Two-blocking can occur when the hook block contacts the boom or top blocks. Which of the following is an effective prevention method?

Two-blocking can occur when the hook block contacts the boom or top blocks. Which of the following is an effective prevention method?

• A. Two-blocking is when the load is suspended by two lines.
• B. Two-blocking occurs when the hook block contacts the boom or top blocks.
• C. Two-blocking happens when the operator loses sight of the load.
• D. Two-blocking occurs when the crane's engine stalls.

Answer: (B)

The main concept being tested is recognizing two-blocking and how to prevent it. Two-blocking occurs when the hook block contacts the boom or the top blocks, which can jam the hoist rope and cause damage or a crane outage. An effective prevention method is to ensure there is enough clearance between the hook block and the boom/top blocks during hoisting and lowering. This means using anti-two-blocking devices or upper-limit controls, keeping proper rigging lengths, and observing the boom angle and load path so the hook block never comes into contact with the upper works. Understanding the exact condition that defines two-blocking is essential to preventing it; the other options describe unrelated issues and do not address prevention of two-blocking.

The main concept being tested is recognizing two-blocking and how to prevent it. Two-blocking occurs when the hook block contacts the boom or the top blocks, which can jam the hoist rope and cause damage or a crane outage. An effective prevention method is to ensure there is enough clearance between the hook block and the boom/top blocks during hoisting and lowering. This means using anti-two-blocking devices or upper-limit controls, keeping proper rigging lengths, and observing the boom angle and load path so the hook block never comes into contact with the upper works. Understanding the exact condition that defines two-blocking is essential to preventing it; the other options describe unrelated issues and do not address prevention of two-blocking.