How to read simple control loops on a PFD (Process flow diagram)


Control loops on a PFD identify areas where variable must be properly maintained.

Main variables controlled in a process.

T - Temperature
P - Pressure
L - Level
F - Flow rate

Example of s simple control loop

What will be indicated
1.What kind of controller is being used

2.Where the controller is receiving its signals

3.How the controller is controlling the variable (valve,variable power supply)

How to read a control loop from PFD

Here Temperature controller is used. Pneumatic signal is used to give the controller output to final control element.