Controls and process applications can be restored

Restoration possible: Many distributed control systems (DCSs) are rapidly aging and risk breaking down. Luckily, there are many tools and innovative methods for supporting and breathing new life into controls and process applications

By Jim Montague

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Youth may be wasted on the young, but there's no reason you and your control systems and process applications can't regain and maintain some youthful strength and couple it with your veteran experience and know-how.

Just as getting up, moving around, walking, biking and sensible weightlifting can get people's blood moving, release endorphins and fuel a sense of well-being, there's a boatload of innovative tools and methods that can do the same for supporting, migrating and reviving distributed control systems and their overall applications—and help them overcome the problems of obsolete equipment and persistent downtime, and reach new levels of efficiency, safety and sustainability. Of course, most process applications go years or decades without replacing many controls and other equipment, but there comes a time when maintenance and repairs must give way to technical advances and more capable components and systems.

For instance, Valero Energy Corp.'s refinery in Benicia, Calif., recently completed a major upgrade and rearrangement of its control systems, control room and networking infrastructure with help from Honeywell Process Solutions (HPS). The refinery was built by Exxon Mobil in the late 1960s and originally used an IBM 1800 system for process control, but later replaced these mainframe computers with Honeywell's TDC 2000 and TDC 3000 systems with extended controllers on Data Hiways for base regulatory control and application modules for supervisory control.

Beginning with 44 nodes, the system grew to more than 60 nodes over the next 20 years. The refinery added a local control network (LCN) as its node count grew, but later replaced it with total plant network (TPN) bridges to maintain the performance of this large system. High-performance process managers (HPMs) were added in 2004. And Valero began planning in 2006 to remove its TPN bridges by 2010. The company also wanted to improve its native Windows (NW) interfaces and reduce the possible scope of failure by dividing its system into manageable clusters.

"TPN Bridge support was going away, and, though our big LCN was working OK, a refinery-wide reliability study in 2003 reported that using it was out of step with the industry. The study pointed out that multiple smaller LCNs were more common in the refining industry," says Denise Plaskett, Valero's principal applications engineer for control systems. "So the best solution for us was to remove the TPN Bridge and add Honeywell's Experion PKS on top, allowing distributed system architecture (DSA) communications between clusters to keep our system whole." Plaskett adds that some of the main challenges to renovating with Experion included:

  • Limited space in the refinery's centralized control room;
  • Seven-week shift cycles that made it hard to get operators in to help with design and training plans;
  • A traditionally do-it-yourself Control Systems group that needed external support for this renovation, even as it continued to support day-to-day refinery operations; and
  • Timing issues that required all integration and cutover to the new system be done on-line, while working around unit turnarounds over a multi-year time period. 

Reasoning the Need

Of course, Valero's Benicia plant is just one of many on the quest to renovate its controls, and though each has many unique characteristics, they also share many common challenges and can use many of the same solutions.

Read Also: Blending Process and Discrete Applications

In fact, a new automation survey by system integrator Maverick Technologies LLC in Columbia, Ill., included responses from 175 technical support, asset maintenance and project planning and execution personnel about their DCS applications and efforts (Figure 1).