Century Aluminum is a global metals and mining company with primary aluminum production operations in the U.S. and Iceland. The company’s smelting facility in Mt. Holly, South Carolina, houses casting equipment capable of processing nearly 230,000 tonnes of aluminum, producing standard-grade ingot, extrusion billet, and other products. As the first primary aluminum plant in the world to achieve the ISO 9001 Quality System Standard, Mt. Holly has the highest standards for production efficiency, energy utilization, and environmental control.
Within its casting operations, the company has tunnels for cooling aluminum billets after they’ve been homogenized (Figure 1). The purpose is to reduce the temperature of the billet — typically from 1,000°F to 90°F. The drives on these cooling units control the main fans to bring cool air to the loads and circulate it throughout the aluminum bundles.
“We were faced with an increase in downtime on our two cooling tunnels due to legacy controls that were getting beyond their functional limits,” said Sam Wilson, casthouse technician at Century Aluminum. “The older drives would have required major rebuilding as they were able to track only speed, delivering the data to the PLC. We required more data and faster processing of it.”
In order to address this challenge, Wilson contacted Miguel Ortiz, product manager at Electrical Equipment Company, a local distributor, who represents Siemens, a major technology developer for various industries. Ortiz and his team, Outreach Resources, did an assessment of the situation and devised a solution.
The new drive and communications system involved the retrofit of a competitor’s drive with a Siemens SINAMICS G120 drive (Figure 2), an intelligent operator panel (IOP-2), and a unique Remote I/O (RIO) to EtherNet/IP™ gateway, co-designed by Siemens and SoftPLC. This device is specifically designed to enable easy migration from the legacy drives to the new drives. In addition, the data transmitted now includes current and torque, a significant advantage for the customer.
The results of this improvement, according to the team at Century Aluminum, included a measurable reduction in downtime of over 50%, which enables more reliable cooling of the aluminum materials, proper data analysis due to additional electrical information being transmitted, and programs being saved on the IOP-2 for faster recovery. Due to the plug-n-play feature, no tools are required to wire one drive to another, saving time in the implementation of the new hardware.
Wilson explained that these cooling tunnels run 24 hours a day, seven days a week, and 365 days a year. Therefore, it was critical the changeovers be as smooth as possible. Due to the nature of the design, both control cabinets were completed in eight hours.
Ortiz further details this successful upgrade. “One of the big advantages on this job is that we were able to take a demo unit into Mt. Holly and show Sam and his team how to configure the gateway without disconnecting the legacy PLC-5 controller,” he noted. “We could scale, readjust and map the start/stop activity, plus being able to install and test run the new equipment without changes to the PLC-5 controller program meant the system on the first retrofitted cooling tunnel were ready to roll much faster and at a lower overall cost.”
In full operation now, the new Siemens control system is allowing for a cooling scenario on a 75-ton load in half the time as previously required, which translates to 300,000 more pounds per day processed. As a further energy saving, the motors on the tunnel conveyors now operate more efficiently in a standard vs dynamic mode.
Wilson notes another appealing feature of the new drives. “With the legacy drives, we got only the current data back to the PLC. On the IOP-2, we get to see real-time, current, RPM and the DC output,” he said. “If there’s something wrong, we know it immediately and can initiate corrective action.”
The 150 hp drives also provide improved flexibility with Century’s operations. This is because the drives can be purposed for use in the company’s carbon plant run, also located in Mt. Holly, where 75 hp is the standard motor in use — providing an additional inventory advantage.
Training was also provided to Century following the installation. “In addition to the demo unit we used, about ten days prior to the install, we did an event at the customer’s facility where we gathered the technicians and some of the engineers to give them an overview of the drives, the IOP-2 and how to troubleshoot from the TIA Portal software,” said Ortiz. “The training gave them both practical knowledge and a higher comfort level, as the majority of those present had lots of experience with another brand of drive products. We were able to show them how to seamlessly connect the new and the remnant legacy products.”
He also complimented the Century team for going the extra mile to take the maintenance and management classes Siemens offers. Using the IOP-2 and its memory for programs, Wilson and his team can use the Siemens Totally Integrated Automation (TIA) Portal to further minimize downtime, as the tunnel performance can be set to ramp-up per the known batch of product incoming.
Overall, the conversion on this application took less than 60 days. “The plug-and-play technology plus the substantial program storage on the IOP-2 make our training of younger techs and operations personnel much easier. With the older equipment, line code upgrades were very time-consuming, while they’re automatic on the Siemens equipment,” notes Wilson. “The younger employees have that fast and easy modular mindset, which is great, as it matches the plug-and-play technology. Saves us a lot of time and money. I thankfully was on an old boat in the Navy and some old Los Angeles class submarines, so I know a bit more about the history of the legacy gear.”