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If a centrifugal cryopump generates noise and vibration during operation, accompanied by a decrease in flow rate, head, and efficiency, and sometimes even stops working, inspections often reveal pitting or honeycombing damage near the inlet edge of the blades; in severe cases, this phenomenon occurs across the entire blade, and the blade may even be punctured. This is damage caused by cavitation. Reasons for cavitation in centrifugal cryopumps: The pump does work on the liquid through its rotating impeller, increasing the liquid’s energy. During the interaction, the velocity and pressure of the liquid change. Generally, the inlet of the impeller in a centrifugal cryopump is the point with the lowest pressure. If the pressure in this area is equal to or lower than the vaporization pressure of the liquid at that temperature, steam and gases dissolved in the liquid will escape from it in large quantities, forming many small bubbles composed of a mixture of steam and gases. As these small bubbles flow with the liquid to high-pressure areas, a pressure difference is created because the pressure inside the bubbles is at the vaporization pressure, while the pressure surrounding the bubbles is higher than that vaporization pressure. Under this pressure difference, the bubbles are compressed and burst, then re-condense. During the condensation process, liquid particles move rapidly from the surroundings toward the center of the bubble; at the moment of condensation, these particles collide with each other, generating very high local pressures. If these bubbles burst and condense near the metal surface, the liquid particles act like countless small projectiles, continuously striking the metal surface. Under continuous impacts with high pressure and frequency, the metal surface gradually deteriorates due to fatigue; this type of damage is commonly referred to as erosion. The bubbles formed also contain some reactive gases (such as oxygen), and the heat released during the condensation of these bubbles causes chemical corrosion of the metal. The combined effect of chemical corrosion and mechanical ablation further accelerates the rate of metal degradation; this phenomenon is known as cavitation damage. When cavitation begins to occur in a centrifugal cryopump, the area affected by cavitation is small, so it has no significant impact on the normal operation of the pump, nor is there any noticeable effect on its performance curve. But when cavitation reaches a certain level, a large number of bubbles are generated, which disrupt the normal flow of the liquid and can even cause the flow to stop, resulting in vibrations and noise ； At the same time, the pump’s flow rate, head, and efficiency decrease significantly, which is also clearly reflected on the pump performance curve. In severe cases, the pump cannot function. Compiled by Hangzhou Zede Pumps, this article states that in order to minimize cavitation as much as possible, the liquid should have a certain degree of subcooling before it enters the pump; meanwhile, the pump should be installed at a lower position so that there is a sufficient static head at the liquid inlet. In addition, attention should be paid to heat preservation to minimize heat loss. For more information, please visit the China Pump Industry Network.