Cavitation phenomenon Cavitation occurs when the inlet pressure of the pump is lower than the saturated vapor pressure of the liquid, causing the liquid to vaporize and form bubbles. The bubbles rupture in the high-pressure zone, generating impact force and damaging the impeller and pump casing. Cavitation not only reduces the performance of multi-stage pumps, but also generates noise and vibration. In severe cases, it can interrupt the liquid in the pump and prevent it from working properly.

The relationship between import pressure and cavitation

* Low import pressure:

When the import pressure approaches or falls below the saturated vapor pressure of the liquid, the risk of cavitation increases.

*High import pressure: Increasing the import pressure can reduce the risk of cavitation, as liquids are more difficult to vaporize. However, excessive import pressure may have adverse effects on the performance and service life of the pump. For example, when the inlet pressure of the pump is too high, the inlet valve of the pump may always be in the open state, resulting in inaccurate control of the total flow of the pump. The high inlet pressure may also affect the strength of the pump and shorten the service life of the power end components.

NPSH (Net Positive Inhalation Pressure Head) NPSHA (Net Positive Suction Head Available): Determined by the system, the higher the inlet pressure, the greater the NPSHA and the lower the risk of cavitation. NPSHR (required net positive suction head): determined by pump design, NPSHA must be greater than NPSHR, otherwise the risk of cavitation increases.

Influencing factors Liquid temperature:

*The higher the temperature, the higher the saturated vapor pressure, and the higher the risk of cavitation.

* Liquid properties: Different liquids have different saturated vapor pressures, which affect the risk of cavitation.

 *Pump speed: The higher the speed, the greater the NPSHR and the higher the risk of cavitation.

Preventive measures Increase import pressure:

*by increasing the pressure of the import pipeline or reducing the installation height of the pump. *Reduce liquid temperature: Reduce saturated vapor pressure and lower the risk of cavitation. *Optimize pump design: Improve impeller and inlet design to reduce NPSHR.

 Conclusion

The import pressure directly affects the cavitation performance, and increasing the import pressure can effectively reduce the risk of cavitation. During design and use, it is necessary to ensure that NPSHA is greater than NPSHR and take corresponding measures to prevent cavitation.