A method for controlling the size of large flanges

Abstract

The present invention relates to the field of offshore wind power technology, and in particular to a method for controlling the size of a large flange. The present invention controls the size of a large flange through four stages: interface preparation, welding preparation, welding and monitoring, and post-welding inspection. The welding process is combined with measurement technology, and the welding operation is adjusted in real time through the measurement data of the center tube and the flange, so as to achieve the purpose of natural forming of the inward-inclined welding of the large flange. During the welding process, the inner inclination of the flange is monitored, and the inner groove welding depth, the air planer root cleaning depth, and the number of outer groove welding are controlled according to the inclination value. At the same time, when welding the outer groove, the method of controlling the current size and the interlayer temperature is used for correction according to the degree of deformation. Finally, the order of covering the surface is determined according to the inclination value. The inclination value of the flange can be accurately controlled while welding, so that the inclination welding is naturally formed, and there is no need to perform surface machining after welding.

Description

Technical Field

[0001] The invention relates to the technical field of offshore wind power, and in particular to a method for controlling the size of a large flange. Background Art

[0002] In marine engineering, especially in the offshore wind power industry, large flanges with a diameter of more than six meters are commonly used in wind power generation pipe frames. At the same time, there are special requirements for the surface shape and flatness of the flanges. After the flanges are welded, a certain inclination value needs to be formed to optimize the mechanical properties of the flanges. At present, in the industry, such large flanges need to be machined on the surface after welding to form an inclination shape that meets the requirements. The processing technology is complicated and the installation period is prolonged. Summary of the invention

[0003] To achieve the above object, the present invention provides a method for controlling the size of a large flange, comprising the following steps:

[0004] S100, preparation of the docking interface: select flanges with reserved processing allowances, process the inner and outer bevels at the edge of the docking interface of the center tube; measure the ovality, circumference and horizontality of the docking interface of the center tube, and mark identification lines at the corresponding positions of the outer wall of the lower opening of the flange and the outer wall of the upper opening of the center tube. The identification lines can divide the flange into multiple equal parts;

[0005] S200, welding preparation: fix the center tube, align the flange with the center tube, and fix it by spot welding at the inner groove; measure the overall ovality and bolt hole spacing of the flange bolt hole group, as well as the inner inclination, horizontality and flatness of the flange;

[0006] S300, welding and monitoring: preheat the flange; start welding from the inner groove, if the inner inclination value of the flange exceeds the preset value, stop welding and mark the area; if the inner inclination value of the flange does not exceed the preset value, continue welding until the inner groove welding is completed; perform air planing to clean the outer groove, and weld the outer groove after the magnetic particle test is qualified; during the welding of the outer groove, control the current size and interlayer temperature to correct the area with large deformation, and finally perform the cover weld; monitor the inner inclination data of the flange throughout the welding process, and make welding adjustments based on the inner inclination data;

[0007] S400, post-welding inspection: inspect the overall ovality and bolt hole spacing of the flange bolt hole group, and the internal inclination, horizontality, flatness and thickness of the flange.

[0008] In some possible implementations, step S300 specifically includes:

[0009] S310, preheating the flange, detecting the surface shape of the flange, and comparing and analyzing the flange inclination data measured in step S200, and locally adjusting the preheating temperature of the corresponding area according to the deformation of each equally divided area of ​​the flange;

[0010] S320, start welding from the inner groove, stop welding when welding reaches 1 / 3 of the inner groove depth, measure the deformation of each area of ​​the flange end face and record the inclination data of each equally divided area; when the inclination data is greater than 4mm, stop welding and mark the area; when the inclination data is less than or equal to 4mm, continue welding to 2 / 3 of the inner groove depth, measure and record the inclination data;

[0011] S330, according to the inclination data values ​​of different equally divided areas, start from the outer groove to perform air planing and root cleaning; after the root cleaning and grinding, perform magnetic particle inspection, if the magnetic particle inspection fails, repair welding is performed on the inner groove; after the magnetic particle inspection passes, continue welding the outer groove;

[0012] S340, after welding three layers of outer groove, measure the deformation of flange end face and inclination data, and in the welding process, take the method of controlling current size and interlayer temperature to correct the area with large deformation; when the inclination data is greater than 2mm, welding is completed; when the inclination data is less than 2mm, continue welding three layers after cooling; according to the above method, measure the inclination data once every three layers of welding and perform corresponding welding operations;

[0013] S350, perform cover welding. If the inclination data of the flange is greater than 1mm, weld the weld of the outer groove cover first; if the inclination data is less than or equal to 1mm, weld the weld of the inner groove cover first; after the cover welding is completed, measure the inclination data of the flange again, and perform repair welding based on the inclination data.

[0014] In some possible implementations, in step S310, the flange surface shape is detected by:

[0015] S311, use the method of pulling powder line to lock several angle directions for measurement;

[0016] S312. Use a steel ruler to measure the height difference between the inner and outer diameters of the flange and the change in overall flatness. The height difference between the inner and outer diameters of the flange is equal to the inclination data.

[0017] In some possible implementations, in step S330, when the air planing is performed, the width and depth of the air planing are kept consistent for the parts with the same inclination data; and the depth of the air planing is increased for the parts with increased inclination data.

[0018] In some possible implementations, in step S340, the method for correcting the outer groove welding is: in the equally divided areas where the shrinkage needs to be increased, the welding current and the interlayer temperature are increased; in the equally divided areas where the shrinkage needs to be controlled, the welding current and the interlayer temperature are reduced.

[0019] In some possible implementations, in step S310, the specific operations of preheating the flange are as follows: heating the flange, first raising the heating temperature to the maximum value, installing a total station on the fixed platform tooling at the center of the flange, detecting the surface shape of the flange after heating, and comparing and analyzing the data with the data before heating, analyzing and obtaining the degree of thermal deformation of each equally divided area of ​​the flange and marking the thermal expansion deformation sequence of each equally divided area; finally, reducing the heating temperature to the minimum value and waiting for welding.

[0020] In some possible implementations, in step S340, the requirements for outer groove welding include: the outer groove welding should be performed from the inside to the outside and in separate passes and sequences until the welding depth requirement is reached.

[0021] In some possible implementations, in step S100,

[0022] The method for measuring the ellipticity of the upper interface of the center tube is as follows: set up the total station inside the center tube, evenly measure several equally divided points in a circle close to the upper position, and use the least square method to find the optimal center of the circle. The ellipticity calculation formula is the difference between the maximum diameter and the minimum diameter, and calculate its ellipticity;

[0023] The method for measuring the level of the upper butt joint of the center tube is as follows: place a small prism on the tip of the butt joint groove, evenly place several equally divided points in a circle, and measure with a total station to obtain the horizontal data of the butt joint;

[0024] The method for measuring the circumference of the center tube interface is: make a mark point 100mm below the tip of the groove on the outer wall of the center tube in advance, divide a circle into several equal points, use a ruler to circle the outer wall of the center tube along the marked points to get the circumference.

[0025] In some possible implementations, in step S200,

[0026] The method for measuring the overall ellipticity and bolt hole spacing of the flange bolt hole group is as follows: set up the total station at a position where the entire flange upper surface can be seen, use auxiliary tooling and prisms to measure the centers of several equally divided bolt holes, use the least squares method to find the optimal circle center, and calculate its ellipticity and bolt hole spacing;

[0027] The method for measuring the internal inclination and level of the flange is: use a total station and a laser plane to monitor the internal inclination, level and flatness of the flange, and adjust them to meet the tolerance requirements.

[0028] In some possible implementations, in step S100, the ovality of the center tube should be controlled within 5 mm, and the misalignment between the center tube and the flange should be controlled within 3 mm.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention controls the size of a large flange through four stages: interface preparation, welding preparation, welding and monitoring, and post-welding inspection. The welding process is combined with measurement technology, and the welding operation is adjusted in real time through measurement data of the center tube and the flange, thereby achieving the purpose of natural forming of the inward-inclined welding of the large flange.

[0031] Before the joint, the data of the center tube and the flange joint are determined by measurement to ensure that the misalignment between the center tube and the flange is within 3mm during the joint, and the flange flatness is controlled in advance; during the welding process, the inner inclination of the flange is monitored, and the inner groove welding depth, the air planer root cleaning depth and the number of outer groove welding are controlled according to the inclination value. At the same time, when welding the outer groove, the current size and interlayer temperature are controlled according to the degree of deformation. Finally, the order of covering is determined according to the inclination value. The inclination value of the flange can be accurately controlled during welding, so that the inclination welding is naturally formed, and there is no need to perform surface machining after welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A flow chart of a method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the following, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "multiple" means two or more.

[0035] Reference Figure 1 A method for controlling the size of a large flange is shown, comprising the following steps:

[0036] S100, preparation of the docking interface: select flanges with reserved processing allowances, process the inner and outer bevels at the edge of the docking interface of the center tube; measure the ovality, circumference and horizontality of the docking interface of the center tube, and mark identification lines at the corresponding positions of the outer wall of the lower opening of the flange and the outer wall of the upper opening of the center tube. The identification lines can divide the flange into multiple equal parts;

[0037] S200, welding preparation: fix the center tube, align the flange with the center tube, and fix it by spot welding at the inner groove; measure the overall ovality and bolt hole spacing of the flange bolt hole group, as well as the inner inclination, horizontality and flatness of the flange;

[0038] S300, welding and monitoring: preheat the flange; start welding from the inner groove, if the inner inclination value of the flange exceeds the preset value, stop welding and mark the area; if the inner inclination value of the flange does not exceed the preset value, continue welding until the inner groove welding is completed; perform air planing to clean the outer groove, and weld the outer groove after the magnetic particle test is qualified; during the welding of the outer groove, control the current size and interlayer temperature to correct the area with large deformation, and finally perform the cover weld; monitor the inner inclination data of the flange throughout the welding process, and make welding adjustments based on the inner inclination data;

[0039] S400, post-welding inspection: inspect the overall ovality and bolt hole spacing of the flange bolt hole group, and the internal inclination, horizontality, flatness and thickness of the flange.

[0040] Among them, in the step S100, considering the overall deformation of the flange, if the welding fails to naturally form the inward inclination value that meets the specifications, the surface repair by machining can be carried out. Therefore, when selecting the flange, the thickness of the flange itself can be increased by a margin of about 4 mm, while ensuring that the thickness is 4 mm greater than the theoretical value and does not affect the functional use of the flange.

[0041] In some possible implementations, in step S100, the method for measuring the ellipticity of the upper interface of the center tube is: set up the total station inside the center tube, and evenly measure a number of equally divided points in a circle close to the upper position, and use the least squares method to find the optimal center of the circle. The ellipticity calculation formula is the difference between the maximum diameter and the minimum diameter, and its ellipticity is calculated; the method for measuring the level of the upper interface of the center tube is: place a small prism on the tip of the groove of the docking interface, evenly place a number of equally divided points in a circle, and measure with a total station to obtain the horizontal data at the docking interface; the method for measuring the circumference of the center tube docking interface is: make a marking point 100 mm below the tip of the groove on the outer wall of the center tube in advance, divide a circle into a number of equally divided points, and use a ruler to circle the outer wall of the center tube along the marking point to obtain the circumference.

[0042] Among them, when measuring the ovality, horizontality and circumference of the center tube, it can be divided into 32 or more points for measurement, that is, the center tube is divided into 32 or more points, which is convenient for measurement and improves the accuracy of the measurement data. Further, after measuring the circumference of the center tube, the outer wall of the center tube can be marked with 0°, 90°, 180°, and 270° marking lines according to the actual circumference, and the flange is also marked with 0°, 90°, 180°, and 270° marking lines accordingly, so that the flange and the center tube can be hoisted and aligned later. In addition, in order to control the deformation of the flange in advance, after the above-mentioned measurement, in the step S100, the ovality of the center tube should be controlled within 5mm, and the docking misalignment of the center tube and the flange should be within 3mm. In addition, the root gap of the group pair should be as small as possible, and the smaller the gap, the more conducive it is to control the flatness of the flange.

[0043] In some possible implementations, in step S200, before assembling the flange, an I-beam should be used to support the inside of the center tube, specifically a M-shaped I-beam, to ensure that the flange has no restraining force on the center tube during assembly, and to try to ensure that no other factors other than the welding heat input will cause deformation of the flange.

[0044] Further, in step S200, the method for measuring the ellipticity and bolt hole spacing of the flange bolt hole group as a whole is as follows: the total station is set up at a position where the entire upper surface of the flange can be seen, and the auxiliary tooling and prism are used to measure the centers of several equally divided bolt holes, and the data are used to find the optimized circle center by the least square method, and the ellipticity and bolt hole spacing are calculated; the method for measuring the inclination and level of the flange is as follows: the inclination, level and flatness of the flange are monitored by the total station and the laser plane, and adjusted to meet the tolerance requirements. Among them, when measuring the ellipticity and bolt hole spacing of the flange bolt hole group as a whole, the centers of 78 bolt holes should be measured, and the flange has a total of 156 bolt holes, that is, one bolt hole is measured every other hole, and the flange is divided into 78 equal parts.

[0045] In some possible implementations, step S300 specifically includes:

[0046] S310, preheating the flange, detecting the surface shape of the flange, and comparing and analyzing the flange inclination data measured in step S200, and locally adjusting the preheating temperature of the corresponding area according to the deformation of each equally divided area of ​​the flange;

[0047] S320, start welding from the inner groove, stop welding when welding reaches 1 / 3 of the inner groove depth, measure the deformation of each area of ​​the flange end face and record the inclination data of each equally divided area; when the inclination data is greater than 4mm, stop welding and mark the area; when the inclination data is less than or equal to 4mm, continue welding to 2 / 3 of the inner groove depth, measure and record the inclination data;

[0048] S330, according to the inclination data values ​​of different equally divided areas, start from the outer groove to perform air planing and root cleaning; after the root cleaning and grinding, perform magnetic particle inspection, if the magnetic particle inspection fails, repair welding is performed on the inner groove; after the magnetic particle inspection passes, continue welding the outer groove;

[0049] S340, after welding three layers of outer groove, measure the deformation of flange end face and inclination data, and in the welding process, take the method of controlling current size and interlayer temperature to correct the area with large deformation; when the inclination data is greater than 2mm, welding is completed; when the inclination data is less than 2mm, continue welding three layers after cooling; according to the above method, measure the inclination data once every three layers of welding and perform corresponding welding operations;

[0050] S350, perform cover welding. If the inclination data of the flange is greater than 1mm, weld the weld of the outer groove cover first; if the inclination data is less than or equal to 1mm, weld the weld of the inner groove cover first; after the cover welding is completed, measure the inclination data of the flange again, and perform repair welding based on the inclination data.

[0051] Among them, in the step S310, the specific operation of preheating the flange is as follows: heating the flange, first raising the heating temperature to the upper limit value, installing the total station on the fixed platform tooling at the center of the flange, detecting the surface shape of the flange after heating, and comparing and analyzing the data before heating, analyzing and obtaining the degree of thermal deformation of each equally divided area of ​​the flange and marking the thermal expansion deformation sequence of each equally divided area; finally, reducing the heating temperature to the minimum value and waiting for welding. Among them, when preheating the flange, the heating temperature is raised to the upper limit value, and preheating can eliminate some welding stress to a certain extent, which is convenient for the subsequent welding operation. In addition, due to the uneven quality inside the flange workpiece, the surface shape of each part of the flange will change differently after preheating. After preheating, the surface shape and thermal expansion deformation data are detected, which is convenient for the operator to record the heat influence of each area of ​​the flange in advance, so as to adjust the welding temperature of each area in the subsequent welding process.

[0052] Specifically, in step S310, the method for measuring the surface shape of the flange is as follows: S311, using the method of pulling a powder line, locking several angle directions for measurement; S312, using a steel ruler to measure the inclination data, comparing the height difference between the inner and outer diameters of the flange and the overall flatness change, the height difference between the inner and outer diameters of the flange is equal to the inclination data value. Among them, the flange is locked at 0°, 90°, 180° or 270° by pulling a powder line to perform multi-area measurements, and determine the temperature change of the shape of each area of ​​the flange; in addition, in addition to using the method of pulling a powder line, the total station optical eyepiece can also be used to lock the measurement direction. Furthermore, when detecting the surface shape of the flange after preheating, a heat-insulating material can be used to block the flange heat wave to prevent it from affecting the data.

[0053] In some possible implementations, in step S330, when the gouging is performed, the width and depth of the gouging are kept consistent for the parts with the same inclination data; the depth of the gouging is increased for the parts with increased inclination data. Gouging is performed to remove defects at the root of the weld, such as pores, pits and impurities; and a suitable welding groove is formed at the same time. In step S330, magnetic particle testing, i.e., MT testing, is performed to observe the defects of the weld using magnetic particles as a display medium, and the position, size, shape and severity of discontinuity when welding the inner groove are determined by testing, so as to continue welding the outer groove after the repair welding is qualified.

[0054] In some possible implementations, in step S340, in the equally divided areas where the shrinkage needs to be increased, the welding current and interlayer temperature are increased; in the equally divided areas where the shrinkage needs to be controlled, the welding current and interlayer temperature are reduced. At the same time, it is necessary to ensure that the current and interlayer temperature are within the specified range, so that the purpose of continuously correcting the inclination value of the flange can be achieved during the welding process. In step S340, the inclination data measured after welding three layers of the outer groove is marked on the flange according to several equal parts, so that the welding can be compared in different areas during the next round of welding. In addition, the requirements for outer groove welding include: the outer groove should be welded from the inside to the outside and in separate lanes and sequences until the welding depth requirements are reached.

[0055] The present invention controls the size of a large flange through four stages of interface preparation, welding preparation, welding and monitoring, and post-welding inspection, combines the welding process with the measurement technology, and adjusts the welding operation in real time through the measurement data of the center tube and the flange, so as to achieve the purpose of natural forming of the inward-inclined welding of the large flange. Before the interface, the data of the center tube and the flange interface are determined by measurement to ensure that the misalignment of the center tube and the flange during docking is within 3mm, and the flange flatness is controlled in advance; during the welding process, the inclination of the flange is monitored, and the welding depth of the inner groove, the depth of the air planer root cleaning, and the number of outer groove welding are controlled according to the inclination value. At the same time, when welding the outer groove, the method of controlling the current size and the interlayer temperature is adopted for correction according to the degree of deformation. Finally, the order of the cover is determined according to the inclination value. The inclination value of the flange can be accurately controlled during welding, so that the inclination welding is naturally formed, and there is no need to perform surface machining after welding.

[0056] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for controlling the size of a large flange. It is characterized in that The following steps are involved: S100, preparation of the docking interface: select flanges with reserved processing allowances, process the inner and outer bevels at the edge of the docking interface of the center tube; measure the ovality, circumference and horizontality of the docking interface of the center tube, and mark identification lines at the corresponding positions of the outer wall of the lower opening of the flange and the outer wall of the upper opening of the center tube. The identification lines can divide the flange into multiple equal parts; S200, welding preparation: fix the center tube, align the flange with the center tube, and fix it by spot welding at the inner groove; measure the overall ovality and bolt hole spacing of the flange bolt hole group, as well as the inner inclination, horizontality and flatness of the flange; S300, welding and monitoring: preheat the flange; start welding from the inner groove, if the inner inclination value of the flange exceeds the preset value, stop welding and mark the area; if the inner inclination value of the flange does not exceed the preset value, continue welding until the inner groove welding is completed; perform air planing to clean the outer groove, and weld the outer groove after the magnetic particle test is qualified; during the welding of the outer groove, control the current size and interlayer temperature to correct the area with large deformation, and finally perform the cover weld; monitor the inner inclination data of the flange throughout the welding process, and make welding adjustments based on the inner inclination data; S400, post-welding inspection: inspect the overall ovality and bolt hole spacing of the flange bolt hole group, and the internal inclination, horizontality, flatness and thickness of the flange.

2. A method for controlling the size of a large flange according to claim 1, It is characterized in that The step S300 specifically includes: S310, preheating the flange, detecting the surface shape of the flange, and comparing and analyzing the flange inclination data measured in step S200, and locally adjusting the preheating temperature of the corresponding area according to the deformation of each equally divided area of ​​the flange; S320, start welding from the inner groove, stop welding when welding reaches 1 / 3 of the inner groove depth, measure the deformation of each area of ​​the flange end face and record the inclination data of each equally divided area; when the inclination data is greater than 4mm, stop welding and mark the area; when the inclination data is less than or equal to 4mm, continue welding to 2 / 3 of the inner groove depth, measure and record the inclination data; S330, according to the inclination data values ​​of different equally divided areas, start from the outer groove to perform air planing and root cleaning; after the root cleaning and grinding, perform magnetic particle inspection, if the magnetic particle inspection fails, repair welding is performed on the inner groove; after the magnetic particle inspection passes, continue welding the outer groove; S340, after welding three layers of outer groove, measure the deformation of flange end face and inclination data, and in the welding process, take the method of controlling current size and interlayer temperature to correct the area with large deformation; when the inclination data is greater than 2mm, welding is completed; when the inclination data is less than 2mm, continue welding three layers after cooling; according to the above method, measure the inclination data once every three layers of welding and perform corresponding welding operations; S350, perform cover welding. If the inclination data of the flange is greater than 1mm, weld the weld of the outer groove cover first; if the inclination data is less than or equal to 1mm, weld the weld of the inner groove cover first; after the cover welding is completed, measure the inclination data of the flange again, and perform repair welding based on the inclination data.

3. A method for controlling the size of a large flange according to claim 2, It is characterized in that In step S310, the flange surface shape is detected by: S311, use the method of pulling powder line to lock several angle directions for measurement; S312. Use a steel ruler to measure the height difference between the inner and outer diameters of the flange and the change in overall flatness. The height difference between the inner and outer diameters of the flange is equal to the inclination data.

4. A method for controlling the size of a large flange according to claim 2, It is characterized in that In step S330, when the air planing is performed, the width and depth of the air planing are kept consistent for the parts with the same inward inclination data; and the depth of the air planing is increased for the parts with increased inward inclination data.

5. A method for controlling the size of a large flange according to claim 2, It is characterized in that In step S340, the method for correcting the outer groove welding is: in the equally divided area where the shrinkage needs to be increased, the welding current and the interlayer temperature are increased; in the equally divided area where the shrinkage needs to be controlled, the welding current and the interlayer temperature are reduced.

6. A method for controlling the size of a large flange according to claim 2 or 5, It is characterized in that In the step S310, the specific operation of preheating the flange is as follows: heating the flange, firstly raising the heating temperature to the maximum value, installing a total station on the fixed platform tooling at the center of the flange, detecting the surface shape of the flange after heating, and comparing and analyzing the data before heating, analyzing and obtaining the degree of thermal deformation of each equally divided area of ​​the flange and marking the thermal expansion deformation sequence of each equally divided area; Finally, lower the temperature to the lowest value and wait for welding.

7. A method for controlling the size of a large flange according to claim 2 or 5, It is characterized in that In step S340, the requirements for outer groove welding include: the outer groove welding should be performed from the inside to the outside and in separate passes and sequences until the welding depth requirement is reached.

8. A method for controlling the size of a large flange according to claim 1, It is characterized in that In the step S100, The method for measuring the ellipticity of the upper interface of the center tube is as follows: set up the total station inside the center tube, evenly measure several equally divided points in a circle close to the upper position, and use the least square method to find the optimal center of the circle. The ellipticity calculation formula is the difference between the maximum diameter and the minimum diameter, and calculate its ellipticity; The method for measuring the level of the upper butt joint of the center tube is as follows: place a small prism on the tip of the butt joint groove, evenly place several equally divided points in a circle, and measure with a total station to obtain the horizontal data of the butt joint; The method for measuring the circumference of the center tube interface is: make a mark point 100mm below the tip of the groove on the outer wall of the center tube in advance, divide a circle into several equal points, use a ruler to circle the outer wall of the center tube along the marked points to get the circumference.

9. A method for controlling the size of a large flange according to claim 1, It is characterized in that In the step S200, The method for measuring the overall ellipticity and bolt hole spacing of the flange bolt hole group is as follows: set up the total station at a position where the entire flange upper surface can be seen, use auxiliary tooling and prisms to measure the centers of several equally divided bolt holes, use the least squares method to find the optimal circle center, and calculate its ellipticity and bolt hole spacing; The method for measuring the internal inclination and level of the flange is: use a total station and a laser plane to monitor the internal inclination, level and flatness of the flange, and adjust them to meet the tolerance requirements.

10. A method for controlling the size of a large flange according to claim 8, It is characterized in that In the step S100, the ovality of the center tube should be controlled within 5 mm, and the misalignment between the center tube and the flange should be controlled within 3 mm.

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