Croos Pump (Shanghai) Co., Ltd.

The Causes and Prevention of Cavitation of Centrifugal Pump

The cavitation of centrifugal pump is one of the most common centrifugal pump faults, there are many reasons for this phenomenon, such as the improper use of operators, the quality of centrifugal pump products and so on. The products have to pass the inspection procedure, and the factors of human operation are more likely. In the state of work, the operating environment of centrifugal pump and the influence of operating factors account for most of the ratio of centrifugal pump cavitation. First, let we konw how the cavitation of centrifugal pump occurs.

The causes and process of cavitation of centrifugal pump:

When the centrifugal pump is working, the liquid pressure of the centrifugal pump will decrease as the fluid in the pump decreases from the inlet to the impeller inlet. When the liquid pressure near the inlet of the blade reaches its minimum, the impeller begins to work on the liquid, and the liquid pressure begins to rise. When the minimum pressure near the inlet of the blade is less than the saturated vapor pressure of the liquid transport temperature, the vaporization of the liquid will occur. Gases that dissolve in liquids also escape, and form bubbles. When the bubble is flowing with the liquid to the lower pressure of the blade, the outside liquid pressure is higher than the vaporization pressure inside the bubble, then the bubble is recongealed to form the cavity. Instantly, the fluid around the cavity rushes at a high speed, causing the liquid to collide with each other, and it will cause the local pressure to increase abruptly. This not only impedes the normal flow of liquid from the centrifugal pump. And when these bubbles burst near the wall of the impeller, the liquid will continuously impact the inner surface of the centrifugal pump. Long term impact will cause structural damage and peeling of the inner wall of the centrifugal pump. If the bubbles are mixed with some chemical gas like oxygen, the gas condensate will use bubbles when gives off heat knot (local temperature can reach 200 ~ 200 ℃), it also forms thermocouple, which produces electrolysis, forming electrochemical corrosion, which speeds up the destruction of metal. Like this liquid vaporization, condensation, impact, formation of high pressure, high temperature, high frequency impact load, and the phenomenon of mechanical stripping and electrochemical corrosion of metal materials is called centrifugal pump cavitation. When the cavitation occurs, the mechanical denudation and chemical corrosion can cause the material to be destroyed, and the noise and vibration will occur. When the cavitation develops seriously, the presence of a large number of bubbles can clog up the cross section of the flow channel and reduce the energy obtained from the impeller, resulting in the interruption of the fluid in the pump and not working properly.

During the cavitation of centrifugal pump, there are four main factors that affect the centrifugal pump:

1. The structure parameters of centrifugal pump: shape of impeller suction inlet, width of inlet edge of blade and position of inlet edge of blade and shape of front cover plate and so on. When cavitation of centrifugal pump occurs, and the influence proportion of its own physical structure is also larger.

2. The work status of centrifugal pump: pump flow, lift, speed.

3. The installation of centrifugal pump: it is necessary to calculate the hydraulic loss and installation height of pump suction pipe.

4. The working environment of centrifugal pump: the atmospheric pressure in the work place where the centrifugal pump is located and the temperature of conveying the liquid. Different types of centrifugal pumps can be used for different types of centrifugal pumps. For example, the transmission of acidic liquid can be used to choose corrosion - resisting centrifugal pump, the chemical fertilizer of smelting dye can be used in glass steel centrifugal pump.

Cavitation of centrifugal pump is one of the common mechanical faults. All mechanical equipment, in the long working condition, will have the occurrence of mechanical equipment damage, when we encounter the cavitation phenomenon of centrifugal pump, we should first analyze whether it is the operation problem or the influence of the working environment of the centrifugal pump. If it's not, it's a product technical problem. The technological innovation of industrial products is faster, and there will be more high-tech products in the future.

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