Flash drums are equipments widely used in chemical

industry to separate vapor and liquid phases in a single

equilibrium stage. As seen in the figure, the pressure of

the vessel must be controlled by manipulanting the

flowrate of vapor stream. For this control loop;

a$)$ Draw the block diagram including all the transfer

functions with their relevant signals.

b$)$ What is the sign of process gain?

c$)$ Based on the safety considerations, choose the way

the valve should operate, air$-$to$-$open or air$-$to$-$

close.

d$)$ If the transmitter is designed to be direct$-$acting,

choose the action of the controller, direct or

reverse.

Note: To get credit, you should explain the reasoning of

your choices.