Why are flow meters generally installed on the outlet pipeline of a pump rather than the inlet pipeline
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Regarding the question in the note, I’m not sure what the cause is – is it unstable flow at the pump inlet or a pressure issue?
I think the outlet pipeline is thinner than the inlet one, has a higher flow rate, and is easier to measure. At the same time, there is a pressure difference in the flow meter, and placing it at the inlet is not conducive to suction
I’m not quite in agreement with the idea regarding pressure difference; the pressure difference caused by a flow meter should be quite small, right? It should be smaller at least than that caused by filters and similar devices I’m not too in agreement with the idea of flow rate either; there’s no theory stating that flow meter measurement must be closely related to flow rate
The pump also has a minimum flow line; when the flow rate at the pump inlet is not equal to the actual processing volume, it is necessary to subtract the flow rate corresponding to the minimum flow line!
If it is installed on the inlet pipeline, a vacuum may be created at the pump inlet due to valve failures, posing a risk to the process. The pressure at the outlet can be adjusted via a bypass, which helps prevent the pump from running dry.
It doesn’t seem to state that it must be installed on the pump outlet pipeline. However, in general, the pump inlet pipeline is short, which makes it inconvenient to install flow meters. Additionally, most flow meters have installation requirements, such as straight pipe sections, etc ； The pump inlet pipelines are usually short and not easy to meet the requirements. So in most cases, the flow meter is installed on the outlet pipeline of the pump.
The inlet pipe is too short, failing to meet the requirements for meter installation; if it is too long, the resistance will be high, which can easily lead to cavitation
The pump inlet should not have too large a pressure drop; installing a flow meter will always result in an increase in pressure drop, and it may also increase the length of the piping, thereby increasing its complexity.
There are no strict requirements regarding the installation location of the flow meter; it is simply necessary to ensure easy installation and visibility. It should also be at a certain distance from the pump, with short inlet pipes for the pump and an outlet that is easy to view for maintenance purposes.
There is also a minimum flow line at the pump outlet; the flow meter installed at the inlet measures the total flow of the pump, and it does not reflect the actual flow entering the next device.
Flow measurement always refers to the flow rate of the fluid being delivered; generally, pumps have backflow, so measuring the flow rate at the pump inlet does not give accurate results