Reader feedback: May 2018

Readers discuss the OPAF's efforts and Foundation Fieldbus.

OPA is not like fieldbus

Great article (OPA plugs and plays). In case anyone thinks that this is just fieldbus all over again—it is not. The objectives are similar to Foundation fieldbus, but that standard had two major faults: It was directed at new (greenfield) installations, and it had no security at all. This OPA-S effort is directed to provide a fully distributed computing framework for existing devices (brownfield) as well as greenfield, and security is included from the lowest-level DCN or DCF, to the network, to the highest-level RTAC.

In many ways, Foundation fieldbus lives within the function block orientation of the DCN/DCF, but this time OPAF has provided both the ability to add function block capability to existing field instruments with the DCN, and to allow vendors to build new instruments with the DCF (function block engine) built inside.

In case you don't recognize it, this is Fieldbus 2.0 that includes the field instrument in the OPA Communications Framework (the network). Also, this introduces the possibility of connecting Ethernet to field devices, since that is the basis of the OPA Communications Framework.

Richard Caro, CEO, CMC Associates
RCaro@CMC.us

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Different worlds

John [Rezabek], thank you for your reply to my comments (Settling for less). We're looking at the same situation through two very different lenses. I work for a small mining/metal producing facility with definite boom/bust cycles and occasionally thin operating margins. The organization is very flat and our headcount is kept lean. We don't have the option of hiring E&I employees with significant experience. We bring in people fresh out of school, and then train them on site. Within five to seven years they become very effective—and then they leave.

We are located close to a number of refineries. Refineries tend to print money, have large operating budgets, and can afford to pay top dollar for the best of the best. They only hire experienced people, and they're almost certain to hold onto those people for the rest of their careers. For a refinery, it makes sense to expend the time and effort to develop their people to the very pinnacle of the technology.

They have the budget, numbers, time and technical acumen to ensure that a Fieldbus solution will succeed. For us, the situation is very different. Our daily task is keeping the lights on using a small number of predominantly rookie employees. Those who have been trained and are fully effective can't be counted on to stay. Greener pastures beckon, and they will leave.

We deliberately avoid Fieldbus because we know that we don't have (and won't have) the human infrastructure to maintain it. The solutions we implement may not be as high-tech as a state-of-the-art Fieldbus installation, but they do everything we need them to, and when they break, our people have the skills to fix them quickly.

I suspect that our situation is more common across the U.S. than yours. When a pinnacle installation berates the rest of us for not joining in the Fieldbus revolution, they don't seem to realize that they're very much like Marie Antoinette exclaiming "Let them eat cake!" Fieldbus isn't dead, but for most of us, it just isn't a good fit.

Martin R. Davis
E&I Manager, US Magnesium, LLC

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