Could an expert please explain the meaning of the logic behind the instruments below?
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This post was last edited by wck139064 on 2020-12-21 22:22
The first diagram shows the cascade control of level and flow rate; there are two control loops for the flow rate, and the level can be used to form a cascade control with one of them. Figure 2 shows a combination of step regulation and selective control. Split is a path divider controller, and low select is a low selector.
Could you explain how to implement the control specifically?
For the level-skipping in the first image, it depends on the situation, right? If hydrogenation is carried out using two feed lines for the same type of raw material, then the liquid level controls the flow rate, and the flow control valve adjusts its opening degree; there is also a certain ratio between the two streams, for example 4:6. When the liquid level is low, the flow rate increases, causing the control valve to open more, with both valves adjusting proportionally. It depends on the design specifically
You want to drive the guy upstairs crazy; everything that contains a ‘Y’ implies logical calculation. For the first cascade, it’s a level-cascade flow control system – there is a selector switch: one can choose to use level-cascade with FIC10103A, or level-cascade with FIC10103B; it depends on which one is selected； Secondly, there is a problem: when choosing the lower value, the value obtained from PIC10801A and the value obtained from PIC11201 are considered; the lower one is used to control PV10047. However, when PY10801A outputs a range of 0-100%, it becomes 100-0% – this shouldn’t be referred to as scaling; rather, it’s an output signal that is used for feedback control. What follows are the signals generated after segmentation; some of them are used for control, while others serve as low-level selection signals for control purposes.