Pumps are widely used in thermal power plants and have a significant impact on the safety and economics of power plants. The reasons of power plant water pumps can be divided into three categories: mechanical, hydraulic and electrical.
1. The mechanical reasons for the failure of the power plant water pump mainly include the following aspects. These causes can cause strong vibrations of the pump and a lot of noise.
(1) The mass imbalance of the rotating parts of the motor and the water pump is divided into the initial imbalance and the imbalance during operation. In the initial state, the quality distribution is uneven due to the failure of the manufacturing process, which affects the balance of the pump. During the operation, the medium flowing in the pump will cause certain corrosion and wear to the pump body, and the impurities contained in the medium cause the pump body. Fouling can also cause uneven pump mass distribution, which affects the balance of the pump. There is another situation in the operation of the pump that will cause the pump to malfunction. That is, the parts on the rotor are detached or other matter enters the pump. Such failure is a sudden imbalance, which is manifested by a sudden increase in vibration value. Then it will lower and stabilize at a normal vibration point .
(2) The rotor is misaligned, that is, the shaft of the pump is not in line with the shaft of the motor, and the misaligned coupling and the misaligned bearing.
(3) Resonance occurs when the natural frequency of the rotor and the frequency at the same speed. In order to reduce the resonance, the basic structure of the pump is generally designed to be large because the fundamental vibration is inversely proportional to the overall mass of the pump. When the foundation is loose, it will cause a large vibration phenomenon. The looseness of the foundation will cause the natural frequency of the system to change, and it is more likely to generate resonance. This situation is very harmful to the safety of the pump.
2. The vibration of the pump hydraulics is cavitation and surge.
Cavitation is when the pressure of the liquid in the pump of the condensate pump drops to a level equal to or lower than the saturation pressure at the liquid temperature at that time, bubbles appear in the liquid, and when the bubble breaks, a large pressure is generated, so that The pump caused a lot of damage. Surge is a situation in which the flow in the tube is unstable and the flow changes periodically, under such condition there is great vibration and noise.
3. Electric of the pump
The imbalance of the internal magnetic field of the motor and the failure of the electrical system operation are the causes of large vibration and strong noise.
1. High lift and large capacity
Since the design of the power plant site requires a large outlet pressure, a high-lift multistage pump is required. The single stage of the multistage pump is 1.5Mpa(1500m), capacity is 1100m³/h which can completed meet its requirements.
The temperature of medium has a large variation range which will cause cavitation. Therefore, for the material of the flow-through component, the way of sealing, the structure of the pump body needs to have higher requirements. N/NB series condensate pumps meet the requirements.
3. Noise, vibration and stability
With balancing plate and balancing ring, the conventional pump could easily wear out after long term operation. It will not only cause noise and vibration but also frequent replacement of the plate and ring. So it has to replace the balacing plate and ring when using conventional multistage pump. Rotor parts with symmetrical impellers of self balancing multistage boiler feed pump can counteract the axial force, so that balancing plate and ring would not be needed. Therefore, It has reduced the cost and time.