Polyisocyanurate cold insulation pipeline and on-site joint coating structure thereof

Abstract

The utility model discloses a polyisocyanurate cold insulation pipeline and an on-site joint coating structure thereof. The cold insulation pipeline comprises a working pipe, an isolating layer, a sealing layer, a cold insulation structure layer and an outer protective layer, wherein the isolating layer, the sealing layer, the cold insulation structure layer and the outer protective layer are sequentially arranged on the outer wall of the working pipe in a sleeving mode from inside to outside. The cold insulation structure layer comprises a first cold insulation layer, a primary moisture-proof layer, a second cold insulation layer, a secondary moisture-proof layer, a third cold insulation layer and a main moisture-proof layer which are sequentially arranged from inside to outside; the field joint coating structure comprises a joint coating isolation layer, a polyisocyanurate pipe shell set, a joint coating main damp-proof layer and a joint coating outer protection layer which are sequentially arranged outside the joint coating position after the two cold insulation pipelines are in butt joint in a sleeving mode from inside to outside. The cold insulation layer of the cold insulation pipeline product is uniform and stable in structure and few in joints, the field joint coating structure is further optimized, the overall cold insulation effect of the pipeline is greatly improved, and the service life of the pipeline is greatly prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of cold-insulation transportation of ultra-low temperature medium pipelines, and in particular relates to a polyisocyanurate cold-insulation pipeline and an on-site patching structure thereof. Background Art

[0002] Natural gas is a high-quality, efficient and convenient clean energy and chemical raw material. Due to the limited domestic natural gas resources, in recent years, the gap between supply and demand has been solved by importing a large amount of liquefied natural gas (LNG). In order to solve the problems of receiving, storing and exporting LNG by sea, my country has built a large number of LNG receiving stations in coastal areas. However, since LNG needs to be stored and transported at ultra-low temperatures (-165℃), the cold preservation of LNG receiving station pipelines, storage tanks and other storage and transportation facilities has become a problem that the industry must face. The quality of its cold preservation has a vital impact on transportation efficiency and safe production.

[0003] Specifically, for the cold insulation of pipelines at LNG receiving stations, modified polyisocyanurate (PIR), foam glass (FG), elastic foam (FEF) and other materials with good low-temperature resistance are used. Based on this, a variety of construction processes have been developed, which are briefly introduced as follows.

[0004] 1) Foam glass cold insulation process: This process is to pre-cut the foam glass block material into a half-tile shape, splice and install it on the outer surface of the steel pipe, and then fix it with stainless steel strapping. Then install a reinforced mesh cloth on the outside of the foam glass, apply a mastic moisture-proof layer, and finally install a metal outer protective layer on the outside.

[0005] 2) PIR cold insulation process: This process is to pre-cut the PIR block material into half-tile shapes, splice and install them on the outer surface of the steel pipe and then fix them with stainless steel strapping tape. PAP air barrier layers need to be installed between the PIR half-tile layers. Then install reinforced mesh cloth on the outside of the PIR, apply mastic moisture-proof layer, and finally install a metal outer protective layer on the outside.

[0006] 3) PIR+foam glass composite cold insulation process: This process combines the advantages of foam glass and PIR cold insulation. The inner layer of the pipeline adopts the PIR half-tile installation process, the outer layer is installed with foam glass half-tile, and then the reinforced mesh cloth is installed on the outside of the foam glass, and the mastic moisture-proof layer is applied, and finally the metal outer protective layer is installed on the outside.

[0007] 4) Flexible insulation elastic foam process: Use rubber-based modified closed-cell elastic foam coil, manually wrap it on the outer surface of the pipe, and install a metal outer protective layer on the outside.

[0008] From the above content, it can be seen that no matter which thermal insulation / cold insulation material is used, the construction process generally requires on-site assembly, and its shortcomings are mainly reflected in the following aspects:

[0009] 1) On-site cold insulation construction is in the late stage of LNG receiving station project construction, and the project schedule is usually very tight. However, the traditional on-site cold insulation process is very complicated, with many construction steps and a long construction period, which slows down the overall construction period;

[0010] 2) The traditional half-tile insulation system requires a large number of materials of different specifications, such as insulation half-tile pipe shells, insulation coils, polyurethane casting foam composite materials, moisture-proof layers, low-temperature glue, sealants, fasteners, outer protective layers, cold-insulation pipe supports, etc. to be transported to the project site, which makes on-site management very difficult;

[0011] 3) On-site cold insulation construction technology is very dependent on labor, with high labor costs and difficulty in construction quality control;

[0012] 4) Prefabricated PIR and foam glass shells are made by cutting large pieces of foam, with high loss rates during cutting, storage and transportation, low overall material utilization (PIR molding utilization rate is 55-60%, foam glass molding utilization rate is 70%), and high waste disposal costs;

[0013] 5) There is usually a part of weld excess height at the weld of steel pipelines. If the prefabricated shell is assembled on site, there will be a certain gap between the outer surface of the pipeline and the shell, which may cause condensation and ice formation. In addition, there are many joints on the axis of the shell. If the joints are not properly sealed, it is easy to cause water vapor to penetrate during operation, resulting in condensation and ice formation, resulting in loss of cold energy and damage to the cold insulation layer.

[0014] 6) The outer protective layer is made of steel or aluminum plates, which are prone to corrosion and riveting failure, causing water to enter the cold insulation layer and condensation to form ice, resulting in the failure of the cold insulation layer.

[0015] In order to solve the above problems and improve the quality level and production efficiency of LNG cold-insulated pipelines, it is necessary to make necessary improvements to the traditional pipeline cold-insulation construction process to meet the increasingly high requirements of LNG receiving stations for pipeline cold-insulation. The mainstream approach is to use pre-insulation technology to complete most of the pipeline cold-insulation construction in the factory's insulation / cold-insulation production line. In this regard, relevant units and companies have carried out corresponding research and application practices, but from the available public information, the existing pipeline pre-insulation technology and process still have many shortcomings and have not effectively solved the above-mentioned concerns.

[0016] Chinese patent application number CN202010533963.3 discloses a LNG cryogenic prefabricated cold-insulation pipe and its manufacturing method, wherein the cryogenic prefabricated pipe is composed of a working pipe, a cold-insulation layer and an outer protective layer from the inside to the outside; a moisture-proof layer can be arranged between the working pipe and the cold-insulation layer, a moisture-proof layer is arranged outside each layer of PIR foam, and the outer protective layer is made of ultraviolet hardened fiberglass. The cold-insulation layer involved is made of polyisocyanurate (PIR) material, and the construction method is a proprietary equipment production method (i.e. continuous casting method) and a proprietary mold production method (i.e. mold casting method). This LNG low-temperature prefabricated insulation pipe and its manufacturing method can indeed improve the degree of construction automation, improve the performance of the insulation pipeline, reduce the cold loss of the pipeline, and reduce the total cost. However, there are also certain shortcomings: 1) The insulation layer construction method adopts the continuous pouring method or the mold pouring method, which inevitably has problems such as poor uniformity of the pore structure and holes, affecting the thermal conductivity of the PIR insulation layer; 2) The continuous pouring method requires proprietary equipment, and the mold pouring method requires customization of the corresponding steel mold. The insulation pipeline of the LNG receiving station is usually no more than 2km in length, and the economic efficiency of the pouring method is not advantageous; 3) There is no isolation layer between the working pipe and the insulation layer, and it is only isolated by a 1mm thick PAP aluminum foil moisture-proof layer. This results in a large longitudinal temperature gradient in the first layer of PIR insulation, which is prone to uneven shrinkage, deformation, and damage. 4) No limit blocks are set on the entire 12m length of the working pipe, which will aggravate the damage caused by shrinkage and deformation of the insulation layer to a certain extent. 5) PE film or sealing tape is used on both ends of the prefabricated pipe for moisture-proof and waterproof sealing, and it is not yet certain whether it can meet the requirements of low-temperature service environment.

[0017] Chinese patent application No. CN202110572843.9 discloses a low-temperature cold-insulation pipe structure prefabricated by a spray winding method and a manufacturing method thereof, wherein a fixing ring is provided on the middle section of the working pipe, and the working pipes at both ends of the fixing ring are wrapped with a glass fiber needle-punched felt isolation layer, and the isolation layer is wrapped with a cold-insulation base layer whose thickness matches the fixing ring, and an air-blocking layer is wrapped on the surface of the cold-insulation base layer and the fixing ring, and several layers of cold-insulation layers are wrapped on the air-blocking layer, and air-blocking layers are added between adjacent cold-insulation layers, and an outer protective layer is wrapped on the surface of the outermost cold-insulation layer. The cold insulation layer of the low-temperature cold insulation pipe adopts the spraying PIR / PUR process for cold insulation construction, and adopts (12um+25um+12um) self-adhesive PAP composite aluminum film as the air barrier layer, which solves the problems existing in the casting PIR / PUR process, but there are still certain shortcomings: 1) The PIR / PUR cold insulation layer is directly sprayed on the outer surface of the glass fiber needle felt insulation layer, and the air contained in the needle felt expands after heating and cannot be discharged, resulting in hollowing between the insulation layer and the cold insulation layer; 2) The surface of the cold insulation layer prepared by the spraying PIR / PUR process has a low surface flatness, and the PAP composite aluminum film is directly wrapped around the surface of the cold insulation layer, and there will inevitably be gaps and holes between the two, which is prone to condensation and ice formation in the later stage, resulting in cold energy loss; 3) It is not clear whether the self-adhesive PAP composite aluminum film still has good bonding properties and waterproof and moisture-proof properties under low-temperature service environment.

[0018] Chinese patent application number CN202021080229.8 discloses a new type of cold-insulation structure prefabricated pipe, including: a wear-resistant layer, at least one PIR cold-insulation layer, at least one moisture-proof layer, a fire-proof layer, a main moisture-proof layer and an outer protective layer. A PAP aluminum foil wear-resistant layer is set on the outside of the working pipe to effectively reduce the friction between the cold-insulation layer and the shrinkage of the working pipe under ultra-low temperature conditions, and ensure that the cold-insulation layer is not damaged and cracked; the cold-insulation layer is a continuous foaming PIR material; SiO2 aerogel felt is set as a fire-proof layer to meet the Class A non-combustible requirements; STI5000 is used as the main moisture-proof layer, and the aluminum-plated steel plate is the outer protective layer. This cold-insulation pipe structure can shorten the construction period of the cold-insulation pipe and extend the service life of the cold-insulation structure, but the wear-resistant layer of the cold-insulation structure only uses one layer of PAP aluminum foil, which cannot completely slow down the tangential damage between the working pipe and the cold-insulation pipe; in addition, the aluminum-plated steel plate is the outer protective layer, which is prone to corrosion problems.

[0019] Chinese patent application number CN202023122999.7 discloses a cold-insulation pipe structure with glass fiber cloth resin as the outer sheath, including a cold-insulation pipe body, wherein the cold-insulation pipe body is provided with a needle-punched fiber blanket layer, a first sprayed PIR layer, a first glass fiber cloth layer, a second sprayed PIR layer, a second glass fiber cloth layer, a third sprayed PIR layer, and a fiberglass layer from the inside to the outside; wherein the end faces of the first, second, and third sprayed PIR layers are provided with end face air-blocking layers. This cold insulation structure is similar to the above-mentioned patent, and also has the following shortcomings: 1) The PIR / PUR cold insulation layer is directly sprayed on the outer surface of the needle-punched fiber blanket layer. The air contained in the needle-punched fiber blanket layer expands after heating and cannot be discharged, resulting in hollows between the needle-punched fiber blanket layer and the cold insulation layer; 2) The aluminum-plated steel plate is the outer protective layer, which is prone to corrosion problems; 3) The surface of the cold insulation layer prepared by the PIR spraying process is not very smooth, and the glass fiber cloth is directly wrapped around the surface of the cold insulation layer. There will inevitably be gaps and holes between the two, which will easily cause condensation and ice formation in the later stage, resulting in loss of cold energy.

[0020] Chinese patent application number CN202120873329.4 discloses a prefabricated cold-insulation pipe for transporting low-temperature media, including a pipe. Except for the pipe heads at both ends of the pipe, the other parts of the pipe are sequentially provided with glass fiber needle felt, a first polyurethane spray cold-insulation layer, a first aluminum foil moisture-proof layer, a second polyurethane spray cold-insulation layer, a second aluminum foil moisture-proof layer, a third polyurethane spray cold-insulation layer and a glass fiber reinforced epoxy resin layer from the inside to the outside. Steps are provided at both ends of the pipe, and a vapor-blocking sealing layer is brushed on the steps. In this cold-insulation pipe structure, the PIR / PUR cold-insulation layer is directly sprayed on the outer surface of the glass fiber needle felt layer. The air contained in the needle felt expands after being heated and cannot be discharged, resulting in hollowing between the needle felt layer and the cold-insulation layer.

[0021] It can be seen that the above-mentioned Chinese patent application has carried out some exploration and practice in the structure and construction process of the cold insulation pipe, but there are still some common problems in the cold insulation pipe structure design and on-site construction:

[0022] 1) Most cold-insulation structures are equipped with a glass fiber needle felt insulation layer, but the subsequent construction process is to directly spray / pour PIR on the outer surface of the insulation layer. During the construction process, the air contained in the insulation layer expands due to heat and cannot be discharged, which easily leads to hollowing between the insulation layer and the cold-insulation layer;

[0023] 2) The cold insulation layer prepared by the spraying / continuous pouring PIR process has a low surface flatness. The subsequent process is to directly wrap the secondary moisture-proof layer (self-adhesive PAP composite aluminum film) onto the surface of the cold insulation layer. There will inevitably be a gap between the two, and condensation and ice are likely to occur during the operation of the pipeline, resulting in cold energy loss;

[0024] 3) The main moisture barrier layer usually uses self-adhesive PAP composite aluminum film, and the bonding performance in low-temperature service environment cannot be fully guaranteed. There is no clear solution for the material selection and installation process of the vapor barrier layer;

[0025] 4) The patching position is a weak link in terms of cold preservation and moisture resistance, and no targeted design has been made for the structure and process of on-site patching.

[0026] The existence of the above problems affects the overall application effect of pipeline pre-insulation technology. In order to further improve the prefabrication process and on-site application effect of LNG receiving station cold-insulated pipelines, a better technical solution is needed. Utility Model Content

[0027] The utility model is proposed to solve the problems existing in the prior art, and its purpose is to provide a polyisocyanurate cold-insulated pipe and an on-site patching structure thereof.

[0028] The utility model is realized by the following technical solutions:

[0029] A polyisocyanurate cold-insulation pipe comprises a working pipe and an isolation layer, a sealing layer, a cold-insulation structure layer and an outer protective layer which are sequentially sleeved on the outer wall of the working pipe from the inside to the outside; the cold-insulation structure layer comprises a first cold-insulation layer, a secondary moisture-proof layer, a second cold-insulation layer, a secondary moisture-proof layer, a third cold-insulation layer and a main moisture-proof layer which are sequentially arranged from the inside to the outside.

[0030] In the above technical solution, a limiting ring is provided on the outer wall of the middle portion of the working tube.

[0031] In the above technical solution, the isolation layer completely covers the outer wall of the working tube; the sealing layer completely covers the isolation layer;

[0032] In the above technical solution, the axial lengths of the first cold insulation layer, the second cold insulation layer and the third cold insulation layer decrease in sequence, and the ends of the three are arranged in steps, and the steps are arranged in arithmetic steps.

[0033] In the above technical solution, the primary moisture-proof layer completely covers the outside of the first cold insulation layer, and the two are bonded; the secondary moisture-proof layer completely covers the outside of the second cold insulation layer, and the two are bonded; the main moisture-proof layer completely covers the outside of the third cold insulation layer, and the two are bonded; the outer protective layer completely covers the main moisture-proof layer.

[0034] In the above technical solution, vapor resistance layers are provided at the ends of the first, second and third cold insulation layers, the outside of the primary moisture-proof layer not covering the second cold insulation layer and the outside of the secondary moisture-proof layer not covering the third cold insulation layer.

[0035] In the above technical solution, the vapor resistance layer is a composite layer structure, which includes multiple layers of rubber coatings and mesh cloth layers arranged between adjacent rubber coatings.

[0036] In the above technical solution, both ends of the working pipe extend out of the cold-insulating structure layer; waterproof caps are arranged at both ends of the cold-insulating structure layer, and the working pipe extends out of the waterproof caps.

[0037] A field patching structure for a polyisocyanurate cold-insulated pipe comprises a patching isolation layer, a polyisocyanurate pipe shell group, a patching main moisture-proof layer and a patching outer protective layer, which are sequentially sleeved from the inside to the outside on the outside of the patching position after two cold-insulated pipes are butt-jointed; the two ends of the patching isolation layer are overlapped on the outside of the closed layers of two sections of working pipes; the polyisocyanurate pipe shell group is fixed to the patching position by aluminum foil tape; the patching main moisture-proof layer is bonded to the outer wall of the polyisocyanurate pipe shell group.

[0038] In the above technical solution, the polyisocyanurate tube shell group includes three layers of polyisocyanurate tube shells, one end of each layer of polyisocyanurate tube shell is tightly attached to the end of the cold insulation pipe on one side, and glass wool is arranged between the end of the cold insulation pipe on the other side; adjacent polyisocyanurate tube shells are tightly attached to the cold insulation pipes on the opposite sides.

[0039] The beneficial effects of the utility model are:

[0040] The utility model provides a polyisocyanurate cold-insulated pipe and an on-site patching structure thereof. In the cold-insulated pipe structure, a layer of self-adhesive aluminum foil tape is added as a sealing layer on the outside of the glass fiber felt to completely seal the air contained in the isolation layer to prevent the subsequent spraying of the cold-insulating layer. The air expands due to heat and cannot be discharged, resulting in hollowing between the isolation layer and the cold-insulating layer. During the service of the pipeline, water vapor condenses and freezes at the hollowing position, affecting the cold-insulating effect and the life of the pipeline; the secondary moisture-proof layer is made of PAP composite aluminum-plastic film, which forms a good seal with the cold-insulating layer PIR. Chemical bonding; the main moisture-proof layer uses butyl rubber composite coil, which has certain fluidity and wettability under normal temperature conditions, and can completely fit the PIR material of the cold insulation layer, avoiding gaps and holes between the moisture-proof layer and the cold insulation layer to the greatest extent, and avoiding condensation and icing during the service of the pipeline, which affects the cold insulation effect and pipeline life; at the same time, the main moisture-proof layer has good low-temperature bonding performance, which ensures the stability of the pipeline in a low-temperature service environment; the on-site patching structure design ensures that the thermal insulation and moisture-proof performance of the patching position reaches the same level as the main pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the structure of the polyisocyanurate cold-insulation pipe in the utility model;

[0042] Figure 2 The utility model is a schematic structural diagram of the on-site patching structure of the polyisocyanurate cold-insulated pipeline.

[0043] in:

[0044] 1. Working pipe; 2. Isolation layer; 3. Limiting ring; 4. Sealing layer; 5. First cold insulation layer; 6. Secondary moisture-proof layer; 7. Second cold insulation layer; 8. Secondary moisture-proof layer; 9. Third cold insulation layer; 10. Main moisture-proof layer; 11. Outer protective layer; 12. Vapor resistance layer; 13. Waterproof cap; 14. Patching isolation layer; 15. Polyisocyanurate pipe shell; 16. Glass wool; 17. Patching main moisture-proof layer; 18. Patching outer protective layer.

[0045] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the technical solution of the present utility model, the technical solution of the present utility model will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

[0047] Example 1

[0048] like Figure 1 As shown, a polyisocyanurate cold-insulated pipe comprises a working pipe 1 and an isolation layer 2, a sealing layer 4, a cold-insulating structure layer and an outer protective layer 11 which are sequentially sleeved on the outer wall of the working pipe 1 from the inside to the outside;

[0049] The cold-insulating structure layer includes a first cold-insulating layer 5, a secondary moisture-proof layer 6, a second cold-insulating layer 7, a secondary moisture-proof layer 8, a third cold-insulating layer 9 and a main moisture-proof layer 10 which are arranged in sequence from the inside to the outside;

[0050] The isolation layer 2 completely covers the outer wall of the working tube 1; the sealing layer 4 completely covers the isolation layer 2;

[0051] A limiting ring 3 is arranged on the outer wall of the middle part of the working tube 1. The limiting ring 3 is formed by splicing two semicircular rings. The limiting ring 3 is fixed to the outer wall of the working tube 1 by a low-temperature adhesive. The thickness of the limiting ring 3 is the same as that of the first cold-insulating layer 5. A secondary moisture-proof layer 6 is arranged outside the limiting ring 3, that is, no isolation layer 2 and sealing layer 4 are arranged between the limiting ring 3 and the working tube 1, and the limiting ring is in direct contact with the working tube;

[0052] The axial lengths of the first cold insulation layer 5, the second cold insulation layer 7 and the third cold insulation layer 9 decrease successively, and the ends of the three are arranged in steps, and the steps are arranged in arithmetical steps. Specifically: the end of the first cold insulation layer 5 is spaced 400mm from the end of the working pipe 1, the end of the second cold insulation layer 7 is spaced 450mm from the end of the working pipe 1, and the end of the third cold insulation layer 9 is spaced 500mm from the end of the working pipe 1. Thus, the ends of the three cold insulation layers are in a stepped structure, which is convenient for on-site patching and expansion joint setting.

[0053] The secondary moisture-proof layer 6 completely covers the outside of the first cold-insulating layer 5, and the two are bonded; the secondary moisture-proof layer 8 completely covers the outside of the second cold-insulating layer 7, and the two are bonded; the main moisture-proof layer 10 completely covers the outside of the third cold-insulating layer 9, and the two are bonded; the outer protective layer 11 completely covers the main moisture-proof layer 10

[0054] The ends of the first cold insulation layer 5, the second cold insulation layer 7 and the third cold insulation layer 9, the outside of the secondary moisture-proof layer 6 not covering the second cold insulation layer 7 and the outside of the secondary moisture-proof layer 8 not covering the third cold insulation layer 9 are all provided with a vapor resistance layer 12, that is, the vapor resistance layer 12 covers the exposed area of ​​the cold insulation layer at the pipe end, and the two ends of the outer protective layer 11 are provided with a vapor resistance layer 12, that is, the vapor resistance layer 12 overlaps with the outer protective layer 11, and the overlap length is ≥20mm; the vapor resistance layer 12 on the end face of the first cold insulation layer 5 extends to the outer wall of the working pipe 1, that is, the vapor resistance layer 12 overlaps with the isolation layer 2, and the overlap length is ≥20mm;

[0055] The vapor resistance layer 12 is a composite layer structure, which includes multiple rubber coating layers and mesh cloth layers arranged between adjacent rubber coating layers.

[0056] The axial length of the cold-insulating structure layer is smaller than the axial length of the working tube 1 , that is, both ends of the working tube 1 extend out of the cold-insulating structure.

[0057] Waterproof caps 13 are provided at both ends of the cold-insulating structure, and the working pipe 1 extends out of the waterproof caps 13 .

[0058] The working pipe 1 is a carbon steel pipe, a stainless steel pipe or other permitted pipes.

[0059] The material of the isolation layer 2 is a glass fiber felt coil with a certain elasticity. The thickness of the isolation layer 2 is 6 mm to 10 mm, and the density is 40 kg / m 3 ~60kg / m 3 , thermal conductivity ≤0.030W / (m·K)@23℃; the isolation layer 2 serves to isolate the first cold-insulating layer 5 from the working tube 1, and acts as an elastic buffer layer.

[0060] The limiting ring 3 is bonded to the outer surface of the working tube 1 by a low-temperature adhesive; the limiting ring 3 is made of cast high-density polyurethane foam with a density of ≥200kg / m 3 , compressive strength ≥ 3MPa, thermal conductivity ≤ 0.045W / (m·K)@23℃, bonded to the middle of the working tube by low-temperature adhesive.

[0061] The sealing layer 4 is bonded to the outside of the isolation layer 2, and the material of the sealing layer 4 is a self-adhesive aluminum foil tape with a thickness of 150 μm; the base material of the self-adhesive aluminum foil tape is aluminum foil, and the adhesive layer material is flame-retardant high-temperature acrylic acid; the self-adhesive aluminum foil tape is spirally wound around the outer surface of the isolation layer 2 to completely wrap the isolation layer 2; the adhesive layer of the self-adhesive aluminum foil tape completely seals the isolation layer to prevent the air contained in the isolation layer 2 from being unable to be discharged after being heated and expanded during the subsequent cold insulation layer spraying process, resulting in hollows between the isolation layer 2 and the cold insulation layer.

[0062] The first cold insulation layer 5, the second cold insulation layer 7 and the third cold insulation layer 9 are all made of modified polyisocyanurate (PIR), with a thickness not exceeding 75 mm and a density of 40-60 kg / m 3 ; Thermal conductivity ≤0.024W / (m·K)@23℃; Closed porosity ≥95%; Compressive strength ≥0.2MPa@23℃, ≥0.28MPa@-165℃; Linear expansion coefficient ≤70×10 -6 m / (m·K)@23℃,≤70×10 -6 m / (m·K)@-165℃; oxygen index ≥30, flame retardant grade B1; the first cold insulation layer 5, the second cold insulation layer 7 and the third cold insulation layer 9 are all formed by spraying process, and are formed by spraying and foaming three times by a two-component high-pressure sprayer.

[0063] The material of the first secondary moisture-proof layer 6 and the second secondary moisture-proof layer 8 is PAP composite aluminum-plastic film with a thickness of 135μm-155μm, a surface wetting tension ≥55mN / m, a gas permeability ≤0.1cm3 / (m2·d·atm), and a tensile strength ≥15MPa. The first secondary moisture-proof layer 6 and the second secondary moisture-proof layer 8 are wrapped in a spiral winding manner and bonded to the outer surfaces of the first cold insulation layer 5 and the second cold insulation layer 7, respectively.

[0064] The main moisture-proof layer 10 is made of a butyl rubber composite coil, the front side of which is butyl rubber and the back side is covered with a self-adhesive aluminum foil, with a thickness of 1.5 mm and a width of 1 m, which is coated and bonded to the outer surface of the third cold insulation layer 9 .

[0065] The material of the outer protective layer 11 is UV-hardened fiberglass GRP, which is a coil formed by pre-impregnating glass fiber felt / cloth with solvent-free epoxy resin and epoxy acrylic resin mixed with photosensitizer. The UV-hardened fiberglass used in the outer protective layer has a thickness of ≥2mm and a width of 100mm. It is wrapped on the outer surface of the main moisture-proof layer in a spiral winding manner and cured by ultraviolet light with a wavelength of 365-410nm. After curing, the bending strength is ≥130MPa, the tensile strength is ≥50MPa, and the elongation at break is ≥1%.

[0066] The vapor resistance layer 12 is formed on the steps and step facades of the cold insulation layer at the end of the working pipe by brushing. The rubber coating of the vapor resistance layer 12 is made of a two-component mastic elastic rubber coating. The composite layer structure is formed by first brushing the two-component mastic elastic rubber coating, then covering it with a mesh cloth, and then brushing the mastic elastic rubber coating on the mesh cloth. The total wet film thickness is greater than 1.6 mm.

[0067] The waterproof cap 13 is a polyethylene heat shrinkable end cap, which is in the form of a seamless sleeve before construction, with a thickness of 1.2 mm, and is installed on the end of the working pipe by torch baking.

[0068] The utility model polyisocyanurate cold-insulating pipe is prepared by the following method:

[0069] 1) Wrapping a layer of glass fiber felt coiled material on the working tube 1 as an isolation layer 2, which serves to isolate the first cold insulation layer 5 from the working tube 1 and acts as an elastic buffer layer;

[0070] 2) Install the limit block 3 in the middle of the working tube 1. The material is cast high-density PUR. Use low-temperature adhesive to firmly bond and fix the limit block;

[0071] 3) A layer of self-adhesive aluminum foil tape is wrapped around the outside of the isolation layer 2 as a sealing layer 4. The sealing layer 4 completely wraps and seals the isolation layer 2;

[0072] 4) Spray the first cold-insulating layer 5 made of modified PIR on the outside of the sealing layer 4 by a two-component high-pressure sprayer. While spraying, wrap the first secondary moisture-proof layer 6 made of PAP composite aluminum-plastic film on the outside of the first cold-insulating layer 5;

[0073] 5) Spray the second cold insulation layer 7 made of modified PIR on the outside of the first secondary moisture-proof layer 6 by a two-component high-pressure sprayer. While spraying, wrap the second secondary moisture-proof layer 8 made of PAP composite aluminum-plastic film on the outside of the second cold insulation layer 7;

[0074] 6) Spray the third cold insulation layer 9 made of modified PIR on the outside of the second secondary moisture-proof layer 8 by a two-component high-pressure sprayer. After the third cold insulation layer is sprayed and completely cured, the main moisture-proof layer 10 made of butyl rubber composite coil is coated and pasted on the outside;

[0075] 7) Install an outer protective layer 11 wrapped around the main moisture-proof layer 10, which is made of ultraviolet-cured fiberglass. After installation, it is cured by ultraviolet light;

[0076] 8) Use cutting equipment to process the cold insulation layer at the pipe end, so that the first cold insulation layer 5, the second cold insulation layer 7, and the third cold insulation layer 9 are laid in a right-angle step shape at the pipe end, which is convenient for forming staggered overlap with the cold insulation material at the on-site patching position, thereby reducing the cold loss at the patching position;

[0077] 9) Apply the vapor barrier layer 12 at the pipe end and embed the glass fiber mesh cloth; the vapor barrier layer 12 should cover the exposed area of ​​the cold insulation layer at the pipe end, and the overlap length with the isolation layer 2 and the outer sheath 11 should be ≥ 20mm;

[0078] 10) A temporary waterproof cap 13 is installed at the end of the pipe to prevent water vapor from entering.

[0079] Example 2

[0080] like Figure 2 As shown, a polyisocyanurate cold-insulated pipe on-site patching structure includes a patching isolation layer 14, a polyisocyanurate pipe shell group, a patching main moisture-proof layer 17 and a patching outer protective layer 18, which are sequentially sleeved on the outside of the patching position of two cold-insulated pipes after being butted from the inside to the outside;

[0081] The patch insulation layer 14 is made of the same material as the insulation layer 2. Both ends of the patch insulation layer 14 are overlapped outside the sealing layer 4 of the two sections of the working pipe 1, and the overlap width is ≥10mm.

[0082] The polyisocyanurate tube shell group is fixed to the patching position by aluminum foil tape; the polyisocyanurate tube shell group includes three layers of polyisocyanurate tube shells, one end of each layer of polyisocyanurate tube shell is in close contact with the end of the cold-insulating pipe on one side, and glass wool 16 is arranged between the end of the cold-insulating pipe on the other side; the ends of adjacent polyisocyanurate tube shells are arranged in a staggered manner, that is, adjacent polyisocyanurate tube shells are in close contact with the cold-insulating pipes on the opposite sides;

[0083] The patching main moisture-proof layer 17 is bonded to the outer wall of the polyisocyanurate tube shell assembly, and its material is the same as that of the main moisture-proof layer 10 .

[0084] The material of the patch outer protective layer 18 is the same as that of the outer protective layer 11 .

[0085] The on-site patching structure of the polyisocyanurate cold-insulated pipe of the utility model is prepared by the following method:

[0086] (1) After the butt welding and nondestructive testing of the two working pipes 1 are completed, the waterproof caps 13 at the pipe ends are removed, the outer surface of the working pipe 1 at the patching position is cleaned, and the first cold insulation layer 5, the second cold insulation layer 7, the third cold insulation layer 9, the outer protective layer 11, and the vapor resistance layer 12 at the pipe ends are checked to see whether they are intact.

[0087] (2) Install the patching isolation layer 14 at the patching position, wrap it around the outer surface of the on-site patching position of the working pipe 1 by manual winding, and fix it with tape, overlapping with the isolation layer 2 at the end of the main pipe, and the overlapping width is ≥10mm.

[0088] (3) The polyisocyanurate tube shells 15 are installed in pairs at the on-site patching positions of the working tube 1 and then fixed with aluminum foil tape.

[0089] (4) The polyisocyanurate tube shell 15 is installed in three layers, and the seams between the layers are staggered. The joints between each layer of the polyisocyanurate tube shell 15 and the end of the working tube 1 are filled with glass wool 16; the outermost layer of the polyisocyanurate tube shell 15 is pasted with a main moisture-proof layer 17, and compacted with a roller;

[0090] (5) The patch outer protective layer 18 is installed on the outside of the patch main moisture-proof layer 17 by manual installation, and after the installation is completed, it is cured by ultraviolet light.

[0091] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0092] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0093] The applicant declares that the above is only a specific implementation method of the present utility model, but the protection scope of the present utility model is not limited thereto. The technicians in the relevant technical field should understand that any changes or substitutions that can be easily thought of by the technicians in the relevant technical field within the technical scope disclosed in the present utility model fall within the protection scope and disclosure scope of the present utility model.

Claims

1. A polyisocyanurate cold-insulated pipe, characterized in that: The invention comprises a working tube (1), and an isolation layer (2), a sealing layer (4), a cold-insulating structure layer and an outer protective layer (11) which are sequentially sleeved on the outer wall of the working tube (1) from the inside to the outside; the cold-insulating structure layer comprises a first cold-insulating layer (5), a secondary moisture-proof layer (6), a second cold-insulating layer (7), a secondary moisture-proof layer (8), a third cold-insulating layer (9) and a main moisture-proof layer (10) which are sequentially arranged from the inside to the outside.

2. The polyisocyanurate cold-insulated pipe according to claim 1, characterized in that: A limiting ring (3) is arranged on the outer wall of the middle part of the working tube (1); the limiting ring (3) is formed by splicing two semicircular rings, the limiting ring (3) is fixed to the outer wall of the working tube (1) by means of a low-temperature adhesive, the thickness of the limiting ring (3) is the same as the thickness of the first cold-insulating layer (5), and a secondary moisture-proof layer (6) is arranged outside the limiting ring (3).

3. The polyisocyanurate cold-insulated pipe according to claim 1, characterized in that: The isolation layer (2) completely covers the outer wall of the working tube (1); and the sealing layer (4) completely covers the isolation layer (2).

4. The polyisocyanurate cold-insulated pipe according to claim 1, characterized in that: The axial lengths of the first cold-insulating layer (5), the second cold-insulating layer (7) and the third cold-insulating layer (9) decrease in sequence, and the ends of the three are arranged in steps, and the steps are arranged in arithmetic steps.

5. The polyisocyanurate cold-insulated pipe according to claim 1, characterized in that: The primary moisture-proof layer (6) completely covers the outside of the first cold-insulating layer (5), and the two are bonded together; the secondary moisture-proof layer (8) completely covers the outside of the second cold-insulating layer (7), and the two are bonded together; the main moisture-proof layer (10) completely covers the outside of the third cold-insulating layer (9), and the two are bonded together; and the outer protective layer (11) completely covers the main moisture-proof layer (10).

6. The polyisocyanurate cold-insulated pipe according to claim 1, characterized in that: A vapor barrier layer (12) is provided at the ends of the first cold insulation layer (5), the second cold insulation layer (7) and the third cold insulation layer (9), the outside of the primary moisture-proof layer (6) not covering the second cold insulation layer (7), and the outside of the secondary moisture-proof layer (8) not covering the third cold insulation layer (9).

7. The polyisocyanurate cold-insulated pipe according to claim 6, characterized in that: The vapor resistance layer (12) is a composite layer structure, comprising multiple layers of rubber coatings and mesh cloth layers arranged between adjacent rubber coatings.

8. The polyisocyanurate cold-insulated pipe according to claim 1, characterized in that: Both ends of the working pipe (1) extend out of the cold-insulating structural layer; waterproof caps (13) are provided at both ends of the cold-insulating structural layer, and the working pipe (1) extends out of the waterproof caps (13).

9. An on-site patching structure for a polyisocyanurate cold-insulated pipe according to any one of claims 1 to 8, characterized in that: The invention comprises a patch insulation layer (14), a polyisocyanurate pipe shell group, a patch main moisture-proof layer (17) and a patch outer protective layer (18) which are sequentially sleeved from the inside to the outside on the outside of the patch position after the two cold-insulating pipes are butt-jointed; the two ends of the patch insulation layer (14) are overlapped on the outside of the sealing layer (4) of the two sections of working pipes (1); the polyisocyanurate pipe shell group is fixed to the patch position by aluminum foil tape; and the patch main moisture-proof layer (17) is bonded to the outer wall of the polyisocyanurate pipe shell group.

10. The on-site patching structure of the polyisocyanurate cold-insulated pipe according to claim 9, characterized in that: The polyisocyanurate tube shell group comprises three layers of polyisocyanurate tube shells, one end of each layer of polyisocyanurate tube shells is in close contact with the end of a cold-insulating pipe on one side, and glass wool (16) is arranged between the end of the cold-insulating pipe on the other side; adjacent polyisocyanurate tube shells are in close contact with the cold-insulating pipes on the opposite sides.

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