RU2530943C2 - Assembly of pipe weld heat isolation for overhead laying - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to pipe covering, particularly, to application of covering at welds of oil pipes. Proposed process comprises application of antirust protection to pipe weld joint with the help of thermosetting polymer tape. Heat-insulating shells of foam polyurethane are fitted at the joint and coupled by tie tapes with locks. Hot melt adhesion tape is glued to edges of the pipe covering to overlap said shells of foam polyurethane. Protective zinc plated case is arranged in symmetry with weld joint centre to cover weld joint and protective shell over preset distance.

EFFECT: better heat insulation, perfected and simplified process, lower labour input.

9 cl, 2 tbl, 2 dwg

Description

The invention relates to thermal insulation of pipes and is intended to provide for the installation of thermal insulation of welded joints of pipes of an oil pipeline intended for transportation of oil and oil products.

The invention is known "Method of thermal insulation of pipes for air, surface and underground laying" (see patent RU No. 2386076, application No. 2007115515/06, published November 20, 2009, IPC F16L 59/14, F16L 59/10), in which for thermal insulation of pipes for air, surface and underground laying concentrically installed relative to the insulated pipe, prefabricated sections of rolled sheet metal shells that simultaneously perform the form and protective coating of thermal insulation are filled through a longitudinal joint in an open state the sleeve an annular cavity between the tube and shell polyurethane foam (PUF) flood marks, closed longitudinal joint shell with overlapping edges and held while structuring the heat-insulating material. However, this method is not applicable in the field due to the impossibility of using PPU filling brands at low temperatures.

The invention is known "The insulated joint of pre-insulated pipes with a polymer sheath, the method of its installation, the polymer sleeve and the method of its manufacture" (see patent RU No. 2389943, application No. 2008137715/06, published May 20, 2010, IPC F16L 59/18, F16L 58 / 00), which proposes a method of mounting a polymer sleeve covering the ends of the polymer shells of adjacent pipes. A sealant is located between the outer surfaces of the ends of the pipe shells covered by the coupling and the inner surface of the ends of the coupling, and the heat-insulating material fills the space of the coupling. The edges of the coupling are protected by an operational bandage made of flexible ties with separate fixation or tapes fixed by a lock. The disadvantage of this method is the insufficient durability of the polymeric material of the coupling in difficult climatic conditions and the protection of the heat-insulating material of the joint from external natural and artificial mechanical stresses with an overhead arrangement of the pipeline.

The invention is known "Method of applying a thermal insulation coating to a pipe" (see patent RU No. 2136495, application No. 97118577, published 1999.09.10, IPC B29C 63/18, F16L 59/14), which consists in applying a thermal insulation coating from a foaming material - PPU on the outer surface of the pipes, an elastic shell is placed on top of the pipe. However, the method is not applicable on welded pipelines, as it requires additional fixtures - forms, which complicates and increases the cost of thermal insulation, requires additional sealing work. In addition, the disadvantages of the previous patent remain.

Closest to the proposed method is the invention "Heat-insulating joint of pre-insulated pipelines and a method for its implementation" (see application RU, No. 2002108868/06, published November 27, 2003, IPC F16L 59/18), which is taken as a prototype of the invention.

The specified invention includes a method of making a heat-insulating joint of previously insulated pipelines, including connecting by welding the ends of the steel pipelines to each other, presetting symmetrically with respect to the welded joint of the metal casing wrapped around the joint, which is filled with PUF between the inner surface of the casing, the outer surface of the pipelines connected to each other and the ends thermally insulated material of these pipelines, after which they activate the joint surface but warming its flame gas burner and gradually shrink superposed web as it warming gas burner flame.

However, this method is not applicable in the field at low temperatures, because the use of polyurethane foam filler grades requires positive temperatures. In addition, there is no anti-corrosion coating on the weld joint.

The objective of the proposed invention is to provide installation of an anti-corrosion coating and thermal insulation of the welded joint of heat-insulated pipes of above-ground laying in difficult climatic conditions (at low temperatures).

The technical result is to provide corrosion protection (due to the use of heat-shrinkable polymer tape) and thermal insulation of the welded joint of heat-insulated pipes, while the proposed method provides an improvement in the technology of installing thermal insulation on the pipeline, which reduces its cost of installation and reduces the complexity.

The technical result is achieved by the fact that they produce corrosion protection of the welded joint with the help of a heat-shrinkable polymer tape, close the joint with heat-insulating shells made of polyurethane foam and protect using a galvanized metal casing.

The method of mounting the heat insulation of the welded joint of heat-insulated pipes for above-ground laying is shown in FIG. 1 and FIG. 2 and includes installation symmetrically with respect to the welded joint of a galvanized metal casing wrapped around a joint that is filled with polyurethane foam between the inner surface of the casing, the outer surface of thermally insulated pipes and interconnected the ends of the heat-insulating material of these pipes, according to the invention, pre-produce corrosion protection of the welded pipe joint 1 s with the help of a heat-shrinkable polymer tape with a lock plate 2, heat-insulating shells made of polyurethane foam 3 are mounted on the joint, fastened with metal tapes 4 with locks 5, glued along the edges of the protective sheath 6 heat-insulated pipes 7 and 8 with a hot-melt adhesive tape 9 with an overlap on the shells made of polyurethane foam 3 galvanized metal casing 10 symmetrically with respect to the weld joint 1, overlapping the joint and the protective shell of insulated pipes.

Before installing a heat-shrinkable polymer tape, the surface of the welded joint and the adjacent zone is prepared, including cleaning, drying with a gas burner to a predetermined temperature with its control using a contact thermometer at four equidistant points along the perimeter of the joint and cleaning the metal surface with an abrasive blasting method.

Before installing a heat-shrinkable polymer tape on the prepared surface, a prepared primer is applied with an even layer of foam roller or spatula.

The overlap of the heat-shrinkable polymer tape on the factory coating of 11 thermally insulated pipes should be at least 50 mm for pipelines with a diameter up to 530 mm inclusive and at least 75 mm for pipelines with a diameter over 530 mm.

The heat-shrinkable tape is installed with an overlap of the upper edge to the lower. A lock plate is installed in the place of this overlap and it is heated by the burner flame, after which it is rolled by a silicone roller to remove air bubbles from under it and align all the material.

The anti-corrosion coating of the welded joint is checked, including the appearance, overlap on the factory coating of thermally insulated pipes, coating thickness, dielectric continuity and adhesion of the coating to the joint metal and in the place of overlapping of the upper edge of the heat-shrinkable polymer tape to the lower.

At least 3 pieces of metal tape with a lock are installed on the shell. (one in the center, two extreme ones - at a distance of 150 to 200 mm from the edge of the insulation shell connected at the welded joint of the insulated pipes).

The hot-melt adhesive tape is applied in two layers according to the marks of the edges of the galvanized metal casing on the shells of heat-insulated pipes, while the second edge of the tapes should overlap the shells of polyurethane foam.

The galvanized metal casing 10 is installed so that the overlap of the edge of the casing is oriented downward. The overlap must be in the positions corresponding to 1, 2 or 10, 11 hours and be at least 100 mm. Positions must be presented along the insulated pipes according to the clock hands.

The galvanized metal casing is installed symmetrically with respect to the welded joint and must completely close the joint and overlap the protective shell of thermally insulated pipes at a distance of at least 100 mm.

In the areas of overlap of the casing on insulated pipes and overlap of the edges of the casing, it is fastened with galvanized self-tapping screws with a pres washer 12 along the edges every 80-100 mm. The distance from the edge of the casing is from 10 to 20 mm.

Checking the quality of installation of the thermal insulation and the galvanized metal casing includes checking the appearance, the size of the overlap of the casing on the protective shell of thermally insulated pipes, the size of the overlap of the casing, the distance between the screws and the distance between the screws and the edge of the casing.

If there is a positive conclusion about the quality of the welded joint and the permit is issued by the technical supervision service for the work on thermal insulation of the welded joint, preliminary corrosion protection of the welded joint by heat-shrinkable polymer tape and its control are carried out.

The way the work.

Prepare the surface of the welded joint and adjacent zone at a distance of at least 200 mm. The surface is cleaned of dirt, dust, moisture and grease, the surface is dried by heating with a gas burner to a predetermined temperature with its control using a contact thermometer at four equidistant points along the perimeter of the joint.

The metal surface is cleaned by the abrasive blasting method, including the cleaning of the factory coating zone of thermally insulated pipes adjacent to the cleaned area at a distance of at least 100 mm from the edge of the coating.

Cleaning Options:

- degree of purification 2 according to GOST 9.402 or Sa 2.5 according to ISO 8501-1;

- surface roughness Rz from 40 to 90 microns according to ISO 8503-1;

- dustiness of the surface is not higher than standard 3 according to ISO 8502-3.

Using a gas burner, the prepared surface (steel and factory coating) is heated to a temperature specified by the manufacturer for this brand of heat-shrinkable polymer tape, with its control using a contact thermometer at four equidistant points along the perimeter of the joint.

The prepared primer is applied to the prepared surface with a foam roller or spatula in an even layer (the time from the moment of mixing to application should not exceed the time specified in the manufacturer's technological documentation).

The heat-shrinkable polymer tape is installed on the surface treated with a primer.

The thickness of the heat-shrinkable polymer tapes is selected depending on the diameters of the pipeline (see table 1).

Table 1 The thickness of the coating zone of the welded joints, depending on the diameter of the pipeline Diameter of the pipeline, mm Minimum coating thickness, mm, not less than Up to 273 incl. 1,2 Over 273 to 530 incl. 1.8 Over 530 to 820 incl. 2.0 Over 820 2,4

A heat-shrinkable polymer tape is mounted around the welded joint with a polyethylene coating upward, and with an adhesive layer to the pipe. The overlap of the ends of the heat-shrinkable polymer tape on each other is at least 100 mm.

One end of the heat-shrinkable polymer tape is heated by the burner flame from the side of the adhesive layer, avoiding shrinkage of polyethylene, and then press it to the prime surface of the welded joint.

The overlap of the heat-shrinkable polymer tape on the factory coating of thermally insulated pipes is at least 50 mm for pipelines with a diameter up to 530 mm inclusive and at least 75 mm for pipelines with a diameter over 530 mm.

A heat-shrinkable polymer tape web is wrapped around an insulated surface. The upper edge of the heat-shrinkable polymer tape is heated by the burner from the side of the adhesive layer and pressed to the lower edge.

The overlap of the edges of the heat-shrinkable polymer tape is rolled with a silicone roller to remove possible air bubbles from the overlap zone. Thus closed in a ring, a heat-shrinkable polymer tape has the "sagging" fabric at the lower generatrix of the joint required for further shrinkage.

Install the lock plate and heat it with the flame of a burner, after which it is rolled with a silicone roller to remove air bubbles from under it and align all the material.

The shrinkage of the heat-shrinkable polymer tape begins immediately after the installation of the lock plate using a gas burner, evenly distributing the flame, starting from the lower generatrix of the joint, that is, in the zone of maximum slack of the tape.

The control of the anti-corrosion coating of the weld joint includes control of the appearance, overlap value on the factory coating of thermally insulated pipes, coating thickness, dielectric continuity and adhesion of the coating to the joint metal and in the place of overlapping of the upper edge of the heat-shrinkable polymer tape to the lower one.

Next, they install heat-insulating shells made of polyurethane foam. For this, the coated welded joint is cleaned. If necessary, the shell segments are cut to the desired size at the installation site.

The number of shell segments, depending on the diameter of the pipeline, corresponds to the values given in table 2.

When installing two segments, the joints of the shells should be in positions corresponding to 3, 9 hours, when installing three - at 2, 6, 10 hours, when installing four - at 2, 5, 8, 11 hours. Provisions should be presented along thermally insulated pipes along clock hands.

table 2 The number of shell segments depending on the diameter of the pipeline Diameter of the pipeline, mm The number of shell segments, pcs. Up to 820 inclusive 2 Over 820 to 1020 inclusive 3 Over 1020 four

Belts with a tensioning mechanism are installed on the shell, which tighten the shells until they are firmly connected, avoiding damage to the shell segments.

At least 3 pieces of metal tape with a lock are installed on the shell. (one in the center, two extreme ones - at a distance of 150 to 200 mm from the edge of the shell of thermally insulated pipes) and tighten the tapes using a tensioner.

The distance at which the galvanized metal casing will be installed is marked along the edges of the protective shells of thermally insulated pipes, after which the inner surface of the casing and the surface on the protective shell of the insulated pipe are degreased at least 150 mm from the edge with a solvent.

Consistently heating the edges of the protective shells of thermally insulated pipes with a burner flame, they glu the hot-melt adhesive tape in two layers at the edges. Tapes are installed according to the marks of the edges of the galvanized metal casing on the shells of thermally insulated pipes, while the second edge of the tapes should go with an overlap on the shells. Roll the tape with a roller so that it evenly fits on the shell.

Next, install a galvanized metal casing so that the overlap of the edge of the casing was oriented from top to bottom. The overlap must be in the positions corresponding to 1, 2 or 10, 11 hours and be at least 100 mm. Positions must be presented along the insulated pipes according to the clock hands.

The casing is installed symmetrically with respect to the welded joint and must completely close the joint and overlap the protective shell of the heat-insulated pipes forming the joint to a distance of at least 100 mm.

At a distance of 300 to 400 mm from the edges of the casing, belts with a tensioning mechanism are installed and tightened.

The edges of the casing are heated with a flame of a gas burner to melt the adhesive tape with a hot melt, and the belts with a tensioning mechanism are finally tightened. After installation, the galvanized metal casing should tightly fit the welded joint.

In the areas of overlapping heat-insulated pipes and overlapping edges of the casing, it is fastened with self-tapping galvanized screws with a washer along the edges every 80-100 mm. The distance from the edge of the casing is from 10 to 20 mm. After installing the screws, remove the temporary belts with a tensioning mechanism.

Checking the quality of installation of the thermal insulation and the galvanized metal casing includes checking the appearance, the size of the overlap of the casing on the protective shell of the insulated pipes, the size of the overlap of the edges of the casing, the distance between the screws and the distance between the screws and the edge of the casing.

The application of the proposed method provides corrosion protection and thermal insulation of the welded joint of heat-insulated pipes of above-ground laying at low temperatures. In addition, the proposed method provides an improvement in the technology of installing thermal insulation on the pipeline, which, in turn, reduces the cost of its installation and reduces the complexity.

Claims (9)

1. A method of installing heat insulation of a welded joint of pipes of an overhead gasket, comprising installing symmetrically with respect to a welded joint of a galvanized metal casing wrapped around a joint that is filled with polyurethane foam between the inner surface of the casing, the outer surface of the pipes interconnected and the ends of the heat-insulating material of these pipes, characterized in that pre-produce anti-corrosion protection of the weld joint using heat-shrinkable polymer tape with a lock plate, installed shells made of polyurethane foam are fastened to the welded joint, fastened with metal tapes with locks, a hot-melt adhesive adhesive tape is glued along the edges of the protective sheath of the pipes with an overlap on the polyurethane shells, and a galvanized metal casing is installed symmetrically with respect to the welded joint, overlapping the joint and the protective shell. 2. The method according to claim 1, characterized in that before installing the anti-corrosion protection of the welded joint, the surface of the welded joint and the adjacent area is prepared, including cleaning, drying with a gas burner to a given temperature with its control using a contact thermometer at four equidistant points at the perimeter of the joint and cleaning the metal surface with an abrasive blasting method. 3. The method according to claim 1, characterized in that before installing the heat-shrinkable polymer tape for corrosion protection of the welded joint on the prepared surface using the foam roller or spatula, the prepared primer is applied uniformly. 4. The method according to claim 1, characterized in that the overlap of the heat-shrinkable polymer tape on the factory coating of pipes is at least 50 mm for pipelines with a diameter up to 530 mm inclusive and at least 75 mm for pipelines with a diameter over 530 mm. 5. The method according to claim 1, characterized in that the lock plate is heated by the flame of the burner, after which it is rolled by a silicone roller to remove air bubbles from under it and align the entire material. 6. The method according to claim 1, characterized in that metal shells with a lock are installed on the shell in an amount of at least 3 pcs. (one in the center, two extreme - at a distance of 150 to 200 mm from the edge of the protective shells of the pipes). 7. The method according to claim 1, characterized in that the hot-melt adhesive tape is applied in two layers at the marks of the edges of the galvanized metal casing on the pipe shells. 8. The method according to claim 1, characterized in that the galvanized metal casing is installed so that the overlap of the edge of the casing is oriented downwards and is in positions corresponding to 1, 2 or 10, 11 hours, and it is necessary to make at least 100 mm of position to represent along the heat-insulated pipes according to the clock hands. 9. The method according to claim 1, characterized in that the casing is installed symmetrically with respect to the welded joint and must completely close the joint and overlap the protective shell of the pipes forming the joint, at a distance of not less than 100 mm