Grade of Chain: NACM (National Association of Chain Manufacturers & ASTM (American Society for Test Materials) classify chains in various grades. The higher the grade, the higher the working load limit for the same size of chain.
Working Load Limit (WLL): (rated capacity) Is the maximum working load that should be applied In direct tension to an undamaged straight length of chain.
Proof Test: (manufacturing test force) Is a term designating the minimum tensile force which has been applied to a chain under a constantly increasing force In direct tension during the manufacturing process. These loads are manufacturing integrity tests and shall not be used as criteria for service or design purpose.
Minimum Breaking Force: The minimum force at which the chain during manufacture has been found by testing to break when a constantly increasing force is applied in direct tension. Breaking force values are not guarantees that all chain segments will endure these loads. This test is a manufacturer’s attribute acceptance test and SHALL NOT be used as criteria for service and design purpose.
Overhead Lifting: The process of lifting that would elevate a freely suspended load to such a position that dropping a load would present a possibility of bodily injury or Property damage.