For a longwall shearer, what are the detector requirements, alarm and trip settings, and SOP requirement?

• A. Must have at least 1 automatic methane detector to detect general body methane; alarm at 1%; trip cutters at 1.25%; trip the machine at 2%; must have an SOP for action when the power trips or detector fails in service.
• B. Detectors are optional and no SOP is required.
• C. Only occupational exposure limits apply with no detector trip actions.
• D. Detectors must monitor only methane above 5% and trigger ventilation changes.

Answer: (A)

The main idea is that longwall equipment must use automatic methane detection with clearly defined alarm and shutdown responses, plus a formal procedure for failures. A detector keeps watch for general body methane; an alarm at 1% provides early warning so people can respond before conditions worsen. If methane reaches 1.25%, the system trips the cutters to halt active extraction and cut the risk of ignition while allowing a controlled stop. If methane climbs to 2%, the entire machine trips to stop operations and further gas release. A formal standard operating procedure is required to spell out exactly what actions to take if power trips or a detector fails, ensuring a consistent, safe response. This combination—automatic detection, specific alarm and trip thresholds, and a documented SOP—is why this option is the correct approach. Detectors are not optional, and relying on higher methane levels or omitting an SOP would leave the system unsafe and non-compliant.