One-on-one interactive guide on centrifugal pump technology
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This post was last edited by foam_ZPTK on 2025-7-19 11:31. My area of expertise is centrifugal pumps; I’m online from time to time and will try to respond as promptly as possible； Experience in the pump industry: 16 years
OP, what kind of pumps generally require seal water? What is the function of the seal water?
For example, the slurry pump uses the external flushing PLAN32 scheme, which requires external flushing water to clean the seal. For media that are prone to crystallization (such as alkaline solutions), 11+62 is generally used. At this point, PLAN62 is referred to as rapid cooling, and water can be used to remove the crystalline deposits from the back side of the mechanical seal. The choice of flushing medium is determined by the medium pumped by the pump; the fluid injected must be compatible with the process fluid and must not contaminate it.
For a centrifugal pump (using diesel as the fluid), I want to machine the impeller. Since the power of the pump and the motor does not match – the pump is powerful enough that the motor tends to overload – are there any formulas or considerations to keep in mind?
D2 is the diameter of the original impeller, while D2' is the diameter of the impeller after cutting. Since head is related to the square of a value, it is mainly calculated based on head. When cutting, you can take into account the calculation results and leave some extra margin to prevent the parameters from not meeting the requirements after cutting. If there is a slight deviation in flow rate and head after cutting, the blade outlet can be ground, that is, the dark gray area shown in the diagram can be removed. The outlet angle can be increased to achieve a head increase of up to 5% near the optimal efficiency point (depending on the outlet angle). But at least 2 millimeters should be left.
BZ, may I ask what size the filter area of the inlet filter for conventional centrifugal pumps should be?
This post was last edited by 3983596_FPPZ on 2018-9-1 at 13:49. It is also necessary to consider the impact of pressure drop on the net positive suction head; measure the pressure difference across the filter at both the rated flow rate and maximum flow rate points to determine the pressure drop, and then subtract that value from the net positive suction head. Since it’s the result of design work, I’m not entirely confident, so let’s base the decision on the actual numbers
Generally, the alarm device will be activated when the pressure difference is ≥0.35 bar; at this point, the filter screen should be removed for cleaning； When it reaches 0.5 bar, the machine should be stopped immediately ； At higher pressures, the filter screen gets damaged, which ultimately leads to damage to the pump.
If the above alarm values and shutdown values result in the device’s net positive suction head not being sufficient, these two values need to be reduced accordingly.