Step control

Most are at 50; why do I see the pressure control for one tower at 20? How to set the split points

Let’s take a look at the specific conditions of the two valves

The first 20% of the output from the control valve serves as the 100% signal source for Valve A, while the latter 80% of the output serves as the 100% signal source for Valve B. It’s hard to describe; you can find a detailed explanation of the instrument.

I’ve really never seen 28; usually it’s two valves for 50, and three valves for 33 – it’s generally an average value. What are the advantages of 28, and how should this PID be tuned? One with a small amplitude and the other with a large amplitude; I hope that professionals in instrumentation can help resolve this confusion.

I have a chance to check the instruments to see if it can be fixed? The instruments here aren’t very good

In general, for pressure staging control in a container, valve A is used to add pressure when it is insufficient, while valve B is used to reduce pressure when it is too high. A staging point of 20% means that the 0-20% output of the control valve serves as the 100-0% signal for valve A; the ratio between the control valve’s output and its opening degree is 1:5. When the output is between 20% and 100%, it serves as the 0-100% signal for valve B, with the ratio between the control valve’s output and its opening degree being 4:5. At an output of 20%, both valves A and B are in the fully closed state; as the output signal decreases, valve A gradually opens, while as the output signal increases, valve B gradually opens. There is also a special case where the output is 0%: in this situation, both valve A and valve B are closed. As the output increases, valve A opens first; when the output reaches 20%, valve A is fully open. As the output continues to increase, valve B gradually opens until it is also fully open.