Re: [foxboro] cascade/constraint control
- From: "Schouten, Frits JF" <Frits.Schouten@xxxxxxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Wed, 24 Oct 2007 11:28:44 +1300
Hi Greg,
we've done something simular with flow and pressure control.
Var. setpoint--+ BCALCI<------BCALC1
| | |
Flow AIN-->PIDE----->| |
|OUTSEL----->AOUT(valve control)
Pressure AIN-->PIDE----->| |
| | |
Fixed setpoint-+ BCALCI<------BCALC2
In our case we need to maintain a minimum pressure. OUTSEL is set to
pass the highest output to the AOUT.
The pressure PID block has a fixed setpoint based on a minimum pressure.
The flow PID block setpoint is based on flow demand.
As the demand for flow is dropping, the valve closes, which will cause a
reduction in pressure. This will result in a higher output on the
pressure PID block, forcing the valve to maintain a position that
retains the minimum pressure.
I'm sure something like the above can be done with flow and temperature.
Cheers,
Frits Schouten.
NZSteel
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Gregory A Hurwitt
Sent: Wednesday, 24 October 2007 9:07 AM
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
=20
=20
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
=20
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Djoin
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Dleave
=20
=0A=0ANOTICE - This message and any attached files may contain informatio=
n that is confidential and intended only for use by the intended recipien=
t. If you are not the intended recipient or the person responsible for de=
livering the message to the intended recipient, be advised that you have =
received this message in error and that any dissemination, copying or use=
of this message or attachment is strictly forbidden, as is the disclosur=
e of the information therein. If you have received this message in error =
please notify the sender immediately and delete the message.
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
Other related posts:
