The Sequence for the Tank Process For the tank process, you will create an SFC to control the tank discharge. As a way to start and stop the SFC, you will create an SFC parameter called SP that the operator will be able to change. The SP will be manipulated with a named set called SFCCTRL. A named set defines names and equates them to integer values. For the tank example, you will create the named set with two values: 0=IDLE and 1=START. Following is a suggested sequence for the tank discharge application. Step 1:
Stop (that is, set the SP to IDLE).
Transition: Wait for the user to change the SP to START. Step 2:
Put the flow loop in auto mode and set the setpoint to 50 gpm.
Transition: Wait for the regulatory valve to be 30% open. Step 3:
Open the block valve.
Transition: Confirm that the block valve is open. Step 4:
Start the pump.
Transition: Confirm that the pump has started. First, you will create the named set, SFCCTRL, in the DeltaV Explorer. Then you will go to Control Studio to create the module containing the Sequential Function Chart.
To create the named set
1. Open (or restore) the DeltaV Explorer. 2. Select System Configuration | Setup | Named Sets. 3. Point to Named Sets in the left pane, click the right mouse button and select New Named Set from the context menu. A new entry, NamedSetn (where n is the next number available), is added to the end of the list of existing named sets. The entry is in an edit box, ready to be renamed. 4. Type the new name, SFCCTRL, and press Enter. 5. Double-click SFCCTRL (or select SFCCTRL, click the right mouse button, and select Properties from the menu). The Properties dialog box appears.
