The cause of vacuum pump cavitation

Cavitation corrosion is a kind of high-noise and destructive phenomenon often occurred in hydraulic machinery. In vacuum acquisition equipment, cavitation corrosion of water-ring vacuum pump is also known to all, and the damage to vacuum pump is a cumulative process, which is easy to cause impeller perforation.
The principle of its occurrence is: due to the action of liquid dynamics, when the partial pressure of the moving liquid drops to the vaporization pressure at this temperature, the liquid begins to vaporize and form bubble, bubble filled with liquid vapor and a small amount of dissolved gas in the liquid. When the bubble with the moving liquid reaches the area where the static pressure exceeds the critical pressure, the steam in the bubble will suddenly condense and burst the bubble. Because the pressure in the bubble is always lower than or close to the critical value, and the pressure of the external liquid is relatively large, so when the bubble bursts, the surrounding liquid rushes to the bubble center at a very high speed and forms the effect of high-frequency water hammer, generating high local stress and local temperature rise, and generating noise and vibration. Repeated processes of the formation and bursting of such bubbles will damage the surface of parts in this area. In addition, chemical and electrochemical corrosion of liquid and parts materials will eventually result in cavitation damage with spongy or honeycombed characteristics.
It is also shown that cavitation may occur even above the critical pressure. Because the pressure decreases, dissolved in the liquid air and other gas will be analyzed, at the same time, the liquid steam out, full of steam and gas liquid and bubble formation, the bubble in the movement parts surface easily produce and grew up, was taken away by liquid, where high pressure suddenly condensation and burst.
The critical pressure at which cavitation occurs varies with the properties of liquids, temperatures, and dissolved gases. For degassing normal temperature water, the saturated vapor pressure equivalent to that of the water temperature can be taken as the critical pressure value for the occurrence of bubble.

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