Means For Applying Tension To A Top Tension Riser

Abstract

A means for applying a controlled tension to a top tension riser on a floating offshore structure. The invention combines a mechanical tensioner device and buoyancy can to apply controlled tension to an individual riser or group of risers supported by a floating offshore structure. The buoyancy can applies static tension force on the riser(s). The mechanical tensioner applies additional tension force to assist the can in limiting the stroke of the riser as the supporting structure is displaced from its nominal position

1 . In an offshore floating structure having one or more top tensioned risers, a means for applying tension to the risers, comprising:
 a. a mechanical tensioning device supported by the offshore floating structure;   b. a buoyancy can supporting the riser; and   c. a line connecting said mechanical tensioning device to said buoyancy can.   
   
   
       2 . The tension applying means of  claim 1 , wherein said mechanical tensioning device is attached directly to the offshore floating structure. 
   
   
       3 . The tension applying means of  claim 1 , wherein said mechanical tensioning device is attached to a tensioner support structure mounted on the offshore floating structure. 
   
   
       4 . The tension applying means of  claim 1 , wherein said mechanical tensioning device comprises a hydraulic cylinder and ram. 
   
   
       5 . A method for applying tension to top tension risers on a floating offshore structure, comprising:
 a. providing a buoyancy can supporting the riser;   b. providing a mechanical tensioning device supported by the offshore floating structure; and   c. attaching a line between said buoyancy can and said mechanical tensioning device such that said buoyancy can and mechanical tensioning device work in combination to support the riser.