Trunnion mounted pivoting riser support for offshore mooring systems

Abstract

A riser connected by a trunnion mounted/pivoting riser support to a disconnectable body or to a riser table of a permanently connected turret. The trunnion includes a trunnion housing and trunnion pivot. The trunnion housing is arranged to allow a riser to pass through it and up to a vessel turret where the disconnectable body is connected to the turret. The trunnion pivot allows the trunnion housing and riser to pivot about a horizontal axis, allowing a disconnectable body to submerge to the sea floor.

What is claimed is:  
     
         1 . An arrangement for supporting an upper end of a riser to a riser termination body which is connected to an offshore structure comprising, 
 a trunnion including a trunnion housing and at least one trunnion pivot connected to said housing,    said trunnion housing arranged and designed to support said upper end of said riser and having a path by which fluid connection is established between the upper end of said riser and a top position of said housing,    said trunnion pivot being coupled to said termination body so that said trunnion and said upper end of said riser are capable of rotation about said pivot.    
     
     
         2 . The arrangement of  claim 1  wherein, 
 said upper end of said riser passes through a path through said trunnion housing, and  
 a riser end fitting is connected to the upper end of the riser, said riser end fitting being arranged and dimensioned to prevent said riser from being pulled downward through said path of said trunnion housing.  
 
     
     
         3 . The arrangement of  claim 1  wherein, 
 said at least one trunnion pivot includes two pivot members disposed on opposite sides of said trunnion housing,  
 said two pivot members being connected to said riser termination body in an arrangement so that said trunnion housing is capable of rotation with respect to said riser termination body about an axis through said pivots.  
 
     
     
         4 . The arrangement of  claim 3  wherein said two pivot members are directly connected to said trunnion housing.  
     
     
         5 . The arrangement of  claim 1  wherein, 
 said trunnion pivot is linked to said trunnion housing by a connection member.  
 
     
     
         6 . The arrangement of  claim 2  further comprising, 
 a bend stiffner positioned about said riser and connected to a lower end of said trunnion housing.  
 
     
     
         7 . The arrangement of  claim 1  wherein, 
 said offshore structure is a turret of an offshore production vessel.  
 
     
     
         8 . The arrangement of  claim 7  wherein, 
 said riser termination body is a disconnectable body arranged and designed for disconnectable connection to said turret of said offshore production vessel,  
 said riser includes floatation between a lower end of said riser connected to the sea floor and said upper end of said riser, and  
 said trunnion housing is arranged and designed so that said trunnion housing is capable of rotation with respect to said disconnectable body so that said upper end of said riser remains rotatably supported by said body when said body disconnects from said offshore production vessel and sinks toward said sea floor.