Knot vs. Hardware for Attaching Load
You need to attach a lifting sling to a load that has no lifting eyes. The load is a bundle of steel pipes. You have a wire rope sling with eyes at both ends. You consider tying a knot in the sling to form a loop, but a colleague suggests using a shackle to connect the eyes. The load weighs 1,500 lb. The sling is rated for 2 tons in a vertical hitch.
1. What are the risks of tying a knot in a wire rope sling?
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Tying a knot in a wire rope sling creates sharp bends that can damage the wire rope and significantly reduce its strength. Knots can reduce the efficiency of the sling by 50% or more. Also, knots can slip or come undone under load. According to rigging standards, knots should not be used in wire rope slings for lifting. The sling's rated capacity is based on proper use with eyes and hardware. Therefore, using a knot is unsafe and may cause failure.
2. What is the correct way to attach the sling to the pipe bundle?
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Use a shackle to connect the two eyes of the sling, forming a loop around the bundle. Ensure the shackle is rated for the load and is properly sized. The sling should be in a basket hitch around the bundle, with both eyes on the shackle. This provides a secure attachment without knots. The capacity of the sling in a basket hitch is typically double the vertical capacity, but depends on the angle. For a vertical basket, capacity is 2 times the single leg vertical capacity, but if the legs are not vertical, it's reduced. Here, the sling is 2 tons vertical, so basket capacity is 4 tons if vertical. The load is 1.5 tons, so it's safe. Ensure the shackle pin is fully engaged and the load is balanced.