11.8 Personal Protective Equipment
Armed with the report, Northern Powergrid used the combined expertise of DuPont™ and its value chain partners, J&K Ross (UK distributor) and Dale Techniche (Garment Manufacturer) to provide a solution to the arc flash hazard. Feedback from the operational departments highlighted that the garments worn at the time by Northern Powergrid employees had a poor level of wearer acceptance due to an uncomfortable design. It also highlighted that the garments were not simple or flexible in their use, with many garments not compatible with each other. There was also an uncertainty on how to match the PPE with hazards in relation to arc flash and whether the existing FR clothing provided an adequate Arc Thermal Protective Value (ATPV). In addition to keeping employees safe, having a professional image and a corporate brand was key. The new designs had to not only adhere to the corporate identity of Northern Powergrid, but also had to be adapted to the working environment of the employees so that the highest degree of usability and comfort could be provided.
DuPont™ identified technical fabrics and solutions that not only adhere to safety and corporate requirements, but also protect against the thermal effects of an arc and flash fire. A patented solution was developed with DuPont™ Nomex® on the outside and 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 generated by an electric arc. A new concept in the construction of fabrics was used, based on 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 much higher protection than any market solution, especially when taking into account its low weight, which is ideal for those working at Northern Powergrid
Once the design was confirmed and the 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 employees. 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 degrees Celsius to ensure they would be fit for purpose. This life-sized instrumented mannequin is one of the most advanced thermal burn injury evaluation devices in the world, giving the ability to accurately test fabrics and garments under the most extreme conditions. They were also tested on the DuPont™ Arc-Man® test rig in Switzerland to simulate an arc flash, confirming the high protection level of the fabric.
11.8.1 Tailoring and trials
To ensure the sample garments were fit for purpose, Northern Powergrid had a group of around ten employees from each trade group, including linesmen, jointers and fitters, test different designs trial the garments and make suggestions based on their experiences. Dale Techniche and J & K Ross Ltd engaged with both the group of wearers and the project team in order to assess the feedback received once the garments had been worn for a lengthy period of time. This feedback was then used to fine tune the original designs to ensure both optimum ergonomics and user features were incorporated in the final garment designs before being CE certified.
11.8.2 The Finished Package
Fulfilling the project 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. 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. Prior to the process Northern Powergrid identified the specific product mix each employee required in order that they may be protected from their individual risk exposure (based on the tasks they would be expected to perform). As a result, J & K Ross were able to supply them with individual ‘employee packs’ to protect against electric arc flash and other thermal risks. A combination of shirts, trousers, coveralls, waterproof jackets, salopettes and wind stoppers were provided to each employee in a customised red and black holdall (Northern Powergrid colours) complete with company logo.
The garment packs are based on a layering system that gives different levels of protection depending upon the layers worn for different levels of hazards. Northern Powergrid developed a simplistic PPE matrix that was also issued to all operational employees and clearly conveys what level of protection is required for each activity. The initial quantities supplied were some 3,500 coveralls, 6,000 t-shirts and polo’s and 3,200 trousers for employees across the Northern Powergrid sites.
11.9 Protection in practice
Since supplying the PPE, the effectiveness in keeping personnel safe was graphically illustrated in April 2013 when two Northern Powergrid engineers working in a substation on an 11,000-volt cable fault experienced a flashover caused by the disruptive failure of a low voltage switchboard. Despite the intensity of the incident, they were able to make an emergency escape from the substation and thankfully were not injured by the flashover. Both were wearing their full arc flash PPE required for the task that had been carried out in accordance with operational procedures. It was evident that the PPE, effectively a last line of defence in these situations, served its purpose extremely well.
My thanks are extended to the following organisations in providing the material and permissions to enable this arc flash protection project to be put into the public domain.
- Northern Powergrid
- Electrical Safety UK Ltd
- J & K Ross
- Create a strategy to target high risk live working interactions.
- Follow the four Ps principle.
- The success of the prediction stage requires the willingness and cooperation of directors, managers, and frontline employees to engage with the project.
- Involve the workforce at the earliest opportunity.
- Design and fit are important to user acceptance.