Pump inlet velocity, impact on the system

Pump inlet velocity, impact on the system

The principle of setting the diameter of the outlet and inlet of the centrifugal pump: Generally, the outlet diameter is selected according to the economic flow rate, and the outlet diameter is determined by the flow rate. When the pipe diameter is less than 250, it is 1~1.2m/s, and when the pipe diameter is 250~1000, it is 1.2~1.6. m/s. Technically, the maximum speed of water flow should not exceed 2.5~3.0m/s, and the minimum speed should not be less than 0.6m/s (to prevent deposition)

Small inlet flow rate, advantages

1. It is beneficial to increase the NPSHA of the cavitation allowance of the device, and the pump is not easy to cavitation;

2. The scouring of the pipeline is small, especially the 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 rate, the pipe diameter needs to be large and the pipeline cost is high;

2. For some easy-to-sediment media, if the flow rate is too small, it 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 Yuhu Jun in the background whether the pipe diameter of the inlet and outlet pipes of the centrifugal pump must be larger than the inlet and outlet diameter of the pump itself. This problem requires specific analysis.


For most pumps, the purpose of increasing the diameter of the inlet and outlet pipes is to reduce the flow rate of the fluid in the pipes, so as to reduce the resistance drop of the pipes and ultimately reduce the power consumption of the pump. However, increasing the pipe diameter is to increase the pipeline investment cost. At a cost, in this way, for the pipeline with a long-distance pump outlet, it can be considered to increase the pipe diameter appropriately to reduce the resistance drop, while for short-distance pipelines, it is not necessary to consider; and for the material conveyed by the pump inlet is liquefied gas, the temperature is close to For materials with boiling point and low suction position that are easy to cavitation, consider increasing the diameter of the pump inlet pipe to reduce resistance drop and avoid cavitation of the pump.

Post time: Nov-08-2020

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