The setting principle of the diameter of the outlet and the inlet of the centrifugal pump: Generally, the outlet diameter is selected according to the economic flow rate, and the outlet diameter is determined according to the flow rate. When the pipe diameter is less than 250, it is 1 to 1.2m/s, and when the pipe diameter is 250 to 1000, it is 1.2 to 1.6 m/s. m/s, from a technical point of view, the maximum speed of the water flow should not exceed 2.5 ~ 3.0m/s, and the minimum speed should not be less than 0.6m/s (to prevent sedimentation).
The inlet flow rate is small, the advantages:
1. It is beneficial to improve the NPSHA of the device, and the pump is not easy to cavitate;
2. Small flushing of pipelines, especially for medium containing particles;
3. It is not easy to generate static electricity;
4. The pressure drop of the inlet filter is small;
5. In the same section, the medium flows evenly and the hydraulic loss is small.
Inlet flow rate is small, disadvantages:
1. Under the same flow, the pipe diameter needs to be large, and the pipeline cost is high;
2. For some easy-to-precipitate media, the flow rate is too small, which is easy to cause sedimentation blockage;
3. The impeller inlet is large, the diameter of the mouth ring is large, and the leakage is large.
The water inlet of the pump is generally larger than the outlet diameter. Someone asked Yuhujun in the background whether the diameter of the inlet and outlet pipes of the centrifugal pump must be larger than the diameter of the inlet and outlet of the pump itself. This question needs to be analyzed in detail.
For most pumps, the purpose of increasing the diameter of the inlet and outlet pipelines is to reduce the flow rate of the fluid in the pipeline, so as to reduce the resistance drop of the pipeline, and finally reduce the power consumption of the pump. However, increasing the diameter of the pipeline is to increase the investment cost of the pipeline. In this way, for the pipeline with a long-distance pump outlet, it can be considered to appropriately increase the pipe diameter to reduce the resistance drop, while for the short-distance pipeline, it can be ignored; for the material transported by the pump inlet is liquefied gas, the temperature is close to For materials that are prone to cavitation, such as those with a boiling point and a relatively low suction position, consideration should be given to increasing the diameter of the pump inlet pipe to reduce the resistance drop and prevent the pump from cavitation.
