Riser tensioner

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A riser tensioner is a device used on an offshore oil drilling rig or ship which keeps a positive pulling force on the riser pipe, independent of the movement of the drill rig or drill ship. The official name is Marine Riser Tensioner.

It may be clear that a riser is a thin string between the sea bottom and ship or rig. If there would be no tensioner and the ship or rig moves downwards, the riser would buckle; if the ship or rig lifts, high forces would be introduced in the riser. For this reason a number of Riser Tensioners (springs) are mounted between ship (rig) and riser. Each of these riser tensioners 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.

On board of a drill rig or drill ship, one find following tensioners:

• Drill string compensator
• Riser tensioner
• Guideline tensioner

Supplyers
Aker Kvaerner MH (Maritime Hydraulics)
Rucker Shaffer
Vetco
Brown Brothers/Vickers