Bend Over Sheave Durability of Fibre Ropes for Deep Sea Handling Operations

Abstract

This paper describes work performed within a Joint Industry Project aiming to evaluate the lifetime of deep sea handling ropes. Various HMPE (High Modulus Polyethylene) fiber ropes, with and without coatings, have been studied under both tensile and cyclic bend over sheave (CBOS) loading. A large test program has enabled both tension-cycle to failure relationships and empirical expressions for residual strength after cycling to be determined. A special device was then developed to apply a known couple to the sheave, allowing both dynamic friction measurements to be made and the influence of applied couple on cycles to failure to be measured. These experimental data were used in the development of a numerical model which can be used to study the influence of rope and sheave parameters.

An empirical model to predict the lifetime of braided HMPE handling ropes under cyclic bend over sheave (CBOS) loading

“…These do not give the same result for a new rope, and preliminary tests showed that the latter result in lower break loads, both for new ropes and after cyclic loading, Fig. 5 (Davies et al, 2013). A direct tension value of residual strength (although a practical in-service retirement criteria) may therefore provide an over-optimistic evaluation of remaining properties in a deep sea handling application.…”

“…It should be emphasized that this is a standard rope design. There are several enhanced bending designs available commercially, some of which were also tested in the project (see Davies et al, 2013), and the approach developed here can be applied to other designs. The specimens tested were around 8 m long, with eye splices at both ends.…”

“…Numerical modelling has also indicated that the main energy dissipation is the result of internal abrasion, both between strands and between assembled yarns within the strands, and provided a tool which can be used to evaluate rope and sheave parameters to optimise lifetime (Davies et al, 2013).…”

“…(Pickett et al, 2009), but there is currently no model capable of simulating the repeated loading of a braided rope over a sheave. Within the present project numerical modelling was performed, by applying software specifically developed for fibrous materials (Durville, 2010(Durville, , 2012 and some first results have been presented (Davies et al, 2013). However, that work will be presented in detail elsewhere.…”

Tensile properties of polypropylene fibers

“…Another approach has been developed by Durville (2010), based on finite element modeling with special algorithms to account for the interactions between elements. This has been used to simulate the tension, torsion, and bend over sheave response of braided fiber ropes (Vu et al, 2015;Davies et al, 2013Davies et al, , 2016.…”