Test method for determining the Assured Residual Life Span (ARELIS) of polyester mooring ropes

A great many specifications, engineering guides and test results relating to polyester mooring ropes have been published. Now, in 2001, this type of rope is being introduced in the Gulf of Mexico. One recent area highlighted is how to inspect ropes in service and what measures need to be taken when minor damage occurs. This article proposes a test method to measure the Assured Residual Life Span (ARELIS) of a mooring rope. This method is based on an idea proposed by Coleman in the 1950s and worked out by Zhurkov in the 1960s. They argued that structural molecular changes (in this report indicated by the "Damage" parameter) occur throughout the lifetime of a polymeric sample. The ARELIS can be tested using a short creep test at a higher than normal load on a sub-rope of a mooring rope insert. The effect of storms can also be taken into account. For a parallel rope construction the effects of reduced load bearing area due to cuts can be predicted. The simplest method of compensating for visual damage in the short term, without undermining the inserts ARELIS test plan, is to reduce pretension.