A kind of milling device and method for repairing the defect of main steam isolation valve seat sealing surface

Abstract

This invention belongs to the technical field of in-situ machining and repair of the sealing surface of the main steam isolation valve seat in nuclear power plants, specifically relating to a milling machining device and method for repairing defects in the sealing surface of the main steam isolation valve seat. It includes a machining unit, a Z-axis unit, an X-axis unit, a Y-axis unit, a valve body circumferential angle adjustment unit, a sealing surface angle adjustment unit, a support unit, and a detection unit. The machining unit and detection unit are mounted on the Z-axis unit. The support unit serves as a mounting platform. The valve body circumferential angle adjustment unit, the sealing surface angle adjustment unit, and the Y-axis unit are fixed to the support unit via two slide rails. The X-axis unit is connected to the Y-axis unit, and the Z-axis unit is connected to the X-axis unit. The advantages are: the machining unit in this invention has circumferential and radial feed, allowing for the repair of the entire valve assembly sealing surface; the machining unit is small in size, allowing operation within the confined space inside the valve body.

Description

Technical Field

[0001] This invention belongs to the field of in-situ machining and repair technology of the sealing surface of the main steam isolation valve seat in nuclear power plants, specifically relating to a milling machining device and method for repairing defects in the sealing surface of the main steam isolation valve seat. Background Technology

[0002] The main steam isolation valve is the largest valve in a nuclear power plant. Installed on the main steam pipeline, it is susceptible to various defects on its seat sealing surface due to mechanical impact and corrosion during operation. When the hard weld overlay on the main steam isolation valve seat sealing surface cracks or is damaged locally by impact, internal leakage will occur, directly affecting the safe operation of the unit.

[0003] During manufacturing, the through holes on both sides of the bottom of the main steam isolation valve are not connected to the pipeline, allowing machining equipment to insert tools through these holes and machine the valve seat sealing surface. However, in power plant applications, the through holes on both sides of the bottom of the main steam isolation valve are welded to the pipeline, preventing machining equipment from entering the valve body through the side holes. Access is only possible through the top through hole. The valve body's internal space is limited, and the valve seat sealing surface requires high hardness and precision. This places high demands on the spatial structure and repair capabilities of the online machining and repair equipment, making equipment design challenging. Currently, there is no equipment capable of directly removing deep defects on the valve seat sealing surface or machining a smooth surface after welding and additive manufacturing. Summary of the Invention

[0004] The purpose of this invention is to provide a milling apparatus and method for repairing defects in the sealing surface of the main steam isolation valve seat, which can repair the sealing surface of the main steam isolation valve seat without disassembling the main steam isolation valve connecting pipe.

[0005] The technical solution of the present invention is as follows: A milling processing device for repairing defects in the sealing surface of a main steam isolation valve seat includes a processing unit, a Z-axis unit, an X-axis unit, a Y-axis unit, a valve body circumferential angle adjustment unit, a sealing surface angle adjustment unit, a support unit, and a detection unit. The processing unit and the detection unit are mounted on the Z-axis unit. The support unit serves as a mounting platform. The valve body circumferential angle adjustment unit, the sealing surface angle adjustment unit, and the Y-axis unit are fixed to the support unit by two slide rails. The X-axis unit is connected to the Y-axis unit, and the Z-axis unit is connected to the X-axis unit.

[0006] The machining unit includes a circumferential feed unit, a radial feed unit, and a power head unit. The circumferential feed unit drives the milling cutter head to feed in the circumferential direction. The circumferential feed unit includes a drive motor, a right-angle reducer, a drive gear, a slewing bearing, and a rotary platform. The drive motor drives the drive gear to rotate via the right-angle reducer. The drive gear meshes with the slewing bearing and drives it to rotate. A rotary platform is fixed on the slewing bearing. The radial feed unit drives the milling cutter head to feed in the radial direction. The radial feed unit includes a drive motor, a linear feed unit, and a sliding platform. The guide rail unit, drive motor, linear unit, and guide rail unit are fixed on the rotary platform of the circumferential feed unit. The sliding platform cooperates with the guide rail unit and can slide on it. The linear unit is connected to the sliding platform. The drive motor cooperates with the linear unit and drives the linear unit and the sliding platform to make linear motion on the guide rail unit. The power head unit is used for the power of milling the valve seat sealing surface. The power head unit includes a power motor, a right-angle tool holder, and a milling cutter head. The power motor is fixed on the sliding platform of the radial feed unit. The power motor drives the right-angle tool holder, and the milling cutter head is installed on the right-angle tool holder.

[0007] The Z-axis unit includes a Z-axis linear drive unit, a Z-axis guide rail unit, and a Z-axis sliding platform. The Z-axis guide rail unit and the Z-axis sliding platform cooperate with each other. The Z-axis linear drive unit drives the Z-axis sliding platform to perform linear motion on the Z-axis guide rail unit, and the Z-axis sliding platform is used to support the machining unit.

[0008] The Y-axis unit is used to drive the milling cutter head to feed in the depth direction. The Y-axis unit includes a Y-axis linear drive unit, a Y-axis guide rail unit, and a Y-axis sliding platform. The Y-axis guide rail unit is mounted on the support unit. The Y-axis guide rail unit cooperates with the Y-axis sliding platform. The Y-axis linear drive unit drives the Y-axis sliding platform to make linear motion on the Y-axis guide rail unit.

[0009] The X-axis unit includes an X-axis linear drive unit, an X-axis guide rail unit, and an X-axis sliding platform. The X-axis guide rail unit is mounted on the Y-axis sliding platform of the Y-axis unit. The X-axis guide rail unit cooperates with the X-axis sliding platform, and the X-axis linear drive unit drives the X-axis sliding platform to perform linear motion on the X-axis guide rail unit.

[0010] The support unit includes a support platform and a connecting block. The support platform has a ring structure, and the connecting block has a wedge-shaped structure and is connected to the support platform by screws.

[0011] The valve body circumferential angle adjustment unit is located on the support platform. The valve body circumferential angle adjustment unit includes a drive motor, a reducer, a drive gear, a slewing bearing, and a slewing platform. The outer ring of the slewing bearing is fixed to the support platform by screws, and the slewing platform is fixed to the inner ring of the slewing bearing. The outer ring of the slewing bearing has an external tooth structure. The drive motor and reducer drive the drive gear to push the slewing platform to rotate along the outer ring of the slewing bearing.

[0012] The sealing surface angle adjustment unit is located on the rotary platform of the valve body circumferential angle adjustment unit. The sealing surface angle adjustment unit includes a drive motor, a corner housing, a swing platform, an arc rack, a rack support seat, a drive gear, a rotating shaft seat, a rotating shaft, an arc block support seat, a Y-axis follower bearing, an arc support block, and an X-axis follower bearing. The power of the drive motor is transferred to the drive gears on both sides through the corner housing. The drive gears move on the arc rack, driving the swing platform to rotate around the rotating shaft on the rotating shaft seat, thereby adjusting the tilt angle of the swing platform.

[0013] The detection unit includes a laser scanner and a leveling distance measuring instrument, both of which are fixed on the sliding platform of the radial feed unit.

[0014] A milling method for repairing defects on the sealing surface of a main steam isolation valve seat includes the following steps: Step 1: Install the valve seat sealing surface milling and repair equipment onto the valve body flange surface; Step 2: The circumferential feed unit of the processing unit drives the detection unit to perform detection; Step 3: The valve body circumferential angle adjustment unit and the sealing surface angle adjustment unit are adjusted according to the detection results of the detection unit to keep the feed plane of the processing unit parallel to the valve seat sealing surface; Step 4: The X-axis unit and Z-axis unit are adjusted according to the detection results of the detection unit to make the rotation center of the machining unit coaxial with the center of the valve seat sealing surface; Step 5: After adjustment, the milling equipment will mill the defects. Step 6: After processing is completed, disassemble the valve seat sealing surface milling repair equipment.

[0015] The beneficial effects of this invention are as follows: The processing unit of this invention has circumferential and radial feed, enabling the repair of the entire valve assembly sealing surface; the processing unit is small in size, allowing operation within the confined space of the valve body; the feed rotation center of the processing unit can be adjusted in a plane using the Z-axis and X-axis units, ensuring that the feed rotation center is aligned with the center of the valve seat sealing surface; the feed plane of the processing unit can be adjusted in angle using the valve body circumferential angle adjustment unit and the sealing surface angle adjustment unit, ensuring that the feed rotation plane remains parallel to the valve seat sealing surface. The processing unit has an automatic adjustment function, reducing the need for personnel to operate within the confined space of the valve body, alleviating workload, improving adjustment efficiency, and reducing overhaul time. Attached Figure Description

[0016] Figure 1 A schematic diagram of a milling apparatus for repairing defects in the sealing surface of a main steam isolation valve provided by the present invention; Figure 2 A schematic diagram of a milling device for repairing defects in the sealing surface of a main steam isolation valve seat, provided by the present invention, and the valve body installation. Figure 3 A milling apparatus for repairing defects in the sealing surface of a main steam isolation valve seat, and a cross-sectional view of the valve body installation provided by the present invention; Figure 4 Schematic diagram of main steam isolation valve body and seat Figure 5 This is a first schematic diagram of the processing unit; Figure 6 This is a second schematic diagram of the processing unit; Figure 7 This is a schematic cross-sectional view of the processing unit; Figure 8 Schematic diagram of X-axis unit, Y-axis unit, and Z-axis unit; Figure 9 A schematic diagram of the valve body circumferential angle adjustment unit and support unit; Figure 10 This is a first schematic diagram of the sealing surface angle adjustment unit; Figure 11 This is a second schematic diagram of the sealing surface angle adjustment unit.

[0017] In the diagram: 100 Machining Unit, 110 Circumferential Feed Unit, 111 Drive Motor, 112 Right-Angle Reducer, 113 Drive Gear, 114 Slewing Bearing, 115 Rotary Platform, 120 Radial Feed Unit, 121 Drive Motor, 122 Linear Unit, 123 Sliding Platform, 124 Guide Rail Unit, 130 Power Head Unit, 131 Power Motor, 132 Right-Angle Tool Holder, 133 Milling Head, 200 Z-Axis Unit, 201 Z-Axis Linear Drive Unit, 202 Z-Axis Guide Rail Unit, 203 Z-Axis Sliding Platform, 300 Valve Body Circumferential Angle Adjustment Unit, 301 Drive Motor, 302 Reducer, 303 Drive Gear, 304 Slewing Bearing, 305 Rotary Platform, 400 Sealing Surface Angle Adjustment Unit, 401 Drive Motor, 402 Corner Housing, 403 Oscillating Platform, 404 Arc-shaped rack, 405 Rack support seat, 406 Drive gear, 407 Rotary shaft seat, 408 Rotary shaft, 409 Arc-shaped block support seat, 410 Y-axis follower bearing, 411 Arc-shaped support block, 412 X-axis follower bearing, 500 X-axis unit, 501 X-axis linear drive unit, 502 X-axis guide rail unit, 503 X-axis sliding platform, 600 Y-axis unit, 601 Y-axis linear drive unit, 602 Y-axis guide rail unit, 603 Y-axis sliding platform, 700 Support unit, 701 Support platform, 702 Connecting block, 800 Detection unit, 801 Leveling distance measuring instrument, 802 Laser scanner, 900 Main steam isolation valve, 910 Valve body, 911 Side through hole, 912 Top through hole, 913 Flange face, 920 Valve seat, 921 Valve seat sealing surface. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] This invention provides a milling apparatus and method for repairing defects on the sealing surface of a main steam isolation valve seat. It can remove defects on the valve seat sealing surface without disassembling the connecting pipes of the main steam isolation valve, machining it into the bevel required for welding repair, and then performing the machining repair after welding. The apparatus is easy to install and adjust, has high processing efficiency, reduces the radiation dose, operational risks, and labor intensity for operators, and significantly shortens the overhaul period.

[0020] like Figure 4As shown, the valve seat sealing surface 921 of the main steam isolation valve 900 may develop defects such as pitting, corrosion, and scratches during use. Defects of small depth can be removed directly by grinding the entire valve seat sealing surface. Defects of larger depth require multiple processes including defect removal, welding additive manufacturing, machining repair, and grinding. During maintenance, after the main steam isolation valve 900 is disassembled, the remaining components are the valve body 910 and valve seat 920. Because the lateral through-hole 911 at the bottom of the valve body 910 is welded to the pipeline, the machining equipment needs to enter the valve body 910 through the top through-hole 912 to remove defects from the valve seat sealing surface 921 and perform machining repair after welding additive manufacturing.

[0021] This invention discloses a milling machining device for repairing defects on the sealing surface of a main steam isolation valve seat. It is used for defect removal and post-additional machining repair, and includes: a machining unit 100, a Z-axis unit 200, an X-axis unit 500, a Y-axis unit 600, a valve body circumferential angle adjustment unit 300, a sealing surface angle adjustment unit 400, a support unit 700, and a detection unit 800. Figure 1 As shown, the processing unit 100 and the detection unit 800 are mounted on the Z-axis unit 200. The support unit 700 serves as the mounting platform. The valve body circumferential angle adjustment unit 300 and the sealing surface angle adjustment unit 400 are also present. The Y-axis unit 600 is fixed to the support unit 700 via two slide rails. The X-axis unit 500 is connected to the Y-axis unit 600, and the Z-axis unit 200 is connected to the X-axis unit 500.

[0022] like Figure 5-7 As shown, the processing unit 100 includes three parts: a circumferential feed unit 110, a radial feed unit 120, and a power head unit 130.

[0023] The circumferential feed unit 110 is used to drive the milling cutter head 133 to feed in the circumferential direction. The circumferential feed unit 110 includes a drive motor 111, a right-angle reducer 112, a drive gear 113, a slewing bearing 114, and a slewing platform 115. The drive motor 111 drives the drive gear 113 to rotate through the right-angle reducer 112. The drive gear 113 meshes with the slewing bearing 114 and drives it to rotate. The slewing bearing 114 is fixed on the slewing platform 115.

[0024] The radial feed unit 120 is used to drive the milling cutter head 133 to feed in the radial direction. The radial feed unit 120 includes: a drive motor 121, a linear unit 122, a sliding platform 123, and a guide rail unit 124. The drive motor 121, the linear unit 122, and the guide rail unit 124 are fixed on the rotary platform 115 of the circumferential feed unit 110. The sliding platform 123 cooperates with the guide rail unit 124 and can slide on it. The linear unit 122 is connected to the sliding platform 123. The drive motor 121 cooperates with the linear unit 122 and drives the linear unit 122 and the sliding platform 123 to make linear motion on the guide rail unit 124.

[0025] The power head unit 130 is used for the power of milling the valve seat sealing surface. The power head unit 130 includes a power motor 131, a right-angle tool holder 132 and a milling cutter head 133. The power motor 131 is fixed on the sliding platform 123 of the radial feed unit 120. The power motor 131 drives the right-angle tool holder 132, and the milling cutter head 133 is mounted on the right-angle tool holder 132.

[0026] like Figure 8 As shown, the Z-axis unit 200 and the X-axis unit 500 are used to adjust the relative position of the rotation center of the machining unit 100 and the center of the valve seat sealing surface 921.

[0027] Z-axis unit 200 includes Z-axis linear drive unit 201, Z-axis guide rail unit 202, and Z-axis sliding platform 203. Z-axis guide rail unit 202 and Z-axis sliding platform 203 cooperate, with Z-axis linear drive unit 201 driving Z-axis sliding platform 203 to perform linear motion on Z-axis guide rail unit 202. Z-axis sliding platform 203 supports machining unit 100. During milling operations, machining unit 100 is subjected to the impact of milling forces and feed forces; therefore, Z-axis sliding platform 203 should possess sufficient rigidity to reduce deformation and ensure milling accuracy.

[0028] like Figure 8 As shown, the Y-axis unit 600 is used to drive the milling cutter head 133 to feed in the depth direction. The Y-axis unit 600 includes a Y-axis linear drive unit 601, a Y-axis guide rail unit 602, and a Y-axis sliding platform 603. The Y-axis guide rail unit 602 is mounted on the support unit 700. The Y-axis guide rail unit 602 cooperates with the Y-axis sliding platform 603. The Y-axis linear drive unit 601 drives the Y-axis sliding platform 603 to perform linear motion on the Y-axis guide rail unit 602.

[0029] like Figure 8As shown, the X-axis unit 500 includes an X-axis linear drive unit 501, an X-axis guide rail unit 502, and an X-axis sliding platform 503. The X-axis guide rail unit 502 is mounted on the Y-axis sliding platform 603 of the Y-axis unit 600. The X-axis guide rail unit 502 cooperates with the X-axis sliding platform 503. The X-axis linear drive unit 501 drives the X-axis sliding platform 503 to perform linear motion on the X-axis guide rail unit 502.

[0030] The valve body circumferential angle adjustment unit 300 and the sealing surface angle adjustment unit 400 are used to adjust the feed path of the machining unit to keep it parallel to the valve seat sealing surface 921.

[0031] like Figure 9 As shown, the support unit 700 is used to fix the repair equipment to the flange face 913 on the top of the valve body 910. The support unit 700 includes a support platform 701 and a connecting block 702. The support platform 701 has an annular structure, and the connecting block 702 has a wedge-shaped structure. It is connected to the support platform 701 by screws. When the screws are tightened, the wedge-shaped structure at the bottom of the connecting block 702 engages with the wedge-shaped structure of the valve body 910 to lock it in place.

[0032] like Figure 9 As shown, the valve body circumferential angle adjustment unit 300 is located on the support platform 701. The valve body circumferential angle adjustment unit 300 includes a drive motor 301, a reducer 302, a drive gear 303, a slewing bearing 304, and a slewing platform 305. The outer ring of the slewing bearing 304 is fixed to the support platform 701 with screws, and the slewing platform 305 is fixed to the inner ring of the slewing bearing 304. The outer ring of the slewing bearing 304 has an external gear structure. The drive motor 301 and the reducer 302 drive the drive gear 303 to push the slewing platform 305 to rotate along the outer ring of the slewing bearing 304.

[0033] like Figure 10 As shown, the sealing surface angle adjustment unit 400 is located on the rotary platform 305 of the valve body circumferential angle adjustment unit. The sealing surface angle adjustment unit 400 includes a drive motor 401, an angle housing 402, a swing platform 403, an arc-shaped rack 404, a rack support 405, a drive gear 406, a rotating shaft seat 407, a rotating shaft 408, an arc-shaped block support 409, a Y-axis follower bearing 410, an arc-shaped support block 411, and an X-axis follower bearing 412.

[0034] The power of the drive motor 401 is transferred to the drive gears 406 on both sides via the corner housing 402. The drive gears 406 move on the arc rack 404, driving the swing platform 403 to rotate around the rotating shaft 408 on the rotating shaft seat 407, thereby adjusting the tilt angle of the swing platform 403.

[0035] like Figure 6As shown, the detection unit 800 includes a laser scanner 802 and a leveling rangefinder 801. Both the laser scanner 802 and the leveling rangefinder 801 are fixed on the sliding platform 123 of the radial feed unit 120.

[0036] The detection unit 800 has two main functions: one is to calibrate the position of the machining unit 100, including ensuring that the rotation center of the machining unit 100 is aligned with the center of the valve seat sealing surface 921, and that the feed plane of the machining unit 100 is parallel to the valve seat sealing surface 921; the other is to use a laser scanner 802 to scan the repair area and check whether the forming quality of the laser welding and milling operations meets the technical requirements. The detection unit 800 and the machining unit 100 share a rotary platform 115, which allows for inspection of the valve seat sealing surface 921 within a 360° range. The leveling distance measuring instrument 801 is a laser distance sensor that can detect the distance from the rotation plane of the machining unit 100 to the valve seat sealing surface 921. The rotary platform 115 drives the leveling distance measuring instrument 801 to measure distances at different rotation angles. The measured distance values ​​are fed back to the controller. Based on the different measured distance values, the adjustment angle can be calculated, and then the valve body circumferential angle adjustment unit 300 and the sealing surface angle adjustment unit 400 can be adjusted so that the feed plane of the processing unit 100 is parallel to the valve seat sealing surface 921.

[0037] In the specific implementation of the milling apparatus of the present invention, the processing unit 100 includes a power head unit 130 for specific milling processing of the surface to be repaired, and the planar motion feed for milling processing is provided by the circumferential feed unit 110 and the radial feed unit 120. For example... Figure 7 As shown, the machining unit 100 is fixed on the Z-axis unit 200, and the Z-axis unit 200 can drive the machining unit 100 to adjust its position in the Z-axis direction.

[0038] The detection unit 800 is fixed to the sliding platform 123 of the processing unit 100 by bolts.

[0039] The Z-axis unit 200 is fixed to the X-axis sliding platform 503 of the X-axis unit 500 by bolts, and the X-axis unit 500 drives the machining unit 100 to adjust its position in the X-axis direction.

[0040] The X-axis unit 500 is fixed on the Y-axis sliding platform 603 of the X-axis unit 500 by bolts. The Y-axis unit 600 drives the machining unit 100 to move in the Y-axis direction, thereby providing the feed motion in the depth direction for milling.

[0041] The Y-axis unit 600 is fixed on the swing platform 403 of the sealing surface angle adjustment unit 400 and connected by screws. The sealing surface angle adjustment unit 400 is used to adjust the angle between the machining unit 100 and the valve seat sealing surface 921.

[0042] The sealing surface angle adjustment unit 400 is fixed on the rotary platform 305 of the valve body circumferential angle adjustment unit 300 and connected by bolts. The valve body circumferential angle adjustment unit 300 is used to adjust the angle between the machining unit 100 and the valve seat sealing surface 921 in the circumferential direction of the valve body flange surface 913.

[0043] The valve body circumferential angle adjustment unit 300 is fixed on the support platform 701 of the support unit 700 and connected by bolts.

[0044] The support unit 700 is fixed on the flange face 913 of the valve body 910 and is fixed by the connecting block 702, which mates with the wedge-shaped surface of the flange face 913.

[0045] The main steam isolation valve seat sealing surface milling repair equipment proposed in this invention has two main uses: first, it is used to remove the original defective surface oxide layer and process the area to be repaired into a shape suitable for weld additive repair; second, it is used to process the welded material after weld additive repair to make the repaired area flat and consistent with the normal area. The implementation methods for the two uses are basically the same, only the milling cutter head is different. Therefore, we will only introduce the defect removal process.

[0046] A milling method for repairing defects on the sealing surface of a main steam isolation valve seat includes the following steps: Step 1: Install the valve seat sealing surface milling and repair equipment onto the valve body flange surface; Step 2: The circumferential feed unit of the processing unit drives the detection unit to perform detection; Step 3: The valve body circumferential angle adjustment unit and the sealing surface angle adjustment unit are adjusted according to the detection results of the detection unit to keep the feed plane of the processing unit parallel to the valve seat sealing surface; Step 4: The X-axis unit and Z-axis unit are adjusted according to the detection results of the detection unit to make the rotation center of the machining unit coaxial with the center of the valve seat sealing surface; Step 5: After adjustment, the milling equipment will mill the defects. Step 6: After processing is completed, disassemble the valve seat sealing surface milling repair equipment.

Claims

1. A milling apparatus for repairing defects in the sealing surface of a main steam isolation valve seat, characterized in that: It includes a machining unit, a Z-axis unit, an X-axis unit, a Y-axis unit, a valve body circumferential angle adjustment unit, a sealing surface angle adjustment unit, a support unit, and a detection unit. The machining unit and the detection unit are mounted on the Z-axis unit. The support unit serves as a mounting platform. The valve body circumferential angle adjustment unit, the sealing surface angle adjustment unit, and the Y-axis unit are fixed to the support unit via two slide rails. The X-axis unit is connected to the Y-axis unit, and the Z-axis unit is connected to the X-axis unit. The machining unit includes a circumferential feed unit, a radial feed unit, and a power head unit. The circumferential feed unit drives the milling cutter head to feed in the circumferential direction. The circumferential feed unit includes a drive motor, a right-angle reducer, a drive gear, a slewing bearing, and a rotary platform. The drive motor drives the drive gear to rotate via the right-angle reducer. The drive gear meshes with the slewing bearing and drives it to rotate. A rotary platform is fixed on the slewing bearing. The radial feed unit drives the milling cutter head to feed in the radial direction. The radial feed unit includes a drive motor, a linear feed unit, and a sliding platform. The guide rail unit, drive motor, linear unit, and guide rail unit are fixed on the rotary platform of the circumferential feed unit. The sliding platform cooperates with the guide rail unit and can slide on it. The linear unit is connected to the sliding platform. The drive motor cooperates with the linear unit and drives the linear unit and the sliding platform to make linear motion on the guide rail unit. The power head unit is used for the power of milling the valve seat sealing surface. The power head unit includes a power motor, a right-angle tool holder, and a milling cutter head. The power motor is fixed on the sliding platform of the radial feed unit. The power motor drives the right-angle tool holder, and the milling cutter head is installed on the right-angle tool holder. The support unit includes a support platform and a connecting block. The support platform has a ring structure, and the connecting block has a wedge-shaped structure and is connected to the support platform by screws. The valve body circumferential angle adjustment unit is located on the support platform. The valve body circumferential angle adjustment unit includes a drive motor, a reducer, a drive gear, a slewing bearing, and a slewing platform. The outer ring of the slewing bearing is fixed to the support platform by screws, and the slewing platform is fixed to the inner ring of the slewing bearing. The outer ring of the slewing bearing has an external tooth structure. The drive motor and the reducer drive the drive gear to push the slewing platform to rotate along the outer ring of the slewing bearing. The sealing surface angle adjustment unit is located on the rotary platform of the valve body circumferential angle adjustment unit. The sealing surface angle adjustment unit includes a drive motor, a corner housing, a swing platform, an arc rack, a rack support seat, a drive gear, a rotating shaft seat, a rotating shaft, an arc block support seat, a Y-axis follower bearing, an arc support block, and an X-axis follower bearing. The power of the drive motor is transferred to the drive gears on both sides through the corner housing. The drive gears move on the arc rack, driving the swing platform to rotate around the rotating shaft on the rotating shaft seat, thereby adjusting the tilt angle of the swing platform.

2. The milling apparatus for repairing defects in the sealing surface of a main steam isolation valve seat as described in claim 1, characterized in that: The Z-axis unit includes a Z-axis linear drive unit, a Z-axis guide rail unit, and a Z-axis sliding platform. The Z-axis guide rail unit and the Z-axis sliding platform cooperate with each other. The Z-axis linear drive unit drives the Z-axis sliding platform to perform linear motion on the Z-axis guide rail unit, and the Z-axis sliding platform is used to support the machining unit.

3. The milling apparatus for repairing defects in the sealing surface of a main steam isolation valve seat as described in claim 1, characterized in that: The Y-axis unit is used to drive the milling cutter head to feed in the depth direction. The Y-axis unit includes a Y-axis linear drive unit, a Y-axis guide rail unit, and a Y-axis sliding platform. The Y-axis guide rail unit is mounted on the support unit. The Y-axis guide rail unit cooperates with the Y-axis sliding platform. The Y-axis linear drive unit drives the Y-axis sliding platform to make linear motion on the Y-axis guide rail unit.

4. The milling apparatus for repairing defects in the sealing surface of a main steam isolation valve seat as described in claim 1, characterized in that: The X-axis unit includes an X-axis linear drive unit, an X-axis guide rail unit, and an X-axis sliding platform. The X-axis guide rail unit is mounted on the Y-axis sliding platform of the Y-axis unit. The X-axis guide rail unit cooperates with the X-axis sliding platform, and the X-axis linear drive unit drives the X-axis sliding platform to perform linear motion on the X-axis guide rail unit.

5. The milling apparatus for repairing defects in the sealing surface of a main steam isolation valve seat as described in claim 1, characterized in that: The detection unit includes a laser scanner and a leveling distance measuring instrument, both of which are fixed on the sliding platform of the radial feed unit.

6. A milling method for repairing defects on the sealing surface of the main steam isolation valve seat using the processing apparatus described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Install the valve seat sealing surface milling and repair equipment onto the valve body flange surface; Step 2: The circumferential feed unit of the processing unit drives the detection unit to perform detection; Step 3: The valve body circumferential angle adjustment unit and the sealing surface angle adjustment unit are adjusted according to the detection results of the detection unit to keep the feed plane of the processing unit parallel to the valve seat sealing surface; Step 4: The X-axis unit and Z-axis unit are adjusted according to the detection results of the detection unit to make the rotation center of the machining unit coaxial with the center of the valve seat sealing surface; Step 5: After adjustment, the milling equipment will mill the defects. Step 6: After processing is completed, disassemble the valve seat sealing surface milling repair equipment.

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