Extra-high voltage flange pre-stress fastening device and installation method thereof

Abstract

The application discloses a kind of extra-high pressure flange prestress fastening device and its installation method, belong to fastening field, including a rod-shaped body with external thread, its core improvement is that the oil hole of same shaft is opened in the inside of rod-shaped body, and the both ends of oil hole are sealed by full welding sealing block and oil injection block, and oil injection block is provided with oil guide hole and sealing cone surface communicated therewith.Installation, install multiple fastening devices in flange, and connect to the same high-pressure oil loading device, inject high-pressure oil synchronously to make all fastening devices produce elastic elongation, then tighten all nuts synchronously in pressure maintaining state, and finally complete installation after pressure relief.The application realizes the synchronization, accurate hydraulic pre-tightening of fastening device through integrated built-in hydraulic oil way, makes installation more quick and convenient, and effectively guarantees the uniformity and long-term reliability of prestress of extra-high pressure flange connection.

Description

Technical Field

[0001] This invention belongs to the field of fastening devices, specifically a prestressed fastening device for ultra-high voltage flanges and its installation method. Background Technology

[0002] In the field of energy equipment such as oil and natural gas, key equipment such as wellheads and blowout preventers generally use ultra-high pressure flange connections, and their connecting parts are usually large double-ended studs or bolts of M36 or above. At present, the installation of such fastening devices mainly relies on tools such as hydraulic torque wrenches, that is, applying huge torque to generate prestress in the fastening device.

[0003] However, this method of applying torque has inherent defects: a considerable portion of the applied torque is used to overcome the friction between the threaded pairs and between the nut support surface and the flange. This portion of the torque is not effectively converted into axial prestress, but instead generates harmful residual torsional shear stress inside the fastening device. During long-term operation of the equipment, this residual stress will be gradually released due to factors such as vibration, impact and load fluctuation, leading to the attenuation of the prestress of the fastening device, which in turn causes the fastening device to loosen, posing a serious threat to the connection sealing and structural safety.

[0004] This problem also exists in other heavy-duty fields. In wind turbine generators, the tower flange connection fastening devices are subjected to complex alternating loads for a long time, and the prestress attenuation directly affects structural safety. In the field of ultra-high voltage mechanical equipment, such as large presses and mining crushers, the foundation connection fastening devices need to withstand huge working loads, and the maintenance of prestress is crucial. In bridge engineering, the connection quality of the fastening devices of steel structure nodes is directly related to the service life of the overall structure. The common feature of these application scenarios is that they all require the use of large, high-strength double-ended studs or bolts of M30 or above, and there are strict requirements for the precise control of prestress and long-term stability.

[0005] To address the problem of loosening of fasteners, existing technologies include mechanical methods such as double nuts for anti-loosening and cotter pin fixing. While these methods can limit nut rotation to some extent, they do not fundamentally eliminate residual stress that causes prestress attenuation. These anti-loosening measures have limited effectiveness under long-term vibration conditions and increase the complexity of the structure and maintenance costs.

[0006] To more accurately control prestress and reduce the impact of friction, the industry has also adopted advanced methods such as hydraulic stretching, heating elongation, and yield control. Although these methods can effectively improve the accuracy of prestress, they generally face problems such as expensive equipment, complex processes, or low operating efficiency, which restricts their large-scale promotion and application in industrial sites, especially in situations where space is limited or high-efficiency operations are required.

[0007] Especially in large flange connections, dozens or even hundreds of double-ended studs or bolts need to be installed. Traditional hydraulic tensioners are often bulky and require tensioning one by one, resulting in low work efficiency and difficulty in ensuring the uniformity of prestress of all fastening devices. While the torque method is relatively simple to operate, the prestress dispersion is large and cannot meet the quality requirements of high-standard connections.

[0008] Therefore, the industry urgently needs a new type of fastening device and its installation technology that can achieve precise prestress control, avoid the generation of residual torsional stress, and has the characteristics of compact structure and simple operation. It can adapt to the installation requirements under various complex working conditions, while ensuring the stability and reliability of prestress during long-term use. Summary of the Invention

[0009] The purpose of this invention is to address the aforementioned technical problems by providing a high-pressure flange connection for use in the oil and natural gas industries. This connection eliminates the need for applying enormous torque, thereby achieving synchronous and precise hydraulic pre-tightening of the fastening device. This makes installation faster and more convenient, effectively ensuring precise control of prestress and reliability of the fastening device connection under heavy-load conditions.

[0010] The objective of this invention is achieved through the following technical solution: A prestressed fastening device for ultra-high pressure flanges, comprising a rod-shaped body with external threads, characterized in that: an oil hole is axially formed inside the rod-shaped body; the oil hole is cylindrical, with a diameter of 50% to 80% of the nominal diameter of the fastening device, and is coaxially arranged with the rod-shaped body to ensure that the pressure generated by the injected hydraulic oil does not produce a bending moment on the rod-shaped body; a sealing block is fully welded to the upper end of the oil hole; the sealing block is a solid cylinder, and its upper and lower end faces are perpendicular to the axis of the rod-shaped body, ensuring that the pressure direction generated by the hydraulic oil is aligned with the axial direction of the rod-shaped body. The lower end of the oil hole is fully welded with an oil injection block. The upper and lower end faces of the oil injection block are perpendicular to the axis of the rod-shaped body, ensuring that the pressure direction generated by the hydraulic oil is consistent with the axial direction of the rod-shaped body. The oil injection block is provided with an axial guide hole with a diameter of 2-3 mm. The inner end of the guide hole communicates with the oil hole, and its outer end is provided with a sealing cone surface. The sealing cone surface can fit with the cone surface of the oil injection nozzle. The large diameter end of the sealing cone surface faces the outside of the rod-shaped body, and the small diameter end faces the inside of the rod-shaped body. The axial height of the sealing block and the oil injection hole is less than one-tenth of the length of the rod-shaped body, and their outward end faces are flush with the end face of the rod-shaped body.

[0011] An installation method for a flange fastening device for ultra-high voltage power transmission, characterized by the following steps: S1: Batch installation and initial tightening: Pass multiple UHV flange fastening devices one by one through the corresponding fastening holes on the first connecting plate and the second connecting plate, and screw the first nut and the second nut onto both ends of each fastening device respectively. Tighten the first nut and the second nut of all fastening devices by hand until each rod-shaped body cannot be loosened in the axial direction. S2: Batch connection of oil injection devices: Screw the female thread into the second connecting thread of each fastening device one by one, and tighten it with a wrench to a torque of at least 50 Nm, so that the conical surface of each oil injection nozzle forms a sealing connection with the sealing conical surface of the corresponding oil injection block, generating contact stress to prevent inadequate sealing when injecting high-pressure hydraulic oil, and connect the oil injection pipes on all oil injection nozzles to a common high-pressure oil loading device. S3: Internal venting operation: Activate the high-pressure oil loading device and inject hydraulic oil at a pressure of less than 10MPa into the oil holes of all fasteners. Then perform the depressurization operation. Repeat this "oil injection-depressurization" cycle at least twice to ensure that the air in the oil holes is fully vented. S4: Simultaneous application of hydraulic prestress: Start the high-pressure oil loading device and simultaneously inject high-pressure hydraulic oil of more than 200MPa into the oil holes of all fastening devices. However, the stress generated should be less than 70% of the yield strength of the fastening device material. Under the action of oil pressure, all rod-shaped bodies will simultaneously produce axial elastic tensile deformation, resulting in gaps between the first nut and the first connecting plate of each fastening device, and between the second nut and the second connecting plate. S5: Final tightening: While maintaining hydraulic pressure, use a wrench to tighten the first and second nuts on all fasteners in sequence until all gaps created in step S4 are completely eliminated. S6: Synchronous pressure relief and disassembly: Close the high-pressure oil loading device and release the system oil pressure. Then, remove the female thread and oil injection nozzle from all fastening devices and recover the hydraulic oil to avoid environmental pollution. This completes the pre-tightening installation of all fastening devices on the entire flange.

[0012] Compared with the prior art, the present invention has the following advantages: This invention uses hydraulic direct tensioning to fasten the device without applying a huge torque. Its prestress has a strict linear relationship with the oil pressure, thereby achieving precise and quantitative control of the prestress of the fastening device. This can make full use of the bolt strength and avoid yielding or fatigue failure.

[0013] The installation method of this invention is simple and quick to operate. It eliminates the need for complex external piping and bulky tensioners required by the traditional hydraulic tensioning method. All operations can be completed with just a lightweight grease fitting, which simultaneously pre-tightens all fastening devices.

[0014] This invention integrates hydraulic oil channels inside the fastening device. Because the cross-sectional area is reduced due to the oil holes inside its rod-shaped body, in order to meet the same load-bearing capacity, the nominal diameter of the fastening device only needs to be increased accordingly to use this fastening device without changing the flange body structure or connection form. Therefore, it has good versatility and engineering applicability. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of the ultra-high voltage flange fastening device of the present invention; Figure 2 for Figure 1 Enlarged view of the oil injection block; Figure 3 This is a schematic diagram of the installation of an ultra-high voltage flange. Figure 4 for Figure 3 Enlarged view of a single fastening device installation; Figure 5 for Figure 3 Enlarged view of the contact between the middle cone surfaces; Figure 6 for Figure 3 A bottom view; Figure 7 This is a schematic diagram illustrating the application of the present invention on a bolt.

[0016] In the figure: 1. Rod-shaped body; 101. First connecting thread; 102. Second connecting thread; 2. Oil hole; 3. Sealing block; 4. Oil injection block; 401. Oil guide hole; 402. Sealing cone surface; 5. First nut; 6. First connecting plate; 7. Second connecting plate; 8. Second nut; 9. Wrench; 10. Female thread; 11. Oil injection nozzle; 12. Oil injection pipe; 13. High-pressure oil loading device. Detailed Implementation

[0017] 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. Based on the embodiments of the invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figures 1 to 6As shown, the ultra-high pressure flange fastening device of the present invention includes a rod-shaped body 1, which is an M48×400-8.8 grade double-ended stud, replacing the original M36 double-ended stud. An oil hole 2 is axially formed inside the rod-shaped body 1. The oil hole 2 is a cylindrical hole with a diameter of 30mm and is coaxially arranged with the rod-shaped body 1 to ensure that the pressure generated by the injected hydraulic oil will not generate a bending moment on the rod-shaped body 1. A sealing block 3 is fully welded to the upper end of the oil hole 2. The sealing block 3 is a solid cylinder with a height of 15mm, and its upper and lower end faces are perpendicular to the axis of the rod-shaped body 1 to ensure that the pressure direction generated by the hydraulic oil is consistent with the axial direction of the rod-shaped body 1. The lower end of the oil hole 2 is fully welded to the lower end of the rod-shaped body 1. An oil injection block 4 is welded on, with a height of 15mm. The upper and lower end faces of the oil injection block 4 are perpendicular to the axis of the rod-shaped body 1, ensuring that the pressure direction generated by the hydraulic oil is consistent with the axial direction of the rod-shaped body 1. The oil injection block 4 is provided with an axial oil guide hole 401 with a diameter of 3mm. The inner end of the oil guide hole 401 is connected to the oil hole 2, and its outer end is provided with a sealing cone surface 402. The sealing cone surface 402 can fit with the cone surface of the oil injection nozzle 11. The large diameter end of the sealing cone surface 402 faces the outside of the rod-shaped body 1, and the small diameter end faces the inside of the rod-shaped body 1. The large diameter of the sealing cone surface is 5mm, and the small diameter is 3mm. The outward end faces of the sealing block 3 and the oil injection block 4 are flush with the end face of the rod-shaped body 1.

[0019] A method for installing double-ended studs on ultra-high voltage flanges, such as Figures 3 to 6 As shown, it includes the following steps: S1: Batch installation and initial tightening: Pass the multiple UHV flange double-ended studs one by one through the corresponding fastening holes on the first connecting plate 6 and the second connecting plate 7, and screw the first nut 5 and the second nut 8 onto both ends of each double-ended stud respectively. Tighten the first nut 5 and the second nut 8 of all double-ended studs by hand until each rod-shaped body 1 cannot be loosened in the axial direction. S2: Batch connection of the oil injection device: Screw the female thread 10 one by one onto the second connecting thread 102 of each double-ended stud, and tighten with a wrench 9 to a torque of 50 Nm. Figure 5 As shown, the conical surface of each oil injection nozzle 11 forms a sealing connection with the corresponding sealing conical surface 402 of the oil injection block 4, generating a certain contact stress to prevent incomplete sealing when injecting high-pressure hydraulic oil. Figure 6 The oil injection pipes 12 on all the oil injection nozzles 11 are connected to a common high-pressure oil loading device 13. S3: Internal venting operation: Start the high-pressure oil loading device 13 and inject 10MPa of hydraulic oil into the oil holes 2 of all double-ended studs. Then perform the depressurization operation and repeat this "oil injection-depressurization" cycle twice to ensure that the air in the oil holes is fully vented. S4: Apply hydraulic prestress synchronously: Start the high-pressure oil loading device 13 and inject 350MPa hydraulic oil into the oil holes 2 of all double-ended studs synchronously. Under the action of oil pressure, all rod-shaped bodies 1 synchronously generate axial elastic tensile deformation, causing gaps to appear between the first nut 5 and the first connecting plate 6 of each double-ended stud, and between the second nut 8 and the second connecting plate 7. S5: Final tightening: While maintaining hydraulic pressure, use wrench 9 to tighten the first nut 5 and the second nut 8 on all double-ended studs in sequence until the gaps created in step S4 on all double-ended studs are completely eliminated; S6: Synchronous pressure relief and disassembly: Close the high-pressure oil loading device 13 and release the system oil pressure. Then, remove the female thread 10 and oil injection nozzle 11 from all double-ended studs and recover the hydraulic oil to avoid environmental pollution. This completes the pre-tightening installation of all double-ended studs on the entire flange.

[0020] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Figures 1-6 The term "double-ended stud" does not imply that the invention is only applicable to double-ended studs, but rather to bolts (see reference). Figure 7 Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A prestressed fastening device for ultra-high voltage flanges, comprising a rod-shaped body (1) with external threads, characterized in that: An oil hole (2) is axially formed inside the rod-shaped body (1). The oil hole (2) is a cylindrical hole and is coaxially arranged with the rod-shaped body (1). A sealing block (3) is fully welded to the upper end of the oil hole (2). The sealing block (3) is a solid cylinder, and its upper and lower end faces are perpendicular to the axis of the rod-shaped body (1). An oil injection block (4) is fully welded to the lower end of the oil hole (2). The upper and lower end faces of the oil injection block (4) are perpendicular to the axis of the rod-shaped body (1). The oil injection block (4) is provided with an axial oil guide hole (401). The inner end of the oil guide hole (401) is connected to the oil hole (2), and its outer end is provided with a sealing cone surface (402). The large diameter end of the sealing cone surface (402) faces the outside of the rod-shaped body (1), and the small diameter end faces the inside of the rod-shaped body (1).

2. A method for installing the prestressed fastening device for ultra-high voltage flanges as described in claim 1, characterized in that, Includes the following steps: S1: Batch installation and initial tightening: Pass multiple UHV flange prestressed fastening devices one by one through the corresponding fastening holes on the first connecting plate (6) and the second connecting plate (7), and screw the first nut (5) and the second nut (8) onto both ends of each fastening device respectively. Tighten the first nut (5) and the second nut (8) of all fastening devices by hand until each rod-shaped body (1) cannot be loosened in the axial direction. S2: Batch connection of oil injection devices: Screw the female thread (10) into the second connection thread (102) of each fastening device one by one, and tighten it with a wrench (9) so that the conical surface of each oil injection nozzle (11) forms a sealed connection with the sealing conical surface (402) of the corresponding oil injection block (4), and connect the oil injection pipe (12) on all oil injection nozzles (11) to a common high-pressure oil loading device (13). S3: Internal venting operation: Start the high-pressure oil loading device (13), inject low-pressure hydraulic oil into the oil holes (2) of all fasteners, and then perform the depressurization operation. Repeat this "oil injection-depressurization" cycle at least twice. S4: Apply hydraulic prestress synchronously: Start the high pressure oil loading device (13) and inject high pressure hydraulic oil into the oil holes (2) of all fastening devices synchronously. Under the action of oil pressure, all rod-shaped bodies (1) synchronously generate axial elastic tensile deformation, causing gaps to appear between the first nut (5) and the first connecting plate (6) of each fastening device, and between the second nut (8) and the second connecting plate (7). S5: Final tightening: While maintaining oil pressure, use a wrench (9) to tighten the first nut (5) and the second nut (8) on all fasteners in sequence until the gaps created in step S4 on all fasteners are completely eliminated; S6: Synchronous pressure relief and disassembly: Close the high-pressure oil loading device (13) and release the system oil pressure, then remove the female thread (10) and oil injection nozzle (11) from all fastening devices to complete the pre-tightening installation of all fastening devices of the entire flange.

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