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Cause Analysis And Treatment Of Turbine Bearing Vibration In Large Thermal Power Plant

2018-10-24 17:02:56

Timken Sealed roll neck Bearings

Under the new normal economic environment, the number of large-scale thermal power plants is increasing and the installed capacity is increased. As an important equipment of large-scale thermal power plant, steam turbines have attracted much attention. Based on this, this paper mainly discusses the causes of large-scale thermal power plant turbine bearing vibration and treatment methods for reference.

0 Introduction

With the progress of the Times, industrial production and the daily life of the residents, the power supply has put forward new quality requirements. As an important equipment of large thermal power plant, the running state of steam turbine directly affects the normal supply of electric energy. In the actual work, the turbine fault, especially the bearing vibration, for the residents of daily production and life caused a serious impact, so in-depth analysis of turbine bearing vibration causes and treatment measures, has very important significance.

1 Turbine Bearing Vibration reasons

(1) Airflow excitation. In the large-scale thermal power plant bearing rotation, the phenomenon of airflow excitation is more common, resulting in increased vibration amplitude, including: 1 The turbine through the impeller and installed blades, the steam machinery can be converted to kinetic energy, steam on the blades of continuous impact, because the blade occupies a large area, Qiemo-grade blade is relatively long. The airflow reaches the tail end of the turbine, which is irregular and chaotic. At the same time, the blade has the expansion and contraction, the continuous vibration under the influence of the change, affecting the steam turbine flow through the channel of exciting vibration. 2) The airflow excitation and the traditional vibration mode are different, the main embodiment in the frequency is unstable, the airflow excitation frequency is seriously differentiated, if the steam turbine is in the low frequency state, its component value will increase, resulting in a large airflow difference, the operating parameters are constantly changing, the bearing vibration is large. (2) Thermal deformation of the rotor. With the increase of the installed capacity, the rotor length is also increasing, the rotor thermal deformation, resulting in abnormal vibration of the unit. Firstly, according to the vibration characteristics of the rotor thermal deformation unit, the vibration amplitude is closely related to the rotor running time. The longer the rotor runs, the more heat is generated and the temperature increases. Rotor operation is a regular, with the corresponding bearing standards. If the existing load is higher, it will affect the cooling state of the steam turbine, and the characteristics of the rotor's own metal will change. Especially when the unit starts to the fixed speed time, many steam turbine rotors will appear the thermal deformation. Second, the rotor continues to heat, the bending deformation will occur, showing a "rugged", in the operation of the channel unit operation is blocked, abnormal vibration occurs. In addition, the rotor material is different, its bearing internal stress is different, the heat release also varies. The rotor is heated, resulting in a constant increase in vibration, combined with heat emission frequency to form phase fluctuations, in this case, the rotor abnormal vibration more obvious. (3) Friction vibration. The main embodiment of vibration caused by friction vibration is: 1) affected by the rotor, the operation of the unit, the operating temperature is constantly rising, resulting in the formation of internal air pressure difference. If the pressure difference changes, the vibration signal will be different, affected by the linear impact, the main power frequency to create a new imbalance and occupy a dominant position, resulting in a vibration intensification phenomenon. 2) rotor and bearing friction process, the thermal power unit differentiation Unified interval Waveform, the number of differentiation, the waveform occurred "cutting top" phenomenon, resulting in increased vibration. 3) The continuous operation of the turbine, sudden stop, resulting in phase change, bearing critical value of the slow down, the original temperature is smaller. The sudden increase or decrease of temperature will cause the steam turbine to tremble, resulting in friction resulting in increased vibration. (4) Shaft seal supply steam pressure. In the turbine unit, the shaft seal is an important component, and its structure, material and shape also cause bearing vibration. Its material construction, generally through the high-pressure sealing piece to install. Unit operation, temperature rise can not be avoided, high-pressure seal is similar to hard components, the external structure is relatively fragile, improper use will occur softening problem. If the shaft seal heated deformation, it will make the shaft seal supply pressure to become larger, sealing film lodging, high-pressure end steam leakage, low-end air entry. With the change of load, the shaft seal shows different fluctuation, especially the pressure difference between the air supply pressure of the low pressure cylinder shaft seal and the internal steam, which leads to the increase of vibration. (5) Personnel operation is not standard. In the operation of steam turbine unit, the operator's operation is not standard, and it is also an important factor causing the bearing vibration. Some of the power plant operators think that their own experience, do not have to check the operation, so the actual implementation, will not strictly follow the steps to operate, even the wrong operation, resulting in oil interruption. Once the lubricating oil is interrupted, the bearing loses support power, and the steam turbine has serious friction, which causes the problem of vibration aggravation.

2 steam turbine bearing vibration big treatment measure

(1) Carefully check the phenomenon of air-induced vibration. First of all, the relevant operators to regularly check the steam turbine unit, detailed record of its operation status. Secondly, when checking, according to a certain time period, the vibration time and data found in the inspection are compared with the maximum and minimum values of the normal vibration range of the unit, and the curve is plotted. Finally, the detailed analysis has plotted the change curve, its clearance reflects the steam turbine set in the critical state of the rate of change, the relevant personnel through a separate way to adjust the pressure of different steam flow, in order to achieve the elimination of air excitation target. (2) Improve the rotor temperature control ability to prevent thermal deformation. The rotor temperature control measures mainly include, first of all, the staff strictly check the rotor running state, and the rotor system balance as the key to check the content, the appropriate adjustment of the rotation center, regulate the internal distribution of the unit, reduce the frequency of the bearing, effectively control the rotor temperature. Secondly, the relevant personnel regularly monitor the rotor temperature and eccentricity, reasonable set maintenance time, straight shaft product letter larger rotor, eliminate bending phenomenon. Finally, to strengthen the management unit shutdown, to ensure uniform heating effect of the rotor to prevent thermal bending of the rotor, using a variety of ways to reduce the number of static and dynamic friction rotor and frequency, in order to effectively prevent the occurrence of vibration phenomenon. (3) To improve the effectiveness of vibration detection work, to establish a sound system of shaft system protection. It is mainly achieved by optimizing the bearing material of the unit. First, the main types of bearings are unified management, simplifying the bearing system monitoring equipment installation process. Second, the actual operation, the staff need to repeatedly adjust the details of the experiment, on the one hand, standardize the implementation of the process method, while ensuring the rationality of the selection of the bearing material; the Shafting control Equipment section automatically senses its own operation, covering the operating speed, market and friction of the turbine. In a certain period of time, the vibration detection system can show the internal pressure of the shaft seal and analyze the relationship between temperature and pressure. High-pressure or high-temperature environment, the system automatically start the early warning procedures, set up a sound monitoring settings for the post-technical staff to implement the adjustment to facilitate. (4) Improve the performance of the shaft seal automatic device, strengthen monitoring and adjustment. Improve the performance of the shaft seal automatic device, combined with the clearance range of the shaft seal, to achieve continuous adjustment interval effect. After repeated experiments, the axial seal distance is adjusted properly, and pressure difference method is used to adjust the pressure difference. The use of high-performance filter equipment to prevent shaft seal occurs with water phenomenon. The condensate is separated from the steam to ensure that the shaft seal maintains normal pressure and effectively controls the steam quality. The vibration amplitude is effectively controlled by the management of the unit shaft seal device.

3 concluding remarks

To sum up, this paper analyzes the basic causes of vibration of large-scale thermal power plant turbine bearing, and puts forward some relevant solutions. In practice, it is necessary to understand the causes of large bearing vibration, improve the standard of inspection technology, enhance the performance of the shaft seal automatic device, reduce the vibration amplitude of the bearing of the turbine, in case of the vibration amplitude is too large, the bearing is damaged and other accidents.

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