FEATURE HAZARDOUS AREA EQUIPMENT POWER TO THE PEOPLE
To both minimise the risk of arc flash and protect against residual risks, Northern Powergrid has used DuPont and its value chain partners, J&K Ross (UK distributor) and Dale Techniche (Garment Manufacturer) to provide a solution to this dangerous hazard
generated by an electric arc. A new concept in the construction of fabrics was used, based in a non-homogenous blend to create an intelligent fabric. This means that when the fabric is exposed to high thermal energy, it responds with an asymmetric shrinkage, generating an extra air chamber to protect the person wearing the garment. The blend offers high protection, especially when taking into account its low weight, which is particularly well suited for those working at Northern Powergrid. Once the design was confirmed and the
E
lectric arc flash or electrical flashover is one of the most deadly and least
understood hazards of electricity and it is prevalent in most industries. It is usually caused by inadvertent contact between an energised conductor, such as a busbar or wire, with another conductor or an earthed surface. The resulting short circuit current will melt the conductors, ionise the air and create a conducting plasma fireball with temperatures in the core of the arc that can reach upwards of 20,000°C causing severe injury and even death. A complex risk assessment was carried
out by electrical consultant Mike Frain from Electrical Safety UK over a four month period. The process met European Legislation (80/391/EE) requiring employers to perform a risk assessment on tasks and was framed by the DuPont 4 P approach - predict, prevent, protect against and results published. The risk assessment looked at worse case scenarios, taking photos of all the key jobs at risk and measuring the distance between a potential arc and a workers body in different positions. The measurements were collated into a report that evaluated the energy levels, arc flash risks and highlighted areas where there was opportunity to improve.
COLLABORATION A patented solution was developed with DuPont Nomex on the outside and
18 APRIL 2014 | ELECTRICAL ENGINEERING
DuPont Kevlar on the inside to produce a very high thermal barrier against flash fire and arc. Because of the reaction of Nomex thickening in a flash fire and Kevlar providing high tensile strength, when such an event occurs, it creates air pockets in the fabric and therefore provides a lightweight flash fire and arc flash solution. For the Northern Powergrid project
two fabrics were worked on - the e+ARC 220RS woven fabric for coveralls and trousers, and the A+PANTHER HD 220 RI knitted fabric to make t-shirts and polo shirts. The e+ARC 220RS fabric is developed to specifically protect against the very high level of thermal energy
Above and below: fit for purpose garments are protecting workers of Northern Powergrid from deadly flashover
fabrics approved, a brief was submitted to DuPont manufacturing partner, Dale Techniche. To ensure that only garments of the highest quality were delivered, Dale Techniche matched the e+arc fabric made with Nomex with state of the art manufacturing processes which were QA controlled by their own staff. Elaina Harvey, Nomex account manager at DuPont, explained, “During the development process the prototypes were also mannequin tested on DuPont Thermo-Man for four seconds to simulate an industrial fire with temperatures up to 1,000°C to ensure they would be fit for purpose. They were also tested on the DuPont Arc-Man test rig to simulate an arc flash, confirming the high protection level of the fabric.”
THE FINISHED PACKAGE Fulfilling the PPE contract included sizing over 1,600 employees, a process that took a team of four people approximately five weeks, across 14 sites in the north east and Yorkshire. Chris Ross, managing director of J & K Ross, explained, “Each employee was individually sized and the information recorded into a custom database to ensure that when the final kit was received, there would be no doubt that the garments would be fit for purpose.” The finished package for Northern
Powergrid included some 3,500 coveralls, 6,000 t-shirts and polo’s and 3,200 trousers for employees across the Northern Powergrid sites.
DuPont
www.dupont-europe.com T: 01925 645 645
Enter 209 / ELECTRICALENGINEERING
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