A reusable and detachable PIR injection molding insulation structure for cryogenic valves and its construction method.

Abstract

This invention relates to a reusable, detachable, and recyclable PIR injection molding insulation structure for cryogenic valves and its construction method. The insulation structure includes a first module and a second module that cooperate with each other. Both are prefabricated metal shell molds with a split design. From the outside to the inside, they consist of a metal protective layer, a butyl rubber vapor barrier and moisture-proof layer, an aluminum foil composite aerogel felt layer, and a PIR injection molded foam block. A rubber sealing strip and a detachable metal separator sheet with a concave-convex structure are provided at the parting surface, so that the PIR foam forms a two-part, interlocking structure after molding. The valve body is covered with an aluminum foil composite aerogel flexible felt. During construction, a high-pressure foaming machine is used for constant-temperature, multi-stage casting. After curing and demolding, a removable, non-destructive split insulation module is obtained. This invention has the advantages of excellent thermal insulation performance, vapor barrier and moisture-proof, recyclability, and long service life, and is suitable for cryogenic valve insulation projects from -196℃ to 80℃.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation construction technology for cryogenic equipment, specifically to a long-lasting cold insulation structure for cryogenic valves, and more particularly to a detachable and reusable PIR injection molding cold insulation structure for cryogenic valves and its construction method. Background Technology

[0002] Currently, the mainstream construction method for cryogenic valve insulation in China involves on-site formwork using PIR or foamed glass curved panels, manual mixing and pouring of PIR material for foaming, and then applying glass wool for cushioning and insulation on the valve surface. This traditional method has many inherent drawbacks in practical applications and cannot meet the requirements for long-term stable operation and repeated maintenance of cryogenic equipment.

[0003] Firstly, traditional manual mixing and foaming methods suffer from poor precision in the ratio of black and white materials and low mixing uniformity, easily leading to problems such as large cell size, localized open pores, air pockets, and incomplete curing. This results in a high thermal conductivity and insufficient closed-cell rate in the insulation layer, resulting in inconsistent thermal insulation performance. Furthermore, the concentrated heat release during large-volume, one-time casting foaming generates significant internal stress within the foam, making it highly susceptible to cracking and delamination failure under cryogenic thermal cycling conditions.

[0004] Secondly, traditional cold insulation structures often use glass wool as a buffer layer for valve bodies. Glass wool has a high water absorption rate and permeable pores. Under deep cold conditions, external water vapor can easily penetrate and accumulate, freeze and expand, directly cracking the PIR cold insulation foam. In addition, liquid foaming material can penetrate into the interior of glass wool fibers, causing the cold insulation layer structure to be discontinuous, the thermal insulation performance to be greatly reduced, and the service life to be short.

[0005] Furthermore, existing casting molds are mostly fixed, integral molds built on-site using insulation materials. After foaming and curing, the mold and foam are tightly bonded together, making demolding impossible without damage. The insulation structure is a one-time molding structure. During annual valve maintenance, valve core replacement, and equipment maintenance, the insulation layer must be destructively removed, resulting in extremely high operation and maintenance costs. Moreover, after each maintenance, new molds and foaming construction are required, leading to low construction efficiency and significant material waste.

[0006] Finally, after the traditional on-site PIR pouring for cold insulation is completed, a moisture-proof layer structure needs to be applied and constructed on-site. This process is cumbersome and time-consuming, and the quality of the moisture-proof layer is not easy to control. At the same time, the cold insulation structure after traditional construction is prone to flaking and damage during subsequent disassembly and reassembly, making it impossible to reuse and disassemble, and unable to meet the engineering requirements of long-term operation and maintenance of cryogenic valves. Summary of the Invention

[0007] This invention designs a reusable and detachable PIR injection molding insulation structure for cryogenic valves and its construction method. The technical problems it solves are the following in the existing on-site casting insulation construction of cryogenic valves: poor quality of foaming due to manual mixing, easy cracking of foam, insufficient moisture and vapor barrier performance leading to water vapor penetration and frost heave failure, the insulation structure being a one-time molding that cannot be disassembled and reused without damage, valve maintenance requiring destructive dismantling and reconstruction, high operation and maintenance costs and low construction efficiency.

[0008] To solve the aforementioned technical problems, the present invention adopts the following solution: A reusable and detachable cryogenic valve PIR injection molding insulation structure includes a first module and a second module that cooperate with each other. Both the first module and the second module are prefabricated metal shell molds with a split design. After the two are molded together, they form an insulation structure covering the valve body. The first module and the second module, from the outside to the inside, include: a metal protective layer, a butyl rubber vapor barrier and moisture-proof layer, an aluminum foil composite aerogel felt layer, and a PIR injection molded bubble. A rubber sealing strip is provided at the parting surface of the first module and the second module. The top of the first module and the second module has a pre-reserved casting hole, and the top edge has a vent hole. A metal separator sheet is detachably inserted into the inner side of the parting surface of the first module and the second module. The metal separator sheet has a concave and convex structure, so that the molded PIR injection molded bubble forms a split structure with two halves that hug each other. The valve body is covered with an aluminum foil composite aerogel flexible felt.

[0009] Preferably, the metal protective layer is made of aluminum alloy plate or stainless steel plate with a thickness of 0.8 to 1.2 mm; the cavity sidewalls of the first module and the second module are provided with draft angles.

[0010] Preferably, the thickness of the butyl rubber vapor barrier layer is 1.2 to 2.0 mm, and it is fully laid on the inner wall of the metal protective layer; the aluminum foil side of the aluminum foil-backed composite aerogel felt layer faces the inner side of the cavity and is bonded and fixed to the butyl rubber vapor barrier layer.

[0011] Preferably, a release isolation layer is provided on the inner side of the aluminum foil composite aerogel felt layer, which is a sprayed high-temperature resistant release agent for rigid polyurethane foam or a high-temperature resistant PE release film that is laid in full coverage.

[0012] Preferably, the PIR cast bubble has a molding density of 40-50 kg / m³, a closed-cell rate of ≥90%, and a thermal conductivity of ≤0.026 W / m·K at 25°C.

[0013] Preferably, fixing bolts are provided at the parting surface flanges of the first module and the second module; and elastic sealing strips are provided at the overlaps between the first module and the second module and the first pipe insulation layer.

[0014] Preferably, the outside of the pipeline is provided with a first pipeline cold insulation layer, a second pipeline moisture-proof layer, a second pipeline cold insulation layer, a first pipeline moisture-proof layer, and a pipeline protective layer in sequence from the inside to the outside. A pipeline cold insulation end face vapor barrier layer is provided at the end face of the second pipeline cold insulation layer to block the penetration of water vapor along the pipeline axis.

[0015] A reusable and detachable PIR injection molding insulation construction process for cryogenic valves, characterized by employing the aforementioned reusable and detachable PIR injection molding insulation structure for cryogenic valves, comprising the following steps: Step 1: Mold prefabrication: Prefabricate the left and right split mold shell, namely the first module and the second module. The mold cavities of the first module and the second module are reserved with draft angles. Rubber sealing strips are installed on the parting surface. The butyl rubber vapor barrier and moisture-proof layer and the aluminum foil composite aerogel felt layer are sequentially bonded and fixed to the inner wall of the mold shell. Step 2, Demolding and release layer construction: Spray release agent or lay high-temperature resistant PE release film on the inner side of the aluminum foil composite aerogel felt layer on the inner wall of the mold. Step 3, Valve body pretreatment: The entire outer side of the valve body is covered with aluminum foil composite aerogel flexible felt; Step 4, Mold assembly and positioning: Insert a metal separator sheet inside the parting surface of the first module and the second module, align the two halves of the mold and close the mold, and lock them with fixing bolts. Install an elastic sealing strip at the joint between the mold and the first pipe insulation layer. Step 5, Mechanized multi-stage pouring: Use a high-pressure foaming machine to keep the PIR black and white materials at a constant temperature of 20-25℃, and pour them into the mold cavity in stages through the pouring hole. Stop pouring after uniform and fine foam flows out of the vent hole. Step 6, Curing and Demolding: After the PIR foam has fully cured, remove the fixing bolts, separate the first module and the second module, and pull out the metal separator to obtain two symmetrical half of the cold insulation module. Step 7, Assembly and Reuse: Align and assemble the two halves of the PIR insulation module on the outside of the valve. During maintenance, simply break apart the two halves of the insulation module. After maintenance, reassemble and seal for protection.

[0016] Preferably, in step 5, a low-pressure multi-point casting method is adopted, and the constant temperature control temperature of PIR black and white materials is 20-25℃.

[0017] Preferably, in step 6, the curing time in a normal temperature environment is 70 minutes, and the curing time in a low temperature environment in winter is 2 hours.

[0018] Preferably, in step 7, the PIR cold preservation module can be used more than 10 times.

[0019] The reusable and reassembleable cryogenic valve PIR injection molding insulation structure and its construction method have the following beneficial effects: (1) This invention uses a high-pressure foaming machine to replace manual mixing and batching. The PIR black and white materials are kept at the optimal reaction temperature range of 20-25℃, and the proportioning accuracy and mixing uniformity are far superior to manual operation. With the design of a closed metal mold cavity and venting holes, it is ensured that the air in the cavity is completely discharged during the casting process, eliminating the defects of air entrapment. The PIR foam molding density is stably controlled at 40-50 kg / m³. 3 With a closed-cell rate of ≥90% and a stable thermal conductivity of ≤0.026W / (m·K) at 25℃, it completely solves the problems of large pores, localized open pores, and inconsistent performance in traditional artificial foaming.

[0020] (2) This invention abandons the traditional water-absorbing glass wool buffer layer and uses a butyl rubber vapor barrier and moisture-proof layer to fully cover the inner wall of the mold, with a splicing overlap width of ≥50mm and no breaks throughout. Combined with the aluminum foil composite aerogel felt layer, the seams are completely sealed with aluminum foil tape, forming a fully closed-loop vapor barrier system, reducing the external water vapor permeability by more than 95%. The valve body buffer layer uses a hydrophobic and moisture-proof aluminum foil composite aerogel flexible felt, which has no pore permeation problem. This completely avoids the failure caused by freezing and expansion due to water vapor penetrating into the bubble body and freezing at low temperature, and extends the service life of the cold insulation structure from the traditional 1-2 years to more than 10 years.

[0021] (3) This invention uses a prefabricated metal mold with a split design, and the cavity is designed with a draft angle. Combined with the inner wall demolding isolation layer, it achieves non-destructive separation of the PIR foam from the mold after curing. A metal separator sheet with a concave-convex structure is inserted into the parting surface, so that the PIR foam naturally forms a split structure with the left and right halves interlocking after molding. The concave-convex structure of the parting surface ensures accurate alignment of the two halves of the foam block and repeated disassembly and assembly. When the valve is repaired, there is no need to destructively remove the insulation layer. The repair can be completed by simply breaking open the two halves of the module. After the repair is completed, it can be re-aligned, reassembled, and sealed for protection before reuse. The construction period for a single repair is shortened by 70%, and the number of times it can be reused can reach more than 10 times, which greatly reduces material consumption and operation and maintenance costs.

[0022] (4) This invention uses aluminum foil composite aerogel flexible felt as the valve body buffer layer, which completely fits the irregular curved surface of the valve and fills the dead corner cavity to form a flexible buffer structure with soft and hard transition; at the same time, the inner wall of the mold is provided with a back aluminum foil composite aerogel felt layer to isolate the metal mold from the heat dissipation at room temperature, avoid the poor reaction of PIR liquid when it is cold, and buffer the temperature difference stress between the mold and the foam. The soft and hard composite buffer structure can effectively offset the triple temperature change stress of the valve body, foam and mold, stably adapt to the cold and hot cycle conditions of -196℃~80℃, and has no cracking, delamination and deformation during long-term operation, solving the core pain point of traditional cold insulation structure being easily damaged under deep cold conditions. Attached Figure Description

[0023] Figure 1 : First exploded view of the PIR molding insulation structure of the reusable cryogenic valve of the present invention; Figure 2 : Second exploded view of the PIR molding insulation structure of the reusable cryogenic valve of the present invention; Figure 3 : Schematic diagram of the assembly of the PIR molding insulation structure for the reusable cryogenic valve in this invention; Figure 4 The third exploded view of the PIR molding insulation structure for a reusable cryogenic valve of this invention; Figure 5 : A cross-sectional view of the PIR molding insulation structure of the reusable cryogenic valve of this invention.

[0024] Explanation of reference numerals in the attached figures: A—Module 1; B—Module 2; C—Pipeline; D—PIR casting molded bubble block; 1—Metal protective layer; 2—Butyl rubber vapor barrier and moisture-proof layer; 3—Aluminum foil composite aerogel felt layer; 4—Elastic sealing strip; 5—Rubber sealing strip; 6—Metal separator sheet; 7—Aluminum foil composite aerogel flexible felt; 8—Pouring hole; 9—Ventilation hole; 10—Fixing bolt; 11—Pipe protective layer; 12—First pipe cold insulation layer; 13—Second pipe moisture-proof layer; 14—First pipe moisture-proof layer; 15—Pipe cold insulation end face vapor barrier layer; 16—Second pipe cold insulation layer. Detailed Implementation

[0025] The following is combined with Figures 1 to 5 The present invention will be further described as follows: like Figure 1As shown, this invention provides a detachable and reusable PIR injection molding insulation structure for cryogenic valves, comprising a first module A and a second module B that cooperate with each other. Both modules A and B are prefabricated metal shell molds with a split design, forming a complete insulation structure after being closed. This insulation structure is installed outside the pipe C and its valve to provide long-term thermal insulation for the cryogenic valve. From the outside to the inside, the first module A and the second module B include: a metal protective layer 1, a butyl rubber vapor barrier layer 2, an aluminum foil-backed composite aerogel felt layer 3, and a PIR injection molded bubble block D. The metal protective layer 1 is prefabricated from an aluminum alloy plate or stainless steel plate with a thickness of 0.8–1.2 mm, serving as the outer shell structure of the mold and providing structural strength and protection. The butyl rubber vapor barrier layer 2 fully covers the inner wall of the metal protective layer 1, with a thickness of 1.2–2.0 mm and an overlap width ≥50 mm, without any breaks or wrinkles, to block the penetration of external moisture into the insulation structure. The aluminum foil composite aerogel felt layer 3 is set inside the butyl rubber vapor barrier and moisture barrier layer 2, with the aluminum foil side facing the inside of the cavity. It is fully bonded and fixed to the butyl rubber vapor barrier and moisture barrier layer 2 by heat-resistant structural adhesive. The joints are completely sealed with aluminum foil tape to isolate the metal mold from room temperature heat dissipation, avoid poor chemical reaction caused by the PIR liquid cooling, and buffer the temperature difference stress between the mold and the foam.

[0026] This invention constructs a fully closed-loop vapor barrier and stress buffering system through the interlayer synergy of a butyl rubber vapor barrier layer, an aluminum foil aerogel felt backing, a flexible aerogel felt for the valve body, and an elastic sealing strip. The butyl rubber layer and aerogel felt interlock at their joints, blocking water vapor permeation paths; the flexible valve body felt conforms to irregular curved surfaces, forming a soft transition buffer, echoing the outer aerogel felt to jointly offset alternating thermal stress; and the elastic sealing strip seals the overlapping interfaces. As a result, water vapor permeability is reduced by more than 95%, service life is extended to more than 10 years, and it is suitable for operating conditions ranging from -196℃ to 80℃.

[0027] A rubber sealing strip 5 is installed at the parting surface between the first module A and the second module B. After mold closing, the rubber sealing strip 5 is deformed by pressure, achieving a reliable seal at the parting surface and preventing PIR liquid from leaking from the parting surface during the pouring process. Fixing bolts 10 are installed at the flange of the parting surface between the first module A and the second module B. These bolts precisely position and lock the two modules in place, ensuring the dimensional accuracy and sealing of the mold cavity after mold closing. An elastic sealing strip 4 is installed at the overlap between the mold and the insulation layer of pipe C. The elastic sealing strip 4 is made of closed-cell elastic material to prevent the mold from damaging the insulation layer 12 of the first pipe under hard pressure, while also sealing any gaps where water vapor can penetrate.

[0028] like Figure 2As shown, the top of the first module A and the second module B are provided with pouring holes 8 for injecting PIR foaming liquid into the cavity after mold closing. The top edge of the mold also has vent holes 9, which are connected to the cavity to expel air from the cavity during pouring, ensuring that the PIR liquid is densely filled without air pockets or trapped air. The sidewalls of the mold cavity have a slight draft angle to ensure that there is no jamming or pulling damage during demolding.

[0029] like Figure 3 As shown, the first module A and the second module B are locked together by fixing bolts 10 to form a complete casting cavity. During casting, PIR liquid is injected into the cavity through the pouring hole 8, and the air in the cavity is discharged through the vent hole 9. Casting stops when uniform and fine foam flows out of the vent hole 9, indicating that the cavity is completely filled.

[0030] like Figure 4 As shown, before mold closing and casting, a metal separator sheet 6 is detachably inserted into the inner side of the parting surface between the first module A and the second module B. The metal separator sheet 6 has a concave-convex structure. After the PIR foam foams and cures in the cavity, due to the isolation effect of the metal separator sheet 6, the molded PIR casting bubble block D naturally forms a two-part, interlocking structure. A matching structure corresponding to the concave-convex structure of the metal separator sheet 6 is formed at the parting surface, facilitating precise alignment and repeated assembly / disassembly of the two bubble blocks. The metal separator sheet 6 is removed after the PIR foam has fully cured, making the two bubble blocks independent and separable.

[0031] This invention achieves non-destructive assembly and disassembly of the cooling module through the coordinated use of a half-mold, draft angle, demolding isolation layer, and separating sheet. The half-mold and draft angle provide the structural basis for demolding, the demolding isolation layer prevents the foam from sticking to the inner lining, and the separating sheet allows the PIR foam to naturally form two halves with a textured interlocking structure after curing. After demolding, a split module that can be broken apart and reset is obtained, requiring no destructive disassembly for maintenance and can be reused more than 10 times.

[0032] The outer side of the valve body is entirely covered with aluminum foil composite aerogel flexible felt 7. This felt perfectly conforms to the valve's irregular curved surface, filling dead angles and cavities, eliminating voids and forming a flexible buffer layer with a soft-hard transition. This layer counteracts the shrinkage and deformation stress generated by low-temperature thermal cycling, preventing the rigid PIR foam from peeling off or cracking from the metal valve body. The aluminum foil composite aerogel flexible felt 7 is a hydrophobic and moisture-proof material with no pores, completely eliminating the high water absorption rate of traditional glass wool buffer layers.

[0033] like Figure 5 The diagram shows the complete cross-sectional structure of the cold insulation structure of the present invention when actually installed on pipe C. (The diagram is from...) Figure 5As can be seen, from the outside to the inside are: metal protective layer 1, butyl rubber vapor barrier and moisture barrier layer 2, aluminum foil composite aerogel felt layer 3, PIR casting molded bubble block D, aluminum foil composite aerogel flexible felt 7, and aluminum foil composite aerogel flexible felt 7 is wrapped around the outer surface of valve and pipe C.

[0034] The exterior of pipe C is sequentially configured from the inside out with a first pipe insulation layer 12, a second pipe moisture-proof layer 13, a second pipe insulation layer 16, a first pipe moisture-proof layer 14, and a pipe protective layer 11. A pipe insulation end-face vapor barrier layer 15 is provided at the end face of the second pipe insulation layer 16 to prevent water vapor from penetrating along the pipe's axial direction. An elastic sealing strip 4 is positioned at the overlap between the metal protective layer 1 and the pipe protective layer 11 to achieve a flexible sealing transition. At the parting surface between the first module A and the second module B, the gap formed after the metal separator sheet 6 is removed is sealed by a rubber sealing strip 5.

[0035] This invention also provides a reusable and detachable PIR injection molding insulation process for cryogenic valves, specifically including the following steps: Step 1: Pre-construction preparation: Select aluminum alloy or stainless steel plates with a thickness of 0.8–1.2 mm at the factory to prefabricate a split mold shell with left and right openings, namely Module A and Module B. Draft angles are provided in the mold cavity, and rubber sealing strips 5 are installed on the parting surface. A 1.2–2.0 mm thick butyl rubber vapor barrier layer 2 and an aluminum foil-backed composite aerogel felt layer 3 are sequentially bonded and fixed to the inner wall of the mold shell, with the aluminum foil side of the aluminum foil-backed composite aerogel felt layer 3 facing the inside of the cavity. The seams are completely sealed with aluminum foil tape. The bonded and assembled metal mold shell is supplied to the site as a prefabricated product.

[0036] Step 2, Demolding and Isolation Layer Construction: Spray a high-temperature resistant release agent for rigid polyurethane foam onto the inner side of the aluminum foil composite aerogel felt layer 3 on the inner wall of the mold, or lay a high-temperature resistant PE release film to form a non-adhesive isolation and demolding interface, ensuring that the PIR foam does not stick to the inner lining structure after curing.

[0037] Step 3, Valve body pretreatment: After the valve passes the anti-corrosion acceptance test, clean the dust and impurities on the valve body, flange, bolts and valve stem surfaces. Wrap the entire outer side of the valve body with aluminum foil composite aerogel flexible felt 7, so that it completely fits the irregular curved surface of the valve, without any gaps or wrinkles, to achieve full-area flexible buffer isolation.

[0038] Step 4, Mold Assembly and Positioning: Insert metal separator sheets 6 inside the parting surface of the first module A and the second module B. Align and close the two mold halves, and precisely position and lock them using fixing bolts 10. Install an elastic sealing strip 4 at the overlap between the mold and the first pipe insulation layer 12. A pouring hole 8 is pre-reserved at the top of the mold, and an vent hole 9 is opened at the top edge.

[0039] Step 5, Mechanized Multi-Stage Casting: Using a portable high-pressure foaming machine, the PIR black and white materials are kept at a constant temperature of 20-25℃. A low-pressure, multi-point multi-stage casting method is employed, with the PIR liquid injected into the mold cavity through the pouring hole 8. Casting is stopped after uniform and fine foam flows out of the vent hole 9, ensuring the mold cavity is free of voids and densely filled.

[0040] Step 6, Curing and Demolding: Curing at room temperature for 70 minutes, or at low temperature in winter for 2 hours. After the PIR foam is fully matured and cross-linked and stable, remove the fixing bolts 10, horizontally separate the first module A and the second module B, and pull out the metal separator sheet 6 to obtain a complete split PIR cold insulation module that is symmetrical on the left and right, namely the PIR casting molded foam block D.

[0041] Step 7: Assembly, Sealing, and Reusable Maintenance: Align and assemble the two halves of the PIR cast foam block D onto the outside of the valve, using the concave and convex structures at the parting line for precise positioning. During valve maintenance, remove the outer metal sealing structure and simply pry open the two halves of the insulation module to complete the maintenance. After maintenance, reassemble and reseal the modules for seamless reuse.

[0042] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A reusable and detachable PIR molding insulation structure for cryogenic valves, characterized in that: It includes a first module (A) and a second module (B) that cooperate with each other. Both the first module (A) and the second module (B) are prefabricated metal shell molds that are split in half. After the two are molded together, they form a cold insulation structure that covers the valve body. The first module (A) and the second module (B) include, from the outside to the inside: a metal protective layer (1), a butyl rubber vapor barrier and moisture barrier layer (2), a back aluminum foil composite aerogel felt layer (3), and a PIR casting molded bubble block (D); A rubber sealing strip (5) is provided at the parting surface between the first module (A) and the second module (B); The top of the first module (A) and the second module (B) are reserved with casting holes (8), and the top edge is provided with venting holes (9). A metal separator sheet (6) is detachably inserted into the inner side of the parting surface of the first module (A) and the second module (B). The metal separator sheet (6) is provided with a concave-convex structure so that the molded PIR casting bubble (D) forms a left and right half-hugging split structure. The valve body is covered with aluminum foil composite aerogel flexible felt (7).

2. The reusable and detachable cryogenic valve PIR molding insulation structure according to claim 1, characterized in that: The metal protective layer (1) is made of aluminum alloy plate or stainless steel plate with a thickness of 0.8 to 1.2 mm; the cavity sidewalls of the first module (A) and the second module (B) are provided with draft angles.

3. The reusable and detachable cryogenic valve PIR molding insulation structure according to claim 1, characterized in that: The thickness of the butyl rubber vapor barrier and moisture-proof layer (2) is 1.2 to 2.0 mm, and it is fully laid on the inner wall of the metal protective layer (1); the aluminum foil side of the aluminum foil backing composite aerogel felt layer (3) faces the inner side of the cavity and is bonded and fixed to the butyl rubber vapor barrier and moisture-proof layer (2).

4. The reusable and detachable cryogenic valve PIR molding insulation structure according to claim 1, characterized in that: The inner side of the aluminum foil composite aerogel felt layer (3) is provided with a release isolation layer, which is a sprayed polyurethane rigid foam special high temperature resistant release agent or a high temperature resistant PE release film that is fully covered.

5. The reusable and detachable cryogenic valve PIR molding insulation structure according to claim 1, characterized in that: The PIR cast bubble block (D) has a molding density of 40-50 kg / m³, a closed-cell rate of ≥90%, and a thermal conductivity of ≤0.026 W / m·K at 25℃.

6. The reusable and detachable cryogenic valve PIR molding insulation structure according to any one of claims 1-5, characterized in that: Fixing bolts (10) are provided at the parting edge of the first module (A) and the second module (B); elastic sealing strips (4) are provided at the overlap of the first module (A) and the second module (B) with the first pipe insulation layer (12).

7. The reusable and detachable cryogenic valve PIR molding insulation structure according to claim 6, characterized in that: The pipe (C) is provided with a first pipe insulation layer (12), a second pipe moisture barrier layer (13), a second pipe insulation layer (16), a first pipe moisture barrier layer (14), and a pipe protection layer (11) from the inside to the outside. A pipe insulation end face vapor barrier layer (15) is provided at the end face of the second pipe insulation layer (16) to block the penetration of water vapor along the pipe axis.

8. A method for constructing a reusable, detachable, cryogenic valve using PIR injection molding for cold insulation, characterized in that... The removable and reusable cryogenic valve PIR molding insulation structure according to claim 7 includes the following steps: Step 1, Mold prefabrication: Prefabricate the left and right split mold shell, namely the first module (A) and the second module (B). The mold cavity of the first module (A) and the second module (B) is reserved with draft angle. Rubber sealing strip (5) is installed on the parting surface. Butyl rubber vapor barrier and moisture-proof layer (2) and aluminum foil composite aerogel felt layer (3) are sequentially bonded and fixed to the inner wall of the mold shell. Step 2, Demolding and isolation layer construction: Spray a release agent or lay a high-temperature resistant PE release film on the inner side of the aluminum foil composite aerogel felt layer (3) on the inner wall of the mold shell; Step 3, Valve body pretreatment: The valve body is completely covered with aluminum foil composite aerogel flexible felt (7); Step 4, Mold assembly and positioning: Insert metal separator sheets (6) into the inner side of the parting surface of the first module (A) and the second module (B), align the two halves of the mold and close the mold, and lock them with fixing bolts (10). Add an elastic sealing strip (4) at the joint between the mold and the first pipe insulation layer (12). Step 5, Mechanized multi-stage pouring: The PIR black and white material is kept at a constant temperature of 20-25℃ using a high-pressure foaming machine and injected into the mold cavity in stages through the pouring hole (8). The pouring is stopped after uniform and fine foam flows out of the vent hole (9). Step 6, Curing and Demolding: After the PIR foam has fully matured, remove the fixing bolts (10), separate the first module (A) and the second module (B), and pull out the metal separator sheet (6) to obtain two symmetrical half of the cold insulation module; Step 7, Assembly and Reuse: Align and assemble the two halves of the PIR insulation module on the outside of the valve. During maintenance, simply break apart the two halves of the insulation module. After maintenance, reassemble and seal for protection.

9. The PIR injection molding and cold insulation construction method for a reusable, detachable cryogenic valve according to claim 8, characterized in that... In step 5, a low-pressure, multi-point, staged casting method is adopted, and the constant temperature control temperature of the PIR black and white materials is 20-25℃.

10. The PIR injection molding and cold insulation construction method for a reusable, detachable cryogenic valve according to claim 8, characterized in that... In step 6, the PIR cold preservation module can be used more than 10 times.

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