A method for grinding bearings in a dynamic balancing test of a steam turbine generator rotor
By using methods such as measurement, pigment application, and electric grinding, the compatibility problem of test bearings in different dynamic balancing test stations was solved, thereby achieving the versatility of test bearings and improving production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN ELECTRIC MASCH CO LTD
- Filing Date
- 2024-03-25
- Publication Date
- 2026-05-26
Smart Images
Figure CN118219067B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of dynamic balancing test bearings for steam turbine generator rotors, and more particularly to a grinding method for dynamic balancing test bearings for steam turbine generator rotors. Background Technology
[0002] As a key component in the generator set for converting mechanical energy into electrical energy, the turbine generator rotor maintains high-speed rotation during unit operation to provide a magnetic field. Therefore, it not only has high requirements in terms of material properties, machining accuracy, and assembly quality, but also requires good dynamic balance. The main equipment required for the dynamic balancing test of the turbine generator rotor includes a drive motor, universal joint, test bearing housing, test bearing, test brush holder, and vibration monitoring device. To ensure the stability of the rotor during the dynamic balancing test, the test bearing has a spherical structure on its outer circumference. The lower left and lower right parts of the lower half bearing contact the bearing housing and are its main support parts. Correspondingly, the inner circumference support position of the bearing housing also adopts a spherical structure. The diameters of the two spheres are matched. After machining, the contact spheres are ground relative to each other to ensure good spherical contact. After grinding, the test bearing can slide freely within a small range along the tangential direction of the bearing sphere, compensating for installation deviations of the rotor and related components. Simultaneously, the lower left or lower right part of the lower half bearing is also the location of the bearing oil inlet. The ground spheres maintain a good seal in the oil passage, preventing oil leakage. Summary of the Invention
[0003] This invention provides a grinding method for improving the versatility of bearings used in dynamic balancing tests of steam turbine generator rotors. This is achieved through the following process steps:
[0004] S1. Measure the clearance between the test bearing and bearing housing A after assembly: After the test bearing and bearing housing A are machined separately, the nominal diameter of the outer spherical surface of the test bearing is the same as the nominal diameter of the inner spherical surface of the bearing housing A; install the test bearing into bearing housing A, and measure the clearance between the lower left and lower right support blocks of the test bearing and the inner spherical surface of bearing housing A; the clearance value is not more than 0.03mm, which is considered qualified; if it is not qualified, it needs to be re-machined.
[0005] S2. Apply pigment to the spherical surface: Remove the test bearing from bearing housing A, apply white pigment to the surface of the outer spherical support block of the test bearing, with a pigment thickness not exceeding 0.007mm; apply colored pigment to the inner spherical surface of bearing housing A corresponding to the lower left and lower right support blocks of the test bearing, with a pigment thickness not exceeding 0.007mm.
[0006] S3. Check the spherical contact: Place the test bearing into bearing housing A and hold for at least 2 minutes; lift the test bearing; check the area of colored pigment adhering to the white pigment within a 150mm×150mm radius of the center of the lower left and lower right support blocks of the test bearing. If the proportion of the adhering area (i.e., the contact rate) exceeds 75%, and the contact rate within 25mm outside the oil hole on the surface of the lower right support block with the oil inlet reaches 100%, it is considered qualified. If it is not qualified, grinding treatment is required.
[0007] S4. Grinding the test bearing: If the contact rate between the test bearing and bearing housing A is not up to standard, use an electric grinding tool to grind the test bearing and remove its surface protrusions; clean the pigment from the surface of the test bearing and bearing housing A, repeat S2 and S3, and check the contact rate; if the contact rate is not up to standard, repeat the above process to continue grinding and checking until the contact rate is up to standard.
[0008] S5. Measure the clearance between the test bearing and bearing housing B after assembly: After the bearing housing B is machined, the nominal diameter of the inner spherical surface of the bearing housing B is the same as the nominal diameter of the outer spherical surface of the test bearing. Install the test bearing into the bearing housing B and measure the clearance between the lower left and lower right support blocks of the test bearing and the inner spherical surface of the bearing housing B. The clearance value is considered qualified if it does not exceed 0.03mm. If it is not qualified, it needs to be re-machined.
[0009] S6. Apply pigment to the spherical surface: Remove the test bearing from bearing housing B, apply white pigment to the surface of the lower left and lower right support blocks on the outer spherical surface of the test bearing, with a pigment thickness not exceeding 0.007mm; apply colored pigment to the inner spherical surface of bearing housing B at the positions corresponding to the lower left and lower right support blocks of the test bearing, with a pigment thickness not exceeding 0.007mm.
[0010] S7. Check the spherical contact: Place the test bearing into bearing housing B and hold for at least 2 minutes; lift the test bearing; check the area of colored pigment on the white pigment of the lower left and lower right support blocks of the test bearing, excluding the central 150mm×150mm area. If the proportion of the colored area (contact rate) exceeds 75%, and the contact rate within the central 175mm×175mm area of the lower right support block with oil inlet reaches 100%, it is considered qualified. If it is not qualified, grinding treatment is required.
[0011] S8. Grinding the test bearing: If the contact rate between the test bearing and bearing housing B is not up to standard, use an electric grinding tool to grind the test bearing and remove any protruding points on its surface; grinding is not allowed within the center 150mm×150mm area of the lower left and lower right support blocks of the test bearing; clean the pigment off the surface of the test bearing and bearing housing B, repeat S6 and S7, and check the contact rate. If the contact rate is not up to standard, repeat the above process to continue grinding and checking until the contact rate is up to standard.
[0012] In the above-mentioned test bearing grinding method, when measuring the gap between the lower left and lower right support blocks of the test bearing and the inner spherical surface of the bearing housing in steps S1 and S5, feeler gauges should be used to measure all areas around the lower left and lower right support blocks.
[0013] In the above-mentioned bearing grinding method for dynamic balancing test of turbine generator rotor, the pigment applied to the lower left and lower right support blocks and the inner spherical surface of the bearing housing in steps S2 and S6 should be uniform and consistent, and the thickness should be measured using a thickness gauge after application.
[0014] In the above-mentioned method for grinding bearings for dynamic balancing test of turbine generator rotor, during operations S3 and S7, the process of placing the test bearing into and lifting it out of the bearing housing must be completed in one go. The test bearing must not be allowed to move relative to the bearing housing, otherwise it will affect the contact rate test results. If the test bearing moves relative to the bearing housing, the test bearing must be lifted out, the paint on the surface of the test bearing and the bearing housing must be cleaned, and the paint must be reapplied before performing S3 and S7.
[0015] In the above-mentioned turbine generator rotor dynamic balancing test bearing grinding method, in S8, the support position range of the inner spherical surface of bearing B is relatively large. If the contact rate of the outer spherical surface of the test bearing is always unqualified, and there are protruding points within a range of 150mm×150mm in the center area of the lower left and lower right support blocks of the test bearing corresponding to the inner spherical surface of bearing B, it is allowed to grind the protruding points within this range of the inner spherical surface of bearing B. Otherwise, it is not allowed to grind any position of bearing A and bearing B (7).
[0016] The test bearing was ground using a dynamic balancing test bearing grinding method for the turbine generator rotor, which resulted in good contact between the central area (150mm × 150mm) of the lower left and lower right support blocks and the inner spherical surface of bearing housing A; and good contact between the area outside the central area (150mm × 150mm) of the lower left and lower right support blocks and the inner spherical surface of bearing housing B.
[0017] The beneficial effects of this invention are:
[0018] This invention enables the matching and applicability of test bearings with bearing housings of different rotor dynamic balancing test stations, solving the problem of using the same set of test bearings for dynamic balancing tests on the same model of steam turbine generator rotor in two different dynamic balancing test stations. This improves the versatility of test bearings, reduces the manufacturing cost of tooling, and also shortens the production cycle of steam turbine generator rotors. Attached Figure Description
[0019] Figure 1This is a schematic diagram of the test bearing.
[0020] Figure 2 This is a schematic diagram of bearing housing A.
[0021] Figure 3 This is a schematic diagram of bearing housing B.
[0022] Figure 4 This is a schematic diagram of the assembly of the test bearing and bearing housing A.
[0023] Figure 5 The purpose of this experiment is to grind the outer spherical surface of the bearing.
[0024] Figure 6 This is a schematic diagram of the assembly of the test bearing and bearing housing B.
[0025] Explanation of markings in the diagram:
[0026] 1-Test bearing; 2-Lower left support block of test bearing; 3-Lower right support block of test bearing;
[0027] 4 - Outer spherical surface of the test bearing; 5 - Bearing housing A; 6 - Inner spherical surface of bearing housing A; 7 - Bearing housing B; 8 - Inner spherical surface of bearing housing B; 9 - Contact position between the test bearing and bearing housing A;
[0028] 10 - The contact position between the test bearing and bearing housing B. Detailed Implementation
[0029] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] The grinding method for improving the versatility of dynamic balance test bearings for steam turbine generator rotors, as disclosed in this invention, is achieved through the following process steps:
[0031] S1. Measure the clearance between the test bearing and bearing housing A after assembly: (e.g.) Figure 1 , Figure 2 As shown, after the test bearing 1 and bearing housing A 4 are machined and cleaned, the nominal diameter of the outer spherical surface 4 of the test bearing 1 is the same as the nominal diameter of the inner spherical surface 6 of the bearing housing A 5; as Figure 4As shown, place the inner spherical surface 6 of bearing housing 5 facing upwards, adjust the mating planes on both sides to be horizontal, use a crane to lift the test bearing 1, and install the test bearing 1 vertically downwards into bearing housing 5, so that the outer spherical surface 4 of the test bearing 1 contacts the inner spherical surface 6 of bearing housing 5, the test bearing 1 is located at the center of bearing housing 5, and the mating surface of the test bearing 1 is kept horizontal. Use a feeler gauge to measure the gap between the outer spherical surface 4 of the lower left support block 2 and the lower right support block 3 of the test bearing 1 and the inner spherical surface 6 of bearing housing 5. If this gap value does not exceed 0.03mm, it is qualified. If it is not qualified, the outer spherical surface 4 of the test bearing 1 and the inner spherical surface 6 of bearing housing 5 need to be re-machined.
[0032] S2. Applying pigment to the spherical surface: Vertically suspend the test bearing 1 and remove it from the bearing housing 5. Apply white pigment evenly to the outer spherical surface 4 of the lower left support block 2 and the lower right support block 3 of the test bearing 1. The pigment thickness should not exceed 0.007mm. After application, use a thickness gauge to check the pigment thickness. If it is not up to standard, it needs to be cleaned and reapplied. Apply colored pigment to the inner spherical surface 6 of the bearing housing 5, corresponding to the positions of the lower left support block 2 and the lower right support block 3 of the test bearing 1. The pigment thickness should not exceed 0.007mm. After application, use a thickness gauge to check the pigment thickness. If it is not up to standard, it needs to be cleaned and reapplied.
[0033] S3. Check the spherical contact: Use a crane to vertically install the test bearing 1 into bearing housing A 5, ensuring the outer spherical surface 4 of the test bearing 1 contacts the inner spherical surface 6 of bearing housing A 5, the test bearing 1 is positioned at the center of bearing housing A 5, and the mating surfaces of the test bearing 1 are horizontal, maintaining this position for at least 2 minutes; then vertically lift the test bearing 1 upwards to separate it from bearing housing A 5; if... Figure 5 As shown, examine the area of colored pigment adhering to the white pigment within a 150mm x 150mm radius of the central area 9 of the outer spherical surface 4 of the lower left support block 2 and the lower right support block 3 of the test bearing 1. When the proportion of the adhering area, i.e., the contact rate, exceeds 75%, and the contact rate within 25mm outside the oil hole on the surface of the support block with the oil inlet reaches 100%, it is considered qualified. If the contact rate is not qualified, the test bearing needs to be ground.
[0034] S4. Grinding the test bearing: If the spherical contact rate between the test bearing 1 and bearing housing 5 is not up to standard, the test bearing 1 needs to be ground with an electric grinding tool to remove the protruding points on its outer spherical surface 4; clean the pigment from the surface of the test bearing 1 and bearing housing 5, repeat S2 and S3, and check the spherical contact rate again; if the contact rate is not up to standard, repeat the above process to continue grinding and checking until the contact rate is up to standard.
[0035] S5. Measure the clearance between the test bearing and bearing housing B after assembly: (e.g.) Figure 3As shown, after the B bearing housing 7 is machined, the nominal diameter of the inner spherical surface 8 of the B bearing housing 7 is the same as the nominal diameter of the outer spherical surface 4 of the test bearing 1; as Figure 6 As shown, place the inner spherical surface 8 of bearing housing 7 facing upwards, adjust the mating planes on both sides to be horizontal, use a crane to lift the test bearing 1, and install the test bearing 1 vertically downwards into bearing housing 7, so that the outer spherical surface 4 of the test bearing 1 contacts the inner spherical surface 8 of bearing housing 7, the test bearing 1 is located at the center of bearing housing 7, and the mating surface of the test bearing is kept horizontal. Use a feeler gauge to measure the gap between the outer spherical surface 4 of the lower left support block 2 and the lower right support block 3 of the test bearing 1 and the inner spherical surface 8 of bearing housing 7. If this gap value does not exceed 0.03mm, it is qualified. If it is not qualified, the outer spherical surface 4 of the test bearing 1 and the inner spherical surface 8 of bearing housing 7 need to be re-machined.
[0036] S6. Applying pigment to the spherical surface: Vertically suspend the test bearing 1 and remove it from the bearing housing 7. Apply white pigment evenly to the outer spherical surface 4 of the lower left support block 2 and the lower right support block 3 of the test bearing 1. The pigment thickness should not exceed 0.007mm. After application, use a thickness gauge to check the pigment thickness. If it is not up to standard, it needs to be cleaned and reapplied. Apply colored pigment to the inner spherical surface 8 of the bearing housing 7, corresponding to the positions of the lower left support block 2 and the lower right support block 3 of the test bearing 1. The pigment thickness should not exceed 0.007mm. After application, use a thickness gauge to check the pigment thickness. If it is not up to standard, it needs to be cleaned and reapplied.
[0037] S7. Check the spherical contact: Use a crane to vertically install the test bearing 1 into the bearing housing 7 (B), ensuring that the outer spherical surface 4 of the test bearing 2 contacts the inner spherical surface 8 of the bearing housing 7 (B), the test bearing 1 is located at the center of the bearing housing 7 (B), and the mating surface of the test bearing 1 is horizontal. Maintain this position for at least 2 minutes. Then, vertically lift the test bearing 1 upwards to separate it from the bearing housing 7 (B). Figure 5 As shown, examine the area of colored pigment adhering to the white pigment on the outer spherical surface 4 of the lower left support block 2 and the lower right support block 3 of the test bearing 1, excluding the central area of 150mm×150mm. If the proportion of the adhering area, i.e. the contact rate, exceeds 75%, and the contact rate within the central area of the lower right support block 3 with the oil inlet hole reaches 100%, it is considered qualified. If the contact rate is not qualified, the test bearing needs to be ground.
[0038] S8. Grinding the test bearing: If the spherical contact rate between the test bearing 1 and bearing housing 7 is not up to standard, the test bearing 1 must be ground using an electric grinding tool to remove the protruding points on its outer spherical surface 4; grinding is not allowed within the 150mm×150mm area 9 of the center of the lower left support block 2 and the lower right support block 3 of the test bearing 1; clean the pigment from the surface of the test bearing 1 and bearing housing 7, repeat S6 and S7, and check the spherical contact rate again; if the contact rate is not up to standard, repeat the above process to continue grinding and checking until the contact rate is up to standard.
[0039] In this embodiment, a grinding process method to improve the versatility of the test bearing was formulated according to the procedure. Based on the spherical surface condition inside different bearing housings, the grinding area and method of the test bearing were determined, so as to realize the versatility of the test bearing on two bearing housings.
[0040] Specific implementation method two: such as Figure 4 As shown, this embodiment further defines S1 and S5 as described in Specific Embodiment 1. In this embodiment, when measuring the gap between the outer spherical surface 4 of the test bearing 1 and the inner spherical surface 6 of the bearing housing 5 and the inner spherical surface 8 of the bearing 7, a feeler gauge is required to measure all areas around the lower left support block 2 and the lower right support block 3.
[0041] In this embodiment, the tools and methods for measuring the clearance between the outer spherical surface of the test bearing and the inner spherical surface of the bearing housing are determined.
[0042] Specific implementation method three: such as Figure 2 , Figure 3 , Figure 5 As shown, this embodiment further defines S2 and S6 as described in Specific Embodiment 1. In this embodiment, in S2 and S6, the pigment applied to the outer spherical surface 4 of the test bearing housing 1, the inner spherical surface 6 of the A bearing housing 5, and the inner spherical surface 8 of the B bearing 7 should be uniform and consistent. After application, the thickness should be measured using a thickness gauge.
[0043] In this embodiment, the inspection method and tools for applying pigment to the outer spherical surface of the test bearing and the inner spherical surface of the bearing housing were determined.
[0044] Specific implementation method four: such as Figure 4 , Figure 6 As shown, this embodiment further defines S3 and S7 as described in Specific Embodiment 1. In this embodiment, the process of placing the test bearing 1 into and lifting out bearing housing A 5 and bearing housing B 7 in S3 and S7 must be completed in one go. The test bearing 1 must not move relative to each other within bearing housing A 5 and bearing housing B 7, otherwise it will affect the contact rate test results. If the test bearing 1 moves relative to each other within bearing housing A 5 and bearing housing B 7, the test bearing 1 must be lifted out, the applied paint must be cleaned off, and the paint must be reapplied before proceeding with S3 and S7.
[0045] In this embodiment, the process method for placing the test bearing into and removing it from the bearing housing was determined.
[0046] Specific implementation method five: such as Figure 3 , Figure 5 As shown, this embodiment further defines S8 as described in Specific Embodiment 1. In this embodiment, the support range of the inner spherical surface 8 of bearing seat B in S8 is relatively large. If the surface contact rate of the outer spherical surface 4 of the test bearing 1 is consistently unqualified, it may be because there are protruding points within a range of 150mm × 150mm corresponding to the center of the surface of the inner spherical surface 8 of bearing seat B and the lower left and lower right support blocks 2 and 3 of the test bearing 1. In this case, it is permissible to grind the protruding points within this range of the inner spherical surface 8 of bearing seat B; otherwise, it is not permissible to grind any position of bearing seat A 5 and bearing seat B 7.
[0047] In this embodiment, a special grinding process was determined when assembling the test bearing with bearing housing B.
[0048] By grinding the test bearing using the above method, the area within 150mm×150mm of the center region 9 of the lower left support block 2 and the lower right support block 3 of the test bearing 1 achieved good contact with the inner spherical surface 6 of the A bearing housing 5; the area outside the center region 150mm×150mm of the lower left support block 2 and the lower right support block 3 of the test bearing 1 achieved good contact with the inner spherical surface 8 of the B bearing housing 7.
[0049] This invention establishes a process for assembling and grinding a test bearing with bearing housing A and bearing housing B respectively. Based on the different spherical surface conditions inside the bearing housings, the grinding area and method of the test bearing are determined, so as to enable the test bearing to be used on both bearing housings.
[0050] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by the present invention is defined by the claims and their equivalents.
Claims
1. A method for grinding bearings used in dynamic balancing tests of steam turbine generator rotors, characterized by the following steps: S1. Measure the clearance between the test bearing and bearing housing A after assembly: Install the test bearing (1) into bearing housing A (5) and measure the clearance between the outer spherical surface (4) of the lower left support block (2) and the lower right support block (3) of the test bearing (1) and the inner spherical surface (6) of bearing housing A. S2. Apply pigment to the spherical surface: Remove the test bearing (1) from the bearing housing (5) of A and apply white pigment to the outer spherical surface (4) of the test bearing (1); apply colored pigment to the inner spherical surface (6) of the bearing housing (6) corresponding to the lower left support block (2) and lower right support block (3) of the test bearing (1). S3. Check the spherical contact: Place the test bearing (1) into bearing housing (5) A and keep it for more than 2 minutes. Lift the test bearing (1) and check the area of the white pigment on the white pigment within the central area (9) of the outer spherical surface (4) of the lower left support block (2) and the lower right support block (3) of the test bearing (1) within 150mm×150mm. When the proportion of the pigmented area, i.e. the contact rate, exceeds 75%, and the contact rate within 25mm outside the oil hole of the outer spherical surface (4) of the lower right support block (3) with the oil hole reaches 100%, it is qualified. If it is not qualified, it needs to be ground. S4. Grinding test bearing: If the contact rate between the test bearing (1) and bearing housing (5) is not up to standard, use an electric grinding tool to grind the test bearing (1), remove the protruding point on its outer spherical surface (4), clean the pigment on the surface of the test bearing (1) and bearing housing (5), repeat S2 and S3, check the contact rate, if the contact rate is not up to standard, repeat the above process to continue grinding and checking until the contact rate is up to standard. S5. Measure the clearance between the test bearing and bearing housing B after assembly: Install the test bearing (1) into bearing housing B (7) and measure the clearance between the outer spherical surface (4) of the lower left support block (2) and the lower right support block (3) of the test bearing (1) and the inner spherical surface (8) of bearing housing B. S6. Apply pigment to the spherical surface: Remove the test bearing (1) from the bearing housing (7) of B and apply white pigment to the outer spherical surface (4) of the test bearing (1); apply colored pigment to the inner spherical surface (8) of the bearing housing of B at the positions corresponding to the lower left support block (2) and the lower right support block (3) of the test bearing (1). S7. Check the spherical contact: Place the test bearing (1) into the bearing housing (7) of B and keep it for more than 2 minutes; lift the test bearing (1) and check the area of the white pigment on the outer spherical surface (4) of the lower left support block (2) and the lower right support block (3) of the test bearing (1), except for the central area of 150mm×150mm. When the proportion of the area of the pigment, i.e. the contact rate, exceeds 75%, and the contact rate in the central area of 175mm×175mm of the outer spherical surface (4) of the lower right support block (3) with the oil inlet reaches 100%, it is qualified. If it is not qualified, it needs to be ground. S8. Grinding test bearing: If the contact rate between the test bearing (1) and bearing housing (7) B is not up to standard, use an electric grinding tool to grind the test bearing (1) to remove the protruding point on its outer spherical surface (4); grinding is not allowed within the 150mm×150mm range (9) of the center area of the lower left support block (2) and the lower right support block (3) of the test bearing (1); clean off the pigment on the surface of the test bearing (1) and bearing housing (7), repeat S6 and S7, check the contact rate, if the contact rate is not up to standard, repeat the above process to continue grinding and checking until the contact rate is up to standard.
2. The test bearing grinding method of claim 1 wherein: When measuring the gaps between the lower left support block (2) and the lower right support block (3) of the test bearing (1) and the inner spherical surface (6) of bearing housing A and bearing housing B in S1 and S5, feeler gauges should be used to measure all parts around the lower left support block (2) and the lower right support block (3).
3. The method for grinding bearings in a turbine generator rotor dynamic balancing test according to claim 1, characterized in that: The pigments applied to the lower left support block (2), lower right support block (3), inner spherical surface (6) of bearing seat A, and inner spherical surface (8) of bearing seat B in S2 and S6 should be uniform and consistent. The thickness should be measured using a thickness gauge after application.
4. The method for grinding bearings in a turbine generator rotor dynamic balancing test according to claim 1, characterized in that: During the operations of S3 and S7, the process of placing the test bearing (1) into and lifting out bearing housing A (5) and bearing housing B (7) must be completed in one step. The test bearing (1) must not move relative to each other within bearing housing A (5) and bearing housing B (7), otherwise it will affect the contact rate test results. If the test bearing (1) moves relative to each other within bearing housing A (5) and bearing housing B (7), the test bearing (1) must be lifted out, the paint on the surface of the test bearing (1), bearing housing A (5), and bearing housing B (7) must be cleaned, and then S3 and S7 can be performed again.
5. The method for grinding bearings in a turbine generator rotor dynamic balancing test according to claim 1, characterized in that: In S8, the support position range of the inner spherical surface (8) of bearing seat B is relatively large. If the contact rate of the outer spherical surface (4) of the test bearing (1) is always unqualified, and there are protruding points in the central area (9) of the left lower support block (2) and right lower support block (3) of bearing seat B corresponding to the test bearing (1) within a range of 150mm×150mm, then it is permissible to grind the protruding points in this range of the inner spherical surface (8) of bearing seat B. Otherwise, it is not permissible to grind any position of bearing seat A (5) and bearing seat B (7).