Discard criteria: A review

As a functional load bearing component rope is probably unique in that it invariably does not last as long as the system in which it is deployed, and its failure is likely to have significant consequences in terms of risk to life, financial loss, or both. Part of the engineering community’s response to these risks is to define sets of “discard criteria” to define conditions which determine the timing of replacement. But these criteria which at first seem straightforward must in practice be subject to extensive “terms and conditions” raising additional considerations including such as the reliability of the inspection process and confidence regarding details of future use. The increasing use of MRT to assist in rope inspection, especially where “invisible” internal degradation is to be expected, raises further questions as to how relevant criteria should be defined recognising the differing levels of sensitivity evident in the range of instruments available. This paper discusses the underlying philosophy of rope certification, and to set out the issues impacting on making appropriate discard decisions.

Author(s): C.R.Chaplin