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Understanding the value of arc flash management and mitigation for large electric process heaters
While larger medium voltage process heaters are relatively new in hydrocarbon processing , the safety issues surrounding medium-voltage equipment are well known . Arc flash events are a prime example of a rare but potentially deadly situation that can be mitigated with the right technology .
About the author
Mike Jones is a New Product Development Engineer who has a passion for collaborating with end users and teams to bring solutions to market . Mike is enthusiastic about developing heating solutions that enable replacement of carbonemitting heaters with heat generated through renewable sources . He currently leads the development and introduction of Watlow ’ s POWERSAFE™ Medium Voltage thermal system , a solution that helps end users reliably transition MW size gas-fired process heaters to electric .
By Michael Jones - Staff Engineer , Watlow
As process heaters become a popular alternative for larger applications that have historically utilized gas-fired heaters , it is important to look at the ways in which they incorporate arc flash mitigation features . When medium- or high-voltage equipment is used for industrial applications , it carries with it certain risks . Arc flash is an example of a well-known electrical risk that requires certain best practices to be followed to minimize damage and injury . When a new piece of medium-voltage equipment is developed , special attention should be given to such risks . This is certainly the case for large electric process heaters , which are becoming more popular in hydrocarbon processing applications .
The risk posed by arc flash Arc flashes typically occur when there is a short circuit in a system ( due to , for example , a dropped tool , buildup of corrosion or conductive dust or the presence of pests ). If the voltage is high enough , and if there is a path to ground or a lower voltage , the resistance of the air is overcome and results in an arc . Arc flash events can result in significant damage . As the energy release increases , it can cause fire and injury . If the energy release is high enough molten conductor metal and high-pressure plasma energy can escape from the cabinet , posing a risk to personnel . The potential arc flash energy is determined by several factors : Equipment voltage , available current and the duration
Arc flash event of the event . As the equipment voltage increases , the potential for arc flash hazards also increases . Low voltage systems operating below 400 volts do not have the energy to cause a significant arc flash hazard . Equipment operating at voltages between 400 volts and 600 volts can cause arc flash hazards , but their capacity to cause massive energy release is limited . Equipment operating at medium voltage ( above 600 volts ) has a high capacity for energy release . The available current is determined by the feed equipment upstream . While it may be practical in some cases to reduce the potential arc flash energy while limiting voltage or current , overall project cost can make this difficult . This makes reducing the duration of the event the most practical approach . Reducing the duration of the arc event also reduces the area of damage . The area of impact is not limited to the explosive blasts . The arc flash produces intense heat and light energy . People in the vicinity of the blast can experience injury from these effects even if they are not exposed directly to the explosion . Equipment surfaces can absorb the energy and experience high temperatures from the radiant energy , causing damage and requiring repair . Although arc flash incidents are relatively rare , their potential for damage , injury and death makes them a huge concern . Some estimates put the incidence of arc flash events roughly between five to 10 per day worldwide , or 3,500 per year . According to a 2021 article in the journal Safety , there were over 2,000 recorded hospitalizations in the U . S . due to electrical injuries , including arc flashes . Of these , 1,900 were non-fatal and 166 were fatal 1 . Although the article did not qualify fatalities in terms of whether they were due to arc flashes or other events , it is clear that arc flashes are on the more lethal end of the spectrum . Are there special risks with regard to arc flashes when it comes to process heating ? Yes and no . On the one hand , medium voltage process heaters are relatively new to many applications . Concerns about decarbonization , automation and safety have driven many to replace gas-fired heaters with larger electrical heaters (> one megawatt ) 2 ; these heaters thus represent a potential new source of risk , and
1
Casey , Tristan W ., Hannah M . Mason , Jasmine Huang , and Richard C . Franklin . 2021 . “ Shaping Frontline Practices : A Scoping Review of Human Factors Implicated in Electrical Safety Incidents ” Safety 7 , no . 4 : 76 . https :// doi . org / 10.3390 / safety7040076 .
38 Heat Exchanger World November 2022 www . heat-exchanger-world . com