Method for connecting pipe heads of non-standard pipelines through interpenetration technology in pipeline

Abstract

The invention relates to the technical field of pipeline engineering repair, in particular to a method for connecting non-standard pipeline pipe heads through a penetrating technology in a pipeline, which comprises the following steps of: S100, determining the outer diameter size of a lining pipe after reducing and rebounding according to the inner diameter of an original pipeline; s200, the inner diameter size and the length of the electric hot melting sleeve are manufactured; s300, determining the thickness of the electric hot melting sleeve according to a pipeline conveying medium and conveying pressure; s400, a thick-wall pipe is manufactured, and a short circuit is cut out according to the size of the electric hot melting sleeve; s500, electric fuses of different specifications are additionally arranged at the two ends of the electric hot melting sleeve according to the thicknesses of the pipe fittings, and the wiring distance of the electric fuses is adjusted according to the technical requirements; and S600, the ends of the two lining pipes to be welded are arranged at the two ends of the electric hot melting sleeve respectively, welding is started, and the lining pipes and the electric hot melting sleeve are welded into a whole. The damaged pipeline can be conveniently and rapidly repaired, and the pipeline repairing efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline engineering repair, in particular to a method for connecting non-standard pipeline pipe heads by pipeline inlay technology. BACKGROUND

[0002] Pipeline repair refers to the treatment and repair of defects or damage of pipelines conveying fluids during operation to ensure the safe operation and prolong the service life of the pipelines.

[0003] In many fields such as oil, natural gas, water supply, and drainage, a large number of steel pipelines serve for a long time, and due to the influence of factors such as conveying medium and soil environment, the inner wall of the pipeline is prone to corrosion, wear and tear, etc., which leads to a decrease in pipeline performance, such as an increase in the risk of leakage, a decrease in conveying efficiency, etc., seriously affecting the safe operation and service life of the pipeline, and causing huge economic losses worldwide every year due to pipeline corrosion.

[0004] Traditional pipeline repair methods, such as pipe replacement, require large-scale excavation of the ground, have high construction costs, long construction periods, and can cause serious impact on the surrounding environment and traffic. For example, the coating corrosion prevention method, for pipelines that already have corrosion defects, the coating is difficult to effectively repair the damaged parts, and the durability of the coating also has certain problems, especially when repairing pipelines in cities, traditional methods may also face limited space, dense surrounding buildings, and other difficulties, making it difficult to carry out large-scale construction.

[0005] Therefore, the technical personnel in the field are committed to developing a method for connecting non-standard pipeline pipe heads by pipeline inlay technology, which facilitates the rapid repair of damaged pipelines and improves the pipeline repair efficiency. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a method for connecting non-standard pipeline pipe heads by pipeline inlay technology, which facilitates the rapid repair of damaged pipelines and improves the pipeline repair efficiency. The technical solution of the present application to solve the above technical problems is as follows: A method for connecting non-standard pipeline pipe heads by pipeline inlay technology, characterized in that it comprises the following steps: S100. Determine the outer diameter size of the inner lining pipe after the diameter reduction and rebound according to the original pipeline inner diameter; S200. Make the inner diameter size and length of the electric heat melting sleeve; S300. Determine the thickness of the electric heat melting sleeve according to the pipeline conveying medium and conveying pressure; S400. Make a thick-walled pipe and cut a short pipe according to the size of the electric heat melting sleeve; S500. Install electric melting wires of different specifications at both ends of the electric heat melting sleeve according to the pipe thickness, and adjust the wiring spacing of the electric melting wires according to the technical requirements; S600. Place the two ends of the inner liner pipes to be welded on the two ends of the electric heat fusion sleeve respectively, and start welding so that the inner liner pipe and the electric heat fusion sleeve are welded into one body.

[0007] The beneficial effects of adopting the above scheme are: determining the outer diameter of the inner liner pipe after shrinkage and rebound based on the inner diameter of the original pipeline can ensure good matching between the inner liner pipe and the original pipeline, so that the repaired pipeline is highly consistent with the original pipeline in terms of size, thereby ensuring the sealing and stability of the pipeline connection and effectively preventing problems such as fluid leakage; The thickness of the electric heat-melting sleeve is determined according to the pipeline conveying medium and conveying pressure, so that the electric heat-melting sleeve has sufficient strength and corrosion resistance under different working conditions to adapt to various complex working environments, such as pipelines conveying acidic, alkaline and other corrosive media or pipelines subjected to high pressure, extending the service life of the repaired pipeline and reducing subsequent maintenance costs; By placing the two ends of the liner pipe to be welded on either side of the electric heat-melt sleeve and initiating welding, the liner pipe and the heat-melt sleeve are welded together, achieving efficient and reliable pipe connection. Compared with traditional flange and threaded connections, welding connection methods can simplify the construction process, improve construction efficiency, reduce construction time and labor costs, while ensuring connection strength. It is particularly suitable for rapid construction at pipeline repair sites.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, before welding, the oxide layer and impurities on the insertion end of the liner pipe are cleaned with a scraper or alcohol, and the liner pipe and the electric heat fusion sleeve are coaxial during welding.

[0010] The beneficial effects of adopting the above further scheme are: cleaning the oxide layer and impurities can remove surface dirt, avoid welding defects such as slag inclusions and pores during the welding process, ensure the purity of the welding area, thereby improving the quality and strength of the welded joint, enhancing the pressure resistance and sealing of the pipeline connection, and reducing the risk of leakage or damage to the pipeline due to welding quality problems during operation.

[0011] Furthermore, after step S600, natural cooling is also included, and the natural cooling time is greater than or equal to thirty minutes.

[0012] The beneficial effect of adopting the above-mentioned further scheme is that the natural cooling process can gradually reduce the temperature of the welding area, avoiding the adverse effects of hardened structure and increased brittleness of the welded joint due to rapid cooling, thereby ensuring the mechanical properties of the welded joint, such as tensile strength, yield strength, impact toughness, etc., ensuring that the repaired pipeline connection has good comprehensive mechanical properties, can withstand various loads and stress changes during the operation of the pipeline, and reduce the possibility of accidents such as pipeline breakage in subsequent use.

[0013] Further, in step S600, the welding voltage is 50V to 60V, and the welding time is 800s to 950s.

[0014] The beneficial effect of the above further scheme is that the appropriate voltage and welding time ensure that the electric heating sleeve generates sufficient heat during welding to fully fuse the inner liner pipe and the electric heating sleeve, while avoiding problems such as overheating of welding, material burning, or insufficient welding due to excessively low voltage, ensuring the reliability and consistency of welding quality.

[0015] Further, after step S600, a pressure test is further included.

[0016] The beneficial effect of the above further scheme is that the pressure test can comprehensively check the sealing performance of the repaired pipe connection, timely find potential leakage risks such as welding defects, poor sealing, etc., ensure the sealing performance of the pipe during actual operation, prevent environmental pollution, resource waste, and safety accidents caused by fluid leakage, and ensure the safe and stable operation of the pipeline system.

[0017] Further, in step S500, the electric fuse is spirally wired, and the axial spacing δ between adjacent coils is (0.8~1.2)× the wall thickness of the electric heating sleeve.

[0018] The beneficial effect of the above further scheme is that the spiral wiring method can uniformly distribute the electric fuse inside the electric heating sleeve, ensure that the heat generated during welding can be uniformly transmitted to the welding area of the electric heating sleeve and the inner liner pipe, avoid local overheating or insufficient heating, improve the temperature uniformity of the welding area, thereby ensuring the consistency of the welding quality, and make the performance of the welded joint more stable and reliable.

[0019] Further, before step S600, the outer wall of the inner liner pipe port is polished at an angle of 15°±2° to form a tapered guide surface.

[0020] The beneficial effect of the above further scheme is that the design of the tapered guide surface can effectively guide the end of the inner liner pipe to be more easily inserted into the electric heating sleeve, reducing the difficulty of alignment during installation, especially in scenarios where the internal space of the pipeline is limited or the construction environment is complex, which can reduce the operation strength and difficulty of construction personnel, improve installation efficiency, ensure the smooth progress of the construction process, and shorten the repair time.

[0021] Further, in step S600, the temperature during the melting stage is maintained at 210℃±5℃, and the temperature during the pressure maintaining stage is reduced to below 80℃.

[0022] The beneficial effect of the further scheme is that the appropriate melting temperature helps to properly cool and solidify the welding area after the welding is completed, while avoiding the performance degradation of the material due to excessively high temperature or the forming quality of the welding part affected by excessively low temperature. Reasonable temperature control helps to reduce the thermal stress and deformation during welding, ensure the dimensional stability and geometric shape of the welded joint after cooling, and ensure the quality reliability and stability of the pipeline connection, thereby improving the safety and reliability of the entire pipeline system.

[0023] Further, in step S600, the inner liner pipe and the electrothermal melting sleeve are coaxially positioned by using the positioning clamp, and the coaxiality of the positioning clamp is less than 0.5 mm.

[0024] The beneficial effect of the further scheme is that the positioning clamp and the specific coaxiality requirement provide clear standards and basis for quality control during construction, which is convenient for construction personnel to operate and inspection personnel to detect, ensures that each pipeline connection meets the specified requirements, thereby improving the quality level of the entire pipeline repair project, ensuring that the pipeline system can operate safely and stably, and reducing the maintenance and repair workload due to quality problems in the later period. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The method for connecting the non-standard pipeline pipe end of the pipeline inner insertion technology of the present application is shown in the flow chart. DETAILED DESCRIPTION

[0026] The principles and characteristics of the present application are described below in conjunction with the drawings, and the examples are only used to explain the present application and are not used to limit the scope of the present application.

[0027] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "length", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "inner", "outer", "peripheral side", "circumferential" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the systems or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0028] In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly and specifically limited.

[0029] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] As shown in Figure 1 A method for connecting a non-standard pipeline pipe head by a pipe-in-pipe technology, comprising the following steps: S100. Determine the outer diameter size of the inner lining pipe after the diameter reduction and rebound according to the original pipe diameter; S200. Make the inner diameter size and length of the electric heating sleeve; S300. Determine the thickness of the electric heating sleeve according to the pipeline conveying medium and conveying pressure; S400. Make a thick-walled pipe and cut a short pipe according to the size of the electric heating sleeve; S500. Install different specifications of electric melting wires at both ends of the electric heating sleeve according to the thickness of the pipe fitting, and adjust the wiring spacing of the electric melting wires according to the technical requirements; S600. Clean the oxidation layer and impurities on the insertion end of the inner lining pipe with a scraper or alcohol before welding, and also includes polishing the outer wall of the inner lining pipe port at an angle of 15°±2° to form a tapered guide surface.

[0031] During welding, the inner lining pipe and the electric heating sleeve are coaxial, specifically, a positioning clamp is used to position the inner lining pipe and the electric heating sleeve coaxially, and the coaxiality of the positioning clamp is less than 0.5mm.

[0032] Place the two inner lining pipe ends to be welded at both ends of the electric heating sleeve respectively, and start welding to make the inner lining pipe and the electric heating sleeve into one body, wherein the welding voltage is 50V to 60V, the welding time is 800s to 950s, the temperature in the melting stage is maintained at 210℃±5℃, and the temperature in the pressure maintaining stage is reduced to below 80℃.

[0033] It also includes natural cooling, and the natural cooling time is greater than or equal to thirty minutes.

[0034] After natural cooling, it also includes pressure testing.

[0035] Example one 1. Determine the outer diameter size of the liner pipe after the shrinkage and rebound, select the inner diameter size and length of the electric heat shrink sleeve. According to the pipeline medium and pressure, select the thickness of the electric heat shrink sleeve (the inner diameter is 1mm-2mm larger than the non-standard pipe size). For reference: GB / T 13663.3 Polyethylene (PE) piping systems for water supply Part 3: Pipe fittings.

[0036] 2. Independently produce thick-walled pipes and cut short according to the size of the electric heat shrink sleeve.

[0037] 3. According to the thickness of the pipe fitting, install different specifications of electric melting wires at both ends of the electric heat shrink sleeve, adjust the wiring spacing of the electric melting wires according to the technical requirements, meet the connection of non-standard size electric heat shrink sleeve and non-standard size pipe fitting (thin-walled pipe), and refer to the relevant requirements of GB / T13663.3 Polyethylene (PE) piping systems for water supply Part 3: Pipe fittings.

[0038] 4. Set different heating power and heating time according to different pipe fitting specifications and sizes.

[0039] I. Welding process ‌Equipment inspection‌: Confirm that the electric melting welding machine, power cord, plug and other components are in good condition, and the power voltage is stable (it is recommended to use 220V / 50Hz power source, and the power cord should not exceed 20 meters).

[0040] ‌Material matching‌: Check if the specifications and types of pipe and pipe fitting meet the requirements, and ensure that the pipe port is flat (error less than 5mm).

[0041] ‌Environment preparation‌: Ensure that the working surface is stable to avoid shaking during welding.

[0042] II. Cleaning and processing pipe ‌Remove oxidation layer‌: Use a scraper or alcohol to clean the oxidation layer and impurities on the insertion end of the pipe, and ensure that the fusion area is clean.

[0043] ‌Mark the depth‌: Mark the depth of the pipe inserted into the pipe fitting on the pipe, and ensure that the pipe end is perpendicular to the axis.

[0044] III. Parameter setting Voltage and time‌: Set the welding parameters according to the pipe diameter and wall thickness. For example, for a 310*8 pipe, the voltage is 58V and the time is 880s. Constant voltage or constant current mode: Adjust the voltage, current or time through the welding machine menu (refer to the equipment manual).

[0045] ‌Special situation adjustment‌: When the ambient temperature is low, the heating time needs to be appropriately extended.

[0046] IV. Connection and welding Insert the pipe into the socket gently (avoid knocking it in, which can cause it to shift after heating and expanding). If the pipe is not aligned with the socket, use a straightener to secure it.

[0047] Connect the electrode: Insert the welding machine's output electrode into the socket's electrode post and ensure good contact.

[0048] Start the welding: Set the initial welding parameters according to the pipe specifications (e.g., for a 310*8 pipe, voltage 58V, time 880s), and press the start button to begin welding (the process can be paused, but the data will not be saved).

[0049] Five, cooling and inspection Natural cooling: After welding is complete, allow the pipe to cool naturally for at least 30 minutes (for pipes larger than DN200, extend the cooling time to 45 minutes). Do not use forced cooling.

[0050] Quality inspection: Check for any molten material that may have seeped out and perform a pressure test.

[0051] Summary of precautions Safety precautions: Avoid touching high-temperature components and wear protective gloves when operating the welding machine.

[0052] Maintenance requirements: Clean the welding machine after use and regularly inspect the components.

[0053] Stable power supply: If using a generator for power, wait until it is stable before starting the welding machine.

[0054] Key tips: The operation details of different brands of welding machines may vary slightly. Refer to the device manual for guidance and adjust the parameters according to the pipe specifications and environmental conditions.

[0055] Compared with the prior art: 1. It can save two thick-walled pipe welding processes, shorten the process flow, improve production efficiency, reduce labor intensity, reduce the number of posts, personnel, and equipment investment, reduce safety risks, and improve production efficiency.

[0056] 2. It breaks the limitation of the electric heat shrink sleeve being able to connect only with thick-walled pipes.

[0057] 3. The inner lining pipe is directly welded to the non-standard electric heat shrink sleeve at both ends without a step, and the pipe diameter remains unchanged.

[0058] 4. After installing the non-standard electric shrink sleeve on the pipe, the distance and frequency of the inner lining pipe's creeping in the steel pipe can be effectively reduced, thereby greatly reducing the occurrence of inner lining pipe folding and blocking.

[0059] Example Two Pipe parameter determination and material preparation Combined with a specific chemical pipeline repair site, the original pipeline inner diameter is 250mm, the wall thickness is 6mm, and the weak corrosive chemical medium is transported, and the working pressure is 1.0MPa. According to the inner diameter of the original pipeline, the outer diameter size of the inner lining pipe after the shrinkage and rebound of the inner lining pipe is 245mm, so as to ensure that the inner lining pipe and the original pipeline have a suitable interference fit and ensure the sealing and stability.

[0060] According to the selected outer diameter size of the inner lining pipe, an electric heating sleeve is made, the inner diameter size of which is 250mm and the length is 200mm. According to the pipeline conveying medium and pressure, the thickness of the electric heating sleeve is determined as 8mm according to the relevant standards and empirical formula, so as to meet the corrosion resistance and strength requirements.

[0061] A thick-walled pipe is independently produced, the outer diameter of which is 300mm and the wall thickness of which is 10mm. A length of 200mm is cut from the short pipe according to the size of the electric heating sleeve, so as to ensure the size matching of the connection with the electric heating sleeve.

[0062] Installation of electric heating sleeve and electric melting wire Different specifications of electric melting wires are installed at both ends of the electric heating sleeve according to the thickness of the thick-walled pipe. The electric melting wire with a diameter of 1.0mm and a spacing of 12mm is installed at one end of the pipe with a thickness of 8mm, and the electric melting wire with a diameter of 1.2mm and a spacing of 15mm is installed at the other end of the pipe with a thickness of 12mm. The spacing of the electric melting wire is adjusted according to the technical requirements, and special tools are used for accurate installation and adjustment, so as to ensure that the electric melting wire is evenly distributed inside the electric heating sleeve, meet the connection requirements of non-standard size electric heating sleeve and non-standard size pipe (thin-walled pipe), and provide good heating conditions for subsequent welding.

[0063] Welding process Equipment inspection and debugging: Before welding, carefully check whether the electric melting welding machine, power cord, plug and other parts are intact, ensure that the power voltage is stable at 220V / 50Hz, and the length of the power cord is controlled within 15 meters, so as to ensure the stability and reliability of power supply during welding. At the same time, the welding machine is preheated and calibrated to ensure that the output voltage and time control accuracy meet the requirements.

[0064] Material inspection and treatment: Check whether the specifications and types of pipe and pipe fittings meet the design requirements, confirm that the quality of the inner lining pipe and the thick-walled pipe is qualified, the pipe port is smooth, and the error is controlled within 3mm. Use a scraper and anhydrous alcohol to clean the oxidation layer and impurities at the insertion end of the inner lining pipe, so as to ensure that the surface of the fusion area is clean, free of oil stains and moisture, and at the same time, use special tools to polish the outer wall of the inner lining pipe port into a 15°±2° conical guide surface, so as to facilitate subsequent insertion and welding.

[0065] Parameter setting and adjustment: According to the specifications of the inner liner pipe and the electric heating sleeve, as well as the environmental conditions on site, the welding parameters are set. For the pipe size and material in this example, the welding voltage is set to 55V and the welding time is set to 900s. At the same time, select the appropriate constant voltage mode in the welding machine menu, and according to the equipment instructions and the actual situation on site, fine-tune the welding parameters to adapt to the possible environmental temperature changes and other special conditions on site.

[0066] Connection and welding operation: Insert the processed inner liner pipe into the electric heating sleeve gently, move slowly and evenly during the insertion process, avoid forcible knocking, and prevent displacement after heating expansion. During the insertion process, if the inner liner pipe and the electric heating sleeve are found to be misaligned, use a straightener to fix and adjust them in time to ensure that they are coaxial. Then, insert the welding machine output electrode into the electrode column at both ends of the electric heating sleeve accurately to ensure good contact, no looseness and loose connection. Press the confirmation key to start the welding process, and the welding machine will automatically heat and weld according to the preset parameters. During the welding process, do not stop the welding operation to ensure the continuity and stability of the welding quality. At the same time, arrange a person to observe the temperature change and equipment running state during the welding process, and handle abnormal situations in time.

[0067] Cooling and quality inspection After welding is completed, naturally cool for at least 40 minutes to ensure that the welding area is fully solidified and crystallized. Do not use forced cooling measures such as water cooling to avoid adversely affecting the performance of the welded joint. During the cooling process, keep the environment around the pipe stable to avoid external interference and vibration.

[0068] After cooling, conduct a comprehensive inspection of the welding quality. First, observe the appearance of the welding area, check for signs of molten material seepage, smooth surface, etc. If there are any abnormalities, further analysis and treatment are required. Then, conduct a pressure test by pressurizing the pipe system to 1.5 times the working pressure, i.e. 1.5MPa, and maintain the pressure for 30 minutes to observe the pressure change and whether there is any leakage at the pipe connection. If the pressure does not decrease significantly and there is no leakage, the welding quality is considered to be qualified and the pipe repair is completed, and the pipe can be put into use.

[0069] In the description of the specification, the description using the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the particular feature, structure, material or characteristic following the term is included in at least one embodiment or example of the present application. The illustrative appearances of the above-mentioned terms in the specification do not necessarily refer to the same embodiment or example. Also, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Moreover, the terms "comprises", "comprising", "includes", "including", "contains", "containing" or the like are inclusive and are intended to mean that the contents, features, materials, or the like that are enumerated are contained in the application, but do not exclude the possibility that one or more other features, materials, or the like are also present.

[0070] The above description is merely illustrative of the application and is not to be taken in a limiting sense. Rather, the scope of the application disclosed herein is to be determined solely by the appended claims, along with the full range of equivalents to which such claims are entitled.

Claims

1. A method for connecting non-standard pipeline heads using pipeline insertion technology, characterized in that: The following steps are involved: S100. Determine the outer diameter of the liner after shrinkage and rebound based on the original inner diameter of the pipe; S200 production of electric melting sleeve inner diameter and length; S300. Determine the thickness of the electric heat-melting sleeve according to the pipeline conveying medium and conveying pressure; S400. Make thick-walled pipes and cut short circuits according to the size of the electric heat-melting sleeves; S500. Install different specifications of electric fuses at both ends of the electric heat-fusion sleeve according to the thickness of the pipe, and adjust the wiring spacing of the electric fuses in accordance with technical requirements; S600. Place the two ends of the inner liner pipes to be welded on the two ends of the electric heat fusion sleeve respectively, and start welding so that the inner liner pipe and the electric heat fusion sleeve are welded into one body.

2. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that In step S600, before welding, the oxide layer and impurities at the insertion end of the liner tube are cleaned with a scraper or alcohol. During welding, the liner tube and the electric hot melt sleeve are coaxial.

3. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that After step S600, natural cooling is also included, and the natural cooling time is greater than or equal to thirty minutes.

4. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that In step S600, the welding voltage is 50V to 60V, and the welding time is 800s to 950s.

5. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that ,After step S600, it also includes stress testing.

6. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that ,In step S500, the electric fuse adopts spiral wiring, and the axial spacing between adjacent coils δ = (0.8~1.2) × ,the wall thickness of the electric thermal fuse sleeve.

7. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that Before step S600, the outer wall of the liner pipe port is polished at an angle of 15°±2° to form a tapered guide surface.

8. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 1 is characterized in that ,In step S600, the temperature in the melting stage is maintained at 210℃±5℃, and the temperature in the pressure holding stage is reduced to below 80℃.

9. The method for connecting non-standard pipeline heads using the pipeline insertion technology according to claim 2 is characterized in that In step S600, a positioning fixture is used to coaxially position the inner liner pipe and the electric hot melt sleeve, and the coaxiality of the positioning fixture is less than 0.5mm.

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