US 4,787,778 A · Method and apparatus for tensioning a riser

Abstract

A tensioner system for a riser of a subsea production well. A plurality of at least three tensioners are each pivotally secured to both a lower surface of the production platform and to a tensioner ring that is itself secured to the riser. The tensioner ring may be generally octagonal with arms protruding from alternate faces of the octagon. These arms define the connecting points for the tensioners. The tensioners are angulated with respect to the axis of the riser, converging toward a single point lying on that axis and defining a first angle. The arms preferably form a second angle with respect to the body of the tensioner ring that is equal to said first angle so that the reaction surface defined by the bottom of the arms is perpendicular to the force lines along which the tensioners act. The failure of one of the tensioners will not result in unbalanced forces that could produce bending torsion, as occurred with previous designs.

Claims13

Dependent claims

A tensioner system for tensioning a riser from a producing subsea well and for compensating for relative movement between said riser and a production platform, said riser having a longitudinal axis, said apparatus comprising:

a plurality of at least three riser tensioners interconnected between said platform and said riser, each said tensioner comprising a piston cylinder arrangement with a rod-mounted piston slidably mounted therein;
a tensioner ring surrounding a portion of said riser and having a plurality of attachment points for connecting said tensioners at a first radial distance from said riser, said plurality of attachment points being equal in number to said plurality of tensioners;
means for securing said tensioner ring to said riser;
means for pivotally attaching an end of each of said tensioners to one of said attachment points;
means for pivotally attaching a second end of each of said tensioners to said platform at a point above said tensioner ring at a second radial distance greater than said first;
whereby said piston cylinders, with said piston rods in their median position, act along force lines which define a first angle with respect to said riser and which pass through a common point lying along the longitudinal axis of said riser such that failure of one of said tensioners will not result in torsional forces being applied to said riser by the tensioner system.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for tensioning a riser

Life of this patent

Method and apparatus for tensioning a riser

Life of this patent

Abstract

Claims13