In February, the agency issued a safety warning and best practices for work around autotransformers as they pose a potential ground fault hazard.
“It is hazardous when a ground fault within the autotransformer occurs and goes undetected by the ground fault protection circuit. Miners and electricians have reported being shocked when contacting shuttle cars,” MSHA noted in its alert.
Shuttle cars equipped with autotransformers may cause a ground fault condition that goes undetected. These hazards exist when an autotransformer ground fault occurs, and the ground fault protection circuit is inadequate because the ground fault current is too low to be detected.
It is suggested that best practices for mines include following 30 CFR §§75.900 (coal) and 57.12003 (metal/nonmetal) to provide adequate protection; training qualified personnel conducting electrical examinations to safely identify the use of autotransformers and their potential hazards; and examining all mining equipment with autotransformers currently in service to ensure safe operating condition.
MSHA also suggested consulting with manufacturers for compliant/approved alternatives, and encouraged mines to contact their local MSHA district office for additional assistance.
Health alert issued concerning ammonia exposure
MSHA distributed a health alert to all U.S. mining operations about exposure to high levels of ammonia (NH3), which can cause serious health effects involving eyes, lungs and skin.
“Miners working with or around ammonia should take caution. Use engineering controls, such as ventilation, and if respirators are in use, ensure that an ammonia-specific filter cartridge is used. “You cannot rely on sense of smell to monitor levels. NH3 can numb the sense of smell.”