Understanding the safety factors of the equipment you are working with is paramount no matter the industry you are working in. With this, it is important to comprehend the differences between working loads, and breaking loads – which may sound the same, but they are not. Any configuration of equipment is only as strong as its weakest, or lowest rated parts. Both terms are a form of rating.
The term working load limit, is most frequently used in rigging terminology, it was the cornerstone of engineering for many years. It is the breaking load of a component divided by an appropriate factor of safety – a safe load that was the maximum carrying capacity. The terms usually apply to equipment such as hooks, slings, shackles and the like.
The working load, sometimes also known as the safety working load, or normal working load (just to confuse things further) is the mass that the equipment being used can safely hold, lift, or lower without there being a fear of breaking. In shorter terms; the maximum load that can be applied to the product safely when in general service. This is most accurate when the product is new and without any ware. This is measured on a straight line pull only, and side pulling can produce different results. It is also important to make sure that all components in a system have the same working load limit.
The breaking load also can be known as the rated capacity. This measure is the force that the piece of equipment breaks when tested at as opposed to measure of mass it can hold. Force is consistently applied at a uniform rate of speed to ascertain the breaking load. The breaking load, or breaking strength as it is also called, is a vital part of the calculation of the working load limit.
The working load is one fifth of the minimum breaking strength. The tests which are undertaken in the laboratory are testing under normal environment type conditions and so when using in adverse weathers or other settings that may include different chemical levels, this should be taken into consideration.
The working load limit of any piece of equipment must never be exceeded, and components must be properly matched. As logic would suggest, it is best to avoid heavy impact shock loads, or any abstract movement such as winging or jerking. Anything like this can lead to stress on the product which leads to the breaking strength and the working load limit being exceeded causing the wider mechanism to fail.
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