A method for repairing in-situ the thermal insulation of a district heating / cooling pipe

Abstract

A district heating / cooling pipeline in-situ insulation layer repairing method, comprising damaged insulation layer removal, support positioning tile installation, tile gap repair area outer pipe installation, repair section gas tightness test, repair section sectional perfusion foaming and foaming hole welding plugging. The application discloses a method for replacing and repairing the insulation layer of a pipeline in the field of central heating / cooling pipeline repairing engineering, which is used for replacing and repairing the insulation layer of a damaged pipeline in order to restore the sealing performance and the insulation performance of the outer protective pipe of the insulation pipeline, and is used for solving the problem of water damage to the insulation layer and loss of insulation performance caused by sealing defects of the outer protective pipe of the insulation pipeline laid directly in the area with high underground water level.

Description

Technical Field

[0001] This invention relates to the field of heating and cooling pipelines, and more particularly to a method for repairing in-situ insulation layers in district heating / cooling pipelines. Background Technology

[0002] In the construction of new pipelines for centralized heating, the vast majority of insulated pipelines are laid directly underground.

[0003] Groundwater levels are complex, and directly buried pipelines inevitably cross areas with high groundwater levels. In such environments, directly buried pipelines often suffer from groundwater intrusion into the insulation layer due to inadequate insulation performance of the outer protective pipe or cracks in the outer protective pipe. This causes the insulation layer to lose its insulation performance and mechanical strength due to prolonged water immersion, and in severe cases, the insulation material may decompose and disappear. Over time, the steel pipe will also gradually corrode due to external water intrusion, eventually leading to perforation and media leakage.

[0004] The problem of water ingress and damage to insulated pipes in environments with high groundwater levels is extremely likely to occur in heating pipeline projects.

[0005] Early detection of water ingress and damage to the insulation layer is relatively easy. During the heating season, steam will rise from the ground, and these areas often indicate where the insulation layer of the insulated pipes has been damaged. In the early stages, the steel pipes transporting the medium in the affected pipelines often haven't suffered any performance-related damage and can be restored to use after simple rust removal. However, due to a long-standing lack of technology and practice for repairing the insulation layer and outer protective layer of insulated pipes without removing the steel pipes, on-site repair of damaged pipelines is impossible. This leads to increased repair costs and situations where reliable sealing cannot be achieved even after repair, resulting in repeated damage from repeated cycles.

[0006] Patent application CN201910722603.5 discloses a "repair process for a prefabricated direct-buried insulated pipeline system," which involves repairing the welded joints of the pipeline with an outer layer of insulation. This process is only applicable to the outer insulation treatment of short-distance pipelines with small joints and is not suitable for repairing longer pipelines. Summary of the Invention

[0007] The purpose of this invention is to provide a method for repairing the insulation layer of district heating / cooling pipelines in situ. This invention discloses a method for replacing and repairing the insulation layer of pipelines in situ during pipeline repair projects in the field of district heating / cooling. This method addresses the problem of water ingress and loss of insulation performance of directly buried heating / cooling insulation pipes in areas with high groundwater levels due to sealing defects in the outer protective pipe. The method involves replacing and repairing the insulation layer of the damaged pipeline, thereby restoring the sealing performance and insulation performance of the outer protective pipe.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A method for repairing in-situ insulation layers of district heating / cooling pipelines includes: removing damaged insulation layers, installing supporting and positioning tiles, installing outer protective pipes in the repair area between tiles, installing outer sleeves in the patching area, and performing sectional injection foaming of the repair section and welding and sealing of the foaming holes; specifically including:

[0010] 1) Remove the damaged insulation layer to expose the medium conveying pipeline, and install the support positioning tiles in sections on the medium conveying pipeline. The installation method is: two semi-circular support positioning tiles are fitted together on the medium conveying pipeline.

[0011] The outer diameter of the support positioning tile has two radii, and the height difference between the two radii is consistent with the thickness of the outer protective tube of the inter-tile repair area. The outer protective tube of the inter-tile repair area is fitted onto the end with the smaller radius. The support positioning tile is made of polyurethane.

[0012] 2) Wrap the outer protective pipe of the tile repair area around and install it between the two adjacent sets of support positioning tiles. The two ends of the outer protective pipe of the tile repair area overlap with the support positioning tiles and are tied and fixed. Weld and seal the longitudinal butt joint of the outer protective pipe of the tile repair area on one side.

[0013] The two ends of the outer protective pipe in the tile repair area are tightened and fixed by the binding straps. Then, the longitudinal joint between the binding straps is beveled in a U-shape and hot melt filler is welded at the bevel. After the binding straps are removed, the longitudinal joints at both ends of the outer protective pipe in the tile repair area are welded and sealed in the same way.

[0014] When the number of outer protective pipes installed in the tile repair area is more than one section, the outer protective pipes in the tile repair area are installed at intervals between the supporting and positioning tiles; the outer protective pipes in the tile repair area are made of high-density polyethylene.

[0015] 3) Wrap electrofusion mesh tape around the original insulation outer protective pipe and the outer protective pipe of the tile repair area. The electrofusion mesh tape of the original insulation outer protective pipe is wrapped at one end close to the repair area, and the electrofusion mesh tape of the outer protective pipe of the tile repair area is wrapped at both ends of the outer protective pipe of the tile repair area.

[0016] 4) Install a patching area outer sleeve around the outer sleeves of adjacent tile repair areas and / or between the original insulation outer sleeve and the outer sleeve of the tile repair area. The two ends of the patching area outer sleeve overlap the outside of the electrofusion mesh belt and are fixed with a binding tightening strap. The patching area outer sleeve is made of high-density polyethylene.

[0017] 5) Use an electrothermal welding machine to weld the electrothermal mesh belt to the outer protective pipe of the repair area and the outer sleeve of the patching area between the upper and lower tiles, or the original insulation outer protective pipe and the outer sleeve of the patching area in a circumferential weld to seal them.

[0018] 6) Weld and seal the longitudinal butt joint on one side of the outer sleeve in the patching area;

[0019] First, the longitudinal butt joint on one side of the outer sleeve in the joint area is beveled. The bevel is a U-shaped bevel, and then hot melt filler welding is performed at the bevel.

[0020] 7) Conduct an overall airtightness test by injecting compressed air into the inner cavity through drilling to check for leaks in the weld.

[0021] 8) By creating foam holes in the outer protective pipe of the tile repair area and the outer sleeve of the joint repair area, foaming material is injected into the outer protective pipe of the tile repair area and the outer sleeve of the joint repair area, and then the foam holes are sealed.

[0022] Drill at least two holes on the outer protective pipe of the tile repair area and the outer sleeve of the patching area as grouting holes and foaming venting holes respectively. Inject foaming material into the outer protective pipe of the tile repair area and the outer sleeve of the patching area through the grouting holes respectively, and then seal the grouting holes and foaming venting holes by hot-melt welding.

[0023] An alarm line can be placed inside the cavity before the outer protective pipe in the repair area between the pipe sets and the outer sleeve in the joint area, providing the basic conditions for installing a pipeline leak monitoring system.

[0024] A repair structure for an in-situ insulation layer repair method for district heating / cooling pipelines includes a support positioning tile, an outer protective pipe for the inter-tile repair area, an outer sleeve for the patching area, an electrofusion mesh belt, and a foam layer. The support positioning tiles are installed in sections on the medium conveying pipeline. The support positioning tiles have a semi-circular structure and are fitted together on the medium conveying pipeline. The outer diameter of the support positioning tiles has two radii, and the height difference between the two radii is consistent with the thickness of the outer protective pipe for the inter-tile repair area. The outer protective pipe for the inter-tile repair area is fitted between two adjacent support positioning tiles, and the two ends of the outer protective pipe overlap the smaller radius end of the support positioning tile.

[0025] When the number of outer protective pipes installed in the tile repair area is more than one section, the outer protective pipes in the tile repair area are installed at intervals between the supporting and positioning tiles;

[0026] The outer sleeve of the repair area is fitted between the outer sleeves of the adjacent tile repair areas and between the original insulation outer sleeve and the outer sleeve of the tile repair area. The overlapping outer sleeve of the tile repair area and the outer sleeve of the repair area are sealed by welding with an electrofusion mesh belt. The overlapping original insulation outer sleeve and the outer sleeve of the repair area are also sealed by welding with an electrofusion mesh belt.

[0027] A foam layer is filled between the outer protective pipe of the tile repair area, the outer sleeve of the patching area, and the medium conveying pipeline;

[0028] The longitudinal joint of the outer protective tube in the tile repair area and the outer sleeve in the patching area is welded and sealed at the rear side.

[0029] This invention discloses the materials, equipment, processes, and implementation methods used for in-situ insulation layer repair of thermal insulation pipes. It includes the supporting positioning tiles, high-density polyethylene sheets, polyurethane foam raw materials, and the entire repair operation process used in the in-situ insulation layer repair.

[0030] The supporting and positioning tiles used in the in-situ insulation layer repair are made of polyurethane, and the molded foam forming is a half-tile with a semi-circular angle of 180 degrees.

[0031] The insulation material used in the in-situ insulation layer repair is used to support and position the half-tiles and for the on-site foaming process. The insulation material is rigid polyurethane foam, a two-component material consisting of polyether and isocyanate, mixed and molded under high pressure atomization. The material ratio is polyether:isocyanate = 1:1.5 (by weight). After mixing, the polyether and isocyanate materials have a foaming time of not less than 60 seconds and a free foaming density of not less than 48 kg / m³ under laboratory conditions.

[0032] The high-density polyethylene (HDPE) sheets used for in-situ insulation layer repair must meet all the requirements for HDPE materials in GB / T29047 standard. The thickness of the HDPE sheets is determined based on the diameter of the pipe to be repaired.

[0033] The extrusion welding machine in this invention is a manual extrusion high-density polyethylene welding machine with automatic temperature control function. The preferred manual extrusion welding machine is the WELDPLASTS2 model from LEISTER, Switzerland.

[0034] The electrothermal welding equipment used in this invention is preferably the Swedish-imported TSC6.0PRO fully automatic electrothermal high-density polyethylene welding equipment.

[0035] The binding tension strap used in this invention is a complete binding tension strap with a ratchet tensioner.

[0036] Compared with existing technologies, the beneficial effects of this invention are:

[0037] 1) This invention enables the performance of directly buried insulated pipes in high-water environments, where the insulation layer and outer protective layer are frequently damaged by water immersion, to be restored through in-situ repair without having to completely cut off the original pipe and replace it with a new one. This saves on the costs of transportation, secondary welding, and secondary return to the factory for insulation that would otherwise be incurred during the replacement process.

[0038] 2) The in-situ insulation layer replacement and repair technology of the steel pipe of the present invention ensures that the prestress effect generated by the preheating installation during the original pipeline installation process is still effective, avoiding the repeated installation of prestress caused by replacing the pipeline, and saving pipeline installation costs.

[0039] 3) The in-situ insulation layer replacement and repair technology of the steel pipe of the present invention makes it possible to quickly repair damaged pipelines, avoid the waste of heating medium during the repair process, and save the cost of heating medium loss.

[0040] 4) This invention can also be applied to the emergency needs of local insulation treatment for newly built pipelines. As needed, an alarm line can be added during the replacement and repair of the in-situ insulation layer, thus providing the basic conditions for installing a pipeline leak monitoring system.

[0041] 5) The present invention has been verified and tested by the applicant through in-situ repair projects of directly buried insulation pipes in high water level environments, which proves that the in-situ insulation layer replacement and repair technology is feasible and reliable. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the support and positioning tile for repairing the insulation layer of the present invention.

[0043] Figure 2 yes Figure 1 Side view.

[0044] Figure 3 This is a schematic diagram showing the aftermath of removing the damaged insulation layer and outer protective pipe of the heating / cooling pipeline.

[0045] Figure 4 This is a schematic diagram of installing support and positioning tiles on a medium conveying steel pipe.

[0046] Figure 5 This is a schematic diagram showing the complete installation of the segmented support positioning tiles.

[0047] Figure 6 This is a schematic diagram of the installation and tightening of the outer protective pipe in the half-wall repair area.

[0048] Figure 7 This is a schematic diagram of the longitudinal joint beveling treatment of the outer protective pipe in the half-tile repair area.

[0049] Figure 8 This is a schematic diagram showing the completion of the longitudinal joint beveling treatment of the outer protective pipe in the half-tile repair area.

[0050] Figure 9 This is a schematic diagram of the longitudinal seam extrusion welding of the outer protective pipe in the half-tile repair area.

[0051] Figure 10 This is a schematic diagram showing the completion of longitudinal seam extrusion welding of the outer protective pipe in the half-tile repair area.

[0052] Figure 11 This is a schematic diagram showing the completion of the installation of the outer protective pipe and the longitudinal seam welding in the repair area of ​​all half-tiles within the segment.

[0053] Figure 12 This is a schematic diagram of the installation of the first repair area's outer protective pipe electrofusion mesh belt.

[0054] Figure 13 This is a schematic diagram of the installation and fixing of the outer sleeve in the joint area.

[0055] Figure 14 This is a schematic diagram of the auxiliary tooling for circumferential welding of the joint area.

[0056] Figure 15 This is a schematic diagram of the circumferential welding of the outer sleeve in the joint area.

[0057] Figure 16 This is a schematic diagram of the beveling treatment for the longitudinal butt joint of the outer sleeve in the patching area.

[0058] Figure 17 This is a schematic diagram of the longitudinal butt joint extrusion welding of the outer sleeve in the patching area.

[0059] Figure 18 This is a schematic diagram showing the completion of the longitudinal butt joint welding of the outer sleeve in the patching area.

[0060] Figure 19 This is a schematic diagram showing the installation and welding of the outer sleeve in the remaining repair areas within the repair section.

[0061] Figure 20 This is a schematic diagram of opening the airtightness test hole for the airtightness test.

[0062] Figure 21 This is a schematic diagram of the entire airtightness test.

[0063] Figure 22 This is a schematic diagram of the foaming and venting holes created during the filling of the foam insulation layer.

[0064] Figure 23 This is a schematic diagram of high-pressure injection foaming in the cavity of the repair area.

[0065] Figure 24 This is a schematic diagram of hot-melt welding filling of foamed pores.

[0066] Figure 25 This is a schematic diagram of the structure of the foam hole weld plug.

[0067] Figure 26 This is a cross-sectional view of the foamed hole plug.

[0068] Figure 27 This is a schematic diagram illustrating the completion of the segmented repair operation of the present invention.

[0069] In the diagram: 1. Medium conveying pipeline; 2. Original polyurethane insulation layer; 3. Original outer insulation pipe; 4. Supporting and positioning tile; 5. Outer insulation pipe for the tile repair area; 6. Bundling and tightening strap; 7. Beveling machine; 8. Longitudinal butt joint of the outer insulation pipe for the tile repair area; 9. Manual extrusion welding machine; 10. Longitudinal open seam weld of the outer insulation pipe for the tile repair area; 11. Electrofusion mesh belt; 12. Electrofusion mesh belt end; 13. Outer sleeve of the repair area; 14. Electrofusion welding equipment tooling; 15. Electrofusion welding output line; 16. Electrofusion welding machine; 17. Longitudinal weld of the outer sleeve of the repair area; 18. Air tightness test opening; 19. Air tightness test gauge device; 20. Compressed air supply pipe; 21. Foaming hole; 22. Foaming machine injection head; 23. Exhaust plug. Detailed Implementation

[0070] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0071] A method for repairing in-situ insulation layers of district heating / cooling pipelines includes: removing damaged insulation layers, installing supporting and positioning tiles, installing outer protective pipes in the repair area between tiles, installing outer sleeves in the patching area, and performing sectional injection foaming of the repair section and welding and sealing of the foaming holes; specifically including:

[0072] 1) such as Figures 3-5 As shown, the damaged insulation layer is removed to expose the medium conveying pipe 1. The support positioning tile 4 is installed on the medium conveying pipe 1 in sections. The installation method is: two semi-circular support positioning tiles 4 are fitted together on the medium conveying pipe 1.

[0073] like Figure 1 , Figure 2 As shown, the outer diameter of the support and positioning tile 4 has two radii, R2 and R3. The height difference between the two radii R2 and R3 is consistent with the thickness of the outer protective tube 5 in the tile repair area. The outer protective tube 5 in the tile repair area is fitted onto the end with the smaller radius R2. The support and positioning tile 4 is made of polyurethane.

[0074] 2) See Figures 6-10 The outer protective pipe 5 of the tile repair area is wrapped around and installed between two adjacent sets of support positioning tiles 4. The two ends of the outer protective pipe 5 of the tile repair area overlap with the support positioning tiles 4 and are tied and fixed. The longitudinal butt joint 8 of the outer protective pipe 5 of the tile repair area on one side is welded and sealed.

[0075] The two ends of the outer protective pipe 5 in the tile repair area are tightened and fixed by the binding and tightening straps 6. Then, the longitudinal joint between the binding and tightening straps 6 is beveled, and the bevel is a U-shaped bevel. Hot melt filler is welded at the bevel. After the binding and tightening straps 6 are removed, the longitudinal joints at both ends of the outer protective pipe 5 in the tile repair area are welded and sealed in the same way.

[0076] When the number of outer protective pipes 5 installed in the tile repair area exceeds one section, the outer protective pipes 5 in the tile repair area are installed at intervals between the supporting and positioning tiles 4 (see...). Figure 11 ); the outer protective pipe 5 of the tile repair area is made of high-density polyethylene.

[0077] 3) such as Figure 12 As shown, an electrothermal mesh belt 11 is wrapped around the original insulation outer protective pipe 3 and the outer protective pipe 5 of the tile repair area. The electrothermal mesh belt 11 of the original insulation outer protective pipe 3 is wrapped at one end close to the repair area, while the electrothermal mesh belt of the outer protective pipe 5 of the tile repair area is wrapped at both ends of the outer protective pipe 5 of the tile repair area.

[0078] 4) such as Figure 13 As shown, in one embodiment, the number of outer protective pipes 5 in the tile repair area is more than one section. The outer outer pipe 13 of the repair area is installed around the adjacent outer protective pipes 5 in the tile repair area and between the original insulation outer protective pipe 3 and the outer protective pipe 5 in the tile repair area. The two ends of the outer outer pipe 13 of the repair area overlap the outside of the electrothermal mesh belt 11 and are fixed by the binding fastening strap 6.

[0079] In another embodiment of the present invention, the number of outer protective tubes 5 installed in the tile repair area is one section. The outer outer tube 13 of the repair area is installed around the original insulation outer protective tube 3 and the outer outer protective tube 5 of the tile repair area. The two ends of the outer outer tube 13 of the repair area overlap the outside of the electrothermal mesh belt 11 and are fixed by the binding tight strap 6.

[0080] The outer sleeve 13 of the joint area is made of high-density polyethylene; the end 12 of the electrofusion mesh belt needs to remain on the outside for connection with the electrofusion welding equipment.

[0081] 5) such as Figure 14 , Figure 15 As shown, the electrothermal welding machine 16 is used to weld the electrothermal welding mesh belt 11 to the outer protective pipe 5 of the tile repair area and the outer sleeve 13 of the joint area, or the original insulation outer protective pipe 3 and the outer sleeve 13 of the joint area, in a circumferential welding seal.

[0082] 6) See Figures 16-18 The longitudinal butt joint on one side of the outer sleeve 13 in the patching area is welded and sealed.

[0083] After removing the strapping and electrofusion welding equipment, the longitudinal butt joint on one side of the outer sleeve 13 in the joint area is beveled. The bevel is a U-shaped bevel, and the thermofusion filler is welded at the bevel.

[0084] Figure 19 This diagram illustrates the installation of outer protective pipes 5 in all repair sections within a repair section when the number of outer protective pipes 5 installed in the repair section exceeds one section.

[0085] 7) See Figures 20-21An overall airtightness test is conducted by injecting compressed air into the inner cavity through drilling to check for leaks in the welds.

[0086] 8) See Figures 22-24 By developing foam holes 21 on the outer protective tube 5 of the tile repair area and the outer sleeve 13 of the repair area, foaming material is injected into the inner cavity of the outer protective tube 5 of the tile repair area and the outer sleeve 13 of the repair area, and then the foam holes 21 are sealed. Figure 25 The outer protective pipe after repair.

[0087] At least two holes are drilled on the outer protective pipe 5 of the tile repair area and the outer sleeve 13 of the patching area as grouting holes and foaming venting holes respectively. Foaming material is injected into the outer protective pipe 5 of the tile repair area and the outer sleeve 5 of the patching area through the grouting holes respectively. Then the grouting holes and foaming venting holes are sealed by hot-melt welding.

[0088] The present invention can also place an alarm line in the inner cavity before the outer protective pipe in the repair area between the sets of tiles and the outer outer pipe in the joint area, providing basic conditions for the installation of a pipeline leakage monitoring system.

[0089] A repair structure for an in-situ insulation layer repair method for district heating / cooling pipelines includes a support positioning tile 4, an outer protective pipe 5 for the inter-tile repair area, an outer sleeve 13 for the patching area, an electrofusion mesh belt 11, and a foam layer. The support positioning tile 4 is installed in sections on the medium conveying pipeline 1. The support positioning tile 4 has a semi-circular structure and is fitted onto the medium conveying pipeline 1. The outer diameter of the support positioning tile 4 has two radii, and the height difference between the two radii is consistent with the thickness of the outer protective pipe 5 for the inter-tile repair area. The outer protective pipe 5 for the inter-tile repair area is fitted between two adjacent support positioning tiles 4, and the two ends of the outer protective pipe 5 overlap the smaller radius end of the support positioning tile 4.

[0090] When the number of outer protective pipes 5 installed in the tile repair area is more than one section, the outer protective pipes 5 in the tile repair area are installed at intervals between the supporting and positioning tiles 4.

[0091] The outer sleeve 13 of the repair area is installed between the outer protective sleeves 5 of the adjacent tile repair area and between the original insulation outer protective sleeve 3 and the outer protective sleeve 4 of the tile repair area. The overlapping outer protective sleeve 4 of the tile repair area and the outer sleeve 13 of the repair area are sealed by welding with an electrofusion mesh belt 11. The overlapping original insulation outer protective sleeve 3 and the outer sleeve 13 of the repair area are sealed by welding with an electrofusion mesh belt 11.

[0092] A foam layer is filled between the outer protective pipe 5 in the tile repair area, the outer sleeve 13 in the joint area and the medium conveying pipeline 1;

[0093] The longitudinal joint of the outer protective pipe 5 in the tile repair area and the outer sleeve 13 in the patching area is welded and sealed.

[0094] The repair operation process of this invention includes earthwork excavation and removal of the damaged insulation layer, installation of supporting positioning tiles, installation of outer protective pipe in the repair area between tiles, longitudinal joint beveling treatment and extrusion welding, installation and fixing of electrofusion mesh belt for circumferential welds, installation and fixing of outer sleeve in the repair area, fully automatic electrofusion welding of circumferential welds, longitudinal joint beveling treatment and extrusion welding of outer sleeve in the repair area, overall air tightness test of the repair section, partial injection foaming of the repair section and welding and sealing of foam holes.

[0095] Earthwork excavation and damaged insulation layer removal involve removing the backfill soil within the damaged repair section to expose the pipeline to be repaired, and removing the damaged outer protective pipe and insulation layer. The excavation length of the repair section is limited by the safe span of the pipeline to be repaired, and the excavation length should not exceed the safe span of the pipeline to be repaired.

[0096] Support positioning installation is the process of positioning and temporarily fixing the support positioning tiles according to the installation spacing determined by the width of the high-density polyethylene sheet used for repair.

[0097] The installation of the outer protective pipe in the tile repair area, the longitudinal joint beveling treatment and the extrusion welding are the processes of installing high-density polyethylene sheets around the adjacent two sets of positioning tiles, using the limiting surface of the adjacent positioning tiles as the boundary, tightening and fixing them with a strapping type, performing beveling and surface treatment, and then welding the joint.

[0098] The length of the outer protective pipe in the tile repair area can be adjusted on-site as needed to ensure that the edge of the plate is butt-jointed along the pipe axis after installation and fixation, or to leave a 2-3mm butt joint gap. The longitudinal joint beveling is performed using a beveling machine to create a U-shaped beveling along the butt joint of the high-density polyethylene outer protective pipe, with the bottom of the U-shape reaching the inner surface of the outer protective pipe. After beveling, a scraper is used to remove the surface oxide layer from the bevel edge of the outer protective pipe within 30mm. Extrusion welding is performed using an extrusion welding machine with automatic temperature control to perform hot-melt filler welding along the longitudinal butt weld seam into the bevel area. The welding wire used for extrusion welding is a 4mm diameter circular cross-section wire, and the wire material is the same as that of the outer protective pipe.

[0099] The extrusion welding process begins with welding the joint between the two tension bands. After natural cooling, the tension bands are removed, and the bevel and surface of the area covered by the tension bands are treated and extrusion welding is performed on the covered area. After the extrusion weld at the area covered by the tension bands has naturally cooled, a flap wheel is used to grind the weld surface smooth and flush with the outer surface of the outer sheath.

[0100] The installation and fixing of the electrofusion mesh belt for circumferential welds is the process of fixing the electrofusion mesh belt to the end surface of the original polyethylene outer protective pipe and / or the end surface of the outer protective pipe in the inter-tile repair area according to the positioning requirements of the electrofusion mesh belt installation position.

[0101] The electrofusion mesh belt is fixed to the end surface of the original insulation outer protective pipe and the end surface of the outer protective pipe in the half-tile repair area using staples. A reasonable length is reserved at the end of the electrofusion mesh belt.

[0102] The installation and fixing of the outer sleeve in the joint area involves cutting the required high-density polyethylene sheet to an appropriate length, centering it around the outside of the two high-density polyethylene pipe ends, evenly covering it with electrofusion mesh tape, and then securing it with a binding strap. The binding strap should be approximately 150mm away from the end face of the outer sleeve in the joint area.

[0103] The fully automated electrofusion welding of circumferential welds is a process of hot-melt welding between the repair outer sleeve and the connected high-density polyethylene outer sheath using the TSC 6.0 PRO fully automated high-density polyethylene welding equipment.

[0104] The TSC 6.0 PRO fully automatic high-density polyethylene welding equipment consists of two parts: an electrofusion welding fixture 14 and an electrofusion welding machine 16. The electrofusion welding fixture 14 and the electrofusion welding machine 16 are electrically connected via an electrofusion welding output line 15. The electrofusion welding fixture 14 is installed on both ends of the outer sleeve of the patching area. The tightening strap on the fixture is aligned with the center line of the electrofusion mesh belt to position it. The tightening device is used to tighten the tightening strap until the set torque is reached, ensuring that there is no obvious gap between the edge of the patching outer sleeve and the connected high-density polyethylene outer sheath. The contact-type pressure feet on the electrofusion welding fixture 14 are connected to the end 12 of the electrofusion mesh belt. The TSC 6.0 PRO can automatically complete the circumferential thermofusion sealing weld between the patching outer sleeve and the connected high-density polyethylene outer sheath.

[0105] The longitudinal joint beveling of the outer sleeve in the joint area is treated by using a beveling machine to create a U-shaped bevel along the butt joint of the outer sleeve in the joint area. The dimensions of the U-shaped bevel are determined according to the beveling requirements of the extrusion welding process. The beveling machine is a bakelite milling machine equipped with a deep round bottom milling cutter. After the beveling is completed, the oxide layer on the surface of the outer sleeve within 20mm on both sides of the bevel edge should be polished with sandpaper or a scraper.

[0106] The longitudinal seam extrusion welding of the outer sleeve in the joint area is a process in which a manual extrusion welding machine with automatic temperature control is used to weld filler along the butt joint of the outer sleeve, with a U-shaped bevel as the constraint. The welding wire used in the longitudinal seam extrusion welding process of the outer sleeve in the joint area is a high-density polyethylene welding wire with the same material parameters and model as the high-density polyethylene outer sleeve, and the diameter of the welding wire is 4mm.

[0107] The overall airtightness test for the repaired section is conducted as follows: After completing the welding work on the joint area of ​​all repaired sections, allow all welds to cool naturally to ambient temperature. Then, create an airtightness test opening at the top (12 o'clock position) of one joint area. The opening size must meet the process dimensional requirements. Using this opening, fix the airtightness test gauge and inject compressed air into the cavity between the high-density polyethylene outer sheath and the steel pipe, maintaining the internal pressure at 0.2 Bar. Spray soapy water onto all welds of the high-density polyethylene outer sheath and outer protective pipe to check for leaks and ensure no pressure drop in the internal cavity. The pressure holding time for the airtightness test should be no less than 2 minutes.

[0108] Repairing segmented and partial injection foaming involves injecting foaming material into each repair area and tile repair area to complete the internal cavity insulation foaming process within the repair area.

[0109] Two foam vent holes are made at the top inner cavity of the outer protective tube in each tile repair area and the outer sleeve in each patching area, corresponding to the 12 o'clock position. The diameter of the vent holes must meet the process dimensional requirements. A high-pressure foaming machine is used to mix the insulation foam material and inject the fully mixed foam material into the inner cavity of the tile repair and patching areas. After the foam material is injected into the foaming cavity, the vent holes must be sealed immediately with a special vent plug 23. The special vent plug 23 has an anti-detachment structure and a small central vent hole (such as...). Figure 25 , Figure 26 (As shown). The amount of foaming material used must meet the foaming process requirements. Foaming is carried out in two batches: first, the foaming of all joint areas is completed sequentially, and then the foaming of each inter-tile repair area is completed sequentially. After foaming is completed, the foaming holes and pipe surfaces are cleaned.

[0110] The foamed pore welding and plugging process utilizes specialized, matching high-density polyethylene plugs that meet the process dimensions and material requirements. The plugs are then heat-fused to the cleaned foamed pores using a hot-melt welding method. After all the foamed pore heat-melt welding and plugging is completed, the welded area is allowed to cool naturally to ambient temperature. The plug surface and surrounding material are then polished. Finally, a manual extrusion welding machine with automatic temperature control is used to perform an extrusion-type covering and reinforcement welding on the treated surface and surrounding material of the foamed pore heat-melt plug. See [link / details]. Figure 25 The replacement and repair work of the in-situ insulation layer of the steel pipes in the repair section has been completed.

Claims

1. A method for repairing in-situ the thermal insulation of a district heating / cooling pipe, characterized in that, This includes the installation of supporting positioning tiles, the installation of outer protective pipes in the tile repair area, the installation of outer sleeves in the patching area, the sectional injection and foaming of the repair section, and the welding and sealing of the foaming holes; specifically including: 1) Install the support and positioning tiles in sections on the medium conveying pipeline. The installation method is: two semi-circular support and positioning tiles are fitted together on the medium conveying pipeline. 2) Wrap the outer protective pipe of the tile repair area around and install it between the two adjacent sets of support positioning tiles. The two ends of the outer protective pipe of the tile repair area overlap with the support positioning tiles and are tied and fixed. Weld and seal the longitudinal butt joint on one side of the outer protective pipe of the tile repair area. When the number of outer protective pipes installed in the tile repair area is more than one section, the outer protective pipes in the tile repair area are installed at intervals between the supporting and positioning tiles; 3) Wrap electrofusion mesh tape around the original insulation outer protective pipe and the outer protective pipe of the tile repair area. The electrofusion mesh tape of the original insulation outer protective pipe is wrapped at one end close to the repair area, and the electrofusion mesh tape of the outer protective pipe of the tile repair area is wrapped at both ends of the outer protective pipe of the tile repair area. 4) Install a patching outer sleeve around the outer protective pipes of the adjacent tile repair area and / or between the original insulation outer protective pipe and the outer protective pipe of the tile repair area. The two ends of the patching outer sleeve overlap the outside of the electrofusion mesh belt and are tied and fixed. 5) Use an electrothermal welding machine to weld the electrothermal mesh belt to the outer protective pipe of the repair area and the outer sleeve of the patching area between the upper and lower tiles, or the original insulation outer protective pipe and the outer sleeve of the patching area in a circumferential weld to seal them. 6) Weld and seal the longitudinal butt joint on one side of the outer sleeve in the patching area; 7) By creating foam holes in the outer protective pipe of the tile repair area and the outer sleeve of the joint repair area, foaming material is injected into the outer protective pipe of the tile repair area and the outer sleeve of the joint repair area, and then the foam holes are sealed. The outer diameter of the supporting positioning tile has two radii, and the height difference between the two radii is consistent with the thickness of the outer protective tube of the tile repair area. The outer protective tube of the tile repair area is fitted onto the end with the smaller radius.

2. The method for repairing in-situ insulation layer of a district heating / cooling pipeline according to claim 1, characterized in that, The supporting positioning tile is made of polyurethane.

3. The method of claim 1, wherein the in-situ repair of the thermal / cooling pipe in the district heating / cooling system is performed by using a thermal / cooling pipe in-situ repair device. The outer protective pipe of the tile repair area is made of high-density polyethylene; the outer sleeve of the joint repair area is made of high-density polyethylene.

4. The method of claim 1, wherein the in-situ repair of the thermal / cooling pipe in the district heating / cooling system is performed by using a thermal / cooling pipe in-situ repair device. Before the outer protective tube in the repair area between the tiles and the outer sleeve in the joint area, place an alarm line inside the cavity.

5. The method of claim 1, wherein the in-situ repair of the thermal / cooling pipe in the district heating / cooling system is performed by using a thermal / cooling pipe in-situ repair device. In step 2), the two ends of the outer protective pipe of the tile repair area are tightened and fixed with a binding strap. Then, the longitudinal joint between the binding straps is beveled and hot melt filler is welded at the bevel. After the binding strap is removed, the longitudinal joints at both ends of the outer protective pipe of the tile repair area are welded and sealed in the same way.

6. The method of claim 1, wherein the method further comprises: In step 6), the longitudinal butt joint on one side of the outer sleeve in the joint area is beveled, and hot melt filler welding is performed at the bevel.

7. A method of repairing an in-situ thermal / cooling pipe insulation according to claim 5 or 6, characterized in that, The bevel is a U-shaped bevel.

8. A method for repairing in-situ insulation layers of district heating / cooling pipelines according to claim 1, characterized in that, Before applying thermal insulation foam to the inner cavity of the outer protective pipe in the repair area and the outer sleeve in the joint area, an overall airtightness test is conducted. Compressed air is injected into the inner cavity by drilling holes to check for leaks in the weld.

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