First: The Inlet and Outlet Size of Pump and Pipe

Pump Inlet is generally larger than outlet, because of the low pressure of inlet , water density is small, flow is slow, in order to meet the water supply balance requirements and ensure that the entrance has a certain pressure head, to prevent cavitation, the inlet is larger. Fire Fighting Pump outlet flow is fast, with large flow of same diameter, so the inlet is larger than outlet. Outlet diameter large, inlet resistance, is conducive to pump inlet medium, export diameter is small, is conducive to maintaining the pump outlet pressure.

Centrifugal pump inlet and outlet pipe diameter than the pump itself is greater than the diameter of the import and export, this issue requires specific analysis of specific issues, for most pumps, the import and export pipeline diameter increases the purpose is to reduce the fluid in the pipeline Flow rate, in order to reduce the pipeline resistance drop, in order to ultimately reduce the power consumption of the pump, but increase the diameter is to increase the cost of pipeline investment cost, so that the pump outlet for long-distance pipeline can be considered appropriate to increase the diameter, Reduce the resistance drop, and for the short distance you can not consider; and for the pump inlet material is liquefied gas, the temperature close to the boiling point, the inlet position is relatively low and so easy to cavitation of the material, you should consider increasing the pump inlet Pipe diameter, in order to reduce the resistance drop, avoid pump cavitation.

Usually the suction pipe diameter of the pump is generally larger than the outlet diameter, according to the pipe diameter of different suction flow rate is also different. When the diameter is less than 250mm, it is 1~1.2m/s, when the diameter is 250~1000mm, 1.2~1.6m/s, technically, the maximum speed of water should not exceed 2.5~3.0m/s, the minimum speed should not be less than 0.6m/s (to prevent deposition).

Second: How to identify the inlet and outlet of the pump for which has been put into production?
Depending on the type of pump, they are so much, we list the following some, we welcome comments added:
1. the pump outlet pipe diameter is generally smaller than the inlet;
2. as viewed from the motor to the pump inlet is generally in the lower right portion of the pump head;
3. general export pressure gauge, check valve, and so on lead leaching;
4. if there is no installation, can be seen from the flange opening of the impeller is exported.
5. if the import and export of a pump is axial, one is radial, then the axis is the entrance, radial exit.
6. if the pump inlet and outlet are radial, then the direction from the motor side to the pump, the left hand side for the entrance, the right hand side for the export.
7. generally the pump manufacturers will mark on the pump steering pump, then the direction of the arrow is the outlet, on the contrary is the inlet.