Abstract: With the development of social economy and the progress of science and technology, the industrial development and power production situation are good. In the operation of thermal power plants, steam turbines have been used for power generation, and the vibration problem of turbine bearings is crucial. Based on this, this article takes the vibration of steam turbine bearings as the research object, analyzes the causes of steam turbine bearing vibration, and elaborates on effective measures to deal with steam turbine bearing vibration from the aspects of unit expansion and temperature improvement, generator current and regulating valve control mode, shutdown inspection situation, etc., in order to ensure the operation quality of steam turbine, improve the production efficiency of thermal power plants, and achieve economic and social benefits growth of enterprises.
Keywords: steam turbine; Bearing vibration; Handling measures
0 Introduction
The vibration of steam turbine bearings has always been a parameter for the healthy operation of steam turbine units. In the operation of large steam turbine units, corresponding bearings and bearings are equipped to monitor the operation of the steam turbine. The vibration parameters of steam turbine bearings directly affect the technical level of operators and the operational health of steam turbine equipment. Strengthening the protection of steam turbine bearing vibration can ensure the stability and safety of the equipment. As the steam turbine cannot be shut down during operation, if the vibration of steam turbine bearings rises during operation, operators need to analyze the cause based on the actual situation and find solutions to the problem.
1 Analysis of the causes of large vibration in turbine bushing
1.1 Loose components and unit expansion
The turbine bearing plays a supporting role on the rotor in the turbine, and a large part of the components in the turbine are operating at high temperatures. When temperature control is abnormal, it can cause uneven expansion of the components in the turbine, causing deformation of the turbine rotor, increasing the amplitude of the unit, and even causing component collisions. During the operation of the steam turbine, various vibrations can cause components to loosen, making it difficult to effectively constrain the components in the turbine, resulting in an increase in vibration amplitude. Especially when the turbine rotor becomes loose, centrifugal force will be generated during high-speed rotation of the rotor, causing the turbine to fail to meet balance requirements and increase the amplitude of the bearing.
1.2 Blade deformation and fracture
During the operation of the steam turbine, a large number of blades are in a high-temperature and high-pressure working state, and the working environment is harsh. After a long period of operation, the blades of the steam turbine will be corroded by water vapor, deformed or even broken. This situation will increase the vibration of the bearing in two aspects. One is the friction of high-temperature and high-pressure gas on the faulty part, which can cause irregular vibration of the rotor and increase the vibration of the bearing. The second is that after the blade deforms or even breaks, it will not meet the force balance requirements of the rotor during the operation of the steam turbine, resulting in significant and severe vibration of the rotor. This situation needs to be avoided as much as possible, and special attention should be paid during unit inspections.
1.3 rotor manufacturing issues
In the manufacturing of steam turbine rotors, due to the involvement of multiple structures, various errors in assembly and component production will gradually accumulate, resulting in uneven distribution of rotor mass. When the steam turbine is put into operation, this uneven distribution of mass will cause vibration of the rotor. Usually, this phenomenon is not obvious when the rotor is not heated. However, when the rotor is heated, these uneven parts will undergo varying degrees of deformation, and significant vibrations will be generated during rotor rotation. These vibrations will also affect the bearings, leading to a decrease in rotor stability, exacerbating the vibration of the turbine bearings, and forming a vicious cycle.
1.4 Various temperatures do not meet the requirements
During the operation of the steam turbine, it is necessary to control the temperature of each part to ensure that the vibration is within a safe range. The temperature that needs to be controlled includes the following aspects: (1) lubricating oil temperature. Lubricating oil requires appropriate viscosity to play a lubricating role. When the temperature of the lubricating oil is too high, its viscosity will be reduced, and effective lubrication cannot be achieved. Oil film oscillation phenomenon will occur. If the oil temperature is too low, it will cause increased friction and vibration. Generally, the appropriate temperature is 25-60 ℃. (2) Shaft seal temperature. The temperature of the shaft seal will affect the elevation of the bearing seat and the clearance of the steam seal, causing vibration and also affecting the temperature of the lubricating oil. (3) Exhaust temperature. The exhaust temperature can cause expansion of the unit.
2 Effective measures to deal with large vibration of turbine bushing
2.1 Unit Expansion and Temperature Improvement Measures
The expansion of the unit is caused by various reasons, which can be divided into sliding pin system failure and unqualified temperature control from the perspective of formation reasons. Therefore, to avoid unit expansion, it is necessary to consider these aspects, such as regularly inspecting the sliding pin system, and promptly repairing and replacing facilities when problems are found. Temperature improvement needs to be approached from multiple aspects, including uniform preheating before the operation of the steam turbine unit and insulation of the cylinder body. In addition, it is necessary to monitor the lubricating oil temperature, shaft seal temperature, and exhaust temperature. When it is found that the temperature does not meet the working requirements, corresponding measures should be taken in a timely manner. This requirement can be met by constructing an automatic temperature control system.
2.2 Generator current and gate control method
When the turbine bearings vibrate, the current of the generator will have a certain impact on the vibration, mainly occurring on the side bearings of the generator. This vibration exists from the beginning of the turbine operation and is not temporary or sudden. Therefore, this hidden danger can be ruled out based on the actual situation.
Can turbine operators control the turbine control valve? If the problem still exists after adjustment, a handheld vibration instrument can be used to test the vibration of the turbine bearing. The vibration conditions of each part and direction need to be investigated, and the vibration parameter values of the turbine bearing need to be adjusted. Then, it will be found that the on-site vibration of the turbine bearing has little effect, and testing will start in the vertical and horizontal directions. When the temperature of the turbine bearing is within a certain range, it can be determined that this may be a problem with the measuring point. At this time, the operator can contact the thermal control personnel and start repairing.
2.3 Shutdown inspection? situation
If the vibration of the turbine bearing still exists, and all tests have been conducted the same, it is recommended to stop the turbine for inspection. After confirming the shutdown, the probe for the turbine bearing vibration should be removed first. If the probe for the turbine bearing vibration is intact and undamaged, at the same time in the turning state, the numerical value of the turbine bearing vibration follows a pattern, with a peak value occurring every twenty seconds. After analyzing this phenomenon, it was found that there is a high point on the main shaft of the steam turbine bearing vibration. The front bearing box of the steam turbine can be lifted and carefully inspected. If there are metal attachments inside, it indicates that the steam turbine has been operating for a long time. With changes in temperature and environment, there is slight friction between the oil gear comb and the steam turbine shaft. When the steam turbine is rotating at high speed and under high temperature friction, the comb will adhere to the steam turbine shaft, forming a high point. When turning, it causes the vibration of the turbine bearing to exhibit a regular fluctuation pattern, which is actually normal operation. Simply find the cause.
3 Summary
In summary, after comprehensive research and analysis, several factors affecting the vibration of turbine bearings have been identified. Through effective elimination methods, Z has been effectively addressed, achieving safe and stable production for the enterprise, resolving the existence of faults, and achieving economic growth.
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