Dear instrument control experts, how should this control loop be understood?
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As shown in the figure below, 1. The tank level LIT is set at two levels – high and low – to control the start and stop of the pump; then can a signal be sent to make the regulating valve ahead also start and stop simultaneously? Is there a sequence, and is it necessary? 2. What level of precise control can this control valve achieve? Add a flow meter ； Regarding the relationship among level gauges, flow meters, and control valves, I’m wondering: should the liquid level reach whatever level is set? What is the control flow?
Bro, I can’t understand the diagram. . . . . . . . . . . . . .
Control serves the process; it is necessary to first understand the requirements of the process.
The valve opens to start the pump, and the valve closes when the pump stops; it follows this sequence, but with a delay of just a few dozen seconds； Liquid level cascade control will suffice. As for flow rate, it can be added at the inlet or not; if it is to be added, it should be placed after the pump
It is personally recommended to add a bypass next to the control valve to facilitate its maintenance
Then I would like to ask, aside from starting and stopping the pumps for controlling the high and low liquid levels； Can I set the start and stop of other level-controlled pumps? Is it necessary to add a flow meter in this situation?
The flow meter you mentioned can be added or not; what are the benefits of adding it?
Yes, the feed can be monitored based on the liquid level. If there are users using the storage tank, a flow meter can be installed at the pump outlet for monitoring or measurement; however, if high precision is not required, this flow meter can be omitted
Adding level control makes it more precise; it’s possible to use a cascade configuration
The process is unclear, so no conclusion can be drawn. . .
Precise control of the liquid level is not required; the high-level pump can be used to start operation when the level is high, and at low levels