A method for manufacturing prefabricated overhead insulated pipe and prefabricated direct-buried insulated pipe

Abstract

This invention relates to a method for manufacturing a prefabricated overhead insulated pipe, comprising the steps of: fitting a corrugated pipe onto the outer surface of the working pipe; fabricating an insulation layer on the surface of the limiting pipe; and fitting a polyurethane layer and a metal outer sheath onto the surface of the insulation layer. This invention also relates to a method for manufacturing a prefabricated direct-buried insulated pipe. The beneficial effects of this invention are: improved operational efficiency of the heating network; good insulation of the heating network, preventing heat loss due to condensation; the use of corrugated pipes to overcome changes in the gap width between the working pipe and the limiting pipe due to thermal expansion and contraction of the working pipe; the three-layer insulation layer, which increases hardness and shields the heat conduction through the gaps, greatly reducing heat loss; and the use of a superhydrophobic insulation coating as a heat-insulating layer, further improving the insulation effect of the heat transmission pipeline in the power plant and preventing increased displacement of the insulation material due to thermal expansion and contraction of the working pipe.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation pipe technology, and particularly relates to a method for manufacturing a prefabricated overhead thermal insulation pipe and a prefabricated direct-buried thermal insulation pipe. Background Technology

[0002] With increasingly severe environmental problems and higher requirements for energy conservation and emission reduction, the construction of thermal power plants and their supporting heating networks has developed rapidly, with the scale of heating networks becoming larger and the pipelines becoming longer. Thermal power plants supply heat to the heating network through pipelines. Due to temperature differences along the pipelines, heat exchange occurs with the external environment. Heat is conducted through the insulation layer outside the pipeline, and the outer surface of the insulation layer then releases heat to the surrounding environment through convection and radiation.

[0003] Steam exits the power plant and enters the heating network to reach users. The steam temperature continuously decreases along the pipeline. The superheat of the steam also continuously decreases until it becomes saturated steam. The superheated steam upstream dissipates heat, its enthalpy decreases, and its temperature drops, but the steam remains superheated. However, the saturated steam downstream does not exhibit this behavior. The heat loss of saturated steam is not manifested as a temperature decrease, but rather as the formation of condensate. Once condensate forms in the pipeline, it must be drained, and this drained condensate contains a considerable amount of heat. For heating networks lacking insulation, with detached outer shells, and exposed steam pipes, the heat loss of the pipeline can increase to 50 to 100 times that of normally insulated pipelines.

[0004] In existing technologies, if insulation tiles are assembled piece by piece during insulation construction, numerous circumferential and longitudinal seams will exist between them. If insulation felt is used, wrapping it layer by layer around the steel pipe, although the gaps between the steel pipe and the felt are fewer than with insulation tiles, gaps still exist. These insulation gaps are inherently formed during construction. Therefore, insulation layer breakage is prone to occur on pipe supports. Regardless of whether cotton felt or tiles are used to wrap the pipes, numerous significant insulation gaps will form after steam is supplied to the pipeline network. Areas with severe insulation gaps can be equivalent to exposed steam pipes. Rigid insulation materials such as calcium silicate tiles are prone to cracking and pulverizing due to thermal displacement during unit start-up and shutdown, pipe vibration during operation, and long-term high-temperature use, forming thermal bridges and significantly increasing heat loss. Summary of the Invention

[0005] To avoid the increase in displacement of the insulation material due to thermal expansion and contraction of the working pipe and to reduce heat loss, the present invention provides a method for manufacturing a prefabricated overhead insulation pipe and a prefabricated direct-buried insulation pipe.

[0006] A method for manufacturing a prefabricated overhead insulated pipe includes the following steps:

[0007] Step 1: Install a limiting tube on the outer surface of the working tube. The limiting tube is made of corrugated pipe.

[0008] Step 2: Spray heat insulation coating on the surface of the limiting tube to form heat insulation coating layer A; place an intermediate heat insulation layer on the surface of heat insulation coating layer A, and continue to spray heat insulation coating on the surface of the intermediate heat insulation layer to form heat insulation coating layer B; let stand for a set time until the intermediate heat insulation layer is firmly bonded to the heat insulation coating layers on its upper and lower surfaces to form an integrated heat insulation layer.

[0009] Step 3: Apply a polyurethane layer to the surface of the insulation layer, and then apply a metal outer sheath to the surface of the polyurethane layer to obtain a prefabricated overhead insulation pipe.

[0010] Preferably, the heat insulation coating layer used in step 2 is a superhydrophobic heat insulation coating.

[0011] A method for manufacturing prefabricated direct-buried insulated pipes using a prefabricated overhead insulated pipe manufacturing method includes the following steps:

[0012] Step 1: Select an outer protective pipe with a diameter larger than that of the prefabricated overhead insulation pipe, and fix a horizontal plate at the bottom of the outer protective pipe; along the length of the outer protective pipe, make multiple slide rails on the inner wall of the outer protective pipe, and the multiple slide rails are evenly distributed on the inner wall of the outer protective pipe. No slide rails are set on the inner wall of the outer protective pipe below the horizontal plate.

[0013] Step 2: Connect multiple prefabricated overhead insulation pipes end to end with sealing components to form a sealed whole, and fix the No. 1 ring and the No. 2 ring on the outer wall of each prefabricated overhead insulation pipe.

[0014] Step 3: Set a support at the bottom of the No. 1 ring sleeve, and evenly fix multiple sets of pulleys that are symmetrical in the length direction of the outer protective tube on the outer circumference of the No. 2 ring sleeve;

[0015] Step 4: Install multiple prefabricated overhead insulation pipes connected end to end into the outer protective pipe; during installation, first put the multiple prefabricated overhead insulation pipes into the outer protective pipe; then adjust the position of the multiple prefabricated overhead insulation pipes, place the support at the bottom of the No. 1 ring on the horizontal plate, and install the multiple sets of pulleys on the No. 2 ring into their corresponding slide rails located on the inner wall of the outer protective pipe to obtain the prefabricated direct buried insulation pipe.

[0016] Preferably, the number of No. 1 rings and No. 2 rings on the multiple prefabricated overhead insulation pipes formed in step 2 are roughly equal.

[0017] Preferably, in step 4, the multiple slide rails on the inner wall of the outer protective tube correspond to the positions of the pulleys at various locations and their shapes match.

[0018] The beneficial effects of this invention are as follows: The prefabricated overhead insulated pipe and prefabricated direct-buried insulated pipe produced by this invention have a significant impact on the operating efficiency of the heating network. The heating network has good insulation properties, which can effectively prevent heat loss due to condensation. The prefabricated overhead insulated pipe produced by this invention overcomes the change in gap width between the working pipe and the limiting pipe caused by thermal expansion and contraction of the working pipe by setting a limiting pipe. The three-layer insulation layer set by this invention increases the hardness and shields the heat conduction of the gap, which can greatly reduce the heat loss. This invention also uses a superhydrophobic insulation coating as a heat insulation coating layer to further improve the heat insulation effect of the heat transmission pipeline of the thermal power plant and avoid the increase in displacement of the insulation material caused by thermal expansion and contraction of the working pipe. Attached Figure Description

[0019] Figure 1 A schematic diagram of the cross-section of a prefabricated overhead insulated pipe;

[0020] Figure 2 A cross-sectional view of the prefabricated direct-buried insulated pipe at the lateral displacement component;

[0021] Figure 3 This is a cross-sectional view of the prefabricated direct-buried insulated pipe at the radial displacement component.

[0022] Explanation of reference numerals in the attached drawings: 1. Working pipe; 2. Limiting pipe; 3. Insulation layer; 4. Polyurethane layer; 5. Metal outer sheath; 6. Outer protective pipe; 7. Air layer; 8. Lateral displacement assembly; 9. Radial displacement assembly; 10. Prefabricated overhead insulation pipe; 13-1. Thermal insulation coating layer A3-1; 3-2. Intermediate thermal insulation layer; 3-3. Thermal insulation coating layer B3-3; 8-1. Horizontal plate; 8-2. Ring No. 1; 8-3. Support; 9-1. Ring No. 2; 9-2. Pulley. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0024] As one embodiment, the manufacturing method of prefabricated direct-buried insulated pipes includes the following steps:

[0025] Step 1: A corrugated pipe is movably fitted onto the outer surface of the working pipe 1. The special structure of the inner wall of the corrugated pipe is used to overcome the change in the gap width between the working pipe and the corrugated pipe due to the thermal expansion and contraction of the working pipe.

[0026] Step 2: Spray a heat-insulating coating onto the surface of the corrugated pipe to form a superhydrophobic heat-insulating coating, as described in the application No. 202010026317.8, "A Method for Preparing a Superhydrophobic Heat-Insulating Coating"; A middle heat-insulating layer 3-2 is then applied to the surface of the superhydrophobic heat-insulating coating, and a heat-insulating coating is further sprayed onto the surface of the middle heat-insulating layer 3-2 to form a superhydrophobic heat-insulating coating; The thickness of the middle heat-insulating layer meets the requirements, and the layer is left to stand for a set time until the middle heat-insulating layer 3-2 is firmly bonded to the superhydrophobic heat-insulating coatings on its upper and lower surfaces, forming an integrated heat-insulating layer 3, which increases hardness and shields the heat conduction of gaps, preventing heat loss;

[0027] Step 3: Apply a polyurethane layer 4 to the surface of the insulation layer 3, and then apply a metal outer sheath 5 to the surface of the polyurethane layer 4, resulting in the following: Figure 1 The prefabricated overhead insulation pipe 10 is shown.

[0028] Step 4: Select an outer protective pipe 6 with a diameter 10 mm larger than the prefabricated overhead insulation pipe, and fix a horizontal plate 8-1 at the bottom of the outer protective pipe 6; along the length of the outer protective pipe 6, make multiple slide rails on the inner wall of the outer protective pipe 6, and the multiple slide rails are evenly distributed on the inner wall of the outer protective pipe 6. No slide rails are set on the inner wall of the outer protective pipe 6 below the horizontal plate 8-1.

[0029] Step 5: Connect multiple prefabricated overhead insulation pipes 10 end to end to form a sealed whole, and fix the first ring 8-2 and the second ring 9-1 on the outer wall of each prefabricated overhead insulation pipe 10; the number of the first ring 8-2 and the second ring 9-1 on the multiple prefabricated overhead insulation pipes 10 are equal.

[0030] Step 6: Set a support 8-3 at the bottom of the first ring 8-2, and evenly fix multiple sets of pulleys 9-2 that are symmetrical in the length direction of the outer protective tube 6 on the outer circumference of the second ring 9-1; the slide rail corresponds to the position of each pulley 9-2 and the shape matches.

[0031] Step 7: Install multiple prefabricated overhead insulation pipes 10 connected end to end into the outer protective pipe 6; during installation, first fit the multiple prefabricated overhead insulation pipes 10 into the outer protective pipe 6; then adjust the position of the multiple prefabricated overhead insulation pipes 10, place the support 8-3 at the bottom of the first ring 8-2 on the horizontal plate 8-1, and install the multiple sets of pulleys 9-2 on the second ring 9-1 into the corresponding slide rails located on the inner wall of the outer protective pipe 6 to obtain the prefabricated direct-buried insulation pipe.

[0032] like Figure 2 and Figure 3As shown, the gap between the prefabricated overhead insulation pipe 10 and the outer protective pipe 6 forms an air layer 7. The horizontal plate 8-1 located inside the outer protective pipe 6, several first-ring sleeves 8-2 fitted on the prefabricated overhead insulation pipe, and supports 8-3 fixed to the bottom of the first-ring sleeves 8-2 and movable on the horizontal plate 8-1 together constitute a lateral displacement assembly 8. Several second-ring sleeves 9-1 fitted on the prefabricated overhead insulation pipe 10 and several pulleys located outside the second-ring sleeves 9-1 constitute a radial displacement assembly 9. The lateral displacement assembly 8 and the radial displacement assembly 9 allow the prefabricated direct-buried insulation pipe to move laterally and radially within the outer protective pipe 6, thereby preventing an increase in the displacement of the insulation material due to thermal expansion and contraction of the working pipe.

[0033] The following are two practical implementation scenarios for the prefabricated direct-buried insulated pipes produced in this embodiment:

[0034] The pipeline used is DN1200, with a bare pipe outer diameter D0 = 1220 mm, a pipeline length L = 30000 m, and a rated flow rate T = 700 t / h. The initial steam parameters are: temperature T1 = 260℃, pressure P1 = 2.0 MPa; the terminal allowable steam parameters are: temperature T2 = 215℃, pressure P2 = 1.6 MPa. Based on Xiamen's annual climate parameters: annual average temperature Ta = 20.6℃, wind speed w = 3.2 m / s.

[0035] The target temperature at the end of the pipeline is set at 215℃, and the target pressure at the end of the pipeline is set at 1.6MPa.

[0036] (I) Implementation Scenarios of Overhead Thermal Insulation

[0037] The prefabricated overhead insulated pipes produced in steps 1 to 3 of this embodiment are used as overhead transmission pipelines for thermal power plants. An 80mm aluminum silicate layer and a 200mm glass wool layer are used as insulation layers, with a total insulation thickness δ = 280mm.

[0038] Assuming the terminal temperature T2 = 230℃, the average steam temperature of the pipeline T = (T1 + T2) / 2 = 245℃. The actual pipeline terminal temperature is calculated according to the calculation method for composite insulation of pipelines in GB50264-2013 "Code for Design of Thermal Insulation Engineering for Industrial Equipment and Pipelines". The relevant data are shown in Table 1 below.

[0039] Table 1 Calculation Data for Pipeline Overhead Composite Insulation

[0040]

[0041]

[0042] Based on the data in the table above, the actual pipe end temperature is calculated to be 230.6℃, which is greater than or equal to the target pipe end temperature of 215℃. Therefore, it can be seen that the prefabricated overhead insulated pipe produced in this embodiment can meet the requirements and achieve a good insulation effect when used as an external overhead pipeline for thermal power plants.

[0043] (II) Implementation Scenarios of Direct Burial Insulation

[0044] The prefabricated direct-buried insulated pipe produced in this embodiment is used as an external transmission pipeline buried underground in a thermal power plant. It uses 10mm aerogel coating, 60mm aerogel pipe shell, 10mm aerogel coating and 50mm polyurethane, with a total insulation thickness δ=130mm.

[0045] Assuming the terminal temperature T2 = 240℃, the average steam temperature of the pipeline T = (T1 + T2) / 2 = 250℃. The actual terminal temperature of the pipeline is calculated according to the composite insulation calculation method in CJJ104T-2014 "Technical Specification for Direct-Buried Steam Pipelines for Urban Heating," neglecting the thermal resistance of the air layer. The relevant data are shown in Table 2 below.

[0046] Table 2 Calculation Data for Composite Insulation of Directly Buried Pipelines

[0047]

[0048]

[0049]

[0050] Based on the data in the table above, the actual pipe end temperature is calculated to be 241.18℃, which is greater than or equal to the target pipe end temperature of 215℃. Therefore, it can be seen that the prefabricated direct-buried insulated pipe produced in this embodiment can meet the requirements and achieve a good insulation effect when used as a direct-buried external transmission pipeline for thermal power plants.

Claims

1. A method for manufacturing a prefabricated overhead insulated pipe, characterized in that, Includes the following steps: Step 1: Install a limiting tube (2) on the outer surface of the working tube (1). The limiting tube (2) is made of corrugated pipe. Step 2: Spray heat insulation coating on the surface of the limiting tube (2) to form heat insulation coating layer A (3-1); place an intermediate heat insulation layer (3-2) on the surface of heat insulation coating layer A (3-1), and continue to spray heat insulation coating on the surface of the intermediate heat insulation layer (3-2) to form heat insulation coating layer B (3-3); let stand for a set time until the intermediate heat insulation layer (3-2) is firmly bonded to the heat insulation coating layers on its upper and lower surfaces to form an integrated heat insulation layer (3); Step 3: Apply a polyurethane layer (4) to the surface of the insulation layer (3), and apply a metal outer sheath (5) to the surface of the polyurethane layer (4) to obtain a prefabricated overhead insulation pipe (10).

2. The method for manufacturing the prefabricated overhead insulated pipe according to claim 1, characterized in that: The thermal insulation coating layer used in step 2 is a superhydrophobic thermal insulation coating.

3. A method for manufacturing prefabricated direct-buried insulated pipes using prefabricated overhead insulated pipes obtained by the method described in claim 1, characterized in that, Includes the following steps: Step 1: Select an outer protective pipe (6) with a diameter larger than that of the prefabricated overhead insulation pipe (10), and fix a horizontal plate (8-1) at the bottom of the outer protective pipe (6); along the length of the outer protective pipe (6), make multiple slide rails on the inner wall of the outer protective pipe (6), and the multiple slide rails are evenly distributed on the inner wall of the outer protective pipe (6). No slide rails are set on the inner wall of the outer protective pipe (6) below the horizontal plate (8-1); Step 2: Connect the ends of multiple prefabricated overhead insulation pipes (10) into a sealed whole by sealing parts, and fix the No. 1 ring sleeve (8-2) and the No. 2 ring sleeve (9-1) on the outer wall of each prefabricated overhead insulation pipe (10). Step 3: Set a support (8-3) at the bottom of the first ring sleeve (8-2), and evenly fix multiple sets of pulleys (9-2) that are symmetrical in the length direction of the outer protective tube (6) on the outer circumference of the second ring sleeve (9-1). Step 4: Install multiple prefabricated overhead insulation pipes (10) connected end to end into the outer protective pipe (6); during installation, first put the multiple prefabricated overhead insulation pipes (10) into the outer protective pipe (6); then adjust the position of the multiple prefabricated overhead insulation pipes (10), place the support (8-3) at the bottom of the first ring (8-2) on the horizontal plate (8-1), and install the multiple sets of pulleys (9-2) on the second ring (9-1) into the corresponding slide rails located on the inner wall of the outer protective pipe (6) to obtain the prefabricated direct buried insulation pipe.

4. The method for manufacturing prefabricated direct-buried insulated pipes according to claim 3, characterized in that: On the multiple prefabricated overhead insulation pipes (10) formed in step 2, the number of No. 1 ring sleeves (8-2) and No. 2 ring sleeves (9-1) are roughly the same.

5. The method for manufacturing pre-insulated pipes according to claim 3, characterized in that: In step 4, the multiple slide rails on the inner wall of the outer protective tube (6) correspond to the positions of the pulleys (9-2) at various locations, and their shapes match.

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