Construction method for quickly repairing bushing burning of steam turbine generator unit

Abstract

The application discloses a construction method for quickly repairing bush burning loss of a steam turbine generator unit, and specifically comprises the following steps: supporting bush replacement, thrust bush replacement, back wheel center finding, oil / wind baffle installation, and turning over debugging detection. The application accurately measures the bush burning loss and the shaft diameter subsidence, combines the unit shaft seal retreat clearance, the blade top peak expansion clearance and the axial minimum limiting K value, determines that there is no mechanical rubbing damage in the unit, temporarily supports the rotor, removes the damaged bush, replaces the spare parts or pours and repairs the bush with new gold, adjusts the bush height according to the bush installation top clearance, the oil baffle top clearance, the bridge gauge record, the wind baffle top clearance and the air clearance value after the bush is installed, and restores the design operation center value, so that the fault repair can be carried out without uncovering the cylinder, the maintenance range is reduced, the equipment hidden danger is eliminated, the construction period is short, the method is safe and reliable, and is easy to popularize.

Description

Technical Field

[0001] This invention relates to a bearing repair method, and more particularly to a construction method for quickly repairing burnt bearings of steam turbine generator sets, belonging to the field of steam turbine maintenance technology. Background Technology

[0002] During the production and operation of thermal power plants, lubrication interruption or oil film damage caused by system or equipment failure, oil quality deterioration, or improper operation frequently leads to the burning of the bearing bushes in the turbine generator set. After the bearing bushes burn out, it can cause localized heat bending of the unit rotor, increased axial displacement, uneven dynamic and static clearances leading to rubbing and other hazards, and may even cause serious accidents such as the scrapping of the unit's shaft system. After the original bearing bushes burn out, due to the lack of experience and data comparison precedents for non-cylinder-opening maintenance, power plants usually adopt the cylinder cover-opening maintenance method for visual inspection and treatment of defects. This method requires a complete disassembly and overhaul of the turbine generator set, which has a large maintenance scope and a long maintenance period, thus increasing the power plant's maintenance costs and downtime. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a construction method for quickly repairing the burn-out bearings of steam turbine generator sets. Under the premise of ensuring that the safety and efficiency of the unit are not affected, the bearing burn-out defects are eliminated in the shortest time and at the lowest cost, thereby minimizing accident losses.

[0004] The technical solution adopted by this invention to solve the technical problem is as follows: A construction method for quickly repairing burnt-out bearings of steam turbine generator sets includes the following steps: A. Construction Preparation ① Prepare the lifting machinery, tools and protective equipment required for construction and high-altitude operations, and conduct insulation tests on electrical tools; ② Remove and move the top covers of each bearing away, temporarily seal the inlet and outlet oil passages of the main oil pump and the inlet and outlet oil passages of the bearing housing, and check whether there are any debris or black metal fragments at the bottom of the bearing box. ③ Disassemble the upper half of each bearing shell, measure the top clearance and record it. At the same time, measure the clearance of the oil baffle, wind baffle and end shaft seal, and calculate the shaft system elevation and axial displacement based on the measurement records and the original installation records. B. Supports tile replacement ① Remove the old tiles, clean and repair the shaft diameter; ② Measure the shaft diameter and cylindricality, adjust and replace or recast and repair the spare tile shaft according to the shaft diameter, and then find the relative center of the shaft and the tile with the arc surface of the tile body as the reference, and adjust the gap between the tile shaft and the cylindrical shaft. ③ Based on the original installation records of the bearing housing recess and shaft seal clearance, adjust the center of the shaft recess by grinding the bearing bush shims. When grinding the bushing and adjusting the shims, the contact area should be greater than 75% and the contact surface should be uniform. C. Replacement of thrust bearings ① Remove the old thrust bearings, clean and repair the thrust disc; ② Measure the deflection value of the thrust plate, and determine the thickness of the thrust pad on the working face based on the axial displacement value, relative expansion value, and the value derived from the installation K value; ③ First, perform individual measurement and grinding on the working and non-working tiles to ensure that the thickness difference between the tiles is less than 0.02mm; then install the front and rear thrust tiles and perform disc rotor grinding. When each thrust tile is in contact with uniform force and the contact area reaches more than 75%, adjust the adjusting shims on the non-working surface according to the required thrust clearance. D. Find the center using the backrest wheels. ① Using the turbine rotor as a reference, adjust the generator or gearbox by moving the generator bearing housing, gearbox, or increasing or decreasing the thickness of the bearing housing shims to adjust the outer circle and opening deviation of the back wheel within the required range. ② After the shaft center alignment is completed, install the back-to-back wheel coupling and use the suspended shaft method to check the rotor concentricity deviation. E. Reinstall the accelerator and windshield. ① Scrape the tips of the oil baffle and windshield, and install and restore the oil baffle and windshield according to the design gap to keep the oil return channel of the oil baffle unobstructed; ② For oil baffles that rely on gravity for sealing, the sealant on the mating surfaces should be uniform and maintain a thickness of 0.2mm-0.3mm; the gaps around the windshields should be uniform. F. Turning and testing ① After the unit has been overhauled, start the lubricating oil pump and slowly open the outlet valve or overflow valve to keep the oil pressure within the specified range, and inject oil into the system to raise its temperature. ② Observe the oil return volume of each bearing housing and adjust the oil volume by adding a throttling orifice plate so that the height of the return oil level is 1 / 4-2 / 3 of the pipe cross-section; the oil return volume of the thrust bearing is controlled by a regulating valve. ③ Start the turning gear. When the oil temperature reaches the operating requirements, recheck and adjust the system lubricating oil pressure and the return oil height of the return oil pipeline; check the turning gear current and compare it with the normal value, and listen for any abnormal noises inside the cylinder. ④ Through a low oil pressure interlock test, the interlock performance of the oil pumps should be fully tested to ensure that it meets the requirements. At the same time, the oil quantity and oil pressure of each oil pump should be adjusted to the design range.

[0005] When the cylinder temperature is below 120°C, the oil pump can be stopped and the bearing housing can be opened for bearing maintenance. After the bearing housing is opened, the inside of the inlet and return oil pipes should be cleaned and the oil ports temporarily sealed. Then, the quality of the lubricating oil should be tested, and the main oil tank and inlet and return oil pipes should be flushed and cleaned, and the system filter screen should be replaced.

[0006] Before reinstalling the bearing bush and oil baffle, thoroughly clean the bearing housing and the inside of the oil inlet pipe, and use dough to completely remove the internal oil stains and other impurities before reinstallation.

[0007] When aligning the shaft system, two rotors should be rotated simultaneously to measure the corresponding positions.

[0008] The positive and beneficial effects of this invention are: 1. This invention analyzes historical trends of DCS, unit design, and installation data, and combines this with actual on-site inspection and measurement of each bearing bush. Through scientific analysis and data comparison, it accurately judges the damage and health status of the shaft system, thus preventing the escalation of the accident's impact. Using this method, the repair period can be controlled within 4-7 days, thereby eliminating bearing bush burn-out defects in the shortest time and at the lowest cost, minimizing accident losses.

[0009] 2. This invention accurately measures the amount of bearing burnout and shaft diameter subsidence, and combines this with the unit's shaft seal clearance, blade tip expansion clearance, and axial minimum limit K value to determine that there is no mechanical wear damage inside the unit. Then, temporary support is provided for the rotor, the damaged bearing is removed, and it is replaced with a spare part or repaired by recasting with black metal. After the bearing is reinstalled, the bearing elevation is adjusted according to the bearing installation top clearance, oil baffle top clearance, bridge gauge records, windshield top clearance, and air gap values ​​to restore it to the design operating center value. This allows for emergency repairs without opening the cylinder, reducing the scope of maintenance, eliminating potential equipment hazards, shortening the construction period, and ensuring safety and reliability. Detailed Implementation

[0010] The present invention will be further explained and described below with reference to the solution: An example of a construction method for quickly repairing burnt-out bearings of a steam turbine generator set includes the following steps: A. Construction Preparation ① Prepare the lifting machinery, tools and protective equipment required for construction and high-altitude operations, and conduct insulation tests on electrical tools; ② Remove and move the top covers of each bearing away, temporarily seal the inlet and outlet oil passages of the main oil pump and the inlet and outlet oil passages of the bearing housing, and check whether there are any debris or black metal fragments at the bottom of the bearing box. ③ Disassemble the upper half of each bearing shell, measure the top clearance and record it. At the same time, measure the clearance of the oil baffle, wind baffle and end shaft seal, and calculate the shaft system elevation and axial displacement based on the measurement records and the original installation records. B. Supports tile replacement ① Remove the old tiles, clean and repair the shaft diameter; ② Measure the shaft diameter and cylindricality, adjust and replace or recast and repair the spare tile shaft according to the shaft diameter, and then find the relative center of the shaft and the tile with the arc surface of the tile body as the reference, and adjust the gap between the tile shaft and the cylindrical shaft. ③ Based on the original installation records of the bearing housing recess and shaft seal clearance, adjust the center of the shaft recess by grinding the bearing bush shims. When grinding the bushing and adjusting the shims, the contact area should be greater than 75% and the contact surface should be uniform. C. Replacement of thrust bearings ① Remove the old thrust bearings, clean and repair the thrust disc; ② Measure the deflection value of the thrust plate, and determine the thickness of the thrust pad on the working face based on the axial displacement value, relative expansion value, and the value derived from the installation K value; ③ First, perform individual measurement and grinding on the working and non-working tiles to ensure that the thickness difference between the tiles is less than 0.02mm; then install the front and rear thrust tiles and perform disc rotor grinding. When each thrust tile is in contact with uniform force and the contact area reaches more than 75%, adjust the adjusting shims on the non-working surface according to the required thrust clearance. D. Find the center using the backrest wheels. ① Using the turbine rotor as a reference, adjust the generator or gearbox by moving the generator bearing housing, gearbox, or increasing or decreasing the thickness of the bearing housing shims to adjust the outer circle and opening deviation of the back wheel within the required range. ② After the shaft center alignment is completed, install the back-to-back wheel coupling and use the suspended shaft method to check the rotor concentricity deviation. E. Reinstall the accelerator and windshield. ① Scrape the tips of the oil baffle and windshield, and install and restore the oil baffle and windshield according to the design gap to keep the oil return channel of the oil baffle unobstructed; ② For oil baffles that rely on gravity for sealing, the sealant on the mating surfaces should be uniform and maintain a thickness of 0.2mm-0.3mm; the gaps around the windshields should be uniform. F. Turning and testing ① After the unit has been overhauled, start the lubricating oil pump and slowly open the outlet valve or overflow valve to keep the oil pressure within the specified range, and inject oil into the system to raise its temperature. ② Observe the oil return volume of each bearing housing and adjust the oil volume by adding a throttling orifice plate so that the height of the return oil level is 1 / 4-2 / 3 of the pipe cross-section; the oil return volume of the thrust bearing is controlled by a regulating valve. ③ Start the turning gear. When the oil temperature reaches the operating requirements, recheck and adjust the system lubricating oil pressure and the return oil height of the return oil pipeline; check the turning gear current and compare it with the normal value, and listen for any abnormal noises inside the cylinder. ④ Through a low oil pressure interlock test, the interlock performance of the oil pumps should be fully tested to ensure that it meets the requirements. At the same time, the oil quantity and oil pressure of each oil pump should be adjusted to the design range.

[0011] When the cylinder temperature is below 120°C, the oil pump can be stopped and the bearing housing can be opened for bearing maintenance. After the bearing housing is opened, the inside of the inlet and return oil pipes should be cleaned and the oil ports temporarily sealed. Then, the quality of the lubricating oil should be tested, and the main oil tank and inlet and return oil pipes should be flushed and cleaned, and the system filter screen should be replaced.

[0012] Before reinstalling the bearing bush and oil baffle, thoroughly clean the bearing housing and the inside of the oil inlet pipe, and use dough to completely remove the internal oil stains and other impurities before reinstallation.

[0013] When aligning the shaft system, two rotors should be rotated simultaneously to measure the corresponding positions.

[0014] When a bearing burnout occurs, the first step is to rotate the main shaft using a turning gear or other methods to prevent bending. Then, compare the turning current or torque before and after the incident. If there is no significant change in the turning current or torque, it can be preliminarily determined that the internal cylinder wear damage is relatively minor. Next, retrieve historical shaft vibration, lubrication temperature, lubricating oil pressure, return oil temperature, axial displacement, relative expansion, and unit coasting time curves for each bearing through the DCS to further analyze the damage to the unit's shaft system and the degree of dynamic and static wear. Finally, review the unit's design documents and installation data to understand the condition of each bearing. Data from bearing top clearance, bridge gauge records, oil baffle clearance, steam seal clearance, blade tip clearance, and K-value extraction, combined with disassembly and inspection data of each bearing, are used to compare the existing clearance at the top of each bearing, the actual clearance of the oil baffle, the generator windshield clearance, the stator and rotor air clearance, the measured clearance of the shaft end steam seal, and the degree of shaft diameter damage. The changes in the lower bearing wear thickness affecting the shaft center elevation are then comprehensively calculated. Simultaneously, considering the design clearance of the steam seal block, the expansion clearance of the heated air baffle, and the changes in turning gear current, the impact of bearing wear on the internal radial dynamic and static clearances of the unit is calculated and determined. Through changes in axial displacement and relative expansion, combined with the turbine K-value extraction value, the impact of thrust bearing wear on the internal axial dynamic and static rubbing of the unit is calculated, including: Vibration of each bearing shaft: reflects the healthy operating condition of the shaft system; Black gold temperature: Based on the temperature rise value controlled by the manufacturer's bearing bush, it reflects the degree of melting and damage of the black gold; Lubricating oil pressure: Based on the time of abnormal oil pressure, combined with vibration and temperature rise, we can understand in advance the time of oil film failure and its impact; Oil return temperature: Based on the oil return temperature rise of the bearing bush combined with the temperature rise of the black metal, the degree of bearing bush damage can be judged in advance by two indicators; Axial displacement: Based on the displacement value combined with vibration and thrust bearing temperature, determine the damage condition of the thrust bearing; Relative expansion: Based on the expansion difference value combined with the unit's vibration value and axial displacement value, understand the axial dynamic and static friction state of the unit; Turning gear current: Analyze the degree of dynamic and static wear based on the changes in turning gear current; Coasting time: The shortening of coasting time serves as evidence of the wear condition of the rotor and bearings; If two or more of the above analytical data show abnormalities simultaneously, the unit must not be restarted and the bearings must be disassembled and inspected.

[0015] The specific calculation method is as follows: ① Record the measurement deviation value using bridge gauges and calculate the center settlement value A of the axle diameter; ② The measured bearing top clearance minus the designed or installed top clearance equals the shaft diameter center settlement value B; ③ The measured oil baffle clearance and windshield clearance minus the design or installation clearance equals the shaft diameter center settlement value C; ④ Calculate the shaft diameter center settlement value D by using the change value of the clearance between the front and rear shaft seal ends; The above three calculated shaft diameter settlement values ​​B, C, and D are used to corroborate value A. The four final values ​​should be basically consistent. Based on the drawings and installation records, the bottom clearance and relief clearance of the shaft seal block were determined. Shaft seal clearance + relief clearance = E value; Based on the drawings and installation records, the gap between the top and bottom of the blade peak was found. Combined with the thermal deformation characteristics of the baffle, the gap value + (0.5-1mm) = F value. The rotor axial displacement G is calculated by combining the derived value of K with the axial displacement and relative expansion value.

[0016] The above calculations show that: ① When AE = negative and AF = negative, combined with the maximum value of shaft vibration and the small deviation of turning current, it can be comprehensively analyzed that there is no radial friction damage inside the cylinder or it is a minor rubbing.

[0017] ② When GK is negative, combined with the maximum value of shaft vibration and the small deviation of turning current, it can be comprehensively analyzed that there is no axial friction damage inside the cylinder or it is a minor rubbing.

[0018] Based on the conclusions, a construction plan for repairing the bearing bushes, oil baffles, and windshields can be formulated to restore the relative centering of the shaft system. When individual values ​​show a slight positive value or individual parameters are abnormal, multiple parameters should be considered to carefully analyze and investigate the cause and formulate reliable maintenance measures.

[0019] Following the burnout of the original bearing bushes, due to a lack of experience and precedents for non-cylinder-opening maintenance, power plants typically opt for a major overhaul (cylinder cover removal) approach for visual inspection and treatment of the defect. This method requires a complete disassembly and overhaul of the turbine generator unit. A normal overhaul of a 12MW turbine generator unit usually takes 15-18 days, while an accident overhaul typically takes ≥20 days. However, this method, by analyzing historical DCS trends, unit design, and installation data, combined with on-site inspection and measurement of each bearing bush, uses scientific analysis and data comparison to accurately determine the shaft damage and health status. This allows for the development of a rapid, non-cylinder-opening repair plan, preventing the accident's impact from escalating. This method can control the repair period within 4-7 days, eliminating bearing burnout defects in the shortest time and at the lowest cost, minimizing accident losses.

Claims

1. A construction method for rapidly repairing burnt-out bearings of steam turbine generator sets, characterized in that, Includes the following steps: First, ensure there is no mechanical wear or abrasion damage inside the unit, then proceed with construction preparations. The specific calculation method is as follows: ① Record the measurement deviation value using bridge gauges and calculate the center settlement value A of the axle diameter; ② The measured bearing top clearance minus the designed or installed top clearance equals the shaft diameter center settlement value B; ③ The measured oil baffle clearance and windshield clearance minus the design or installation clearance equals the shaft diameter center settlement value C; ④ Calculate the shaft diameter center settlement value D by using the change value of the clearance between the front and rear shaft seal ends; The above three calculated shaft diameter settlement values ​​(B, C, and D) are used to corroborate value A. Ultimately, the four values ​​should be basically consistent. By referring to the drawings and installation records, the bottom clearance and relief clearance of the shaft seal block were found. Shaft seal clearance + relief clearance = E value; Based on the drawings and installation records, the gap between the top and bottom of the blade peak was found. Combined with the thermal deformation characteristics of the baffle, the gap value + (0.5-1mm) = F value. The rotor axial displacement G is calculated by combining the derived value of K with the axial displacement and relative expansion value. The above calculations show that: ① When AE = negative and AF = negative, combined with the maximum value of shaft vibration and the small deviation of turning current, it can be comprehensively analyzed that there is no radial friction damage inside the cylinder or it is a minor rubbing. ② When GK=negative, combined with the maximum value of shaft vibration and the small deviation of turning current, it can be comprehensively analyzed that there is no axial friction damage inside the cylinder or it is a minor rubbing. A. Construction Preparation ① Prepare the lifting machinery, tools and protective equipment required for construction and high-altitude operations, and conduct insulation tests on electrical tools; ② Remove and move the top covers of each bearing away, temporarily seal the inlet and outlet oil passages of the main oil pump and the inlet and outlet oil passages of the bearing housing, and check whether there are any debris or black metal fragments at the bottom of the bearing box. ③ Disassemble the upper half of each bearing shell, measure the top clearance and record it. At the same time, measure the clearance of the oil baffle, wind baffle and end shaft seal, and calculate the shaft system elevation and axial displacement based on the measurement records and the original installation records. B. Supports tile replacement ① Remove the old tiles, clean and repair the shaft diameter; ② Measure the shaft diameter and cylindricality, adjust and replace or recast and repair the spare tile shaft according to the shaft diameter, and then find the relative center of the shaft and the tile with the arc surface of the tile body as the reference, and adjust the gap between the tile shaft and the cylindrical shaft. ③ Based on the original installation records of the bearing housing recess and shaft seal clearance, adjust the center of the shaft recess by grinding the bearing bush shims. When grinding the bushing and adjusting the shims, the contact area should be greater than 75% and the contact surface should be uniform. C. Replacement of thrust bearings ① Remove the old thrust bearings, clean and repair the thrust disc; ② Measure the deflection value of the thrust plate, and determine the thickness of the thrust pad on the working face based on the axial displacement value, relative expansion value, and the value derived from the installation K value; ③ First, perform individual measurement and grinding on the working and non-working tiles to ensure that the thickness difference between the tiles is less than 0.02mm; then install the front and rear thrust tiles and perform disc rotor grinding. When each thrust tile is in contact with uniform force and the contact area reaches more than 75%, adjust the adjusting shims on the non-working surface according to the required thrust clearance. D. Find the center using the backrest wheels. ① Using the turbine rotor as a reference, adjust the generator or gearbox by moving the generator bearing housing, gearbox, or increasing or decreasing the thickness of the bearing housing shims to adjust the outer circle and opening deviation of the back wheel within the required range. ② After the shaft center alignment is completed, install the back-to-back wheel coupling and use the suspended shaft method to check the rotor concentricity deviation. E. Reinstall the accelerator and windshield. ① Scrape the tips of the oil baffle and windshield, and install and restore the oil baffle and windshield according to the design gap to keep the oil return channel of the oil baffle unobstructed; ② For oil baffles that rely on gravity for sealing, the sealant on the mating surfaces should be uniform and maintain a thickness of 0.2mm-0.3mm; the gaps around the windshields should be uniform. F. Turning and testing ① After the unit has been overhauled, start the lubricating oil pump and slowly open the outlet valve or overflow valve to keep the oil pressure within the specified range, and inject oil into the system to raise its temperature. ② Observe the oil return volume of each bearing housing and adjust the oil volume by adding a throttling orifice plate so that the height of the return oil level is 1 / 4-2 / 3 of the pipe cross-section; the oil return volume of the thrust bearing is controlled by a regulating valve. ③ Start the turning gear. When the oil temperature reaches the operating requirements, recheck and adjust the system lubricating oil pressure and the return oil height of the return oil pipeline; check the turning gear current and compare it with the normal value, and listen for any abnormal noises inside the cylinder. ④ Through a low oil pressure interlock test, the interlock performance of the oil pumps should be fully tested to ensure that it meets the requirements. At the same time, the oil quantity and oil pressure of each oil pump should be adjusted to the design range.

2. The construction method for rapidly repairing burnt-out bearings of a steam turbine generator set according to claim 1, characterized in that: When the cylinder temperature is below 120°C, the oil pump can be stopped and the bearing housing can be opened for bearing maintenance. After the bearing housing is opened, the inside of the inlet and return oil pipes should be cleaned and the oil ports temporarily sealed. Then, the quality of the lubricating oil should be tested, and the main oil tank and inlet and return oil pipes should be flushed and cleaned, and the system filter screen should be replaced.

3. The construction method for rapidly repairing burnt-out bearings of a steam turbine generator set according to claim 1, characterized in that: Before reinstalling the bearing bush and oil baffle, thoroughly clean the bearing housing and the inside of the oil inlet pipe, and use dough to completely remove the internal oil stains and other impurities before reinstallation.

4. The construction method for rapidly repairing burnt-out bearings of a steam turbine generator set according to claim 1, characterized in that: When aligning the shaft system, two rotors should be rotated simultaneously to measure the corresponding positions.