Hot: installation height of slurry pump and cavitation phenomenon
DO PUMP is a manufacturer specializing in the production of China slurry pump, slurry pump parts, Warman slurry pump, sand pumps, dredging pumps, and submersible sand pumps. At the same time, DO PUMP provides sand pump design and selection, and helps customers solve sand pump solutions.
1. The device height of the slurry pump Hg
The allowable vacuum height Hs refers to the maximum vacuum that the pressure p1 at the pump inlet can allow
It is the value determined experimentally by the pump manufacturer, and the actual allowable suction vacuum height Hs is not a value calculated according to the formula. This value is attached to the pump sample for users to check. 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 1.013105Pa, when the operating conditions and working medium are different, conversion is required.
But the operating conditions are different from the experimental conditions, 1 conveying clean water. Can be converted according to the following formula
Hs1=Hs＋(Ha10.33Hυ－0.24
A two-step conversion is required: the first step is to convert the Hs1 found in the pump sample according to the above formula. The second step is to convert Hs1 to Hs2 according to the following formula to transport other liquids. When the conditions of the liquid to be transported and the villain are different from the experimental conditions.
NPSH Δh
When calculating the height of the device, use the NPSH Δh to calculate, for the oil pump. Even if the NPSH Δh is checked from the oil pump sample, its value is also measured with 20℃ clean water. If other liquids are to be transported, calibration is also required. Check the relevant books.
The actual height of the pump should be less than the calculated value. Also, consider from the perspective of safety. When the calculated Hg is negative, it means that the suction port of the pump should be below the liquid level of the tank.
For example, a slurry pump found from the sample that the allowable suction vacuum height is Hs=5.7m. The total resistance of the known suction pipe is 1.5mH2O and the local atmospheric pressure is 9.81104Pa. The dynamic pressure head of the liquid in the suction pipe can be ignored. Try calculation:
1 Pump device when delivering 20℃ clean water; www.00jf.com
2 Change to the height of the pump when delivering 80℃ water.
Solution: 1 The height of the pump when delivering 20℃ clean water
Known: Hs=5.7m
Hf0-1=1.5m
u12/2g≈0
Therefore, the device height of the pump is Hg=5.7-0-1.5=4.2m, and the local atmospheric pressure is 9.81104Pa, which is basically in line with the experimental conditions when the pump leaves the factory.
2The height of the pump when delivering 80℃ water
It is not possible to directly use the Hs value in the pump sample to calculate the height of the device when delivering water at 80°C. Need to convert Hs time line by the following formula, that is, Hs1 = Hs + (Ha10.33Hυ－0.24
It is known that Ha=9.81104Pa≈10mH2O. The saturated vapor pressure of 80℃ water is 47.4kPa from the appendix.
Hv=47.4103Pa=4.83mH2O
Hs1=5.7+1010.334.83+0.24=0.78m
2. Cavitation phenomenon of slurry pump
Causes noise and vibration of the pump. The cavitation phenomenon of the slurry pump means that the liquid to be transported is partially vaporized due to the saturated vapor pressure at the delivery temperature being equal to or lower than the pump inlet (actually the pressure at the blade inlet. In severe cases, the pump The flow rate, pressure head and efficiency of the slurry pump are significantly reduced. Obviously, cavitation is not allowed in the normal operation of the slurry pump.
Especially when transporting high-temperature volatile liquids, the key to preventing cavitation is that the height of the pump is correct. Pay more attention.
Substitute the value of Hs1 into the formula to obtain the height of the device
Hg=Hs1Hf0-1=0.781.5=0.72m
Indicates that the pump should be installed below the liquid level of the pool, and Hg is a negative value. At least 0.72m lower than the liquid level
