Re: [foxboro] foxboro Digest V5 #150

 
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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