Tips for a Successful Cutover
The guidelines for determining cutover order include going from the back to the front of the unit and from simple to complex loops. If the next step includes an HMI upgrade, try to cut over all points on a graphic before moving to next one. If an issue arises, skip that loop and come back to it later.
PAR uses two hot cutover (HCO) teams – one doing the current cutover, and one planning the next – each with a systems hardware specialist, as well as two contract and one Total instrument technician. A construction coordinator directs outside activities. A DCS systems administrator directs the inside (control room) team, which includes an extra console operator, two contract configuration specialists and two MAC engineers. The teams are scheduled four 10-hour days (Monday through Thursday), and achieve about 35 points per day. Fridays are reserved for rain-outs and to address issues identified earlier in the week.
Lunches are catered to improve efficiency. "The cutover team costs about $15,000 per day," Conley says. "You can spend a lot more than you expect." Hot cutover is when you'll make a major number of discoveries. "You'll find a surprising number of things," he said. "We averaged more than 175 per Hiway on the first two. Decide how you'll handle them ahead of time, because you'll want to fix them all as you find them, and you can't do that at $15,000 per day."
Log all discrepancies (loop sheet errors, range changes, questionable configurations, graphic errors), address high-priority issues immediately using an expedited management of change (MOC) process, and hand off other issues to process support engineering for follow-up. PAR uses discoveries to improve performance on subsequent steps, so previous lessons don't have to be relearned. "By the third one, I think we were down to 12," Conley said. He offered the audience a complete list of "lessons learned" by e-mail request.
The Journey Continues
In 2008, PAR added a Deep Conversion Project (DCP) that would delay the next TDC 2000 replacement step for 30 months. The DCP required nine new Experion C300 controllers in the brownfield to handle 2,850 additional I/O. Additional greenfield units added 12,000 new I/O and two consoles. The project also replaced 45 legacy operating consoles, updated approximately 400 existing operator graphics and installed a refinery-wide fiber-optic backbone.
The central control building was modified to fit additional operator consoles, which gave PAR the opportunity to move the servers to a more secure location. In the process, "We found a lot of abandoned and mystery cable and coax under the floor," Conley said. "We had to be careful that we didn't lose anything."
The fiber-optic backbone runs on air-blown fiber (ABF) installed in a backbone of plastic multi-tubing that has as many as 19 pathways, each able to accommodate as many as 24 fiber-optic cables. Fiber can be quickly and easily blown into or removed from the individual pathways. "Multi-mode, single-mode or mixed fiber can be blown at a rate of 50 meters per minute and in continuous lengths up to 2,000 meters," Conley said. Since the cable is not pulled through the conduit, no strength members or jacketing is needed, and ABF is substantially smaller – a six-fiber ABF cable is 2 mm in diameter, as compared to 12 mm for conventional fiber. "It's guaranteed for 25 years when it's installed by a certified contractor," he added. "We've been using it since 1996."
PAR has now completed five of nine planned steps of its TDC 2000 migration, "on schedule and in budget," Conley said. "With Honeywell's Hiway Care extension, beginning in 2012, we lengthened our program schedule by planning a new step every 18 months. This extended schedule will complete our TDC 2000 conversion in 2023."
Conley left the audience with five takeaway lessons from Port Arthur:
- Read the book, Control System Migrations.
- Choose your MAC and MAC project manager carefully – rely on customer recommendations.
- Develop detailed, comprehensive RFPs for FEL development and detailed design/engineering/commissioning.
- Consider using a configuration/graphics specialty company.
- Maximize your local staff's involvement for long-term success.