Riser tensioner for an offshore platform

Abstract

An upgraded riser tensioner ( 10 ) includes a cylinder end sheave body ( 12 ), a hydraulic cylinder ( 22 ), a rod ( 24 ) extending upward from the hydraulic cylinder, and upper sheave assembly ( 20 ) supported on the rod. A piston ( 26 ) is movable within the hydraulic cylinder. A blind end cover ( 22 ) is spaced at the lower end of the hydraulic cylinder. An adaptor plate ( 30 ) is spaced between the blind end cover and the cylinder and sheave body, and includes circumferentially spaced interior bolt holes and circumferentially spaced external bolt holes.

1 . An upgraded riser tensioner for an offshore vessel or platform, comprising:
 a cylinder end sheave body secured to the offshore platform, the cylinder end sheave body housing a lower sheave assembly;   a hydraulic cylinder extending upward from the cylinder end sheave body;   a rod extending upward from the hydraulic cylinder;   an upper sheave assembly supported on the rod;   a piston movable within the hydraulic cylinder and connected to the rod;   a blind end cover spaced at a lower end of the hydraulic cylinder; and   an adaptor plate spaced between the blind end cover and the cylinder end sheave body, the adaptor plate including internal bolt holes for bolting to the cylinder end sheave body, and external bolt holes for bolting the adaptor plate to the blind end cover.   
   
   
       2 . An upgraded riser tensioner as defined in  claim 1 , wherein the cylinder includes a rod extend port for receiving hydraulic fluid. 
   
   
       3 . An upgraded riser tensioner as defined in  claim 1 , further comprising:
 a packing gland for sealing between the cylinder and the rod.   
   
   
       4 . An upgraded riser tensioner as defined in  claim 1 , further comprising:
 at least one accumulator supported on the cylinder for transferring fluid to and receiving fluid from the cylinder.   
   
   
       5 . An upgraded riser tensioner as defined in  claim 1 , wherein the blind end cover fluidly closes a lower end of the hydraulic cylinder. 
   
   
       6 . An upgraded riser tensioner as defined in  claim 1 , wherein the adaptor plate includes circumferentially spaced radially inner holes for attaching the hydraulic cylinder to the cylinder end sheave body, and circumferentially spaced radially outer holes for attaching the adaptor plate to the blind end cover. 
   
   
       7 . An upgraded riser tensioner as defined in  claim 1 , wherein the upgraded hydraulic cylinder has a cross-sectional area of at least 25% greater than the circumferential area of a hydraulic cylinder prior to the upgrade. 
   
   
       8 . An upgraded riser tensioner as defined in  claim 1 , wherein a cable extends between the lower sheave assembly and the upper sheave assembly. 
   
   
       9 . An upgraded riser tensioner for an offshore vessel or platform, comprising:
 a cylinder end sheave body secured to the offshore platform, the cylinder end sheave body housing a lower sheave assembly;   a hydraulic cylinder extending upward from the cylinder end sheave body;   a rod extending upward from the hydraulic cylinder;   an upper sheave assembly supported on the rod;   a piston movable within the hydraulic cylinder and connected to the rod;   a blind end cover fluidly closing off a lower end of the hydraulic cylinder; and   an adaptor plate spaced between the blind end cover and the cylinder end sheave body, the adaptor plate including circumferentially spaced radially inner holes for attaching the hydraulic cylinder to the cylinder and sheave body, and circumferentially spaced radially outer holes for attaching the adaptor plate to the blind end cover.   
   
   
       10 . An upgraded riser tensioner as defined in  claim 9 , further comprising:
 at least one accumulator supported on the cylinder for transferring fluid to and receiving fluid from the cylinder.   
   
   
       11 . An upgraded riser tensioner as defined in  claim 9 , wherein the upgraded hydraulic cylinder has a cross-sectional area of at least 25% greater than the circumferential area of a hydraulic cylinder prior to the upgrade. 
   
   
       12 . An upgraded riser tensioner as defined in  claim 9 , wherein the cylinder includes a rod extend port for receiving hydraulic fluid. 
   
   
       13 . An upgraded riser tensioner as defined in  claim 9 , further comprising:
 a packing gland for sealing between the cylinder and the rod.   
   
   
       14 . A method of upgrading a riser tensioner for an offshore vessel or platform, the riser tensioner including a cylinder end sheave body secured to the offshore platform, the cylinder end sheave body housing a lower sheave assembly, a hydraulic cylinder extending upward from the cylinder end sheave body, a blind end cover spaced at a lower end of the hydraulic cylinder, a rod extending upward from the hydraulic cylinder, an upper sheave assembly supported on the rod, and a piston movable within the hydraulic cylinder and connected to the rod, the method comprising:
 spacing an adaptor plate between the blind end cover and the cylinder end sheave body, the adaptor plate including internal bolt holes and external bolt holes;   bolting the adaptor plate to the cylinder end sheave body using the internal bolt holes; and   bolting the adaptor plate to the blind end cover using the external bolt holes.   
   
   
       15 . A method as defined in  claim 14 , further comprising:
 providing a rod extend port in the cylinder for receiving hydraulic fluid.   
   
   
       16 . A method as defined in  claim 14 , further comprising:
 providing a packing gland for sealing between the cylinder and the rod.   
   
   
       17 . A method as defined in  claim 14 , further comprising:
 supporting at least one accumulator on the cylinder for transferring fluid to and receiving fluid from the cylinder.   
   
   
       18 . A method as defined in  claim 14 , wherein the blind end cover fluidly closes a lower end of the hydraulic cylinder. 
   
   
       19 . A method as defined in  claim 14 , further comprising:
 providing the adaptor plate to include circumferentially spaced radially inner holes for attaching the hydraulic cylinder to the cylinder and sheave body, and circumferentially spaced radially outer holes for attaching the adaptor plate to the blind end cover.   
   
   
       20 . A method as defined in  claim 14 , further comprising:
 extending a cable between the lower sheave assembly and the upper sheave assembly.