Does this sound familiar? “We have a lot of old analog and pneumatic crap from the 1960s and ’70s; it’s severely aging, it has poor reliability, and much of it’s obsolete and unsupported,” says Dave Hooten, PE, electrical supervisor for instrumentation, control and design engineering at Progress Energy Carolinas in Raleigh, N.C. “We started trying to replace the worst offenders with digital equipment, but it was done willy-nilly and without an overall game plan, and so we ended up with different single-loop controllers for our moisture separator reheater (MSR) drain levels, different digital feed-water controllers, several digital recorders and other one-point solutions, as well as different loose parts. They all operated differently and didn’t communicate with each other, so we began to see the need to standardize.”
Progress Energy runs five nuclear power plants, as well as coal, gas/oil and hydropower applications that collectively generate 21,000 MW and serve 3.1 million customers in North Carolina, South Carolina and Florida. The utility recently secured a 20-year license renewal for its oldest nuclear plant in Hartsville, S.C., which was built in 1970, and is seeking renewals for two more in Southport, N.C. However, to operate efficiently in future decades, the plants needed standardized digital components and a unified digital network, says Hooten. In 2003, the plants formed a team to evaluate 12 distributed control systems (DCSs), and sought bids on three.
“We stopped and asked ourselves what we were doing here,” says Hooten. “We found that 70% of our non-safety-related instrumentation and controls (I&C) could be on a DCS and a digital network. We wanted to pick one solution for all four sites and have a more strategic alliance with its vendor because our biggest criteria was that, unlike a fossil-fuel application, we couldn’t shut everything down and rip and replace. We would have to do our upgrade in pieces. We also needed good forward and backward compatibility, so we could have scalability and high confidence in our DCS in the long run.”
Hooten says they were nervous, and the project was hard to do. “However, I believed if we could just do one successful upgrade, then it would sell itself,” he adds. “In fact, we just finished our first project a few weeks ago at Harris 1 (Figure 1) in New Hill, N.C., and the guys already are asking, ‘When are we doing the next one?’ Every senior manager we’ve shown this to is giddy.”
Progress Energy’s Harris 1 nuclear plant replaced analog and pneumatic hardwiring in its three-level reactor auxiliary building’s supply and exhaust fan system with a DCS, digital network and Ethernet, as well as HART transmitters.
Source: Progress Energy
Unfortunately, until a better way arrives, the old “if it’s not broke, don’t fix it” mantra still holds. So, even though many devices will likely bust and fail soon, and despite all the hype and node growth surrounding fieldbuses, Ethernet and now wireless, it’s still no surprise to find that a significant majority of all installed control and automation systems still rely on point-to-point hardwiring.
Helge Hornis, Ph.D., intelligent systems manager at Pepperl+Fuchs (P+F) explains, “The engineering staffs at many manufacturers are stretched thin, and so many are doing the same thing they’ve done for the past 10 years. They don’t feel like they have the time to reinvent to make better solutions. But they’ve got to break out of that mode or they’re going to go under. However, it takes management with vision and guts to try new things. As a result, a lot of innovation comes from newer companies that don’t have the baggage of old PLC code and design drawings.” Consequently, it’s during these brief, often unplanned downtimes that many end users find they must finally move from hardwired, point-to-point networks to twisted-pair fieldbuses, Ethernet or other digital networks, often for the first time.
“About 90% of the applications we see still have hardwired field devices because users don’t want to put them on a digital network or Ethernet,” says Dave Blaida, of Matrix Technologies, a CSIA-certified system integrator in Maumee, Ohio. “However, the line between 4-20 mA field networks and data networks are blurring as SCADA and HMI application get more data-intensive. More clients are considering using them, even though they might have had no data network before. We quoted a couple of chemical processing projects recently that included wiring a valve to an I/O point by using actuator-sensor interface (AS-i) bus to replace the hardwiring back to that valve. So, rather than wire each valve back to a PLC, a bank pre-wired with AS-i can send all the valves’ I/O data back through one cable to the PLC. This can save 75% on traditional hardwiring costs.”