Gerdau Ameristeel Corp., based in Tampa, Fla., is the second largest mini-mill steel producer and steel recycler in North America, with an annual manufacturing capacity of more than 10 million metric tons of mill finished steel products. The company currently has 11 mini mills running a manufacturing execution system (MES) called QMOS (for Quad Mill Operation System), from Quad Infotech Inc., Toronto, Ontario, Canada, which interfaces to the company’s Oracle enterprise resource planning (ERP) system.
While QMOS oversees the management of information to the ERP system, it relies heavily on KepServerEX from Kepware Technologies Inc., of Portland, Maine, to manage the myriad of diverse programmable logic controllers (PLCs) distributed throughout the mills. KepServerEx relies on OPC, an open communication standard, to enable communication among products from a variety of vendors.
“We have a variety of different PLCs—just about every platform out there—Siemens, Allen-Bradley, GE and so on. We’re trying to become more standardized, but each mini mill has its own set of PLCs. The great advantage of using KepServerEX is that its drivers are able to connect to all the PLCs, regardless of their individual specifications,” says Jason McGill, application architect at Gerdau Ameristeel.
Melt and roll
In the company’s Jacksonville, Fla., mill, there are two major operations—the rolling mill and the melt shop. There is also a shredder, which takes large objects—such as cars and other large pieces of metal—and shreds them down so they will melt faster. The plant melts and rolls about 90 tons of steel an hour, or the equivalent of 750,000 cars per year.
The Jacksonville rolling mill operation is monitoring approximately 13,000 input/output (I/O) points, and the melt shop has another 10,000 points for a total of 23,000 I/Os being acquired from the PLCs via KepServerEX. “We’re only about half of where we want to be,” says Jarrod Parrotta, improvement facilitator at the mill. “Our target is somewhere between 40,000 to 50,000 I/O points.”
There are currently four Wonderware Servers in the Jacksonville plant—two in the rolling mill and two in the melt shop. The servers, supplied by Invensys Operations Management, Plano, Texas, are set up in a redundant configuration and run a thin client. The plant uses Factory Focus, the read-only version of Wonderware InTouch.
The thin clients are installed on the corporate side on the desktops of certain executives who have a need for a more granular view of specific operational information. Process data is collected by KepServerEX via LinkMaster, another Kepware product. LinkMaster allows Gerdau staff to easily link data from multiple data sources and provides a simple means of integrating systems from multiple vendors into a single operational solution. In this case, the KepServerEX communicates the data to QMOS and to Factory Focus.
“With the current system configuration, I will never have to let anything through the firewall. Using the two Kepware servers across the firewall allows me to provide a security control feature and limit the amount of traffic on the process network,” Parrotta notes.
Gerdau Ameristeel uses some 19 PLCs from about five different PLC vendors, primarily GE and Rockwell Automation. According to Parrotta, problems were arising because of scalability issues. The company wanted to add additional Wonderware terminals and was finding that the PLC scan rates were being taxed and becoming too slow. “As we added more terminals, some of our processes were nearing the limits of their scan cycles. This was causing us to have data issues,” says Parrotta. “Our Wonderware clients that were pulling data from the PLCs were running so slow that they weren’t reporting what they needed to report and would just stop communicating to the other clients—skipping a scan cycle entirely.”
Using KepServerEX, the company was able to solve the problem by centralizing all the communications to one server. “Rather than having five or six clients pulling data from it, which was mostly repetitious, we had one Kepware server and clients pulled from that server,” Parrotta explains.
To provide additional intelligence on the milling and rolling operations, the Jacksonville plant integrated a historian as a separate standalone system. “We were gathering data anyway, so we decided to create a historical archive. Our historian software pulls the clients directly to Kepware. When QMOS was introduced, we already had everything in place so it was just an easy plug-and-play.”
Troubleshoot anything
Currently, the Jacksonville operations are logging all of their tags. If operators have an issue, they can literally track down the problem to the minutest detail. According to Parrotta, because all the physical I/Os are being logged, company users can technically re-create anything that an operator did via the Wonderware interface. “We can trend just about anything and find out if it was a human error or whether it was, for example, a sensor that failed. As long as we have every I/O logged, we can troubleshoot anything,” he says.
After receiving a schedule from the ERP system, QMOS covers the management of the planning, scheduling and production in the rolling mill and the melt shop. It manages the process from receiving customer orders, creation of production schedules and managing the demand for the steel, up to the production of the billets and bundling and packaging and shipment of semi-finished or finished products to customers.
“QMOS figures out what ingredients are needed for the products. Recipes for those orders reside in both QMOS and Wonderware. QMOS is keeping track of each step in the process. It’s keeping track of all the operational parameters that are critical—for example, amps, pressures, kilowatt-hours, time start/stop (off events from PLCs via Kepware). As these events happen, we move the products we are making through one station to the next—triggering and tracking PLC events. These are all recorded in Kepware. As the events happen, they move from stage A, to B, to C…as part of the batch. All this is tracked inside the QMOS MES system.
“QMOS is passing data and tags back to Kepware and I’m using that data to trigger Wonderware to auto-load the recipe that is needed. We are moving toward an automatic recipe load. It’s still handled by Wonderware, but is getting signals to do so from QMOS through Kepware. We’re pulling data out of the Oracle database on the opposite end within certain parameters and we’re sending those to the KepServerEX to manage the tags to the PLC.”
Challenges met
In the Jacksonville plant, Kepware provides the connectivity between the PLCs, QMOS, Wonderware and an IBM historian. Operations are separated into two domains, the plant floor/process side and the corporate side. The Oracle ERP resides on the corporate domain, and Wonderware, the PLCs and historian reside on the process domain. QMOS and Kepware straddle between the process side and corporate because QMOS via Kepware’s communication delivers data that both corporate and the process people use. There are two redundancy KepServers on the process side and another two KepServers on the corporate side. The plant is running the KepServers as simulation modules that act as clients without having any extra drivers or licenses installed.
Two main challenges at the Jacksonville plant, according to Parrotta, were to solve the problems of overtaxing the PLCs, and managing the traffic on the network from both the corporate and process domains. “With KepServerEx’s ability to read a variety of PLCs, it helped us overcome those two challenges,” he says.
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