The ease of deploying synthetic fibre tethers makes them an attractive choice for tethering deepwater risers and umbilicals. Onshore too, Lankhorst Offshore tethers are proving their worth in submarine power cable laying in the remote Norwegian countryside.
Deepwater tethers, developed and manufactured by Lankhorst Offshore, play a valuable role in securing risers and umbilicals from fatigue caused by the effects of subsea currents, and mooring mid-water arches. Fibre tethers such as the Lanko®Force and Gama98® with Dyneema® have significant performance advantages over chain and steel wire tethers. As well as being lighter and with almost neutral buoyancy, synthetic fibre tethers have no corrosion or fatigue issues and allow easy system installation.
Power Cable Installation
In addition to deepwater riser projects, synthetic fibre tethers have recently been used to install power cables. For example, Lankhorst Offshore has supplied fibre rope tethers to secure a submarine power line for a Norwegian power line project. Faced with laying four power lines across a fjord approximately 8km wide and 526 meters at its deepest point, Lankhorst tethers have been used to provide a holdback tether arrangement for each cable as it makes the transition between the fjord’s rock wall and seabed at 165m water depth. Constructed from Lanko®Force Dyneema® DM20 12 strand braided rope with a braided polyester jacket, the ten 8m synthetic fibre tethers feature a polyurethane coated spliced eye at both ends and ROV handles for ease of positioning subsea.
“Wherever pipe or cable has to be protected from excessive movement underwater, our tethers are the ideal solution, says Sergio Leite, Sales Director, Synthetic Tethers, Lankhorst Offshore. “Our tethers are engineered to meet specific project conditions. In this way we are able to ensure a typical service life of over 20 years.”