Re: [foxboro] PIDA documentation (Was: PH controller in Waste Wat er Treatment)
- From: "Cossitt, Howard" <howard.cossitt@xxxxxxxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Wed, 22 Mar 2006 13:15:03 -0500
I am happy to say that this does exist already.
Our course 2101 (previously CON1), Continuous control includes parameters
from the PIDA block such as the extra MODOPT values as well as use of the
FBTUNE block.
If you don't want to follow the entire 5 day workshop, please note that all
our workshops are designed using the latest instructional design techniques
therefore they are modular. This means that workshops may easily be
tailored to meet your specific needs by concentrating on only those modules
which you require i.e. a 1 day workshop on PIDTAU and FBTUNE.
Please contact the Lifetime Learning Center for enrolment details.
Howard C. Cossitt
National Training Coordinator, Lifetime Learning Center
Invensys Systems Canada
Phone: +1-514-421-8095
Fax: +1-514-421-8059
Email: howard.cossitt@xxxxxxxxxxxxxxxx
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of Corey R Clingo
Sent: Wednesday, March 22, 2006 9:28 AM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] PIDA documentation (Was: PH controller in Waste Water
Treatment)
"This option is seldom used and probably not
well documented,..."
So, how many out there really make full use of the capabilities of the
PIDA block, particularly with regard to self/adaptive tuning
(FBTUNE/FFTUNE, etc.)? Documentation and training on how to do this is
sorely lacking, and I haven't had/taken the time to experiment with it
enough to teach myself. IMHO, this is a 1-day training class Foxboro
ought to offer; The EXACT/PIxTAU/etc. capabilities are distinguishing
features of the I/A system, and Foxboro out to play them up by helping
their customers get the most out of them (especially now that competitors
are adding interesting bits along these lines to their own DCS
controllers).
Corey Clingo
BASF Corp.
"Johnson, Alex P (IPS)" <alex.johnson@xxxxxxxxxxxxxxxx>
Sent by: foxboro-bounce@xxxxxxxxxxxxx
03/22/2006 08:27 AM
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Re: [foxboro] PH controller in Waste Water Treatment
Robert,
I'm not control expert but I've lived with, worked with, and sat next to
lots of them. With that in mind, I'd like to make a couple of comments on
the threads of response that you have received that I think deserve a
comment:
1) There was a comment about the suitability of the PIDA algorithm and our
control block set for various types of process control problems - large
dead
times, long lags, and combinations of both.
The PIDA algorithm when used with the PIDTAU option is quite capable of
dealing with long dead-times. This option is seldom used and probably not
well documented, but if for some reason your process has a long dead time
we
do have a solution in our block.
Long lag processes aren't too bad in general if the DT is short. [Yes,
this
is a general statement and there may be exceptions.]
The real problem is long lags and large dead times. Those problems need
extra help beyond our PID algorithm.
2) General comment on pH control
Here's what I've learned from those who really do understand pH control:
It is really, really easy to design a physical system for pH control that
simply cannot control pH regardless of the algorithm used.
The real issue with pH control is almost always related to the process
equipment. At the end of the day, if the pH in the inflow can vary 2:1,
you
need a range of neutralizing flow that can support a 100:1 change in flow.
That's a bit wide for most flow valves and generally requires separate
tanks
with separate neutralization flows and lots of mixers and so on.
No control algorithm is going to control the pH if the physical equipment
can't meet the process demands.
Are you certain that your physical plant can meet the need?
Regards,
Alex Johnson
Invensys Systems, Inc.
10900 Equity Drive
Houston, TX 77041
713.329.8472 (voice)
713.329.1700 (fax)
713.329.1600 (switchboard)
alex.johnson@xxxxxxxxxxxxxxxx
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