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RE: [EXTERNAL] [EE365 Train & Develop Group] Cascading with the Calc block

The post will not let me reply to it in the exchange365 portal – so I hope this makes it to the right place:
 
The description above makes it sound like you are working with discrete valves – is that right?
 
Your description does not sound like a cascade strategy as you are setting the valves based on the PID PV, not the PID Output. Can you explain more what you mean?
 
Thanks,
Brian
 
Brian Hrankowsky
Eli Lilly and Company
Lilly Corporate Center
Indianpolis Indiana 46285
317-651-1455
hrankowsky_brian@lilly.com
 
From: Barrick_JA [mailto:bounce-Barrick_JA@emersonexchange365.com]
Sent: Thursday, July 20, 2017 12:38 PM
To: TrainAndDevelop@emersonexchange365.com
Subject: [EXTERNAL] [EE365 Train & Develop Group] Cascading with the Calc block
 
Update from Emerson Exchange 365
 

So I'm new to DetlaV, having spent most of my automation career in a Ladder Logic/Rockwell Automation environment. I'm trying to cascade two FCVs, one primary, in order to fill a tank. I'm using XFR and CALC blocks as my input to my PID for the main FCV with a simple expression:  

IF 

'TANKLEVEL/PID1/PV.CV' >75 THEN 'OUT1>CV' := 0

ENDIF;

IF

'TANKLEVEL/PID1/PC.CV' < 45 THEN 'OUT1.CV' := 1

ENDIF:

For the other FCV, I'm using this:

IF

/TANKLEVEL/PID1/PV.CV' < 60 AND 'TANKLEVEL/PID1/PV.CV' > 75 THEN 'OUT1.CV' := 1;

ENDIF;

IF

/TANKLEVEL/PID/PV.CV' < 45 THEN 'OUT1.CV' := 0

ENDIF

The control philosophy is basically this: IF TANKLEVEL >75 then SECONDARYVALVE = CLOSED and PRIMARYVALVE = CLOSED

Else, if TANKLEVEL < 60 and > 45, then PRIMARYVALVE = OPEN and SECONDARYVALVE = CLOSED

Else, if TANKLEVEL < 45, then PRIMARYVALVE = OPEN and SECONDARYVALVE = OPEN

Appreciate any assist here...am knee-deep in learning DeltaV.

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