Drum Level Control

Take a look here...

http://www.controlguru.com/wp/p44.html

If you have any questions, feel free to ask!

_{(isn't google great?!)}

Sir thanks for the answers. but two more doubts i want to clarify---

1- What is the calculation among (A)durm level, (B)feed flow & (C)steam flow to meet the set point for the feed control valve? f(A,B,C) = ??

2- what type of control is taking place here, PID or only PI and why?

A1: Corrective action = gain x (error + (integral error with respect to time divided by integral time constant) + (derivative time constant multiplied by rate of change of error))

A2: PID. One can always turn off the derivative term if needed.

Three elements are the level of drum, feed water flow and steam flow.

The concept is to achieve feed water flow equal to the steam flow so as to compensate the amount of water to be added in the drum.

Three elements control is in cascaded mode. One controller is based on pressure compensated level of the drum as process variable.

Steam flow data is in feed forward control and add to the output of first controller then feed to the second controller as Setpoint (SP) to be the reference of feed water flow as PV.

the output of the second controller will drive the Feed water flow control valve.

Control algorithm is PID but usually derivative term is off.