General Crane Safety Practice Test

The correct angle of 20 degrees from the vertical is critical in ensuring the safe use of shackles and wire rope slings at their full lifting capacity. When the angle exceeds this threshold, the load-sharing mechanism of the rigging system can become compromised. This is due to the increased forces exerted on the sling or shackle as the angle increases, which can lead to additional stress and potential equipment failure.

At angles greater than 20 degrees, the effective working load limit of the sling decreases due to the geometry of the lift, resulting in a higher risk of accidents. Therefore, adhering to the 20-degree guideline allows for optimal performance of the rigging equipment while maintaining safety during lifting operations. This standard helps ensure that the rigging is used within a safe working range and minimizes the risk of accidents or equipment failure.