Installation height and cavitation of RY vertical heat transfer oil pump 1. Installation height of RY vertical heat transfer oil pump Hg Allowable suction vacuum height Hs refers to the maximum vacuum that can be reached by the pressure p1 at the pump inlet and the actual allowable vacuum The height Hs value is not a value calculated according to the formula, but is a value experimentally determined by the pump manufacturer. This value is attached to the pump sample for user to check. Installation height and cavitation phenomenon of RY vertical heat transfer oil pump 1. Installation height of RY vertical heat transfer oil pump Hg
The allowable suction vacuum height Hs refers to the maximum vacuum that the pressure p1 at the pump inlet can allow, and the actual allowable vacuum height Hs value is not a value calculated according to the formula, but is a value experimentally determined by the pump manufacturer. Values ​​are attached to the pump sample for user review. It should be noted that the Hs value given in the pump sample is the value when the cleaning oil is used as the working medium, the operating condition is 20 ° C and the pressure is 1.013 × 105 Pa. When the operating conditions and working medium are different, the conversion is required.
(1) Delivering clean oil, Botaibang, but the operating conditions are different from the experimental conditions, and can be converted according to the following formula: Hs1=Hs+(Ha-10.33)-(HÏ…-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 clear oil. 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 RY vertical heat transfer oil pump is found on the sample to allow the vacuum height Hs = 5.7m. 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 20°C clear oil;
(2) The installation height of the pump when the 80°C oil is delivered.
Solution: (1) The installation height of the pump is known to deliver 20°C oil: Hs=5.7m
Hf0-1=1.5m
U12/2g≈0
The local atmospheric pressure is 9.81x104Pa, 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) When the 80 °C oil is transported when transporting 80 °C oil, the installation height can not be calculated directly by using the Hs value in the pump sample. The Hs should be converted 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 the 80 ° C oil 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
2. Cavitation phenomenon The cavitation phenomenon of the RY vertical heat transfer oil pump means that the liquid to be transported 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 pump inlet (actually at the inlet of the blade), causing the pump Noise and vibration are generated. In severe cases, the flow rate, head pressure and efficiency of the pump are significantly reduced. Obviously, the cavitation phenomenon is not allowed in the normal operation of the RY vertical heat transfer oil 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 oil level, at least 0.72m below the liquid level.
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