If centrifugal cryogenic pumps generate noise and vibration during operation, accompanied by reduced flow, lift, and efficiency, and sometimes fail to work, repairs often involve pitting or honeycomb damage near the entry edge of the blade, Serious when the entire leaves have this phenomenon, and even the leaves are penetrated, which is caused by cavitation damage.
Centrifugal cryogenic pump cavitation causes: pump rotating impeller to work on the liquid, so that liquid energy increases. During the interaction, the speed and pressure of the liquid change. Typically, the inlet of a centrifugal cryopump is the lowest pressure point. If the pressure in this area is equal to or lower than the vaporization pressure of the liquid at this temperature, there is a large amount of vapor and gas dissolved in the liquid escaping from the liquid, forming small bubbles of steam and gas mixture. These small bubbles with the liquid flow to the high pressure zone, due to the pressure inside the bubble is vaporization, and bubbles around the vaporization pressure is greater than the pressure difference. Under the pressure difference, the bubble is crushed and re-condensed. In the process of condensation, the liquid particles accelerate from the periphery to the center of the bubble. At the moment of condensation, the particles collide with each other, resulting in high local pressure. If these bubbles condense and rupture near the metal surface, the liquid particles will hit the surface of the metal continuously, just like innumerable small warheads. Under stressful and frequent strikes, metal surfaces are gradually destroyed by fatigue, often referred to as denudation. In the resulting bubble is also mixed with a number of lively gases (such as oxygen, etc.), with the release of air bubbles condensation heat, the metal chemical corrosion. The combined action of chemical and mechanical ablation further accelerates the rate of metal damage, a phenomenon known as cavitation damage.
Centrifugal cryogenic pump cavitation began to occur, the smaller cavitation area, the normal operation of the pump no significant impact on the pump performance curve is also not significantly reflected. However, when the cavitation develops to a certain extent, a large number of bubbles are generated, affecting the normal flow of the liquid and even causing the liquid flow to be intermittent, resulting in vibration and noise. At the same time, the flow, lift and efficiency of the pump are obviously decreased, . Serious, the pump can not work. Article by Hangzhou Zed pump finishing In order to avoid cavitation as much as possible in the process design, the liquid should be in the pump before entering a certain degree of subcooling, while the pump to be installed in a lower position, so that the liquid inlet Static pressure head. Also pay attention to keep cold, try to reduce the cold loss.
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