TECHNICAL FIELD

The present invention concerns a method for joining a tubular member and a pipeline for conveying corrosive products.

BACKGROUND ART

In the petrochemical sector, corrosive products such as hydrocarbons, for example, with a high sulphide and/or carbon dioxide content, are known to be conveyed along metal pipelines. In addition to good mechanical properties, the pipelines for conveying corrosive products must guarantee high resistance to corrosion; for said purpose, they have a metal wall covered by an inner coating which is made of metal alloys designed to withstand the corrosive agents and which is joined to the wall by cladding or by lining. The pipelines clad or lined with the above-mentioned metal alloys are resistant to the aggressiveness of the corrosive products. However, the protection afforded by the cladding or lining is no longer guaranteed when one end of the pipeline is joined to a tubular member.

The joint between a tubular member and the end of a pipeline is dictated, for example, by the need to connect the pipeline to a flanged connector adapted to repair a damaged pipeline. A relatively simple method of joining a tubular member and a pipeline is described in the document EP 802,002 and comprises the steps of inserting the end of the pipeline comprising an inner face, an outer face, and a front face, adjacent to the inner and outer faces, inside an inner seat of the tubular member, inserting an expandable mandrel inside the end of the pipeline, and expanding the expandable mandrel to join the end of the pipeline and the connector.

The method described above is not able to preserve the protection guaranteed by the protective cladding/lining, even if the entire connector is made of corrosion-resistant material, because at least the front face of the pipeline is without the protective cladding/ lining and, in use, could be arranged in contact with the corrosive products. Furthermore, infiltrations of corrosive fluid could occur also along the portion of outer face adjacent to the front face.

DISCLOSURE OF INVENTION

One object of the present invention is to provide an efficient and inexpensive method for joining a tubular member to the end of a pipeline for conducting corrosive products.

According to the present invention, a method is provided for joining a tubular member and a pipeline for conducting corrosive products; the method comprising the steps of preparing a tubular member having an inner seat; inserting the end of a pipeline inside the inner seat of the tubular member; inserting a sleeve made of corrosion-resistant material inside the end of the pipeline; inserting an expandable mandrel inside the sleeve; and expanding the expandable mandrel to join the end of the pipeline and the tubular member, sealing the sleeve and the pipeline; and shielding parts of the pipeline sensitive to the corrosive products by means of the sleeve.

In this way, with one single operation it is possible to join the pipeline and the tubular member and shield the parts of the pipeline sensitive to the corrosive fluids. According to a preferred embodiment of the present invention, the sleeve is thinner than the pipeline.

In this way, the sleeve is subject to a plastic deformation greater than the plastic deformation of the pipeline and this allows sealing of the sleeve to the pipeline.

According to a preferred embodiment of the present invention, the pipeline is thinner than the tubular member.

In this way, the pipeline deforms against the tubular member to create a mechanical coupling.

Preferably, the mandrel is so expanded as to produce a plastic deformation at least of the end of the pipeline, and of the sleeve .

Preferably, the expansion of the expandable mandrel is located at least along an annular portion of the sleeve.

In practice, it is sufficient to plastically deform only some parts of the sleeve and the end of the pipeline.

Preferably, the pipeline has a wall having an inner face, a front face and an outer face, said inner seat comprising an indented axial profile.

The indented profile allows the end of the pipeline to grip the tubular member and create the mechanical joint.

Preferably, the tubular member comprises, inside the inner seat, an annular projection designed to contact the outer face of the pipeline, and at least one recess at the inner face to define the indented profile.

Preferably, the tubular member has, on the outside of the inner seat, a tubular face designed to align with the inner face of the pipeline.

The alignment between the tubular face and the inner face prevents the formation of steps between the tubular member and the pipeline and, therefore, avoids excessive deformations of the sleeve.

Preferably, the step of arranging the sleeve inside the pipeline comprises positioning a part of the sleeve at the tubular face and another part of the sleeve at the inner face and inner seat; and the step of expanding the expandable mandrel comprises deforming an annular area of the sleeve against the pipeline, and the pipeline against the tubular member inside the inner seat, and another annular area of the sleeve directly against the tubular member.

In this way the area at the front face of the pipeline is inaccessible to the corrosive products.

Preferably, the sleeve extends the whole length of the tubular face .

When the tubular member is not made of corrosion-resistant material, then it is necessary to provide protection of the tubular member along the tubular face.

According to a preferred embodiment of the present invention, the sleeve has a U-shaped turn-up designed to cover the inner face, the front face and the outer face of the pipeline, the turn-up being housed inside the inner seat between the pipeline and the tubular member.

According to said embodiment, the sleeve shields the sensitive parts of the pipeline and covers said sensitive parts. Preferably, the steps of inserting the sleeve and the expandable mandrel inside the pipeline comprise first fitting the sleeve around the expandable mandrel and inserting the sleeve together with the expandable mandrel inside the pipeline . This solution is very practical and reduces the work times.

Preferably, the expandable mandrel comprises a centre body and at least two sealing rings spaced apart along the centre body to define an expansion chamber between the centre body, the two sealing rings and the sleeve, the step of expanding the expandable mandrel being performed by pumping pressurized fluid inside the expansion chamber.

In practice, the expandable mandrel is an hydroforming mandrel provided with an expansion chamber.

Preferably, the expandable mandrel comprises four sealing rings to define at least two expansion chambers designed to receive pressurized fluid and spaced apart along the centre body .

In this way, it is possible to seal the sleeve in two distinct separate areas . A further object of the present invention is to produce a tubular assembly for conducting corrosive products.

According to the present invention, a tubular assembly is produced for conducting corrosive products, the tubular assembly comprising a pipeline, a tubular member and a sleeve, which is made of material resistant to corrosive products, and is configured to shield parts of the pipeline sensitive to corrosive products, and is fixed to the pipeline using the method claimed.

A further object of the present invention is to produce a kit for joining a tubular member and a pipeline for conducting corrosive products which is free from the drawbacks of the known art . According to the present invention, a kit is produced for joining a tubular member and a pipeline for conducting corrosive products; the kit comprising a sleeve made of corrosion-resistant material and designed to be arranged inside one end of the pipeline in turn inserted in an inner seat of a tubular member; and an expandable mandrel designed to be inserted inside the sleeve and expanded to join the end of the pipeline and the tubular member, seal the sleeve and the pipeline, and shield by means of the sleeve parts of the pipeline sensitive to corrosive products.

In particular, the expandable mandrel comprises a centre body and at least two sealing rings spaced apart along the centre body to define an expansion chamber between the centre body, the two sealing rings and the sleeve; the step of expanding the expandable mandrel being performed by pumping pressurised fluid inside the expansion chamber.

According to the present invention it is possible to define two separate sealing areas obtained by means of an expandable mandrel comprising four sealing rings to define at least two expansion chambers designed to receive pressurized fluid and spaced apart along the centre body.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will appear clear from the following description of the non-limiting embodiment examples thereof, with reference to the attached figures, in which:

- figures 1 to 3 are longitudinal section views, with parts removed for clarity, of respective steps of the method subject of the present invention; - figure 4 is a longitudinal section view, with parts removed for clarity and parts in section, of a tubular assembly obtained by the method subject of the present invention, some steps of which are illustrated in figures 1 to 3;

- figures 5 to 7 are longitudinal section views, with parts removed for clarity, of respective stages of the method according to an alternative embodiment of the present invention;

- figure 8 is a longitudinal section view, with parts removed for clarity, of a tubular assembly produced using the method subject of the present invention, some steps of which are illustrated in figures 1 to 3;

- figures 9 and 10 are longitudinal section views, with parts removed for clarity, of respective tubular assemblies produced using respective alternative methods of the present invention;

- figure 11 is a longitudinal section view, on an enlarged scale, and with parts removed for clarity, of a detail of a tubular assembly produced using the method subject of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to figure 1, the number 1 indicates overall an underwater pipeline designed to conduct liquids or gases, in particular hydrocarbons which are particularly corrosive because they are rich in hydrogen sulphides and carbon dioxide, and the number 2 indicates a tubular member which, in the case illustrated, is defined by a flanged connector and is arranged around one end of the pipeline 1. The pipeline 1 extends along an axis Al and has a tubular wall 3, which is defined as a whole by a supporting structure and by an inner coating applied to the supporting structure by cladding or lining. The supporting structure of the wall 3 is made of steel, while the coating is made of a metal alloy able to withstand the chemical attacks of the corrosive substances contained in the hydrocarbons. The wall 3 therefore has an inner face 4 resistant to the corrosive products, and a front face 5 and an outer face 6 which are not able to withstand the corrosive products. The tubular member 2 is inserted around the end of the pipeline 1, extends around the pipeline 1 and comprises a flange 7 designed to provide a bolted joint; and a tubular body 8, which has an inner seat 9 designed to house the end of the pipeline 1, and a tubular face 10 adjacent to the inner seat 9 and coplanar with the inner face 4 of the pipeline 1.

The inner seat 9 is arranged on the opposite side of the flange 7, has an indented profile and is defined by an indent with respect to the tubular face 10. In the inner seat 9 an annular projection 11 extends in a radial direction towards the axis Al . The annular projection 11 is arranged in a central position to define two annular recesses 12 and 13 arranged on opposite sides with respect to said annular projection 11.

The tubular element 2 is made of metallic material resistant to corrosion or at least has a coating suited to protect it from the aggressive chemical agents contained in the corrosive products .

The pipeline 1 or, better, the wall 3 of the pipeline 1 is thinner than the tubular element 2 or, better, than the tubular body 8 at the inner seat 9. With reference to figure 2, the number 14 indicates an expandable mandrel, and the number 15 indicates a sleeve fitted around the expandable mandrel 14.

The expandable mandrel 14 extends along a longitudinal axis A2 and comprises a frame 16 and two sealing rings 17. In the case in point, the frame 16 comprises a centre body 18, two end elements 19 and a gripping member 20. The sealing rings 17 are spaced apart along the centre body 18 and delimit together with the centre body 18 and the sleeve 15 an expansion chamber 21 designed to be filled with a pressurized fluid .

The sleeve 15 is made of a metal alloy resistant to corrosion and is thinner than the wall 3 of the pipeline 1 (figure 1) .

The sleeve 15 has a length such that its ends extend into the inner seat from one sealing ring 17 to the other sealing ring 17. With reference to figure 3, the expandable mandrel 14 and the sleeve 15 fitted on the expandable mandrel 14 are inserted inside the pipeline 1 and the tubular member 2.

The expandable mandrel 14 is inserted in the pipeline 1 and in the tubular member 2 so as to arrange a sealing ring 17 in the annular recess 13 and the other sealing ring 17 at the tubular face 10.

In practice, the sleeve 15 extends partly in the area of the tubular face 10 of the tubular member 2 and partly along the inner face 4 of the pipeline 1.

Once the expandable mandrel 14 and the sleeve 15 are correctly positioned, the expandable mandrel 14 and the sleeve 15 are locked in position by expansion of the sealing rings 17 so as to hermetically close the expansion chamber 21. Subsequently, a pressurized liquid is sent to the expansion chamber 21 at a pressure such as to deform at least the end of the pipeline 1 and the sleeve 15.

The deformation of the end of the pipeline 1 at the inner seat 9 produces a mechanical coupling with the tubular member 2 at the annular projection 11 and the annular recesses 12 and 13. In practice, the end of the pipeline deforms around the annular projection 11.

In other words, the end of the pipeline 1 plastically deforms and occupies wholly or partly the free space of the annular recesses 12 and 13 and hooks to the annular projection 11. The sleeve 15 is also subject to a plastic deformation and adapts to the shape of the end of the pipeline 1 and hermetically adheres to it.

In further detail, the deformation produced by the expandable mandrel 14 comprises partly a plastic deformation and partly an elastic deformation which comprises an elastic return. The elastic return of the end of the pipeline 1 is greater than the elastic return of the sleeve 15. Consequently, the sleeve 15 adheres intimately to the end of the pipeline 1.

Said operation which comprises cold plastic deformation of the metal parts is called cold forging. Although the present description refers to an expandable hydroforming mandrel 14, the present invention in its broadest form is not limited to the use of the expandable mandrel 14 but comprises the use of mandrels in which the plastic deformation is obtained directly with mechanical members.

Figure 4 illustrates a tubular assembly 22 obtained by the method described and comprising the pipeline 1, the tubular member 2, and the sleeve 15 joined to one another. The sleeve 15 has the function of shielding the area between the pipeline 1 and the tubular face 10 of the tubular member 2 so that the corrosive fluid cannot come into contact with the front face 5 and the outer face 6 of the pipeline 1. With reference to figures 5 to 7, an embodiment of the method subject of the invention is illustrated which is similar to the one described with reference to figures 1 to 3, and differs from the latter due to the fact that the tubular member 2 has a tubular face 10 particularly extended in the axial direction, a particularly long sleeve 15, and an expandable mandrel 14 adapted to define two expansion chambers 21 and, therefore, two separate deformation areas in an axial direction .

In figure 8, the tubular assembly 22 obtained with the method shown, at least partly, in figures 5 to 7 comprises two deformed areas in which the sleeve 15 has been hermetically sealed, on one side to the tubular member 2 and on the other side to the pipeline 1. According to said embodiment, the areas involved in the deformation are arranged on opposite sides with respect to the area in which the front face 5 of the pipeline 1 is arranged. In some cases, it is expedient to avoid an excessive plastic deformation at the front face 5 where an annular groove may be present which could be filled with the deformed material of the sleeve 15. The groove would allow an excessive flow of material inside the groove itself and would make the sleeve 15 excessively thin, thereby excessively reducing the thickness of the sleeve 15 in that area to the extent of jeopardising the corrosion protection.

With reference to figure 9, the tubular assembly 22 comprises a sleeve 115, which is provided with a turn-up 116 and is fitted on the end of the pipeline 1 to cover part of the inner face 4, the front face 5 and part of the outer face 6. The turn-up 116 is housed in the annular recess 12. The method for producing the tubular assembly 22 of figure 9 comprises fitting the sleeve 115 on the end of the pipeline 1, arranging the tubular member 2 around the end of the pipeline 1, inserting the expandable mandrel 14 inside the pipeline 1 and the tubular member 2, and deforming the area of the pipeline 1 and sleeve 115 at the annular projection 11 and at the annular recesses 12 and 13.

With reference to figure 10, the sleeve 15 is arranged solely at the inner wall 4 of the end of the pipeline 1 at the annular projection 11 and the annular recesses 12 and 13, and has the function of preventing excessive stretching and weakening of the coating of the wall 3. In this case, the front face 5 and the portion of outer face 6 housed in the annular recess 12 are protected by an anticorrosion alloy coating .

With reference to figure 11, a tubular assembly 22 is illustrated in which the tubular member 2 has a duct 23 which extends through the tubular body 8 and emerges along the tubular face 10, and in which a sleeve 15 has been cold forged to the tubular body 8 along the tubular face 10 and comprises an annular area 24 in which the sleeve 15 is arranged to contact the tubular portion 8, and two annular areas 25 and 26, which are arranged on opposite sides of the annular area 24 and are forged and sealed to the tubular portion 8. The duct 23 emerges at the area 24 and allows pressurized fluid to be pumped to test the seal of the joints in the annular areas 25 and 26.

Lastly, it is obvious that variations can be made to the present invention with respect to the embodiment described without departing from the scope of the following claims. The present invention can also be applied to carbon steel pipelines .