The working load limit (safety factor) for hoist rope on an overhead crane is typically 5 to 1.

The working load limit (safety factor) for hoist rope on an overhead crane is typically 5 to 1.

• A. 3 to 1
• B. 4 to 1
• C. 5 to 1
• D. 10 to 1

Answer: (C)

Key idea: the safety margin for hoist rope is built into the working load limit by using a 5:1 safety factor. In practice, the rope’s breaking strength is about five times the maximum load the crane is allowed to lift, which creates a cushion for dynamic effects like starting, stopping, and shocks, plus wear, bending over the drum, and potential minor damage. This margin helps prevent rope failure during normal operation and under unexpected conditions. A smaller factor, such as 3:1, wouldn’t leave enough room for those dynamic and wear factors, while a much larger factor like 10:1 would be unnecessarily conservative and costly for typical cranes. Therefore, 5 to 1 is the standard, balancing safety with practicality.

Key idea: the safety margin for hoist rope is built into the working load limit by using a 5:1 safety factor. In practice, the rope’s breaking strength is about five times the maximum load the crane is allowed to lift, which creates a cushion for dynamic effects like starting, stopping, and shocks, plus wear, bending over the drum, and potential minor damage. This margin helps prevent rope failure during normal operation and under unexpected conditions. A smaller factor, such as 3:1, wouldn’t leave enough room for those dynamic and wear factors, while a much larger factor like 10:1 would be unnecessarily conservative and costly for typical cranes. Therefore, 5 to 1 is the standard, balancing safety with practicality.