A method for repairing the irregularity defect of the journal of a steam turbine rotor

Abstract

The present invention provides a method for repairing the non-cylindricity defect of a turbine rotor journal, the method comprising the following steps: S1, measuring the diameter size and straightness of the rotor before repair and dividing the rotor journal repair area; S2, installing a special grinding tool in the journal repair area to grind and polish the rotor journal; S3, after the rotor journal repair is completed, removing the grinding tool, measuring the journal size with an outside diameter micrometer, and ensuring that the rotor journal diameter size meets the tolerance requirements; S4, installing the bearing, measuring the straightness and end face circular runout of the rotor journal at different phases with a measuring tool, and ensuring that the straightness and end face circular runout sizes meet the tolerance requirements. The present invention can repair the non-cylindricity of the rotor journal without returning to the factory for repair, ensuring the use accuracy, and has the advantages of short cycle and low cost.

Description

Technical Field

[0001] The invention mainly relates to the technical field related to steam turbine repair, and specifically is a method for repairing the irregularity defect of a steam turbine rotor journal. Background Art

[0002] The steam turbine is used in power generation projects and is located between the generator and the condenser. The steam turbine has a shaft at the high-pressure end, and the turbine shaft and the generator shaft are connected by a self-synchronizing coupling. During actual use, the key factory data of the steam turbine needs to be checked regularly. When there is a deviation in the non-column degree of the shaft neck at the electric end of the medium and low-pressure rotors, it needs to be repaired in time. For example, when the applicant of this application measured the shaft neck at the electric end of the medium and low-pressure rotors in the project, it was found that the non-column degree of the shaft neck at the electric end of the medium and low-pressure rotors was 0.045mm, which exceeded the specified 0.02mm and was a serious deviation, so it needed to be dealt with in time.

[0003] In the existing technology, when there is a problem of misalignment, the solution is to return the machine to the factory or find a local large-scale machine processing factory for turning and reassembly of the bearing. For example, the investigation found that during the new installation of Power Plant A, the shaft neck misalignment of Unit 1 was unqualified, and the main engine factory's on-site repair did not meet the requirements of the regulations. It was eventually returned to the factory for processing. After returning to the factory, the shaft neck was turned and the bearing was reassembled. The main engine factory promised to provide non-standard bearing spare parts in the future.

[0004] In the above-mentioned treatment plan, it is necessary to dismantle the medium and low pressure cylinders on site, return the medium and low pressure rotors to the factory for turning, and re-assemble the bearings according to the size of the repaired journal after turning, which will result in a long time period and extremely high cost. The estimated cost is about 1 million and the cycle is about 65 days. Because the on-site main engine installation work needs to be completely stopped, the feasibility is relatively low. Therefore, the applicant of this application proposed to use manual grinding to repair the non-columnar problem. During the grinding process, if sandpaper is used directly for grinding, it is difficult to control the angle and strength, and the situation after repair cannot be controlled. In addition, the space of the bearing chamber is small, and the grinding space is insufficient, so the feasibility is low. Therefore, it is necessary to design an effective repair method to solve the problem of non-columnar defects in the turbine shaft journal. Summary of the invention

[0005] In order to solve the shortcomings of current technology, the present invention combines the existing technology and, based on practical application, provides a method for repairing the unevenness of the turbine rotor journal. The method can repair the unevenness of the rotor journal without returning it to the factory for repair, thereby ensuring the accuracy of use and having the advantages of short cycle and low cost.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for repairing a turbine rotor journal irregularity defect, the method comprising the following steps:

[0008] S1. Measure the diameter and straightness of the rotor before repair and divide the rotor journal repair area;

[0009] S2. Install the special grinding tool in the journal maintenance area to grind and polish the rotor journal.

[0010] The grinding tool comprises two independent semi-circular hoops, sandpaper is pasted on the inner circumference of the two semi-circular hoops, and the two semi-circular hoops are fastened by a tightening belt wrapped around the outer circumference. A pull rope is connected to each semi-circular hoop, and the operator pulls the pull rope to rotate the semi-circular hoop to grind the rotor shaft neck;

[0011] S3. After the rotor journal is repaired, remove the grinding tooling and measure the journal size with an outside micrometer to ensure that the rotor journal diameter meets the tolerance requirements;

[0012] S4. Install the bearings and use measuring tools to measure the straightness and end face runout of the rotor journal at different phases to ensure that the straightness and end face runout dimensions meet the tolerance requirements.

[0013] Wherein, the measuring tool comprises a guide rail group and a reference gauge arranged on one side of the rotor, the reference gauge is installed on the guide rail group, and the guide rail group is installed on the center plane of the bearing seat.

[0014] Further, step S2 specifically includes:

[0015] S21. Install 120-grit sandpaper in the two half-hoops respectively, set the half-hoops on the rotor journal, and tighten the two half-hoops to a suitable strength by tightening the straps;

[0016] S22. Two operators pull the rope back and forth on both sides of the rotor to drive the semi-encircling hoop to rotate evenly, and grind the rotor shaft neck with sandpaper. During the grinding process, the tightening force of the semi-encircling hoop is monitored, and the tightening force is increased in time when the force is insufficient;

[0017] S23, loosen the tightening belt every 5 minutes, measure the journal size of the grinding area, if the size does not reach the set size, replace the new sandpaper and continue grinding until the journal size reaches the set size;

[0018] S24. Replace the sandpaper model with 150 mesh, repeat the grinding process, and move the semi-hoop axially repeatedly until the surface finish of the journal reaches Ra0.4.

[0019] Furthermore, in step S21, the tightening force of the binding belt is controlled so that the tightening force at the large end of the journal taper is slightly greater than that at the small end of the taper, and the tightening force of the entire section is appropriate for the operator to be able to push the clamp to rotate with a little force.

[0020] Further, in step S22, each pulling requires that the half-hoop rotation angle is not less than 120 degrees, and the rotation frequency is about 30 times per minute.

[0021] Furthermore, the semi-encircling hoop is made of nylon.

[0022] Furthermore, a plurality of clamping grooves are provided on each semi-encircling hoop, and the clamping grooves are provided along the outer circumferential contour of the semi-encircling hoop, and the binding belts are wound in the clamping grooves.

[0023] Furthermore, the length of the sandpaper satisfies: extending outward from the inner circular surface of the semi-encircling hoop to the center plane of the semi-encircling hoop, so that the sandpaper can be fixed by a pressure plate arranged at the center plane, and the pressure plate is connected to the center plane of the semi-encircling hoop by fastening screws.

[0024] Further, the measuring tool specifically includes a transition plate, a guide rail, a support plate and a gauge, the transition plate is arranged on one side of the rotor and fixedly connected to the center plane of the bearing seat, the guide rail is fixedly connected to the transition plate by bolts, the support plate and the guide rail are slidably matched, and the gauge is arranged on the support plate;

[0025] In step S4, the straightness of the outer circle of the repaired journal is measured with the outer circle of the thrust plates on both sides of the rotor journal as a reference. During the measurement process, the support plate is first adjusted to be parallel to the rotor axis, and then the straightness is measured by a gauge.

[0026] Further, in step S4, the measuring method specifically includes the following steps:

[0027] S41. Pick any point A and point B on the outer circle of the thrust plates on both sides. The distance between the two points AB is L0. Measure the outer diameters of the two points, which are recorded as A0 and B0 respectively. Calculate the difference and divide it by 2, which is recorded as C0.

[0028] S42. Install the transition plate on the center surface of the bearing seat through connecting bolts;

[0029] S43, setting the guide rail on the transition plate, adsorbing the table on the surface of the support plate, and controlling the distance between the table and the rotor so that the table needle contacts the rotor surface;

[0030] S44. Slightly fix the guide rail with the fixing bolts so that the meter reading does not change significantly when the support plate is manually shaken;

[0031] S45, push the support plate to move along the guide rail, make the gauge pointer contact the thrust inventory point A on one side, and clear the gauge reading;

[0032] S46, push the pallet to move along the guide rail, make the gauge pointer contact the thrust inventory point B on the other side, and record the gauge reading as D0;

[0033] S47, calculate the parallelism deviation value between the support plate and the rotor axis, and record it as E0, E0=ARCTAN((D0-C0) / L0);

[0034] S48, knock the guide rail with a copper rod to make it swing to a certain angle, continue to push the support plate to observe the reading of point B with point A as the 0 point, and repeat the above operation until the reading of the guide rail D0 = C0;

[0035] S49, tighten the guide rail connecting bolts symmetrically;

[0036] S410, continue to push the support plate and observe the reading of point B with point A as the zero point to confirm that the parallelism of the support plate is parallel to the rotor axis at this time;

[0037] S411, put the pointer of the gauge in contact with the outer circle of the journal, take the leftmost outer circle as the zero point, push the support plate to measure the gauge reading jump of the entire outer circle of the journal, and the maximum value is the straightness deviation value;

[0038] S412. Rotate the rotor and measure the straightness of the journal at different phases.

[0039] Further, in step S412, the rotor is rotated in units of 30 degrees to measure the straightness of the rotor journals of 12 phases of 360 degrees to ensure that the straightness of the rotor journals of the 12 phases meets the design dimensions.

[0040] Beneficial effects of the present invention:

[0041] 1. The present invention proposes for the first time to solve the problem of unevenness of the turbine rotor journal by manual grinding. With the specially designed grinding tool, the rotor journal can be ground quickly and accurately to meet the size requirements. Practice has proved that the method provided by the present invention does not require cylinder repair and can ensure grinding accuracy and effect.

[0042] 2. The repair method provided by the present invention is combined with the design of a special grinding tool. In the repair of rotor bearings, the overall cost is low and the grinding accuracy can be guaranteed. Through the special measuring tools and measuring methods provided, high-precision and rapid measurement of the rotor journal after repair can be achieved to ensure the reliability of the measured dimensions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Attached Figure 1 It is a step diagram of the repair method of the present invention;

[0044] Attached Figure 2 The grinding tool structure of the present invention is schematically shown Figure 1 ;

[0045] Attached Figure 3 The grinding tool structure of the present invention is schematically shown Figure 2 ;

[0046] Attached Figure 4 It is a schematic diagram of the structure of the measuring tool of the present invention.

[0047] Numbers shown in the accompanying drawings:

[0048] 1. Half hoop; 2. Sandpaper; 3. Pressing plate; 4. Handle; 5. Pressing groove; 6. Fastening screw. DETAILED DESCRIPTION

[0049] The present invention will be further described with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the application.

[0050] This embodiment provides a method for repairing the non-cylindrical defect of a steam turbine rotor journal, which is mainly used to repair the non-cylindrical defect of the rotor journal. In this embodiment, the repair steps are mainly as follows: Figure 1 shown.

[0051] First, measure the diameter and straightness of the rotor before repair and divide the rotor journal repair area:

[0052] The on-site measurement shows that the non-column of the shaft neck at the electric end of the medium and low pressure rotor is 0.045mm, so there is a large error. The area with the large error is measured and found as the maintenance area for repair.

[0053] Secondly, repair by manual grinding:

[0054] The medium and low pressure rotors of the generator set are currently in place in the bearing seat. The space of the bearing seat is narrow, so a grinding clamp is used to repair the out-of-tolerance parts of the rotor in the bearing seat. For this purpose, this embodiment designs a special grinding tool for journal grinding.

[0055] The special grinding tool structure provided in this embodiment is as follows Figure 2 , Figure 3 shown.

[0056] It mainly includes two independent semi-encircling hoops 1, the width of the semi-encircling hoop 1 is 100mm, the gap between the inner circle and the shaft neck is 0.5mm on one side, and the thickness is 50mm. Sandpaper 2 is attached to the inner circle surface of the semi-encircling hoop 1, and a handle 4 for installing a rope is provided on the outer circle surface of each semi-encircling hoop 1. The two semi-encircling hoops 1 are fastened by a tightening belt wrapped around the outer circle surface of the semi-encircling hoop 1. The base material of the semi-encircling hoop 1 is nylon, which can play a role in protecting the shaft neck during grinding. After the rope is installed on the handle 4, the staff pulls the rope at a uniform speed to rotate the semi-encircling hoop 1 and then grinds the surface of the shaft neck through the sandpaper 2 on the inside.

[0057] In this embodiment, four clamping grooves 5 are further provided on each semi-encircling hoop 1. The clamping grooves 5 are provided along the outer circumferential surface contour of the semi-encircling hoop 1. The tightening belt is provided in the clamping grooves 5. During construction, the special tightening belt is wound in the clamping grooves 5. The tightening force of the special tightening belt is controlled so that the tightening pressure can be evenly distributed on the surface of the sandpaper 2, and at the same time, the upper and lower semi-axial alignment and positioning of the semi-encircling hoop 1 are played.

[0058] In this embodiment, the handle 4 is fixedly connected to the outer circumferential surface of the semi-encircling hoop 1 by fasteners, and the handle 4 is arranged at the center of the outer circumferential surface of the semi-encircling hoop 1 to ensure uniform force during the grinding process.

[0059] In this embodiment, the sandpaper 2 is fixed on the inner side of the semi-ring clamp 2 by a pressure plate 3. Specifically, the sandpaper 2 is extended outward from the inner circular surface of the semi-ring clamp 1 to the center plane of the semi-ring clamp 1. The center plane is provided with a pressure plate 3, and the pressure plate 3 is fixedly connected to the semi-ring clamp 1 by a fastening screw 6, thereby pressing and fixing the sandpaper 2, which can ensure that the sandpaper 2 will not slip in the semi-ring clamp 1 due to the small friction coefficient during grinding.

[0060] The grinding tool provided in this embodiment completes the grinding of the rotor journal by entering the next process.

[0061] In process 1, 120-grit sandpaper 2 is installed on the upper and lower halves of the semi-encircling hoop 1 respectively, and the semi-encircling hoop 1 is set up in the area of ​​the shaft neck to be repaired. By cross-wrapping the tightening belt, the tightening force of the tightening belt is controlled. The tightening force at the large end of the shaft neck taper is slightly greater than that at the small end of the taper. The tightening force of the entire section is appropriate to be able to push the hoop to rotate with a little force from the operator.

[0062] In process 2, two people stand on both sides of the rotor and pull handle 4 back and forth at the same time to drive the clamp to rotate evenly to ensure stable force during the movement. Each pull requires the clamp to rotate at an angle of not less than 120 degrees, and the rotation frequency is about 30 times per minute. During the grinding process, pay attention to monitor the tightness of the clamp. If the clamp is found to be insufficiently tight, increase the tightness in time.

[0063] Step 3: Loosen the special tightening belt every 5 minutes and measure the journal size of the grinding area. If the measured size does not reach the required size, replace the new sandpaper, move the clamp back to the area to be polished, tighten the tightening belt, continue to pull the clamp back and forth to grind the journal, and repeat the above process until the measured size of the journal reaches the required size.

[0064] Step 4: Polishing: Change the sandpaper model to 150 mesh, repeat the above process, and move the clamp axially repeatedly until the surface finish of the shaft neck reaches Ra0.4.

[0065] After the shaft neck is repaired by grinding tooling, it is inspected: first remove the semi-encircling hoop 1, and measure the shaft neck size with an outside diameter micrometer to ensure that the diameter of the rotor shaft neck after repair meets the design requirement of a tolerance of 0.02mm.

[0066] Finally, install the bearing and use special measuring tools to measure the straightness of the shaft neck and the end face circular runout. Rotate the rotor in units of 30 degrees and use a transfer tool to measure the straightness of the rotor shaft neck in 360 degrees and 12 phases to ensure that the straightness and shaft neck runout meet the design requirement of 0.02mm.

[0067] In this embodiment, in order to facilitate measurement and ensure measurement accuracy, a special measuring tool is designed.

[0068] like Figure 4 As shown, the measuring tool mainly includes a transition plate 7, a guide rail 15, a support plate 8 and a support table 9, wherein the transition plate 7 is mounted on the center plane of the bearing seat 14 through the transition plate fastening screws 11, the guide rail 15 is fixed on the transition plate 7 through bolts 10, the support plate 8 is mounted on the guide rail 15 and can slide axially, and the support table 9 is adsorbed and mounted on the support plate 8.

[0069] Since the outer circle of the journal and the outer circle of the thrust plates on both sides (thrust plate A12 and thrust plate B13 in the figure) are processed with the same rotation reference, the axes of these three outer circles theoretically coincide and are all the axes of the rotor body. Therefore, the outer circle of the thrust plates on both sides (thrust plate A12 and thrust plate B13) is used as the reference to measure the straightness of the outer circle of the journal after grinding.

[0070] The measurement steps of the measuring tool are as follows.

[0071] (1) Figure 4 As shown, take any point A and point B on the outer circle of the thrust plates at both ends (thrust plate A12 and thrust plate B13), the distance between points A and B is L0, measure the outer circle diameters of these two points, record them as A0 and B0 respectively, calculate their difference and divide it by 2, record it as C0;

[0072] (2) Install the transition plate 7 on the middle plane of the bearing seat 14 using the transition plate fastening screws 11;

[0073] (3) The guide rail 15 is mounted on the transition plate 7, the gauge 9 is adsorbed on the surface of the support plate 8, and the distance between the gauge 9 and the rotor is controlled so that the gauge needle contacts the rotor surface;

[0074] (4) Slightly fix the guide rail 15 with the bolt 10 so that the meter reading does not change significantly when the support plate 8 is manually shaken;

[0075] (5) Push the support plate 8, make the gauge pointer contact the thrust inventory point A on one side, and clear the gauge reading;

[0076] (6) Push the support plate 8, make the gauge pointer contact the thrust inventory point B on the other side, and record the gauge reading as D0;

[0077] (7) At this time, the parallelism deviation value between the support plate 8 and the rotor axis can be calculated and recorded as E0, E0 = ARCTAN ((D0-C0) / L0); therefore, we make the meter reading D0 = C0, which means that the support plate 8 is parallel to the rotor axis at this time;

[0078] (8) Use the copper rod to knock the guide rail 15 to make it swing to a certain angle, continue to push the support plate 8 to observe the reading of point B with point A as the zero point, and repeat the above operation until the reading of the table D0 = C0;

[0079] (9) Tighten the bolts 10 symmetrically and observe the reading on the gauge. If the reading on the gauge changes before the bolts 10 are finally tightened, continue to push the support plate 8 to observe the reading on the gauge at point B with point A as the zero point, calibrate the parallelism of the support plate 8 again, and finally tighten the bolts 10.

[0080] (10) Continue to push the support plate 8 and observe the reading of point B with point A as the zero point to confirm that the parallelism of the support plate 8 is parallel to the rotor axis at this time;

[0081] (11) Place the pointer on the gauge in contact with the outer circle of the journal, take the leftmost outer circle as the zero point, push the support plate 8 to measure the gauge reading jump of the entire outer circle of the journal, and the maximum value is the straightness deviation value;

[0082] (12) By rotating the rotor, the straightness of the journal at different phases can be measured.

[0083] During the actual measurement process, the rotor was rotated in units of 30 degrees and the above-mentioned tool was used to measure the straightness of the rotor journal in 360 degrees and 12 phases. The measurement proved that the straightness and journal runout test results of the repaired rotor journal met the design requirement of journal straightness of 0.02mm.

Claims

1. A method for repairing the irregularity of the journal of a steam turbine rotor, characterized in that: The repair method comprises the following steps: S1. Measure the diameter and straightness of the rotor before repair and divide the rotor journal repair area; S2. Install the special grinding tool in the journal maintenance area to grind and polish the rotor journal. The grinding tool comprises two independent semi-circular hoops, sandpaper is pasted on the inner circumference of the two semi-circular hoops, and the two semi-circular hoops are fastened by a tightening belt wrapped around the outer circumference. A pull rope is connected to each semi-circular hoop, and the operator pulls the pull rope to rotate the semi-circular hoop to grind the rotor shaft neck; S3. After the rotor journal is repaired, remove the grinding tooling and measure the journal size with an outside micrometer to ensure that the rotor journal diameter meets the tolerance requirements; S4. Install the bearings and use measuring tools to measure the straightness and end face runout of the rotor journal at different phases to ensure that the straightness and end face runout dimensions meet the tolerance requirements. Wherein, the measuring tool comprises a guide rail assembly and a reference gauge arranged on one side of the rotor, the reference gauge is installed on the guide rail assembly, and the guide rail assembly is installed on the center plane of the bearing seat; Step S2 specifically includes: S21. Install 120-grit sandpaper in the two half-hoops respectively, set the half-hoops on the rotor journal, and tighten the two half-hoops to a suitable strength by tightening the straps; S22. Two operators pull the rope back and forth on both sides of the rotor to drive the semi-encircling hoop to rotate evenly, and grind the rotor shaft neck with sandpaper. During the grinding process, the tightening force of the semi-encircling hoop is monitored, and the tightening force is increased in time when the force is insufficient; S23, loosen the tightening belt every 5 minutes, measure the journal size of the grinding area, if the size does not reach the set size, replace the new sandpaper and continue grinding until the journal size reaches the set size; S24, replace the sandpaper model with 150 mesh, repeat the grinding process, and repeatedly move the semi-encircling hoop axially until the surface finish of the journal reaches Ra0.4; The measuring tool specifically comprises a transition plate, a guide rail, a support plate and a gauge, wherein the transition plate is arranged on one side of the rotor and fixedly connected to the center plane of the bearing seat, the guide rail is fixedly connected to the transition plate by bolts, the support plate is slidably matched with the guide rail, and the gauge is arranged on the support plate; In step S4, the straightness of the outer circle of the repaired journal is measured with the outer circle of the thrust plates on both sides of the rotor journal as the reference. During the measurement process, the support plate is first adjusted to be parallel to the rotor axis, and then the straightness is measured by a table; In step S4, the measurement method specifically includes the following steps: S41. Pick any point A and point B on the outer circle of the thrust plates on both sides. The distance between the two points AB is L0. Measure the outer diameters of the two points, which are recorded as A0 and B0 respectively. Calculate the difference and divide it by 2, which is recorded as C0. S42. Install the transition plate on the center surface of the bearing seat through connecting bolts; S43, setting the guide rail on the transition plate, adsorbing the table on the surface of the support plate, and controlling the distance between the table and the rotor so that the table needle contacts the rotor surface; S44. Slightly fix the guide rail with the fixing bolts so that the meter reading does not change significantly when the support plate is manually shaken; S45, push the support plate to move along the guide rail, make the gauge pointer contact the thrust inventory point A on one side, and clear the gauge reading; S46, push the pallet to move along the guide rail, make the gauge pointer contact the thrust inventory point B on the other side, and record the gauge reading as D0; S47, calculate the parallelism deviation value between the support plate and the rotor axis, record it as E0, E0=ARCTAN((D0-C0) / L0); S48, knock the guide rail with a copper rod to make it swing to a certain angle, continue to push the support plate to observe the reading of point B with point A as the 0 point, and repeat the above operation until the reading of the guide rail D0=C0; S49, tighten the guide rail connecting bolts symmetrically; S410, continue to push the support plate and observe the reading of point B with point A as the zero point to confirm that the parallelism of the support plate is parallel to the rotor axis at this time; S411, put the pointer of the gauge in contact with the outer circle of the journal, take the leftmost outer circle as the zero point, push the support plate to measure the gauge reading jump of the entire outer circle of the journal, and the maximum value is the straightness deviation value; S412. Rotate the rotor and measure the straightness of the journal at different phases.

2. The method for repairing the irregularity defect of the steam turbine rotor journal according to claim 1, characterized in that: In step S21, the tightening force of the tightening belt is controlled so that the tightening force at the large end of the journal taper is slightly greater than that at the small end of the taper. The tightening force of the entire section is appropriate for the operator to be able to push the clamp to rotate with a little force.

3. The method for repairing the irregularity defect of the turbine rotor journal according to claim 1, characterized in that: In step S22, each pulling requires that the half-encircling hoop has a rotation angle of not less than 120 degrees and a rotation frequency of 30 times per minute.

4. The method for repairing the irregularity defect of the steam turbine rotor journal according to claim 1, characterized in that: The semi-encircling hoop is made of nylon.

5. The method for repairing the irregularity defect of the steam turbine rotor journal according to claim 1, characterized in that: A plurality of clamping grooves are also arranged on each semi-encircling hoop. The clamping grooves are arranged along the outer circumferential surface contour of the semi-encircling hoop, and the binding belts are wound in the clamping grooves.

6. The method for repairing the irregularity defect of the steam turbine rotor journal according to claim 1, characterized in that: The length of the sandpaper satisfies: extending outward from the inner circular surface of the semi-encircling hoop to the mid-plane of the semi-encircling hoop, so that the sandpaper can be fixed by a pressing plate arranged at the mid-plane, and the pressing plate is connected to the mid-plane of the semi-encircling hoop by fastening screws.

7. The method for repairing the irregularity defect of the steam turbine rotor journal according to claim 1, characterized in that: In step S412, the rotor is rotated in units of 30 degrees to measure the straightness of the rotor journals of 12 phases over 360 degrees to ensure that the straightness of the rotor journals of the 12 phases meets the design dimensions.

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