Re: [foxboro] cascade/constraint control

Greg,

Another option if you wish to reduce the number of blocks you build.

You can do as Joseph Riccardi mentioned but instead of having a SIGSEL
or OUTSEL block just connect the TC to the HOLIM parameter of the FC.

Follow Joseph's suggestions as far as FBK & BCALCI of the TC, connecting
it to the AOUT instead.

Michael L. Jaudon
TRONOX, LLC
(Technology Group-Hamilton, MS)
(662)343-8710 Office
(662)304-0313 Cell
mike.jaudon@xxxxxxxxxx

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-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Joseph M. Riccardi
Sent: Tuesday, October 23, 2007 10:23 PM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] cascade/constraint control

From memory...  If you want a smooth transfer between the LC and TC, and
you
want to prevent the controller not selected from winding up/down,
connect
the FBK parameter of each block to the output of the SIGSEL, or OUTSEL.
The
controller not selected will track the controller selected, with an off
set
equal to the proportional error.


Joseph M. Riccardi, Inc.
DCS Services - Industrial Process Control
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Joe@xxxxxxxxxxxxx
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"To give real service you must add something that cannot be bought or
measured with money; and that is sincerity and integrity." - Donald A.
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-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On
Behalf Of Gregory A Hurwitt
Sent: Tuesday, October 23, 2007 4:07 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] cascade/constraint control


I have a control scheme that will normally run as level-flow cascade.
If
the temperature of the downstream equipment falls too low, then the flow
must be restricted.  I plan to use a constraint control scheme:


+-----------+            +-----------+             +-----------+
|           |            |           |             |           |
|    LC     | -------->  |   SIGSEL  |  -------->  |    FC     |
|           |            |   (low)   |             |           |
+-----------+            +-----------+             +-----------+
^
+-----------+                  |
|           |                  |
|    TC     | -----------------+
|           |
+-----------+

What are the recommended FBK and BCALCI connections for the LC and TC?
How
do I ensure that the TC does not wind up while it is not selected?

________________________________________________________________________
____
__________


Greg Hurwitt
Engineering Associate

E-Mail:  gregory.hurwitt@xxxxxxxx
Postal Address:
BASF Corporation
602 Copper Road
Freeport, TX 77541
USA

BASF - The Chemical Company

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