What is a proof test?

A proof test is an essential process used in rigging to verify the strength and integrity of a lifting sling or other rigging equipment. This test involves applying a force that exceeds the rated load of the equipment, but within a controlled manner to ensure that the item can handle loads above its specified capacity without permanent deformation or failure. This process helps in identifying any latent defects or weaknesses in the equipment that may not have been apparent through visual inspection alone.

By subjecting the sling to a higher stress level, operators gain confidence in the equipment's performance and safety before it is put into regular service. The goal of a proof test is to ensure reliability and safety without causing damage to the sling, unlike destructive testing, which focuses on exposing the limits of materials until they fail.