Why this article is important:
- The article highlights Ethernet-APL as the modern successor, offering better capabilities, long-term support and alignment with current supplier investments.
- Many process plants still rely on legacy fieldbus systems like Foundation Fieldbus and Profibus PA, which are becoming unsustainable due to vendor disengagement and diminishing expertise.
- The promise of better diagnostics and condition monitoring through digital networks helps plants avoid costly failures and improve uptime, making a strong case for modernization.
You may have read about Frank in last November’s On the Bus column. He was getting along okay with his decades-old fieldbus installation but was troubled by apathy on the part of suppliers and expertise evaporating through career advancement, acquisitions, and retirements. He found hope for a future migration in the work of the FieldComm Group’s TR10365, outlining a concept for migration of fieldbus to two-wire Ethernet (APL). But a path to future-proof his large installed base of fieldbus devices and networks was still on the drawing board, and he worried about how to justify a migration.
A decade before fieldbus became a viable solution for real process plants, perspectives promoted by contemporary consultants helped their clients see maintenance as a profit center versus a cost. The dynamics between operations and maintenance works best when it isn’t adversarial and requires the maintenance professional to engage in “selling up”—educating his or her customers, peers, and reports on the path to better engagement and understanding of how they can facilitate a profitable relationship.
Read more: A bridge to the future–if you want it
The value of digitization is likely to come from improving maintenance—gaining the ability to detect and foresee potentially calamitous circumstances through process diagnostics, machinery diagnostics and device diagnostics. Inexpensive and often wireless sensors can be added to process equipment—heat exchangers, for example—to track fouling or detect tube leaks. Rotating equipment is fitted with temperature and vibration monitoring. The availability of a fieldbus was seen as a path to further this vision, heightening the visibility of device health.
The issue with fieldbus solutions like Foundation fieldbus and Profibus PA are that they will cease to be sustainable long term. More modern networks—specifically Ethernet APL (the advanced physical layer supporting two-wire Ethernet—are already compelling device manufacturers and systems suppliers to invest in the more capable protocol. You may have noticed the pool of talent in the supplier community has become less deep, just like ours, as corporations strive to remain profitable (by eliminating jobs). Meaning, the best or “remaining people will be focused on the new stuff.
If your facility has a substantial installed base of fieldbus devices, selling the return-on-investment from digitally integrated “intelligent” devices becomes essential to clearing the path to APL. Ignorance of, apathy, or disdain for fieldbus could mean Frank or his successor burdening a future budget with wholesale rip-and-replace of field devices and control system I/O. The footprint of conventional 4-20 mA I/O may exceed available rack room space, as multiple (wire) pairs are needed where fieldbus only required one or two. Even with remote I/O, Frank noted that a substantial investment in new infrastructure and devices would become necessary.
Get your subscription to Control's tri-weekly newsletter.
Frank needs to start selling the virtues of fieldbus and begin years before an investment in migration is immanent. Create some virtues if none are apparent. Organize and prioritize the vast number of devices alarms, applying meaningful alarm thresholds or disabling them entirely. Celebrate the cases—call it a “near miss/hit” if you must—where a device diagnostic helped avoid an upset or abnormal situation. Engage with AI consultants who can devise ways to use machine learning to mine the device intelligence data lake.
For the brave early adopters, migrating to the new protocol may be complicated or expensive. A decade or more ago, Don Bartusiak (then overlord of control systems for ExxonMobil) had dozens of aging proprietary control systems to update. He noted that all migrations were costly, chaotic, and offered zero or negative payback. He and his crew were motivated to strike off on the journey to O-PAS, which today is being deployed on live processes. O-PAS, by design, allows for an incremental migration from the old DCS, preserving all the profitable advanced controls and optimization, and unshackling the process plant from its closed, proprietary, and obsolete platforms. Capital outlay for the migration can likewise be paced to suit the budget and availability of resources. For field devices, APL “Etherbus” has the same promise—we think.
