Self-priming pump suction lift
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Usage conditions: Methanol in underground tanks, density 0.75–0.9; modified to a self-priming pump, with a designed suction lift of 5 meters. I would like to ask if the suction lift and the density of the medium have any impact? ? According to the formula P=pgh, the suction lift should be greater compared to water; however, methanol vaporizes easily, leading to cavitation. Do any of my colleagues have any practical experience that I could learn from?
In essence, a self-priming pump utilizes atmospheric pressure; one atmosphere is equivalent to a water column 10 meters high. Given that methanol has a density of around 11–13 meters, and if we exclude the extreme values, then this is roughly the maximum suction height that a self-priming pump can achieve in theory. 7-8 meters is practically the maximum value that can be achieved. But methanol vaporizes easily, and that’s another matter. If the self-priming height is too high, the pump may experience surge.
Based on the saturated vapor temperature of methanol, a height of around 4 meters was determined; furthermore, a desalinated water supply was connected at the inlet, as this seemed to be a more reliable approach. Let’s see how it performs then
What kind of pump is used for methanol self-priming pumps? Cam rotor pump? How is it working now?
The suction lift is affected by the density of the medium; the higher the density, the lower the suction lift. Example: For water, with a density of 1000 kg/m3, the self-priming height can reach 4 meters ； When using concentrated sulfuric acid with a density of 1840 kg/m3, the self-priming height can only reach about 2 meters. For methanol suction, a stainless steel magnetic self-priming pump can be used, which is leak-free.
At normal temperature and pressure, methanol has a relatively low saturated vapor pressure, which means it evaporates easily. Theoretically, a suction lift of 4 meters can be achieved.