Measuring Chain Elongation

Measuring Chain Elongation

Chain elongation is an easy way for the customer to determine the wear on the internal components of the chain just by taking a few measurements while the chain is on the conveyor. The measurement can then be compared to the chain’s original length and used to determine how much life is remaining in the chain.

To measure chain elongation, you will first need to follow any and all safety guidelines to lockout the conveyor and remove any guards needed to gain access to the chain. Usually, a 10 pitch section of chain is preferred, but more or less can be used depending on access to the chain. When taking the measurement on the chain there are several locations you can measure from and to, but the measurement needs to be taken from a consistent place. In other words, if the measurement starts from the centerline of the pin it will need to end on the centerline of the pin approximately 10 pitches away, or however many pitches are being measured.  Other common places to measure to and from would be the front edge of the pin head or the front edge of a sidebar. Once this measurement is taken it can be used in the formula below to determine the chain’s elongation.  Once the chain elongation is determined the rules of thumb are as follows:

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RWL vs. AUS – An Engineering Perspective

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RWL vs. AUS  – An Engineering Perspective

What are Rated Working Load (RWL) and the Average Ultimate Strength (AUS) of an engineered class chain and what do they mean?

First let’s tackle the AUS and a general overview of how it is calculated. The AUS is a calculated value from the chain manufacturer of the average breaking strength of the chain. The published AUS rating is generally the lowest calculated value between the following: the sidebar’s tensile strength, the sidebar’s shear strength and the pin’s shear strength (see Figure 1). Generally speaking this number should not be used when sizing a chain for a particular application because this is the breaking limit of the chain; the chain should never equal or exceed this value as it will result in total chain failure. It should be considered into your chain choice when a higher fatigue strength is required for the more demanding applications.

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