NO20101561A1 - Method and apparatus for sealing underwater pipes using a plug and sealant; welding unit for such apparatus - Google Patents

Abstract

The present application relates to a method for providing a tight joint between a first and a second subsea pipe (10, 12) having a first and a second pipe (16, 18), the method comprising at least the steps: (a) positioning a plug (22) in the first pipe (16) to plug the first pipe (10); (b) placing a sealant (26) over the first and second pipes (16, 18); (c) removing water around the first and second pipes (16, 18); (d) providing a welding unit (42) along the second tube (12) to at least the second tube (18); and (e) creating one or more welding seams internally around the first and second tubes (16, 18) to provide the tight joint between the first and second tubes (10, 12). The present application also relates to such an apparatus and a welding unit.

Description

METHOD AND APPARATUS FOR SEALING UNDERWATER PIPES USING A PLUG AND A SEALING AGENT; WELDING UNIT FOR SUCH APPARATUS

The present invention relates to a method and an apparatus for sealing underwater pipes, which e.g. submarine pipes, in particular for the repair of a broken submarine pipeline.

In the case of submarine pipelines for fluids such as e.g. oil, any damage to the pipeline that needs repair, for example caused by the environment or caused by collision with other equipment or corrosion or even bulging of the pipeline, where the pipeline is not too deep, can be brought to the surface and the repair operation carried out above the surface before the pipeline again placed under water, such as on the seabed.

Where such pipes or pipelines are located in deeper water, there are increasing difficulties. Divers can be used, but the depths at which they are allowed to work have been reduced over the years due to increasing safety concerns, and are in some places limited to 180 metres.

WO2006/004428 Al describes a remote-controlled splicing system for "dive-free welding". A pipe sleeve is placed around the two pipe ends, and then a welding clamp is placed around the pipelines to weld the pipe sleeve to the outside of the pipelines. The welding tool is integrated with the welding clamp to provide a very special piece of equipment that is able to integrate the clamp and the welding tool, and to position and operate them properly. For this reason, WO2006/004428 prefers that a remotely operated underwater vehicle (ROV) is still involved, with operator costs.

US 5,437,517 describes a method for automatically repairing an underwater pipeline, which involves one "simple working module" that is lowered to the seabed by a crane, and which performs various operations that require very special alignment, heavy equipment, and perfect alignment of the replacement pipe section for connection via locking flanges. It is known in the field that connection using locking flanges is less secure than welding.

One object of the present invention is to provide an improved method for joining two pipelines under water.

According to one aspect of the present invention, there is provided a method of providing a tight joint between a first and a second underwater pipe having first and second pipe ends, which method comprises at least the steps of: (a) placing a plug in the first touching to plug the first tube; (b) placing a sealant over the first and second touching ends; (c) removing water around the first and second stirrups; (d) providing a welding assembly along the second pipe to at least the second pipe end; and (e) creating one or more weld seams internally around the first and second tube ends to provide the tight joint between the first and second tubes.

By providing the welding assembly along the second pipe to reach at least the second touching and generally being in the vicinity of both the first and the second touching, the or each welding seam is created internally by the welding assembly, or at least provided internally, from within the tubes. This is in contrast to the traditional provision of external welding seams on underwater pipes.

The present invention is thus a method which can provide an internally welded, tight joint based on joining the two underwater pipes from the inside of the pipes.

The present invention can provide a tight joint between first and second underwater pipes capable of transporting any type of fluid, be it in gaseous form, liquid form or a combination thereof, including various hydrocarbons.

The present invention can be used at any water depth, such as underwater depth, whether this is within the safety range of a diver or not.

The plug to be placed in the first pipe end provides a plug in the first pipe during welding. Plugs such as isolation plugs (isolation pigs), isolation units or other devices are well known in the art. Removal of such plugs after welding is also well known in the field, where other known pipeline equipment such as clearance pigs is used.

The sealing means may comprise one or more elements or bodies which are provided separately or in one piece and are able to enclose the first and second touching ends so that water around the first and second touching ends can then be removed.

In one embodiment of the present invention, the sealing means comprises a sleeve, optionally including one or

several internal seals, which can be placed longitudinally above the first and second touching ends. The sleeve optionally includes one or more internal circumferential seals capable of forming at least a temporary, watertight seal between the sleeve and the pipe ends.

The sealant may include insulation around the socket to help reduce heat loss during the creation of the weld seam.

In another embodiment of the present invention, the sealing means includes one or more barriers/dams ("dams") or clamps, usually provided in two or more parts and capable of enclosing the first and second touching ends to allow removal of water around the first and the second touching. Barriers or dams such as cofferdams and clamps such as Dearman clamps are well known in the art.

The sealing means may include one or more induction coils capable of helping to prepare the pipes and/or pipe ends before welding.

The second pipe preferably extends above the surface of the water, for example above the sea surface. Such an extent may be due to the existing alignment or path for the second pipe, or a special step prior to the method according to the present invention.

In this way, atmospheric pressure and/or supply of one or more other gases can be provided along the second pipe from where it is located above the surface of the water, to the location of the first and second pipe ends. The welding can thus be provided at or near atmospheric pressure and/or in a desired gaseous atmosphere, which allows the method and operation of the welding to be relatively and technically simple compared to underwater welding at high water pressure.

The welding unit may comprise one or more of the group including: pipe cleaners, pipe end formers, cameras, lights, and pipe end aligners. The welding unit can be self-movable, or one or more pipe-inside devices, devices or units, such as tracked carriages, can be used to provide mobility to the welding unit. The welding unit's operation(s) may also be self-powered, or powered by the use of one or more umbilical cords, known in the art, along the second pipe.

Removal of water around the first and second touching ends is known in the art and usually involves the provision of one or more hoses, preferably in connection with the sealant, to dewater the area or vicinity around the first and second touching ends.

The welding unit can provide any type of weld seam, or combination thereof, such as butt welds, wedge welds, etc., thereby providing a tight joint between the first and second pipes from within near the pipe ends. The provision of welding seams between the pipe ends and/or one or more sleeves or the like, optionally as part of the sealant, is well known in the art and is not explained in more detail in this document.

According to a second aspect of the present invention, there is provided an apparatus which shall provide a tight joint between a first and a second underwater pipe having a first and a second connecting end, which apparatus comprises at least:

(a) a plug to be placed in the first pipe end to plug the first pipe; (b) a sealing means to seal over the first and the second touching; (c) one or more hoses to remove water around the first and second stirrups; (d) a welding assembly provided along the second pipe to at least the second pipe end and capable of internally forming one or more weld seams around the first and second pipe ends to provide the tight joint between the first and the second tube.

According to a third aspect of the present invention, there is provided a welding unit which is able to internally create one or more welding seams around the first and the second touching the first and the second underwater pipes to provide the tight joint between the first and the second pipe, where the welding unit can be provided along the second pipe.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, where: Fig. 1 is a schematic cross-sectional elevation of a first embodiment of the present invention; Fig. 2 is a schematic cross-sectional elevation of a second embodiment of the present invention; Fig. 3 is a side view of the welding unit shown in fig. 2; and

Fig. 4 is an elevation along line AA in fig. 3.

Reference is made to the drawings where fig. 1 shows a method for providing a tight joint between a first underwater pipe 10, such as an underwater pipe, and a second underwater pipe 12.

Fig. 1 shows a sea surface or a water surface 14 only as an illustration and without limitation in terms of the depth at which the first and second pipes 10, 12 are located and where it is intended to connect them to each other or splice them together again.

The nature and material of the first and second tubes 10, 12 are well known in the art and can vary depending on the type of fluid or fluids that are carried along them, and their properties and parameters. Common fluids are those based on one or more hydrocarbons, such as e.g. methane or heavier hydrocarbons such as oil.

The first and second tubes 10, 12 can have any size and/or dimensions. It is common, although the invention is not limited to this, that the inner and outer diameters of the first and second tubes 10, 12 are the same. This applies in particular where the method according to the present invention is used to repair an existing pipeline.

Existing subsea pipelines may need repair for a number of reasons, such as those described above. In such circumstances, the pipeline may require the removal of one or more sections, thereby forming a first pipe 10 having a first pipe end 16 and a second pipe 12 having a second pipe end 18.

It may be desirable to provide some preparation of the first and second pipes 10, 12 and in particular of the first and second pipe ends 16, 18 prior to the present embodiment of the present invention. This could include cleaning the first and second touching 16,

18 and/or removal of any coating (not shown) around the first and second pipes 10, 12, particularly around their first and second pipe ends 16, 18, to help provide the joint between them. Some pipes and pipelines have special coatings which may prevent the final provision of a tight joint between the first and second pipes 10, 12. Fig. 1 shows a plug 22, such as an insulation plug, which has been inserted into the first touching 16. The insertion can be carried out by one or more divers, or with a suitable underwater device. The plug 22 may include a circumferential seal 24 which is adapted to increase the engagement between the surface of the plug 22 and the inner circumference of the first pipe 10, thereby increasing the seal between them, particularly when the pressure differential across the plug 22 increases, as will be explained in bottom-up. Fig. 1 shows a first sealing means comprising a sleeve 26, optionally a sleeve tube, which has four internal circumferential seals 28. The sleeve 26 can be placed around the first and second tubes 16, 18 by one or more divers, or by a suitable underwater apparatus.

The sealant preferably includes enclosing thermal insulation, to reduce heat loss away from the subsequent welding operation. Heat insulation coating or coating 32 is well known in the art and is not explained further in this document.

Optionally, there may additionally be one or more further collars 34 placed between the first and second tubes 10, 12 and the sleeve 26, and optionally the thermal insulation 32, to increase the coupling of the same during subsequent processing.

Fig. 1 shows two hoses 35, 36 on opposite sides of the sleeve

26, which have valves and outlets 37, 38. The hoses 35, 36 are adapted to remove water around the first and second stirrups 16, 18 in a manner known in the art, such as using one or more vacuum pumps.

Fig. 1 also shows the second pipe 12 which extends above the water or sea surface 14 in such a way that atmospheric pressure can extend down through the second pipe 12 and be the prevailing pressure in the vicinity or the area around the first and second pipes 16, 18 The plug 22 ensures that the higher pressure of water or other fluid that may be found in the first pipe 10 does not affect the pressure around the first and second pipe ends 16, 18. Likewise, it allows the use of the seals 28 together with the sleeve 26, and the additional collars 34, the pressure in the area or the vicinity between the first and the second touching 16, 18 to be as desired.

If desired or necessary, one or more welding gases can be pumped down through the second pipe 12 to provide the right or desired welding atmosphere and/or pressure around the first and second pipes 16, 18.

Fig. 1 also shows a first welding unit 42 which can be provided along the second pipe 12, which e.g. from a place above sea level. The first welding unit 42 may include one or more peripheral wheels to assist its movement along the second pipe 12. Fig. 1 also shows a drive mechanism such as a first crawler 44 which is known in the art and which is capable of providing the first welding unit 42 movement. Fig. 1 also shows an umbilical cord 46 in the second pipe 12, which is able to supply the first welding unit 42 with power.

The front surface of the first welding unit 42 may include one or more units, devices, instruments or other equipment adapted to contribute to the preparation, cleaning, alignment etc. of the intended position or places to provide welding. In the embodiment shown in fig. 1, it is intended to provide fillet welds 60 between the first and second stirrups 16, 18 and the inner circumference of the sleeve 26 between them. In this respect, one or more instruments at the front of the first welding unit 42 can contribute to the final cleaning of such places.

The fillet welds 60 are thus provided internally in or within the first and second pipe ends 16, 18 and the sleeve 26. That is, not externally on the first and second pipes 10, 12 and the sleeve 26.

The first and second touching ends 16, 18 are preferably aligned and also preferably provided with a gap between them. The gap can be a suitable distance, such as in the range of 10-30 cm.

The first welding unit 42 includes an arm 52, preferably including one or more joints, at the end of which there is a welding point 54 which is able to create the above-mentioned wedge welds 60.

In this way, the embodiment of the present invention is shown in fig. 1 capable of providing internal welding between the first and second pipe ends 16, 18 (and thus necessarily between the first and second pipes 10, 12) and the sleeve 26 to form an internally welded tight joint between the first and the other pipes 10, 12.

Fig. 1 shows one embodiment of providing weld seams around the first and second pipe ends 16, 18. The present invention is not limited by the number or type or arrangement of welds around the first and second pipe ends 16, 18, whether they are to be welded together directly (as shown in Fig. 2 below) or be welded indirectly via one or more other pieces such as the sleeve 26.

When the welding is complete, the first track carriage 44 can withdraw the first welding unit 42 by reversing the operation for its installation, and the plug 22 can be removed by providing a clearing plug or the like, known in the art, along the first pipe 10 The pipeline formed by the joined first and second pipes 10, 12 is then ready to be used or reused.

The present invention thus provides a method for providing a tight joint between the first and second pipes 10, 12 using internal dry welding, the strength and reliability of which is known to be better than when wet welding externally around underwater pipes. Fig. 2 shows a second embodiment of the present invention which involves a first and a second pipe 10, 12. In a similar way to the embodiment shown in fig. 1, the first pipe 10 has been fitted with a plug 22 which is to provide a barrier against the penetration of fluid in the first pipe 10 towards the first pipe end 16 during the practice of the present invention. Fig. 2 shows the placement of two sets of clamps around the first and second pipe ends 16, 18, alternatively or additionally around the first and second pipes 10, 12, to form a second sealing means.

The first clamp or force set comprises one or more Dearman forceps 62 known in the art. Dearman fasteners 62 may be provided in two halves with a hinge to fit around the first and second stirrups 16, 18. Dearman fasteners 62 may be designed as a foam core composite for buoyancy. The Dearman clamps 62 would be installable by divers and/or suitable underwater equipment. Fig. 2 shows ceramic coated, hydraulically driven shoes 64 for the Dearman clamps 62 in a manner known in the art. Ceramic-backing strips can also be installed between the legs of the Dearman clamps and the pipe ends.

The Dearman forces 62 may also include one or more induction coils 66 which are designed to provide any desired preheating and/or drying of the first and second stirrups 16, 18.

One or more dams of all kinds can be placed around the Dearman forces 62 (dams). Fig. 2 shows two half-shell coffer dams 68 which are to isolate the working area around the Dearman forces 62 from the surrounding water 70. Fig. 2 shows two hoses 71, 72 on opposite sides of the coffer dams 68, which have valves and outlets 73, 74. The hoses 71, 72 are adapted to remove water around the first and second touching 16, 18 in a manner known in the art. The hoses 71, 72 can also optionally be used to supply one or more suitable fluids such as welding gases or auxiliary gases, preferably heated auxiliary gas, into the cofferdams 68 to contribute to the subsequent welding. Fig. 2 also shows a power umbilical cord 76 which is to supply power to one or more of the Dearman forces 62, the induction coils 66, etc. Fig. 2 shows the second pipe 12 which extends over a water or sea surface 78 in such a way that atmospheric pressure can extend down through the second pipe 12 and be the prevailing pressure in the vicinity or the area around the first and second pipe ends 16, 18. If desired or necessary, one or more welding gases or other gases can be pumped down through the second pipe 12 for thereby providing the right or desired welding atmosphere and/or pressure around the first and second touching 16, 18.

Fig. 2 shows a second welding unit 82 which can be provided along the second pipe 12, which e.g. from a place above sea level. The second welding unit 82 may include one or more circumferential wheels to assist its movement along the second pipe 12. The second welding unit 82 comprises two end units 84a, 84b with a joining tool section 86.

As shown in more detail in fig. 3 and 4, the joining tool section 86, which may be circular or of any other cross-section, includes one or more tools 88 which extend, e.g. at right angles, from it, which tools 88 can provide various operations and processes. One tool may be an internal pipe cleaner that is adapted to assist in physical cleaning of the first and/or second pipes 16, 18 or another portion of the first and second pipes 10, 12. Another tool may be a high pressure air supply for similar functions. Another tool may be a vacuum port capable of extracting material around the first and second stirrups 16, 18 to prevent any obstruction to the subsequent welding operation.

The present invention is not limited by the nature, number or function of the tools 88. Other tools include grinders, sanding discs, preheating equipment, metal wire cutters, nozzle cleaners, lights and a tool changer. The joining tool section 86 is optionally movable, such as rotatable, to allow each tool 88 to be accessible around the inner circumference of the first and second stirrups 16, 18.

The second welding unit 82 may also include one or more cameras 90 and lights 91 to facilitate visual inspection of the first and second touching 16, 18, and/or the subsequent welding.

The second welding unit 82 may be self-propelled or it may include a drive mechanism such as a second track carriage 92 which is known in the art and is capable of providing movement to the second welding unit 82. Fig. 2 also shows an umbilical cord 94 in the second pipe 12 for supplying power to the second welding unit 82.

In use and after placing and connecting the Dearman clamps 62 and the cofferdams 68, water around the first and the second pipes 16, 18 can be removed via the hoses 71, 72 followed by the introduction and displacement of the second welding unit 82 and the second track carriage 92 along the second pipe 12 to these is placed at the workplace near the first and second pipe ends 16, 18. Tools 88 in the joining tool section 86 can then be used to prepare the areas to be welded, optionally followed by any preheating and /or drying using the induction coils 66. Dried air and/or welding gas can then be pumped along the second tube 12 to provide the right atmosphere and/or the right pressure around the first and second tubes 16, 18, after which the second welding unit 82 provides butt welds (of which the first parts 96 are shown in Fig. 2) to join the first and second touching ends 16, 18 and thus provide a tight joint between the first and the second underwater pipe 10, 12.

In this way, the embodiment of the present invention is shown in fig. 2 able to provide internal welding or one or more internal welding seams between the first and the second touching 16, 18 at the desired atmosphere and pressure. As the welding takes place against mechanically driven shoes 64 and any counter-holding material between the shoes, the root opening for the welding production can typically be closed or up to 5 mm. Testing of the weld could also be performed by one or more tools 88 on the second welding unit 82 (and/or by one or more non-destructive testing methods from the outside of the first and second pipes 10, 12 after completion of welding and rigging of the equipment) .

Various modifications and variations in the described embodiments of the present invention will be obvious to experts in the field without going beyond the scope of the invention as stated in this document. Although the invention has been described in connection with the specific preferred embodiments, it is to be understood that the invention as stated in the claims shall not be unduly limited to such specific embodiments.

Claims (11)

1. Method for providing a tight joint between a first and a second underwater pipe having a first and a second pipe end, characterized in that it comprises at least the steps: (a) placing a plug in the first pipe end to plug the first tube; (b) placing a sealant over the first and second touching ends; (c) removing water around the first and second pipe ends; (d) providing a welding assembly along the second pipe to at least the second pipe end; and (e) creating one or more weld seams internally around the first and second tube ends to provide the tight joint between the first and second tubes. 2. Method as stated in claim 1, characterized in that the one or more welding seams are created at or near atmospheric pressure. 3. Method as stated in claim 1 or claim 2, characterized in that the sealing means comprises one or more sleeves or clamps or a combination of these. 4. Method as stated in any of the preceding claims, characterized in that the second pipe extends above the water surface. 5. Method as stated in claim 4, characterized in that the welding unit is provided along the second pipe from a level above the water. 6. Method as stated in one or more of the preceding claims, characterized in that the welding unit includes one/one or more from the group including: pipe cleaners, pipe end formers, cameras, lights; and pipe end aligners. 7. Method as stated in one or more of the preceding claims, characterized in that the sealing means includes a sleeve which is able to extend around the first and the second touching end, and the welding unit creates one or more wedge welds between the first and the other touching and the sealant. 8. Method according to one or more of claims 1 to 6, characterized in that the sealing means comprises two or more shell clamps, and the welding unit creates one or more butt welds between the first and the second touching end. 9. Method as stated in any of the preceding claims, characterized in that the welding unit is provided along the second pipe by a tracked vehicle. 10. Apparatus for providing a tight joint between a first and a second underwater pipe having a first and a second pipe end, characterized in that it comprises at least: (a) a plug to be placed in the first pipe end to plug the first tube; (b) a sealing means to seal over the first and the second touching; (c) one or more hoses for removing water around the first and second pipes; (d) a welding assembly provided along the second pipe to at least the second pipe end and capable of internally forming one or more weld seams around the first and second pipe ends to provide the tight joint between the first and second pipes . 11. Welding unit characterized in that it is able to internally create one or more welding seams around a first and a second pipe end of a first and a second underwater pipe to provide a tight joint between the first and the second pipe, the welding unit can be provided along the other pipes.