The single largest category of electrical injuries in the mining industry is non-contact electrical burns caused by arc flash events, according to an investigation conducted by the National Institute for Occupational Safety and Health (NIOSH) over 11 years. Even though this study found that the majority of mining electrical injuries are caused by electrical arcs, few miners are aware that such a hazard exists. (1)
OSHA defines arc flash as, “a phenomenon where a flashover of electric current leaves its intended path and travels through the air from one conductor to another, or to ground.” (2) An arc flash can be caused by many factors found in mining environments including dust, condensation, corrosion, and more.
Accounting for arc flash can complicate the efficiency of safely connecting and disconnecting mining, quarrying, and aggregate electrical equipment. The solution? MELTRIC Switch-Rated plugs and receptacles.
Eliminating Arc Flash Exposure
Drawing an arc during plug removal is an inherent hazard with traditional pin and sleeve and twist-type devices. By contrast, MELTRIC Switch-Rated devices isolate the making and breaking of the contacts in an enclosed arc chamber. The plug contacts are de-energized and isolated from live parts before the plug can be physically removed.
When the receptacle’s OFF button is pushed, its spring-loaded operating mechanism instantly opens the contacts to break the circuit and ejects the plug to its OFF position. The quick (15 milliseconds) breaking of the contacts minimizes arcing; any arcing that does occur is safely contained within the internal and enclosed arc chamber.
In the OFF position, the plug contacts are dead and separated from live parts by a safe distance. Isolated and inaccessible to users, all contacts are fully contained within an enclosure formed by the plug’s skirted casing and the receptacle’s casing.
The rotation of the plug required prior to its removal from the receptacle automatically closes and locks the safety shutter. This ensures that potential arc paths and access to live parts are blocked before the plug can be removed. There is no possibility of drawing an arc and the hazard is eliminated.
Additional Safety Advantages
MELTRIC DS and DSN Series Switch-Rated plugs and receptacles combine the safety of a switch with the convenience of a plug and receptacle in one reliable, cost-effective device. They provide user safety, code compliance, and operating cost benefits that are not possible with other devices.
Switch-Rated plugs and receptacles provide a convenient ‘line of sight’ disconnect. With their UL/CSA ratings for “Branch Circuit Disconnect Switching” up to 200 A and “Motor Circuit Disconnect Switching” up to 100 HP. Switch-Rated devices are an approved NEC disconnect switch. They provide a safe and convenient plug-and-play disconnect switch everywhere they are used to make connections eliminating the need for ancillary disconnect switches.
Switch-Rated plugs and receptacles have environmental ratings for a watertight operation. They achieve their rated watertightness simply by connecting the plug and receptacle. There is no need to thread on or turn watertightness rings as is required on many pin and sleeve devices. DSN Series devices provide Type 4X and IP69K/IP69 watertightness, while the DS Series provides Type 3R as standard or Type 4X as an option.
Why MELTRIC?
With their unique features and capabilities, MELTRIC products provide users with a safer and more reliable product. MELTRIC butt-style contacts provide longer operating lives, help users reduce equipment costs, and remove arcing hazards caused by live contacts or wrongful disconnection. These advantages, together with competitive pricing, short lead times, and a 5-year warranty on electrical contacts make MELTRIC products the best overall value in the plug and receptacle/connector market.
MELTRIC is focused on providing customers with the best overall value by offering the safest, highest quality, and most reliable plugs and receptacles, and by backing them with outstanding service and support.
View the published article: http://canadianminingmagazine.com/arc-flash-safety-in-mining/
References:
- Kowalski-Trakofler, KM. Barrett, EA. “Mining Publication: Reducing Non-Contact Electric Arc Injuries: An Investigation of Behavioral and Organizational Issues” Center for Disease Control and Prevention, https://www.cdc.gov/niosh/mining/works/coversheet1462.html, Accessed 4 Aug. 2022.
- “Workplace Safety Awareness Council” Occupational Safety and Health Administration, https://www.osha.gov/sites/default/files/2018-12/fy07_sh-16615-07_arc_flash_handout.pdf Accessed 4 Aug. 2022