Marine riser tensioner

A riser is a string of pipe between the sea bottom and ship or rig. If there were no tensioner and the ship or rig moves downward, the riser would buckle; if the ship or rig is raised, high forces would be transmitted to the riser. To counteract these forces, a number of riser tensioners (springs) are mounted between the ship (rig) and riser. Each riser tensioner consists out of a hydraulic cylinder with sheaves at both sides. The cylinder is connected to a number of high-pressure gas bottles via a medium separator. A wire rope is rigged in the cylinder; one end is connected to the fixed part of the tensioner, the other end is connected to the riser.

Onboard a drill rig or drill ship, various tensioners are used:

• Drill string compensator
• Riser tensioner
• Guideline tensioner

Suppliers
Aker Kvaerner MH (Maritime Hydraulics)
National Oilwell Varco
DTI LLC
Rucker Shaffer
Vetco
Brown Brothers/Vickers
Oceaneering