First, the cavitation phenomenon of centrifugal pump
The cavitation phenomenon of centrifugal pump refers to the partial vaporization of the transported liquid due to the saturated vapor pressure at the conveying temperature equal to or lower than the pressure at the pump entrance (actually for the blade entrance), causing the pump to produce noise and vibration, and in serious cases, the pump flow, pressure head and efficiency are significantly reduced, obviously, the cavitation phenomenon is not allowed to occur in the normal operation of the centrifugal pump. The key to avoid cavitation is that the installation height of the pump should be correct, especially when transporting volatile liquids with high temperatures.
Second, the installation height of centrifugal pump Hg
Allowable suction vacuum height Hs refers to the maximum vacuum degree that the pressure p1 at the pump inlet can be allowed to achieve
The actual Hs value of the allowable suction vacuum height is not a value calculated according to the formula, but a value determined by the pump manufacturer's experiment, which is attached to the pump sample for user reference. It should be noted that the Hs value given in the pump sample is the value when clean water is used as the working medium, the operating condition is 20℃ and the pressure is 1.013×105Pa, and when the operating conditions and the working medium are different, it needs to be converted.
(1) Conveying water, but the operating conditions are different from the experimental conditions, can be converted according to the following formula
Hs1=Hs+(Ha-10.33) - (hVIL-0.24)
(2) Transporting other liquids When the conditions of the transported liquid are different from the experimental conditions, a two-step conversion is required: The first step is to detect Hs1 in the pump sample according to the above formula; In the second step, Hs1 is converted to H猃 according to the following formula