DCS migrations: Opportunity for improvement, or operational disaster

When planning a distributed control system (DCS) migration, some of the old can be retained, but don’t go too far. Training is critical to a smooth and safe transition.


Imagine this distributed control system (DCS) migration project situation: the timeline is well along to the point that the new system vendor has been chosen and a system integrator brought on board to help with the mechanics of the project. Everything seems to be on track; at least until the owner's operations manager drops a bomb during the project update meeting.

"We've been discussing this whole situation internally," he says. "We're excited about the system, but we have one major concern. We have to avoid losing any production so we're going to do a hot cutover, as we've all agreed. But our upper management is concerned about the operators. Based on the discussions coming out of our human-machine interface (HMI) design team, we are afraid of having to launch a large-scale training program as the new system comes online. We want to retain and reuse all the HMI screens and graphics from the current system so all the operators will be familiar with how things work from the get-go. This should reduce the need for training and avoid any problems with the operators supporting the project." The DCS vendor's rep and the project lead from the integrator exchange sidelong glances. Neither wants to speak first. After a pregnant silence, the integrator says, "I understand what you're trying to do, but I do not believe what you're suggesting is practical or even ultimately desirable."

Nobody at the table moves a muscle.

The integrator continues, "Think about it. Many of your HMI screens date back to the initial installation more than 20 years ago. Sure, some have been updated, but they were minor changes and only reflect equipment configuration modifications, not new control strategies. They work with the existing system, certainly, but they aren't very good. Trying to integrate them with the new platform will require a huge amount of custom code writing, and nobody put that in the budget."

No one else challenges his assertion, so the integrator presses his point further. "The idea is also very shortsighted." The ops manager sniffs, but the integrator is unfazed: "Your desire to avoid training now puts you in a situation where you won't realize many of the gains to be made with the new system. Such a decision will cost more now and haunt you for years to come. If you don't bite the bullet and do the training now, you'll regret it. Maybe not today, maybe not tomorrow, but soon, and for the rest of the system's life." 

A legitimate concern, but the wrong solution

Both sides in the scenario have a legitimate point. A DCS migration, particularly one in which a new platform is introduced, requires much thought and can unleash a variety of problems if not executed well. Training is a significant issue and should be approached carefully. If the operators do not know what to do to maintain normal operation, much less start up a unit, correct a process upset, or other abnormal situation, disaster can follow. (See migration sidebar linked below.)

At the same time, the integrator's lead makes an equally important point. Going through all the pain and suffering of a full migration or major upgrade without embracing all the benefits is regrettable. Channeling Rick's appeal from Casablanca may have been over the top, but the plant management got his point. Imagine a company that has not upgraded its office equipment in 30 years. All its people are still working on IBM PC XTs using DOS-based WordPerfect 4.0 and daisy wheel printers, selected because they look like text from a typewriter. No e-mail. No Internet. When the time for an upgrade finally arrives, would the users insist on trying to make today's Microsoft Word with all its graphic capabilities look and work like the old system?

New control platforms bring many improvements in their ability to interact with operators, or at least they can. The improvements are not automatic, but the means to implement them should be.

Process control strategy with HMIs

The screens that operators watch in the control room are their window into the process. Short of going out into the unit and looking inside the equipment, they have no other mechanism to know what is happening in all those pipes and vessels. Going back 20 or 30 years, HMI designers thought operator screens should look like a piping and instrumentation diagram (P&ID) because that's how people conceived the process. Insert boxes at key points displaying specific process variable values, and that does it.

Fortunately, some clever people recognized the connection between human error and safety incidents and asked if that approach really worked. They began asking questions of what operators need to know to control the process. The concepts of situational awareness began to emerge as groups like the Abnormal Situation Management Consortium (ASM) and Center for Operator Performance identified what really needs to happen to keep a process unit on an even keel. The design concepts of what operator screens need to look like changed driven by studying what the operators need to know. It wasn't so much a change in look as it was a change in function. (See high-performance HMI sidebar linked below.) 

Making it work

Undertaking such a project requires a lot of analysis during the design phase. Looking at the recommendations offered by the organizations just mentioned is a good place to start. Operators and the designers creating the new system need to go through all the existing HMI screens one by one dissecting them to determine what is useful and what isn't. Is all the information necessary to execute a routine function available in one place? Are two variables that depend on each other both visible on the same screen? How much time does an operator use flipping between screens during a startup or grade-change procedure? When these kinds of questions get sorted through, things will begin to make sense.

The problem is, it all takes time. This kind of analysis has to be done, it has to be incorporated into the new system, and the operators need to be trained. Everything may make more sense and be more intuitive, but they still have to understand how it all works to be comfortable running the plant. The operations manager at the beginning of the story probably has a sense of what it all involves and is reluctant to face the reality, but his solution is not the right approach.

Peter Welander is a contributing content specialist for Control Engineering. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra@cfemedia.com.


Key Concepts

  • Training is crucial when planning a distributed control system (DCS) migration.
  • New control platforms have the ability to interact with operators.
  • Operators and designers need to go through all the existing HMI screens to determine what is useful and what isn't.

Consider this

What other steps can operators and designers take to make sure that DCS migration is a smooth process?

ONLINE extra

See related sidebars on DCS migrations and high-performance HMIs linked below.






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