Challenges in assurance of high value large diameter ropes used in deep water subsea construction activities

Increased subsea activities in ultra-deep waters have augmented the use of large diameter wire ropes in excess of 100 mm diameter and 3000 m long. The life~me performance characteristics for such ropes are typically defined by scaling-up the theory developed and proven on smaller diameter designs. This scaling-up may not fully cover aspects such as increased internal heat, corrosion, wear and interaction of wires within multi-layer strands. Although an age based discard criterion is successfully applied within subsea construction, there are questions about its applicability to large diameter mul~stranded low rotation high value ropes. The cost impact of discarding too-ear1y or too-late is significant. Hence the strong incentive to redefine a retirement criterion for high value ropes. This paper presents the challenges in assurance of high value large diameter ropes and discusses the findings of condition assessment tests on a 120 mm diameter rope, discarded after si)( years in service with full maintenance and operational history.

Author(s): R.B. Kante and D. Cannell