Bubba and the Bus

The Rule of 20: If You Select a Tech at Random from a Group of 20, Can He or She Fix the Problem in 20 Minutes?

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John RezabekBy John Rezabek, Contributing Editor

Mature plants, such as those where most of us in North America work, tend to have a mature workforce as well. Sophisticated instrumentation and control technologies have been coming on the scene for decades. The control professionals, suppliers and consultants who support us have been working with our in-plant stakeholders for all that time, making an effort to make the latest offerings palatable—or at least tolerable—to the people we expect will use and maintain them. Some companies find themselves at a crossroads, where the comfort level of our “Bubbas” is challenged to the point where we hesitate to move forward. This was true with early DCS implementations, and it remains an issue when considering a digitally enabled fieldbus.

Most of us dealt with the onslaught of microprocessor technology by partitioning the scary systems-‘n-software world from the pig-iron world of instrument air and analog 4-20 mA. Only specially ordained DCS-priests were allowed in the rack room or to touch printed circuit boards and configuration consoles, and we strove to replicate what our operators were already using.

My current plant is less than 10 years old, but even back in 1999, we had concerns about whether our operators would use a mouse. Consequently, the first iteration of our operator interface was installed with both mice and touchscreens that would mimic the functionality of a panel-based controller or a first-generation DCS.

Helped by an unwieldy touchscreen calibration method, the mouse and standard QWERTY keyboard became the interface of choice. The ubiquity of the Internet and Windows GUI had made even Grampy Bubba increasingly computer-literate.

Are engineers and front-line supervisors “misunderestimating” Bubba? Field instruments have undergone some major changes, such as the digital integration of field devices. How has Bubba dealt with them? He learned to use handheld configurators, such as the HART 275, Honeywell and other proprietary handheld devices, some third-party devices and even notebook computers.

I was at a refinery in 1993 that replaced 1960s vintage 10-50 mA transmitters with Honeywell DE. It didn’t take long for our techs to appreciate how the new transmitters were making their jobs easier, despite the “new” ways you had to access and calibrate them. The then-modern transmitters had sensors that were corrected over the entire span of operating conditions, and this silicon-empowered design required noticeably less attention.

The span limits of DP cells were much greater, so changing out a “capsule” for a range change was nearly eliminated. DP flow applications kept reading flow even when the DP exceeded the original span, and the transmitter’s configuration was stored in the DCS database, so the need to set the proper calibrated range of any such device was nearly eliminated.

A couple of weeks ago, I heard about the “Rule of 20”: If you select a tech at random from a group of 20, can he or she fix the problem in 20 minutes? I can’t think of many instrument maintenance activities in a process plant that can be completed in 20 minutes—filling out time cards maybe. But the concern is about the bell-curve of achievement that permeates all organizations. How well does the system work when you get an instrument tech on the trailing end?

Early incarnations of fieldbus would have probably failed the “Rule of 20,” but improvements have made usability less of an issue. Systems suppliers are working and investing to make tasks such as replacing a transmitter much simpler. Familiar handhelds, such as the HART 375 and the Beamex MC5, now incorporate fieldbus capabilities. If maintenance challenges have been discouraging a move to digitally integrated field devices, the time may be right to re-evaluate whether your Bubba can make the leap to fieldbus.

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