Control system migration or migraine?

“After realizing that we needed to migrate, we looked at various factors critical to our decision making to determine which product to choose,” relates Fabio Fazio, senior maintenance leader at Petrobras. “Those factors included control reliability, data configurability, network architecture support, plant standardization and safety instrumented system integration.”

Then comes the hard part. Migrators get to listen to the pitches of all the vendors, both first and second tier, as to why they should move to that vendor’s platform, and why it’s distinct from all the others.

Picking a Path is Easy—Sometimes…
Back in the day, Honeywell’s Geismar, La.-based properties were part of Allied Chemical. Now that they belong to Honeywell, it appears that migrating from legacy systems to Honeywell’s Experion PKS systems is gong swiftly and simply. Earlier this year, Honeywell Geismar’s hydrofluoric acid works replaced a 1990s legacy system with a new Experion DCS system in 24 hours, using the facility’s existing wiring. In addition, since Honeywell also makes security systems, as Bill Lessig, Geismar’s plant manager, showed in his presentation at HUG, it was simple to interface the control system to the plant security system and the plant safety system. The point of Lessig's talk was that the integration of process control, building automation, and security systems was the driver for his project. Integration is the key, he noted, because it offers:

• Risk reduction,
• Better preparedness,
• Proactive response,
• Lower total cost of ownership (TCO) due to having one vendor, 
• Easier training, and
• Cost savings due to the ability to share data.

"It may not seem like it, but it is an extremely powerful tool," Lessig adds.

…Except When It’s Not Easy
Duke Power had a much harder choice, since the existing controls were provided by GE, the continuing vendor of its turbines. When GE announced it was phasing out support for its analog control systems, Duke Power had no choice but to look for another vendor. GE offered Duke digital control options, but after a thorough review, Duke chose a redundant control system from Invensys Triconex. “The controller is triple-redundant,” Dempsey says, “so we no longer have a single point of failure.”

Dempsey goes on to describe an important new benefit. “And the box is qualified with the Nuclear Regulatory Commission (NRC) as a safety-related application that can help keep core from melting if there’s a problem. This is several safety levels above what is required for turbine control, but when you consider that the turbine can trip the entire plant, it makes sense to go for the highest quality,” he says.

FIGURE 2: OCONEE NUCLEAR STATION
Duke Power’s Oconee Station was only the second operating nuclear plant to be re-licensed for a second 20-year operation stint.

In fact, the Oconee Nuclear Station was the second operating nuclear power plant in the U.S. to be relicensed by the NRC (See Figure 2). “We knew that introducing more redundancy at key points would enhance reliability considerably,” says Dempsey, “and found that digital technology could provide that redundancy, while at the same time reducing the cost of downtime.”

You also have to evaluate all the options. “It would have been easy just to go with the turbine control system offered by the manufacturer,” adds Dempsey. “However, the Invensys hardware was not only on a par with the other alternatives, but the company also went the extra mile to make sure their system matched our needs. With the other vendors, we would have had to make changes to our plant control system and our cable room, which simply weren’t viable options.”

Changing Horses
One interesting fact is that while many migrations are straightforward moves from an antiquated system made by a vendor to the latest and greatest system by the same vendor, many migrations are not. End-users regularly decide to standardize on a new vendor for upgrades. For instance, Petrobras’ petrochemical plant (San Lorenzo, Argentina) had a typical mix of systems. Built in 1965, the plant had everything from pneumatic controllers and single-loop standalone controllers to outdated systems from the former Fisher Controls and Bailey Controls, now Emerson and ABB, respectively. The plant also had a SCADA system and many freestanding PLCs.

Fabio Fazio reports that the upgrade’s important drivers included high downtime of the existing systems, costly maintenance of the obsolete systems, and the diverse legacy systems, which made it hard to acquire or supervise global business data.

Petrobras investigated products from all the major control system vendors, prior to choosing a Honeywell upgrade path. “The other products we evaluated didn’t even compare,” says Fazio of Honeywell’s product, “in terms of communications, redundancy, architecture and safety system integration features.” Illustrating how important winning a migration contract can be, Fazio adds, “Due to the success of our Experion migration, Petrobras is now investigating other Honeywell solutions.”