RU2687476C1 - Method of pipeline repair without decommissioning - Google Patents

Abstract

FIELD: valve industry.SUBSTANCE: invention relates to construction and repair of metal pressure pipelines without decommissioning, and can be used in repair and reconstruction of reservoirs, boilers and high pressure vessels. Proposed method comprises determination of pipeline damaged section, removal of insulation coating and cleaning of repair zone. To recover strength and stiffness of damaged section of pipeline 1, split steel coupling 2 is used, inner diameter of which is equal to outer diameter of pipeline. Parts of the coupling are installed on the outer surface of the pipeline and connected. Sections of outer surface of coupling 3 are heated to temperature of plastic deformation and after cooling there applied is sealing compound in zones of coupling ends.EFFECT: improvement of repair quality due to possibility of restoration of carrying capacity of pipeline by recovery of strength and rigidity of pipeline on damaged section to level close to level of defect-free design in various conditions of repair and operation, and also reduction of labor intensity of repair works.1 cl, 1 dwg

Description

The invention relates to the field of construction and repair of pipelines and can be used in the repair of pipelines, as well as the reconstruction of tanks, high pressure vessels, i.e. constructions made of parts with developed cylindrical surfaces.

Known variants of the method of repair of pipelines installing detachable coupling, for example [1; 2, s. 108-114; 3, s. 18-19], including the operation of cleaning the surface of the pipe, connecting the parts of the coupling, applying a fast-hardening polymer material to fill defects with a preliminary discharge of the working pressure in the pipeline.

The disadvantage of this method is the necessity of relieving the working pressure in the pipeline, which adversely affects the performance of the pumping process.

There are variants of the method of repairing pipelines by installing a detachable coupling, for example [4-10], which includes cleaning the surface of the pipe, connecting the coupling parts, centering the coupling, installing end seals to seal the under-coupling space, pumping under pressure into the under-coupling space of a fast-hardening polymer material and then maintaining pressure before curing the polymer material.

The main disadvantage of the known methods is the inability to regulate the amount of back pressure in different parts of the repaired area, which is advisable to do depending on the degree of damage to individual parts of the repaired area. Other disadvantages are due to the properties of existing polymeric materials:

- temperature restrictions on the curing mode: low curing speed at low temperatures, which makes it impossible to apply the method on pipelines pumping cooled media, and a sharp increase in the curing rate at elevated temperatures (pumping hot water, steam, heated viscous liquids), which may not allow completely fill the coupling space and create the required backpressure;

- temperature limitations on operating conditions: polymer embrittlement at low temperatures and a decrease in adhesion and elastic properties at elevated temperatures;

- low thermal conductivity of the polymer can lead to temperature differences in the pipeline and the coupling, which inevitably affect the amount of back pressure.

The closest technical solution to the claimed method is the repair of pipelines with local defects [11], which consists in applying to the prepared surface of the pre-cooled pipeline a preheated tape and then fixing it on the pipeline.

The known method has low efficiency due to the following factors:

- the inability to sufficiently evenly cool the wall of the pipeline throughout its thickness, since the temperature of the internal surface of the pipeline is almost equal to the temperature of the pumped medium. The use of a refrigerant with a very low temperature will result in significant tensile mechanical stresses in the surface layers of the pipeline wall, which can lead to surface cracks, especially since at low temperatures the plasticity of almost all structural materials decreases and the tendency to brittle fracture increases;

- the inability with sufficient accuracy to ensure the required temperature difference between the pipeline and the tape for the period of time necessary for winding the tape and its fixation due to the inevitable heat exchange between the tape and the pipeline.

The purpose of the invention is to improve the efficiency of repair by providing the possibility of restoring the bearing capacity of the pipeline by restoring the strength and rigidity of the pipeline on the damaged section to a level close to the level of defect-free pipe in various repair and maintenance conditions, as well as reducing the complexity of repair work.

This goal is achieved due to the fact that in the method of repairing the pipeline without decommissioning, consisting in stripping the repaired pipeline section, installing on the outer surface of the pipeline a split coupling with an inner diameter equal to the outer diameter of the pipeline, fastening its parts, according to the invention after fixing the split coupling parts sections of the outer surface of the coupling are heated to the temperature of occurrence of plastic deformations and after cooling, a sealing compound is applied in the torus zones coupling coupling The coupling on the ends is partially or fully welded to the pipeline. Between the coupling and the pipeline place a layer of fiberglass.

The proposed method of repairing the pipeline without decommissioning is as follows. Trim the repaired section of the pipeline. Make a detachable coupling, the inner diameter of which is equal to the outer diameter of the repaired pipeline. An anticorrosive treatment of the outer surface of the repaired pipeline section and the inner surface of the coupling is carried out; for this, in particular, passivation, phosphating, and sputtering of aluminum can be used. Install the coupling on the repaired section of the pipeline and connect its parts. Sections of the outer surface of the coupling are heated to the temperature of occurrence of plastic deformations, for example, by welding the bead with electric welding. Apply a sealing compound in the area of the ends of the coupling. The coupling on the ends is partially or fully welded to the pipeline. If necessary, reduce the temperature of the heating wall of the pipeline, between the pipeline and the coupling set of insulating material, such as a layer of fiberglass.

The proposed method is illustrated in FIG. one.

FIG. 1 is a drawing explaining the operations of the proposed method for repairing a pipeline without decommissioning, where: 1 is a pipeline; 2 - split coupling; 3 - sections of the outer surface of the coupling, subjected to heating to the temperature of occurrence of plastic deformations.

When heated, the yield strength of the material of the coupling is significantly reduced, as a result of mechanical stresses due to thermal expansion of the material fall to almost zero value. Upon subsequent cooling, the material is compressed in previously heated areas, due to which the coupling compresses the pipeline, as a result, the amount of mechanical circumferential stresses in the pipeline is reduced.

If it is necessary to simultaneously reduce axial stresses, before the operation of heating sections of the outer surface of the coupling to the temperature of occurrence of plastic deformations, the coupling is partially or fully welded to the pipe wall at the ends. When cooling previously heated sections, the material is compressed in the axial direction, due to which the coupling in the axial direction compresses the pipeline, as a result, the value of mechanical axial stresses in the pipeline decreases

The temperature of the heating, the shape and size of the heated areas are determined on the basis of thermal strength calculation. If necessary, reduce the temperature of the heating wall of the pipeline, between the pipeline and the coupling set of insulating material, such as a layer of fiberglass.

Sources of information taken into account

1. RF patent №2097646, 1995, F16L 57/00

2. Zabela K.A., Kraskov V.A., Moskvich V.M., Soschenko A.E. Safety of water pipelines intersections - Moscow: Nedra-Business Center LLC, 2001. - 195 sec. Il.

3. Guidance document for Instructions for the repair of pipelines and tanks using polymer adhesive compositions RD-39-30-968-83, - M. 1984

4. RF patent №2104439, 1998, F16L 55/175

5. RF patent №2213289, 2003, F16L 55/175

6. RF patent №2222746, 2004, F16L 55/175

7. RF Patent No. 2292512, 2007, F16L 55/175

8. RF patent №2352854,2009, F16L 55/175

9. RF patent №2449204, 2012, F16L 55/175

10. RF patent number 2451233, 2012, F16L 55/175

11. USSR author's certificate №1707419, 1989, F16L 55/18

Claims (2)

1. The method of repairing the pipeline without decommissioning, which consists in stripping the repaired section of the pipeline, installing the split coupling on the outer surface of the pipeline and fixing its parts, characterized in that the coupling is performed with an internal diameter equal to the outer diameter of the repair pipeline, after fixing the split coupling parts sections of the outer surface of the coupling are heated to the temperature of occurrence of plastic deformations and, after cooling, a sealing compound is applied in the zones of the ends of the coupling. 2. The method according to p. 1, characterized in that the coupling on the ends partially or fully welded to the pipeline.

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