In the cooling water system of the generator stator of a power plant, the CZ80-160 centrifugal pump plays a vital role. It is responsible for delivering cooling water stably and efficiently, ensuring the normal operating temperature of the generator stator, thereby ensuring the safety and stability of the entire power plant generator set. As one of the core components of the centrifugal pump, the normal operation of the pump shaft is directly related to the performance of the centrifugal pump and even the entire cooling water system. Therefore, the protection of the pump shaft of the CZ80-160 centrifugal pump is crucial. The following will start with the analysis of the common causes of pump shaft damage and discuss the protection measures for the pump shaft of the pump in the cooling water system of the generator stator of the power plant.

I. Common causes of damage to the pump shaft of the CZ80-160 centrifugal pump

(I) Excessive vibration

1. Mechanical reasons

- In the cooling water system of the generator stator of a power plant, the CZ80-160 centrifugal pump has been running for a long time, and the pump shaft may be unbalanced due to bearing wear. For example, bearing wear may be due to long-term excessive load or lack of sufficient lubrication. As the bearing wears, the concentricity of the pump shaft will gradually change, and abnormal vibration will occur during operation.

- Insufficient machining accuracy of the pump shaft itself or deviation during installation can also cause excessive vibration. For example, if the gap between the shaft and the bearing is not set properly when installing the pump shaft, friction may occur during operation, causing vibration.

2. Fluid dynamics factors

- In the cooling water system, the flow state of water affects the vibration of the pump shaft. If the inlet pressure of the cooling water is unstable or there is throttling in the inlet pipeline, it will cause hydraulic imbalance in the pump. This hydraulic imbalance will produce irregular fluid excitation force, acting on the pump shaft and causing vibration.

(II) Unbalance

1. Impeller factors

- The impeller is an important component connected to the pump shaft in the centrifugal pump. During the operation of the generator stator cooling water system, the impeller may have uneven mass distribution due to long-term wear. For example, the impeller blades may be corroded or washed by impurities carried in the cooling water, causing the center of gravity of the impeller to shift. When the impeller is installed on the pump shaft, the pump shaft will bend and vibrate due to the unbalanced force.

2. Adhesion of foreign matter

- Cooling water may carry some tiny solid particles during the circulation process. If these particles are not effectively filtered at the inlet of the water pump, they may adhere to the pump shaft or impeller. As the number of attached particles increases, the dynamic balance of the pump shaft and the impeller will be destroyed, causing unbalanced movement of the pump shaft.

(III) Interruption of pumped liquid flow

1. Valve failure

- In the pipeline of the cooling water system, the valve plays a role in controlling the direction and flow of water flow. If the valve fails, such as the check valve fails and flows backward, or the stop valve is not fully opened, the flow of cooling water in the pump will be interrupted. Sudden flow changes or interruptions will cause huge axial and bending forces on the pump shaft.

2. Pipeline blockage

- Impurities in the cooling water may gradually settle in the pipeline, causing pipeline blockage. When blockage occurs, the pump shaft will be subjected to higher pressure on the one hand, and on the other hand, it may produce abnormal stress conditions due to uneven water flow, increasing the risk of pump shaft damage.

II. Protection measures for the pump shaft of CZ80-160 centrifugal pump

(I) Protection against excessive vibration

1. Accurate assembly and commissioning before installation

When installing the CZ80-160 centrifugal pump, accurate assembly of the pump shaft and impeller and other components is required. Use high-precision measuring tools to ensure that key parameters such as the concentricity of the pump shaft and the verticality of the impeller and the pump shaft are within the specified range. At the same time, after the installation is completed, a comprehensive dynamic commissioning should be carried out to detect the vibration of the pump under different working conditions and adjust any deviations found in time.

2. Install vibration monitoring device

- Advanced vibration sensors are installed on the CZ80-160 centrifugal pump in the stator cooling water system of the power plant generator. These sensors can monitor the vibration velocity, acceleration and displacement of the pump shaft in real time. By comparing with the set threshold, once abnormal vibration is found, timely measures can be taken, such as shutdown inspection or on-site adjustment. At the same time, vibration data can also be recorded to analyze the long-term trend of pump shaft vibration in order to predict possible problems in advance.

3. Optimize fluid dynamics design

- During the design phase of the cooling water system, ensure the reasonable layout of the pipeline to avoid throttling. Computational fluid dynamics (CFD) can be used to simulate and analyze the flow state of cooling water in the pump, optimize the shape and hydraulic conditions of the inlet pipeline, and ensure that the fluid excitation force on the pump shaft is uniform and stable. In addition, the inlet filter of the cooling water system should be cleaned regularly according to the actual operating conditions to prevent hydraulic imbalance caused by blockage of debris.

(II) Protection against imbalance

1. Inspection and maintenance of impellers

- Regularly (for example, quarterly or half-yearly) inspect the impeller of the CZ80-160 centrifugal pump. Check the wear of the impeller blades and use non-destructive testing technology (such as ultrasonic testing or magnetic particle testing) to detect whether there are defects inside the blades. For blades with severe wear, repair or replace them in time. At the same time, after the impeller is reinstalled on the pump shaft, a dynamic balance test should be performed to ensure that the center of gravity of the impeller is in the correct position.

2. Strengthen water quality filtration and monitoring

- Multi-stage filtration devices are installed at the inlet and outlet of cooling water. The coarse filtration device at the inlet can intercept larger impurity particles, and the fine filtration device at the outlet can further remove tiny solid particles. At the same time, the water quality of cooling water should be monitored regularly, and the parameters of the filtration device should be adjusted in time according to the water quality to ensure that the water quality of cooling water meets the system requirements and prevent foreign matter adhesion caused by poor water quality.

(III) Protection against interruption of pumped liquid flow

1. Regular inspection and maintenance of valves

- Regularly (monthly or semi-annually) inspect various valves (such as stop valves, check valves, regulating valves, etc.) in the cooling water system. Check the sealing, operational flexibility and control mechanism of the valve. For aging valves or valves prone to failure, they should be replaced or repaired in time. At the same time, auxiliary control and monitoring devices, such as electric actuators and position sensors, can be installed at the valves to monitor the status of the valves in real time and remotely control the opening and closing of the valves.

2. Management and maintenance of pipelines

- Regularly (annually) conduct a comprehensive inspection of the pipelines of the cooling water system, and use equipment such as pipeline endoscopes to check whether there is any blockage inside the pipeline. At the same time, a spare pipeline is set up in the cooling water system and equipped with a corresponding switching device. Once the main pipeline is blocked, it can be quickly switched to the spare pipeline to ensure the normal supply of cooling water and avoid damage to the pump shaft due to sudden changes in flow.

In the stator cooling water system of the power plant generator, the protection of the pump shaft of the CZ80-160 centrifugal pump needs to start from multiple aspects, comprehensively consider various possible causes of pump shaft damage, and take corresponding and effective protection measures. Only in this way can the CZ80-160 centrifugal pump be ensured to operate stably and efficiently in the cooling water system, and the safety and normal power generation of the generator set be guaranteed.

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