What device is used to limit the hoisting operation on a crane?

The anti two-blocking device is essential for limiting the hoisting operation on a crane. This device prevents the hook block from being drawn too close to the crane's boom or other structures, which can lead to dangerous collisions or equipment damage. By ensuring that there is adequate spacing and preventing overhoisting, the anti two-blocking device enhances safety during lifting operations. When the hook block reaches a predetermined height, the device triggers a stop to the hoisting operation, thereby helping to protect both the equipment and personnel.

While other devices listed may have their own specific functions, they do not directly address the critical limit of hoisting operations in the same way. The luffing jib limiting device pertains to the movement of the jib itself, the hoist drum indicator provides information on the amount of rope that has been deployed but does not limit movement, and the boom angle indicator shows the angle of the boom but does not impose operational limits. Thus, the correct choice focuses exclusively on maintaining safe hoisting limits.