By
John Rezabek, Contributing Editor
Itâs like this, you come home to find muddy footprints leading through the family room and learn that the kids let the cable guy in. He exchanged your hardware, lost all your favorites and all those Tivoâd âDancing with the Starsâ episodes you hadnât watched yet. This leaves you with that sense of violation, of having an inconsiderate chucklehead trudge through your treasures and louse a few things up along the way. This is what itâs like when Cletus the Instrument Tech has his way with your DCS at 3 a.m. on a Saturday.
Now, Cletus is an experienced tech with several levels of CCST credentials to his name and cares about doing a good job. But fieldbus has thrust himâmaybe unwillinglyâinto the once-forbidden world of DCS engineering consoles. While fairly decent with the mouse, Cletusâs fingers are less delicate than those of your typical DCS priest, having been shoved in tight places, around sharp objects, doing steam tracing, and occasionally soaked with some less-than-friendly hydrocarbon substance. Heâs good and experienced, but when it comes to seeking out fieldbus diagnostics, methods and function blocks on the DCS console in the middle of the night, this is new territory for him.
Last month I spoke with a process control engineer who works at a big petrochemical complex near the Gulf Coast. Their fieldbus installation is a few years old, but the DCS types still feel as if it was ârailroadedâ in by their field device people. She described a situation in which middle-of-the-night instrument maintenance caused various degrees of mayhem, for example, when her local Cletus put the wrong function block in âout of serviceâ mode. Selecting the wrong block can mean the operator no longer has manual control of an important valve while the maintenance fix is being performed. Operators tend to find this unacceptable!Â
âIâm tired of getting calls in the middle of the night,â she said. âEven if we donât get a call at 3 a.m., finding the âtracksâ of the uninitiated in what we thought were our elegantly crafted control strategies is a lousy way to start the day.â
If youâve begun implementing fieldbus, I hope youâve prepared for the demise of the barriers between field instruments and the forbidden city inside the DCS rack room. Theyâre coming down. If you didnât prepare, I think youâll need to schedule a âgroup hugâ ASAP. There may be some rough seas ahead.
True, digital integration of field devices means the line where the system stops and the field begins âdisappears forever. Iâve been around long enough to have worked before this barrier came to be, when the same discipline and the same engineers did everything from orifice plates and thermowells to field devices to controllers. We sort of cordoned off the DCS back in the 1980s and created the âsystem engineerâ role. While that division may have served its purposeâsaving us from having to train every instrument tech in the shop on the very reliable DCSâfieldbus may take you back to a possibly less comfortable paradigm.
Even our counterparts on the supplier side of process control have issues with this paradigm shift, as field device champions sometimes arenât even in the same time zone as their host-system brothers and sisters. Iâve been asking my favorite suppliers to get their divisions to play nicer with each other for years. There are improvements, but, as in our own organizations, fiefdoms of the old paradigm still linger on.
Before hydrocarbons are coursing through your fieldbus-capable flowmeters and control valves, users will benefit from gathering all the stakeholders from operations, instrument maintenance and control systems and walking through scenarios for troubleshooting and maintenance. Clear procedures, thorough training and a good test bed for practice will help avoid the stress some users experience when theyâve relied too much on OJT (on the job training) or DOE! (do-oops-educate!) If your contract and work practices allow it, involve operations in the commissioning of fieldbus systemsâthereâs nothing like operators to look out for their best interestsâand their comfort and familiarity with the fieldbus infrastructure will pay dividends when âmidnight Cletusâ answers the call-out.