Control loop configurations for chemical process variables

The different control loop configurations for different process variables are given below.Its just the simplest configurations used in control systems.


1. Level control.

Figure: On-off level control loop.

Figure. Control loops for continuous level control.
a - by the control of an inlet stream; b - by the control of an outlet stream;
c - cascade control loop.

Figure:  Level control in evaporator.


2. Pressure control

Figure: Pressure control loop for evaporating unit.
1, 2 - evaporating units; 3 - barometric condenser.

Figure: Pressure control in the distillation column.
1 - distillation column; 2 - reflux column; 3 - reflux tank;


3. Temperature control

Figure: Single loop control system for a stirred tank.

Figure: Single loop control system for heat exchanger.

Figure: Cascade control system for heat exchanger.


4. Flow control

Figure: Flow control by throttling the stream after the centrifugal pump.

Figure:  Flow control using by-pass pipe-line in the case of the piston pump.


5. pH control

Figure: pH control system.


6. Composition control

Figure: Feedback system for composition control.

Figure:Inferential system for composition control.


Note: Click on the image to get an enlarged view.


Article Source:: Dr. Alexander Badalyan, University of South Australia