deadly consequences


heat generated by the arc. Flame retardant overalls meeting the standards are required as is a flame retardant balaclava (like those used by F1 drivers).


FACE PROTECTION (EN 166) When looking for eye and face protection, basic requirements are outlined in the European Standard (EN 166) but a more recent German standard (GS-ET 29) may be used when looking for increased protection. Face and head protection should include full face shields with integrated hood and can also include air flow respirators where necessary.


HAND PROTECTION Hands are likely to be the closest part of the body to the source of the arc flash, but at the moment no EN regulation for arc rating gloves exists. Recently however, the International Electrotechnical Commission (IEC) called on experts to look to create a ‘Preliminary Work Item for determining the electric arc performance of hand protection equipment.’ It added that in the meantime, testing labs should perform tests on gloves, adapting standards available for clothing or ASTM. Prior to that, where hand protection is concerned it is recommended to wear rubber insulating gloves combining protection from shock and arc flash resistance properties that are inherent to the rubber.


Arc flash risks present a very clear and present danger. Where they do happen, the impact can be catastrophic for whoever is caught in one. PPE is the last line of defence but needs to provide the right level of protection.


Honeywell www.honeywelluk.com T: 08457 678 999


Enter 212 ELECTRICAL ENGINEERING | SEPTEMBER 2014 31


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64