Worn Sling and Sharp Corner
You are rigging a 1,200 lb steel plate with a 2-leg bridle using 1/2-inch wire rope slings. The slings are in good condition except for one that has several broken outer wires and a kink near the hook. The plate has sharp edges. The load must be lifted 10 feet. You have corner protectors available but they are worn and thin.
1. What inspection criteria determine if the wire rope sling with broken wires and a kink is safe to use?
Read the worked answer
According to ASME B30.9, a wire rope sling shall be removed from service if there are 10 or more randomly distributed broken wires in one rope lay, or 5 or more broken wires in one strand in one rope lay. Also, a kink is considered severe damage and the sling must be removed from service. Since the sling has a kink, it is not safe to use regardless of the number of broken wires. Therefore, that sling must be removed from service.
2. How should you address the sharp edges of the plate when using the remaining sling?
Read the worked answer
Sharp edges can cut or crush a wire rope sling, reducing its capacity. The worn and thin corner protectors may not provide adequate protection. You should use suitable corner protectors that are in good condition, or otherwise protect the sling from the edges. If adequate protection is not available, the lift should not proceed. Additionally, the sling angle affects capacity: for a 2-leg bridle, the tension in each leg increases as the angle from horizontal decreases. You must ensure the sling angle is not less than 30 degrees from horizontal (or per manufacturer) and that the load is balanced.