Changsha Zoomlian Pump Industry, a multistage centrifugal pump manufacturer, explains what the Net Positive Suction Head (NPSH) of a multi-stage centrifugal pump means. The NPSH of a multi-stage centrifugal pump refers to the safety margin or allowance that prevents cavitation during the pump's operation. Cavitation occurs in a multi-stage centrifugal pump when the liquid in the impeller is subjected to excessive vacuum or the formation of cavitation bubbles, causing partial evaporation of the liquid and the occurrence of cavitation. Cavitation can damage the pump, reduce its performance, and lead to noise and vibration.
The main purpose of NPSH is to ensure that the multi-stage centrifugal pump is not affected by cavitation under normal operating conditions. NPSH is typically measured in specific units such as meters (m) or feet (ft). It represents the difference between the static pressure of the liquid from the pump inlet to the pump impeller and the liquid vapor pressure. If this difference is large enough, the liquid will not cavitate in the impeller.
Once the NPSH is calculated, a suitable multi-stage centrifugal pump can be selected or appropriate operating parameters can be determined based on specific application requirements to ensure the pump is free from cavitation effects. A reasonable NPSH margin can improve the reliability of the multi-stage centrifugal pump, extend its service life, and ensure the stable operation of the entire plant system.