Closed Loop System Logic

Hello all,

I have a question. I am familiar with PID control loops. I have a project I'm working on which is steam control for a batch. I have a heat exchanger and on it I have a control valve and a temp transmitter, but I also have a temp transmitter on the tank. My goal is to have the tank's temp at 180 degrees. Which reading do I use? The Steam_Temp or the Tank1_Temp to use on the PID loop or how would I come up with the logic in order to be successful on this system?

You are trying to control tank temperature. That would be our process variable. Beyond that, I'd have to see a schematic of your system.

I would program a cascade loop with output from tank temp loop driving the setpoint for the steam loop.

baldone said:

I would program a cascade loop with output from tank temp loop driving the setpoint for the steam loop.

Click to expand...

Normally you would have a flow transmitter on the steam.

See link below for more on cascade control..

http://www.controlguru.com/2007/070607.html

Mickey said:

Normally you would have a flow transmitter on the steam.

See link below for more on cascade control..

http://www.controlguru.com/2007/070607.html

Click to expand...

Depends on the system design.
If the Heat Exchanger is on a continuous flow recirculation loop I would do a temperature cascade regardless of flow to prevent overshoot due to loop windup on a single loop on the tank.