Wireless: Steel mill applications show communication reliability

By Control Engineering Staff November 7, 2007

In two application success stories, two companies, Honeywell and Emerson , prove that their wireless platforms can survive and operate in steel mills, which have to be one of the most hostile industrial environments. Examining these applications makes the point that those radios can handle tough assignments and save money in the process.

Honeywell’s example is at Nucor Steel in Tuscaloosa, Alabama. The main application is the electric arc furnace, the main vessel in which scrap steel is melted for recasting into slabs. The furnace uses large carbon rods to form huge arcs inside the furnace, combined with gas burners around the perimeter to melt 135 tons of scrap in each charge. Probes are placed at strategic points around the outside to monitor the process temperature and alert operators if heat has compromised the refractory lining and is threatening to burn through the furnace sides.

Describing the process, a melt shop electrical supervisor said that the instruments themselves aren’t the problem as much as trying to protect the cables to the devices. As he put it, “We have so much heat and flame that we destroy the long runs of wiring. If I could get rid of every piece of wire on this furnace, I would be a happy man as an electrical supervisor. We don’t usually destroy the sensors, and we don’t destroy the cabinets, because we can control those points. It’s the long continuous cable runs in between that are nearly impossible. That’s why this has had such an immediate impact for us. If we have great success, I’m sure we’ll expand it to the rest of the mill because they face the same challenges.”

The area surrounding an arc furnace is extremely hot and indescribably filthy. Moreover, electrical fields generated by arcs operating at 120,000 amps do not make for a peaceful RF environment. Still, the sensors survive in that context and the communication has been exceptionally reliable.

Emerson’s deployments at Wheeling-Pittsburgh Steel have centered around the 80 inch hot strip mill at the Mingo Junction plant. Here, huge slabs of glowing steel are squeezed into thinner, longer strips and rolled into coils. At various points between the roll stands, water is sprayed on the steel either to strip off oxide scale or to cool it before coiling. One of the first applications was installing flowmeters on the cooling headers. There are huge amounts of electrical drive equipment with large variable speed drives on the mill stands, and smaller variable speed drives on each of dozens of transport roller drives. Again, it is hardly a clean or peaceful environment. When high-pressure water sprays hit glowing slabs, water and steam goes every direction.

The information collected by the wireless sensors has proven to be very valuable to the plant operators. Gary Borham, operations manager, noted that, “We previously had no way of knowing how much water was being sprayed over the surface of any given piece of steel traveling down the run-out table. Now, the actual water flow is known, making it possible to always attain the optimum coiling temperature.”

In one “aha moment” during the installation process, after technicians had put in one transmitter, they were confused when two appeared on the control system. It turned out that the second was sitting on the floor of the maintenance shop, two buildings away, communicating through the steel and concrete walls. It had already announced itself to the self-forming network.

These success stories in very difficult environments give a sense of what wireless instrumentation is capable of doing. The signal robustness should be an encouragement to anyone who wonders if it can really operate in a harsh industrial application.

—Peter Welander, process industries editor, PWelander@cfemedia.com Control Engineering Weekly News

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