Method for protecting weld joints of concrete weight coated pipes

Abstract

The invention relates to the field of building and repairing pipelines having an external concrete coating, laid on the bottom of a body of water or in marshland. In a method for protecting weld joints of concrete weight coated pipes, a sleeve pre-impregnated with a compound is placed over a weld joint cleaned to bare metal and the regions proximate the seam on the two corresponding sections of pipe The edges of the end parts of the sleeve form smooth conical transitions from the sleeve to the end face of the concrete coating of the pipes, and the loose impregnated edges of the parts of the sleeve that are to be joined together are integrated into one another to form a seamless hollow cylinder around the pipe. The amount of curing agent in the sleeve impregnation compound is set so that the material of the sleeve polymerizes after the pipe has been laid on the bottom. By means of clamping couplings and a clamping assembly, the sleeve is hermetically pressed to the pipe to prevent electrolyte from getting under the sleeve and to protect the metal of the weld seam and the region proximate the seam against corrosion. The section of the pipeline containing the weld seam is thus also clamped, making it thicker and stronger, which increases the protection of the pipeline against external mechanical effects.

Description

[0001] METHOD OF PROTECTING WELDED JOINTS OF CONCRETE PIPES

[0002] DESCRIPTION

[0003] The invention relates to the field of construction and repair of pipelines with an external concrete coating, laid on the bottom of a reservoir or in swampy areas, and is aimed at protecting welded joints and weld-affected zones from corrosion damage, as well as from mechanical damage [F16L 57 / 00, F16L 58 / 00].

[0004] A WELDING PROTECTION SYSTEM is known from the prior art [WO9516160A1, published 15.06.1995], in which a pipeline includes several pipes, each of which has an anti-corrosion coating and a weight coating applied over the anti-corrosion coating, and the method includes applying as an annular wrap: a first tape element containing a flexible heat-resistant waterproofing substrate, such as a high-temperature PVC film, and a layer of pressure-sensitive adhesive having a width that covers and is adhered to a first length of the open pipe joint on both sides of the weld joint and at least partially overlaps and is adhered to a second length of the joint adjacent to the first length of the joint on both sides of the joint, covered with an anti-corrosion coating, but not a weight coating;and a second tape element comprising a wear-resistant film with a high melting point, such as a polyester film, having a width less than the width of the first tape element and laminated in the center of the outer surface of the first tape so that when applied it overlaps the first length of the joint of the open pipe and does not overlap the second length of the joint, and fills the volume of the joint; the first and second tape elements are conveniently represented as a pre-laminated tape with a pressure-sensitive adhesive layer protected by a release film or paper.

[0005] A disadvantage of this analogue is the use of only a ring-shaped wrapper as a protective coating, not reinforced by any other means, such as tightening sleeves, which can reduce the level of protection of welded joints and near-weld zones from corrosion and mechanical damage. Also known is a METHOD FOR APPLYING A POLYMER PROTECTIVE COATING TO INSULATED SURFACES OF WELDED JOINTS OF STEEL PIPELINES WITH A FACTORY POLYMER COATING IN THE FIELD [RU2130149, published 10.05.1999], which includes preheating the surface to be insulated, applying and forming a thermoplastic adhesive layer on it, followed by applying and forming at least one layer of polymer protective coating. Simultaneously with the preheating of the surface to be insulated, the adjacent factory polymer coating is heated.Preheating of the surface to be insulated is accomplished with infrared gas burners uniformly distributed over the entire surface, and the adjacent factory-applied polymer coating is preheated using the exhaust gases from these burners. Before applying the polymer protective coating, an intermediate layer of a material with high adhesive properties to both the thermoplastic adhesive layer and the polymer protective coating is applied and formed onto the thermoplastic adhesive layer. Each of these layers is formed by maintaining its material at a stable forming temperature until its structure is fully formed. Sevilen is used as the powdered adhesive, and a heat- and light-stabilized polymer is used as the polymer material. The layers are applied using flame spraying.

[0006] The disadvantage of the analogue is the formation of each of the protective layers by maintaining its material at a stable formation temperature for the entire time until its complete structuring, which, in the event of deformations caused by the descent of a welded section of the pipeline from a special vessel to the bottom, can cause the formation of new damage and, thus, can reduce the level of protection of welded joints and weld-affected zones.

[0007] The closest in technical essence is the METHOD OF FIRELESS REPAIR OF DEFECTIVE SECTIONS OF PIPELINES WITHOUT CHANGING PUMPING MODES [RU2788782, publ. 24.01.2023], during the implementation of which the surface of the section of the pipeline being repaired is prepared, dust is removed, moisture is removed, degreased with acetone, a rust converter is applied, which acts as a primer, the cavity of the defect is filled with a quick-hardening composite paste, a thin uniform layer of polymer adhesive is applied to the prepared area, while the inner composite sleeve is first glued, then on top of the inner composite sleeve, overlapping the horizontal joint of the inner sleeve, an outer composite sleeve is glued onto a thin uniform layer of adhesive, on top of which compression composite couplings are mounted, consisting of two half couplings connected to each other on one side by hinges, and on the other side by tie screws.The proposed method allows, without the use of welding or other fire processes, and without reducing the operating pressure in the pipeline, to repair non-through mechanical and corrosion defects of any length along the axis of the pipeline section being repaired, to stop defect formation, to strengthen the pipeline walls and to restore the load-bearing capacity to a defect-free level.

[0008] The main technical problem with the prototype is that the proposed repair method, when applied to welded joints of concrete-lined pipeline sections, allows for their protection from external mechanical damage, but is not capable of reliably protecting the pipe surface from corrosion. This is because it is impossible to ensure a completely hermetic seal between the edge of the elastically deformed composite sleeve and the edge of the concrete coating previously applied to the pipe during installation. This does not exclude the possibility of electrolyte, such as salty seawater, getting under the sleeve, leading to further development of the corrosion process and, thus, potentially reducing the level of protection of welded joints and weld-affected zones from corrosion and mechanical damage.

[0009] The objective of the invention is to eliminate the shortcomings of the prototype, namely, to provide reinforcement of the section with a welded joint in the zone between the concreted parts of the joined sections of the underwater pipeline, as well as reliable and durable protection of such sections from both mechanical damage, for example, from ship anchors, and from corrosion, designed for the entire service life of the pipeline.

[0010] The technical result of the invention is to enhance the protection of welded joints and heat-affected zones from corrosion and mechanical damage. This technical result is achieved through the use of the proposed method for protecting welded joints of concrete-lined pipes, in which a sleeve pre-impregnated with a compound is installed over a welded joint stripped to the metal and the heat-affected zones of two pipe sections so that the edges of the end parts of the sleeve form smooth conical transitions from the sleeve to the end of the concrete pipe shell, and the fluffed impregnated edges of the connecting parts of the sleeve are integrated into each other to form a seamless hollow cylinder around the pipe, while the amount of hardener in the compound impregnating the sleeve is set according to a preliminary calculation so that the sleeve material polymerizes after the pipe is placed on the bottom, then by means of at least three tightening sleeves,each of which consists of a pre-cured cylindrical shell made of composite laminate, and a clamping unit including a screw, preferably with an internal hexagon, a washer, two steel external clamping jaws, two steel internal clamping jaws and a nut, press the sleeve to the pipe, ensuring tightness due to its reliable gluing with absolute obturation, which prevents the ingress of electrolyte under the sleeve and protects the metal of the weld and the weld-affected zone from corrosion, crimp the section of the pipeline with the weld, making it thicker and stronger, which in turn increases the protection of the pipeline from external mechanical influences.

[0011] In particular, the bushing is made from a non-woven reinforcing mat made from polymer fibers.

[0012] In particular, the bushing is made from a non-woven reinforcing mat made of mineral fibers.

[0013] In particular, the bushing is made from a non-woven reinforcing mat made from a mixture of polymer and mineral fibers.

[0014] In particular, the width of the sleeve is 20-30 mm greater than the distance between the edges of the concrete shells of two adjacent sections of the pipeline.

[0015] In particular, the bushing is impregnated with an epoxy resin-based compound.

[0016] In particular, the bushing is impregnated with a compound based on polyester resin.

[0017] Specifically, the bushing is impregnated with a compound based on polyamide resin. Specifically, the bushing is impregnated with a compound based on polyurethane resin.

[0018] In particular, the bushing is impregnated with a compound based on silicone resin.

[0019] In particular, the shell of the turnbuckle is made of stainless metal.

[0020] In particular, the tension coupling is made with a tension unit made of parts made of composite materials.

[0021] Brief description of the drawings.

[0022] Fig. 1 shows a welded joint of two concrete-lined pipeline sections and a protective composite structure.

[0023] Fig. 2 shows section A-A from Fig. 1

[0024] The drawings indicate: 1 - pipeline; 2 - casing; 3 - sleeve; 4 - tightening coupling; 5 - welded joint; 6, 7 - conical transitions; 8 - screw; 9 - washer; 10 - outer pressure cheek; 11 - inner pressure cheek; 12 - nut; 13 - connecting seam. Implementation of the invention.

[0025] During construction or repair of pipeline 1 equipped with external protective concrete shell 2, a bushing 3 made of polymer non-woven mat impregnated with compound is installed on a vessel or on the edge over the welded joint 5 of two sections, the width of which is 20-30 mm greater than the distance L between the edges of concrete shells 2 of two adjacent sections of pipeline 1, wherein the edges of bushing 3 form smooth conical transitions 6 and 7 from bushing 3 to the end of concrete shell 2, thereby ensuring a tight fit of bushing 3 to the ends of concrete shell 2 and reliable sealing of the section of pipeline 1 with welded joint 5.

[0026] By means of the tightening couplings 4, tightened with the help of the tightening unit, including the screw 8 with the internal hexagon, the washer 9, two steel outer pressure jaws 10, two steel inner pressure jaws 11 and the nut 12, the sleeve 3 is tightly pressed to the pipe, and thus the ingress of moisture (electrolyte) under the sleeve 3 is excluded, creating a complete seal, which excludes the occurrence of the process of corrosion of the metal of both the weld seam 5 and the weld-affected zone. In addition, the tightening couplings 4, by compressing the sleeve 3, also compress the section of the pipeline with the weld seam 5, which allows the use of the protective composite structure according to the present description as a means for the permanent repair of pipelines. The connecting seam 13 of the sleeve 3 in Fig.1 and 2 are conventionally depicted by a dotted line, while it is actually absent, since the sleeve 3 is made of non-woven material, and the impregnated edges of the sleeve 3 are integrated into each other, leading to the merging of the seam 13 with the surface of the sleeve 3, after which the sleeve 3 forms a hollow cylinder, tightly glued to the surface of the section of the pipeline 1 with a welded joint, and reliably protects it from external physical influences.

[0027] The material of the sleeve 3 is made from polymer and / or mineral fibers, such as glass, basalt, a mixture of glass and basalt, carbon fiber, Kevlar, or from a mixture of the said materials, wherein the sleeve 3 is impregnated with a compound, in various embodiments, based on epoxy, polyester, polyamide, polyurethane, or silicone resin, immediately before winding around the section of the pipeline 1 stripped to metal with a welded joint 5.

[0028] Sleeve 3, thanks to the regulation of the amount of hardener in the compound used, polymerizes strictly after a calculated time after the pipe is placed on the bottom, that is, at the moment when the section of pipeline 1 with welded joint 5 will no longer be subject to deformation caused by the lowering of the welded pipeline from a special vessel to the bottom.

[0029] The proposed method for protecting welded joints of concrete-lined pipes is applicable both during construction and during repair work on underwater pipelines, which is currently of great relevance, in particular, in the development of hydrocarbon deposits on the offshore, oceanic shelf and swamps, particularly in Siberia.

[0030] The claimed technical result - strengthening the protection of welded joints and weld-affected zones from corrosion damage and mechanical damage - is achieved due to the fact that in the proposed method, in contrast to the prototype, for repair by strengthening sections of pipelines with a welded joint and their weld-affected zones, internal composite bushings elastically deformed to the diameter of the pipe are not used, but a non-woven reinforcing mat made of polymer and / or mineral fibers such as glass, basalt, a mixture of glass and basalt, carbon fiber, Kevlar or a mixture of the named materials is used, which, immediately before winding around the section of the pipeline stripped to the metal with a welded joint connecting two concreted sections of the pipeline, is impregnated with a compound based on epoxy, polyester, polyamide, polyurethane, or silicone resin, forming a composite bushing directly on the section with a welded joint,where it will be qualitatively imprinted on the inner surface of the bushing and will transfer the load through the composite bushing to the reinforcing shells without losses, and the said process will occur only after the bushing has polymerized strictly after a calculated time, which is ensured by the polymerization rate, regulated by the amount of hardener in the compound used, and, according to the claimed invention, is set in such a way that polymerization will occur after the pipe has taken its design position on the bottom, that is, when the section of pipe with the welded joint will no longer be subject to deformation caused by the lowering of the welded pipeline from a special vessel to the bottom.

Claims

FORMULA 1. A method for protecting welded joints of concrete-lined pipes, in which a sleeve, pre-impregnated with a compound, is installed over a welded joint cleaned to the metal and the weld-affected zones of two pipe sections so that the edges of the end parts of the sleeve form smooth conical transitions from the sleeve to the end of the concrete shell of the pipes, and the fluffed edges of the connecting parts of the sleeve, impregnated with a compound, are integrated into each other to form a seamless hollow cylinder around the pipe, while the amount of hardener in the compound impregnating the sleeve is set according to a preliminary calculation so that the material of the sleeve polymerizes after the pipe is placed on the bottom, then by means of at least three tightening couplings, each of which consists of a shell made of composite laminate pre-cured on a cylindrical form, and a tightening unit including a screw, preferably with an internal hexagon, a washer, two steel outer clamping jaws,Two steel internal clamping jaws and a nut press the sleeve to the pipe, ensuring a tight seal due to its reliable adhesion with absolute obturation, which prevents electrolyte from getting under the sleeve and protects the weld metal and the weld-affected zone from corrosion, compressing the section of the pipeline with the weld, making it thicker and stronger, which in turn increases the protection of the pipeline from external mechanical influences.

2. The method according to paragraph 1, characterized in that the bushing is made from a non-woven reinforcing mat made from polymer fibers.

3. The method according to paragraph 1, characterized in that the bushing is made from a non-woven reinforcing mat made from mineral fibers.

4. The method according to paragraph 1, characterized in that the bushing is made from a non-woven reinforcing mat made from a mixture of polymer and mineral fibers.

5. The method according to paragraph 1, characterized in that the width of the sleeve is 20-30 mm greater than the distance between the edges of the concrete shells of two adjacent sections of the pipeline.

6. The method according to paragraph 1, characterized in that the bushing is impregnated with a compound based on epoxy resin.

7. The method according to paragraph 1, characterized in that the bushing is impregnated with a compound based on polyester resin.

8. The method according to paragraph 1, characterized in that the bushing is impregnated with a compound based on polyamide resin.

9. The method according to paragraph 1, characterized in that the bushing is impregnated with a compound based on polyurethane resin.

10. The method according to paragraph 1, characterized in that the bushing is impregnated with a compound based on silicone resin.

11. The method according to paragraph 1, characterized in that the shell of the tightening coupling is made of stainless metal.

12. The method according to paragraph 1, characterized in that the tightening coupling is made with a tightening unit from parts made from composite materials.

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