An anti-two-block system is used to prevent or warn the operator of a two-block condition on a crane.  Two-blocking is the dangerous condition where the lower hook block is raised until it contacts any part of the boom tip hardware.  The term comes from block and tackle terminology, describing when the blocks (or pulleys), upper and lower, come into contact with each other.

Two-blocking may occur while winching up, while telescoping the boom out, or when booming down (unless the winch is mounted on the boom).  Continuing any of these actions will cause the lower hook block to be drawn over the top sheave or cause the wire rope to break-either of which will cause the load to fall out of control to the ground.

This system can be integrated with swing limit and boom limit, our system can be applied in most of the offshore pedestal crane such as HSMC ROTO-30, HSMC ROTO-15, Unit Marine, Allied Marine, Manitex ML-2400, etc