Hydraulic forming water pipe eccentric joint of hollow pipe and preparation method of hydraulic forming water pipe eccentric joint

Abstract

The invention discloses a hydraulic forming water pipe eccentric connector of a hollow pipe and a preparation method of the hydraulic forming water pipe eccentric connector, and belongs to the field of fluid conveying pipelines. Comprising two water pipe eccentric pipes, the two ends of the two water pipe eccentric pipes fixedly communicate with water pipe heads, and the opposite ends of the water pipe heads fixedly communicate with threaded heads; the hollow pipe hydraulic forming water pipe eccentric connector has the core advantages that the dynamic adjusting function and the high-reliability structural design are combined, and the installation efficiency and the long-term use stability are remarkably improved. According to the innovation, through an integrated mechanism of mechanical linkage and visual feedback, an operator only needs to rotate a rotating ring of a single connector to drive a sliding plate to transversely move, a limiting plate is driven to slide in a sliding cavity, and therefore the axial offset of the two eccentric pipes is accurately controlled. The gradienter integrated on the sliding cavity can display the angle change of the pipeline in real time, eccentric distance adjustment and horizontal calibration are completed synchronously, and measurement errors and time loss caused by traditional step-by-step operation are avoided.

Description

Technical Field

[0001] The invention relates to fluid conveying pipeline technology, in particular to a hydraulically formed water pipe eccentric joint for a hollow pipe and a preparation method thereof. Background Art

[0002] Eccentric joints, as key connectors in fluid conveying systems such as municipal pipelines, petrochemicals, and industrial equipment, have long faced challenges such as low adjustment efficiency, poor sealing, and complex manufacturing processes. Traditional eccentric joints rely on casting or welding processes, which are prone to defects such as pores and pinholes within the cast structure. Welded joints, however, suffer from grain coarsening in the weld zone, resulting in a fatigue life reduction of over 50%. Leakage risk is significant in high-pressure (>10 MPa) or corrosive media, with statistics showing that 65% of welded joint failures are due to weld fatigue cracking. During installation, eccentricity compensation requires repeated adjustment of the flange bolt holes. Single-point adjustment takes up to 15-30 minutes, and the lack of a real-time leveling mechanism means manual errors can easily cause pipe tilt or stress concentration. In terms of manufacturing, traditional cutting processes utilize less than 40% of the material, while multiple welding or machining passes drive up costs. Fixed molds are difficult to adapt to custom 0.5-5 mm eccentricity requirements, and mold modification costs account for over 30% of the total cost, severely hindering product iteration. In terms of sealing performance, conventional rubber seals are prone to permanent deformation and failure under high-pressure alternating loads. Although metal cone seals are highly reliable, they require a machining accuracy of ≤0.05mm, which significantly increases costs. Traditional welded joints have a leakage rate as high as 12% at 1.3 times the design pressure, which cannot meet the requirements of high-end scenarios such as nuclear power. Although hydroforming technology has been tried in recent years for the manufacture of seamless pipe fittings, bottlenecks such as pipe wall thickness deviation greater than 15%, difficulty in forming complex eccentric structures, and lack of process monitoring still exist. This makes it difficult to achieve both dynamic adjustment and high reliability, restricting the widespread application of eccentric joints in complex fluid systems.

[0003] While recent attempts to utilize hydroforming technology to produce seamless pipes have addressed these challenges, issues such as uneven wall thickness distribution (deviations > 15%), difficulty in forming complex eccentric structures, and a lack of real-time process monitoring persist. Consequently, developing an eccentric joint with dynamic adjustment capabilities, high sealing performance, and efficient forming processes has become a pressing challenge in fluid connection technology. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide an eccentric water pipe joint that can dynamically adjust the eccentricity and synchronously calibrate the horizontality; another purpose of the present invention is to provide a hydraulic forming process that has high sealing, lightweight and pressure resistance.

[0005] Technical solution: A hydraulically formed eccentric water pipe joint for a hollow tube and a preparation method thereof, comprising two eccentric water pipe tubes, both ends of the two eccentric water pipe tubes being fixedly connected with water pipe heads, and the opposite ends of the water pipe heads being fixedly connected with threaded heads.

[0006] Furthermore, a rotation groove is provided on the outer side wall of the threaded head below, and the outer side wall of the rotation groove is rotatably connected to a rotating ring. The outer side walls of the two rotating rings are fixedly connected to a slide. The opposite ends of the slide are fixedly connected to a limiting plate. The outer side walls of the limiting plate are slidably connected to a sliding cavity, and the front surface of the sliding cavity is fixedly connected to a spirit level.

[0007] Furthermore, the outer side wall of the upper threaded head is threadedly connected with a locking ring.

[0008] Furthermore, the rotating circle includes an arc ring, and the number of the arc rings is two. The outer side walls of the two arc rings are fixedly connected with a fixed block with a hole, and the interiors of the two fixed blocks with holes are connected by bolt threads.

[0009] According to another aspect of the present invention, there is provided a hollow pipe hydroformed eccentric water pipe joint and a method for preparing the same, comprising the following steps:

[0010] S1. Preparation of bimetallic tube

[0011] The composite tube billet is constructed of a stainless steel outer layer (60% thickness) and a copper alloy inner layer (40%), metallurgically bonded through hot isostatic pressing. Spiral microgrooves with a depth of 50-80μm are laser-engraved on the inner wall of the tube billet to enhance lubricant adhesion and material flow guidance during hydroforming. Intelligent support rings are embedded, and biodegradable polylactic acid (PLA) support rings are pre-placed at both ends of the tube billet. These support rings are embedded with micro pressure sensors (<1mm diameter) for real-time monitoring of stress distribution during the forming process. The outer surface of the tube billet is plasma nitrided to form a 10-15μm hardened layer, enhancing resistance to hydraulic shock.

[0012] S2. Construction of dynamic adjustable mold system

[0013] The split inner core module is assembled, and two sections of hydraulically driven conical inner core modules are installed. The module gap is precisely adjusted by a servo motor (adjustment accuracy ±0.05mm), and supports continuous adjustment of eccentricity of 0.5-5mm. The inner wall of the mold is designed with asymmetric spiral guide grooves (groove depth 1.2mm on the thin-wall side and 0.8mm on the thick-wall side). The fluid path is optimized through CFD simulation, and the multi-parameter coupling control system integrates three-channel closed-loop control of hydraulic pressure (0-200MPa), temperature (-50℃~400℃), and inner core displacement. The fuzzy PID algorithm is used to achieve dynamic balance. The mold has a built-in distributed optical fiber sensor to collect wall thickness data in real time and feed it back to the control system.

[0014] S3, multi-stage collaborative hydroforming

[0015] Apply 80-100MPa reverse pressure axially to compress the tube blank to 95% of its initial length, eliminating the internal porosity and residual stress of the material. Simultaneously preheat the mold to 200°C to activate the viscoelastic properties of the PLA support ring. Inject high-pressure liquid (150MPa on the thin-wall side and 120MPa on the thick-wall side), and simultaneously drive the inner core module to offset at a speed of 0.5-2mm / s. According to the fiber optic sensor data, the pressure gradient and temperature field are dynamically adjusted every 0.1 second (the heating rate on the thin-wall side is 10°C / s and the thick-wall side is 5°C / s). Immediately after molding, the microchannel liquid nitrogen spray in the mold is started (-196°C), and the pipe is cooled to room temperature within 3 seconds to inhibit grain coarsening. The pressure holding and unloading curve is controlled by PLC to avoid rebound deformation (rebound amount <0.3%).

[0016] S4, post-processing and intelligent quality inspection

[0017] High-temperature nitrogen (400°C) is introduced to degrade the PLA support ring, and the residual gas is expelled through negative pressure suction, resulting in an inner wall roughness Ra ≤ 0.8μm. A CrAlN coating (2-3μm thick) is deposited by magnetron sputtering in the eccentric transition zone to improve corrosion resistance.

[0018] Geometric accuracy: A laser 3D scanner constructs a digital model and compares it with the design tolerance (eccentricity ±0.1mm, wall thickness deviation ±3%).

[0019] Performance test: Pulse water pressure test: 25-35MPa alternating pressure cycle 10^5 times, no leakage or plastic deformation; electrochemical workstation detection pitting potential, ensure >1.2V (vs.SCE).

[0020] Beneficial Effects: The core advantage of this hollow tube hydroformed eccentric water pipe joint lies in its combination of dynamic adjustment capabilities and high-reliability structural design, significantly improving installation efficiency and long-term stability. Its innovation lies in the integrated mechanism of mechanical linkage and visual feedback. The operator only needs to rotate a single joint circle to drive the slide to move laterally, causing the limit plate to slide within the sliding cavity, thereby precisely controlling the axial offset of the two eccentric tubes. The spirit level integrated in the sliding cavity can display the pipe angle changes in real time, achieving the simultaneous completion of eccentricity adjustment and horizontal calibration, avoiding the measurement errors and time loss of traditional step-by-step operations;

[0021] The double locking design further enhances the stability of the joint: the rotating ring is fixed by bolts to the matching relationship between the arc ring and the rotating groove, effectively preventing eccentric rebound; the upper locking ring forms a multi-layer sealing structure by squeezing the sealing surface through thread pressure, combined with the seamless hollow tube body manufactured by the hydraulic forming process, so that the overall pressure bearing capacity is increased by more than 40% compared with traditional welded pipes. After verification by 1.5 times the design pressure test, the joint can still maintain a leakage-free state under high-pressure environment, and the eccentric angle has no deformation or offset. In addition, the grease protection design of the sliding cavity and the sliding surface of the rotating ring, combined with the lightweight hollow tube structure, not only extends the service life, but also reduces the installation load in high-altitude or mobile scenes. It is suitable for high-demand fluid transportation scenes such as petrochemicals and municipal pipelines;

[0022] The process of the hollow tube hydraulically formed water pipe eccentric joint achieves seamless processing of complex eccentric structures through hydraulic forming technology, and combines dynamic adjustment and double locking design to form multiple advantages. Its beneficial effects are primarily reflected in three aspects: First, material utilization is significantly improved. The hydraulic forming process uses high-pressure fluid to evenly stretch the pipe, reducing material loss by over 60% and unit production costs by approximately 40%. Furthermore, the one-piece formed pipe has a uniform wall thickness distribution and is free of weld defects. Its compressive strength is 45% higher than that of traditional welded pipes, and its fatigue life is more than doubled, meeting the stringent sealing requirements of high-pressure fluids. Second, the integrated design of dynamic adjustment and horizontal calibration uses a circular motion to drive the slide plate to move laterally and link the limit plate to slide. Combined with real-time feedback from a spirit level on angle changes, this allows for simultaneous and precise adjustment of eccentricity and levelness, improving construction efficiency by over 30%. The linear guidance of the limit plate by the slide cavity avoids manual error. Third, the process is highly adaptable. Through flexible adjustment of mold and hydraulic parameters, joints with different eccentricities or curvature radii can be quickly produced. The mold modification cost is only 20% of that of traditional stamping processes. This makes it suitable for diverse scenarios such as underground pipe bending compensation and compact equipment layout, achieving both lightweight and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the overall structure of the water pipe head of the present invention;

[0025] Figure 3 It is a structural schematic diagram of the level adjustment device of the present invention.

[0026] In the figure: 1. Eccentric pipe of water pipe; 2. Water pipe head; 3. Threaded head; 4. Rotating groove; 5. Rotating circle; 6. Slide plate; 7. Limiting plate; 8. Sliding cavity; 9. Level; 10. Locking ring; 11. Arc ring; 12. Fixing block with hole. DETAILED DESCRIPTION

[0027] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example

[0029] like Figure 1-Figure 3 As shown, a hydraulically formed eccentric water pipe joint for a hollow pipe is provided, comprising an eccentric water pipe pipe 1, wherein the number of the eccentric water pipe pipe 1 is two, and both ends of the two eccentric water pipe pipes 1 are fixedly connected to a water pipe head 2, and the opposite ends of the water pipe head 2 are fixedly connected to a threaded head 3. A rotation groove 4 is provided on the outer wall of the lower threaded head 3, and a rotation ring 5 is rotatably connected to the outer wall of the rotation groove 4, and a slide plate 6 is fixedly connected to the outer walls of the two rotation rings 5, and the opposite ends of the slide plate 6 are fixedly connected to a limit plate 7, and the outer walls of the limit plate 7 are slidably connected to a sliding cavity 8, and the front surface of the sliding cavity 8 is fixedly connected to a spirit level 9. A locking ring 10 is threadedly connected to the outer wall of the upper threaded head 3. The rotation ring 5 comprises an arc ring 11, and the number of the arc rings 11 is two, and the outer walls of the two arc rings 11 are fixedly connected to a fixed block 12 with a hole, and the interiors of the two fixed blocks 12 with holes are threadedly connected by bolts 13;

[0030] Thread the two eccentric joints into the threaded connections at either end of the pipe to be connected, such as flanges or threaded pipe ends. Initially tighten until manually adjustable, ensuring that the eccentric tube 1 of the water pipe is aligned with the pipe axis. Observe the level gauge 9 on the slide cavity 8 and make preliminary adjustments to the overall joint angle to bring the pipe close to horizontal or to the designed inclination angle, laying the foundation for subsequent fine-tuning. While rotating the ring 5 of one joint, the ring 5 of the other joint remains stationary due to the restraining action of the slide plate 6 and the slide cavity 8, forming an "active-active" linkage. The active ring 5 drives the slide plate 6 laterally, pushing the limit plate 7 within the slide cavity 8, forcing the two eccentric tubes 1 to axially offset and achieve eccentricity adjustment. Using the level gauge 9 to provide real-time feedback on changes in pipe level, alternately rotate the two devices until the target eccentric angle and horizontality are achieved. After adjustment, tighten the bolts 13 of the two rings 5 ​​to secure the arc ring 11 within the groove 4 to prevent eccentricity rebound. Tighten the locking rings 10 on both joints simultaneously, using thread pressure to squeeze the sealing surface, such as a rubber washer or metal cone, to ensure the interface is sealed. After tightening, check the torque value of the bolts 13 and the locking ring 10. If necessary, use anti-loosening glue or double nuts to reinforce.

[0031] Finally, perform a water pressure test, pressurize the water to 1.5 times the design pressure, check whether the interface is leaking, confirm that the eccentric angle is not deformed due to pressure, clean the sliding surface of the sliding cavity 8 and the rotating circle 5, and apply grease such as silicone grease to prevent rust from affecting the subsequent adjustment flexibility.

[0032] According to another aspect of the present invention, a hollow pipe hydroforming eccentric water pipe joint is provided, comprising the following steps: S1, bimetallic tube blank preparation

[0033] The composite tube billet is constructed of a stainless steel outer layer (60% thickness) and a copper alloy inner layer (40%), metallurgically bonded through hot isostatic pressing. Spiral microgrooves with a depth of 50-80μm are laser-engraved on the inner wall of the tube billet to enhance lubricant adhesion and material flow guidance during hydroforming. Intelligent support rings are embedded, and biodegradable polylactic acid (PLA) support rings are pre-placed at both ends of the tube billet. These support rings are embedded with micro pressure sensors (<1mm diameter) for real-time monitoring of stress distribution during the forming process. The outer surface of the tube billet is plasma nitrided to form a 10-15μm hardened layer, enhancing resistance to hydraulic shock.

[0034] S2. Construction of dynamic adjustable mold system

[0035] The split inner core module is assembled, and two sections of hydraulically driven conical inner core modules are installed. The module gap is precisely adjusted by a servo motor (adjustment accuracy ±0.05mm), and supports continuous adjustment of eccentricity of 0.5-5mm. The inner wall of the mold is designed with asymmetric spiral guide grooves (groove depth 1.2mm on the thin-wall side and 0.8mm on the thick-wall side). The fluid path is optimized through CFD simulation, and the multi-parameter coupling control system integrates three-channel closed-loop control of hydraulic pressure (0-200MPa), temperature (-50℃~400℃), and inner core displacement. The fuzzy PID algorithm is used to achieve dynamic balance. The mold has a built-in distributed optical fiber sensor to collect wall thickness data in real time and feed it back to the control system.

[0036] S3, multi-stage collaborative hydroforming

[0037] Apply 80-100MPa reverse pressure axially to compress the tube blank to 95% of its initial length, eliminating the internal porosity and residual stress of the material. Simultaneously preheat the mold to 200°C to activate the viscoelastic properties of the PLA support ring. Inject high-pressure liquid (150MPa on the thin-wall side and 120MPa on the thick-wall side), and simultaneously drive the inner core module to offset at a speed of 0.5-2mm / s. According to the fiber optic sensor data, the pressure gradient and temperature field are dynamically adjusted every 0.1 second (the heating rate on the thin-wall side is 10°C / s and the thick-wall side is 5°C / s). Immediately after molding, the microchannel liquid nitrogen spray in the mold is started (-196°C), and the pipe is cooled to room temperature within 3 seconds to inhibit grain coarsening. The pressure holding and unloading curve is controlled by PLC to avoid rebound deformation (rebound amount <0.3%).

[0038] S4, post-processing and intelligent quality inspection

[0039] High-temperature nitrogen (400°C) is introduced to degrade the PLA support ring, and the residual gas is expelled through negative pressure suction, resulting in an inner wall roughness Ra ≤ 0.8μm. A CrAlN coating (2-3μm thick) is deposited by magnetron sputtering in the eccentric transition zone to improve corrosion resistance.

[0040] Geometric accuracy testing: A laser 3D scanner constructs a digital model and compares it with the design tolerance (eccentricity ±0.1mm, wall thickness deviation ±3%).

[0041] Performance test: Pulse water pressure test: 25-35MPa alternating pressure cycle 10^5 times, no leakage or plastic deformation, electrochemical workstation detection pitting potential to ensure >1.2V (vs.SCE).

[0042] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A hollow pipe hydraulically formed eccentric water pipe joint, comprising an eccentric water pipe (1), characterized in that: There are two eccentric water pipes (1), both ends of the two eccentric water pipes (1) are fixedly connected to water pipe heads (2), and the opposite ends of the water pipe heads (2) are fixedly connected to threaded heads (3).

2. The hydroformed eccentric water pipe joint of a hollow tube according to claim 1, characterized in that: The outer wall of the threaded head (3) below is provided with a rotation groove (4), the outer wall of the rotation groove (4) is rotatably connected to a rotation circle (5), the outer walls of the two rotation circles (5) are fixedly connected to a slide plate (6), the opposite ends of the slide plate (6) are fixedly connected to a limit plate (7), the outer walls of the limit plate (7) are slidably connected to a sliding cavity (8), and the front surface of the sliding cavity (8) is fixedly connected to a spirit level (9).

3. The hollow pipe hydroformed eccentric water pipe joint according to claim 2, characterized in that: The outer side wall of the upper threaded head (3) is threadedly connected with a locking ring (10).

4. The hollow pipe hydroformed eccentric water pipe joint according to claim 2, characterized in that: The rotating ring (5) includes an arc ring (11), the number of the arc rings (11) is two, the outer side walls of the two arc rings (11) are fixedly connected with a fixed block (12) with a hole, and the interiors of the two fixed blocks (12) with a hole are threadedly connected by bolts (13).

5. A hollow pipe hydraulically formed eccentric water pipe joint and a preparation method thereof, comprising any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Preparation of bimetallic tube A composite tube blank is constructed of a stainless steel outer layer (60% thickness) and a copper alloy inner layer (40%), metallurgically bonded via hot isostatic pressing. Spiral microgrooves with a depth of 50–80 μm are laser-engraved on the inner wall of the tube blank to enhance lubricant adhesion and material flow guidance during hydroforming. Intelligent support ring embedding: Biodegradable polylactic acid (PLA) support rings are pre-placed at both ends of the tube blank. Micro pressure sensors (<1mm diameter) are embedded in the support rings to monitor stress distribution during the molding process in real time. The outer surface of the tube blank is plasma nitrided to form a 10–15μm hardened layer, improving resistance to hydraulic shock. S2. Construction of dynamic adjustable mold system The split inner core module is assembled, and two sections of hydraulically driven conical inner core modules are installed. The module gap is precisely adjusted by a servo motor (adjustment accuracy ±0.05mm), and supports continuous adjustment of eccentricity of 0.5-5mm. The inner wall of the mold is designed with asymmetric spiral guide grooves (groove depth 1.2mm on the thin-wall side and 0.8mm on the thick-wall side). The fluid path is optimized through CFD simulation, and the multi-parameter coupling control system integrates three-channel closed-loop control of hydraulic pressure (0-200MPa), temperature (-50℃~400℃), and inner core displacement. The fuzzy PID algorithm is used to achieve dynamic balance. The mold has a built-in distributed optical fiber sensor to collect wall thickness data in real time and feed it back to the control system. S3, multi-stage collaborative hydroforming A reverse pressure of 80-100 MPa is applied axially to compress the tube to 95% of its initial length, eliminating internal porosity and residual stress. The mold is simultaneously preheated to 200°C to activate the viscoelastic properties of the PLA support ring. High-pressure liquid (150 MPa on the thin-wall side, 120 MPa on the thick-wall side) is injected, while the core module is simultaneously driven at a speed of 0.5-2 mm / s. Based on fiber optic sensor data, the pressure gradient and temperature field are dynamically adjusted every 0.1 second (heating rate 10°C / s on the thin-wall side, 5°C / s on the thick-wall side). Immediately after molding, liquid nitrogen spray (-196°C) is activated through the mold's microchannels, cooling the tube to room temperature within 3 seconds to suppress grain coarsening. A PLC controls the pressure-holding and unloading curves to prevent springback deformation (springback < 0.3%). S4, post-processing and intelligent quality inspection High-temperature nitrogen (400°C) is introduced to degrade the PLA support ring, and the residual gas is expelled through negative pressure suction, resulting in an inner wall roughness Ra ≤ 0.8μm. A CrAlN coating (2-3μm thick) is deposited by magnetron sputtering in the eccentric transition zone to improve corrosion resistance. Geometric accuracy testing: A laser 3D scanner constructs a digital model and compares it with the design tolerance (eccentricity ±0.1mm, wall thickness deviation ±3%). Performance test: Pulse water pressure test: 25-35MPa alternating pressure cycle 10^5 times, no leakage or plastic deformation; electrochemical workstation detection pitting potential to ensure >1.2V (vs.SCE).

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