Problem
FIGURE shows a partially completed diagram of a flow control system. The flow controller is reverse acting and has a 0.2 to 1.0 bar pneumatic output signal which will supply both control valves V1 and V2.
The small range control valve, V2, only needs to operate on the first 25% output change of the controller output signal. For larger flow rates the small range valve will remain fully open and control will be achieved by operation of the large range valve. Note the differing air failure action of the two valves.
Design a system utilising valve positioners which will meet the prestated specifications.
