A pipe end reducing device for a petroleum transport pipeline

Abstract

The application relates to a pipe end reducing device of a petroleum conveying pipeline pipe, which comprises a pipe body, a rack, a fixing unit for fixing the pipe body in the circumferential direction and a reducing unit for expanding or reducing the pipe end of the pipe body, the fixing unit and the reducing unit are symmetrically arranged on the two sides of the rack, the fixing unit fixes the pipe body on the rack and is coaxial with the reducing unit, and the reducing unit expands or reduces the pipe diameter of the pipe end of the pipe body by contacting the pipe end. The fixing unit and the reducing unit are symmetrically arranged on the two sides of the rack, so that the forces on the two sides are balanced, the pipe body is prevented from being deviated or bent due to unilateral force, the pipe body is fixed in the circumferential direction by the fixing unit, the circumferential force of the pipe body is uniformly balanced, axial displacement or radial deflection of the pipe body during the reducing process is prevented, and the coaxial degree and the roundness precision of the reducing are ensured.

Description

Technical Field

[0001] This invention relates to the field of pipe end diameter reduction technology for oil pipelines, and in particular to a pipe end diameter reduction device for oil pipelines. Background Technology

[0002] Conventional oil pipelines are usually connected by welding. Welding operations are time-consuming and require complicated preparation. In contrast, oil pipeline connection construction in foreign countries, such as the United States and Russia, often uses mechanical interference fitting to connect the pipelines. This method is fast, efficient, and requires less preparation time.

[0003] Therefore, in order to enable pipe connections, both ends of the pipe body need to be prefabricated in advance, with one end cold-expanded and the other end cold-shrinked. This way, when connecting pipes on site, the shrink-diameter end of one pipe can be inserted into the expanded-diameter end of another pipe, and the two pipes can be connected quickly and efficiently through mechanical interference fitting.

[0004] Utility model patent CN205147140U discloses a pipe end expansion and contraction device, belonging to the technical field of pipe fitting processing devices. It includes a left frame, a right frame, and a guide rod. An expansion cylinder is fixedly mounted on the front side of the left frame, and two contraction cylinders are fixedly mounted on the rear side of the left frame. The expansion cylinder is connected to an expansion punch, and the contraction cylinders are connected to a movable block. The upper and lower ends of the movable block cooperate with the guide rod. The movable block has a mold mounting hole, in which a contraction die is movably mounted. The contraction die includes an upper contraction die and a lower contraction die, which are respectively connected to a push cylinder. The centers of the expansion punch and the contraction die are on the same horizontal line. The outer diameter of the expansion punch gradually increases from right to left, and the inner diameter of the contraction die gradually decreases from right to left. However, this patent lacks a reliable method for fixing the pipe body during the expansion or contraction process.

[0005] Therefore, how to reliably fix the tube body during the tube expansion or contraction process is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and provide a pipe end reducing device for oil transportation pipelines.

[0007] The objective of this invention can be achieved through the following technical solutions: According to one aspect of the present invention, a pipe end reducing device for an oil pipeline is provided, comprising a pipe body, a frame, a fixing unit for circumferentially fixing the pipe body, and a reducing unit for expanding or reducing the diameter of the pipe end. The fixing unit and the reducing unit are symmetrically arranged on both sides of the frame. The fixing unit fixes the pipe body on the frame and is coaxial with the reducing unit. The reducing unit contacts the pipe end to expand or reduce the diameter of the pipe end.

[0008] As a preferred technical solution, the fixing unit includes a base clamping arm, a left clamping arm, a right clamping arm, and a clamping cylinder. The base clamping arm is disposed in the frame. The left and right clamping arms are movably connected to the two ends of the base clamping arm, respectively. The clamping cylinder is poweredly connected to the left and right clamping arms, respectively. The left and right clamping arms rotate in opposite directions.

[0009] As a preferred technical solution, the fixing unit further includes a clamping cylinder pin and a clamping cylinder pressure plate. One end of the clamping cylinder pin is disposed on the left or right clamping arm, and the other end of the clamping cylinder pin is connected to the cylinder body of the clamping cylinder. The clamping cylinder pin is fixed by the clamping cylinder pressure plate.

[0010] As a preferred technical solution, the fixing unit further includes a rotating shaft and a connecting sleeve. The rotating shaft is disposed in the left or right clamping arm, the connecting sleeve is disposed on the rotating shaft, and the output shaft of the clamping cylinder is connected to the connecting sleeve.

[0011] As a preferred technical solution, the fixing unit further includes a tube clamp, which is respectively disposed on the base clamp arm, the left clamp arm and the right clamp arm and contacts the tube body.

[0012] As a preferred technical solution, the fixing unit further includes threaded teeth, which are disposed on the inner surface of the tube clamp.

[0013] As a preferred technical solution, the fixing unit further includes a base pin, and the left clamping arm and the right clamping arm are movably connected to the two ends of the base clamping arm through the base pin.

[0014] As a preferred technical solution, the left clamping arm, the right clamping arm, and the base clamping arm all include arc portions. The arc portion of the base clamping arm is a semicircle, and the arc portions of the left and right clamping arms are quarter circles. The arc portions of the left clamping arm, the right clamping arm, and the base clamping arm form a complete circumference, and the circumference fits the tube body.

[0015] As a preferred technical solution, the diameter-changing unit includes a flange, a main oil cylinder, a connecting seat, and a diameter-changing component. The main oil cylinder is mounted on the frame, the connecting seat is mounted on the output shaft head of the main oil cylinder through the flange, the diameter-changing component is connected to the connecting seat, and the diameter-changing component is coaxial with the pipe body.

[0016] As a preferred technical solution, the reducing component includes a pipe punch for expanding the pipe end diameter and a pipe die for reducing the pipe diameter.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The fixing unit and the diameter changing unit of the present invention are symmetrically arranged on both sides of the frame, so that the force on both sides is balanced and the tube body is avoided from being deflected or bent due to the force applied on one side; the fixing unit fixes the tube body circumferentially, so that the circumference of the tube body is uniformly stressed, while ensuring that the tube body does not undergo axial displacement or radial deflection during the diameter changing process, thus ensuring the coaxiality and roundness accuracy of the diameter changing.

[0018] 2. This invention uses hydraulic drive to provide sufficient clamping force to ensure that large-diameter, heavy-duty pipes do not move axially when changing diameter; at the same time, the left and right clamping arms rotate in opposite directions to achieve synchronous opposing clamping, so that the clamping force is evenly distributed around the pipe and avoids local crushing.

[0019] 3. In this invention, the cylinder body of the clamping cylinder is connected to any one of the clamping arms, and the output shaft of the clamping cylinder is connected to another clamping arm. Only the extension or retraction of the output shaft is needed to achieve the opposite clamping or releasing of the clamping cylinder.

[0020] 4. The multi-segment clamps of the present invention are assembled to form a complete clamping surface, ensuring that the tube body is uniformly stressed along the entire circumference, preventing local stress concentration from causing the tube body to be pinched or flattened; the thread teeth significantly increase the axial friction coefficient between the tube body and the clamp, preventing the tube body from axially slipping when the diameter changes under large thrust, and at the same time requiring less clamping force than smooth clamps, reducing the risk of crushing of the outer wall of the tube body.

[0021] 5. The tube punch of the present invention presses inward into the tube end, causing the tube end material to plastically deform outward in the radial direction, thereby expanding the diameter; the tube die presses against the outer wall of the tube end, causing the tube end material to shrink inward in the radial direction, thereby reducing the diameter; the corresponding structure can be replaced according to actual needs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention from another perspective; Figure 3 This is a front view of the overall structure of the present invention; Figure 4 This is a top view of the overall structure of the present invention; Figure 5 This is a left view of the overall structure of the present invention; Figure 6 This is a right view of the overall structure of the present invention; Figure 7 This is a schematic diagram of the frame structure from a first-view perspective of the present invention; Figure 8 This is a schematic diagram of the frame structure from a second perspective of the present invention; Figure 9 This is a schematic diagram of the frame structure from a second perspective of the present invention; Figure 10 This is a schematic diagram of the structure of the base clamping arm of the present invention; Figure 11 This is a schematic diagram showing the front and back structures of the left clamping arm of the present invention; Figure 12 This is a schematic diagram of the structure of the right clamping arm of the present invention; Figure 13 This is a schematic diagram of the connector structure of the present invention; Figure 14 This is a schematic diagram of the flange structure of the present invention; Figure 15 This is a schematic diagram of the tube clamp structure of the present invention; Figure 16 This is a schematic diagram of the tube body concave mold structure of the present invention; Figure 17 This is a schematic diagram of the tube punch structure of the present invention; 1. Main hydraulic cylinder; 2. Frame; 3. Base pin; 4. Left clamping arm; 5. Clamping cylinder pin; 6. Clamping cylinder pressure plate; 7. Right clamping arm; 8. Clamping cylinder; 9. Pipe clamp; 10. Base clamping arm; 11. Pipe; 12. Pipe die; 13. Pipe punch; 14. Connecting seat; 15. Flange. Detailed Implementation

[0023] 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] Example 1 like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, a pipe end reducing device for an oil pipeline includes a pipe body 11, a frame 2, a fixing unit for circumferentially fixing the pipe body 11, and a reducing unit for expanding or reducing the diameter of the pipe end of the pipe body 11. The fixing unit and the reducing unit are symmetrically arranged on both sides of the frame 2. The fixing unit fixes the pipe body 11 on the frame 2 and is coaxial with the reducing unit. The reducing unit contacts the pipe end of the pipe body 11 to expand or reduce the diameter of the pipe end of the pipe body 11.

[0025] like Figure 3 , Figure 4 and Figure 6 As shown, the variable diameter unit includes a flange 15, a main oil cylinder 1, a connecting seat 14, and a variable diameter component. The main oil cylinder 1 is mounted on the frame 2. The connecting seat 14 is mounted on the output shaft head of the main oil cylinder 1 through the flange 15. The variable diameter component is connected to the connecting seat 14 and is coaxial with the pipe body 11.

[0026] like Figure 16 and Figure 17 As shown, the reducing component includes a pipe punch 13 for expanding the pipe end diameter of the pipe body 11 and a pipe die 12 for reducing the pipe diameter of the pipe body 11.

[0027] In this embodiment, a frame 2 is provided as a support. The two ends of the frame 2 are used to install a fixing unit and a reducing unit, respectively, so that the fixing unit and the reducing unit are symmetrically arranged. The fixing unit is used to fix the pipe body 11, fixing its circumference, so that the pipe body 11 is evenly stressed in the circumferential direction, avoiding stress concentration that could cause damage to the pipe body 11; at the same time, it prevents the pipe body 11 from moving axially during the expansion or reduction process. The reducing unit is used to expand or reduce the diameter of the pipe end of the pipe body 11.

[0028] like Figure 3 and Figure 4 As shown, the reducing unit includes a flange 15, a main hydraulic cylinder 1, a connecting seat 14, and a reducing component. The connecting seat 14 is mounted on the output shaft of the main hydraulic cylinder 1 via the flange 15. The reducing component is connected to the connecting seat 14, and the main hydraulic cylinder 1 is mounted on the frame 2. Power is provided by the main hydraulic cylinder 1, causing its output shaft to extend or retract, thereby moving the reducing component closer to or away from the pipe body 11 located on the fixed unit. The output shaft of the main hydraulic cylinder 1, the reducing component, and the pipe body 11 remain coaxial, facilitating the reducing component's action on the pipe end of the pipe body 11 to expand or reduce its diameter. The flange 15, connecting seat 14, and reducing component allow for flexible installation and removal of the reducing component, enabling flexible configuration to meet various needs.

[0029] The reducing component is divided into a pipe punch 13 for expanding the pipe end diameter of the pipe body 11 and a pipe die 12 for reducing the pipe diameter of the pipe body 11; the diameter of the pipe punch 13 changes sequentially along the axial direction (e.g., ...). Figure 17 As shown), the end of the tube punch 13 (i.e., the part that first enters the tube 11) has a diameter smaller than the diameter of the tube 11, facilitating entry into the tube 11. The diameter of the remaining part is larger than the diameter of the tube 11, thus expanding the diameter of the tube 11. The inner diameter of the tube die 12 varies sequentially along the axial direction (e.g., ...). Figure 16 As shown), the inner diameter of the end of the tube die 12 (i.e. the part that first enters the tube 11) is larger than the outer diameter of the tube 11, while the inner diameter of the remaining part is smaller than the outer diameter of the tube 11, thus reducing the diameter of the tube 11.

[0030] like Figure 6 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 As shown, the fixing unit includes a base clamping arm 10, a left clamping arm 4, a right clamping arm 7, and a clamping cylinder 8. The base clamping arm 10 is disposed in the frame 2. The left clamping arm 4 and the right clamping arm 7 are movably connected to both ends of the base clamping arm 10, respectively. The clamping cylinder 8 is poweredly connected to the left clamping arm 4 and the right clamping arm 7, respectively. The left clamping arm 4 and the right clamping arm 7 rotate in opposite directions.

[0031] In this embodiment, the base clamping arm 10 is mounted on the frame 2. A left clamping arm 4 and a right clamping arm 7 are respectively mounted at the top ends of the base clamping arm 10. Both the left and right clamping arms 4 and 7 are rotatable, forming a complete circumference with the base clamping arm 10 for circumferential fixation of the tube body 11. The power for the left and right clamping arms 4 and 7 is provided by the clamping cylinder 8, causing them to rotate in opposite directions to clamp or rotate in opposite directions to release.

[0032] The fixing unit also includes a clamping cylinder pin 5 and a clamping cylinder pressure plate 6. One end of the clamping cylinder pin 5 is set on the left clamping arm 4 or the right clamping arm 7, and the other end of the clamping cylinder pin 5 is connected to the cylinder body of the clamping cylinder 8. The clamping cylinder pin 5 is fixed by the clamping cylinder pressure plate 6.

[0033] The fixing unit also includes a rotating shaft and a connecting sleeve. The rotating shaft is disposed in the left clamping arm 4 or the right clamping arm 7, and the connecting sleeve is disposed on the rotating shaft. The output shaft of the clamping cylinder 8 is connected to the connecting sleeve.

[0034] The fixing unit also includes a base pin 3, and the left clamping arm 4 and the right clamping arm 7 are movably connected to both ends of the base clamping arm 10 through the base pin 3.

[0035] In this embodiment, the same power source is used to simultaneously achieve synchronous rotation of the left clamping arm 4 and the right clamping arm 7. The cylinder body of the clamping cylinder 8 is mounted on either the left clamping arm 4 or the right clamping arm 7 via the clamping cylinder pin 5. The output shaft of the clamping cylinder 8 is connected to either the left clamping arm 4 or the right clamping arm 7 via a rotating shaft and a connecting sleeve. The cylinder body is connected to only one clamping arm, while the output shaft is connected to the other clamping arm; that is, when the cylinder body is connected to the left clamping arm 4, the output shaft is connected to the right clamping arm 5. Corresponding through holes are provided on the left clamping arm 4 and the right clamping arm 7 to accommodate the rotating shaft and the clamping cylinder pin 5. The clamping cylinder pin 5 is fixed by the clamping cylinder pressure plate 6. Both the left clamping arm 4 and the right clamping arm 7 are rotatably connected to the base clamping arm 10 via the base pin 3.

[0036] like Figure 15 As shown, the fixing unit also includes a tube clamp 9, which is respectively disposed on the base clamp arm 10, the left clamp arm 4 and the right clamp arm 7 and contacts the tube body 11.

[0037] The fixing unit also includes threaded teeth, which are disposed on the inner surface of the tube clamp 9.

[0038] The left clamping arm 4, the right clamping arm 7, and the base clamping arm 10 all include arc-shaped portions. The arc-shaped portion of the base clamping arm 10 is a semicircle, and the arc-shaped portions of the left clamping arm 4 and the right clamping arm 7 are quarter circles. The arc-shaped portions of the left clamping arm 4, the right clamping arm 7, and the base clamping arm 10 form a complete circumference, and the circumference fits the tube body 11.

[0039] In this embodiment, the left clamping arm 4, the right clamping arm 7, and the base clamping arm 10 all include arc-shaped portions. The arc-shaped portions of the left clamping arm 4, the right clamping arm 7, and the base clamping arm 10 form a complete circle. The arc-shaped portions of the left clamping arm 4 and the right clamping arm 7 are quarter circles, and the arc-shaped portion of the base clamping arm 10 is a semi circle. The left clamping arm 4, the right clamping arm 7, and the base clamping arm 10 are adapted to the outer surface structure of the tube body 11 and can be perfectly clamped.

[0040] The pipe clamps 9 are configured as four pieces. Two pipe clamps 9 are on the base clamping arm 10, and one pipe clamp 9 is on each of the left and right clamping arms. After each pipe clamp 9 clamps the pipe 11, the gap between the end faces of any two clamps distributed radially along the pipe is 6.4 mm. Figure 6 As shown in the right view. The tube clamp 9 is 500mm long and has a threaded tooth profile of 60° triangular teeth on its inner surface. This design ensures that the tube 11 does not slip while the tube clamp 9 does not damage the tube 11 during the process of the tube being subjected to such a large thrust.

[0041] In addition, the frame 2 is welded from thick steel plates and square steel pipes, and a square frame is reserved at the rear of the frame 2 to accommodate the base clamping arm 10, such as... Figure 7 , Figure 8 , Figure 9 As shown, place the base clamping arm within the frame as required, perform full welding, and relieve stress after welding. Then, based on the position of the center hole of the base clamping arm 10, make the mounting hole for the main hydraulic cylinder 1 to ensure concentricity. The frame 2 is subjected to uniform stress throughout.

[0042] The connecting seat 14 is installed onto the piston rod head of the main oil cylinder 1. The mounting hole on the mold connecting seat 14 is a small taper conical hole, and the root round hole is used for positioning to ensure quick installation onto the piston rod head. Two half flanges 15 are installed onto the groove on the piston rod head of the main oil cylinder 1 and connected by bolts to firmly install the mold connecting seat 14 onto the piston rod head of the main oil cylinder 1.

[0043] The tube body die 12 and the tube body punch 13 are both made of M200 external thread and are installed on the die connecting seat 14 by thread connection. The die material is cold work die steel Cr12MoV.

[0044] Example 2 This invention enables the expansion and reduction of both ends of pipelines up to 12m in length and with an outer diameter of 10”~16”, thus meeting the requirements for large-diameter pipeline splicing operations. Taking a 16” pipeline (pipe body 11) as an example, a 16” pipeline with a pipe body specification of φ406.4×9.5 and material X52 is placed on a platform. The pipeline travels to the diameter reducing device station, and is transported to the diameter reducing device fixture by a liftable rotating conveyor roller (a standardized component, which can use existing devices), where it is expanded and reduced in diameter respectively.

[0045] The principle of the diameter expansion action: Start the hydraulic station of the diameter reducing device (standardized component, existing products can be used, not shown in the diagram), set the system pressure, operate the control button, and extend the piston rod of the clamping cylinder 8. At this time, the left clamping arm 4 and the right clamping arm 7 rotate and open around the base pin 3 respectively. When the end faces of the two clamping arms are in contact with the upper surface of the base clamping arm 10, the two clamping arms are fully open. Then raise the liftable rotating conveyor roller to lift the pipe 11 (16” pipeline pipe) located at the work station to a certain height. The conveyor roller rotates, sending the pipe 11 into the clamping arm fixtures of the diameter reducing device. One pipe clamp 9 is installed on the left clamping arm 4, one pipe clamp 9 is installed on the right clamping arm 7, and two pipe clamps 9 are installed on the base clamping arm 10. The tool is installed on the clamping arms by bolts on both sides. Then, the liftable rotary conveyor roller is lowered to place the tube body 11 on the two tube clamps 9 on the base clamping arm 10. Lubricating oil is applied to the inner wall of the end of the tube body 11 and the outer wall of the tube punch 13. Then, the piston rod of the clamping cylinder 8 is retracted to clamp the tube body 11. The piston rod of the main cylinder 1 is extended, and the tube punch 13 installed on the connecting seat 14 on the piston rod of the main cylinder 1 begins to extend into the tube body 11 to expand the diameter until the end face of the punch is in contact with the end face of the tube body. The expansion is completed. Then, the punch is withdrawn from the tube body 11, the left and right clamping arms are opened, and the liftable rotary conveyor roller lifts the tube body 11 and conveys the tube body 11 out of the fixed unit. Thus, one expansion operation is completed.

[0046] The principle of the diameter reduction operation: When reducing the diameter of the pipe body 11, the pipe punch 13 must first be replaced with the pipe die 12. Since the pipe punch 13 weighs nearly half a ton, it cannot be removed from the connecting seat 14 on the reducing device. Instead, the connecting seat 14 and the pipe punch 13 are first hoisted, and then the bolts connecting the connecting seat 14 and the flange 15 are removed. The connecting seat 14 and the pipe punch 13 can then be hoisted out of the reducing device as a whole. Then, the threads of the connecting seat 14 and the pipe punch 13 are unscrewed on the ground, and the punch is safely removed. The pipe die 12 is then screwed into the connecting seat 14 on the ground and hoisted onto the frame 2. The connecting seat 14 is then reinstalled onto the piston rod head of the main cylinder 1 through the flange 15. This completes the replacement of the pipe die 12. Repeat the expansion action to complete one tube diameter reduction. The difference from the expansion action is that lubricating oil needs to be applied to the outer surface of the tube 11 and the inner surface of the tube die 12.

[0047] During continuous production, a reducing device can be placed at each end of the pipe body 11 in a staggered manner. The pipe body punch 13 is installed on the first reducing device, and the pipe body die 12 is installed on the second reducing device. After the pipe body 11 is expanded on the first reducing device, it moves to the second reducing device to reduce the diameter at the other end. This ensures continuous prefabrication at both ends of the pipe body 11.

[0048] When the adjustable rotating conveyor roller is raised, the pipeline at the workstation is lifted to a certain height. The conveyor roller rotates and sends the pipe 11 into the clamping arm of the diameter reducing device. At this time, special attention should be paid to ensure that the pipe 11 is not lifted too low, otherwise the pipe 11 may collide with the clamp. This is because the two clamps on the base clamp arm are basically equivalent to a φ406.4 semicircle. Therefore, the pipe 11 needs to be raised to a relatively high height to avoid the two corners of these two clamps and smoothly enter the clamping arm of the diameter reducing device.

[0049] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A pipe end reducing device for an oil transmission pipeline, characterized in that, It includes a pipe body (11), a frame (2), a fixing unit for circumferentially fixing the pipe body (11), and a diameter-changing unit for expanding or shrinking the pipe end of the pipe body (11). The fixing unit and the diameter-changing unit are symmetrically arranged on both sides of the frame (2). The fixing unit fixes the pipe body (11) on the frame (2) and is coaxial with the diameter-changing unit. The diameter-changing unit contacts the pipe end of the pipe body (11) to expand or shrink the pipe diameter of the pipe end of the pipe body (11).

2. The pipe end reducing device for an oil pipeline according to claim 1, characterized in that, The fixing unit includes a base clamping arm (10), a left clamping arm (4), a right clamping arm (7), and a clamping cylinder (8). The base clamping arm (10) is set in the frame (2). The left clamping arm (4) and the right clamping arm (7) are movably connected to the two ends of the base clamping arm (10), respectively. The clamping cylinder (8) is poweredly connected to the left clamping arm (4) and the right clamping arm (7), respectively. The left clamping arm (4) and the right clamping arm (7) rotate in opposite directions.

3. The pipe end reducing device for an oil pipeline according to claim 2, characterized in that, The fixing unit also includes a clamping cylinder pin (5) and a clamping cylinder pressure plate (6). One end of the clamping cylinder pin (5) is set on the left clamping arm (4) or the right clamping arm (7), and the other end of the clamping cylinder pin (5) is connected to the cylinder body of the clamping cylinder (8). The clamping cylinder pin (5) is fixed by the clamping cylinder pressure plate (6).

4. The pipe end reducing device for an oil pipeline according to claim 2, characterized in that, The fixing unit also includes a rotating shaft and a connecting sleeve. The rotating shaft is disposed in the left clamping arm (4) or the right clamping arm (7), and the connecting sleeve is disposed on the rotating shaft. The output shaft of the clamping cylinder (8) is connected to the connecting sleeve.

5. The pipe end reducing device for an oil pipeline according to claim 2, characterized in that, The fixing unit also includes a tube clamp (9), which is respectively mounted on the base clamp arm (10), the left clamp arm (4) and the right clamp arm (7) and contacts the tube body (11).

6. The pipe end reducing device for an oil pipeline according to claim 5, characterized in that, The fixing unit also includes threaded teeth, which are disposed on the inner surface of the tube clamp (9).

7. The pipe end reducing device for an oil pipeline according to claim 2, characterized in that, The fixing unit also includes a base pin (3), and the left clamping arm (4) and the right clamping arm (7) are movably connected to both ends of the base clamping arm (10) through the base pin (3).

8. The pipe end reducing device for an oil pipeline according to claim 2, characterized in that, The left clamping arm (4), the right clamping arm (7) and the base clamping arm (10) all include arc portions. The arc portion of the base clamping arm (10) is a semicircle, and the arc portions of the left clamping arm (4) and the right clamping arm (7) are quarter circles. The arc portions of the left clamping arm (4), the right clamping arm (7) and the base clamping arm (10) form a complete circumference and the circumference fits the tube body (11).

9. The pipe end reducing device for an oil pipeline according to claim 1, characterized in that, The variable diameter unit includes a flange (15), a main cylinder (1), a connecting seat (14), and a variable diameter component. The main cylinder (1) is mounted on the frame (2). The connecting seat (14) is mounted on the output shaft head of the main cylinder (1) through the flange (15). The variable diameter component is connected to the connecting seat (14) and is coaxial with the pipe body (11).

10. The pipe end reducing device for an oil pipeline according to claim 9, characterized in that, The reducing component includes a pipe punch (13) for enlarging the pipe end diameter of the pipe body (11) and a pipe die (12) for reducing the pipe diameter of the pipe body (11).

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