Control of pump outlet flow rate

This is a mechanism for protecting the flow rate at the pump’s outlet. It regulates the outlet flow rate normally; when the flow rate drops below the minimum value, the return line is activated, so that the flow rate through the return line plus the flow rate at the outlet equal the pump’s minimum flow rate, thereby protecting the pump equipment. Without a sequential logic diagram, one can only guess

Thank you! This is the lack of a control logic diagram. I would like to ask how this logic is controlled when the traffic increases from low to high?

This post was last edited by Hansonwen on 2018-6-27 at 14:21. If the interlock control is designed in accordance with the HG standards, the signal indicated by the graphic symbol “∑” for the signal processing function can be understood as the sum of the flow parameters from two orifice plate flow meters; this signal is used to control the opening degree of the control valve FV-20501 on the minimum flow protection line. When the summed flow rate (i.e., the total flow rate) is below the minimum flow setting, the protection line control valve opens; the opening degree of the main line control valve is 0%. Moreover, the lower the value resulting from the detection and calculation, the greater the opening degree of the protection line valve ； When the sum of the detection values is higher than the minimum flow setting, the opening degree of the protection line control valve is 0%, while the outlet main line control valve opens; the higher the calculated sum, the greater the opening degree of the main line control valve. Under accident conditions, the main line control valve closes, the protection line control valve opens fully, and the pump operates in reverse flow.

Are pump backflow protections already this advanced these days? Previously, a flow-limiting orifice was simply added to the protection line; at most, an orifice flow meter was installed on the pump outlet main pipe, and its flow signal was used directly to control the adjustment valve of the protection line, with no calculations being performed ； This has been made too complicated.

The Lummus process package was used, with no modifications to their controls. As mentioned on the 6th floor, it’s not commonly designed this way in China; it’s a bit complicated. Thank you very much for the description on floor 6; it’s extremely clear.

Many process packages abroad are done this way; it’s not complicated, it’s just that you’re encountering it for the first time. The previous replies were either incorrect or incomplete; for example, what was said on the sixth floor was half correct while the other half was wrong. Generally, larger pumps are equipped with a minimum flow protection feature; this value is usually 30 percent of the normal design flow rate. When the flow rate controlled by the main material supply falls below the pump’s minimum protection flow rate, the minimum return control valve opens to ensure that the total outlet flow rate of the pump remains above the minimum flow level. After the minimum flow valve is opened, the main material flow control valve will not be closed to zero as mentioned on the sixth floor. Rather, both control valves are controlled according to their respective PID controllers, and it is by no means the proportional control mentioned earlier.