Which device helps prevent two-blocking during lifting?

• A. Anti-Two-Blocking Devices
• B. Boom Angel Indicator
• C. Personal Fall Arrest System
• D. Load-sensing pin

Answer: (A)

Preventing two-blocking relies on controlling how far the hoist rope can be reeved so the hook block can’t come into contact with the boom tip or upper works. Anti-Two-Blocking Devices monitor the position of the hook block and automatically limit or stop hoist movement when it gets too close, maintaining a safe clearance. They can be simple mechanical switches tied to the hoist line or more advanced electronic sensors that signal the hoist to stop or slow down. This directly stops the dangerous situation where the rope could jam, cause equipment damage, or drop the load.

The other devices serve different purposes: a Boom Angle Indicator warns when the boom is at an unsafe angle, a Personal Fall Arrest System protects a worker from falls, and a Load-sensing pin helps ensure you don’t lift beyond rated capacity. None of these specifically prevent two-blocking.