Improving Durability of ROV Tether Cables by UHMWPE Fiber

Abstract

Abstract This paper describes the durability enhancement of Nexans' conventional ROV tether cable design by using a strength member made with a bending optimized Ultra-High Molecular Weight PolyEthylene (UHMWPE; also refered to as HMPE) fiber, manufactured by DSM Dyneema and branded as Dyneema®, and herewith creating opportunities for more costeffective ROV operations and more flexibility in the design of ROV tether cables. The improved ROV tether cable is manufactured by Nexans and branded as ENABLE®. As a physical connection between a Remote Operating Vehicle (ROV) and its tether management system (TMS), ROV tether cables are exposed to small bending diameters and relatively sharp directional changes in the TMS. During ROV operations the cables are exposed to axial loading, severe multiple bending in arbitrary planes and hydrostatic pressure. The internal friction caused by motions and hydrostatic pressure induces mechanical deterioration of the strength member in ROV tether cables, hence a loss of functionality and regular re-termination and cut-backs of the ROV tether cable. In conventional tether cable designs aramid fibers are commonly applied in contra-helically stranded layers around an electro-optical core. After a while in operation internal abrasion, misalignment and compressive failure of these fibers, especially at the section of the tether cable closest to the ROV, become apparent. Based on its physical characteristics, UHMWPE fiber holds promise to overcome these failure modes.