An axially slidable double-layer composite casing and its connection method

Abstract

The present invention relates to the technology of thermal pipelines, aiming to provide a double-layer composite casing that can slide axially and its connection method. The composite casing includes an inner layer pipe and an outer layer pipe that are coaxially nested and installed; at least two sets of support and sliding mechanisms perpendicular to the axial direction are arranged between the inner layer pipe and the outer layer pipe; the bottom end is fixedly installed on the outer surface of the inner layer pipe, and the top end is movably connected to the inner wall of the outer layer pipe. Through the axial sliding of the inner and outer layer pipelines, the present invention can, under the existing pipeline welding process conditions, first weld the inner layer pipe and then weld the outer layer pipe, without operations such as on-site repair of the pipeline insulation layer, avoiding structural discontinuity at the joints. At the same time, since a support structure rather than a filling structure is adopted between the inner and outer layers, the heat exchange area is reduced, and the thermal resistance between the inner and outer layers is increased. Since the space between the inner and outer layers is completely connected, vacuum pumping in the middle can be further adopted to further increase the thermal resistance and reduce heat loss.

Description

Technical Field

[0001] The present invention relates to the technology of thermal pipelines, and particularly to a double-layer composite casing that can slide axially and its connection method. Background Art

[0002] Central heating is of great significance for saving primary energy, improving energy utilization efficiency, enhancing the living quality of residents, and reducing urban environmental pollution. Thermal pipelines are an important part of the central heating system for transporting heat media such as hot water and steam. Thermal pipelines refer to the heating pipelines that start from boiler rooms, direct-fired engine rooms, heating centers, etc. and lead from the heat source to the building heat inlets. The working pressure of the heating hot water medium is not higher than 2.5 MPa, and the working temperature does not exceed 200 °C; the working pressure of the heating steam medium is not higher than 1.6 MPa, and the working temperature does not exceed 350 °C. Reducing the heat loss of thermal pipelines is the key to improving the heat transfer efficiency of the heat network and the efficiency of the entire heating system. For example, the annual heating cost of a small industrial park's heat network is about 80 million yuan. For every 1% reduction in the heat loss of the pipeline network, about 800,000 yuan can be saved.

[0003] Currently, thermal pipelines mainly adopt the structural form of multi-layer insulation composite pipes, that is, an inner metal pipe, an intermediate insulation layer, and an outer metal pipe. Among them, the inner metal pipe plays the role of withstanding internal pressure, the intermediate insulation layer provides pipeline thermal resistance and reduces pipeline heat loss, and the outer metal pipe plays the roles of protection and withstanding the external pressure of the soil when buried. However, such insulation pipes have a high cost, large heat loss at the pipeline joints, and relatively large overall heat loss of the pipeline. Taking the thermal pipeline with a diameter of D600 in an industrial park as an example, the thickness of its insulation layer reaches more than 200 mm, the outer diameter of the pipeline exceeds 1 meter, the cost of every 9 meters of pipeline exceeds 100,000 yuan, and the overall equivalent thermal conductivity is about 0.07 W / (m²·°C). In addition, during on-site connection, it is necessary to first strip the insulation layer of the finished pipe fittings, weld the inner metal pipes, and then re-wrap the insulation layer. This operation results in complex processes, time-consuming and laborious. If the newly wrapped insulation layer is not properly processed, the equivalent thermal conductivity at the joint will exceed 0.2 W / (m²·°C), causing relatively large heat loss.

[0004] Therefore, the present invention intends to provide a new-structured insulation composite pipe, by changing the connection method of the traditional composite casing, improving the joint connection efficiency, and avoiding heat loss caused by the installation of traditional heating pipelines. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a double-layer composite casing that can slide axially and its connection method.

[0006] To solve the above technical problem, the solution adopted by the present invention is:

[0007] Provided is a double-layer composite sleeve that can slide axially, including an inner layer tube and an outer layer tube installed coaxially and nested; at least two sets of support and sliding mechanisms perpendicular to the axial direction are provided between the inner layer tube and the outer layer tube;

[0008] The support and sliding mechanism has any one of the following structures:

[0009] (1) The support and sliding mechanism includes at least 3 radial support members evenly arranged in the circumferential direction. The radial support member is composed of a support rod and a sliding member. The bottom end of the support rod is fixedly installed on the outer surface of the inner layer tube, and the sliding member is arranged at the top end of the support rod and is in contact with the inner wall of the outer layer tube; or,

[0010] (2) The support and sliding mechanism is composed of a support ring and a sliding member. The bottom of the support ring is fixedly sleeved on the outer surface of the inner layer tube, and several sliding members are evenly arranged on the top of the support ring in the circumferential direction and are in contact with the inner wall of the outer layer tube.

[0011] In the present invention, the sliding member is a roller, a ball bearing or a cylindrical roller bearing.

[0012] In the present invention, the inner layer tube and the outer layer tube have the same axial length.

[0013] In the present invention, the number of sliding members of each group of support and sliding mechanisms is equal, and the sliding members in different groups are arranged parallel to each other axially.

[0014] In the present invention, the inner layer tube is an inner layer tube made of metal material; the outer layer tube is a steel pipe, a thermoplastic reinforced plastic composite pipe, a steel wire wound reinforced polyethylene pipe or a plastic pipe; the support rod is a support rod made of polytetrafluoroethylene (PTFE), polyphenyl ester (Ekonol), polyimide (PI), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), glass wool or glass fiber material.

[0015] In the present invention, the bottom end of the support rod or the support ring is fixed on the outer surface of the inner layer tube by welding or bolt fastening.

[0016] The present invention further provides a connection method for the aforementioned double-layer composite sleeve, including the following steps:

[0017] (1) Transport the double-layer composite sleeve to the installation site, and hoist and position two adjacent double-layer composite sleeves to be connected;

[0018] (2) Drag the outer layer tube axially so that the inner layer tube and the outer layer tube are misaligned, exposing the interface part of the inner layer tube to be welded;

[0019] (3) Perform welding operation on the inner layer tube, and then push the outer layer tube back to perform welding operation on the outer layer tube.

[0020] In the present invention, according to the requirements of the inner layer pipe for the welding space, if the inner layer pipe can complete the welding operation from one side, the weld of the outer layer pipe and the weld of the inner layer pipe are located at the same axial position; if the inner layer pipe cannot complete the welding operation from one side, the weld of the outer layer pipe and the weld of the inner layer pipe maintain a sufficient axial distance (i.e., offset) to ensure that the inner layer pipe has sufficient welding operation space.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] In the present invention, through the axial sliding of the inner and outer layer pipes, under the existing pipeline welding process conditions, the inner layer pipe can be welded first, and then the outer layer pipe can be welded, without the need for on-site repair of the pipeline insulation layer and other operations, avoiding structural discontinuity at the joints. At the same time, since a support structure rather than a filling structure is adopted between the inner and outer layers, the heat exchange area is reduced, and the thermal resistance between the inner and outer layers is increased. Since the space between the inner and outer layers is completely connected, vacuum pumping in the middle can be further adopted to further increase the thermal resistance and reduce heat loss. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of an axially slidable double-layer composite casing;

[0024] Figure 2 is Figure 1 a radial cross-sectional view of the double-layer composite casing in

[0025] Figure 3 a schematic structural diagram of a double-layer composite casing with more support structures;

[0026] Figure 4 is a relative position diagram of the double-layer composite casing before installation;

[0027] Figure 5 is a schematic diagram of the double-layer composite casing after welding is completed. Detailed Description of the Invention

[0028] The following combines the drawings to describe the specific implementation manners of the present invention in detail.

[0029] The axially slidable double-layer composite casing includes an inner layer pipe 1 and an outer layer pipe 2 which are coaxially nested and installed, and both have the same axial length. At least two groups of support sliding mechanisms perpendicular to the axial direction are arranged between the inner layer pipe 1 and the outer layer pipe 2, and the support sliding mechanism has any one of the following structures:

[0030] (1) The support sliding mechanism includes at least 3 radially supporting members (such as 3, 4, 6) arranged evenly in the circumferential direction, Figure 2As shown, there are 4 radial support members. The radial support member is composed of a support rod 3 and a sliding member 4. The bottom end of the support rod 3 is fixedly installed on the outer surface of the inner layer tube 1, and the sliding member 4 is arranged at the top end of the support rod 3 and is in contact with the inner wall of the outer layer tube 2; or,

[0031] (2) The support sliding mechanism is composed of a support ring and a sliding member. The bottom of the support ring is fixedly sleeved on the outer surface of the inner layer tube 1, and several sliding members 4 are evenly arranged along the circumferential direction on the top of the support ring and are in contact with the inner wall of the outer layer tube 2.

[0032] When the inner layer tube 1 is made of metal, the bottom end of the support rod 3 or the support ring is preferably fixed on the outer surface of the inner layer tube 1 by welding (bolted fastening can also be selected). The number of sliding members 4 in each group of support sliding mechanisms is equal, and the sliding members 4 in different groups are arranged parallel to each other along the axial direction. The sliding member 4 can be a roller, a ball bearing or a cylindrical roller bearing, which is used to reduce the sliding friction of the outer tube along the axial direction.

[0033] Axially, N support sliding mechanisms can be arranged at equal intervals according to the diameter and external pressure resistance stiffness requirements of the outer layer tube 2, where N≥2 ( Figure 1 As shown in the structure with N = 2, Figure 3 As shown in the structure with N = 4). The support sliding mechanisms are distributed along the axial direction and are arranged parallel to each other, which are used to isolate and support the outer layer tube 2, and at the same time improve the external pressure resistance performance of the outer layer tube 2. The space (air or evacuated) between the inner layer tube 1 and the outer layer tube 2 plays a heat insulation role to reduce the heat transfer between the inner and outer layer tubes.

[0034] For application scenarios below 200°C, the support rod 3 can be made of several high-temperature resistant and low-thermal conductivity polymers such as polytetrafluoroethylene (PTFE), polyphenyl ester (Ekonol), polyimide (PI), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), etc.; for application scenarios above 200°C, the support rod 3 can be made of high-temperature resistant materials such as glass wool and glass fiber.

[0035] The outer layer tube 2 can be made of a steel pipe, a thermoplastic reinforced plastic composite pipe, a steel wire wound reinforced polyethylene pipe (PSP) or a plastic pipe (such as a polyethylene pipe, a polypropylene pipe), etc. Among them, the steel pipe has high rigidity and a large thermal conductivity coefficient, and is suitable for occasions with high vacuum degree and high external pressure resistance, but with low requirements for the thermal conductivity coefficient of the outer layer. The PSP is composed of steel and plastic, has medium rigidity and a small thermal conductivity coefficient, and is suitable for occasions with medium external pressure resistance and certain requirements for the heat insulation performance of the outer tube. The polyethylene pipe has low rigidity and a small thermal conductivity coefficient, and is suitable for occasions where the outer layer tube is not required to have external pressure resistance, but has certain requirements for the heat insulation performance.

[0036] For the axially slidable double-layer composite casing in the present invention, its specific connection method:

[0037] (1) Transport the assembled double-layer composite casing to the installation site, and hoist and position two adjacent sections of the double-layer composite casing to be connected.

[0038] (2) Drag the outer pipe 2 axially so that the inner pipe 1 and the outer pipe 2 are misaligned, exposing the interface part of the inner pipe 1 to be welded (as shown in Figure 4 ).

[0039] (3) Perform welding operations on the inner pipe 1 to produce the circumferential weld 5 shown in Figure 4 . Then push the outer pipe 2 back and perform welding operations on the outer pipe 2 to produce the circumferential weld 6 shown in Figure 5 .

[0040] According to the requirements of the inner pipe 1 for the welding space, the weld 6 of the outer pipe 2 can be located at the same axial position as the weld 5 of the inner pipe 1, or there can be a slight misalignment (as shown in Figure 5 ). If all welding of the inner pipe 1 can be completed from one side, the inner and outer welding parts can be at the same axial position; otherwise, the inner and outer welding parts can be slightly misaligned to ensure a larger welding space for the inner pipe 1.

[0041] When the outer pipe 2 is a composite pipe such as PSP or a polyethylene pipe, connection methods such as flange connection and electrofusion connection can also be used. At this time, flanges or electrofusion fittings can be installed at the pipe ends in advance as needed. After the welding of the inner pipe 1 is completed, push the outer pipe 2 back and connect it according to the conventional flange connection method or electrofusion welding method. Details are not described here.

Claims

1. A connection method for an axially slidable double-layer composite casing, comprising an inner layer tube and an outer layer tube coaxially nested and installed; Characterized in that, At least two sets of support and sliding mechanisms perpendicular to the axial direction are arranged between the inner layer tube and the outer layer tube, and at least two sets of support and sliding mechanisms are distributed along the axial direction and arranged parallel to each other; Each set of support and sliding mechanisms has any one of the following structures: (1) The support and sliding mechanism includes at least 3 radially supporting members evenly arranged in the circumferential direction. The radially supporting members are composed of a support rod and a sliding member. The bottom end of the support rod is fixedly installed on the outer surface of the inner layer tube, and the sliding member is arranged at the top end of the support rod and is in contact with the inner wall of the outer layer tube; or, (2) The support and sliding mechanism is composed of a support ring and a sliding member. The bottom of the support ring is fixedly sleeved on the outer surface of the inner layer tube, and several sliding members are evenly arranged on the top of the support ring in the circumferential direction and are in contact with the inner wall of the outer layer tube; Among them, when connecting two adjacent sections of the double-layer composite casing, the respective outer layer tubes are dragged in opposite axial directions, so that the inner layer tube and the outer layer tube are displaced, exposing the inner layer tube interface part to be welded; and when the inner layer tubes of two adjacent sections of the double-layer composite casing are welded, the respective outer layer tubes of the double-layer composite casing are axially reset to perform the outer layer tube welding operation. The axial movement distance of the respective outer layer tubes of two adjacent sections of the double-layer composite casing during the reset of their respective outer layer tubes is different from the distance that their respective outer layer tubes are dragged in opposite axial directions, so that the weld of the outer layer tube is staggered from the weld of the inner layer tube.

2. The method according to claim 1, Characterized in that, The sliding member is a roller, a ball bearing or a cylindrical roller bearing.

3. The method according to claim 1, Characterized in that, The inner layer tube and the outer layer tube have the same axial length.

4. The method according to claim 1, Characterized in that, The number of sliding members in each set of support and sliding mechanisms is equal, and the sliding members in different sets are arranged parallel to each other axially.

5. The method according to claim 1, Characterized in that, The outer layer tube is a plastic tube.

6. The method according to claim 1, Characterized in that, The inner layer tube is an inner layer tube made of metal material; the outer layer tube is a steel tube, a thermoplastic reinforced plastic composite tube or a steel wire wound reinforced polyethylene tube; the support rod is a support rod made of polytetrafluoroethylene, polyphenyl ester, polyimide, polyether ether ketone, polyphenylene sulfide, glass wool or glass fiber material.

7. The method according to claim 1, Characterized in that, The bottom end of the support rod or the support ring is fixed on the outer surface of the inner layer tube by welding or bolt fastening.

8. The method according to any one of claims 1-7, Characterized in that, Before connecting two adjacent sections of the double-layer composite casing, the following steps are further included: transporting multiple sections of the double-layer composite casing to the installation site, and hoisting two adjacent sections of the double-layer composite casing to be connected into place.

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