Steel riser top locking system

Abstract

A top locking system for a riser tube in a supporting tube is arranged on a floating vessel. The riser tube is inserted in the supporting tube and is mounted in a hang-off support tube. The top locking system is arranged at an upper end of the supporting tube and includes a plurality of hinged wedges arranged at an external peripheral wall of the upper end of the supporting tube. Each hinge wedge of the top locking system is rotatingly moveable from an opened to a closed position around a hinge shaft of a respective support hinge at the peripheral wall. The support hinge includes a pair of parallel brackets provided with eccentric bushes in which the hinge shaft is mounted.

1 . Top locking system for a riser tube in a supporting tube on a floating unit; the riser tube being inserted in the supporting tube; the riser tube being mounted in a hang-off support tube;
 the top locking system being arranged at an upper end of the supporting tube and comprising a plurality of hinged wedges arranged at an external peripheral wall of the upper end of the supporting tube; each hinge wedge being rotatingly moveable from an opened to a closed position around a hinge shaft of a respective support hinge at said peripheral wall, the support hinge comprising a pair of parallel brackets provided with eccentric bushes in which the hinge shaft is mounted.   
     
     
         2 . Top locking system according to  claim 1 , wherein in the closed position the hinged wedge is positioned between an external periphery of the hang-off support tube and an internal peripheral wall of the supporting tube. 
     
     
         3 . Top locking system according to  claim 1 , wherein the supporting tube is supported on a lower riser balcony of the floating vessel. 
     
     
         4 . Top locking system according to  claim 1 , wherein the riser tube is equipped with the hang-off support tube inserted in the supporting tube, and with a gap compensator structure at a lower end of the supporting tube positioned between the external wall of the hang-off support tube and the internal wall of the supporting tube. 
     
     
         5 . Top locking system according to  claim 1 , wherein an eccentricity of the eccentric bushes is configured to provide an inward or outward displacement of the hinged wedge towards or from a center of the supporting tube, when the hinged wedge is in or is approximating the closed position. 
     
     
         6 . Top locking system according to  claim 1 , wherein the floating unit is a floating production storage and offloading, FPSO, vessel. 
     
     
         7 . Top locking system according to  claim 1  wherein the top locking system comprises a number of hinged wedges around the periphery of the riser tube. 
     
     
         8 . Top locking system according to  claim 7 , wherein the number of hinged wedges is at least three. 
     
     
         9 . Top locking system according to  claim 1  wherein in the closed position the hinged wedge is positioned below a collar of the riser tube. 
     
     
         10 . Top locking system according to  claim 1 , wherein the hinged wedges are each rotatingly moveable by an actuator, preferably a hydraulic actuator. 
     
     
         11 . Top locking system according to  claim 10 , wherein each hinge is individually moveable by the actuator. 
     
     
         12 . Top locking system according to  claim 1 , wherein the supporting tube has a lengthwise opening over a portion of its circumference. 
     
     
         13 . An offshore floating unit comprising a top locking system according to  claim 1 . 
     
     
         14 . Top locking system according to  claim 2 , wherein the supporting tube is supported on a lower riser balcony of the floating vessel. 
     
     
         15 . Top locking system according to  claim 2 , wherein the riser tube is equipped with the hang-off support tube inserted in the supporting tube, and with a gap compensator structure at a lower end of the supporting tube positioned between the external wall of the hang-off support tube and the internal wall of the supporting tube. 
     
     
         16 . Top locking system according to  claim 3 , wherein the riser tube is equipped with the hang-off support tube inserted in the supporting tube, and with a gap compensator structure at a lower end of the supporting tube positioned between the external wall of the hang-off support tube and the internal wall of the supporting tube. 
     
     
         17 . Top locking system according to  claim 2 , wherein an eccentricity of the eccentric bushes is configured to provide an inward or outward displacement of the hinged wedge towards or from a center of the supporting tube, when the hinged wedge is in or is approximating the closed position. 
     
     
         18 . Top locking system according to  claim 3 , wherein an eccentricity of the eccentric bushes is configured to provide an inward or outward displacement of the hinged wedge towards or from a center of the supporting tube, when the hinged wedge is in or is approximating the closed position. 
     
     
         19 . The top locking system according to  claim 8 , wherein the number of hinged wedges is six. 
     
     
         20 . The top locking system according to  claim 10 , wherein the actuator is a hydraulic actuator.