A method for inspecting and repairing the front bearing box of a steam turbine in a thermal power plant

Abstract

The invention discloses a method for inspecting and repairing the front bearing box of a steam turbine in a thermal power plant, and belongs to the technical field of steam turbine inspection and repair. The method removes the front bearing box without cutting off the steam inlet and steam extraction pipelines at the lower part of the high-pressure outer lower cylinder and without lifting the outer lower cylinder. By adopting the above method, the front bearing box can be safely, efficiently and economically removed for inspection and repair, which solves the defect that the front bearing box does not slide smoothly during the operation of the unit and causes large vibration of the bearing shell, improves the safety and stability of the unit operation, and removes the front bearing box without cutting off the air inlet and steam extraction pipelines at the lower part of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, which greatly saves time, manpower and materials.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine maintenance, and in particular to a method for maintaining a front bearing box of a steam turbine in a thermal power plant. Background Art

[0002] The front bearing box of the steam turbine is not only the carrier of the front bearing of the steam turbine rotor, but also contains a large number of thermal control original instruments, crisis security system pipeline equipment, etc. In terms of the box as a whole, the front bearing box of the steam turbine is also the front end support carrier of the high-pressure cylinder of the steam turbine. The front end of the high-pressure cylinder is supported on the front bearing box by two cat claws. The vertical surface of the front end of the high-pressure outer cylinder is connected to the front box with a vertical pin (assembly clearance 0.05~0.10mm) to fix the left and right position of the cylinder while ensuring that it can expand and move in the vertical direction. There are longitudinal pins at the bottom of the front box to fix the left and right position of the front bearing box while ensuring that the front bearing box can move longitudinally forward and backward during operation. There are also angle pins at the four corners of the bottom of the front bearing box to tighten and provide an expansion gap of 0.03~0.05mm between the angle pins and the bearing box body. During operation, the forward expansion of the high-pressure cylinder will be reflected from the longitudinal pins at the bottom of the front bearing box, and the vertical expansion will be reflected through the vertical pins connecting the cylinder and the bearing box.

[0003] As the unit runs for too long, the number of starts and stops increases, and the steam parameters change frequently, causing the unit to expand and contract frequently. The number of sliding surfaces at the bottom of the front bearing box increases, causing wear and tear on the sliding surface, which causes the bearing cover to vibrate excessively, and the bearing cover vibration is reflected in the excessive vibration during operation.

[0004] The aging, deterioration, rust and corrosion of the lubricating grease between the bottom of the front box and the front box platen increase the friction resistance of the front box, making the thrust and pull transmitted by the cat claws on the left and right sides of the front cylinder unbalanced, causing uneven expansion of the cylinder, and easily causing deformation of the front box, affecting the expansion of the cylinder and increasing the vibration of the unit. Only by dismantling the front box and checking the keyways and the overall sliding surface can the hidden danger be eliminated.

[0005] Since the high-pressure cylinder is mounted on the front bearing box, the overhaul is time-sensitive and the task is heavy. If the front bearing box can be removed without cutting the lower air intake and steam extraction pipes of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, it will greatly save time, manpower and materials. Summary of the invention

[0006] In order to overcome the technical problems in the background technology, the present invention provides a method for inspecting and repairing a front bearing box of a steam turbine in a thermal power plant.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] A method for inspecting the front bearing box of a steam turbine in a thermal power plant is provided, wherein the front bearing box is dismantled for inspection without cutting off the air intake and steam extraction pipes at the lower part of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, and the method specifically comprises the following steps: Step 1: Preparatory measures before dismantling

[0009] S11. Remove the four corner cross pins at the front and rear sides of the high and medium pressure outer cylinder;

[0010] S12, cutting and removing the oil inlet and outlet pipes connected to the main oil pump in the front bearing box;

[0011] S13, cutting and removing the oil inlet and outlet pipes connected to the bearing in the front bearing box;

[0012] S14. Remove or cut the oil pipes related to the emergency shut-off system;

[0013] S15. Measure the positioning dimensions of the front bearing box and the table;

[0014] S16, remove the front bearing box angle pin;

[0015] S17, prepare the lower cylinder lifting tool;

[0016] S18. Temporary measuring points are welded between the front bearing box and the table to detect the change of the front bearing box position during reinstallation. Temporary measuring points are made on the left and right sides of the lower cylinder to monitor the left and right shaking of the cylinder during the cylinder lifting.

[0017] S19. Remove the thermal control components and circuits connected to the front bearing box;

[0018] Step 2: Remove the front bearing box

[0019] S21, the upper part of the front bearing box is removed, and the internal control circuit and the lower oil pipe are cut off;

[0020] S22, the upper half of the bearing is removed and the coupling is released;

[0021] S23, remove the upper half of the high and medium pressure cylinders and empty the inside of the cylinders;

[0022] S24. According to the actual measurements of the specific dimensions on site, the lifting cylinder support frame is manufactured on site;

[0023] S25. Clean the debris at the connection between the high-pressure outer cylinder and the front bearing box and the bearing box, check and measure the vertical pin sliding fit clearance and axial expansion clearance, and record them;

[0024] S26, measure the clearances of the front cat claw cross pin, make a record, then spray the cat claw pressure plate bolts with rust loosening liquid, remove the bolts on both sides, pull out the pin bolts, and take out the lower pressure block of the cat claw pin;

[0025] S27. Use a cylinder lifting tool to lift the cylinder by 0.5-1.0 mm, based on the actual height at which the shim can be pulled out, pull out the shim below the cylinder claw, check the contact between the cylinder claw and the bearing box shim, the load distribution, and record them, then restore the shim and drop the cylinder;

[0026] S28. Reconfirm and review the clearance values ​​of the sliding pins of each part, the longitudinal, transverse, horizontal values ​​and lift values ​​of the cylinder and the front bearing box; loosen the bolts connecting the rear cylinder and the support frame appropriately, and use the cylinder lifting tool to lift the high-pressure cylinder by 10 to 20 mm and fix it;

[0027] S29. Use the bridge crane and hand chain hoist to pull out the front bearing box, and check again whether the changes of the dial indicators at each monitoring point are within the allowable range;

[0028] Step 3: Check and handle the front bearing box

[0029] S31. Clean the rust, oil and burrs on the surface of the lower platen of the front bearing box, the bottom surface of the front bearing box and the longitudinal pins of the front bearing box. Grind the bottom surface of the front bearing box and the platen until the contact surface reaches more than 75% after color inspection, and the contact points are evenly distributed. The full circumferential clearance between the platen and the base is less than 0.05mm. The front bearing box slides freely on the platen and has no other defects such as grooves. It should be polished to pass.

[0030] Step 4: Reinstall the front bearing box

[0031] S41. Before reinstallation, add molybdenum disulfide grease to the oil passage between the bottom of the front bearing box and the table, apply molybdenum disulfide dry powder on the surface of both, and clear the oil drain and oil filling ports of the oil passage to facilitate regular oiling and lubrication during operation;

[0032] S42, the process of reinstalling the front bearing box is the reverse process of taking it out;

[0033] S43. After the front bearing box is reinstalled, the vertical pins connecting the cylinder and the front bearing box should be reinstalled, and the clearance should be adjusted strictly according to the design requirements;

[0034] S44. After the vertical pin is prepared, use the micrometer installed in front of the front bearing box to check the cylinder's left and right and up and down displacement change. The value should not be greater than 0.05mm. Otherwise, the cause should be found out and the cylinder position should be readjusted. At this point, the inspection and maintenance of the front bearing box is completed.

[0035] Further preferably, in the preparatory measures before dismantling in step 1, if the left and right deviations exceed 0.08 mm, S18, correction is stopped, and the parts should be adjusted to the original position after reinstallation.

[0036] Preferably, in step 2, before removing the front bearing box, it is necessary to ensure that the lower cylinder is empty and there are no speed regulating sleeves or oil pipe connections inside or outside the front bearing box.

[0037] Preferably, in step 2 S28, the rear of the cylinder is checked to see whether the changes of the dial indicators of each monitoring point are within the allowable range, and then the cylinder is supported by a fixed bracket.

[0038] Preferably, after the front bearing box S29 is taken out in step 2, a dedicated person checks the cylinder monitoring point dial indicator every hour and records it. If it is found that the dial indicator sinks more than 0.1 mm, a jack or a crane support should be added in time to avoid excessive sinking of the cylinder support.

[0039] Preferably, in step three S31, if the longitudinal pin and the vertical pin are damaged and the gap is too large, they need to be re-configured. The pre-repair measurement data, installation records, design specifications, and actual measurement of the cylinder level and lift values ​​should be referred to for restoration and configuration. The materials used must undergo metal inspection and have suitable hardness before use.

[0040] Preferably, the method for grinding the bottom surface of the front bearing box and the table plate in step three is:

[0041] By using the angle pin bolts on both sides of the table, the front bearing box body is moved back and forth with the cooperation of a crowbar, a jack, and a hand hoist to achieve the purpose of grinding.

[0042] Preferably, the front bearing box reinstallation process in step 4 requires measurement of various data, and comparison with the data measured during disassembly, and then adjustment and assembly until qualified.

[0043] Beneficial effects of the present invention:

[0044] By adopting the above method, the front bearing box can be removed for inspection and maintenance safely, efficiently and economically, which solves the defect of large bearing vibration caused by poor sliding of the front bearing box during unit operation, improves the safe and stable operation of the unit, and removes the front bearing box without cutting the lower air intake and steam extraction pipes of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, thereby greatly saving time, manpower and materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a process flow chart of the present invention;

[0046] Figure 2 This is a schematic diagram of the connection between the front bearing box and the high-pressure cylinder of the present invention;

[0047] Figure 3 It is a schematic diagram of the lifting cylinder of the present invention.

[0048] Parts and numbers in the picture:

[0049] 1-front bearing box; 11-longitudinal pin; 12-angle pin; 2-high-pressure cylinder; 21-vertical pin; 22-cat's claw cross pin. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Embodiment 1

[0052] like Figure 2 As shown, the interior of the front bearing box 1 of the steam turbine is not only the carrier of the front bearing of the steam turbine rotor, but also contains a large number of thermal control original instruments, crisis security system pipeline equipment, etc. As far as the box body is concerned, the front bearing box 1 of the steam turbine is also the front end support carrier of the high-pressure cylinder 2 of the steam turbine. The front end of the high-pressure cylinder 2 is supported on the front bearing box 1 by two cat claws. The vertical surface of the front end of the high-pressure outer cylinder is connected to the front bearing box 1 with a vertical pin 21 (the assembly clearance is required to be 0.04-0.8mm) to fix the left and right position of the cylinder while ensuring that the vertical direction can expand and move. The bottom of the front bearing box 1 has a longitudinal pin 11 to fix the left and right position of the front bearing box 1 while ensuring that the front bearing box 1 can move longitudinally forward and backward during operation. There are also angle pins 12 at the four corners of the bottom of the front bearing box 1, and there is an expansion gap of 0.03-0.05mm between the angle pins 12 and the bearing box body. During operation, the forward expansion of the high-pressure cylinder 2 will be reflected from the longitudinal pin 11 at the bottom of the front bearing box 1, and the vertical expansion will be reflected through the vertical pin 21 connecting the cylinder and the bearing box.

[0053] During the operation of the steam turbine of unit #3 of a power plant, the maximum vibration value of the #1 bearing cover was detected to be too large, reaching 0.085mm, which seriously exceeded the design specifications. After long-term operation, the fasteners of the speed regulating sleeve installed on the front bearing box 1 became loose. When the unit was started, the micrometer was used to detect the uneven expansion between the bottom of the left and right front bearing boxes 1 and the table plate, and the left and right deviations reached 8.0mm, seriously affecting the safety and stability of the unit.

[0054] The maintenance method of the present invention is used to dismantle the front bearing box 1 of the steam turbine for maintenance:

[0055] A method for overhauling a front bearing box 1 of a steam turbine in a thermal power plant, wherein the front bearing box 1 is dismantled for overhaul without cutting off the air intake and steam extraction pipelines at the lower part of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, and specifically comprises the following steps:

[0056] Step 1: Preparatory measures before demolition:

[0057] S11. Remove the four corner cross pins at the front and rear sides of the high and medium pressure outer cylinder;

[0058] S12, cutting and removing the oil inlet and outlet pipes connected to the main oil pump in the front bearing box 1;

[0059] S13, cutting and removing the oil inlet and outlet pipes connected to the #1 bearing in the front bearing box 1;

[0060] S14. Remove or cut the oil pipes related to the emergency shut-off system;

[0061] S15. Measure the positioning dimensions (elevation and lift) of the front bearing box 1 and the table;

[0062] S16, remove the four corner pins 12 of the front bearing box 1;

[0063] S17, prepare the lower cylinder top cylinder tool, such as Figure 3 (2 100T jacks, U-shaped connecting bolts, brackets, pressure plates, etc., steel beams and brackets are prepared on site);

[0064] S18, temporary measuring points are welded between the front bearing box 1 and the table to detect the change of the position of the front bearing box 1 during reinstallation, and temporary measuring points are made on the left and right sides of the lower cylinder to monitor the left and right shaking of the cylinder during the cylinder lifting;

[0065] S19, removing the thermal control components and circuits connected to the front bearing box 1;

[0066] Only after the above preparation conditions are met can the work of lifting the cylinder and extracting the front bearing box 1 be carried out.

[0067] Step 2: Remove the front bearing box 1:

[0068] S21, the upper half of the front bearing box 1 is removed, and the internal control circuit and the lower oil pipe are cut off;

[0069] S22, the upper half of the bearing is removed and the coupling is released;

[0070] S23, remove the upper half of the high and medium pressure cylinders and empty the inside of the cylinders;

[0071] S24. According to the actual measurements of the specific dimensions on site, the lifting cylinder support frame is manufactured on site;

[0072] S25. Clean the debris from the connection between the high-pressure outer cylinder and the front bearing box 1 and #2 bearing box, check and measure the sliding fit clearance and axial expansion clearance of the vertical pin 21, and record them;

[0073] S26, measure the clearances of the front cat claw cross pin 22, make a record, then spray the cat claw pressure plate bolts with rust loosening liquid, remove the bolts on both sides, pull out the pin bolts, and take out the lower pressure block of the cat claw pin;

[0074] S27. Use a cylinder lifting tool to lift the cylinder by 0.5 mm, pull out the shim at the bottom of the cylinder claw, check the contact between the cylinder claw and the bearing box shim, the load distribution, and record them, then restore the shim and drop the cylinder;

[0075] S28. Reconfirm and review the clearance values ​​of the sliding pins of each part, the longitudinal, transverse, horizontal values ​​and lift values ​​of the cylinder and the front bearing box 1; loosen the bolts connecting the rear cylinder and the support frame appropriately, and use the cylinder lifting tool to lift the high-pressure cylinder 2 by 10mm and fix it;

[0076] S29. Use the bridge crane and the hand chain hoist to pull out the front bearing box 1, and check again whether the changes of the dial indicators at each monitoring point are within the allowable range;

[0077] Step 3: Check and handle the front bearing box 1:

[0078] S31. Clean the rust, oil stains and burrs on the surface of the lower table of the front bearing box 1, the bottom surface of the front bearing box 1 and the longitudinal pin 11 of the front bearing box 1. Grind the bottom surface of the front bearing box 1 and the table until the contact surface reaches more than 75% after color inspection, and the contact points are evenly distributed. The full circumferential clearance between the table and the base is less than 0.05mm. The front bearing box 1 slides freely on the table, and there are no other defects such as grooves. The grinding should be qualified;

[0079] Step 4: Reinstall the front bearing box 1:

[0080] S41. Before reinstallation, add molybdenum disulfide grease to the oil passage between the bottom surface of the front bearing box 1 and the table plate, apply molybdenum disulfide dry powder on the surface of both, and clear the oil drain and oil filling ports of the oil passage to facilitate regular oiling and lubrication during operation;

[0081] S42, the reinstallation process of the front bearing box 1 is the reverse process of the removal process;

[0082] S43. After the front bearing box 1 is reinstalled, the vertical pin 21 connecting the cylinder and the front bearing box 1 should be reinstalled, and the clearance should be adjusted strictly according to the design requirements;

[0083] S44. After the preparation of the vertical pin 21 is completed, use the micrometer installed in front of the front bearing box 1 to check the cylinder's left and right and up and down displacement changes. The value should not be greater than 0.05mm. Otherwise, the cause should be found out and the cylinder position should be readjusted. At this point, the inspection and maintenance work of the front bearing box 1 is completed.

[0084] Further preferably, in step 1, if the left-right deviation exceeds 0.08 mm, the correction is stopped in S18, and the machine should be adjusted to the original position after reinstallation.

[0085] Preferably, in step 2, before removing the front bearing box 1 , it is necessary to ensure that the lower cylinder is empty and there are no speed regulating sleeves or oil pipe connections inside or outside the front bearing box 1 .

[0086] Preferably, in step 2 S28, the rear of the cylinder is checked to see whether the changes of the dial indicators of each monitoring point are within the allowable range, and then the cylinder is supported by a fixed bracket.

[0087] Preferably, after the front bearing box 1 is taken out in step 2 S29, a dedicated person checks the cylinder monitoring point dial indicator every hour and records it. If it is found that the dial indicator sinks more than 0.1 mm, a jack or a crane support should be added in time to avoid excessive sinking of the cylinder support.

[0088] Preferably, in step three S31, if the longitudinal pin 11 and the vertical pin 21 are damaged and the gap is too large, they need to be re-configured. The pre-repair measurement data, installation records, design specifications, and actual measurement of the cylinder level and lift values ​​should be referred to for restoration and configuration. The materials used must undergo metal inspection and have suitable hardness before use.

[0089] Preferably, the method for grinding the bottom surface of the front bearing box 1 and the table plate in step 3 is:

[0090] By using the angle pins 12 bolts on both sides of the table, the front bearing box 1 body is moved back and forth with a crowbar, a jack, and a hand hoist to achieve the purpose of grinding.

[0091] Preferably, the reinstallation process of the front bearing box 1 in step 4 requires measurement of various data, and comparison with the data measured during disassembly, and then adjustment and assembly until qualified.

[0092] The maintenance work of the front bearing box 1 of #3 machine has been completed. After the treatment, the vibration values ​​of #1, #2 bearings and bearing boxes were measured when the machine was started, which decreased significantly (see Table 1 below). When the machine was started, the thermal expansion deviation value at both ends of the front bearing box 1 was measured to be 1.5mm, which was significantly lower than the deviation value of 8mm before the maintenance, meeting the design specifications and achieving the expected effect.

[0093] Table 1 Unit: mm

[0094]

[0095]

[0096] Embodiment 2

[0097] When the steam turbine of the #4 unit of a thermal power plant of a certain chemical group in Shaanxi was started, the thermal expansion deviation value at both ends of the front bearing box 1 was measured to be 7.6mm. After long-term operation, the fasteners of the speed regulating sleeve installed on the front bearing box 1 became loose. When the unit was started, the micrometer was used to detect the uneven expansion between the bottom of the left and right front bearing boxes 1 and the table plate. The maintenance method of the present invention was used to dismantle the front bearing box 1 of the steam turbine for maintenance.

[0098] A method for overhauling a front bearing box 1 of a steam turbine in a thermal power plant, wherein the front bearing box 1 is dismantled for overhaul without cutting off the air intake and steam extraction pipelines at the lower part of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, and specifically comprises the following steps:

[0099] Step 1: Preparatory measures before demolition:

[0100] S11. Remove the four corner cross pins at the front and rear sides of the high and medium pressure outer cylinder;

[0101] S12, cutting and removing the oil inlet and outlet pipes connected to the main oil pump in the front bearing box 1;

[0102] S13, cutting and removing the oil inlet and outlet pipes connected to the #1 bearing in the front bearing box 1;

[0103] S14. Remove or cut the oil pipes related to the emergency shut-off system;

[0104] S15. Measure the positioning dimensions (elevation and lift) of the front bearing box 1 and the table;

[0105] S16, remove the four corner pins 12 of the front bearing box 1;

[0106] S17, prepare the lower cylinder top cylinder tool, such as Figure 3 (2 100T jacks, U-shaped connecting bolts, brackets, pressure plates, etc., steel beams and brackets are prepared on site);

[0107] S18, temporary measuring points are welded between the front bearing box 1 and the table to detect the change of the position of the front bearing box 1 during reinstallation, and temporary measuring points are made on the left and right sides of the lower cylinder to monitor the left and right shaking of the cylinder during the cylinder lifting;

[0108] S19, removing the thermal control components and circuits connected to the front bearing box 1;

[0109] Only after the above preparation conditions are met can the work of lifting the cylinder and extracting the front bearing box 1 be carried out.

[0110] Step 2: Remove the front bearing box 1:

[0111] S21, the upper half of the front bearing box 1 is removed, and the internal control circuit and the lower oil pipe are cut off;

[0112] S22, the upper half of the bearing is removed and the coupling is released;

[0113] S23, remove the upper half of the high and medium pressure cylinders and empty the inside of the cylinders;

[0114] S24. According to the actual measurements of the specific dimensions on site, the lifting cylinder support frame is manufactured on site;

[0115] S25. Clean the debris from the connection between the high-pressure outer cylinder and the front bearing box 1 and #2 bearing box, check and measure the sliding fit clearance and axial expansion clearance of the vertical pin 21, and record them;

[0116] S26, measure the clearances of the front cat claw cross pin 22, make a record, then spray the cat claw pressure plate bolts with rust loosening liquid, remove the bolts on both sides, pull out the pin bolts, and take out the lower pressure block of the cat claw pin;

[0117] S27. Use a cylinder lifting tool to lift the cylinder 1.0 mm, pull out the shim at the bottom of the cylinder claw, check the contact between the cylinder claw and the bearing box shim, load distribution, and record them, then restore the shim and drop the cylinder;

[0118] S28. Reconfirm and review the clearance values ​​of the sliding pins of each part, the longitudinal, transverse, horizontal values ​​and lift values ​​of the cylinder and the front bearing box 1; loosen the bolts connecting the rear cylinder and the support frame appropriately, and use the cylinder lifting tool to lift the high-pressure cylinder 2 by 20mm and fix it;

[0119] S29. Use the bridge crane and the hand chain hoist to pull out the front bearing box 1, and check again whether the changes of the dial indicators at each monitoring point are within the allowable range;

[0120] Step 3: Check and handle the front bearing box 1:

[0121] S31. Clean the rust, oil stains and burrs on the surface of the lower table of the front bearing box 1, the bottom surface of the front bearing box 1 and the longitudinal pin 11 of the front bearing box 1. Grind the bottom surface of the front bearing box 1 and the table until the contact surface reaches more than 75% after color inspection, and the contact points are evenly distributed. The full circumferential clearance between the table and the base is less than 0.05mm. The front bearing box 1 slides freely on the table, and there are no other defects such as grooves. The grinding should be qualified;

[0122] Step 4: Reinstall the front bearing box 1:

[0123] S41. Before reinstallation, add molybdenum disulfide grease to the oil passage between the bottom surface of the front bearing box 1 and the table plate, apply molybdenum disulfide dry powder on the surface of both, and clear the oil drain and oil filling ports of the oil passage to facilitate regular oiling and lubrication during operation;

[0124] S42, the reinstallation process of the front bearing box 1 is the reverse process of the removal process;

[0125] S43. After the front bearing box 1 is reinstalled, the vertical pin 21 connecting the cylinder and the front bearing box 1 should be reinstalled, and the clearance should be adjusted strictly according to the design requirements;

[0126] S44. After the preparation of the vertical pin 21 is completed, use the micrometer installed in front of the front bearing box 1 to check the cylinder's left and right and up and down displacement changes. The value should not be greater than 0.05mm. Otherwise, the cause should be found out and the cylinder position should be readjusted. At this point, the inspection and maintenance work of the front bearing box 1 is completed.

[0127] Further preferably, in step 1, if the left-right deviation exceeds 0.08 mm, the correction is stopped in S18, and the machine should be adjusted to the original position after reinstallation.

[0128] Preferably, in step 2, before removing the front bearing box 1 , it is necessary to ensure that the lower cylinder is empty and there are no speed regulating sleeves or oil pipe connections inside or outside the front bearing box 1 .

[0129] Preferably, in step 2 S28, the rear of the cylinder is checked to see whether the changes of the dial indicators of each monitoring point are within the allowable range, and then the cylinder is supported by a fixed bracket.

[0130] Preferably, after the front bearing box 1 is taken out in step 2 S29, a dedicated person checks the cylinder monitoring point dial indicator every hour and records it. If it is found that the dial indicator sinks more than 0.1 mm, a jack or a crane support should be added in time to avoid excessive sinking of the cylinder support.

[0131] Preferably, in step three S31, if the longitudinal pin 11 and the vertical pin 21 are damaged and the gap is too large, they need to be re-configured. The pre-repair measurement data, installation records, design specifications, and actual measurement of the cylinder level and lift values ​​should be referred to for restoration and configuration. The materials used must undergo metal inspection and have suitable hardness before use.

[0132] Preferably, the method for grinding the bottom surface of the front bearing box 1 and the table plate in step 3 is:

[0133] By using the angle pins 12 bolts on both sides of the table, the front bearing box 1 body is moved back and forth with a crowbar, a jack, and a hand hoist to achieve the purpose of grinding.

[0134] Preferably, the reinstallation process of the front bearing box 1 in step 4 requires measurement of various data, and comparison with the data measured during disassembly, and then adjustment and assembly until qualified.

[0135] The maintenance work of the front bearing box 1 of #4 machine has been completed. After the treatment, the vibration values ​​of #1, #2 bearings and bearing boxes were measured when the machine was started, which decreased significantly (see Table 2 below). When the machine was started, the thermal expansion deviation value at both ends of the front bearing box 1 was measured to be 1.3mm, which was significantly lower than the deviation value of 7.6mm before the maintenance, which met the design specifications and achieved the expected effect.

[0136] Table 2 Unit: mm

[0137]

[0138] This method solves the problem of large vibration of the bearing shell caused by poor sliding of the front bearing box 1 during the operation of the unit, improves the safety and stability of the unit operation, and indirectly creates greater economic benefits. The dismantling and inspection method of the front bearing box 1 is representative and advanced, and is worthy of reference in similar projects.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for overhauling the front bearing box of a steam turbine in a thermal power plant, characterized in that: Without cutting off the steam inlet and extraction pipes at the bottom of the high-pressure outer lower cylinder and without lifting the outer lower cylinder, the front bearing box is dismantled for maintenance, which specifically includes the following steps: Step 1: Preparatory measures before demolition S11. Remove the four corner cross pins at the front and rear sides of the high and medium pressure outer cylinder; S12, cutting and removing the oil inlet and outlet pipes connected to the main oil pump in the front bearing box; S13, cutting and removing the oil inlet and outlet pipes connected to the bearing in the front bearing box; S14. Remove or cut the oil pipes related to the emergency shut-off system; S15. Measure the positioning dimensions of the front bearing box and the table; S16, remove the front bearing box angle pin; S17, prepare the lower cylinder lifting tool; S18. Temporary measuring points are welded between the front bearing box and the table to detect the change of the front bearing box position during reinstallation. Temporary measuring points are made on the left and right sides of the lower cylinder to monitor the left and right shaking of the cylinder during the cylinder lifting. S19. Remove the thermal control components and circuits connected to the front bearing box; Step 2: Remove the front bearing box S21, the upper part of the front bearing box is removed, and the internal control circuit and the lower oil pipe are cut off; S22, the upper half of the bearing is removed and the coupling is released; S23, remove the upper half of the high and medium pressure cylinders and empty the inside of the cylinders; S24. According to the actual measurements of the specific dimensions on site, the lifting cylinder support frame is manufactured on site; S25. Clean the debris at the connection between the high and medium pressure outer cylinder and the front bearing box and the bearing box, check and measure the sliding fit clearance and axial expansion clearance of the high and medium pressure outer cylinder pins, and record them; S26, measure the clearances of the front cat claw cross pin, make a record, then spray the cat claw pressure plate bolts with rust loosening liquid, remove the bolts on both sides, pull out the pin bolts, and take out the lower pressure block of the cat claw pin; S27. Use a cylinder lifting tool to lift the cylinder by 0.5-1.0 mm, based on the actual height at which the shim can be pulled out, pull out the shim below the cylinder claw, check the contact between the cylinder claw and the bearing box shim, the load distribution, and record them, then restore the shim and drop the cylinder; S28. Reconfirm and review the clearance values ​​of the sliding pins of each part, the longitudinal, transverse, horizontal values ​​and lift values ​​of the cylinder and the front bearing box; loosen the bolts connecting the rear cylinder and the support frame appropriately, and use the cylinder lifting tool to lift the high-pressure cylinder by 10 to 20 mm and fix it; S29. Use the bridge crane and hand chain hoist to pull out the front bearing box, and check again whether the changes of the dial indicators at each monitoring point are within the allowable range; Step 3: Check and handle the front bearing box S31. Clean the rust, oil and burrs on the surface of the lower platen of the front bearing box, the bottom surface of the front bearing box and the longitudinal pins of the front bearing box. Grind the bottom surface of the front bearing box and the platen until the contact surface reaches more than 75% after color inspection, and the contact points are evenly distributed. The full circumferential clearance between the platen and the base is less than 0.05mm. The front bearing box slides freely on the platen and has no other defects such as grooves. It should be polished to pass. Step 4: Reinstall the front bearing box S41. Before reinstallation, add molybdenum disulfide grease to the oil passage between the bottom of the front bearing box and the table, apply molybdenum disulfide dry powder on the surface of both, and clear the oil drain and oil filling ports of the oil passage to facilitate regular oiling and lubrication during operation; S42, the process of reinstalling the front bearing box is the reverse process of taking it out; S43. After the front bearing box is reinstalled, the vertical pins connecting the cylinder and the front bearing box should be reinstalled, and the clearance should be adjusted strictly according to the design requirements; S44. After the vertical pin is prepared, use the micrometer installed in front of the front bearing box to check the cylinder's left and right and up and down displacement change. The value should not be greater than 0.05mm. Otherwise, the cause should be found out and the cylinder position should be readjusted. At this point, the inspection and maintenance of the front bearing box is completed.

2. A method for overhauling a front bearing box of a steam turbine in a thermal power plant according to claim 1, characterized in that: In step 1, if the left-right deviation of S18 exceeds 0.08 mm, the correction is stopped, and the machine should be adjusted to the original position after reinstallation.

3. A method for overhauling a front bearing box of a steam turbine in a thermal power plant according to claim 2, characterized in that: In step 2, before removing the front bearing box, it is necessary to ensure that the lower cylinder is empty and there are no speed regulating sleeves or oil pipes connected inside or outside the front bearing box.

4. A method for overhauling a front bearing box of a steam turbine in a thermal power plant according to claim 3, characterized in that: In step 2, S28 checks the change of the dial indicator at each monitoring point at the rear of the cylinder to ensure that it is within the allowable range, and then supports the cylinder with a fixed bracket.

5. A method for overhauling a front bearing box of a steam turbine in a thermal power plant according to claim 4, characterized in that: After the S29 front bearing box is taken out in step 2, a dedicated person shall check the cylinder monitoring point dial indicator every hour and record it. If the dial indicator settlement is found to exceed 0.1mm, a jack or a crane support shall be added in time to avoid excessive sinking of the cylinder support.

6. A method for overhauling a front bearing box of a steam turbine in a thermal power plant according to claim 5, characterized in that: In step three, if the longitudinal pin and vertical pin are damaged and the gap is too large, they need to be re-matched. The pre-repair measurement data, installation records, design specifications, and actual measurement of the cylinder level and lift values ​​should be referred to for restoration and matching. The materials used must be metal inspected and have suitable hardness before use.

7. A method for overhauling the front bearing box of a steam turbine in a thermal power plant according to claim 6, characterized in that: The method for grinding the bottom surface of the front bearing box and the table plate in step 3 is: By using the angle pin bolts on both sides of the table, the front bearing box body is moved back and forth with the cooperation of a crowbar, a jack, and a hand hoist to achieve the purpose of grinding.

8. A method for overhauling a front bearing box of a steam turbine in a thermal power plant according to claim 6, characterized in that: The process of reinstalling the front bearing box in step 4 requires measuring various data and comparing them with the data measured during disassembly, and then adjusting and assembling them until they are qualified.

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