Given that the pump has a wide range of flow rates, can bypass be used to control the flow rate at low flow rates? As shown in the figure
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Given that the pump has a wide range of flow rates, can bypass be used to control the flow rate at low flow rates? As shown in the diagram, my pump has a flow rate of 32 m3/h and a head of 40 meters. I need a minimum flow rate of 5 m3/h, with a maximum flow rate of 30 m3/h; the head should remain around 35 meters. It’s not a problem when the flow rate is high, but what should I do when it’s as low as 5 m3/h? Could I add a bypass line, along with a control valve on that bypass line, to help regulate the flow rate on the main line? I thought about using variable frequency drive, but after that both the flow rate and head pressure decrease, and it’s no longer possible to maintain the required head pressure. Is this an acceptable solution? If that doesn’t work, what other options are there? Thank you!
How about adding the return line after the main flow control? If the opening of the main control valve remains unchanged and only the return line valve is adjusted, will the head change? Should the return line go to the upstream storage tank, or directly to the pump inlet?
It’s such a big difference; I’m not sure if it’s possible. But with such large fluctuations in flow rate, the pipe diameter must be inappropriate at the lowest flow levels, right?
In fact, centrifugal pumps allow for variations in flow rate; the flow rate can be controlled through the outlet control valve. Moreover, a lower flow rate corresponds to a higher head, as determined by the performance curve. Therefore, it is not necessary for all 32 m3 of flow rate to pass through the pump. If the required flow rate is 5 m3, this may already be below the pump’s minimum flow rate. A minimum flow rate limit is established to protect the pump; this limit can be achieved by allowing a certain amount of flow to pass through an orifice plate. For example, if the pump’s minimum flow rate is 7 m3, then when the process requires 5 m3 of flow, only 2 m3 need to pass through the pump. As for the owner’s claim that you need to maintain a head of 35m constant, the reason for this is that pump systems at the user end usually have pressure control mechanisms, namely backpressure control. At low flow rates, the head is higher, which means that more of the excess head has to be dissipated within the piping system. Therefore, it is possible to close the gate valves before and after the control valve slightly, thereby distributing some of the pressure loss to the control valve itself, allowing it to regulate the flow rate stably within its capabilities. I’m not sure if it was explained clearly?
In fact, centrifugal pumps allow for variations in flow rate; the flow rate can be controlled through the outlet control valve. Moreover, a lower flow rate corresponds to a higher head, as determined by the performance curve. Therefore, it is not necessary for all 32 m3 of flow rate to pass through the pump. If the required flow rate is 5 m3, this may already be below the pump’s minimum flow rate. A minimum flow rate limit is established to protect the pump; this limit can be achieved by allowing a certain amount of flow to pass through an orifice plate. For example, if the pump’s minimum flow rate is 7 m3, then when the process requires 5 m3 of flow, only 2 m3 need to pass through the pump. As for the owner’s claim that you need to maintain a head of 35m constant, the reason for this is that pump systems at the user end usually have pressure control mechanisms, namely backpressure control. At low flow rates, the head is higher, which means that more of the excess head has to be dissipated within the piping system. Therefore, it is possible to close the gate valves before and after the control valve slightly, thereby distributing some of the pressure loss to the control valve itself, allowing it to regulate the flow rate stably within its capabilities. I’m not sure if it was explained clearly?
In fact, centrifugal pumps allow for variations in flow rate; the flow rate can be controlled through the outlet control valve. Moreover, a lower flow rate corresponds to a higher head, as determined by the performance curve. Therefore, it is not necessary for all 32 m3 of flow rate to pass through the pump. If the required flow rate is 5 m3, this may already be below the pump’s minimum flow rate. A minimum flow rate limit is established to protect the pump; this limit can be achieved by allowing a certain amount of flow to pass through an orifice plate. For example, if the pump’s minimum flow rate is 7 m3, then when the process requires 5 m3 of flow, only 2 m3 need to pass through the pump. As for the owner’s claim that you need to maintain a head of 35m constant, the reason for this is that pump systems at the user end usually have pressure control mechanisms, namely backpressure control. At low flow rates, the head is higher, which means that more of the excess head has to be dissipated within the piping system. Therefore, it is possible to close the gate valves before and after the control valve slightly, thereby distributing some of the pressure loss to the control valve itself, allowing it to regulate the flow rate stably within its capabilities. I’m not sure if it was explained clearly?
How is the orifice plate selected? ?
I would like to ask: after a certain flow rate passes through the orifice plate (which is equivalent to pressure relief), will the head pressure in the main pipeline decrease significantly to the point where it can no longer meet the required head pressure for that pipeline? ? ?
So how can we ensure that the minimum flow rate is 2 M3/h? How can this minimum flow rate be guaranteed or controlled? ?
Is there no return flow via a pump on the storage tank? Moderately adjusting the reflux can also control the flow rate