MSHA issues alerts for ammonia & autotransformers

The Mine Safety and Health Administration (MSHA) recently issued safety alerts for autotransformers and ammonia.

These alerts provide reminders of regulations, dangers, and best practices to ensure safety when operating in and near equipment that uses autotransformers, as well as methods to reliably detect and protect against ammonia gas exposure.

Autotransformers can cause electric shock when contacting shuttle cars

Autotransformers being used by machine manufacturers 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. 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.

Best Practices

• Follow 30 CFR §75.900 (coal) and §57.12003 (metal/nonmetal) to provide adequate protection.
• Train qualified personnel conducting electrical examinations to safely identify the use of autotransformers and their potential hazards.
• Examine all mining equipment with autotransformers currently in service to ensure safe operating condition.
• Consult with manufacturers for compliant/approved alternatives.
• Contact your local MSHA district office for additional assistance.

Smell alone cannot reliably be used to monitor ammonia concentrations

Exposure to high levels of ammonia can cause serious health effects involving the 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.

Ammonia at Mine Sites

Ammonia is used on mine sites for chemical processing, refrigeration systems, emissions, and as a neutralizing agent. Exposure can occur due to equipment malfunctions, leaks, chemical mixing, or improper handling. Ensure proper ventilation in mines where ammonia is naturally occurring.

Ammonia Detection

Ammonia has a sharp, pungent smell that can be detected at levels as low as five parts per million (ppm). However, smell alone cannot be relied upon for detection and appropriate warning. Industrial hygiene sampling equipment should be used to monitor levels of ammonia and personal exposure.

Exposure Limits

The Threshold Limit Value-Time Weighted Average (TLV-TWA) for ammonia is 25 ppm. Ammonia is Immediately Dangerous to Life and Health (IDLH) at 300 ppm.

First Aid

If ammonia gas is inhaled, relocate the person to fresh air. If liquid ammonia contacts the body, remove contaminated clothes and rinse with water for at least 15 minutes. Immediately seek medical aid.

Stay informed on your required site-specific hazard awareness training including hazardous materials, warning signals, and evacuation procedures.