1. Advantages of small inlet current speed
1) It is beneficial to increase NPSHA, so the pump is not easy to cavitation;
2) Small scour to pipeline, especially 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.
2. Disadvantages of small inlet current speed
1) Under the same flow rate, large pipe diameter and high pipeline cost are needed;
2) For some easy to precipitate media, the flow rate is too small, which is easy to cause deposition blockage;
3) The impeller has large inlet, which leads large ring diameter and large leakage.
The water inlet of the pump is generally larger than the outlet diameter, However, for most pumps, the purpose of increasing the diameter of the inlet and outlet pipes is to reduce the flow velocity of the fluid in the pipes, so as to reduce the resistance drop of the pipes, and ultimately reduce the power consumption of the pumps, but increasing the pipe diameter is at the cost of increasing the investment cost of the pipes. In this way, for the long-distance pipes with the pump outlet, the pipe diameter can be appropriately increased to reduce the resistance drop, while for the short-distance pipes it is unnecessary to consider; for the materials transported at the pump inlet, which are liquefied gas, temperature close to boiling point, low suction position and other materials prone to cavitation, it is necessary to consider increasing the diameter of the pump inlet pipe to reduce the resistance drop and avoid cavitation of the pump.