Another Fieldbus User Disputes Article Focus
Industrial Networking columnist/contributing editor and process control specialist at ISP Lima John Rezabek makes known his displeasure at the content of The Fieldbus Jungle article, written by system integrator Hunter Vegas:
I was dismayed to read IN's latest series of articles by P. Hunter Vegas, where he aims to presumably expose the many pitfalls of Foundationfieldbus, Profibus, and a few other industrial networks. I work in a continuous process plant where all the regulatory control--EVERY throttling control valve--is using Foundation fieldbus instrumentation and networks.
Our operators are not "buried" in alarms - Foundation fieldbus devices do not create alarms for operators by default, "every time an instrument thinks it has a problem" - our operators are only alerted to device problems when it can have an impact on their operation. We are just emerging from a tough, cold winter and our plant manager credits the ability of fieldbus devices to alert us to potential freeze-ups as playing a significant role in keeping the plant running reliably and at near-record rates all winter.
Ironically, after falsely implying that FF devices will bury operators in alarms, in the very next paragraph Vegas says "the failure rate of field instruments is very low". So while that statement is true, he goes on "advanced diagnostics usually won't detect" failures like plugged impulse lines, fouling, or network problems. Where has this man been? Every major supplier's FF DP cell offers plugged line detection. Mag meters and pH transmitters among others have diagnostics for fouling. There are several very effective on-line tools for continuous assessment of network health. He casts aspersions about FF causing plant shutdowns, but says nothing of its real track record or how reliable it really is. Our plant has been making extensive use of control in the field for over 10 years and FF has never been the root cause of a process interruption. On the contrary, it goes a long way to keep us out of the ditch.
Having used fieldbus for over a decade, we routinely replace or exchange devices from the whole period (3 different "ITK" major revisions, from ITK3 through ITK5) without issue. I use diverse devices from numerous manufacturers, including 5 different Foundation fieldbus valve positioners, three different discrete valve positioners, four suppliers of pressure / DP transmitters, radar, ultrasonic flow, pH, conductivity, hundreds of devices from over a dozen suppliers. Fieldbus works. Vegas should come out to Lima, Ohio for a glimpse of reality.
John Rezabek, Process Control Specialist, ISP Lima LLC
Chairman, Fieldbus Foundation End-User Advisory Council
Contributing Editor, Control and IN
[email protected]
The article in question can be read here:
http://www.controldesign.com/articles/2011/FieldbusJungleIN11Q1.html
