Since the minimum process flow rate is greater than the pump’s minimum stable flow rate, is it still necessary to install a minimum return line?
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As the title suggests: if the minimum process flow rate is greater than the pump’s minimum stable flow rate, is it still necessary to install a minimum return line? There are two opinions among those around me at the moment. One is that since the minimum flow rate required for the process is greater than the pump’s minimum stable flow rate, there is no need to install a minimum reflux line. The other opinion is that even though the process’s minimum flow rate is higher than the pump’s minimum stable flow rate, it is still necessary to have a reflux line in order to prevent pump damage during startup and shutdown. Let’s discuss this
A minimum return line should be installed to prevent cavitation when the pump’s flow rate falls below the rated value! And it can eliminate some of the axial force! This post was last edited by anship1984 on 2009-3-28 12:29.]
The process safety analysis of the pump can be carried out based on the PFD’s flow diagram, such as through HAZOP analysis, to determine whether a reflux line is necessary. It is usually required in situations such as startup and shutdown, or in emergency conditions. Of course, it is possible to determine this only by examining the PFD.
In favor of establishing it. If it is a formal requirement
The second explanation is slightly better, but the relationship between the minimum flow rate required for the process and the pump’s minimum stable flow rate is primarily determined by considerations related to the pump’s efficiency; it has little to do with whether a return pipeline is installed or not； As for installing a return pipeline, it is based on the protection of the pump itself.
Purpose of setting a minimum return pipe: 1. To protect the pump. 2. During operation intervals, close the control valve at the pump outlet; this allows the material in the tank to circulate back and forth between the tank and the pump, thereby preventing the easily solidifying material from solidifying statically and blocking the system.
Thank you all! Also, if a minimum reflux line is set, does the reflux line remain open regardless of whether the flow rate in the process line is normal or at its minimum? Or does the return line open only when the process pipeline is closed or the flow rate is at its minimum?