No one likes receiving those letters saying that your controls platform is so obsolete that its manufacturer will no longer be supporting it. When those letters arrive, it forces companies to ask, “What should we do about it? How do we migrate to a more up-to-date platform without ripping out wires and installing all new equipment?”

The answer is to seek an automation vendor that advocates a migration strategy that matches your needs. In the case of a producer of petrochemicals, the right strategy was one that guaranteed continuity of operations. When management learned that support for its legacy Fisher Provox system would end in 2012, it decided to migrate to a new system at the very next planned shutdown in 2009. Waiting for the following one in 2012 would be too risky.

Of the three proposals it considered, the company selected the one offered by Invensys Operations Management, headquartered in Plano, Texas. “We were able to retain all field wiring, input/output (I/O) cabinets, terminations and power supplies,” says the petrochemical producer’s control system manager. According to Invensys, this ability comes from the openness of its I/A Series distributed control system (DCS), its flexible mesh architecture and an I/O philosophy that permits a one-to-one replacement of other vendors’ I/O modules.

The migration itself took place over four days, and checking the loops took another two weeks, all of which occurred during the month-long shutdown. The control-system manager attributes the success to seven months of planning beforehand and involving the right people from the start.

Migration lessons

Dan Tadie echoes this observation as he tells you about the seven successful migrations that he undertook at Colorado Springs Utilities, in central Colorado. A retired plant manager working part-time as a migration consultant under the name Sunhills Consulting, Tadie put these qualities at the center of the four-step migration plan that he developed during his 29-year tenure at the utility.

The first six migrations converted pneumatic controls on six units in two plants to DCSs, but the last one at the Birdsall plant differed from the others in two important ways. First, this migration would retain most of the existing field devices. Second, it would replace the DCS with a platform based upon ControlLogix process automation controllers (PACs) from Milwaukee-based Rockwell Automation Inc.

Birdsall’s three fossil-fuel-fired units had been sitting idle most of the time because long-term contracts allowed the utility to buy electricity cheaper than the plant could produce it. Whenever short-term economics favored using Birdsall, though, another plant would dispatch a crew to fire up the old Birdsall units for a while.

Birdsall’s future came into question when the DCS manufacturer sent the utility the dreaded letter of obsolescence. An assessment, however, showed that a number of changes, including new controls, would allow the plant to continue contributing to the utility’s bottom line. “If Birdsall could be counted on to be reliable, it would offset power purchases of about $6 million a year,” explains Tadie.

To avoid bringing yet another controls platform into the company, Tadie limited his search to the platforms already used there. Of the four that made sense at Birdsall, he chose ControlLogix. “Rockwell had an advantage with scalability,” he recalls. “I could operate our smallest hydroelectric site cost effectively and easily scale it up for our largest fossil-fired unit.”

Four-step plan

The first step in Tadie’s four-step migration plan was to identify the capabilities of his staff and to use them as much as possible. “We assessed what we could become capable of doing within the allotted time and budget, rather than what we were capable of doing right then,” he explains. “Everywhere we could, we used our in-house staff.”

Because his staff consisted mainly of operators, he taught them the basics of instrumentation so they could execute the second step in his plan—identifying and verifying each control component in the plant, from field I/O to controls. At Birdsall, Tadie gave his staff a list of all known field devices and asked them to verify their calibration and to find any discrepancies. “They came up with two or three, which was great, because those would have been the ones that burned us at start-up,” he says.

After you figure out where you are, the next step is to determine where you want to go, taking into account your budget and other constraints. Tadie recommends consulting an integrator for guidance if you do not have the resident expertise. He also urges having several conversations with the operators and ...