The vaporization problem when centrifugal pumps transport liquids with low boiling points
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In the plant, centrifugal pumps are used to transport vinyl chloride liquid. The boiling point of vinyl chloride is -13.9°C, and it vaporizes very easily inside these pumps, resulting in cavitation. Is there any good solution to this problem? The saturated vapor pressure of vinyl chloride at 25°C is 0.4 MPa. The operation of the centrifugal pump’s shaft can also lead to an increase in temperature, thereby raising the saturated vapor pressure.
It seems that only by increasing the inlet pressure can cavitation be avoided.
The pressure in the vinyl chloride sphere tank is fixed, and the lower the liquid level, the lower the pressure; therefore, measures to increase the inlet pressure are not feasible.
This post was last edited by ylb913 on 2015-7-8 09:35. Measures such as raising the liquid level at the pump inlet (raising the liquid level of the equipment or the equipment itself), and using thicker inlet pipelines, should be taken. Alternatively, work on the pump itself to reduce its required net positive suction head.
Using 25 degrees is not very appropriate; for tanks storing such materials, a maximum storage temperature of 50 degrees should be chosen. The saturated vapor pressure at this temperature should be used to determine the net positive suction head of the pump, which in turn helps to decide the installation height of both the pump and the tank
A cooling device is added at the inlet to lower the inlet temperature. Or increase inbound traffic. Either become a double-suction impeller or be equipped with an inducer wheel
I don’t know much about multi-stage pumps; shielded pumps should work though. But now, the best approach is to avoid cavitation without replacing the pump
Indeed, but the higher the temperature, the easier it is for vinyl chloride to vaporize, making this problem even more difficult to solve
The inlet pressure is now 80, while the outlet pressure is 50. The inlet pipeline is insulated with polyurethane, and the spherical tank is equipped with a spray water system
This should work, though the cost is not low