Why does an Anti-Two-Block alarm activate when the hook is fully lowered?
The A2B alarm activates when lowered because the hook block contacts or approaches the boom head, triggering the proximity sensor or weight block switch.
Anti-Two-Block systems activate when the hook block gets too close to the boom head or load block, which can occur during lowering operations if the operator continues lowering past the safe limit. The system uses either a proximity sensor, weight block assembly, or cable-actuated switch to detect when the hook block approaches the boom head within a predetermined distance, typically 18-24 inches.
Remember: "Hook Hits Head = A2B Alert" (Hook block contacts boom head triggers the alarm)
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