RU2352856C1 - Repair method of long-distance sections of active pipelines - Google Patents

Abstract

FIELD: engineering industry.

SUBSTANCE: invention refers to pipeline transport, and is used when repairing main gas lines. A pair of process rings is installed on both sides of defective long-distance pipeline section. Inner end faces of paired rings are attached to pipeline surface. One more pair or several pairs of process rings are installed on defective section. Coupling rings are installed symmetrically on each pair of process rings. Couplings are installed on free parts of the nearest process rings of neighbouring pairs. Cavities between paired rings are filled with self-curing mass, and after that the whole space under the coupling is filled with such mass.

EFFECT: improving pipeline reliability.

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Description

The invention relates to techniques for repairing pipeline transport, mainly gas pipelines.

During long-term operation of gas pipelines, on their linear sections as a result of corrosion processes, mechanical and chemical influences, numerous defects appear (shells, caverns, cracks, fistulas, dents, delamination of the pipe metal, corrugations, etc.). In some cases, defects are unacceptable for the safe operation of the pipeline.

The method of repairing linear sections of a gas pipeline by installing a process coil on an emergency section of a pipeline is widely known (see, for example, the Rules for Overhauling the Linear Part of Gas Pipelines. VSN 2-112-79. - Moscow: VNIIST, 1973, pp. 34-35) . The method is as follows. The emergency section of the pipeline is localized and gas is pumped out of it. After that, the part of the pipe containing the defect is cut out and a technological coil is welded in its place. The method is radical, essentially repeating the installation of the pipeline. At the same time, it has significant drawbacks associated with the complexity, inevitability of large financial costs associated with the need to bleed gas and forced downtime of the pipeline.

A known method of repairing linear sections of pipelines by installing a repair sleeve filled with an adhesive composition (see, UK Patent Application, GB, 2210134 A). The method can be used without reducing the pressure in the pipeline. The repair structure consists of two coupling halves. In the process, the coupling halves are mechanically connected to each other, forming a closed shell around the repaired section of the pipeline. Next, the shell is centered using technological elements (bolts) installed in the holes of the housing. After that, the space between the pipeline and the coupling is sealed at both ends with a self-hardening compound (cement, epoxy putty, etc.). An epoxy composition is pumped into the insulated gap through special fittings, which ensures high structural rigidity.

This method of repairing almost all types of non-through defects has been widely used in linear sections of pipelines operating under high pressure. Pipeline sections so repaired have, as a rule, higher strength than adjacent undamaged pipe sections. Despite the wide distribution, the method has significant disadvantages associated with the impossibility of introducing an epoxy filler under high pressure. In the future, due to changes in the geometric dimensions of the pipeline due to pressure differences of the pumped product and temperature deformations, the epoxy layer may delaminate, which can lead to a decrease in the rigidity and tightness of the structure. In addition, the relatively low filling pressure with the epoxy composition of the space under the coupling, taking into account its shrinkage during solidification, allows the appearance of voids. The maximum filling pressure under the coupling is limited by the strength of the insulating gaskets at the ends. Installing the coupling allows you to reduce the radial load on the defective area, but does not compensate for axial loads, which is of great importance for defects in the form of corrugations resulting from mechanical longitudinal compression of the pipeline or with extensive corrosion damage around the circumference of the pipe.

A known method of repairing a pipeline under pressure by installing technological elements on it (see ed. St. USSR 1058182). The method allows repairing a defective section of a pipeline by installing parts of a split sleeve on it with further welding of the parts together. The ends of the coupling with a given penetration value are welded with annular seams to the pipe walls. To prevent the loss of stability of the pipe due to its overheating, rings are installed at a certain distance from the ends of the coupling, which are welded together with the coupling and the pipeline. The method allows to repair a defective section of the pipeline, while compensating for both radial and axial stresses, however, it does not allow to repair a pipe having a corrugation, as well as defective welds. In addition, the method has limited use for repairing long sections because of the complexity of manufacturing a repair sleeve that accurately repeats the profile of the pipeline section being repaired.

A known method of repairing a pipeline under pressure by installing technological elements on it (see ed. St. USSR 1680473). The method allows repairing a defective section of a pipeline by installing parts of a split sleeve on it with further welding of the parts together. Unlike the previous analogue, in this method, the coupling is replaced by several couplings, welded to each other and the pipe wall with annular seams. The method allows you to repair a linear section of the pipeline of arbitrary length, but is not applicable for the repair of corrugations and defective welds. In addition, the method may not be applicable for repair of a pipeline with severe corrosion damage due to the danger of burn-through of the pipeline wall.

A known method of repairing defective sections of the pipeline (see patent of Ukraine 75859), which is the prototype of the claimed invention. The method is as follows.

First, parts of the rings and the split sleeve are manufactured. In the central sectors of the opposite parts of the coupling, fittings with taps are tightly fixed. Rings on the pipeline are installed in pairs, two on both sides of the repaired area. In this case, paired rings are installed at a small distance from each other. The width of the rings and the distance between the paired rings are not critical and should be selected for the specific conditions of the repair. When installed on a pipeline, parts of the rings are pressed tightly against the surface of the pipe using a centralizer or other mechanisms of similar purpose and fastened together, for example, glued, welded or soldered. The close ends of the rings are attached to the surface of the pipeline, for example, by welding. After that, parts of the coupling are mounted on the rings, which are pressed to the surface of the rings and fastened together in the longitudinal direction, for example, soldered, welded or twisted with bolts. In this case, the clutch is installed so that its ends are located above the extreme rings. The ends of the coupling are attached to the surface of the corresponding extreme rings. Further, holes are made in the coupling that exit into the cavity between the paired rings. Additional taps are installed in the holes. After that, through additional taps, a cavity is formed that is formed by paired rings, the outer wall of the pipeline and the inner wall of the coupling, a self-vulcanizing sealant. After the end of the process of self-vulcanization of the sealant, seals are formed along the edges of the coupling - ring gaskets localizing the sub-coupling space. After this, the coupling space is filled with a self-vulcanizing sealant.

The method selected as a prototype allows for repair of sections of pipelines having almost all types of non-through defects, but has limited use on pipelines having extended defective sections (more than 1.5D, where D is the diameter of the pipeline), especially if the defects are located on bends of the pipeline. This is due to the complexity of manufacturing the coupling, repeating the relief of the repaired section of the pipeline. In addition, when filling a large volume of coupling space with a sealant, it is difficult to ensure uniform pressure distribution over the entire surface of the defective area, which reduces the quality of repair.

In addition, the scheme used in the prototype is not without drawback. The fact is that the rings do not carry the main load. Therefore, in practice, they are made of easily weldable, soft and sufficiently thin material (for main gas pipelines 10 mm), which allows the ring to be pressed tightly, without gaps, to the pipeline. The entire load from the pipe being repaired is transferred to the coupling, therefore, for its manufacture, durable steel with a thickness of 16-24 mm is used. To carry out tight, without gaps, clamping the coupling to the rings is quite difficult. If there are gaps between the coupling and the inner ring, it is also quite difficult to create the required sealant pressure between the pair rings.

The basis of the invention is the task of simplifying the repair of extended sections of pipelines while improving the quality of repairs through the use of a multi-section coupling with dividing the coupling space into zones using additional pairs of rings filled with self-hardening mass. This will create a rigid coupling shell around the pipe, repeating the profile of the repaired linear section of the pipeline of arbitrary length. The division of the coupling space into small zones will ensure uniformity of filling it with a self-hardening mass and thereby improve the quality of repair.

The problem underlying the invention is solved due to the fact that in the method of repairing extended sections of existing pipelines, which includes installing on the pipeline from two sides of the defective section two pairs of process rings, attaching their inner ends to the surface of the pipeline, installation on process rings parts of a split repair coupling, fastening them together, attaching the ends of the coupling to the surface of the respective rings, filling under pressure the spaces between the twin rings according to the invention, between the pairs of process rings mounted on both sides of the defective section, at least one or more pairs of additional process pipes are fixed on the pipeline rings, after which coupling rings are symmetrically installed on each pair of technological rings, the width of which is chosen equal to the distance between the s mmetry of the technological rings of the corresponding pair, after which the ends of the coupling rings are attached to the surface of the corresponding technological rings, in addition, on the free parts of the nearest technological rings of adjacent pairs, parts of split repair couplings are installed, which are pressed to the rings and fastened together, while the ends of the couplings are attached to the surface of the respective process rings.

The essence of the invention is as follows. On two sides of an extended section of the pipeline, recognized as defective, are installed on a pair of process rings. In this case, paired rings are installed at a small distance from each other. The width of the rings and the distance between the paired rings are not critical and should be selected for the specific conditions of the repair. When installed on a pipeline, parts of the rings are pressed tightly to the surface of the pipe using a centralizer or other mechanisms of similar purpose and fastened together, for example, glued, welded or soldered. The inner ends of the paired rings are attached to the surface of the pipeline, for example, welded, soldered or glued. After that, the pipeline section bounded by rings is conventionally divided into elementary sections, the length of which should not exceed 1.5 D, where D is the diameter of the pipeline. In places of conditional separation establish additional pairs of rings. Coupling rings are symmetrically installed on each pair of technological rings, the width of which is chosen equal to the distance between the centers of the technological rings of the corresponding pair. The ends of the coupling rings are attached to the surface of the respective process rings. After that, on the free parts of the nearest technological rings of adjacent pairs, parts of split repair couplings are installed, which are pressed to the rings and fastened together in the longitudinal direction. The ends of the couplings are attached to the surface of the respective process rings. After this, the cavities between the paired rings are filled under pressure with a self-hardening mass (for example, sealant or epoxy). Self-hardening mass is pumped into the cavity using a syringe or pump through taps that are pre-installed in the lower and upper parts of the coupling rings. After the solidification of the mass (the end of the process of self-vulcanization of the sealant) between the paired rings, seals are formed - ring gaskets that hermetically divide the coupling space into zones. After this, the coupling sleeve area is filled with a self-hardening mass using a syringe or a pump through pre-installed additional valves.

To simplify the design, coupling rings may not be installed on the extreme pairs of process rings. In this case, the extreme couplings are installed so that one end of each of them is located on the corresponding extreme technological ring, and the other on the free part of the nearest additional technological ring.

The greatest effect of the repair will be achieved when using technological rings and elements of welding couplings for fastening. In this case, maximum compensation is achieved for both circumferential and axial stresses arising in the pipeline section being repaired. In this case, only the inner ends of the extreme pairs of rings that are outside the defective area are directly welded to the pipeline. The use of welding to fasten the inner rings may be limited by the degree and nature of the damage to the pipe wall. The fixing of the inner rings on the pipeline in case of significant damage to its surface can be carried out by strong pressing of the rings to the pipeline during its installation, as well as through the use of soldering or gluing of contacting surfaces.

The method is illustrated by drawings.

Figure 1-3 schematically shows a section of the pipeline, repaired by the proposed method, where 1 is the pipeline; 2 - extreme pairs of technological rings; 3 - inner pairs of process rings; 4 - coupling rings; 5 - couplings; 6 - additional cranes; 7 - a syringe; 8 - self-hardening mass.

Figure 4 schematically shows a section of the pipeline, repaired by the proposed method, without installing the coupling rings on the extreme pairs of process rings, where 1 is the pipeline; 2 - extreme pairs of technological rings; 3 - inner pairs of process rings; 4 - coupling rings; 5 - couplings; 6 - additional cranes; 7 - a syringe; 8 - self-hardening mass; 9 - extreme clutch.

Thus, in the present invention, a sleeve of arbitrary length can be composed of a finite number of seals connected by simple couplings. Each seal, in turn, consists of two rings pressed to the pipeline, interconnected by coupling rings.

The thickness of the process rings determines the volume of the coupling space, and therefore the volume of self-hardening mass pumped into it. Therefore, it is desirable to choose a ring thickness as small as possible. In most cases, the practical use of the proposed method, the thickness of the rings should be less than the wall thickness of the used repair clutch.

The method can be used on any pipelines, however, the greatest effect is achieved when repairing large gas pipelines of large diameter (more than 700 mm).

Claims (3)

1. The method of repairing long sections of existing pipelines, which consists in installing technological rings on the pipeline, mounting on the technological rings and fastening parts of repair couplings together, attaching the ends of the couplings to the surface of the corresponding technological rings with further filling of the coupling space with a self-hardening mass, characterized in that at first on the pipeline, within the defective area, several pairs of process rings are installed, after which each pair of process rings the sleeves symmetrically install the coupling rings, the width of which is chosen equal to the distance between the centers of the technological rings of the corresponding pair, after which the ends of the coupling rings are attached to the surface of the corresponding technological rings, then on the free parts of the nearest technological rings of adjacent pairs install parts of split repair couplings that are pressed against the rings and fasten together, while the ends of the split repair couplings are attached to the surface of the respective process rings, then wide GUSTs between paired rings is filled under pressure self-hardening mass, whereupon a similar mass, under pressure, commensurate with the pressure inside the pipeline is filled space podmuftovoe each section formed corresponding to the repair coupling, piping and associated technological rings. 2. The method according to claim 1, characterized in that welding is used to fasten the structural elements to each other, while the inner ends of the extreme pairs of technological rings are welded directly to the pipeline, and the additional technological rings are fixed relative to the pipeline by clamping, as well as by soldering or bonding contact surfaces. 3. The method according to claim 1, characterized in that the thickness of the process rings is chosen smaller than the wall thickness of the split couplings.

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