Patent FR-2858648-A1 (FR)
Title: Device for making a sealed flexible connection to the surface for an underwater pipe or riser carrying a float using revolving pieces on the ends of the riser and a union with a spherical seating
Inventor: STASSEN YVES
IPC: E21B17/01
Filed: 2003-08-08
Abstract: A first forged revolving piece (22) is fixed to the top of the lower part (1a) of the riser and a second forged revolving piece (24) is fixed to the bottom of the upper part (1b) of the riser. A union (23) is fixed in a sealed and reversible manner to the second piece and connected to the first piece by a laminated revolving seating (30) of conical or preferably spherical shape : The junction device (8) is placed between and fixed to a lower part of the riser descending to the seabed and an upper part of riser passing through the float (2) and rising to the surface. Each forged revolving piece has an internal pipe section of the same diameter as the part of the riser it is attached to. A revolving union (23) is fixed in a sealed and reversible manner to the second forged piece and is connected to the first forged piece by a laminated revolving seating (30) of conical or spherical shape. An independent claim is made for a linkage for a riser tensioned by a float comprising a cylindrical enclosing drum (20) coaxial around the top of the immersed pipe, which has a junction device as described above. The first forged piece has an external convex revolving surface at its top centred on a point O on the ZZ' axis of the riser and the second forged piece is welded to the upper part of the riser. The union has a first internal concave revolving surface, preferably spherical, centred on the same point O. A first laminated revolving seating which is also preferably spherical, centred on the same point O, is made of a number of layers of elastomer sandwiched between leaves of rigid reinforcement material, in particular steel. These stick to the concave and convex surfaces to ensure a sealed and elastic linkage between the union and the first piece. A toroidal joint (28) forms a seal between the upper revolving surface and the lower surface of the second piece, which are bolted together. The external envelope of the float is fixed to an upper revolving surface on the second piece or to an upper revolving surface of a second union whose lower revolving surface is itself bolted to the upper surface of the first union with a toroidal joint. The second piece has a second convex external surface which is preferably spherical centred on the same point O as the other spherical surfaces. A second laminated seating connects the second convex revolving surface to a second internal concave surface on the top of the second forged piece. The first and second pieces and the union define a first internal chamber in which the pressure is controlled. A second internal pipe of greater diameter than the riser, preferably a reinforced pipe of greater thickness than the riser, is fixed to the external envelope of the float by a second revolving union to which the bottom of the float's external envelope and the bottom of the second pipe are welded. A second chamber is defined by the internal revolving surface of this second union, the upper surface of the second piece, the cylindrical external surface of the second pipe and a closing connection at the top end of the second internal pipe and riser. The pressure in the second chamber is also controlled. The float extends over a length of 40 to 100m to confer sufficient floatation to tension the seabed-surface connection and is made of cylindrical caissons individually sealed and mechanically fixed together in the longitudinal ZZ' direction. Means of stabilization are placed in the bottom of the float which effectively increase the amount of water moved with it or lowering the centre of gravity of the upper part of the pipe at the level of the float.