Making Migrations Successful
Control system features and functionality are critical, but how big a part does service play? One chemical plant learned that value. See photos.
Many companies offer various grades of dicyclopentadiene (DCPD), a commodity product used in coatings and resins. However, when ultra-high purity levels of DCPD are required, electrical, automotive, and other industries often turn to Cymetech Corporation’s plant in Calvert City, KY.
Since opening in 1996, the plant has been a leader producing ultra-high 97-99% purity grades of DCPD. Marketed under the trade name Ultrene, these grades help Cymetech’s customers lower costs by improving their processes, increasing end yields and decreasing waste.
Until recently, the continuous distillation process was controlled by a Fisher (now part of Emerson Process Management) Provox system. Cymetech site manager Paul Petitt says that the system was installed when the plant was commissioned and had, until recently, been reliable and efficient. However, the aging system began generating nuisance alarms and problems that would cause periodic plant shut downs.
“We had to find spare parts that were pretty prehistoric,” Petitt says. “There were also issues with the controller which made us seriously look at upgrading our system.” Petitt and other Cymetech engineers soon began evaluating companies to help the plant migrate from the outdated system to one that would reliably automate the process for years to come. Since Cymetech is not a large company, the evaluation process was straightforward and the team quickly narrowed the choice to three suppliers.
Petitt adds, “We were familiar with the Provox language and we didn’t want something radically different, but cost, service, training, and local support were factors as well. We compared everything on a spread sheet and Siemens’ migration plan stood out.”
Weighing service and training
This was the first project where Petitt and Cymetech had considered Siemens and there were some concerns about specifying a new vendor. Cymetech production engineer Jason Tucker and Petitt went to Siemens’ nearby St. Louis, MO, office to evaluate the PCS 7 process automation system, including the PVX OS operator system, for the upgrade.
“Siemens engineers and technicians assured us that we would receive technical support and service that would exceed our expectations,” Tucker says. “The attitude was, ‘we’ll work with you to make it work and you don’t have to figure this out on your own.’ We discovered that anytime we called the U.S.-based hotline, someone got back to us within minutes. The local technicians were also always willing to help out.”
After the agreement was finalized, Tucker visited Siemens training facility in Norcross, GA, for one week of instruction. This was his first hands-on exposure to the system. “Once I started to learn the language and began playing around on the operator station, I was really able to take off with the project,” Tucker says. “I was able to generate a lot of graphics and function blocks, and I really began to see how things worked by following the manuals and examples from my training in Atlanta.”
Tucker also found that Siemens’ online technical forums were helpful. The forums include technical support representatives, as well as thousands of other PCS 7 end users from around the world, who help address issues relative to the situation at hand. And since Tucker alone would oversee and execute the programming and installation of the upgrade, he needed quick answers, support, and thorough product knowledge.
“The project skyrocketed after this training,” Tucker says. “The operator station allowed us to apply and simulate processes to make sure they worked in advance. The operator station had the tools we needed to migrate the database from Provox to PCS 7. It also had the openness of OPC to see values from the Provox controllers. I moved forward because my confidence level was really boosted.”
Starting with a blank screen on the new system and the installed control technology, Tucker started the first upgrade on Area One of the operation where DCPD is distilled to 97% purity. The first upgrade proceeded with the Provox controllers still in place. However, two PVX OS operator stations replaced the existing Provox OWP. During the upgrade, Area Two continued to distill the DCPD to 99% purity using the existing Provox system. These OPC-based operator and engineering stations helped smooth the migration by simultaneously connecting the existing controllers and the new PCS 7-416 controller.
Within two months, Tucker completed all programming. The PCS 7 process automation system and 416 controller was online. “PVX OS had the migration tools and open framework needed to build the OS database quickly, assign Provox points to graphics, and set up the alarm system,” Tucker says. “It also used the OPC open standard to communicate with the Provox controllers in real time and allowed the operators to see points from the old and new controllers. Without this migration step, the upgrade would have been more challenging.”
The migration also included two Micromaster drives and 400 conventionally-wired I/O points. Profibus connected the drives and the IO modules back to the controllers and central control approximately 100 feet away.
After six months, Tucker began upgrading Area Two operations. One year from beginning the plant upgrade, all of the remaining Provox elements had been replaced in both Area One and Two operations. The PCS 7 process automation system now controls and automates the entire plant’s proprietary processes, including temperature controls, pressures, flow, tank levels, columns, reflux flows for distillation columns, and steam flows.
Trending and alarms improve
Petitt says the plant runs more efficiently since the upgrade. Trending capabilities of the new system allow operators in the central control room to review process information over the past 100 days to troubleshoot and consider process improvements. He explains, “Let’s say we had a perfect run two months ago. We can go back and duplicate those settings rather than just trying to figure it out. Or if we have a pressure problem we can determine when it started, and if the pumps heated up because somebody worked on them. We couldn’t do that with the Provox system. It could give an instantaneous trend, but we’d lose the information if we were not there.”
Another upgrade consideration focused on maintaining and adjusting alarms during the transition. Tucker wanted the new alarm screens to closely mirror the previous screens when possible, so he printed every screen, drew arrows where he wanted icons to be placed, and implemented the changes. Since PCS 7 alarm screens can be customized, the process was uncomplicated.
Operators now monitor and adjust alarm indications and settings from the two PVX OS operator stations in the control room using screens that resemble the Provox presentations. Tucker says he created links allowing operators to suppress potential nuisance alarms depending on the type of run selected. “The new DCS system allows the operators to monitor the plant safer and efficiently,” Tucker says. “There are plenty of graphics to show what mode we are in, so there is less chance of turning the wrong alarm off at the wrong time. We know when we do get an alarm we have to pay attention to it. At first, a lot of the operators resisted the change to the new system, but eventually they all said they like the new system better.”
Room for improvements
Petitt says the standard functionality of PCS 7, combined with the information available over the Profibus communications protocol, will simplify future plant improvements and expansions. “PCS 7 can emulate many of the functions of Provox and still stay within the bounds of a non-customized system,” he says. “Also, it will be easier to add equipment, processes and features. Profibus eliminates most of the hard wiring as well as provides the information and diagnostic information we will need.”
Petitt says he is considering using the PCS 7 system and Profibus for potential asset management and energy management programs. Profibus brings diagnostics from the drives and other equipment back to the workstations allowing operators to examine all of the variables giving them a status indication of the asset and energy expended. Tucker adds, “The upgrade gives us additional and easier ways to change parameters to improve the process. We get a spreadsheet that serves as a starting point for an improvement suggestion. We type in the parameters, implement the change, and see if it works. Now, it takes less than 10 minutes to change a control point. In the past, we would have to temporarily shut the process down and wait for an hour to make the smallest changes.”
Both Tucker and Petitt say the performance of PCS 7 has met their expectations for ease of use, reliability and functionality. They also point to Siemens upfront and ongoing service and support as keys to the success of the upgrade. “We were promised one week of support to do whatever we needed, from pulling wires to engineering,” Tucker says.
|Rich Chmielewski is chemical marketing manager for Siemens Industry Inc.|