Anchor line tensioning method

Abstract

Method for mooring an offshore structure includes: providing a mooring line having one end connected to the sea bed and a connector at a free end; lifting the free end onto a deck of an anchor line handling vessel; connecting on the anchor line handling vessel a chain tensioner with a connection side to the connector; providing a working chain having a short tensioning part and a long installation part into the entry side of the chain tensioner; holding a free end of the installation part while lowering the chain tensioner below water level; picking up a free end of a pendant attached to the offshore structure, and attaching it to the free end of the installation part in an interconnect position on the anchor line handling vessel; placing the interconnect position overboard; connecting a lifting cable on the anchor line handling vessel to the tensioning part below water level; and exerting an upward tensioning force on the tensioning chain part.

1 . A chain tensioner, comprising:
 an elongate tensioner housing;   a connection side with a connector member and an entry side;   wherein the connection member is configured for connecting to a mooring chain section, and   wherein the entry side is configured for feeding a working chain to a tensioner housing,   a sheave; and   an opening in the tensioner housing for passage of a tensioning chain section of the working chain from the entry side through the tensioner housing along the sheave,   wherein the connection member and the entry side are positioned on a line along a longitudinal axis of the tensioner housing, the sheave is positioned on the tensioner housing in between the connection member and the entry side, and is aligned with the connection member and the entry side along said longitudinal axis, and   wherein a center of rotation of the sheave is positioned at a perpendicular distance from said line, with the perpendicular distance substantially equal to a radius of the sheave.   
     
     
         2 . The chain tensioner according to  claim 1 , wherein said line is a tangent of the sheave circumference. 
     
     
         3 . The chain tensioner according to  claim 1 , wherein the chain tensioner further comprises a chain stopper. 
     
     
         4 . The chain tensioner according to  claim 1  in combination with the the mooring chain section and the working chain,
 wherein the connection member is connected to the mooring chain section, and 
 wherein the tensioning chain section of the working chain passes through the opening in the tensioner housing from the entry side through the tensioner housing along the sheave. 
 
     
     
         5 . The chain tensioner according to  claim 4 , wherein said line is a tangent of the sheave circumference. 
     
     
         6 . The chain tensioner according to  claim 4 , wherein the chain tensioner further comprises a chain stopper. 
     
     
         7 . The chain tensioner according to  claim 5 , wherein the chain tensioner further comprises a chain stopper.