What does \"surge in flow rate\" mean when shutting down a centrifugal pump?

The so-called sudden increase in flow rate that occurs when switching centrifugal pumps refers to the phenomenon where, during the process of switching between two or more centrifugal pumps operating in parallel, uneven flow distribution or changes in system pressure cause one of the pumps to suddenly handle an excessive amount of flow. **The main reasons are as follows: ** 1. **Mismatched pump performance**: If there is a significant difference in the performance curves of pumps connected in parallel, it may lead to uneven flow distribution. 2. **System piping design**: Improper piping design or issues such as blockages can also lead to uneven flow distribution. 3. **Control system issues**: Improper setting or malfunction of the parameters in the automatic control system can lead to inaccurate control during pump switching, resulting in excessive flow. **The solutions are as follows: ** 1. **Choose pumps with similar performance**: Pumps that operate in parallel should ideally have performance curves that are similar to each other, so that the flow rate can be distributed more evenly. 2. **Optimize pipeline design**: Examine and improve the pipeline design to ensure a uniform distribution of resistance within the pipes, thereby minimizing local resistance as much as possible. 3. **Adjust control strategies**: Optimize the start/stop and variable frequency control strategies of the pumps, implement precise flow and pressure control, and avoid flow competition during pump switching. 4. **Install flow balancing devices**: Install flow balancing devices, such as flow distributors, in the system to balance the load on each pump. 5. **Conduct system debugging**: Perform regular maintenance and debugging of the system to ensure that all devices are operating properly, while adjusting the control parameters based on actual operation conditions. Through these measures, the problem of sudden flow fluctuations in centrifugal pumps during pump switching operations can be effectively avoided, ensuring the stable operation of the pumps and the safety of the system. .

It probably refers to the fluctuations (increase) in traffic caused by it. The correct procedure is to start the standby pump as required, and then, while maintaining a constant flow rate, gradually close the outlet valve of the online pump and gradually open the outlet valve of the standby pump, until the outlet valve of the online pump is fully closed; at that point, the outlet valve of the standby pump should be adjusted to an appropriate opening degree based on the required flow rate. Then stop the online pump, close the inlet valve, and cut off the power supply – this completes the pump replacement. Such a procedure will not result in any fluctuations in flow rate; for reference only.

My understanding is that what you call seizing market share is a kind of “diversion” phenomenon, and I think 3L’s view is correct. Additionally, it is possible to remotely control the pumping rhythm at the site using the flow rate at the pump’s outlet, as well as through flow control valves. I would like to ask whether this issue occurs occasionally or all the time; if it happens only occasionally, then there’s no major problem – careful operation will suffice. If this phenomenon occurs every time, you need to first check whether the mechanical properties of the two pumps and motors are consistent with those of the pipelines in place, and pay special attention to whether the outlet filter is clogged, as well as the opening degree of the pre-heating line and drain line in the process pipelines.

When you turn the pumps in parallel on or off, it causes a change in the resistance in the outlet pipes connected to them. This change can be considered as an equivalent to opening or closing the valve of the pump that is still running, which in turn results in fluctuations in the flow rate of the centrifugal pump that is still in operation. Why is the flow rate of centrifugal pumps affected by the outlet? When a centrifugal pump leaves the factory, its impeller diameter has been determined and its rotational speed is fixed; therefore, the parameters of this centrifugal pump are fixed, and the specific details can be seen from its performance curve. So, how is the flow rate or pressure of this centrifugal pump controlled after it is installed on-site? It involves adjusting the resistance of the outlet pipe; the most common method is to control the opening degree of the outlet valve~