On the relationship between the head of a pump and the actual outlet pressure
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If there are three pumps on site, transporting water as the medium, with two of them having a capacity of 80 m3/H at 65 m head and the third one having a capacity of 105 m3/H at 50 m head, what is the gauge pressure indicated by the outlet pressure gauge under normal operating conditions? Is it possible to connect these three pumps in parallel? By adjusting the outlet head to be consistent through the return valve, the delivery pressure of the pump units should be the same, allowing them to be used in parallel. However, in practice, those with a lower head often fail to deliver fluid – where is the error here?
If they are transported together, it’s no problem as long as the external pressure is lower than their own pressure; they can be connected in parallel, and there’s no need to adjust the outlet pressure
A pump with such a high head that produces such low pressure has very low actual efficiency; in the long run, it is advisable to replace it with an appropriate pump, as this will result in better energy savings
When used in parallel, if one of the pumps fails to operate, it is necessary to check whether the actual flow rate being used is too low
Can I say that you’re talking nonsense? The flow rate and head of water pumps operating in parallel must be the same, just as is the case with transformers connected in parallel. It’s not possible to connect them in parallel; your engineers would definitely not allow it.
It is not used in practice in this way. Could you please explain clearly why this is the case – which data factors prevent parallel operation?
This post was last edited by hlcl on 2016-9-10 09:10. The pump operates within a pipeline, and this involves the performance curves of the pump as well as those of the pipeline. In terms of design, it is generally not allowed to connect pumps with different characteristic curves in parallel. If pumps with differing performance curves are used together, the flow rates will be different, and there will be a significant difference in their discharge pressures; pumps with lower head pressure will find it difficult to deliver fluid. Using pumps with different performance curves in parallel is basically a last resort when carrying out modifications. In this case, it is necessary to adjust the pipeline characteristic curve of the pump, that is, to manually maintain a consistent outlet pressure of the pumps by closing the outlet valves of those pumps with higher head. To determine whether the pump is delivering flow, the specific flow rate can be ascertained by comparing the pump’s performance curve with the outlet pressure; it is important to prevent the pump from operating at its minimum flow rate.
According to what was said on the 7th floor, it’s possible to control the outlet pressure properly; parallel connection is indeed feasible. This isn’t nonsense, and I’m not trying to deceive anyone – does anyone else have any insights? At least we should know whether it’s possible or not