Re: [foxboro] foxboro Digest V5 #150
- From: Rguercio@xxxxxxx
- To: foxboro@xxxxxxxxxxxxx
- Date: Thu, 28 Apr 2005 22:51:35 EDT
In a message dated 4/28/05 10:45:42 AM Mountain Daylight Time,
foxboro@xxxxxxxxxxxxx writes:
foxboro Digest Thu, 28 Apr 2005 Volume: 05 Issue: 150
Dear Fellow Foxboro Freelisters (FFF),
I acknowledge up front that this kind of posting might not have a legitimate
place on the Foxboro Freelist, but I'm going to take the chance anyway as a
consultant who specializes in Foxboro I/A who has just completed some recent
experience with one of Honeywell's (recent) offerings. Those of you who
don't want to read comments about Honeywell's Plantscape please stop reading
here.
I just wanted to pass on some things that may make you more happy about your
companies' decisions to use the Foxboro platform. I am just finishing up a
consulting trip to Equatorial Guinea, West Africa helping Marathon startup
and commission their onshore gas plants and offshore platforms. The system is
a Plantscape 500, and I am helping commission and tune control loops and do
some revision on the control strategies.
We found several applications ideal for GAP and NON-LINEAR pida controllers.
The changeover was painless and bringing up the new controllers seemed
really slick - they operated "right out of the box" and with minimal tuning
seemed to do a great job. After several days, however, we kept seeing
anomalies:
long periods of superb control, then the controllers seemed to go wacko.
The short story is that due to the equations used and how they were
implemented, anytime the (PV-SP) went EXACTLY to zero, the controller seemed
to lose the
sign of its gain and would go beserk, sometimes recovering, sometimes not.
We really wanted them to work, so we investigated the various PID equation
options, etc, off and on over a week's period. Still the mysterious crashes.
Finally called TAC, and while the representative immediately acknowledged
the problem and expressed personal regret over it, said that Honeywell's
position was that they were not providing patches for our system because it was
now
obsolete. Bear in mind that this system was purchased about 2 years ago, is
just coming online, and yet is considered obsolete enough not to fix
problems with basic advertised functionality. I asked what was someone to do
if
they wanted to go GAP or NON-LINEAR, and the answer was "write your own".
This
attitude floored me. Yes, I am capable of doing that, and even have my own
advanced level controller written for Foxboro, but Honeywell's arrogance was
amazing. We all know that I/A has its share of problems and outstanding
CAR's, but I've never experienced the arrogance from TAC nor especially from
Foxboro reps like Alex Johnson like I did from Honeywell TAC. Anyway, sorry
for
this aside, but thought some of you might get a kick out of it - and if any of
you have close Honeywell contacts, you may want to tease them with it.
Rick Guercio, RG Consulting
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