The cavitation phenomenon of the centrifugal pump means that the liquid to be delivered is partially vaporized due to the pressure of the saturated vapor at the delivery temperature being equal to or lower than the pressure at the inlet of the pump (actually at the inlet of the blade), causing noise and vibration of the pump. The pump's flow, head and efficiency are significantly reduced. First, the installation height of the centrifugal pump Hg Allowable suction vacuum height Hs is the maximum vacuum that can be reached by the pressure p1 at the pump inlet. The actual allowable vacuum height Hs value is not a value calculated according to the formula, but a value determined experimentally by the pump manufacturer. This value is attached to the pump sample for the user to check. It should be noted that the Hs value given in the pump sample is the value when the water is used as the working medium, the operating conditions are 20 ° C and the pressure is 1.013 × 105 Pa. When the operating conditions and working medium are different, the conversion is required. (1) Conveying clean water, but the operating conditions are different from the experimental conditions, and can be converted according to the following formula Hs1=Hs+(Ha-10.33)-(Hυ-0.24) (2) Conveying other liquids When the conditions of the liquid to be transported and the villain are different from the experimental conditions, a two-step conversion is required: the first step is based on the Hs1 detected in the pump sample; the second step is as follows: Hs1 Converted to H's Cavitation allowance Δh For the oil pump, calculate the installation height with the NPSH Δh, that is, use the NPSH Δh to be taken from the oil pump sample, and the value is also measured with 20 ° C water. If other liquids are transported, corrections are also required. Check the relevant books. From a safety point of view, the actual installation height of the pump should be less than the calculated value. Also, when the calculated Hg is negative, it indicates that the suction port position of the pump should be below the liquid level of the sump. For example, a centrifugal pump is found on the sample to allow the vacuum height Hs = 5.7 m. It is known that the total resistance of the suction line is 1.5 mH2O, the local atmospheric pressure is 9.81 x 104 Pa, and the dynamic head of the liquid in the suction line is negligible. Trial calculation: (1) Installation of the pump when conveying water at 20 ° C; (2) The installation height of the pump when the water is transported at 80 °C. Solution: (1) Installation height of pump when conveying 20°C clean water Known: Hs=5.7m Hf0-1=1.5m U12/2g≈0 The local atmospheric pressure is 9.81×104Pa, which is basically consistent with the experimental conditions when the pump is shipped, so the installation height of the pump is Hg=5.7-0-1.5=4.2m. (2) Mounting height of the pump when transporting 80°C water When transporting water at 80 °C, the installation height cannot be calculated directly from the Hs value in the pump sample. It is necessary to convert the Hs according to the following formula, ie Hs1=Hs+(Ha-10.33)-(Hυ-0.24) It is known that Ha = 9.81 × 104 Pa ≈ 10 mH 2 O, and the saturated vapor pressure of water at 80 ° C was found to be 47.4 kPa by the appendix. Hv=47.4×103Pa=4.83mH2O Hs1=5.7+10-10.33-4.83+0.24=0.78m Second, the cavitation phenomenon of centrifugal pumps The cavitation phenomenon of the centrifugal pump means that the liquid to be delivered is partially vaporized due to the pressure of the saturated vapor at the delivery temperature being equal to or lower than the pressure at the inlet of the pump (actually at the inlet of the blade), causing noise and vibration of the pump. The flow rate, head pressure and efficiency of the pump are significantly reduced. Obviously, cavitation is not allowed in the normal operation of the centrifugal pump. The key to avoiding cavitation is that the pump should be installed at the correct height, especially when transporting volatile liquids with high temperatures. Substituting the Hs1 value into the formula to obtain the installation height Hg=Hs1-Hf0-1=0.78-1.5=-0.72m Hg is a negative value, indicating that the pump should be installed below the pool level, at least 0.72m below the liquid level. Concerned about surprises Label: installation height and cavitation of centrifugal pump Previous: Building an intelligent system electric lock Next: Encyclopedia of centrifugal pumps Minimalist Wall Lamp,Minimalist Wall Light,Minimal Wall Light,Minimalist Wall Lighting Zhongshan Seekyo Lighting CO., Ltd. , https://www.seekyomodernlamp.com