Objectives Upon completion of this module you will be able to define
The application of a Sequential Function Chart
The execution of a Sequential Function Chart
Steps in a Sequential Function Chart
Actions in a Step
Action Qualifiers in a Step
Transitions Named Sets for Sequential Function Chart
8-3
Sequential Function Charts
SFCs are used to control time/event sequences. For example, the startup/shutdown sequence for a piece of equipment. SFCs consist of
– Step - Executes action(s) – Transition - Determines when to proceed to the next Step based on an expression being evaluated as TRUE – Terminations - Special symbol that represents the end of a sequence
8-4
Step Actions There are three types of Step Actions:
Assignment - Assigns the result of an expression to a destination
Boolean - References a module-level Boolean parameter
Non-Boolean - References a function block
8-5
Action Qualifiers
8-6
Action Qualifiers There are two types of Action Qualifiers: Non-Stored action qualifiers are only active while the associated step is active or a portion of the time the step is active.
N (Non-Stored) - Only active when the step is active. R (Reset) - Active on the first scan through a step. Used to stop a stored action. L (Time Limited) - Only active when the step is active. Also, you can specify the action to be “active” for a maximum time or based on an expression. D (Delayed) - Only active when the step is active. Also, you specify a delay based on time or an expression before the action becomes active. P (Pulse) - Executes the action once based on a delay time or an expression.
8-7
Action Qualifiers Stored action qualifiers may be active for only a portion of the time that the associated step is active or they may remain active after the associated step has become inactive depending on the specific qualifier.
S Set (Stored) - Active when the step becomes active and stays active until it is reset. SD (Stored and Delayed) - Active after a delay time or an expression evaluated “true” when the step becomes active and stays active until it is reset. DS (Delayed and Stored) - Active after a delay based on time or an expression when the step becomes active and stays active until it is reset. If the step goes inactive before the time delay is up, this action will not go active. SL (Stored and Time Limited) - Active when the step becomes active and stays active until the configure time has elapsed or expression is evaluated “true”. 8-8
SFC Execution Valid divergence and convergence include:
Divergent Paths
Sequence Select Convergence
8-9
SFC Execution
Parallel Divergence
Parallel Convergence
8-10
Adding an Action to a Step
Add Actions by selecting Step placing the positioning selector in the Action window right mouse clicking Add . 8-11
Defining Action Properties
Select Action right mouse click Properties to modify or define an action. The Expression Assistant launches the Browser . 8-12
Defining Transition Properties
Select Transition right mouse click Properties to modify or define the transition condition. The T1 Properties dialog box appears. 8-13
Workshop - Using SFCs This workshop requires you to perform the following tasks: Task 1.
Create a Named Set which will be used for operator interface to the SFC.
20 = WAITING FOR BLK VLV TO OPEN 30 = WAITING FOR FLW VLV TO OPEN
Open the block valve XV-101 Update the operator with message 20
SET FLOW RATE
40 = WAITING FOR PUMP TO START
Set the flow rate to 50 GPM FIC-102 Update the operator with message 30 Wait for flow valve to be > 30 % open
START PUMP
Start pump MTR-102 Update the operator with message 40 Wait for pump to start
8-15
Workshop - Using SFC-T101 Step 1.
Create Named Set NS-T101 using DeltaV Explorer.
8-16
Workshop - Using SFC-T101 Step 2.
Modify Properties and add names and values as shown below.
Named Set NS-T101 ( Name- Case sensitive) 0 = SELECT SEQ 10 = STARTUP 20 = WAITING FOR BLK VLV TO OPEN 30 = WAITING FOR FLW VLV TO OPEN 40 = WAITING FOR PUMP TO START
Visible Yes Yes Yes Yes Yes
User Selectable Yes Yes No No No 8-17
Workshop - Using SFC-T101 Step 3.
Use Control Studio to create Sequential Function Chart SFC-T101. Select New. Change the Algorithm Type to Sequential Function Chart.
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Workshop - Using SFC-T101 Step 4.
Create parameter MESSAGE (Named Set, NS-T101).
Step 5.
Create Sequential Function Chart using Steps, Transitions and Terminations from the All SFC Items Palette. ‘MESSAGE’ := ‘NS-T101:SELECT SEQ’; STOP SEQUENCE
‘MESSAGE’ = ‘NS-T101:STARTUP’ OPEN BLK VLV
Open the block valve XV-101 Update the operator with message 20 Wait for the block valve to open XVSTAT-101
SET FLOW RATE
Set the flow rate to 50 GPM FIC-102 Update the operator with message 30 Wait for flow valve to be > 30 % open
START PUMP
Start pump MTR-102 Update the operator with message 40 Wait for pump to start
8-19
Workshop - Using SFC-T101 Step 6.
Assign the SFC to your controller.
Step 7.
Save and download the SFC.
Step 8.
If an algorithm error occurs, use the
Step 9.
Add the MESSAGE parameter to operator display Tank101 with Data Entry set to In-place.
button to check the SFC.
Step 10. Verify that the sequence executes properly.
Note: Remember to download Changed Setup Data.
8-20
Action Properties (General Tab)
Delay allows you to define a time or an expression you want satisfied before the action is executed. When the time has lapsed or the expression has been evaluated TRUE , the action will be performed. Note: The delay does not hold the step. 8-21
8-22
Action Properties (Confirm Tab)
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Action Properties (Confirm Tab) If you add a Confirm to an Action, you must configure the transition or termination that follows to an expression that allows for the confirmation to complete.
CONFIRM_FAIL — set whenever an action has a confirmed timeout before the expression used in confirming becomes TRUE. FAILED_CONFIRMS — the number of actions on the step that have failed to confirm. PENDING_CONFIRMS — the number of actions on the step not yet confirmed or failed.
8-24
Workshop - Modifying SFC-T101 This workshop requires you to perform the following tasks: Step 1.
Modify NS-T101 to display shutdown messages for operator interface to the SFC.
Step 2.
Modify SFC-T101 so it will Startup and Shutdown Tank101 using divergent paths as shown below.
Step 3.
Download the SFC.
Step 4.
If an algorithm error occurs, use the
Step 5.
Verify that the sequence executes properly.
button to check the SFC.
8-25
Workshop - Startup & Shutdown STOP SEQUENCE
Wait for STARTUP command OPEN BLK VLV
Wait for SHUTDOWN command
Open the block valve XV-101 Update the operator with message
STOP PUMP
Wait for block valve to open XVSTAT-101
SET FLOW RATE
Set the flow rate to 50 GPM FIC-102. Update the operator with message
Wait for pump to stop
CLOSE BLK VLV
Start pump MTR-102 Update the operator with message
Wait for pump to start
END SEQUENCE
Close block valve XV-101 and, using the Confirm tab, verify block valve XVSTAT-101 is closed. Update the operator with message
Transition on Pending_Confirms = 0
Wait for flow valve to be > 30 % open
START PUMP
Stop pump MTR-102 Update the operator with message
Set the mode of FIC-102 to MAN. Set OUT of FIC-102 to 0% using Pulse Delay CLOSE FLOW VLV Expression to verify actual mode = MAN. Update the operator with message Wait for flow valve to be < 2 % open
