At ArcelorMittal, we recognize that the steelmaking process requires significant energy. As a result, we are constantly finding ways to save energy. We strive to be a responsible energy user that helps create a lower carbon future. The installation of variable frequency drives (VFDs) is one example of our efforts to do so.
At the Burns Harbor hot strip mill, four 400 horsepower motors power pumps supply water to the runout table to cool a steel strip after it passes through the finishing mill. According to Tom Poplawski, process manager, “These pumps ran all the time, whether the mill was down or on a slower pace – even when we were running product that did not require all the 60,000 gallons per minute.”
To reconcile this unnecessary expenditure of energy, Tom and three of his colleagues decided to install VFD technology. A VFD is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the motor. With the VFDs varying the speed of the four motors, the pumps provide just the amount of water required for cooling the steel and no more. “Today, they are running between 60 to 80 percent of the speed that was previously used and we’re only delivering the water required by the operation,” explains Larry Fabina, manager, continuous improvement.
The replacement process took careful planning and the team had a tight window to get the VFDs installed.
“We didn’t have time to remove the old starters, so we had to find an area to install the new drives, while we were still running on the old drives,” says Melecio Magallon, project manager. “Once we identified that, the next hurdles were power cables. We weren’t very comfortable with the existing power cables, because of their age, and they weren’t really designed for a VFD. So, we figured out a way to get the new power feeds from the new drives down to the existing motors. Then, we brought in a contractor to work with our in-house electricians and do the physical install, as well as all the wiring, the start-up and commissioning.”
The first advantage of the new process is energy efficiency, but that is not all. Burns Harbor is also saving money on maintenance, because there isn’t as much wear and tear on the pumping system.
Plus, the system may ultimately help improve the quality of the product, due to more consistent temperature control.
“One of the things we looked at was how the pressure is affected by turning on the bottom spray,” explains Chris Thompson, engineer. “Sometimes this causes a pretty big pressure drop, which affects our coiling temperature. We were never able to do anything about it before because the speeds always had to be at 100 percent for all the pumps. Now we’re able to increase the speed right when we’re turning on the bottom spray. We don’t get the pressure dip and it improves our coiling temperature control in the head end of the strip. So it made a difference in quality to make it better and we didn’t even think about that to begin with.”
This project was a success on many levels, according to Fabina. ”Number one, it was done safely - no injuries happened throughout the project. Number two, it came in under cost. Three, the project has attained the energy savings that was in the new original project scope. And four, we maxed out on the incentive check from the utility company (NIPSCO), which was $440,000. This project has a little over a one year pay back and from here on out it will be saving approximately $360,000 a year, year after year.”
ArcelorMittal acquired the VFDs from Eaton, a power-management company that works with companies to improve their energy efficiency and worked on the installation with Glenmount Global solutions, an independent engineering and technology company.
VFDs have been installed at a number of other facilities and will continue to be adopted due to their many benefits. Saving energy and money, they are an effective solution that contributes to our goal of being a responsible energy user.