Control system migration may be complex, but identifying, addressing and resolving its many problems can make it an especially rewarding challenge for the automation professional. A team at Total Petrochemicals & Refining has been modernizing the TDC 2000 system in its Port Arthur facility since 2005, and learned many lessons they shared this week with other attendees of the Honeywell Users Group (HUG) Americas Symposium in San Antonio, Texas.
The Port Arthur Refinery (PAR) began life in the early 1900s as an oil terminal for Spindletop. It's been a refinery since 1936 and now has a capacity of 174,000 barrels per day (174 MBPD) of transportation fuels. "By 2005, the systems we had installed between 1982 and 1992 were at and over capacity," said Randy Conley, Total supervisor, DCS/SIS/APC implementation, who presented the work on behalf of himself and fellow team members Lanny Gibson and Bert Labath. The 18,000 active I/O are on eight data Hiways – 80% TDC 2000, 20% TDC 3000 – and unit segregation had been lost.
"First, for anyone considering a DCS migration, I highly recommend the book, Control System Migrations, by David Roessler, published last year," said Conley. "I wish I'd been able to read this book before we began our project."
Project Approval Is First Hurdle
Before you can begin, you have to get the project approved, and selling a major migration is not a typical tech presentation. "You'll be talking to high-level management," Conley said. "The stakes are higher and the information needs are different – they want to know, what's in it for me?" Quantify the benefits and speak to persuade, as well as to inform.
Open with a strong, two- or three-page executive summary. "Take out the acronyms and make sure you speak their language," Conley said. "Many decision-makers won't read beyond the summary."
The following seven or 10 slides can explain the assumptions, acknowledge the costs (frame them in a positive manner), provide a simplified schedule and list recommendations. Propose "fit for purpose," not state-of-the-art, emphasize results and give a solid wrap-up as a conclusion. Move supporting details to an appendix or a hidden set of slides.
At Port Arthur, the migration planned eight steps, one per data Hiway, prioritized according to capacity, equipment age and maintenance history. The original schedule was to begin a new step every 12 months to distribute capital commitments and comply with Honeywell's announced end-of-support date. "Each step took 18 to 24 months to complete, resulting in overlap," Conley said. Since refinery outages could not be planned, "We adopted a philosophy of hot cutover at the junction box," he said. Done one loop at a time, hot junction cutover minimizes risk of upset, eases operator transition and decouples the project from operations, but also requires space and electrical power to handle both the old and new systems. Some systems did not have enough room and had to be staged at a remote location. "That added about $1 million," he said.
Choose Your Team Carefully
Conley offered specific advice about choosing a main automation contractor (MAC), manning the project team and managing the hot cutovers. "Use industry contacts to identify potential MACs," he said. His team narrowed a list of 12 to three and awarded them contracts for FEL (front-end loading, or feasibility) studies to estimate costs ±10%, then used the FEL results to prepare the capital request for the first step. They factored those results to get an estimate for the entire refinery ±50%. "After the first two steps were completed, we re-estimated the remaining steps based on our discovery items – our lessons learned," he said.
PAR's project execution team has three full-time roles: project architect, and DCS and SIS project managers. Other team members are temporarily reassigned from their regular jobs as needed. PAR contracts with a MAC and a configuration/graphics specialist to round out the project execution team. This "weak matrix" approach intimately involves plant personnel in designing and implementing the system they will later use, but can slow the project, as members must focus on the plant first, then the project.
"Operations has a key role in the project's success," Conley said. From cable tray routing and enclosure locations to cutover order and risk analysis, "Everything around the hot cutover – they're essential to that." They'll also approve graphics updates, help develop operator training, support factory/site acceptance tests (FAT/SAT), plan and implement the hot cutovers, and maintain the operations punch list. "Assign a chief operator early on," Conley advised. "The CO sells the project to coworkers, which reduces griping."