OA18911A - Procédé de raccordement de deux éléments unitaires de conduite de transport de fluides au moyen d'un manchon. - Google Patents

Abstract

L'invention concerne un procédé de raccordement de deux éléments unitaires (4, 4') d'une conduite de transport de fluides, chaque élément unitaire de conduite étant recouvert d'un revêtement isolant externe (6, 6') réalisé dans un matériau thermoplastique à l'exception d'une portion d'extrémité dépourvue de revêtement isolant externe, le procédé comprenant une étape de soudage des deux éléments unitaires de conduite mis bout à bout, une étape de positionnement d'un manchon annulaire (14) autour d'une zone de retrait du revêtement isolant externe et en partie autour du revêtement isolant externe des deux éléments unitaires de conduite, le manchon étant réalisé dans un matériau thermoplastique, une étape de fixation étanche par soudage du manchon sur le revêtement isolant externe, et une étape d'application d'une pression extérieure sur le manchon pour lui permettre de se déformer élastiquement et épouser la forme des portions d'extrémité respectives des deux éléments unitaires de conduite.

Description

Title of invention

Method of connecting two unitary elements for transporting fluids by means of a sleeve

Invention background

The present invention relates to the general field of fluid transport pipes, in particular submarine pipes, lying at the bottom of the sea or ensuring the bottom-surface connection for the transfer of hydrocarbons, for example oil and gas, from underwater production wells. It relates more particularly to the connection between two unitary elements of such pipes.

These underwater pipes generally include a steel alloy tube which is covered with an external insulating coating, typically a thermoplastic polymer, limiting the loss of heat to the ambient environment. The thickness of this external coating varies according to the operating conditions of the fluid to be transported (length of the pipe, temperature of the fluid, composition of the fluid, etc.).

Generally, these pipes are assembled on the ground in unit length elements (one speaks of double, triple or quadruple joints, hereinafter indifferently called “quad-joints” for quadruple sections of tube). These quad-joints are then transported to sea on a laying vessel.

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

The J and S laying techniques require connecting each new quad-joint to the submarine pipe on the laying ship before lowering it into the sea by moving the laying ship.

This step of connecting the new quad joint to the submarine pipe is carried out by welding end to end the free steel ends of the respective tubes of the new quad joint and the submarine pipe. The connection of the new quad-joint and the insulated submarine pipe 5 is made possible by a preliminary operation carried out after the factory coating of the quad-joints, this operation consisting in removing the insulating coating at the ends over a defined length allowing the installation of welding and non-destructive testing equipment.

Once these ends are welded together, it is necessary to cover the area of the pipe comprising the weld as well as the portions of the pipe tube for which the external insulating coating has been removed (this area hereinafter called " zone for removing the insulating coating ”(or“ cut-back ”in English) from a new insulating coating, ensuring that this covering is laid in a completely sealed manner with the rest of the external insulating coating of the pipe. For this purpose, the area of withdrawal of the insulating coating can be covered by several successive layers of different polymeric materials. For example, after the preparation of the bare steel surface by shot-blasting, a first relatively thin layer 20 will be applied, forming a corrosion protection primer directly applied to the coating removal area, a second thicker layer of a polymer-based adhesive on the adhesion primer, and a relatively thick third layer on the adhesive at least the thickness of the coating applied to the pipe. Alternatively, it is possible, after the deposition of an adhesion primer on the coating removal zone, to carry out an injection molding of insulating material.

This method of applying the outer insulating coating to the area of shrinkage of the coating is known as "Field Joint Coating", namely "pipe joint coating" in English. Reference may be made to document WO 2012/098528 which describes an example of such an application technique.

This “Field Joint Coating” technique however has a number of drawbacks. In particular, it requires a relatively long and therefore constraining production time (typically of the order of 20 to 30 minutes per operation). When it involves injection of material by molding, this technique presents a problem of adhesion of the molding on the zone of withdrawal of the insulating coating of the pipe, namely that the durability of the system is dependent on the success of the cohesion of the molded joint. on the existing coating. Finally, it is an application technique that offers little flexibility.

Subject and summary of the invention

The main object of the present invention is therefore to propose a connection method which does not have the aforementioned drawbacks of "Field Joint Coating".

According to the invention, this object is achieved by a method of connecting two unit elements of a fluid transport pipe, each unit pipe member being made of metal alloy and being covered with an external insulating coating produced in a thermoplastic material with the exception of an end portion devoid of an external insulating coating, the method comprising:

a step of welding the two unitary pipe elements placed end to end at their end portion devoid of external insulating coating so as to form an annular zone for withdrawal of the external insulating coating;

a step of positioning an annular sleeve around the area of withdrawal of the external insulating coating and partly around the external insulating coating of the two unitary pipe elements, the sleeve being made of a thermoplastic material; and a step of sealingly fixing by welding the sleeve to the external insulating coating of the two unitary pipe elements.

The method according to the invention is remarkable in that it uses a sleeve which is slid over the withdrawal zone of the external insulating coating to cover it and which is fixed by welding in a sealed manner on this coating. This sleeve, which is made of a thermoplastic material, makes it possible to guarantee a continuity of the coating at the level of the connection zone between the two unitary pipe elements, that is to say to guarantee sealing. In addition, the welding time of the sleeve can be very low, of the order of approximately 3 minutes, which represents a significant time saving compared to the technique of "Field Joint Coating" of the prior art. In addition, thanks to the use of welding, the fixing of the sleeve presents no adhesion problem on the unitary pipe elements. Finally, this process is applicable to any thermoplastic material used for the production of the external insulating coating and to all the dimensions of the unitary pipe element.

The method may further comprise, after the step of sealing the sleeve securely, a step of injecting an insulating material inside an annular cavity delimited inside by the zone of withdrawal of the external insulating coating. and outside by the sleeve. In the presence of a relatively large thickness of external insulating coating, for example of at least about 10 mm, this insulating material thus makes it possible to ensure thermal insulation of the individual pipe elements at their connection, and to transmit the pressure forces applied on the sleeve towards the unitary pipe elements (crushing forces under external pressure).

In this case, the insulating material is preferably hot when in the form of a gel or a liquid which is capable of solidifying inside the cavity while cooling.

The step of sealing the sleeve tightly on the external insulating coating of the two unitary pipe elements can be carried out by laser welding (technique known in English as “Laser Bonded Coating” for coating bonded by laser).

In this case, the material constituting the sleeve may be transparent or translucent at the wavelength of the laser in order to allow the laser to pass through the sleeve to the surfaces to be welded, the laser welding of the sleeve including the possible positioning. between surfaces in contact with the sleeve and the external insulating coating of the two unitary film-conducting elements made of material absorbing at the wavelength of the laser.

Alternatively, the step of sealing the sleeve tightly on the external insulating coating of the two unitary pipe elements can be carried out by electro-fusion welding (technique known in English as "Fusion Bonded Coating" for coating bonded by fusion).

In this case, the sleeve can comprise at least one electrical resistance at an internal surface which is, during the step of positioning the sleeve, brought into contact with the portions of the external insulating coating of the unitary pipe elements covered by said sleeve and which is connected to a source of electrical energy to cause a fusion on the surface of the material constituting the sleeve capable of ensuring a tight fixing of the sleeve on the external insulating coating of the individual pipe elements.

The step of positioning the sleeve may comprise sliding the sleeve along one of the two unitary pipe elements.

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 exemplary embodiments thereof without any limiting character. In the figures:

- Figure 1 to 5 show different steps of a method of connecting two unitary submarine pipe elements according to one embodiment of the invention;

- Figures 6A and 6B show an alternative embodiment of the sealed fixing of the sleeve by the laser welding technique; and

- Figure 7 shows another embodiment of the invention in which there is no injection of insulating material inside the withdrawal area of the outer insulating coating.

Detailed description of the invention

The invention applies to the connection of two unit elements of a pipe, in particular an underwater pipe, for transporting fluids such as hydrocarbons, for example oil and gas from underwater production wells.

One field of application of the invention is that of underwater pipes of the “Single Pipe” type (for single pipe), in contrast to coaxial pipes called PIPs (for “Pipe In Pipe”).

Figures 1 to 5 show an example of application of the invention to the connection of respective tubes 2, 2 'of two unit elements 4, 4' (hereinafter called "quad-joints") of such a submarine pipe.

In known manner, the respective tube 2, 2 ′ of these quad-joints is made of steel alloy and is covered with an external insulating coating, respectively 6, 6 ′, intended to limit the loss of heat to the ambient medium. Typically, this external insulating coating is made from a thermoplastic polymer, for example polypropylene, and can be formed from different layers, the constitution of which may vary according to the operating conditions. It is possible, for example, to use an external insulating coating composition formed from internal layers of foamed polypropylene or loaded with hollow glass microspheres (this is then called syntactic foam) and external layers of pure polypropylene.

During the laying of the underwater pipe at sea, the quadjoints are connected to each other on board the laying vessel and as and when they are laid at sea (the laying may be in J or S). These 15 laying techniques require connecting each new quad joint to the last assembled quad joint of the submarine pipe on the laying ship before lowering it into the sea by moving the laying ship.

To this end, as shown in FIG. 1, it is first necessary to remove the external insulating coating 6, 6 ′ on an end portion of the tubes 2, 2 ′ of the new quad-joint 4 to be assembled and of the last 4 'quad-joint assembled from the submarine pipe.

This step is for example carried out by means of different techniques of mechanical machining of the external insulating coatings 6, 6 ′. This cut can take several forms at the end 6a, 6'a respectively of the external insulating coverings 6, 6 '. Thus, as more particularly visible in FIG. 4, these ends 6a, 6'a can be cut in the form of a truncated cone. Alternatively, these ends could have other shapes, such as for example a straight shape, a staircase shape, etc.

The next step in the connection process consists in aligning the longitudinal axis 8 of the new quad-joint 4 to be assembled with the longitudinal axis 8 'of the last quad-joint 4' assembled of the submarine pipe and bringing these quad-joints together them to put the free end 35 of their respective tube 2, 2 'in contact with each other (Figure 2).

These steel tubes 2, 2 ′ are then welded together at their free end so as to form an annular weld bead 10 between the tubes. This welding can be carried out in one or more passes by any known welding technique, in particular passing through the outside or inside of the quad joints.

The tubes 2, 2 thus welded together, they form an annular zone 12 for withdrawal of the insulating coating (also called "cutback" in English) which is delimited longitudinally between the ends 6a, 6'a respective of the external insulating coatings 6, 6 '.

Once the tubes 2, 2 'are welded together, the connection method according to the invention provides for positioning an annular sleeve 14 around the withdrawal zone 12 of the external insulating coating, this sleeve 14 having an internal diameter slightly greater than the diameter outer quad-joints 4, 4 'covered with their outer insulating coating 6, 6' so that they can be slid along these and a length greater than the length of the zone of withdrawal of the outer insulating coating so as to come to cover partly the external insulating coating of the two unitary pipe elements.

Prior to positioning the sleeve 14, the annular surface of the withdrawal zone 12 of the insulating coating may have been treated, for example by carrying out a surface treatment consisting of shot blasting of the bare steel surface, followed by an application of '' a thin polymer coating, ensuring the functionality of an anticorrosion barrier, which can be applied either in liquid form by transfer using a contact tool or by spraying, or in powder form or even in '' a heat-shrinkable sleeve. For mechanical reasons specific to the installation and operating characteristics of the line, the weld bead could also be treated by carrying out a treatment to remove the slag from the welding operation (by grinding) in order to obtain a perfectly flat surface.

The sleeve 14 is made of a thermoplastic material which may be the same as the material used to produce the external insulating coating 6, 6 ′ of the quad joints.

Once the sleeve is positioned, it is tightly fixed on the external insulating coating according to a process described below.

This sealed fixing step can be carried out by electro-fusion welding (technique known as “Fusion Bonded Coating” - FIGS. 1 to 5) or by laser welding (technique known as “Laser Bonded Coating” - Figures 6A and 6B).

Electro-fusion welding consists in directly welding the sleeve 14 on the external insulating coating 6, 6 ′ using one or more electrical resistors 20 integrated in the sleeve as soon as it is manufactured, the sleeve being produced. in a thermoplastic material which is thermochemically compatible with the thermoplastic material of the outer insulating coatings of the quad joints.

Thus, as shown in FIGS. 3 to 5, the sleeve 14 integrates on its internal surface, and at each of its two longitudinal ends, an electrical resistance 20, this electrical resistance coming into contact with the portions of the external insulating coating 15 6, 6 'of the quad-joints covered by said sleeve.

During the actual welding step, these electrical resistors 20 are connected by pairs of connectors 22a, 22b to a source of electrical energy (not shown in the figures) to cause a fusion on the surface of the material constituting the sleeve. suitable for ensuring a tight fixing of the sleeve on the external insulating coating of the two quad-joint tubes. More precisely, the dissipation by Joule effect of the electric power supplied to the electrical resistors has the effect of causing a surface fusion of the material constituting the sleeve. The intimate mixture of the sleeve material and the material of the external insulating coatings of the tubes makes it possible to ensure perfect cohesion and sealing between the sleeve and these external insulating coatings.

As shown in FIGS. 6A and 6B, the step of sealing the sleeve securely can alternatively be carried out by laser welding.

To this end, as shown diagrammatically in FIG. 6A, the material constituting the sleeve 14 is transparent (or translucent) at the wavelength of the laser used for welding and films 24 of absorbent material are positioned at the wavelength 35 of the laser used at the end of the external insulating coatings 6, 6 ′ covered by the sleeve if the external insulating coating is less absorbent than the sleeve. In the case where the external insulating coating is made of a material which is more absorbent than that of the sleeve, such films are not necessary

In this way, during the step of sealing the sleeve tightly, a laser beam L is applied directed towards the absorbent material (the external insulating coating or the films 24 if necessary). The transparent constitution of the laser sleeve allows the laser beam to pass through it in the direction of its thickness to reach the absorbent material at the wavelength of the laser beam L (external insulating coating or film). This material being absorbent, the electromagnetic energy of the laser beam is converted into heat causing a fusion on the surface of the material of the sleeve. The intimate mixing of the material of the sleeve with the material constituting the external insulating coatings 6, 6 ′ (at their ends covered by the sleeve) thus makes it possible to ensure perfect cohesion and sealing between the sleeve and these external insulating coatings.

It will be noted that the laser beam L may be applied to the sleeve from the outside of the pipe, for example by means of a laser directed towards the surfaces to be welded and capable of pivoting around the longitudinal axis of the pipe.

Once the sleeve is tightly fixed on the external insulating coating, it delimits on the outside an annular cavity 16 which is delimited on the inside by the withdrawal zone 12 of the insulating coating.

In the embodiment of FIGS. 1 to 6, it is then planned to inject inside this cavity 16 an insulating material 18 which is hot when in the form of a liquid or a gel which is capable of solidifying inside the cavity when it cools. For example, the material could be polyurethane in solid or foamed form or a gel based on polyurethane and an organic compound such as kerosene for example.

To do this, the sleeve 14 is pierced with a first orifice 14a for injecting the insulating material 18 and with a second orifice 14b for ensuring that the cavity 16 is brought to ambient pressure (FIG. 5). Typically, an injection tool can be used which is positioned around the sleeve and allows the injection of the insulating material by applying during it a pressure on the sleeve to counter that dueο due to I injection (which will also have for advantage of facilitating welding).

These holes 14a, 14b may have been made during the manufacture of the sleeve and their location on the latter depends in particular on the position (vertical or horizontal) of the quad-joints 4, 4 'during their connection.

Once the insulating material 18 has been injected inside the cavity 16, the method provides for sealing the orifices 14a, 14b of the sleeve which have been used for this injection. This step can be carried out using patches or plugs (made of plastic for example) which are positioned in a sealed manner at the orifices 14a, 14b.

In connection with FIG. 7, another embodiment of the invention will now be described.

This embodiment applies more particularly to external insulating coatings which have a small thickness, for example less than 10 mm approximately. It also provides for positioning a sleeve 14 around the withdrawal zone 12 of the external insulating coating so as to partially cover the external insulating coating 6, 6 'at their end 6a, 6'a. Once positioned, the sleeve 14 is tightly fixed to this external insulating coating by electrofusion (using one or more electrical resistors 20 as shown in FIG. 7) or by laser welding (embodiment not shown ) as previously described.

Compared to the embodiment described above, taking into account the small thickness of the external insulating coatings, no injection of insulating material is provided inside the annular cavity 16 delimited between the sleeve 14 and the withdrawal zone of the external insulating coating.

The thickness of this cavity 16 being small, and the slope of the ends 6a, 6'a of the external insulating coatings 6, 6 'being advantageously soft, the sleeve 14 will, under the effect of the application of an external pressure between 1 and 2 bars, deform plastically and follow the shape of the quad-joints without risking tearing. The application of this external pressure is preferably exerted by means of a suitable tool before or during the step of tight fixing by welding of the sleeve, or after the step of tight fixing by welding of the sleeve by hydrostatic pressure. .

Claims (8)

1. Method for connecting two unit elements (4, 4 ') of a fluid transport pipe, each unit pipe element being made of metal alloy and being covered with an external insulating coating (6, 6 ⁷ ) made in a thermoplastic material with the exception of an end portion without an external insulating coating, the method comprising: a step of welding the two unitary pipe elements placed end to end at their end portion devoid of external insulating coating so as to form an annular zone of withdrawal (12) from the external insulating coating; a step of positioning an annular sleeve (14) around the withdrawal area of the external insulating coating and partly around the external insulating coating of the two unitary pipe elements, the sleeve being made of a thermoplastic material; a step of sealingly fixing by welding the sleeve to the external insulating coating of the two unitary pipe elements; and a step of applying external pressure to the sleeve to allow it to deform plastically and to conform to the shape of the respective end portions of the two unitary pipe elements. 2. Method according to claim 1, wherein the step of tightly fixing the sleeve (14) on the external insulating coating (6, 69 of the two unitary pipe elements is carried out by laser welding. 3. The method of claim 2, wherein the material of the sleeve is transparent or translucent at the wavelength of the laser to allow the laser to pass through the sleeve to the surfaces to be welded, laser welding of the sleeve. comprising the possible positioning between surfaces in contact with the sleeve and the external insulating coating of the two unitary film-conducting elements (24) made of material absorbing at the wavelength of the laser. 4. The method of claim 1, wherein the step of sealingly sealing the sleeve (14) on the outer insulating coating of the two unit pipe elements is carried out by electrofusion welding. 5. Method according to claim 4, in which the sleeve comprises at least one electrical resistance (20) at an internal surface which is, during the step of positioning the sleeve, brought into contact with the portions of the insulating coating. external of the unitary pipe elements covered by said sleeve and which is connected to a source of electrical energy to cause a fusion on the surface of the material constituting the sleeve capable of ensuring a tight fixing of the sleeve on the external insulating coating of the unitary pipe elements . 6. Method according to any one of claims 1 to 5, wherein the step of positioning the sleeve (14) comprises sliding the sleeve along one of the two unitary pipe elements. 7. Method according to any one of claims 1 to 6, in which the external pressure applied to the sleeve is between 1 and 2 bars. 8. Method according to any one of claims 1 to 7, in which the external pressure is applied to the sleeve before, during or after the step of tight fixing by welding of the sleeve.