Enable™ Tether cables for ROVs with new high performance yarns
Remote Operated Vehicle (ROV) cables are subject to dynamic movement, stress, currents, and rough seas. Conventional tethers use aramid fibers. However, a new bending-optimized polymer yarn from Dyneema ® used in Enable™ developed by Nexans Norway, boosts their flexibility and extends their life time.
ROV tether cables are exposed to repeated bending at small diameters and low tension, followed by occasional snap loads. High performance polymer yarn handles hydrostatic pressure at great depths, and is resistant to fatigue and friction damage. It is also chemically stable in seawater oils and other fluids used in the oil & gas industry.
The deep-sea challenge
A typical subsea ROV has a tether cable between the vehicle and the garage, or tether management system (TMS), to transmit electrical power, optical signals and mechanical payloads through a light and flexible cable. Operational stress causes synthetic fibers (used as strength members) to deteriorate, especially at the ROV end, resulting in re-termination and an unfortunate shortening of a vital cable. So we needed to lower the coefficient of friction, increase abrasion resistance, and reduce sensitivity for localized compression failures, while maintaining axial stiffness and critical break strength.
By selecting this new fibre, we achieved a significant improvement in the strength member. The Enable™ tether designs are manufactured with Dyneema ® yarns from DSM and were chosen to ensure prolonged service life on existing systems. Less termination work on vessels, shorter shutdown times, more flexibility in design, and lower weight to accommodate more copper conductors in a smaller diameter are all advantages. This proven technology leads to less voltage loss, longer excursion lengths, and lower failure and replacement costs for customers. The Enable™ designs have been in operation in harsh environments and have been successfully tested by third parties.