New Dangers in Determining Adequate Electrical PPE
02 October 2012
Shockingly recent tests have indicated that in many cases workers are under-protected against the heat levels that they are exposed to during an arc flash event.
Over recent years there have been massive steps towards improving the personal protective equipment (PPE) worn by individuals with high risk jobs within electrical environments. This has been a major step towards protecting workers against the heat energy associated with arc flash events.
Researchers from Ferraz Shawmut’s High Power Test Laboratory have been looking into the level of thermal protection that is currently worn within electrical PPE clothing by workers and assessing whether the protection levels are safe enough. Shockingly the new tests have indicated that in many cases workers are under-protected against the heat levels that they are exposed to during an arc flash event.
Explaining on a rudimental level, an arc begins when current begins passing through ionized air, creating a by-product of heat. Volumes of ionized gases and combined vaporised metal from conductors are then explosively expelled within a plasma cloud. It doesn’t end there though as electrical energy continues to be converted into extremely hazardous energy such as a pressure wave, extreme heat, toxic smoke, molten conductor material, shrapnel and intense light.
Any person within the range of the expanding plasma cloud is directly exposed to the highest heat levels. Temperatures have been measured within this area in the new tests and have been noted as over 15,000 °C. In addition to the heat from the plasma, an individual is directly exposed to the molten metal ejected from the electrode tips and radiated heat from surrounding. These test results were shown at the IEEE Electrical Safety Workshop and clearly highlighted that there was the possibility of higher heat energy being produced than previously predicted.
Importantly this research uncovered electrode configurations that resulted in the projection of significantly more heat energy than the current predicted levels. The risk occurs when conductors where configured differently, thus changing the directional nature of the arc development. Mainstream arc flash protection clothing was tested within this directional plasma flow at both higher and predicted levels. Worryingly the PPE did not provide even the predicted level of thermal protection in many cases.
New arc flash management strategies are needed to address this identified increased risk. The IEEE have joined the NFPA in order to create a joint collaborative initiative on arc flash research. Their target is to enhance safety standards that predict the hazards of arc flash events and to improve safeguards for workers. Moving forwards two major management areas of improvement should be considered by all employers:
Firstly, provisional enquiries have suggested that the equipment configurations which direct arc flash development outward should be clearly identified. Models then need to be designed in order to accurately predict the levels of energy presented to the workers from such equipment.
Secondly, the current industry test method and rating system for arc flash PPE need to be redeveloped in order to address the newly identified hazards. Higher level PPE should be worn while this takes place. This is especially relevant for configurations which direct the arc flash development outwards towards the worker.
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