OA18401A - An anti-slip and self-centering device for an inner tube inside an outer tube of a unit-length subsea pipe element for the transport of fluids. - Google Patents

Abstract

The invention relates to an anti-slip and self-centering device for an inner tube within an outer tube of a unit length subsea pipe member for transporting fluids, comprising a ring (4) made of elastomeric material sandwiched between two annular metal plates (6, 8) of which an internal diameter corresponds substantially to the diameter of the internal tube and an external diameter corresponds substantially to the diameter of the external tube, the device further comprising means ( 10, 12) for clamping the plates together to compress the ring of elastomeric material.

Description

Anti-slip and self-centering device of an inner tube inside an outer tube of a unit length member of subsea pipe for the transport of fluids

Background of the invention

The present invention relates to the general field of underwater pipes resting on the seabed or providing the bottom-to-surface connection for the transfer of hydrocarbons, in particular oil and gas, coming from underwater production wells.

It relates more precisely to coaxial underwater conduits of the “Pipe In Pipe” or PIP type, that is to say “conduit in a conduit”, in which an internal tube transports the fluids and an external tube coaxial with the preceding one, Also called “external envelope”, is in contact with the ambient medium, that is to say with water. The annular space between the two tubes can be filled with an insulating material or else be emptied of any gas so as to provide thermal insulation for the fluids circulating in the internal duct. Such subsea coaxial pipes are particularly used in the context of installations at great depths where the water temperature is typically 4 ° C.

Generally, these coaxial conduits are assembled on land in units of unit length (one speaks of double, triple or quadruple joints, hereinafter indifferently referred to as "quad-joints" for quadruple sections of tube), of the order of 10 to 100m depending on the load bearing capacity of the laying system. These sets of pipes are then transported to sea on a laying vessel.

During installation, the quad-joints are connected to each other on board the vessel and as they are laid at sea. The installation can be carried out via a J-shaped laying tower positioned on the laying vessel. With the J-laying, the submarine pipe is typically lowered from the laying vessel practically vertical (between + 30 ° and -10 ° with respect to the vertical). The J-laying is a simple catenary laying in which the almost vertical inclination of the pipe decreases as it moves downwards until it follows the slope of the seabed.

This J-laying method requires moving each new quad-joint from a horizontal position (along the deck of the laying vessel) to a vertical position to line up with the J-laying tower. The quad-joint is kept vertical on the laying tower to allow its lower end to be welded to the upper end of the pipe. Once the quad-joint was welded to the pipe, the latter was lowered into the sea by moving the laying vessel forward by an advance corresponding to the length of the quad-joint.

Applied to coaxial pipes of the "PIP" type, the J-laying method involves vertically welding the quad-joint on the subsea pipe already in place. The new quad-joint is shown with an upward offset between the outer tube and the inner tube to allow the inner tube to be welded to that of the submarine pipe standby in the J-tower retainer , then to slide the outer tube of the quad-joint relative to the inner tube downwards in order to weld its lower end to the corresponding free end of the outer tube of the underwater pipe. The latter is then lowered into the sea and the operation is repeated with a new quad-joint.

In practice, such an installation method presents a certain number of problems. In particular, when lifting the new quadjoint, the inner tube must be kept in position to prevent it from sliding freely. Until now, specific complex devices were placed at the end to support this maintenance before being removed after welding the inner tube to the submarine pipe. However, the use of such devices proves costly in terms of installation time. In addition, when laying the inner tube of the quad-joint on the inner tube of the submarine pipe standing vertically in the J-tower, the inner tube, if free, tends to helically buckle in the outer tube of the submarine pipe, so that it is then generally necessary to adjust the upper part of the pipe to take up this play (the inner tube is cut as much as necessary). Finally, the sliding step of the outer tube relative to the inner tube risks tearing off certain parts positioned around the inner tube of the quad-joint (such as thermal insulation, heating cables, optical fibers, etc. the centering wedges, etc.).

Purpose and summary of the invention

The main object of the present invention is therefore to provide an anti-slip and self-centering device for an internal tube inside an external tube which does not have the aforementioned drawbacks.

According to the invention, this object is achieved by means of an anti-slip and self-centering device of an inner tube inside an outer tube of an element of unit length of sub-pipe. for transporting fluids, comprising a ring made of elastomeric material sandwiched between two annular metal plates, an internal diameter of which corresponds substantially to the diameter of the internal tube and an external diameter substantially corresponds to the diameter of the external tube, the device further comprising means for clamping the plates together in order to compress the ring of elastomeric material.

By compressing the ring of elastomeric material by clamping the plates together, the device according to the invention makes it possible in particular to ensure the concentricity of the tubes and the vertical retention of the inner tube inside the outer tube of the unit length element of pipe (or quad-joint). Indeed, the device is applied at a shoulder of the inner tube with the elastomer compression plates positioned on either side of this shoulder so that the plates are stopped by the shoulder. The device is thus completely fixed with respect to the inner tube, so that the sliding necessary for the assembly of the submarine pipe is forced and controlled and can only take place on the inner surface of the outer tube.

In addition, the clamping force is applied to the plates of the device in order to ensure a strong anti-slip stress between the inner and outer tubes. The characteristics of the device according to the invention and the clamping force are calibrated according to the weight of the internal tube so as to prevent any sliding of the internal tube under the effect of its own weight but to allow such a controlled sliding for values. greater than 15% to 50% of this weight (the load factor is defined during the design of the device according to the characteristics of the loading arms of the J-tower, the tubes making up the subsea pipeline and their accessories).

More precisely, the load factor of the device must be chosen to avoid inadvertent (i.e. uncontrolled) sliding of the inner tube with respect to the outer tube during its vertical positioning in the J-shaped tower (and thus guarantee the safety of operators). The load factor must also prevent the relative displacement of the two tubes when laying in the catenary part of the submarine pipe (maintaining a constant length between the tubes). The load factor should also prevent crushing or sagging of the subsea pipe annulus during variations in pipe length due to temperature variations.

Note that the sliding of the two tubes relative to each other when adding a quad-joint is a forced sliding and perfectly controlled by the intermediary of the loading arms of the J-shaped tower. Indeed, by being able to take the (vertical) weight of a quad-joint, these loading arms are able to apply vertical forces going down three or four times greater, in particular to force the alignment of the tubes and ensure welding without openwork the sections to be welded.

The device according to the invention also makes it possible to keep the inner tube concentric inside the outer tube of the element of unit length. The clearance between the inner tube and the outer tube thus remains constant throughout the assembly operation of the unit-length pipe element on the submarine pipe.

The device according to the invention finally makes it possible to ensure a locking in position of the parts, and in particular of the heating cables, optical fibers, etc. around the inner tube of the unit length pipe member. In this way, the device according to the invention makes it possible to avoid any tearing of these parts during the phase of sliding of the outer tube relative to the inner tube.

The tightening means may comprise a plurality of screws passing through the two plates and the ring made of elastomeric material and which are able to be tightened on nuts. In this case, these screws preferably each have a strength class of 12.9.

Preferably, at least one of the two plates is made from at least two angular sectors of plates. This feature has the advantage of facilitating assembly of the device around the shoulder of the inner tube.

Also preferably, the ring of the device is made of ethylene-propylene-diene monomer (EPDM) having a shore hardness of between 30 and 90, a Young's modulus of less than 1MPa and a Poisson's ratio close to 0.5. The plates of the device may for their part be made of steel.

The invention also relates to an element of unit length of submarine pipe for the transport of fluids, comprising an inner tube, an outer tube mounted around the inner tube while being coaxial with it, and at least one device as defined above. which is interposed between the inner tube and the outer tube and disposed around an annular shoulder of the inner tube.

Preferably, such a device is interposed between the inner tube and the outer tube at each longitudinal end of said element of unit length of submarine pipe.

Also preferably, each device is assembled around an annular shoulder of the inner tube positioned vis-à-vis the shoulder of the inner tube. In addition, each device advantageously ensures locking in position of at least one heating cable and / or at least one optical fiber.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting nature. In the figures:

- Figure 1 is a perspective and exploded view of the device according to one embodiment of the invention;

- Figure 2 is an assembled view of the device of Figure 1;

- Figures 3A and 3B are partial and sectional views of the device of Figures 1 and 2 in the uncompressed state and in the compressed state, respectively; and

- Figure 4 is a view of an element of unit length of submarine pipe type "PIP" equipped with devices according to the invention.

Detailed description of the invention

The invention applies to the laying of a submarine coaxial pipe of the "Pipe in Pipe" (or "PIP") type, that is to say a pipe which comprises an internal tube intended to transport hydrocarbons from production well and an external tube coaxial with the preceding one, also called “external envelope”, which is in direct contact with the surrounding water.

This type of subsea coaxial pipe is typically used in the offshore production of hydrocarbons at great depth. In the context of such installations, the subsea coaxial pipes can be assembled on land in several elements of unit length (one also speaks of “joints”, in particular of “double joints” for two unit elements assembled together, “triple joints”. "For three unitary elements assembled together," quadruple joints "for four unitary elements assembled together, or more generally" quad-joints "for quadruple sections of tube), of the order of 10 to 100 m depending on the capacity of holding of the installation system. During installation, these elements of unit length of submarine pipe are connected to each other on board the ship and as and when they are laid at sea.

The operation of connecting an element of unit length to the submarine pipe already lowered into the sea requires in particular to position the element of unit length of pipe vertically, to keep it in this position during welding of the end. from its inner tube to the upper end of the inner tube of the submarine pipe, then slide the outer tube to weld it to the upper end of the outer tube of the submarine pipe.

The object of the invention is an anti-slip and self-centering device making it possible, during this connection operation, to maintain vertical and fixed the internal tube of the element of unit length of pipe inside the tube. external, while ensuring its centering inside the external duct.

An example of such a device 2 is shown in perspective and exploded in Figures 1 and 2.

The device 2 comprises in particular a ring 4 of elastomeric material which is sandwiched between two annular metal plates 6, 8 (preferably of steel), the internal diameter of which corresponds substantially to the external diameter of the internal tube of the element of unit length. pipe on which the device is intended to be assembled, and whose external diameter D substantially corresponds to the internal diameter of the external tube of said element of unit length of pipe.

The device 2 further comprises means for clamping the plates 6, 8 together in order to compress the ring 4 of elastomeric material, the ring tending to “swell” radially both inwardly and outwardly. plates under the compressive force.

The clamping means can be produced by means of a plurality of screws 10 passing right through both the two plates 6, 8 and the ring 4 of elastomeric material and by clamping nuts 12. In the example illustrated in FIG. 1, the screws 10 are ten in number and are regularly spaced around an axis X-X of revolution of the device.

FIG. 3A represents the device of FIGS. 1 and 2 in the assembled position and “at rest”, that is to say without compressing the ring 4 of elastomeric material, while FIG. 3B represents the same device after application of a tightening force of the nuts 12 on the screws 10 causing compression of the ring 4, and thus a deformation of the latter visible by a radial “expansion” inward and outward.

When the device is interposed between an inner tube and an outer tube of an element of unit length of submarine pipe, this compression of the ring of the device thus makes it possible to ensure a locking in position of the inner tube to the inside the outer tube.

The elastomeric material used to make the ring of the device, as well as the characteristics of the screws / nuts and their tightening force, are chosen and calibrated according to the blocking needs of the inner tube of the unit length element of pipe under -marine inside the outer tube.

In particular, for the particular application envisaged (namely the vertical connection of an element of unit length of pipe on an underwater pipe), these choices and calibrations are defined so as to be able to support the weight of the internal tube but not beyond. In particular, the characteristics of the device must not prevent the sliding of the outer tube relative to the inner tube once the latter is connected to the inner tube of the submarine pipe.

Thus, the characteristics of the device according to the invention can be chosen and calibrated to enable it to absorb a compression load of between 1 MPa and 5 MPa (with an admissible compression load of 3.5 MPa, the device can support up to 4.7 tonnes at the inner tube and up to 5.8 tonnes at the outer tube of the unit length pipe element, these values being given for guidance only and depend on the diameters and dimensions of the contact surfaces).

For this purpose, one could for example choose as elastomeric material to make the ring of the device ethylene-propylenediene monomer (EPDM) having a shore hardness between 30 and 90, a dVoung modulus less than IMPa and a Poisson's ratio of l. 'order of 0.5. Thus, with such a Poisson's ratio, the vertical pressure on the plates exerted by the tightening of the screws is almost equal to the contact pressure on the side walls of the tubes.

With such characteristics, the screws 10 used for tightening the plates 6, 8 can each have a strength class of 12.9 so that their tightening allows the plates to be brought together in the order of approximately 0.5 mm.

FIG. 4 shows two devices 2 according to the invention assembled at each longitudinal end of an element of unit length of submarine pipe 14.

As previously described, the unit length pipe member 14 comprises an inner tube 16 disposed within an outer tube 18 by being coaxial thereto.

At each of its longitudinal ends, the internal tube 18 is provided with an annular shoulder 20 at the level of which is more precisely a device 2 according to the invention. This shoulder 20 is thin (so as not to prevent the controlled sliding of the outer tube) and can be obtained by adding a small length of inner tube integrating the shoulder at both ends (it protrudes radially towards the end). 'outside).

Preferably, the outer tube 18 also comprises, at its inner surface, an annular shoulder 20 'positioned vis-à-vis the shoulder 20 of the inner tube so as to reinforce the safety of the device (this shoulder 20' protrudes radially inward).

In the still horizontal position of the element of unitary length of pipe, the ring 4 of elastomeric material of the device is thus slid around the inner tube from one of its longitudinal ends in order to cover the corresponding shoulder 20.

The two annular plates 6, 8 are then positioned on either side of the ring 4, the plate located on the side opposite the end of the internal tube (here the plate 6) preferably being made from at least two angular sectors of plates 6a, 6b (see FIG. 1) so as to facilitate its assembly around the inner tube.

The screws 10 and nuts 12 are then mounted on the device (without exerting at this stage of tightening the nuts) with the screw heads advantageously turned towards the corresponding longitudinal end of the inner tube.

The outer tube 18 of the unit length pipe member is then slid longitudinally around the inner tube to its desired position. The screws 10 are then tightened in their nuts 12 so as to compress the ring 4 of elastomeric material. As indicated previously, this clamping force is calibrated according to the weight of the inner tube to allow the two devices to support the weight of the inner tube (with a safety margin of 15 to 20% more).

The annular space delimited between the two devices 2 can be filled with an insulating material, in particular with a resin. For this purpose, the devices according to the invention can advantageously serve as a stop wall or as a mold during the injection of the resin in order to maintain the latter in a fixed volume and which can be placed under vacuum.

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The unitary pipe length element 14 thus assembled can then be mounted vertically by means known per se to allow its assembly on the submarine pipe descended into the sea.

It will be noted that, advantageously, the device according to the invention can be used so as to ensure a locking in position around the internal tube of the element of unit length of conduct of various parts, such as heating cables, fibers. optics, etc.

To this end, these heating cables, optical fibers or others which extend longitudinally along the inner tube are inserted between the inner tube and the ring of elastomeric material of the device so that the compression of the latter ensures locking them in position.

Claims (9)

1. Element (14) of unit length of submarine pipe for the transport of fluids, comprising an inner tube (16), an outer tube (18) mounted around the inner tube while being coaxial with it, and at least one device. 'anti-slip and self-centering (2) which is interposed between the inner tube and the outer tube and arranged around an annular shoulder (20) of the inner tube, each anti-slip and self-centering device comprising a ring (4) of elastomeric material sandwiched between two annular metal plates (6, 8) of which an internal diameter (d) corresponds substantially to the diameter of the internal tube and an external diameter (D) corresponds approximately to the diameter of the external tube , and means (10,12) for clamping the plates together to compress the ring made of elastomeric material. 2. A unit length subsea pipe element according to claim 1, comprising an anti-slip and self-centering device which is interposed between the inner tube and the outer tube at each longitudinal end of said unit length pipe member. . 3. Subsea pipe unit length element according to one of claims 1 and 2, wherein the anti-slip and self-centering device is assembled around an annular shoulder (209 of the outer tube positioned facing the shoulder (20) of the inner tube. 4. Subsea pipe unit length element according to any one of claims 1 to 3, wherein the anti-slip and self-centering device locks in position at least one heating cable and / or at least one optical fiber. 5. Subsea pipe unit length element according to any one of claims 1 to 4, wherein the clamping means of the anti-slip and self-centering device comprise a plurality of screws (10) passing through. the two plates (6, 8) and the ring (4) made of elastomeric material and which are able to be tightened on nuts (12). A unit length subsea pipe member according to claim 5, wherein the screws (10) each have a strength class of 12.9. 7. Subsea pipe unit length element according to any one of claims 1 to 6, wherein at least one of the two plates (6) of the anti-slip and self-centering device is produced. from at least two angular sectors of plates (6a, 6b). 8. An element of unit length of submarine pipe according to any one of claims 1 to 7, wherein the ring (4) of the anti-slip and self-centering device is made of ethylenepropylene-diene monomer. having a shore hardness of between 30 and 90, a Young's modulus of less than lMPa and a Poisson's ratio of the order of 0.5. 9. A unit length subsea pipe element according to any one of claims 1 to 8, wherein the plates (6, 8) of the anti-slip and self-centering device are made of steel.