What does anti-two-block protection do?

• A. Increases lifting speed.
• B. Prevents hook block contact with boom tip or sheaves, protecting hoist and preventing uncontrolled loads.
• C. Locks the outriggers.
• D. Measures load weight.

Answer: (B)

Anti-two-block protection is a safety mechanism that stops the hoist before the hook block can touch the boom tip or the upper block. As the lower block gets close to the upper block, sensors or limit devices detect the approaching block and stop or slow hoisting to prevent two-blocking. This protects the hoist rope, sheaves, and other crane components from damage and prevents uncontrolled load movement or rope jamming. Two-blocking can lead to rope failure or sudden load drops, so this protection keeps operation within safe limits. It isn’t about increasing lifting speed, locking the outriggers, or measuring load weight; it specifically prevents block-to-block contact and the associated dangers.