RU2602715C1 - Connection of pipes with internal coating and method of its implementation - Google Patents

Abstract

FIELD: production of fittings.

SUBSTANCE: invention relates to pipeline valves and can be used in construction of pipelines for transportation of liquid aggressive media, particularly for oil pumping, gas-condensate mixture, etc. Welded joint of pipes with internal heat-sensitive coating includes two pipes, connecting enameled bushing, wherein ring branch pipes corresponding to brand chemical composition and dimensional values of connected pipes are welded between connected pipes ends and connecting bushing to pipes ends. Branch pipes inner surface in bushing length section (3.1-3.5) has high temperature silicate enamel coating of bushing enamel composition. On side of non-enamelled section branch pipes are welded to pipes ends using circular seam, “branch pipe-pipe-branch pipe” weld joint is subjected to inner surface mechanical cleaning and subsequent application of heat-sensitive coating onto this surface with partial overlapping of branches enamelled section. Connection of pipes into string is performed by means of connection enameled bushing welding with annular branch pipes without fusion of inner heat-sensitive layer.

EFFECT: connection of pipes with internal heat-sensitive coating and method of its implementation provides simple and reliable welded joint and joint inner surface anticorrosion protection against effects of pumped aggressive fluids.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to the construction of pipeline transport and is used in the assembly of pipelines intended for the transportation of corrosive media in the oil, gas, chemical, mining, energy and other industries. For these purposes, pipes with an internal anti-corrosion heat-sensitive (polymer, paint) or heat-resistant (silicate-enamel, ceramic) coating are widely used. However, a significant problem is the choice of the method of connecting such pipes into pipeline systems due to the problems of ensuring internal protection of the welded joint zone taking into account the technical and economic requirements for their operation.

A known method of manufacturing pipelines from enameled pipes [Ed. USSR certificate 1268348, bull. No. 41, publ. November 7, 1986], according to which, after applying paste from a slip of the same enamel that is coated on the inside of the pipe, welding is performed with belts at a distance of 5-10 mm from the ends, then this section is heated until the belts of the enamel paste, which should cover the ring, are softened weld. However, the molten enamel paste in the upper part of the annular seam does not spread on the sides, but flows down. As a result, the upper part of the weld is without enamel, which negatively affects the corrosion resistance of the weld.

A known method of connecting metal pipes with an internal anti-corrosion coating [RF Patent 2154221, Bull. No. 22, publ. 08/10/2000]. For connection, bushings made of corrosion-resistant metal are used. The bushings on the inner surface of the pipe ends are pre-fixed by radially crimping the pipe ends, and finally by reducing the pipe ends to the length of the bushings. After applying an anticorrosive layer to the inner surface of the pipes and preparing the edges, the pipes are joined using the well-known technology of welding two-layer metals. However, upon contact of dissimilar metals, there is a danger of electrochemical corrosion, which requires additional protective measures.

Known pipe with an inner coating and method of its manufacture [RF Patent 2105921, Bull. No. 6, publ. February 27, 1998]. A layer of a self-fluxing alloy is applied to the end sections of the inner surface of the pipe, melted by heating, an additional layer of a self-fluxing alloy is applied to a limited length of the melted layer, and a heat-sensitive coating is applied to the inner surface with a partial coating of the melted layer. Nickel-aluminum, chromium-nickel, stainless alloys, and ceramic coatings are used as a self-fluxing heat-resistant coating. The protective coating of the weld is formed when welding pipes into a whip due to the fact that the melt of the self-fluxing alloy spreads over the surface of the root of the weld with an additional layer of glassy slag formed. However, there is also no guarantee of protection of the upper zone of the weld due to dripping of the melt.

In general, the well-known methods for protecting welded joints of pipes with an internal coating against corrosion, with certain advantages, have common disadvantages: the difficulty of welding by field welding, in particular by the technology of welding two-layer materials, the use of scarce connecting materials and heating equipment, significant technical and economic costs, lack of guaranteed protection of the inner surface of the pipe in the zone of thermal heating during the formation of the weld.

The closest in technical essence and the achieved result is the known connection of enameled pipes and the method of its implementation [RF Patent 2227241, Bull. No. 11, publ. April 20, 2004].

To connect the pipes with an internal enamel coating, a sleeve with a radial projection enameled with a vintage enamel composition of pipes along the entire perimeter of the middle section and with a cut along its length is used. The dimensions of the sleeve are related to the thickness of the pipe wall. The width (I) and height (h) of the radial protrusion, as well as the length (L) of the sleeve and the thickness (t) of its wall, refer to the thickness (S) of the wall of the connected pipes, respectively: 1 / S = (0.1-0.3) , h / S = (0.3-0.6), L / S = (2-5) and t / S = (0.12-0.35).

The practice of operating pipeline systems using enamelled sleeves for connecting enameled pipes has confirmed the long-term reliable corrosion protection of the welded joint. At the same time, the use of an enamelled sleeve for welding pipes with a heat-sensitive coating, for example polymer, does not ensure continuity of the inner coating of the pipes in the heat affected zone of the welded process due to burnout and fusion of the heat-sensitive coating.

In the present application for the invention, the task is set using the basic principles of functional mutual arrangement and interaction of structural elements of a known pipe joint [RF Patent 2227241, Bull. No. 11, publ. 04/20/2004], to develop a reliable design for connecting pipes with an internal heat-sensitive coating, providing internal protection of the welded joint while maintaining the integrity of the heat-sensitive coating, eliminate the noted drawbacks of analogues and achieve higher economic, technical and operational characteristics of welded pipeline systems designed for the transportation of aggressive wednesday

The essence of the invention and the task are solved in that in a welded joint containing two pipes, a connecting enameled sleeve with a cut along its length and a radial protrusion, made along the perimeter of its middle section, the width (I) and height (h) of the radial protrusion as well as the length (L) of the sleeve and the thickness (t) of its wall are related to the thickness (S) of the wall of the connected pipes, respectively, as I / S = (0.1-0.3), h / S = (0.3-0, 6), L / S = (2-5), t / S = (0.12-0.35), placed between the inner surface of the ends of the pipes to be connected and the outer surface of the sleeve oplavkoe anticorrosion coating in the inventive connection between the ends of the pipe with internal thermosensitive coating and a connecting sleeve welded enamelled annular nozzles corresponding branded chemical composition and dimensional values of the pipe, wherein each pipe length (L _rds) is not less than 4.0 connecting length enameled sleeve (L _W ), and its inner surface has a high-temperature silicate-enamel coating of the vintage enamel composition of the connecting sleeve on a section of a pipe with a length of (3.1-3.5) L _W from its end from the side of the connecting root suture with an enamelled sleeve, the heat-sensitive coating being a continuous continuous layer on the inner surface of the pipe and pipes connected to it by welding with partial overlapping of the surface of silicate-enamel pipe cover by the amount of (0.1-0.5) L _W

A causal relationship between the ratio of the parameters of the connecting enamelled sleeve and the quantitative parameters of the claimed welded joint of pipes with an internal heat-sensitive coating, taking into account the use of enameled annular pipes in the welded joint, is determined by the need to protect both silicate and heat-sensitive coatings in the heat affected zone of the weld and is consistent with the data obtained when creating technical solutions [RF Patent 2227241, Bull. No. 11, publ. 04/20/2004, Utility Model No. 123891], as well as many years of successful experience in the industrial use of connecting sleeves in pipeline systems.

In FIG. a longitudinal section shows a general view of the connection of pipes with an internal heat-sensitive coating in working condition.

The connection consists of two pipes 1, 2 with an internal heat-sensitive coating 3, two nozzles 4, 5 with an internal silicate-enamel coating 6, a branded coating composition of the sleeve 7, connected by a root welding seam 8 with nozzles 4, 5, which are joined to the opposite side pipes 1, 2 by a weld seam 9, 10. On the length of the nozzles equal to the length of the sleeve, an anti-corrosion coating 11 is formed from an enamel composition, including enamel coatings of the pipes, sleeve and silicate low-melting enamel.

In FIG. in addition, L _pat is the length of the nozzles, L _W is the length of the sleeve, S is the thickness of the pipes to be connected, S _pat is the thickness of the walls of the nozzles, L _ep is the length of the enameled portion of the inner surface of the nozzles, L _per is the overlap length of the enamel coating of the nozzle with a heat-sensitive layer.

From sources of information [Auth. USSR certificate 1648696, bull. No. 18, publ. 05/15/1991] it is known the use of annular nozzles of corrosion-resistant elements, welded to the pipes with a special filler material. Before applying a protective coating, a welded joint with corrosion-resistant elements is subjected to heat treatment, a coating is applied, and then the pipes are welded together along corrosion-resistant elements.

In the known method of connecting metal pipes with an internal anti-corrosion coating [RF Patent 2154221, Bull. No. 22, publ. 08/10/2000] use bushings made of corrosion-resistant steel, fixed by radial compression and reduction of pipe ends to the length of the bushings. After preparing the edges of the bushings for welding, the pipe connection is carried out according to the known technology of welding two-layer metals.

However, it is known that welded joints made of steels with various electrochemical properties, for example, “carbon steel - stainless steel” are subject to severe contact corrosion, which negatively affects the operational reliability of pipelines.

According to the method [RF Patent 2105921, Bull. No. 6, publ. 02.27.1998] before applying the internal heat-sensitive coating to the pipe, heat-resistant layers of thermally or chemically treated and untreated self-fluxing alloy (nickel-aluminum, stainless alloys, enamels, ceramic materials) are applied to the pipe ends. Welding of the end sections of the pipe in the manufacture of the pipeline is carried out in one step.

A disadvantage of the known pipe joining methods is the technical complexity of implementation, the use of expensive materials, including self-fluxing alloys, the laboriousness of pipe assembly in the field, and the tendency to contact corrosion of welded joints of dissimilar metals during pipeline operation.

The closest in technical essence and the achievement of the task is a method of connecting enameled pipes [RF Patent 2227241, Bull. No. 11, publ. April 20, 2004], performed on enameled metal elements. An enameled connecting sleeve interconnected by dimensional values with the wall thickness of the pipe is placed inside the ends of the pipes and, when the root seam is formed, the anticorrosion coating is formed in the form of an enamel composition along the length of the connection over the entire length of the sleeve along the entire surface of the sleeve by fusing the initial enamel coating and slip with silicate low-melting enamel. contact with the ends of the welded pipes.

The application for the invention proposed a new method for connecting pipes, providing high technical, economic and operational characteristics of the welded joint (see Fig.), For the construction of pipeline systems for various purposes, including pipes with an internal heat-sensitive coating (polymer compositions, paints and others materials). The method includes preparing the connection elements for assembly, selection and formation of protective coatings of the connection elements, their welding, taking into account the claimed relationship of the connection elements and their size ratios.

Silicate-enamel coating 6, corresponding to the coating composition of the connecting sleeve 7, is deposited on the inner surface of the nozzles 4, 5 of the steel grade and size of the connected pipes in a section of length (3.1-3.5) L _W. Then, from the side of the non-enameled section of the pipe, an annular seam 9, 10 is welded to the ends of the pipes. The welded connection “pipe-pipe-pipe” is subjected to mechanical cleaning of the inner surface and the subsequent operation of applying a heat-sensitive coating 3 to this surface. Moreover, before cleaning to protect the enamel coating of the pipes and partially overlap the enamelled area with a heat-sensitive layer (L _per ) from the free end of the pipes to the depth (2.9-3.0) L _W place removable elastic cylindrical protective elements (not shown in Fig.). After applying a heat-sensitive coating to the pipe-to-pipe-to-pipe connection and removing protective elements from the pipes, the indicated element of connection with each other is welded into the pipe whip by welding the root joint 8 of the connecting enamelled sleeve 9 with pipes on the side of the internal enamel coating.

The proposed connection and its implementation provides reliable corrosion protection of the welded joint of pipes with a heat-sensitive inner coating using the claimed combination and layout of the connection elements: an enameled connecting sleeve, pipes with an internal enamel coating, corresponding to the grade composition of the steel and the pipe size. The connection is a promising technical and economic solution for the construction of pipeline systems for various purposes.

Execution example

The proposed method for connecting pipes was tested during installation of pipelines in a whip at the experimental sections of the workshop under industrial conditions. For this, 9 sets of prototypes of the elements of the compound with a different ratio of the declared parameters were used. Each set contained two samples of connected pipes made of steel of grade 20, with a diameter of 325 mm, a wall thickness of 6 mm, and a length of 1000 mm each, two samples of pipes of the same diameter, wall thickness and the same steel grade as the joined pipes, but earlier coated with silicate enamel of the ESBT-10 brand (TU 14-11-356-2011) according to well-known industrial technology, leaving the end part of the inner surface of the nozzles free of enamel coating, and the connecting sleeve enameled with enamel ESBT-10, the sleeve VSE-A-325x6 (st20) length 30 mm according to TU 14-2R-387-2011 complete with mo platemaking slip. According to the well-known technology, pipes and nozzles from the side of an unprotected silicate-enamel coating were connected by welding. After cleaning the inner surface of the weld, the inner surface of the pipes and the surface of the nozzles not coated with enamel were shot blasted to prepare the surface for coating. Moreover, to protect against damage by a fraction of the enamel coating, a thin-walled cylindrical protective element was installed in the cavity of the nozzles, having a longitudinal section for possible compression during installation and subsequent fixing during compression. After shot-blasting, the protective thermosensitive coating (epoxy) with the overlapping of the silicate-enamel coating of the nozzles was applied to the inner surface of the pipes to be connected with welded pipes in the factory using the existing technology. After removing the protective elements from the ends of the nozzles, the pipes were connected by welding the connecting enameled sleeve with nozzles.

The quality control results of the obtained pipe compounds of the claimed method are shown in the table.

Thus, the proposed connection of pipes with an internal protective coating and the method of its implementation provide simplicity and reliability of the connection, the mechanical strength of the joint, the reliability of the corrosion protection of the metal of the pipes with the internal heat-sensitive coating from the pumped aggressive fluid.

Claims (2)

1. The connection of the pipes with an inner coating, comprising two pipes, a connecting enameled sleeve with a cut along its length and a radial protrusion made along the perimeter of its middle section, the width (l) and the height (h) of the radial protrusion, as well as the length (L) bushings and the thickness (t) of its wall are related to the thickness (S) of the wall of the connected pipes, respectively, as l / S = (0.1-0.3), h / S = (0.3-0.6), L / S = (2-5), t / S = (0.12-0.35), located between the inner surface of the ends of the pipes to be connected and the outer surface of the sleeve, a low-melting anti-corrosion coating, characterized in that between the ends of the pipe with internal thermosensitive coating and a connecting sleeve welded enamelled annular nozzles corresponding branded chemical composition and dimensional values of the pipe, wherein each pipe length (L _rds) is not less than 4.0 connecting enameled sleeve length (L _W) and its inner surface has a high-temperature silicate-enamel coating of the branded enamel composition of the connecting sleeve on the pipe section with a length of (3.1-3.5) L _W from its end from the side of the a root root suture with an enamelled sleeve, the heat-sensitive coating being a continuous continuous layer on the inner surface of the pipe and pipes connected to it by welding with partial overlap of the surface of the silicate-enamel coating of the pipe by the amount of (0.1-0.5) L _W. 2. A method of connecting pipes with an inner coating, including preparing the connection elements for assembly, forming protective coatings of the connection elements, welding them, characterized in that the connection is carried out using the relationship of the elements and their size ratios according to claim 1 in the sequence: silicate enamel is fused coating the inner surface of long sections of pipes (3,1-3,5) L and _W by fittings neemalirovannogo circumferential seam portion is welded with the ends of the pipe, weld "pipe-pipe-patra c 'is mechanically sweep the inner surface and the subsequent operation of application on the surface of the heat-sensitive coating, wherein prior to stripping the enamel coating to protect the nozzles and partially overlap enamelled thermosensitive layer portion with a free end of each pipe to a depth of (2,9-3,0) L _W place a removable elastic cylindrical protective element and after applying the heat-sensitive coating and removing the protective elements from the nozzles, the pipes are connected by welding extension enameled sleeve with nozzles.

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