What is anti-two block and why is it necessary?

• A. Anti-two block increases lifting speed
• B. Anti-two block prevents the hook block from contacting the boom tip or sheaves; it protects the hoist and load from entanglement and equipment damage; ensure the device is functional and never hoist past the designed limit.
• C. Anti-two block is optional
• D. Anti-two block only used for fixed cranes

Answer: (B)

Anti-two block is a safety feature that prevents the hook block from contacting the boom tip or the upper sheaves. If the block comes up too far, two-blocking can occur, which can yank the rope into the sheaves, overload the hoist, damage components, and even cause the load to drop or the crane to seize. The anti-two block system detects when the hook block is getting too close and stops hoisting or warns the operator before contact happens, keeping the rope, hoist, and load safe and preventing damage to the crane. It’s a necessary protection, not an optional add-on, and it’s used on many cranes, in various configurations, to reduce the risk of entanglement and equipment failure. It doesn’t speed up lifting; it protects against dangerous travel limits and ensures safe operation.