A field heat preservation device for district heating pipeline elbow, a design method and a construction method

Abstract

The application provides a field heat preservation device for a district heating pipeline elbow, a design method and a construction method. The application comprises a support tile sleeved on the outside of the elbow and an outer sleeve, the outer sleeve comprises an outer sleeve bevel joint unit and an outer sleeve joint unit, the support tile is used for mounting and positioning the outer sleeve bevel joint unit and has preset heat preservation performance, the outer sleeve bevel joint unit is obtained by separating the overall design of the outer sleeve bevel joint elbow pipe, comprises a corner with a certain angle, and is a basic outer sleeve unit composed of two outer sleeve bevel joint segments, the outer sleeve joint unit is an outer sleeve sleeve connecting the blank position between the two adjacent outer sleeve bevel joint units, and a foaming layer is arranged between the outer sleeve and the working steel pipe. The design method and the implementation method of the application make it possible to repair the elbow pipe in place with high sealing quality standards, and save the time cost and economic cost of heat preservation installation and in-place heat preservation replacement repair of the directly buried heat preservation pipeline elbow pipe.

Description

Technical Field

[0001] This invention relates to the field of pipe elbow insulation technology, and more particularly to a field insulation device, design method and construction method for district heating pipe elbows. Background Technology

[0002] In the construction and installation of pipelines for centralized heating / cooling systems, changes in pipeline routes due to obstacle avoidance or route alterations are frequent, necessitating the installation of elbows on-site to address these changes. For such unforeseen circumstances, prefabricated insulated elbows cannot meet the time constraints of construction; therefore, bare elbows must be installed and then insulated on-site.

[0003] In projects where insulation is repaired on damaged pipes, the issue of completing insulation fabrication on elbows or bends is frequently encountered.

[0004] On-site insulation of elbows or bends has always been an unavoidable issue in the construction or repair of centralized heating / cooling pipelines. This invention fills a gap in the industry by disclosing a systematic method for the design and implementation of on-site elbow and bend insulation. Summary of the Invention

[0005] In response to the aforementioned technical problems, a field insulation device for elbows in district heating pipelines, a design method, and a construction method are provided.

[0006] The technical means employed in this invention are as follows:

[0007] A field insulation device for a district heating pipeline elbow includes a support tile and an outer protective pipe fitted around the elbow. The outer protective pipe includes an outer protective pipe mitered joint unit and an outer protective pipe splice unit. The support tile is used for the installation and positioning of the outer protective pipe mitered joint unit and has a preset insulation performance. The outer protective pipe mitered joint unit is a basic outer protective pipe unit consisting of two outer protective pipe mitered joint sections, obtained by separating the outer protective pipe mitered joint bend according to the overall design of the elbow bend. It includes a certain angle of rotation. The outer protective pipe splice unit is an outer protective pipe sleeve that connects the blank space between two adjacent outer protective pipe mitered joint units. A foam layer is provided between the outer protective pipe and the working steel pipe.

[0008] Furthermore, the outer protective tube mitered joint unit includes an end section mitered joint unit and an intermediate mitered joint unit, wherein the end section mitered joint unit is a mitered joint unit at both ends, and the other mitered joint units serve as intermediate mitered joint units.

[0009] Furthermore, the supporting tile is an annular tile formed by the reaction molding of polyurethane material.

[0010] This invention also provides a design method for an on-site insulation device for elbows in district heating pipelines, comprising the following steps:

[0011] Step 1, Insulation Support Tile Design: Based on the insulation layer thickness requirements, outer protective pipe specifications, and the segmentation of the outer protective pipe's mitered section, design the specifications and dimensions of the support tile while ensuring minimal interference during installation.

[0012] Step 2, Design of the oblique bend of the outer protective pipe of the bend: Draw the steel bend fitting; based on the steel bend fitting, draw the steel bend fitting insulation outer protective pipe bend that is sleeved on the outside of it. The steel bend fitting insulation outer protective pipe bend is a curve fitted into several adjacent line segments; reserve the size of the joint section for the line segments of the steel bend fitting insulation outer protective pipe bend.

[0013] Step 3: Design of the mitered bend section of the outer protective pipe: Determine the size of the mitered unit of the outer protective pipe for the reserved joint section. The mitered unit of the outer protective pipe is the pipe section between the joint line of the adjacent outer protective pipe and the port of the adjacent mitered unit. Divide the entire outer protective pipe into end mitered units and intermediate mitered units. The end mitered units are the mitered units at both ends, and the other mitered units are the intermediate mitered units. Different size designs are made for the end mitered units and the intermediate mitered units.

[0014] Step 4, Outer Protective Tube Misalignment Unit Design: A complete end section misalignment unit or intermediate misalignment unit is made from an integrated template. The end section misalignment unit consists of one end section misalignment segment and one intermediate misalignment segment, and the intermediate misalignment unit consists of two intermediate misalignment segments.

[0015] Step 5: Design of the template for the outer sheath oblique joint section: Draw the unfolded diagrams of the middle oblique joint section and the end oblique joint section respectively.

[0016] Furthermore, in step 2, the design method for the bend includes the following steps:

[0017] Step 2.1: Divide the 90-degree center arc of the steel bend into equal parts on the steel bend drawing. Connect the centers of each division point and the center arc of the bend to obtain the radial center lines of several mitered sections of the outer protective pipe. During the division process, the following conditions must be met: 1) The 45-degree position of the arc corresponds to the mitered section, not the joint between the mitered sections; 2) The principle for determining the number of mitered sections is to ensure that the designed insulation support tile will not seriously interfere with the outer protective pipe.

[0018] Step 2.2: Draw the tangents of the arcs at the center of the bends passing through each of the equally divided points. The intersection of the tangents is the joint position of each bend section of the outer protective pipe.

[0019] Step 2.3: Make an equidistant line on both sides of the radius of the equidistant segment arc. The equidistant distance is 'a'. Measure the distance between the equidistant line on the inner short side of the outer protective tube mitered segment and the joint line of the adjacent mitered segment. Ensure that the distance is not less than 'a' to ensure that the patch sleeve and the mitered segment have sufficient overlap length during the subsequent patching installation process.

[0020] This invention also provides a construction method for an on-site insulation device for elbows in district heating pipelines, comprising the following steps:

[0021] Fabrication of support tiles: Based on the design dimensions of the finished support tiles, the foaming mold for the support tiles is designed, and the support tiles are fabricated using a polyurethane foaming machine;

[0022] Misaligned segment unfolding template fabrication: Based on the design parameters of the misaligned segments, the misaligned segment unfolding template is fabricated.

[0023] Fabrication of mitered joint sections: Weld the plates of the mitered joint sections to complete the fabrication of all the required intermediate and end sections;

[0024] Fabrication of the miter joint unit: A miter joint unit is made by welding two miter joint segments together. Specifically, two intermediate miter joint segments are connected to form an intermediate miter joint unit, and an intermediate miter joint segment and an end segment are connected to form an end miter joint unit.

[0025] Installation of support tiles: Install the support tiles on the bare steel bend pipe according to the positioning reference line;

[0026] Installation of the outer protective tube mitered joint unit: Install the first end section mitered joint unit with the support tile as the limit, and then complete the installation of the remaining mitered joint units;

[0027] Overall assembly: installation and welding of joints between miter joint units;

[0028] Foaming process: Polyurethane foaming material is injected into the cavity to be foamed using a high-pressure foaming machine to complete the foaming of all joint sections, and then all the miter joint sections are foamed.

[0029] Furthermore, during the fabrication of the miter joint segments and miter joint units, the joints are welded together using manual extrusion welding with temperature control function.

[0030] Furthermore, during the overall assembly process, the joint circumferential seam between the end section mitered joint unit and the first intermediate mitered joint unit is welded by electrofusion welding, and the joint sleeve is welded along the pipeline axis direction using a temperature-controlled manual extrusion welding device.

[0031] Furthermore, after the overall assembly is completed, an overall airtightness test is conducted on the outer protective tube of the bent pipe. Only after the test is passed can the foaming process be carried out.

[0032] Furthermore, after foaming is completed, the vent plug is removed, the injection hole is enlarged, and the foaming hole is hot-melted and welded using a hot-melt process and high-density polyethylene plug. After the hot-melt welding is completed and cooled, the surfaces of the plug and the outer protective tube material are ground and cleaned, and the plug is sealed and reinforced by a temperature-controlled extrusion welding device.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The outer protective pipe of the elbow / bend obtained by the implementation method of on-site insulation of district heating / cooling pipeline elbows / bends disclosed in this invention can achieve an overall airtightness test and can guarantee 100% airtightness test qualification. The design and implementation method of this invention makes it possible to maintain elbows / bends in place with high sealing quality standards, saving time and economic costs for the installation and in-place replacement and maintenance of insulation for directly buried insulated pipeline elbows / bends. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the positioning support half-tile in an embodiment of the present invention.

[0037] Figure 2 A schematic diagram of a DN1400R3.5D steel bend pipe fitting is shown in an embodiment of the present invention.

[0038] Figure 3 A schematic diagram of a DN1400R3.5D steel bend pipe fitting with thermal insulation outer protective pipe is shown in this embodiment of the invention.

[0039] Figure 4 This is a schematic diagram illustrating the reserved dimensions of the miter joint outer protective pipe splice section in an embodiment of the present invention.

[0040] Figure 5 This is a schematic diagram showing the dimensions of the outer protective tube oblique joint unit in an embodiment of the present invention.

[0041] Figure 6 This is a schematic diagram showing the centerline dimensions of the oblique joint segment of the outer protective tube oblique joint unit in an embodiment of the present invention.

[0042] Figure 7 The following is a diagram showing the unfolded template of the oblique joint segments of the outer protective tube in an embodiment of the present invention. The left diagram shows the unfolded template of each oblique joint segment in the middle, and the right diagram shows the unfolded template of the two end segments.

[0043] Figure 8 This is a schematic diagram of the material cutting template made according to the template unfolding diagram during the implementation of this embodiment of the invention.

[0044] Figure 9 This is a schematic diagram illustrating the fabrication of the intermediate oblique joint segment and the end oblique joint segment in an embodiment of the present invention.

[0045] Figure 10 This is a schematic diagram of the fabrication of the miter joint unit in an embodiment of the present invention, wherein the left figure is the middle miter joint unit and the right figure is the end miter joint unit.

[0046] Figure 11 This is a schematic diagram illustrating the measurement and marking of the support half-tile installation positioning points on a bare steel bend in an embodiment of the present invention.

[0047] Figure 12 This is a schematic diagram of marking positioning reference lines on a bare steel bent pipe in an embodiment of the present invention.

[0048] Figure 13 This is a schematic diagram of installing support tiles on a bare steel bent pipe according to a positioning reference line in an embodiment of the present invention.

[0049] Figure 14 This is a schematic diagram of the installation of the first end section oblique joint unit with the support tile as the limitation in an embodiment of the present invention.

[0050] Figure 15 This is a schematic diagram of the installation of all other oblique joint units with the support tile as the limit in an embodiment of the present invention.

[0051] Figure 16 This is a schematic diagram of the installation of the heating mesh at the electrothermal fusion joint between the end section oblique joint unit and the first intermediate oblique joint unit in an embodiment of the present invention.

[0052] Figure 17 This is a schematic diagram of the electrothermal welding of the circumferential seam between the end section miter joint unit and the first intermediate miter joint unit in an embodiment of the present invention.

[0053] Figure 18 This is a schematic diagram of the welding of the joint along the axial direction between the end section miter joint unit and the first intermediate miter joint unit in an embodiment of the present invention.

[0054] Figure 19 This is a schematic diagram illustrating the installation and welding of all the patch sleeves between the remaining miter joint units in this embodiment of the invention.

[0055] Figure 20 This is a schematic diagram illustrating the installation and welding of two end-section miter joint units with adjacent straight pipe splice sleeves in an embodiment of the present invention.

[0056] Figure 21 This is a schematic diagram of the overall airtightness test of the outer protective pipe of the bend in an embodiment of the present invention.

[0057] Figure 22 This is a schematic diagram of the foaming process for the joint section and the miter joint unit section in an embodiment of the present invention.

[0058] In the diagram: 1. Rigid polyurethane foam support tile; 2. Steel bend pipe fitting; 3. High-density polyethylene bend insulation mitered outer protective pipe; 4. Misered joint unit port of outer protective pipe; 5. Extruded weld bead; 6. Middle mitered joint segment; 7. End section mitered joint segment; 8. Extruded weld bead connecting the middle mitered joint segment; 9. Extruded weld bead in the axial direction of the end section mitered joint segment; 10. Virtual installation position of the mitered joint unit; 11. Positioning point of the support half tile; 12. Positioning reference line; 13. Electrofusion repair heating mesh; 14. Repair sleeve; 15. Extruded weld bead in the axial direction of the repair sleeve weld; 16. Pressure gauge for air tightness test; 17. Air injection hole for air tightness test of outer protective pipe. Detailed Implementation

[0059] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0062] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0063] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0064] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0065] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0066] For clarity and specificity, this invention will use a large-diameter bend with a diameter of DN1400 and a radius of curvature of R=3.5D as an example to disclose a method for on-site insulation design and implementation of bare elbow bends. In other optional embodiments, insulation design and implementation methods that can be performed using the method of this invention for bends of different diameters are all within the scope of protection of this invention. The method of this invention is the first of its kind in the industry, and there is no relevant technical information or patent information to draw upon. Therefore, the description of the method of this invention will omit comparisons with other methods.

[0067] This invention discloses an on-site insulation device for a district heating pipeline elbow, comprising a support tile 1 and an outer protective pipe 3 fitted over a steel elbow fitting 2 to be pre-insulated. The outer protective pipe includes an outer protective pipe miter joint unit and an outer protective pipe joint filling unit. The support tile is used for the installation and positioning of the outer protective pipe miter joint unit and has a preset insulation performance. The outer protective pipe miter joint unit is a basic outer protective pipe unit consisting of two miter joint sections, formed by separating the outer protective pipe miter joints of the elbow according to the overall design of the elbow elbow. The outer protective pipe joint filling unit is an outer protective pipe sleeve connecting the blank space between two adjacent outer protective pipe miter joint units. The sleeve is connected to the adjacent miter joint units in a sealed manner through an intelligent electrothermal fusion filling process. A foam layer is provided between the outer protective pipe and the working steel pipe.

[0068] As an optional implementation, the support tile is made of polyurethane. The polyurethane support tile is an annular tile formed by the reaction of polyurethane material, which has achieved the function of the support tile having a preset heat insulation performance. In other optional implementations, it can also be any material that can complete the pipe heat insulation.

[0069] The specific implementation method includes two main parts: design and on-site implementation.

[0070] Example 1

[0071] This embodiment provides a design method for an on-site insulation device for a district heating pipeline bend, including the following steps: design of insulation support tiles, design of the bend outer protective pipe slant joint bend, design of the slant joint section of the outer protective pipe slant joint bend, design of the outer protective pipe slant joint unit, and design of the outer protective pipe slant joint section unfolded template.

[0072] The support tile is designed based on the insulation layer thickness requirements, outer protective pipe specifications, and the segmentation of the outer protective pipe's oblique joints, ensuring minimal interference during installation. In this embodiment, the support tile is made of polyurethane material that meets the insulation requirements of bent pipes. Taking a DN1400 bent pipe as an example, the outer protective pipe specifications are Φ1656x25mm, the steel pipe outer diameter is Φ1420mm, and the dimensions of the finished support tile are as follows. Figure 1As shown, in actual operation, the support tile can be designed as a half-tile with a circumference of 180 degrees. The support tile is characterized by a 12.5mm high positioning facet on its outer edge, which serves as a positioning and limiting element for the oblique joint unit installation. Based on the finished design dimensions of the support tile, the foaming mold design for the 180° arc angle support half-tile is completed.

[0073] The design process of the outer protective pipe mitered bend includes drawing the bare steel bend, drawing the outer protective pipe bend, and drawing the reserved dimensions verification of the joint section.

[0074] The drawing of the bare steel bend is as follows: Figure 2 As shown. This invention uses the on-site insulation of a DN1400R3.5 specification bend as an example. The bend angle is 90°. The design method for bends of other specifications and angles is the same as the example in this invention.

[0075] The outer protective pipe bend is shown in the drawing. Figure 3 As shown. The design method involves dividing the 90-degree center arc of the steel bend into equal parts on the steel bend drawing. Connecting each division point with the center of the arc of the bend's center line yields several radial center lines for the mitered sections of the outer protective pipe. During the division process, the following conditions must be met: 1) The 45-degree position of the arc corresponds to the mitered section, not the joint between mitered sections; 2) The principle for determining the number of mitered sections is to ensure that the designed insulation support tile will not severely interfere with the outer protective pipe. (Attached) Figure 3 The number of equal divisions of the arc of the center line of the bend shown is 8. In other optional embodiments, the effect of any division is within the protection scope of the present invention. Next, draw the tangents of the arc of the center line of the bend passing through each division point. The intersection of each tangent is the joint position of each oblique section of the outer protective pipe bend.

[0076] The reserved dimensions of the joint section are verified and drawn as follows: Figure 4 As shown in the figure. The specific drawing method is as follows: Draw equidistant lines on both sides of the radius of the equally spaced points of the mitered segment arc, with an equidistant spacing of 'a'. Measure the distance between the equidistant line on the inner short side of the outer protective tube mitered segment and the joint line of the adjacent mitered segment, ensuring that this distance is not less than 'a'. In this embodiment, 'a' is taken as 150mm to ensure that the patch sleeve and the mitered segment have sufficient overlap length during the subsequent patch installation process. In the example figure, the overlap allowance is 251.057mm, which fully meets the overlap size requirements during patch installation.

[0077] The design of the mitered bend section of the outer protective pipe includes determining the size of the mitered unit of the outer protective pipe and determining the centerline size of the mitered section of the mitered unit of the outer protective pipe.

[0078] The determination of the outer sheath oblique joint unit size is as follows: Figure 5 As shown. According to Figure 4The bisectors are drawn to represent the edge lines of the outer sheath's mitered joint section, i.e., port 4 of the outer sheath's mitered joint unit in the figure. In this invention, the outer sheath's mitered joint section refers to the pipe segment between the outer sheath's joint line and the port of the adjacent mitered joint unit. The entire outer sheath is divided into end mitered joint units and intermediate mitered joint units. The end mitered joint units are the mitered joint units at both ends, and the other mitered joint units are intermediate mitered joint units. The outer sheath's mitered joint unit is an assembly consisting of two adjacent mitered joint sections welded together at a certain angle.

[0079] The determination of the centerline dimension of the oblique joint segment of the outer protective tube oblique joint unit is as follows: Figure 6 As shown. The centerline dimension is the distance between the joint line of the miter joint section and the edge line of the miter joint section on the centerline of the outer protective tube. The centerline length of the end section is longer than that of the middle section. In this embodiment, the centerline length of the end section is 482.608 mm, and the centerline length of the middle section is 332.608 mm. The centerline length of the miter joint section is the dimensional basis for the centerline height in the design of the miter joint section display stand template of the outer protective tube.

[0080] The outer protective tube mitered joint unit design refers to a basic installation unit in which two mitered joint segments are connected to each other to achieve an 11.25° rotation angle.

[0081] The design of the outer protective tube oblique joint section unfolded template is as follows: Figure 7 As shown. The unfolded sample diagram serves as the graphic and dimensional basis for creating the unfolded template. The unfolded diagrams of the intermediate and end sections of the mitered elbow are drawn according to the multi-segment mitered elbow sheet metal unfolding algorithm. In this embodiment, the line spacing is 162.8 mm, the centerline length of the intermediate section is 332.7 mm, and the centerline length of the end section is 482.7 mm.

[0082] Example 2

[0083] Based on the design parameters of Example 1, this example provides a construction method for an on-site insulation device for elbows in district heating pipelines, including the following steps:

[0084] On-site implementation includes: fabrication of support tiles, fabrication of templates for diagonal joint sections, cutting of diagonal joint sections, welding and forming of diagonal joint sections, welding of diagonal joint units, marking and positioning of bare steel bend pipe parts, installation of support tiles, installation and welding of diagonal joint units of outer protective pipe, installation and welding of joints between diagonal joint units, installation and welding of joints between diagonal joint sections of outer protective pipe and adjacent straight outer protective pipe, overall air tightness test of outer protective pipe of bend pipe, partial foaming of bend pipe, sealing and welding of foaming holes.

[0085] The support tiles are manufactured using a foaming mold and a high-pressure foaming machine for injection molding. The demolding time is typically 30 minutes. The foam density of the support tiles is not less than 60 kg / m³. 3After preparation, the edges are complete and there are no obvious visible voids.

[0086] like Figure 8 As shown, the oblique joint segmented unfolding template is made by using a CNC engraving machine to carve and cut the template onto a color steel plate or galvanized plate that meets the size requirements, based on a sheet metal unfolding template drawing. If this is not possible, the template can be precisely laid out and cut manually. The segmented unfolding template includes end segmented unfolding templates and intermediate segmented unfolding templates. Each template is marked with an extrusion welding pass 5 to facilitate subsequent processing.

[0087] The cutting of the miter joint sections is based on the unfolded template and the required quantity. Lines are drawn on a high-density polyethylene (HDPE) sheet that meets the thickness and material requirements to obtain the various miter joint sections. In this embodiment, each DN1400R3.5D outer sheath has 14 miter joint sections in the middle and 2 miter joint sections at the ends. After cutting the miter joint sections of the outer sheath, the center line and bottom edge should be clearly marked. The bottom edge is the edge line of the joint side port of the miter joint section.

[0088] The oblique segment welding forming is as follows: Figure 9 As shown. The ends of the mitered joint sections are beveled at a 30° angle. The mitered joint sections are then bent into circles, aligned on both sides, and clamped in place using auxiliary fixtures. The joints are then welded using manual extrusion welding with temperature control. Welding is completed for all required intermediate mitered joint sections 6 and end mitered joint sections 7.

[0089] The oblique joint unit is welded as follows: Figure 10 As shown. A miter joint unit is made by welding two miter joint segments together; two intermediate miter joint segments are connected together to form an intermediate miter joint unit; and one intermediate miter joint segment and one end segment are connected together to form an end segment miter joint unit. Before welding the miter joint segments, the welding edges are beveled at a 30° angle. The material surface next to the weld is ground and cleaned. The connection welding is completed using a temperature-controlled manual extrusion welding machine. The weld beads specifically include the extrusion weld bead 8 connecting the intermediate miter joint segments and the axial extrusion weld bead 9 of the end segment miter joint segments.

[0090] The steel bend pipe bare piece is marked and positioned as follows: Figure 11 As shown. The supporting half-tile positioning point 11 is the reference point for the supporting half-tile installation position, and the virtual installation position 10 of the miter joint unit is pre-set. According to the attached... Figure 11 Mark the positioning points as shown and measure the distance between adjacent positioning points. Determine and draw each positioning point in the horizontal direction of the bend, using a gantry crane and spirit level for centering during the measurement process. Draw positioning reference lines based on the positioning point markings, such as... Figure 12 As shown. The positioning reference line indicates the positioning position of the positioning support tile.

[0091] The support tile is installed as follows: Figure 13 As shown. Align the support half-tile with the positioning reference line 12 and install it, then temporarily lock it in place using a tightening strap.

[0092] The installation and welding of the outer protective tube oblique joint unit are as follows: Figure 14 and Figure 15 As shown. Following the required installation direction, cut the miter joint unit along the centerline and fit it onto the lower part of the support tile, ensuring both sides are aligned only with the positioning edge of the support tile. Temporarily tighten with a tightening tape. Mark the cut edge and make a second cut to ensure proper seam alignment, then temporarily tighten again. Beveling the seam and grinding the welding area, then use temperature-controlled manual extrusion welding to complete the joint welding. Complete the installation of all miter joint units in the same manner.

[0093] The installation and welding of the joint between the miter joint units includes surface treatment, installation of the heating mesh for circumferential welding, electrofusion welding, and axial welding.

[0094] The patch design specifies a patch spacing of 300mm, requiring a patch sleeve width of 500mm. The patch sleeve material is the same high-density polyethylene material as the miter joint unit.

[0095] The welding surface treatment involves cleaning and grinding both the welding surface of the patch sleeve and the welding surface of the miter joint unit, and then centering and overlapping the patch sleeve onto the miter joint unit.

[0096] The installation of the circumferential welding heating mesh is shown in Figure 16. After temporarily tightening and fixing the patch sleeve 14 and cutting it according to the marked lines, the welding heating mesh 13 for the overlapping area weld is installed. The welding heating mesh is a heating mesh that meets the welding process requirements of MITTEL's TSC.

[0097] The installation and welding of the joint between the oblique section of the outer protective pipe and the adjacent straight outer protective pipe are as follows: Figure 17 As shown. The electrofusion welding refers to the hot-melt welding between the high-density polyethylene materials of the patch sleeve and the miter joint unit, performed using the MITTEL TSC intelligent electrofusion welding machine.

[0098] The axially welded component, such as Figure 18 As shown: Implementation—Welding of the joint along the axial direction between the end section miter joint unit and the first intermediate miter joint unit. After cleaning, grinding, and beveling the weld material of the joint sleeve weld, the joint sleeve weld is completed 15mm along the pipeline axis using a temperature-controlled manual extrusion welding device. The joint welding and assembly between all miter joint units is completed in the same manner, as follows. Figure 19 As shown.

[0099] The installation and welding of the joint between the oblique section of the outer protective pipe and the adjacent straight outer protective pipe are as follows: Figure 20As shown: Implementation—Complete the installation and welding of the two end-section miter joint units with the adjacent straight pipe splice sleeves. Complete the splice installation and welding between the two end-section miter joint units and the outer protective pipe of the adjacent straight pipe in the same manner as the splice installation between the miter joint units.

[0100] The overall airtightness test of the outer protective pipe of the bend is as follows: Figure 21 As shown: Implementation – Overall airtightness test of the outer protective pipe of the bend. An airtightness test hole 17 is drilled on the completed oblique joint section or repair section of the outer protective pipe of the bend. An airtightness test plug and an airtightness test pressure gauge 16 are installed, and an air source is connected. The test pressure is controlled at 0.2 Bar and maintained for 2 minutes. During the pressure holding period, foam water is used to test the seal of all welds. After the airtightness test is passed, the airtightness test equipment is removed.

[0101] The segmented foaming process is divided into two steps: foaming of the joint section and foaming of the miter joint unit. Figure 22 As shown. First, foaming is performed on all the joint sections, then foaming is performed on all the miter joint sections. Before foaming, two foaming holes are made on the outer protective pipe at the required foaming location. Then, a high-pressure foaming machine is used to inject polyurethane foaming material into the required foaming cavity, and the foaming holes are temporarily sealed with vent plugs. Joint unit foaming is a process of injecting polyurethane foaming material into the space between the outer protective pipe and the working steel pipe of the joint unit through high-pressure injection to react and generate polyurethane insulation material. Miter joint unit foaming is a process of injecting polyurethane foaming material into the space between the outer protective pipe and the working steel pipe of the miter joint unit through high-pressure injection to react and generate polyurethane insulation material.

[0102] The foaming pore sealing and welding process refers to the following steps after foaming: removing the vent plug, enlarging the injection hole, and then using a hot-melt process and high-density polyethylene (HDPE) to hot-melt weld the foaming pores. After the hot-melt welding is completed and cooled, the surfaces adjacent to the sealing and outer sheath materials are ground and cleaned. A temperature-controlled extrusion welding device is then used to perform a sealing and strengthening weld on the sealing pores. The foaming pore welding and sealing process involves using a specialized frustum-shaped plug, made of a material compatible with the outer sheath, to hot-melt weld the foaming pores. A second extrusion welding process with automatic temperature control is then used to apply a secondary coating to the outer surface of the foaming pore sealing plug.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for an on-site insulation device for elbows in a district heating pipeline, characterized in that, Includes the following steps: Design of the outer protective bend of the bend: Draw the steel bend fitting; draw the steel bend fitting insulation outer protective bend that is sleeved on the outside of it, the steel bend fitting insulation outer protective bend is composed of several adjacent line segments by curve fitting; reserve the size of the joint section for the line segments of the steel bend fitting insulation outer protective bend. Design of the mitered bend section of the outer protective pipe: The dimensions of the mitered bend unit of the outer protective pipe are determined based on the reserved joint section. The mitered bend section of the outer protective pipe refers to the pipe section between the joint line of adjacent outer protective pipes and the port of the adjacent mitered bend unit. The mitered bend unit of the outer protective pipe is formed by welding two adjacent mitered bend sections of the outer protective pipe together with a certain angle. The entire outer protective pipe is divided into end section mitered bend units and intermediate mitered bend units. The end section mitered bend units are the mitered bend units at both ends, and the other mitered bend units are intermediate mitered bend units. Different dimensions are designed for the end section mitered bend units and the intermediate mitered bend units. Outer sheath oblique joint unit design: The end section oblique joint unit consists of one end section oblique joint segment and one intermediate oblique joint segment, and the intermediate oblique joint unit consists of two intermediate oblique joint segments; Outer sheath mitered section unfolded template design: Draw unfolded diagrams of the intermediate mitered section and the end section mitered section respectively; Insulation support tile design: Based on the insulation layer thickness requirements, outer protective pipe specifications, and the segmentation of the outer protective pipe's mitered section, the specifications and dimensions of the support tile are designed to ensure minimal interference during installation.

2. The design method according to claim 1, characterized in that, The design method for pipe bends includes the following steps: On the steel bend drawing, the 90-degree center arc of the steel bend is divided into equal parts. Connecting each division point with the center of the arc of the bend's center line yields several radial center lines of the mitered sections of the outer protective pipe. During the division process, the following conditions must be met: 1) The 45-degree position of the arc corresponds to the mitered section, not the joint between the mitered sections; 2) The principle for determining the number of mitered sections is to ensure that the designed insulation support tile will not seriously interfere with the outer protective pipe. Draw the tangents to the center arc of the bend that passes through each of the equally divided points. The intersection of the tangents is the joint position of each oblique section of the outer protective pipe bend. Make an equidistant line on both sides of the radius of the equidistant segment arc. The equidistant distance is 'a'. Measure the distance between the equidistant line on the inner short side of the outer protective tube mitered segment and the joint line of the adjacent mitered segment. Ensure that the distance is not less than 'a' to ensure that the patch sleeve and the mitered segment have sufficient overlap length during the subsequent patching installation process.

3. A construction method for an on-site insulation device for a district heating pipeline elbow based on the design method described in claim 1 or 2, characterized in that, Includes the following steps: Fabrication of support tiles: Based on the design dimensions of the finished support tiles, the foaming mold for the support tiles is designed, and the support tiles are fabricated using a polyurethane foaming machine; Misaligned segment unfolding template fabrication: Based on the design parameters of the misaligned segments, the misaligned segment unfolding template is fabricated. Fabrication of mitered joint sections: Weld the plates of the mitered joint sections to complete the fabrication of all the required intermediate and end sections; Fabrication of the miter joint unit: A miter joint unit is made by welding two miter joint segments together. Specifically, two intermediate miter joint segments are connected to form an intermediate miter joint unit, and an intermediate miter joint segment and an end segment are connected to form an end miter joint unit. Installation of support tiles: Install the support tiles on the bare steel bend pipe according to the positioning reference line; Installation of the outer protective tube mitered joint unit: Install the first end section mitered joint unit with the support tile as the limit, and then complete the installation of the remaining mitered joint units; Overall assembly: installation and welding of joints between miter joint units; Foaming process: Polyurethane foaming material is injected into the cavity to be foamed using a high-pressure foaming machine to complete the foaming of all joint sections, and then all the miter joint sections are foamed.

4. The construction method according to claim 3, characterized in that, During the fabrication of the miter joint segments and miter joint units, the joints are welded together using manual extrusion welding with temperature control.

5. The construction method according to claim 3, characterized in that, During the overall assembly process, the joint circumferential seam between the end section mitered joint unit and the first intermediate mitered joint unit is welded by electrofusion welding, and the joint sleeve is welded along the pipeline axis by a temperature-controlled manual extrusion welding device.

6. The construction method according to claim 3, characterized in that, After the overall assembly is completed, an overall airtightness test is conducted on the outer protective tube of the bent pipe. Only after the test is passed can the foaming process be carried out.

7. The construction method according to claim 3, characterized in that, After foaming, the vent plug is removed, the injection hole is enlarged, and the foaming hole is hot-melted and welded using a hot-melt process and high-density polyethylene plug. After the hot-melt welding is completed and cooled, the surfaces of the plug and the outer protective tube material are ground and cleaned. The plug is then sealed and reinforced using a temperature-controlled extrusion welding device.

8. A field insulation device for a district heating pipeline elbow obtained by the construction method according to any one of claims 4 to 7, characterized in that, The device includes a support tile and an outer protective tube fitted onto the outside of the elbow. The outer protective tube includes an outer protective tube mitered joint unit and an outer protective tube splice unit. The support tile is used for the installation and positioning of the outer protective tube mitered joint unit and has a preset thermal insulation performance. The outer protective tube mitered joint unit is a basic outer protective tube unit consisting of two outer protective tube mitered joint sections, obtained by separating the outer protective tube mitered joint bend according to the overall design of the elbow bend. It includes a certain angle of rotation. The outer protective tube splice unit is an outer protective tube sleeve that connects the blank space between two adjacent outer protective tube mitered joint units. A foam layer is provided between the outer protective tube and the working steel pipe.

9. The on-site insulation device for district heating pipeline elbows according to claim 8, characterized in that, The outer protective tube mitered joint unit includes an end section mitered joint unit and an intermediate mitered joint unit, wherein the end section mitered joint unit is a mitered joint unit at both ends, and the other mitered joint units are intermediate mitered joint units.

10. The on-site insulation device for district heating pipeline elbows according to claim 8, characterized in that, The supporting tile is a ring-shaped tile formed by the reaction of polyurethane material.

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