Prefabricated heat preservation bell and spigot corrugated reinforced steel cylinder concrete composite pipe and design method thereof

Abstract

The invention belongs to the technical field of heating pipelines, and particularly relates to a prefabricated heat preservation bell and spigot corrugated reinforced steel cylinder concrete composite pipe and a design method thereof. In order to solve the technical problems of strong destructiveness of high internal and external pressure effects, prominent thermal strain damage under large temperature difference working conditions and serious corrosion in high-temperature and high-humidity environments, the invention provides the prefabricated heat-preservation bell and spigot corrugated reinforced steel cylinder concrete composite pipe which sequentially comprises a protective layer, a heat-preservation layer, a steel cylinder and a lining layer from outside to inside, and bell and spigot structures are arranged at pipe end joints. The bell and spigot is sealed by double rubber rings; the design method of the composite pipe comprises the following steps: respectively designing the wall thickness of the steel cylinder; the bell and spigot structure is provided with a retaining bolt and a strain compensation groove; a composite pipe lining layer; the composite pipe comprises a protective layer and an insulating layer. According to the invention, the structural design of the large-diameter heat supply pipeline is realized, the problems of high internal and external pressure, large temperature difference thermal strain, high-temperature and high-humidity corrosion and the like of the heat supply pipeline are solved, the hot water conveying performance of the heat supply pipeline is ensured, the cost is reduced, and the safety is improved.

Description

Technical Field

[0001] This invention belongs to the field of heating pipeline technology, and particularly relates to a prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe and its design method. Background Art

[0002] With the advancement of urbanization, the urban heating area is constantly expanding, and the heating pipeline industry is developing rapidly. The design of heating pipeline structures needs to focus on the strength of large-diameter pipelines under high internal and external pressure, the thermal strain under large temperature differences, and the insulation and corrosion prevention in high-temperature and high-humidity environments. High-density polyethylene plastic outer sheath polyurethane foam prefabricated direct-buried insulated pipes (hereinafter referred to as "prefabricated direct-buried insulated pipes") adopt a three-layer composite structure of steel cylinder, rigid polyurethane foam insulation layer, and high-density polyethylene outer sheath. Due to their low cost, excellent insulation and energy-saving properties, and waterproof and pressure-resistant performance, they are widely used in municipal centralized heating. However, in actual engineering projects, prefabricated direct-buried insulated pipes have revealed the following disadvantages: 1. The steel cylinder is welded at the joint, resulting in reduced strength at the weld; 2. Corrugated pipes or sleeves are required between pipes to compensate for thermal strain, leading to high construction costs; 3. The steel cylinder is in a high-temperature and high-humidity service environment for a long time, increasing the risk of corrosion. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology and address the technical problems of strong destructive effects under high internal and external pressure, prominent thermal strain damage under large temperature difference conditions, and severe corrosion in high temperature and high humidity environments, this invention provides a prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe and its design method.

[0004] According to a first aspect of the present invention, a prefabricated insulated socket-reinforced corrugated steel cylinder concrete composite pipe is provided. The pipe body consists of a protective layer 7, an insulation layer 1, a steel cylinder 6, and an inner lining layer 9, arranged from the outside to the inside. The protective layer 7 completely covers the insulation layer 1 circumferentially and is firmly bonded to the outer surface of the insulation layer 1 by an adhesive. The insulation layer 1 completely covers the steel cylinder 6 circumferentially, and the inner surface of the insulation layer 1 is firmly bonded to the outer wall of the steel cylinder 6 by an adhesive. The inner lining layer 9 is densely filled into the inner wall of the steel cylinder 6. A U-shaped corrugated reinforcing structure 8 is pressed on the pipe wall of the steel cylinder 6 and surrounds it circumferentially. One end of the pipe is a socket 4, and the other end is a spigot 3. A radial bolt hole is provided on the end face of the socket 4, which penetrates the outer wall of the socket 4 and communicates with the inner cavity of the pipe. The outer wall of the spigot 3 is provided with a circumferential double U-shaped groove, with the front groove being closer to the outermost front edge of the spigot 3 and the rear groove being farther away from the outermost front edge of the spigot 3. The anti-reverse bolt 5 includes a head with a relatively wide cross-section and a screw connected perpendicularly to the head. The screw and the bolt hole of the socket 4 are threaded together to form a threaded pair. When connecting the pipe, the spigot 3 is inserted into the socket 4 to the designed depth. The screw of the anti-reverse bolt 5 is screwed into the bolt hole until the lower surface of the head of the anti-reverse bolt 5 is close to the inner wall of the socket 4. The rear groove is the sliding groove of the anti-reverse bolt 5. The bottom end of the screw of the anti-reverse bolt 5 passes radially through the outer wall of the socket 4 and falls into the rear groove of the spigot 3. It can slide along the pipe axis to form axial anti-reverse and circumferential anti-rotation locking. When the socket 4 and the spigot 3 are connected, a double rubber ring seal is formed between the socket 4 and the spigot 3. The double rubber ring includes an L-shaped rubber ring 2 and a T-shaped rubber ring 10. The L-shaped rubber ring is placed in the gap between the end face of the socket 4 and the top of the spigot 3. The T-shaped rubber ring is embedded in the front groove of the spigot 3, and its flange is close to the inner wall of the socket 4 to form a seal.

[0005] According to a second aspect of the present invention, a design method for a prefabricated insulated socket-joint corrugated reinforced steel cylinder concrete composite pipe is provided, comprising the following steps: Step 1: Design the steel cylinder wall thickness; Step 2: Design a socket structure with anti-reverse bolts and strain compensation grooves; Step 3: Design the inner lining of the composite pipe, which is composed of cement mortar or reinforced concrete; Step 4: Design the insulation layer and protective layer of the composite pipe. The insulation layer is made of rigid polyurethane foam, and the protective layer is made of high-density polyethylene.

[0006] The beneficial effects of this invention are as follows: This invention, a prefabricated insulated socket-joint corrugated reinforced steel cylinder concrete composite pipe and its design method, provides a systematic design approach for large-diameter heating pipelines. First, the circumferential tensile stress of the steel cylinder wall under internal pressure is analyzed, and the steel cylinder wall thickness is designed. Then, a socket structure with anti-reverse bolts and strain compensation grooves is designed. Finally, the inner lining layer (cement mortar or reinforced concrete), insulation layer (rigid polyurethane foam), and protective layer (high-density polyethylene) of the steel cylinder are designed. Heating pipelines with diameters ranging from 200 to 1600 mm have been designed using this method.

[0007] By designing the steel cylinder wall thickness under internal pressure conditions, the internal pressure strength of the heating pipeline is ensured while saving steel consumption. The heating pipeline features a four-layer composite structure from the outside in: a high-density polyethylene layer, a rigid polyurethane foam layer, a steel cylinder, and an inner lining layer made of cement mortar or reinforced concrete. This design improves resistance to external pressure and enhances thermal insulation performance. A socket-type heating pipeline with anti-reverse bolts and strain compensation grooves is designed, solving the problem of reduced strength at traditional welded pipe connections. The anti-reverse bolts slide along the strain compensation grooves to compensate for thermal strain, saving on compensator installation and reducing construction costs. The cement mortar or reinforced concrete lining prevents direct contact between hot water and the steel cylinder, effectively improving the corrosion resistance of the heating pipeline. This invention achieves a structural design for large-diameter heating pipelines, solving the technical problems of strong destructive effects under high internal and external pressure, significant thermal strain damage under large temperature difference conditions, and severe corrosion in high-temperature and high-humidity environments. It ensures the performance of the heating pipeline in transporting hot water while reducing costs and improving safety. Attached Figure Description

[0008] Figure 1 The present invention is a prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe (the inner lining is composed of cement mortar). Figure 2 This invention relates to a prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe (with an inner lining made of reinforced concrete). Figure 3 This is a flowchart illustrating the design method of the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe of the present invention.

[0009] Attached reference numerals: 1-Insulation layer, 2-L-shaped rubber ring, 3-Spigot, 4-Socket, 5-Anti-reverse bolt, 6-Steel cylinder, 7-Protective layer, 8-U-shaped corrugated reinforcement structure, 9-Inner lining layer, 10-T-shaped rubber ring, 11-Reinforcing cage, 12-First flared section of socket, 13-Second flared section of socket, 14-Third flared section of socket. DETAILED DESCRIPTION

[0010] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0011] In some embodiments, such as Figure 1 and 2 As shown, the prefabricated insulated socket-reinforced corrugated steel cylinder concrete composite pipe provided by the present invention comprises, from the outside to the inside, a protective layer 7, an insulation layer 1, a steel cylinder 6, and an inner lining layer 9. The protective layer 7 completely covers the insulation layer 1 circumferentially and is firmly bonded to the outer surface of the insulation layer 1 with adhesive. The insulation layer 1 completely covers the steel cylinder 6 circumferentially, and the inner surface of the insulation layer 1 is firmly bonded to the outer wall of the steel cylinder 6 with adhesive. The inner lining layer 9 is densely filled into the inner wall of the steel cylinder 6. A U-shaped corrugated reinforcing structure 8 is pressed onto the wall of the steel cylinder 6 and surrounds it circumferentially. One end of the pipe is a socket 4, and the other end is a spigot 3. A radial bolt hole is provided on the end face of the socket 4, which penetrates the outer wall of the socket 4 and communicates with the inner cavity of the pipe. The outer wall of the spigot 3 is provided with a circumferential double U-shaped groove, with the front groove being closer to the outermost front edge of the spigot 3 and the rear groove being farther away from the outermost front edge of the spigot 3. Anti-lock bolts are also present. The bolt 5 includes a head with a relatively wide cross-section and a screw connected perpendicularly to the head. The screw and the bolt hole of the socket 4 are threaded together to form a threaded pair. When connecting the pipe, the spigot 3 is inserted into the socket 4 to the designed depth. The screw of the anti-reverse bolt 5 is screwed into the bolt hole until the lower surface of the head of the anti-reverse bolt 5 is close to the inner wall of the socket 4. The rear groove is the sliding groove of the anti-reverse bolt 5. The bottom end of the screw of the anti-reverse bolt 5 passes radially through the outer wall of the socket 4 and falls into the rear groove of the spigot 3. It can slide along the pipe axis to form axial anti-reverse and circumferential anti-rotation locking. When the socket 4 and the spigot 3 are connected, a double rubber ring seal is formed between the socket 4 and the spigot 3. The double rubber ring includes an L-shaped rubber ring 2 and a T-shaped rubber ring 10. The L-shaped rubber ring is placed in the gap between the end face of the socket 4 and the top of the spigot 3. The T-shaped rubber ring is embedded in the front groove of the spigot 3, and its flange is close to the inner wall of the socket 4 to form a seal.

[0012] Preferably, the protective layer 7 is a high-density polyethylene layer, and the insulation layer 1 is a rigid polyurethane foam layer; Preferably, the inner lining layer 9 is made of cement mortar or reinforced concrete. When the inner lining layer 9 is made of reinforced concrete, a steel cage 11 is embedded in the layer. Preferably, the design depth is such that the distance between the insert and the socket and the left end of the back groove is 20 mm. L The depth of insertion into the socket, where L The total length of the composite pipe body is given. is the coefficient of thermal expansion of the composite pipe.

[0013] In some embodiments, such as Figure 3 As shown, the design method for prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe provided by the present invention includes the following steps: Step 1: Design the steel cylinder wall thickness; Step 2: Design a socket structure with anti-reverse bolts and strain compensation grooves; Step 3: Design the inner lining of the composite pipe, which is composed of cement mortar or reinforced concrete; Step 4: Design the insulation layer and protective layer of the composite pipe. The insulation layer is made of rigid polyurethane foam, and the protective layer is made of high-density polyethylene.

[0014] Preferably, in step one, the steel cylinder wall thickness is designed as follows: Calculate internal pressure p The circumferential tensile stress of the tube under action is calculated using a uniform tube model to determine the steel cylinder wall thickness. t : ; in, p For internal pressure, D The inner diameter of the steel cylinder To design the yield stress.

[0015] Preferably, the internal pressure p The pressure is 1.2~2.1 MPa.

[0016] Preferably, the inner diameter of the steel cylinder D The value range is 200~1600mm.

[0017] Preferably, the selected steel material is Q355 or Q420 steel, with a corresponding yield stress of 355MPa or 420MPa, and a design yield stress of... Take 60% of the yield stress of the corresponding material.

[0018] Preferably, the surface of the steel cylinder is provided with double U-shaped corrugations.

[0019] Preferably, step two, designing the socket structure with anti-reverse bolts and strain compensation grooves, specifically involves: First, design the socket structure. The socket structure is made of Q355 or Q420 steel plate rolled into three flared sections and welded to the outer wall of the steel cylinder. The steel plate thickness of the socket structure is 5~12mm, and the total length is 180~220mm. For example... Figure 1 and 2As shown, the first flared section 12 is flush with the outer wall of the steel cylinder, accounting for 7% to 8% of the total length; the second flared section 13 has an inner diameter 4 to 6 mm larger than the first flared section 12, accounting for 70% to 76% of the total length; the third flared section 14 is outwardly flared, with an angle of 10° to 15° with the second flared section 13, accounting for 17% to 22% of the total length. A locking bolt hole is provided at the junction of the second flared section 13 and the third flared section 14 for screwing in an M20 locking bolt.

[0020] Then, the spigot structure was designed, consisting of double U-shaped grooves, directly pressed into shape on the steel cylinder wall. The groove closest to the outermost tip of the spigot is the front groove, and the groove furthest from the outermost tip is the rear groove. The front groove is 45-60 mm from the outermost tip of the spigot, with a depth of 8-10 mm. The rear groove, serving as a strain compensation groove, is 50-75 mm from the front groove, with a depth of 4-8 mm and a width of [missing information]. d : ; in, The coefficient of thermal expansion of the composite pipe is... L Let ΔT be the total length of the composite pipe, and ΔT be the temperature change of the composite pipe.

[0021] Preferably, the total length of the composite pipe is... L The range is 6000~12000mm.

[0022] Preferably, the coefficient of thermal expansion of the composite tube is... 8×10 -6 ~12×10 -6 / ℃.

[0023] Preferably, the temperature change ΔT of the composite tube is 100~120℃.

[0024] The sealing performance of the socket and spigot is ensured by double rubber rings. An L-shaped rubber ring is placed in the gap between the end face of the socket and the top of the spigot, while a T-shaped rubber ring is installed in the front groove of the spigot. When the socket and spigot are joined, the spigot is inserted into the socket, and the L-shaped rubber ring is compressed. When the distance between the anti-reverse bolt and the left end of the strain compensation groove is 20... L When tightening the anti-reverse bolt, maintain a 5-8mm gap between the second flared section of the socket and the spigot.

[0025] Preferably, the L-shaped rubber ring is hollow and the compression ratio is 35%~45%.

[0026] Preferably, in step three, the inner lining of the composite pipe is designed, wherein the inner lining is composed of cement mortar or reinforced concrete, specifically as follows: The inner lining is made of cement mortar or reinforced concrete. When the inner diameter of the steel cylinder is 200~800mm, the inner lining is made of cement mortar with a thickness of 10~15mm; when the inner diameter of the steel cylinder is 900~1000mm, the inner lining is made of cement mortar with a thickness of 20~30mm; when the inner diameter of the steel cylinder is 1000~1200mm, the inner lining is made of cement mortar with a thickness of 20~30mm or reinforced concrete with a thickness of 55-65mm; when the inner diameter of the steel cylinder is 1200~1400mm, the inner lining is made of reinforced concrete with a thickness of 65-70mm; when the inner diameter of the steel cylinder is 1400~1600mm, the inner lining is made of reinforced concrete with a thickness of 70-85mm.

[0027] Preferably, in step four, the insulation layer and protective layer of the composite pipe are designed. The insulation layer is made of rigid polyurethane foam, and the protective layer is made of high-density polyethylene. Specifically: The insulation layer is composed of a rigid polyurethane foam layer, and the protective layer is composed of a high-density polyethylene layer. When the inner diameter of the steel cylinder is 200~500mm, the insulation layer is composed of rigid polyurethane foam with a thickness of 42~55mm, and the protective layer is composed of a high-density polyethylene outer layer with a thickness of 4~7mm; when the inner diameter of the steel cylinder is 500~900mm, the insulation layer is composed of rigid polyurethane foam with a thickness of 55~59mm, and the protective layer is composed of high-density polyethylene with a thickness of 7~10mm; when the inner diameter of the steel cylinder is 1000~1200mm, the insulation layer is composed of rigid polyurethane foam with a thickness of 59~65mm, and the protective layer is composed of high-density polyethylene with a thickness of 11~13mm; when the inner diameter of the steel cylinder is 1200~1600mm, the insulation layer is composed of rigid polyurethane foam with a thickness of 65~104mm, and the protective layer is composed of high-density polyethylene with a thickness of 13~20mm.

[0028] This example illustrates the design internal pressure. p The design dimensions of some prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe structures with an inner lining of cement mortar are shown in Table 1, and those with an inner lining of reinforced concrete are shown in Table 2.

[0029] Table 1

[0030] Table 2

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made to the present invention should be included within the scope of protection of the present invention.

Claims

1. A precast insulated socket corrugated reinforced steel cylinder concrete composite pipe, characterized in that, The pipe body consists of a protective layer, an insulation layer, a steel cylinder, and an inner lining layer, arranged from the outside to the inside. The protective layer completely covers the insulation layer circumferentially and is firmly bonded to the outer surface of the insulation layer with adhesive. The insulation layer completely covers the steel cylinder circumferentially, and its inner surface is firmly bonded to the outer wall of the steel cylinder with adhesive. The inner lining layer densely fills the inner wall of the steel cylinder. A U-shaped corrugated reinforcement structure is pressed onto the pipe wall of the steel cylinder, encircling the pipe wall circumferentially. One end of the pipe is a socket, and the other end is a spigot. A radial bolt hole is provided on the end face of the socket, which penetrates the outer wall of the socket and communicates with the inner cavity of the pipe. The outer wall of the spigot has a circumferential double U-shaped groove, with the front groove closest to the outermost edge of the spigot and the rear groove furthest from the outermost edge of the spigot. The anti-reverse bolt includes a head with a relatively wide cross-section. The screw is perpendicularly connected to the head, and the screw and the threaded engagement of the bolt hole in the socket form a threaded pair. When connecting the pipe, the spigot is inserted into the socket to the designed depth, and the screw of the anti-reverse bolt is screwed into the bolt hole until the lower surface of the head of the anti-reverse bolt is pressed against the inner wall of the socket. The rear groove is the sliding groove of the anti-reverse bolt. The bottom end of the anti-reverse bolt passes radially through the outer wall of the socket and falls into the rear groove of the spigot, and can slide along the pipe axis to form axial anti-reverse and circumferential anti-rotation locking. When the socket and spigot are connected, a double rubber ring seal is formed between the socket and the spigot. The double rubber ring includes an L-shaped rubber ring and a T-shaped rubber ring. The L-shaped rubber ring is placed in the gap between the end face of the socket and the top of the spigot, and the T-shaped rubber ring is embedded in the front groove of the spigot. Its flange is pressed against the inner wall of the socket to form a seal.

2. The prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 1, characterized in that, The inner diameter of the steel cylinder ranges from 200 to 1600 mm, and the total length of the composite pipe is from 6000 to 12000 mm.

3. The prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 1, characterized in that, The steel cylinder is made of Q355 or Q420 steel, with a corresponding yield stress of 355MPa or 420MPa.

4. The prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 1, characterized in that, The inner lining is made of cement mortar or reinforced concrete. When the inner lining is made of reinforced concrete, a steel cage is embedded in the layer.

5. The design method of the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Design the steel cylinder wall thickness; Step 2: Design a socket structure with anti-reverse bolts and strain compensation grooves; Step 3: Design the inner lining of the composite pipe, which is composed of cement mortar or reinforced concrete; Step 4: Design the insulation layer and protective layer of the composite pipe. The insulation layer is made of rigid polyurethane foam, and the protective layer is made of high-density polyethylene.

6. The design method for the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 5, characterized in that, The first step, designing the steel cylinder wall thickness, specifically involves calculating the internal pressure. p The circumferential tensile stress of the tube under action is calculated using a uniform tube model to determine the steel cylinder wall thickness. t : ； in, p For internal pressure, D The inner diameter of the steel cylinder To design the yield stress.

7. The design method for the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 5, characterized in that, The socket structure is made of Q355 or Q420 steel plate rolled into three flared sections and welded to the outer wall of the steel cylinder. The steel plate of the socket structure has a thickness of 5-12mm and a total length of 180-220mm. The first flared section is close to the outer wall of the steel cylinder and accounts for 7%-8% of the total length. The inner diameter of the second flared section is 4-6mm larger than that of the first flared section and accounts for 70%-76% of the total length. The third flared section is outwardly flared and has an angle of 10°-15° with the second flared section, accounting for 17%-22% of the total length. A locking bolt hole is provided at the junction of the second and third flared sections for screwing in a locking bolt.

8. The design method for the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 5, characterized in that, The socket structure has a double U-shaped circumferential groove on its outer wall, which is directly pressed into shape on the steel cylinder wall. The groove closest to the outermost front edge of the socket is the front groove, and the groove furthest from the outermost front edge is the rear groove. The front groove is 45-60mm from the outermost front edge of the socket and has a depth of 8-10mm. The rear groove is a strain compensation groove, 50-75mm from the front groove, with a depth of 4-8mm and a width of [missing information]. d : ； in, The coefficient of thermal expansion of the composite pipe is... L Let ΔT be the total length of the composite pipe, and ΔT be the temperature change of the composite pipe.

9. The design method for the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 5, characterized in that, The design of the inner lining layer of the steel cylinder in step three is as follows: when the inner diameter of the steel cylinder is 200~800mm, the inner lining layer is composed of cement mortar with a thickness of 10~15mm; when the inner diameter of the steel cylinder is 900~1000mm, the inner lining layer is composed of cement mortar with a thickness of 20~30mm; when the inner diameter of the steel cylinder is 1000~1200mm, the inner lining layer is composed of cement mortar with a thickness of 20~30mm or the inner lining layer is composed of reinforced concrete with a thickness of 55-65mm; when the inner diameter of the steel cylinder is 1200~1400mm, the inner lining layer is composed of reinforced concrete with a thickness of 65-75mm; when the inner diameter of the steel cylinder is 1400~1600mm, the inner lining layer is composed of reinforced concrete with a thickness of 75-85mm.

10. The design method for the prefabricated insulated socket corrugated reinforced steel cylinder concrete composite pipe according to claim 5, characterized in that, Step four, designing the insulation and protective layers of the steel cylinder, specifically involves the following: When the inner diameter of the steel cylinder is 200-500mm, the insulation layer is made of rigid polyurethane foam with a thickness of 42-55mm, and the protective layer is made of high-density polyethylene with a thickness of 4-7mm; when the inner diameter of the steel cylinder is 500-900mm, the insulation layer is made of rigid polyurethane foam with a thickness of 55-59mm, and the protective layer is made of high-density polyethylene with a thickness of 7-10mm; when the inner diameter of the steel cylinder is 1000-1200mm, the insulation layer is made of rigid polyurethane foam with a thickness of 59-65mm, and the protective layer is made of high-density polyethylene with a thickness of 11-13mm; when the inner diameter of the steel cylinder is 1200-1600mm, the insulation layer is made of rigid polyurethane foam with a thickness of 65-104mm, and the protective layer is made of high-density polyethylene with a thickness of 13-20mm.

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