Logical Control Programs Anchors Aluminum  Scott Dombrowski Robert Chockley

Example One Logical Controls –IF, THEN, WHILE –Constantly being monitored Reboiler –Used to cool process streams –Phase Changes –Water turns to steam

Reboiler Diagram

Operating Condictions T1 is 300 o F T2 is 150 o F F1 is 20 gal/min F2 is 10 gal/min P1 is 150 psi F3 is closed

Possible Conditions to be Controlled What control logic should be used to return the system to normal operating conditions for each case? 1.T2 reaches 200 o F 2.T1 reaches 350 o F 3.P1 reaches 200 psi

Solution Case 1 If T2>=200 o F, THEN F1 = 30 gal/min If T2>=200 o F, THEN F2 = 5 gal/min

Solution Case 2 IF T1 >= 350 o F, THEN F1 = 30 gal/min IF T1 >= 350 o F, THEN F2 = 5 gal/min

Solution Case 2 (More Complete) IF T1 >= 350 o F, THEN F1 = 30 gal/min, ELSE F1 =20 gal/min IF T1 >= 350 o F, THEN F2 = 5 gal/min, ELSE F2 = 10 gal/min

Solution Case 3 IF P1 >= 200 psi, THEN F1 = 30 gal/min AND F2 = 5 gal/min WHILE P1 >= 200 psi for >= 5 min, IF F1 = 30 gal/min and F2 = 5 gal/min, THEN F3 = open, F2 = 0 gal/min