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Working Load Limit (WLL)
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The Working Load Limit is the maximum load which should ever be applied to the product, even when the product is
new and when the load is uniformly applied – straight line pull only. Avoid side loading. Ail catalog ratings are based
upon usual environmental conditions and consideration must be given to unusual conditions such as extreme high
or low temperatures, chemical solutions or vapors, prolonged immersion in salt water, etc. Never exceed the Work
ing Load Limit.
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Proof Test Load (Proof Load)
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The term "Proof Test" designates a quality control test applied to the product for the sole purpose of detecting defects
in material or manufacture. The Proof Test Load (usually twice the Working Load Limit) is the load which the product
withstood without deformation when new and under laboratory test conditions. A constantly increasing force is
applied in direct line to the product at a uniform rate of speed on a standard pull testing machine. The Proof Test Load
does not mean the Working Load Limit should ever be exceeded.
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Breaking Strength/Ultimate Strength
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Do not use breaking strength as a criterion for service or design purposes. Refer to the Working Load Limit instead.
Breaking strength is the average force at which the product, in the condition it would leave the factory, has been
found by representative testing to break, when a constantly increasing force is applied in direct line to the product at
a uniform rate of speed on a standard pull testing machine. Proof testing to twice the Working Load Limit does not
apply to hand-spliced slings. Remember: Breaking Strengths, when published, were obtained under controlled laboratory conditions. Listing of the Breaking Strength does not mean the Working Load Limit should ever be exceeded.
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Design Factor (sometimes referred to as safety factor)
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An industry term usually computed by dividing the catalog Breaking Strength by the catalog Working Load Limit and
generally expressed as a ratio. For example: 5 to 1.
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Shock Load
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A load resulting from rapid change of movement, such as impacting, jerking or swinging of a static load. Sudden
release of tension is another form of shock loading. Shock loads are generally significantly greater than static loads.
Any shock loading must be considered when selecting the item for use in a system. Avoid shock loads as they may
exceed the Working Load Limit.
