When a longwall shearer's detector indicates 2% methane around the machine, what action is required?

• A. Trip electricity supply to the machine
• B. Trip electricity supply to the cutters only
• C. Shut down ventilation and evacuate
• D. No action required until 3% is reached

Answer: (A)

Methane around a longwall machine is an ignition risk, so the first priority is removing any sources of ignition. Tripping the electricity supply to the machine immediately de-energizes all components that could spark or heat, removing the main ignition risk from the suite of equipment. Turning off just the cutters wouldn’t disable other energized parts of the shearer that could ignite methane, so it’s not sufficient. Shutting down ventilation would reduce dilution and could allow gas to accumulate, and waiting for a higher concentration isn’t acceptable practice. Therefore, the proper action is to cut power to the machine to eliminate ignition sources right away.