9 measures to prevent cavitation of centrifugal pumps
2021-08-24 01:26:13
The cavitation of the centrifugal pump is caused by the pressure at the partial low pressure zone near the inlet of the liquid passage being reduced to the saturated vapor pressure of the liquid, resulting in partial vaporization of the liquid. Therefore, any factor that can reduce the local pressure to the vaporization pressure of the liquid may be the cause of the induced cavitation. The conditions for cavitation should be considered in terms of the characteristics of the inhalation device, the structure of the pump itself, and the nature of the liquid being delivered.
1) Structural measures: double suction impeller is used to reduce the flow rate through the impeller, thereby reducing the NPSH of the pump; supercharged pre-pump is installed in front of the large high-lift pump to increase the inlet pressure; impeller special Designed to improve the flow condition at the inlet of the blade; an inducer wheel is added in front of the centrifugal impeller to increase the flow pressure into the impeller.
2) The installation height of the pump, the higher the installation height of the pump, the lower the inlet pressure of the pump, and the lower the installation height of the pump can increase the inlet pressure of the pump. Therefore, a reasonable determination of the installation height of the pump can avoid cavitation of the pump.
3) The resistance of the suction line, the more the elbows, valves and other fittings are installed in the suction line, the greater the resistance of the pipeline, the lower the inlet pressure of the pump. Therefore, it is possible to prevent the pump from cavitation by minimizing unnecessary pipe fittings or increasing the diameter of the pipette as much as possible and reducing the pipe resistance.
4) The geometry of the pump, since the kinetic energy and static pressure energy of the liquid at the pump inlet can be converted to each other, the value remains unchanged. When the inlet liquid flow rate is high, the pressure is low, and when the flow rate is low, the pressure is high. Therefore, the flow area of ​​the pump inlet is increased, and the inlet speed of the impeller is lowered. It can prevent the pump from cavitation.
5) The density of the liquid. The higher the suction density of the pump, the smaller the suction height of the pump. When the pump with the smaller density of the installed liquid is used to transfer the liquid with higher density, the pump may generate cavitation, but the transport density is higher. When a pump with a large liquid reforms a liquid with a lower density, the inlet pressure of the pump is higher and no cavitation occurs.
6) The temperature at which the liquid is delivered. The saturated vapor pressure of the liquid increases as the temperature increases. When the inlet pressure of the pump is constant, when the temperature of the liquid is raised, the saturated vapor pressure of the liquid may rise to be equal to or higher than the inlet pressure of the pump, and the pump may cavitation.
7) Liquid level of the suction pool. When the liquid level pressure of the suction tank is high, the inlet pressure of the pump also increases. Conversely, the inlet pressure of the pump is lower, and the pump is prone to cavitation.
8) Volatile liquid transporting liquid The volatile vapor pressure of the liquid which is more volatile at the same temperature is higher. Therefore, the pump which transports the volatile liquid is liable to cause cavitation.
9) Other measures: The material of the over-flow part of the pump is made of material resistant to cavitation damage; the rotation speed of the pump is reduced.
1) Structural measures: double suction impeller is used to reduce the flow rate through the impeller, thereby reducing the NPSH of the pump; supercharged pre-pump is installed in front of the large high-lift pump to increase the inlet pressure; impeller special Designed to improve the flow condition at the inlet of the blade; an inducer wheel is added in front of the centrifugal impeller to increase the flow pressure into the impeller.
2) The installation height of the pump, the higher the installation height of the pump, the lower the inlet pressure of the pump, and the lower the installation height of the pump can increase the inlet pressure of the pump. Therefore, a reasonable determination of the installation height of the pump can avoid cavitation of the pump.
3) The resistance of the suction line, the more the elbows, valves and other fittings are installed in the suction line, the greater the resistance of the pipeline, the lower the inlet pressure of the pump. Therefore, it is possible to prevent the pump from cavitation by minimizing unnecessary pipe fittings or increasing the diameter of the pipette as much as possible and reducing the pipe resistance.
4) The geometry of the pump, since the kinetic energy and static pressure energy of the liquid at the pump inlet can be converted to each other, the value remains unchanged. When the inlet liquid flow rate is high, the pressure is low, and when the flow rate is low, the pressure is high. Therefore, the flow area of ​​the pump inlet is increased, and the inlet speed of the impeller is lowered. It can prevent the pump from cavitation.
5) The density of the liquid. The higher the suction density of the pump, the smaller the suction height of the pump. When the pump with the smaller density of the installed liquid is used to transfer the liquid with higher density, the pump may generate cavitation, but the transport density is higher. When a pump with a large liquid reforms a liquid with a lower density, the inlet pressure of the pump is higher and no cavitation occurs.
6) The temperature at which the liquid is delivered. The saturated vapor pressure of the liquid increases as the temperature increases. When the inlet pressure of the pump is constant, when the temperature of the liquid is raised, the saturated vapor pressure of the liquid may rise to be equal to or higher than the inlet pressure of the pump, and the pump may cavitation.
7) Liquid level of the suction pool. When the liquid level pressure of the suction tank is high, the inlet pressure of the pump also increases. Conversely, the inlet pressure of the pump is lower, and the pump is prone to cavitation.
8) Volatile liquid transporting liquid The volatile vapor pressure of the liquid which is more volatile at the same temperature is higher. Therefore, the pump which transports the volatile liquid is liable to cause cavitation.
9) Other measures: The material of the over-flow part of the pump is made of material resistant to cavitation damage; the rotation speed of the pump is reduced.
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