Automatic root cleaning machine for small-bore pipeline inner girth weld and working method thereof

Abstract

The application discloses a small-bore pipeline inner ring weld automatic root cleaning machine and a working method thereof, and belongs to the field of pipeline inner weld cleaning. The machine comprises walking driving joints, universal joints, in-place tensioning joints and polishing joints which are coaxially arranged in sequence from back to front. The polishing joint comprises an integral rotating driving assembly connected with the in-place tensioning joint. The output end of the integral rotating driving assembly is connected with a polishing driving assembly through a first support frame. The output end of the polishing driving assembly is connected with a grinding wheel. A camera is arranged on the first support frame and close to the grinding wheel. The camera and the grinding wheel are located on the same radial plane. The small-bore pipeline inner ring weld automatic root cleaning machine and the working method thereof can quickly complete the automatic and accurate root cleaning work of the small-bore pipeline weld through the modular design of various functional joints and the cooperation of the camera.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline internal weld cleaning, in particular to a small-diameter pipeline internal girth weld automatic root cleaning machine and a working method thereof. BACKGROUND

[0002] In the small-diameter pipeline installation and maintenance engineering of the petroleum, chemical, natural gas and other industries, the root cleaning operation of the pipeline internal girth weld is a key process to ensure the strength and sealing performance of the welded joint. That is, after the single-side welding of the pipeline is completed, the root of the weld needs to be thoroughly cleaned to remove defects such as welding slag and un-melted areas, otherwise it will directly affect the pressure resistance and service life of the pipeline, and cannot meet the stringent requirements of the industry on the safe operation of the pipeline.

[0003] In the prior art, the mainstream for the root cleaning operation of the small-diameter pipeline internal girth weld is the manual handheld abrasive wheel piece type root cleaning machine. The operation mode of this type of equipment is that the operator needs to stretch his hands and the equipment into the narrow internal space of the pipeline, manually holds the root cleaning machine with an abrasive wheel piece according to his subjective experience, continuously adjusts the radial distance and polishing depth of the abrasive wheel piece and the internal wall of the pipeline along the girth weld track, and polishes the root of the weld through the high-speed rotation of the abrasive wheel piece.

[0004] However, the above-mentioned manual handheld abrasive wheel piece type root cleaning machine has significant technical defects in actual application, and cannot meet the quality and efficiency requirements of the small-diameter pipeline root cleaning operation, which are as follows:

[0005] 1. High labor intensity and health risks: Due to the limited internal operating space of the small-diameter pipeline, the operator needs to maintain a fixed posture such as bending over and stretching his arms for a long time, continuously holds the equipment and adjusts its position and posture, which easily causes physical fatigue and leads to a decrease in operation stability. At the same time, the continuous vibration generated during the operation of the equipment will be transmitted to the operator's hands through the handle, and long-term operation can easily induce hand vibration disease and other occupational health problems, and the instability of manual holding further increases the risk of the equipment knocking against the internal wall of the pipeline.

[0006] 2. Low processing precision and poor quality consistency: The core parameters of the root cleaning operation (such as polishing depth, centering of the abrasive wheel piece and the weld, and uniformity of the circular track) completely depend on the experience judgment of the operator, and there is no objective detection and control means. On the one hand, the difference in technical level of different operators will lead to uneven root cleaning quality of the same batch of pipelines; on the other hand, even the same operator will cause the problems of "over-polishing" (damaging the base metal of the pipeline) or "incomplete root cleaning" (leaving welding slag) due to the operation deviation caused by fatigue after a long time of operation, which seriously affects the strength and sealing performance of the weld joint, and cannot meet the high standard requirements of the petroleum, chemical and other industries on the welding quality of the pipeline.

[0007] 3. Low work efficiency and impact on project progress: the speed of manual operation is limited by the physiological limit of human body, and the inner ring welding seam of a single small-diameter pipeline needs to be polished segment by segment, and the single operation time is relatively long; when facing the batch pipeline cleaning task, the efficiency bottleneck of manual operation will cause the overall project progress to lag seriously, especially in the project with strict requirements on construction period such as oil pipeline construction, and the defect is more prominent.

[0008] In summary, the existing manual handheld abrasive wheel piece type cleaning machine cannot adapt to the technical requirements of "high precision, high efficiency and low labor intensity" for the inner ring welding seam cleaning operation of small-diameter pipeline. SUMMARY

[0009] The purpose of the present application is to provide a small-diameter pipeline inner ring welding seam automatic cleaning machine and its working method, which solves the above technical problems.

[0010] To achieve the above purpose, the present application provides a small-diameter pipeline inner ring welding seam automatic cleaning machine, which comprises walking driving joints, universal joints, in-place tensioning joints and polishing joints arranged coaxially in sequence from back to front, wherein the polishing joint comprises a whole rotating driving assembly connected with the in-place tensioning joint, the output end of the whole rotating driving assembly is connected with a polishing driving assembly through a first support frame, the output end of the polishing driving assembly is connected with an abrasive wheel, a camera is further arranged on the first support frame and close to the abrasive wheel, and the camera and the abrasive wheel are located on the same radial plane;

[0011] The camera is electrically connected with the driving joint, the whole rotating driving assembly and the polishing driving assembly through a control terminal, is used for collecting the image of the inner wall of the small-diameter pipeline to be cleaned by the camera, and drives the abrasive wheel to automatically clean after the driving joint, the whole rotating driving assembly and the polishing driving assembly are controlled by the control terminal after processing.

[0012] Preferably, the whole rotating driving assembly comprises a whole rotating driving motor fixed on the in-place tensioning joint, a planetary gear connected with the output end of the whole rotating driving motor, the gear ring of the planetary gear is fixedly connected with one end of the first support frame, the other end of the first support frame is eccentrically connected with a driving shaft, one end of the driving shaft is connected with the output end of the polishing driving assembly, the other end is fixedly connected with the abrasive wheel, the polishing part of the abrasive wheel protrudes from the outer edge of the first support frame, and the polishing part of the abrasive wheel and the mounting position of the camera are staggered arranged;

[0013] The abrasive wheel and the polishing driving assembly are arranged on both sides of the first support frame, and the polishing driving assembly is arranged inside the first support frame.

[0014] Preferably, the polishing driving assembly comprises an electric push rod fixed inside the first support frame and a self-rotating polishing driving motor connected with the output end of the electric push rod, and the output end of the self-rotating polishing driving motor is fixedly connected with the driving shaft.

[0015] The first support frame is provided with a long strip-shaped guide hole, which is parallel to the electric push rod and is penetrated by the driving shaft.

[0016] Preferably, the walking driving section comprises a driving wheel side support and a plurality of walking driving assemblies rotatably arranged on the outer circumferential side of the driving wheel side support, and each of the plurality of walking driving assemblies is a tire structure provided with a hub motor.

[0017] Preferably, the in-place tensioning section comprises a second support frame and an in-place tensioning driving assembly arranged in the second support frame, the in-place tensioning driving assembly comprises an in-place tensioning driving motor fixed on the second support frame and a driving gear disc connected with the output end of the in-place tensioning driving motor, the end surface of the driving gear disc is uniformly provided with a plurality of arc-shaped guide holes with the same direction, one end of the arc-shaped guide hole is movably connected with a tensioning rod, the other end of the tensioning rod is fixedly connected with a tensioning shoe after penetrating through a guide plate fixed on the second support frame, a pressure sensor is fixed on the side of the tensioning shoe facing the inner wall of the small-diameter pipeline to be cleaned, and the pressure sensor is in communication with a control terminal.

[0018] A universal joint is arranged between the driving wheel side support and the second support frame.

[0019] Preferably, a plurality of bull's eye bearings are rotatably arranged on the outer circumferential side of the first support frame and face the inner wall of the small-diameter pipeline to be cleaned.

[0020] Preferably, the lengths of the walking driving section, the in-place tensioning section and the polishing section are , and the maximum diameter is ;

[0021] wherein the length satisfies the following constraint relationship with the small-diameter pipeline to be cleaned:

[0022] ;

[0023] wherein, represents the curvature radius of the elbow portion of the small-diameter pipeline to be cleaned; represents the radius of the straight pipe portion of the small-diameter pipeline to be cleaned; represents the bending angle of the elbow portion of the small-diameter pipeline to be cleaned, and when , is 0.707;

[0024] satisfies the following constraint relationship with the small-diameter pipeline to be cleaned:

[0025] ;

[0026] wherein, represents the minimum safety gap between the set automatic root cleaning machine and the inner wall of the small-diameter pipeline to be cleaned;

[0027] At the same time, the diameter of the in-place tension joint in the contracted state and the maximum diameter also satisfy the following constraint relationship:

[0028] .

[0029] A working method of a small-diameter pipeline inner ring weld automatic root cleaning machine, comprising the following steps:

[0030] S1, the automatic root cleaning machine is sent into the inner wall of the small-diameter pipeline to be cleaned, and the walking driving joint is opened when the in-place tension joint is in the contracted state, the tire drives the in-place tension joint and the polishing joint to move axially along the inner wall of the small-diameter pipeline to be cleaned under the driving action of the in-wheel motor, and the camera is used to collect the image of the inner wall of the small-diameter pipeline to be cleaned in the process, the weld position is determined according to the image of the inner wall of the small-diameter pipeline, the walking driving joint is closed, and the control terminal is used to determine the weld width and the target polishing depth ;

[0031] S2, the in-place tension joint is opened, the driving gear plate is driven to rotate by the in-place tension driving motor, and then the tension rod moves radially in the arc-shaped guide hole, at this time, the tension rod is pushed out under the guidance of the arc-shaped guide hole, and then the plurality of tension boots are synchronously extended until the tension force collected by the pressure sensor reaches the set tension force, and the tension driving motor is closed;

[0032] S3, adjusting the initial position: based on the target polishing depth, the electric push rod is driven to drive the grinding wheel to move along the long strip-shaped guide hole until it is flush with the inner ring weld, and then the electric push rod is closed;

[0033] S4, start the self-rotation polishing driving motor, the overall rotation driving motor and the electric push rod, the self-rotation polishing driving motor drives the grinding wheel to rotate around the center of the rotation shaft, at the same time, the overall rotation driving motor drives the polishing joint to rotate as a whole, and the electric push rod drives the grinding wheel to give radial feed so that the grinding wheel polishes at the set rotation speed and radial feed speed until it is ground flat;

[0034] S5, control the tension boots of the in-place tension joint to shrink, and then open the in-wheel motor to drive the automatic root cleaning machine to push out the small-diameter pipeline to be cleaned.

[0035] Preferably, in step S1, the camera is used to collect the image of the inner wall of the small-diameter pipeline to be cleaned, and after being converted into a gray-scale image, the gray-scale difference value of the gray-scale values of the two adjacent pixels in the axial direction is calculated , and then the gray-scale difference value is compared with the set gray-scale threshold value , if if the value of the welding seam position is reached, it is determined that the welding seam position is reached, otherwise, it is determined that the welding seam position is not reached;

[0036] wherein,

[0037]

[0038] wherein, and respectively represent the gray scale values of two pixels axially adjacent to each other.

[0039] Preferably, in step S4, the rotating speed is set to satisfy the following relationship between the rotating speed and the radial feed speed:

[0040]

[0041] wherein, represents a calibration coefficient.

[0042] Therefore, the present application adopts the above-mentioned small-diameter pipe inner girth welding seam automatic root cleaning machine and its working method, which has the beneficial effects of:

[0043] 1. Significantly reduce labor intensity and avoid occupational health risks: Compared with the traditional manual handheld abrasive wheel piece type root cleaning machine, the present application can fundamentally eliminate the physical fatigue of the operator due to long-time operation through the "power-driven joint automatic movement + in-place tensioning joint fixation + polishing joint" snake-shaped modular design; and avoid the transmission of equipment vibration through the hands, effectively avoiding occupational health hazards such as hand vibration disease, and improving the safety of the working environment; at the same time, the size of each joint strictly follows the pipeline adaptation constraint, and the flexible connection between joints is realized through the universal joint, which can smoothly pass through the internal space of the small-diameter elbow pipe, solving the technical pain point of the traditional equipment "straight pipe can be operated, elbow pipe is difficult to adapt", and expanding the applicability of the equipment to complex pipeline scenes.

[0044] 2. Greatly improve the root cleaning precision and ensure the consistency of the welding seam quality: the core parameters such as the welding seam position and height can be automatically determined based on the image collected by the camera, and then based on the recognition result, the feed and rotation of the abrasive wheel can be controlled, which can effectively avoid the problems of "excessive wear of the base material" or "incomplete root cleaning of residual welding slag", ensure the high consistency of the root cleaning quality of different pipelines and different operation periods, and meet the strict standards of welding joint strength and sealing performance.

[0045] 3. High efficiency and short operation cycle: the power-driven joint is used to realize fast pipe entry and exit, and the continuous polishing of the annular welding seam is realized at a preset rotating speed and radial feed speed, without the need for manual operation, which can greatly shorten the root cleaning time of a single pipeline, especially suitable for batch pipeline installation and maintenance scenes in the petroleum and chemical industries, effectively avoiding the delay of the overall project progress due to the root cleaning process. ​​​​

[0046] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 Figure 1 is a schematic diagram of the overall structure of the automatic root cleaning machine for the inner girth weld of small-bore pipelines according to the present application.

[0048] Figure 2 Figure 2 is a schematic diagram of the polishing joint structure of the automatic root cleaning machine for the inner girth weld of small-bore pipelines according to the present application.

[0049] Figure 3 Figure 3 is a schematic diagram of the in-place tensioning joint structure of the automatic root cleaning machine for the inner girth weld of small-bore pipelines according to the present application.

[0050] Figure 4 Figure 4 is a schematic diagram of the walking drive joint structure of the automatic root cleaning machine for the inner girth weld of small-bore pipelines according to the present application.

[0051] Figure 5 Figure 5 is a layout diagram of the long strip-shaped guide hole of the automatic root cleaning machine for the inner girth weld of small-bore pipelines according to the present application.

[0052] LIST OF REFERENCE NUMERALS

[0053] 1, camera; 2, grinding wheel; 3, self-rotation polishing drive motor; 4, electric push rod; 5, first support frame; 6, overall rotation drive motor; 7, second support frame; 8, universal joint; 9, tire; 10, driving wheel side support; 11, drive gear disc; 12, tensioning boot; 13, in-place tensioning drive motor; 14, bull-eye bearing; 15, planetary gear; 16, tensioning rod; 17, arc-shaped guide hole; 18, limit gear; 19, guide plate; 20, long strip-shaped guide hole. DETAILED DESCRIPTION

[0054] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the embodiments of the present application are further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present application and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application. The examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout.

[0055] It is to be understood that the terms "including", "comprising", "having" and their conjugates mean "including but not limited to", e.g. a process, method, object, or apparatus that comprises a list of steps or elements is not necessarily limited to those specifically listed and can include other steps or elements not expressly listed or inherent to such process, method, object, or apparatus.

[0056] The embodiments of the present application will be described in detail below with reference to the drawings.

[0057] As Figures 1-5 shown in the drawings, the automatic root cleaning machine for the girth weld in small-bore pipeline comprises a walking driving joint, a universal joint 8, a position-arriving tensioning joint and a polishing joint arranged coaxially in sequence from back to front, wherein the polishing joint comprises an integral rotating driving assembly connected with the position-arriving tensioning joint, the output end of the integral rotating driving assembly is connected with a polishing driving assembly through a first support frame 5, the output end of the polishing driving assembly is connected with a grinding wheel 2, a camera 1 is further arranged on the first support frame 5 and close to the grinding wheel 2, the camera 1 and the grinding wheel 2 are located on the same radial plane; the camera 1 is electrically connected with the driving joint, the integral rotating driving assembly and the polishing driving assembly through a control terminal, and is used for collecting the image of the inner wall of the small-bore pipeline to be cleaned by the camera 1, and driving the grinding wheel 2 to automatically clean the root after the driving joint, the integral rotating driving assembly and the polishing driving assembly are controlled by the control terminal.

[0058] It should be noted that the above electronic devices are all mature products in the market, and the present embodiment only needs to connect them according to the instructions after purchasing, and does not need to be improved, so the circuit connection structure and principle will not be described here.

[0059] The integral rotating driving assembly comprises an integral rotating driving motor 6 fixed on the position-arriving tensioning joint, a planetary gear 15 connected with the output end of the integral rotating driving motor 6, the gear ring of the planetary gear 15 is fixedly connected with one end of the first support frame 5, the other end of the first support frame 5 is eccentrically connected with a driving shaft, one end of the driving shaft is connected with the output end of the polishing driving assembly, the other end is fixedly connected with the grinding wheel 2, the polishing part of the grinding wheel 2 protrudes from the outer edge of the first support frame 5, a rotating gap is left between the grinding wheel 2 and the first support frame 5, and the polishing part of the grinding wheel 2 and the mounting position of the camera 1 are staggered; the grinding wheel 2 and the polishing driving assembly are arranged on both sides of the first support frame 5, and the polishing driving assembly is located inside the first support frame 5.

[0060] The polishing driving assembly comprises an electric push rod 4 fixed inside the first support frame 5 and a self-rotation polishing driving motor 3 connected with the output end of the electric push rod 4, and the output end of the self-rotation polishing driving motor 3 is fixedly connected with the driving shaft; a long strip-shaped guide hole 20 is formed on the first support frame 5, the long strip-shaped guide hole 20 is parallel to the electric push rod 4 and is penetrated by the driving shaft, and a rotation gap is left between the driving shaft and the inner wall of the long strip-shaped guide hole 20.

[0061] The walking driving section comprises a driving wheel side support 10 and a plurality of walking driving assemblies rotatably arranged on the outer circumferential side of the driving wheel side support 10, and the plurality of walking driving assemblies are all tire 9 structures provided with a hub motor.

[0062] The in-place tensioning section comprises a second support frame 7 and an in-place tensioning driving assembly arranged inside the second support frame 7, the in-place tensioning driving assembly comprises an in-place tensioning driving motor 13 fixed on the second support frame 7 and a driving gear disc 11 connected with the output end of the in-place tensioning driving motor 13, a plurality of arc-shaped guide holes 17 with the same direction are uniformly formed on the end face side of the driving gear disc 11, one end of the arc-shaped guide hole 17 is movably connected with a tensioning rod 16, the other end of the tensioning rod 16 is fixedly connected with a tensioning shoe 12 after penetrating out of a guide plate 19 fixed on the second support frame 7, the tensioning shoe 12 is fixed with a pressure sensor on the side facing the inner wall of the small-diameter pipeline to be cleaned, and the pressure sensor is in communication with a control terminal; the driving wheel side support 10 and the second support frame 7 are provided with a universal joint 8.

[0063] In the embodiment, a limiting gear 18 meshing with the driving gear disc 11 is further arranged.

[0064] A plurality of bull's eye bearings 14 are rotatably arranged on the outer circumferential side of the first support frame 5 and facing the inner wall of the small-diameter pipeline to be cleaned, and the bull's eye bearings 14 are in rolling contact with the inner wall of the small-diameter pipeline to be cleaned.

[0065] The lengths of the walking driving section, the in-place tensioning section and the polishing section are set as , and the maximum diameter is ; (the walking driving section, the in-place tensioning section and the polishing section are all separate functional sections);

[0066] The length of a single functional section is The small-diameter pipeline to be cleaned and the small-diameter pipeline to be cleaned satisfy the following constraint relationship:

[0067] ;

[0068] In the formula, represents the curvature radius of the elbow portion of the small-diameter pipeline to be cleaned; represents the radius of the straight pipe portion of the small-diameter pipeline to be cleaned; represents the bending angle of the elbow portion of the small-diameter pipeline to be cleaned, and when Time, Take 0.707;

[0069] With the small-caliber pipeline to be cleaned to meet the following constraint relationship:

[0070] ;

[0071] In the formula, The minimum safety gap between the set automatic root cleaning machine and the inner wall of the small-caliber pipeline to be cleaned;

[0072] At the same time, the diameter of the in-place expansion joint in the contracted state And the maximum diameter Also meet the following constraint relationship:

[0073] .

[0074] A working method of a small-caliber pipeline inner girth weld automatic root cleaning machine, comprising the following steps:

[0075] S1, the automatic root cleaning machine is sent into the inner wall of the small-caliber pipeline to be cleaned, and the walking drive joint is opened when the in-place expansion joint is in the contracted state, the tire 9 is driven by the in-wheel motor to drive the in-place expansion joint and the polishing joint to move along the inner wall of the small-caliber pipeline to be cleaned in the axial direction, in the process, the camera 1 is used to collect the image of the inner wall of the small-caliber pipeline to be cleaned, the weld position is determined according to the image of the inner wall of the small-caliber pipeline, the walking drive joint is closed, and the weld width and the target polishing depth are determined by the control terminal ;

[0076] In step S1, the camera 1 is used to collect the image of the inner wall of the small-caliber pipeline to be cleaned, and the gray scale difference value of the gray scale values of the two adjacent pixels in the axial direction is calculated after being converted to a gray scale image , and then the gray scale difference value is compared with the set gray scale threshold , if , it is determined that the weld position is reached, otherwise, it is determined that the weld position is not reached;

[0077] Wherein,

[0078] ;

[0079] In the formula, And Respectively represent the gray scale values of the two adjacent pixels in the axial direction.

[0080] S2, open to the position of the tensioning joint, to the position of the tensioning drive motor 13 drive gear plate 11 rotation, in turn, so that the tensioning rod 16 in the arc-shaped guide hole 17 radial movement, at this time in the arc-shaped guide hole 17 under the action of the guide, push out the tensioning rod 16, in turn, drive multiple tensioning boots 12 synchronous extension, until the pressure sensor collected tensioning force reaches the set tensioning force, close the tensioning drive motor;

[0081] S3, adjust the initial position: based on the target polishing depth, drive the electric push rod 4 drive sand wheel 2 along the long strip-shaped guide hole 20, until the inner ring of the weld is flush, close the electric push rod 4;

[0082] S4, start the rotation polishing drive motor 3, the overall rotation drive motor 6 and the electric push rod 4, the rotation polishing drive motor 3 drive sand wheel 2 rotation around the center of the shaft, while the overall rotation drive motor 6 drive polishing section overall rotation, electric push rod 4 drive sand wheel 2 radial feed so that sand wheel 2 with the set rotation speed and radial feed speed Polish until smooth;

[0083] In step S4, the set rotation speed and radial feed speed Satisfy the following relationship:

[0084] ;

[0085] In the formula, Indicates the calibration coefficient.

[0086] S5, control the contraction of the tensioning boots 12 of the to-position tensioning joint, and then open the wheel hub motor to drive the automatic root cleaning machine to push out the cleaned small diameter pipeline.

[0087] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application rather than limiting them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalent replacement of the technical solutions of the present application, and these modifications or equivalent replacement can not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A small-bore pipe girth weld automatic back gouging machine characterized by: The walking driving joint, the universal joint, the in-place tensioning joint and the polishing joint are coaxially arranged in sequence from back to front, wherein the polishing joint comprises an integral rotary driving assembly connected with the in-place tensioning joint, the output end of the integral rotary driving assembly is connected with a polishing driving assembly through a first support frame, the output end of the polishing driving assembly is connected with a grinding wheel, a camera is further arranged on the first support frame and close to the grinding wheel, and the camera and the grinding wheel are located on the same radial plane; The camera is electrically connected with the driving joint, the integral rotary driving assembly and the polishing driving assembly through a control terminal, is used for collecting the image of the inner wall of the small-diameter pipeline to be cleaned by the camera, and controls the driving joint, the integral rotary driving assembly and the polishing driving assembly to drive the grinding wheel to automatically clean the root after being processed by the control terminal; The length of the walking driving section, the in-place tensioning section and the polishing section is set as , and the maximum diameter is ; wherein the length The small-diameter pipeline to be cleaned satisfies the following constraint relationship: ； wherein, Rc represents the curvature radius of the elbow section of the small-diameter pipeline to be cleaned; Rl represents the radius of the straight section of the small-diameter pipeline to be cleaned; R represents the bending angle of the elbow section of the small-diameter pipeline to be cleaned, when Rc > Rl, 0.707; The small-diameter pipeline to be cleaned satisfies the following constraint relationship: ； In the formula, represents the minimum safety gap between the set automatic root cleaning machine and the inner wall of the small-diameter pipeline to be cleaned; At the same time, the diameter of the in-place tensioning joint in the contracted state satisfies the following constraint relationship: between the maximum diameter 。 2. The machine according to claim 1, characterized in that: The integral rotary driving assembly comprises an integral rotary driving motor fixed on the in-place tensioning joint, and a planetary gear connected with the output end of the integral rotary driving motor, the gear ring of the planetary gear is fixedly connected with one end of the first support frame, the other end of the first support frame is eccentrically connected with a driving shaft, one end of the driving shaft is connected with the output end of the polishing driving assembly, the other end is fixedly connected with the grinding wheel, the polishing part of the grinding wheel protrudes from the outer edge of the first support frame, and the polishing part of the grinding wheel and the mounting position of the camera are staggered. The grinding wheel and the polishing driving assembly are arranged on both sides of the first support frame, and the polishing driving assembly is arranged inside the first support frame.

3. A machine for automatic back gouging of girth welds in small diameter pipes according to claim 2, characterized in that: The polishing driving assembly comprises an electric push rod fixed inside the first support frame and a self-rotating polishing driving motor connected with the output end of the electric push rod, and the output end of the self-rotating polishing driving motor is fixedly connected with the driving shaft. A long strip-shaped guide hole is formed on the first support frame, the long strip-shaped guide hole is parallel to the electric push rod and is penetrated by the driving shaft, and a rotation gap is left between the driving shaft and the inner wall of the long strip-shaped guide hole.

4. A machine for automatic back gouging of girth welds in small diameter pipes according to claim 3, characterized in that: The walking driving joint comprises a driving wheel side support and a plurality of walking driving assemblies rotationally arranged on the outer circumferential side of the driving wheel side support, and the plurality of walking driving assemblies are all tire structures provided with wheel hub motors.

5. A machine for automatic back gouging of girth welds in small diameter pipes according to claim 4, characterized in that: The in-place tensioning joint comprises a second support frame and an in-place tensioning driving assembly arranged inside the second support frame, the in-place tensioning driving assembly comprises an in-place tensioning driving motor fixed on the second support frame and a driving gear disc connected with the output end of the in-place tensioning driving motor, a plurality of arc-shaped guide holes with the same direction are uniformly formed on the end face side of the driving gear disc, one end of the tensioning rod is movably connected with the arc-shaped guide holes, the other end of the tensioning rod is fixedly connected with a tensioning shoe after penetrating out of a guide plate fixed on the second support frame, a pressure sensor is fixed on the side of the tensioning shoe facing the small-diameter pipeline to be cleaned, and the pressure sensor communicates with the control terminal; A universal joint is arranged between the driving wheel side support and the second support frame.

6. A machine for automatic back gouging of girth welds in small diameter pipes according to claim 5, characterized in that: A plurality of bull's eye bearings are rotationally arranged on the outer circumferential side of the first support frame and facing the inner wall of the small-diameter pipeline to be cleaned, and the bull's eye bearings are in rolling contact with the inner wall of the small-diameter pipeline to be cleaned.

7. A method of operating a machine for automatically back gouging girth welds in small bore pipes as claimed in claim 6 wherein: The method comprises the following steps: S1, the automatic root machine is sent into the inner wall of the small-diameter pipeline to be cleaned, and the in-place expansion joint is in a contracted state. The walking drive joint is opened, the tire is driven by the in-wheel motor to drive the in-place expansion joint and the polishing joint to move axially along the inner wall of the small-diameter pipeline to be cleaned. In this process, the camera is used to collect the image of the inner wall of the small-diameter pipeline to be cleaned. According to the image of the inner wall of the small-diameter pipeline, it is determined that the weld position is reached. The walking drive joint is closed, and the control terminal is used to determine the weld width and the target polishing depth ; S2, open to the position of the tensioning joint, the drive motor to drive the gear plate rotation, and then make the tensioning rod in the arc-shaped guide hole radial movement, at this time under the guidance of the arc-shaped guide hole, push out the tensioning rod, and then drive a plurality of tensioning boots synchronous extension, until the pressure sensor collected tensioning force reaches the set tensioning force, close the tensioning drive motor; S3, adjust the initial position: based on the target polishing depth, drive the electric push rod to drive the grinding wheel to move along the long strip-shaped guide hole until it is flush with the inner ring of the weld, and then close the electric push rod; S4, start the rotation polishing driving motor, the whole rotation driving motor and the electric push rod, the rotation polishing driving motor drives the grinding wheel to rotate around the center of the rotation shaft, at the same time the whole rotation driving motor drives the polishing section to rotate as a whole, the electric push rod drives the grinding wheel to give in radially so that the grinding wheel rotates at a set speed and the radial feeding speed polishing until grinding S5, control the contraction of the tensioning boots of the to-position tensioning joint, and then open the wheel hub motor to drive the automatic root cleaning machine to push out the cleaned small diameter pipeline.

8. The working method of the automatic root-removing machine for girth welds in small-bore pipes according to claim 7, characterized in that: In step S1, the camera is used to collect the image of the inner wall of the small-diameter pipeline to be cleaned, and the gray difference value of the gray values of two adjacent pixels in the axial direction is calculated after being converted into a gray image , and the gray difference value is compared with the set gray threshold value If , it is determined that the weld position is reached, otherwise, it is determined that the weld position is not reached; Wherein, ； wherein and respectively represent the gray scale values of two pixels axially adjacent.

9. The working method of the automatic root-removing machine for girth welds in small-bore pipes according to claim 8, characterized in that: In step S4, the rotation speed is set satisfies the following relationship between the radial feed speed v and the radial feed speed ； In the formula, denotes a calibration coefficient.

Images