Riser Tethers – Taking a Firm Grip

Overcoming the mechanical fatigue effects of subsea currents on risers and umbilicals is an area where Lanko®force Synthetic Riser Tethers are proving to be particularly effective. Made from Dyneema® DM20, a high modulus polyethylene (HMPE) rope, the tethers are designed to hold risers and umbilicals in position, connected to subsea production systems such as well manifolds, wellheads, Christmas trees and well jumpers. 

Lankhorst Offshore has supplied several Riser Tether sets recently. Configurations can be customised to suit the application. In one instance, Lanko®force rope riser tethers have been used for permanent subsea anchoring of flexible water injection risers in 300-350m water depths. The water injection riser is suspended in a free hanging catenary configuration. To hold the riser securely in position a V-shaped, 28.5m Lanko®force Dyneema® riser tether, with Dyneema® jacket, is used to provide the axial restraint needed for a friction clamp tethered to an anchor.

Typically, the riser tether has a Lanko®force 84mm diameter rope construction with a 12 strand braided rope core made from Dyneema® DM20. The high modulus polyethylene core provides the strength and mechanical performance expected of these long-term tethers. The entire rope core is protected by a braided Dyneema® jacket and polyurethane coating, and includes ROV handling points for ease of installation.

“The riser and umbilical tethers are very technical products that demand the highest levels of mechanical and fatigue performance over many years. The strength and durability of Lanko®force Dyneema® DM20 makes it ideal for just this type of application,” says Sergio Leite, sales director, Lankhorst Offshore.