By Rich Merritt, Contributing Editor
Back in the day (circa 1979), the engineers at Electronic Associates (EA) in Monmouth Beach, N.J., let me cause my own “Three-Mile Island” incident using one of the simulators they built to train nuclear plant operators.
Those 1979-era simulators consisted of a complete replica of a nuclear reactor’s control room, with all the single-loop electronic controllers and panel readouts connected to a minicomputer simulating the reactor. The instructors at EA showed me how to “scram” a reactor. They led me through the entire process, saying, “Shut off the feed-water pump. Close this valve. Ignore that alarm.” I uncovered the core, and scrammed the simulated reactor. Great fun!
At about the same time, the movie The China Syndrome was released, and scared audiences with the near-meltdown at a fictitious nuclear plant. The hero, a control engineer named Jack Godell, keeps telling everyone there’s a problem with a pump, but no one listens. If the Godell character had had modern computer modeling and simulation software, he could have fed all the vibration data into a simulator, the computer would have predicted the outcome, and he wouldn’t have been machine-gunned for his troubles.
Fast-forward 30 years, and the folks at video surveillance vendor Longwatch have built the simulator Godell needed. Longwatch president, Steve Rubin, explains, “We took some clips from The China Syndrome, and put them on an HMI screen to illustrate what such a simulation might look like to an operator.”
In the simulation, the HMI screen first shows normal operation, then an alarm goes off, and the video switches to a “live” camera in the pump room. We watch as the pump shakes itself to death and falls to the floor. [Go to www.controlglobal.com/0810_Simulation.html to see this video and others. The direct link to the video is www.controlglobal.com/0810_SimChina.html.]
The pump animation in The China Syndrome was the result of 1970s movie magic, using mainframe computers with about the same computing power as today’s PlayStation 3. But we’ve come a long way since then, with video gamers leading the way. For example, in the new iRacing racing simulator (www.iRacing.com), the builders laser-scanned in each race track to “replicate the personality, eccentricities and challenges of the track with mathematical precision.” [ To see this realistic simulation in action, go to www.controlglobal.com/0810_SimRacing.html.]
So the question is, can we use the same technology for future process modeling and simulation software? Why would we want to?
Getting Down With Graphics
HMI screens have improved in recent years, mostly in the area of graphics. Today, process control equipment and icons are downright realistic. Marcia Gadbois, vice president of business development for InduSoft, says these HMI graphics lend themselves to modeling and simulation. “When running a simulation, we can make the valves open and close, the pumps start and stop, tanks fill and empty, and show variables changing on the screen.”
But going much beyond this level of graphics in the process control industry is probably unlikely. Companies are not going to laser scan their process areas, so they can be animated on an HMI screen. Though CAD packages can certainly show a 3-D representation of a process unit, what would be the point? There really isn’t anything to see. In a process plant, most action takes place inside things like batch reactors, tanks and distillation columns.
N-D Better Than 3-D
Robin Brooks, managing director of process improvement software vendor Curvaceous Software, advises thinking beyond 3-D graphics to multiple dimensions (N-D). “We see the future as N-D with process operation and alarms and alerts tamed and seen in context,” he predicts. “N-D lets operators see many more variables with alarms and all the interactions between them, and is capable of eliminating alarm floods. How much interaction? Probably less than today, because controls will get better and better, and operators will be forced out of the loop. Start-up and shutdown will be computer-controlled for increased safety. Their role will be limited to deciding what to do in cases of genuine equipment failure only.”
In Curvaceous’ N-D simulation of a multi-phase batch process, which runs at about 100x real time (batch processes are slow in real life), black dots are variable process variables, red indicates an alarm, and blue is corrective advice for open or closed-loop use. Green lines are multi-variable control limits. An operator just has to keep the black dots inside the green lines for a perfect batch. [Go to www.controlglobal.com/0810_SimCurv.html to see this simulation.]
Longwatch’s Rubin agrees with Brooks about operator functions. “Watching an HMI screen has been described as long periods of boredom interrupted by moments of panic,” says Rubin. “If an alarm occurs, operators leap into action. If the plant has video connected to the HMI screens, a camera shot can be instantly put on the HMI screen, so the operator can see what’s happening out in the process unit. It might be a leak, a tank overflowing, or some other visual event.” Rubin thinks video is a better solution than animated graphics for simulations. “All these video snapshots can be archived for future use in a computer model or simulation,” he says. “Then, when the simulation says a tank will overflow, a video snapshot of the tank actually overflowing could be put on the screen.”