Come Glimpse Reality
I was dismayed to read Industrial Networking's series of articles by P. Hunter Vegas ("The Fieldbus Jungle," www.IndustrialNetworking.net/fieldbus11q1), where he aims to presumably expose the many pitfalls of Foundation fieldbus, 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 detects a problem"); our operators are only alerted to device problems when they 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 instrumentation is very low." So while that statement is true, he continues, "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 online 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 more than 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 more than a decade, we routinely replace or exchange devices from the whole period (three different ITK major revisions, from ITK3 through ITK5) without issue. I use diverse devices from numerous manufacturers, including five 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 more than 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, www.ispcorp.com
Chairman, Fieldbus Foundation End-User Advisory Council
Contributing editor, Control and Industrial Networking
A More Encouraging View
I was somewhat surprised with respect to the rather "dark" view of digital instrumentation and controls upgrades in the article. The author dwelled far too long on the peculiar pitfalls of digital upgrades while missing significant benefits regarding the digitalization of the process control industry. There are particular benefits that might not be as important to some areas of the process control industry, but are of particular and very important benefit to my specific area of I&C. My particular area of expertise is that of instrumentation and control systems for nuclear power plants.
To its credit, the article did identify a number of the problem areas Duke Energy/Oconee experienced with its first Foundation fieldbus-based installation. However, the second and third installations, as well as subsequent smaller additions to the FF system, have been very straightforward and implemented efficiently. Far too much focus was paid to the difficulties, and not enough encouraging or beneficial operating experiences were provided to mitigate the trepidation-based arguments that many uninformed people and organizations offer to endure their obsolete systems or undertake heroic maintenance of the status quo (analog and pneumatics) with respect to power industry process instrumentation and control systems.
The Oconee Major Projects Engineering organization implemented many digital upgrades at the Oconee Nuclear Station and the Keowee Hydroelectric Station between 2003 and 2009. Oconee Nuclear Station's three units began generating in 1973 and 1974. The I&C used is of that timeframe. Oconee today still has many pneumatic and analog I&C process loops, but Oconee is also one of the most digital nuclear power plants in the U.S. Digital systems are the future for power generation, whether an existing plant or a new one, and regardless of the fuel or energy source utilized. Duke Energy has implemented many digital upgrades within its nuclear fleet—most driven by obsolescence issues and a desire for improved performance, monitoring and reduced maintenance.
Michael H. Miller, PE, Oconee Nuclear Station,
Sargent & Lundy, www.sargentlundy.com
A Digital World
I think that the article on Foundation fieldbus misses the point, some key issues, and one unalterable truth. Everything is going digital in this world. Much of what we know of the world today, in spite of the complications, is better and provides value beyond initial cost. Ask any iPhone or BlackBerry user if they would give them up despite the huge upfront cost and the even larger ongoing data plan costs.
What I find almost trivial is the somewhat irrelevant discussion around initial costs. I really didn't need a lot of research to know that if I buy something that has an order of magnitude of choices, the engineering costs would go up. Our first fieldbus project cost us almost three times the cost per I/O of a traditional 4-20 mA loop in a DCS. Our second project cut that cost per I/O in half. I don't believe we will ever reach parity because there always will be more choices. We'll get better at using templates and configurators and software gizmos to automate things because now we can. But if the cost per I/O was the only issue, pneumatics were pretty cheap compared with a DCS project 20 years ago.