Regarding the actual lifting height of the pump
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I have a question that has been bothering me for a long time. Suppose a slurry pump is used to pump clean water, with only one valve at the outlet. The pipeline is extremely long, and pipeline resistance must be taken into account. When the pump is started, the clean water rises to a certain height and then stops there, say 50 meters. If the valve is then closed, will the height of the water change? If we go by the principle that as flow rate decreases, head increases, then the height increases ； But considering pipe resistance, the increased head (energy) loss is incurred at the valve, leaving the height unchanged. What exactly is the situation? In the second case, closing the valve can only regulate the flow rate – does it have no other function? The original issue is that the floor-sweeping pump in our factory has trouble pumping coal slurry water; we want to increase the diameter of the outlet pipe in order to raise the water lifting height. I’m not sure if this is feasible. Currently, we are just adding valves, and reducing their opening doesn’t seem to have much effect. I wonder if it’s because the outlet pipe is too thick, rather than the issue being related to insufficient flow within the pipe. Thank you to all of you
When selecting a pump, it depends on the type of medium to be transported; for a certain flow rate, pipes of an appropriate diameter along with a pump that matches it are needed. Reducing the outlet valve only increases the pressure at the pump head, without increasing the pressure in the pipeline downstream of the outlet valve. If your assumption is correct, then all pumps can have their flow rate and head changed by altering the diameter of the outlet pipe? Obviously not. Therefore, the slurry pump should be considered for model replacement or changes to the fluidity of the medium.
If the valve is closed, the height of the water column will decrease.
The clear water level remains constant; this is the pump’s shut-off head
There have also been such doubts – to learn* it a bit
Yes, although the valve was turned down, the flow rate didn’t change; checking the flow and pressure curve chart shows that the pressure remained unchanged as well. Generally, when adjusting valves, it is first the change in pipe resistance that leads to a change in flow rate; flow rate is controlled by adjusting pressure, rather than directly adjusting the flow rate itself.
When the resistance of the fluid in the pipeline remains constant and the pump’s output power stays unchanged, the head is determined by the size of the fluid flow channel, the size of the impeller, and the power of the motor; thus, the head can be controlled by adjusting these three factors
Check the performance curve of your pumps.
Correct~~~ At the highest point, Q=0; at this point it is already a closed-loop lift. When the valve is closed, as long as it isn’t fully closed, the flow rate remains 0 and there is no pipe resistance, so the liquid level stays unchanged~~~~~~~~~~~~~~~~~~
At this point, there is no flow; in other words, the pump is operating at its shut-off point. According to the pump’s performance curve, to increase the pumping height, it is possible to do so by changing the type of pump, adjusting its speed, or increasing the diameter of the impeller.