Managed SCADA System Advances Water Controls at Steel Mill

Approximately 75,000 gallons of water are required to produce 1 ton of steel. Water transfers heat, removes scale from steel and converts gases produced in ovens and furnaces. Nucor Corporation, the largest steel producer in the U.S., has a production capacity of more than 27 million tons of steel. The Nucor Steel Mill in Crawfordsville, Indiana, needed an innovative, cost-effective solution to monitor its water supply remotely for increased system control and visibility. A lagoon at the Crawfordsville plant provides the water for steel production. Five remote wells supply water to the lagoon using remote control. Plant personnel control well pumps, track well flow across the entire system and identify potential pipeline leaks. Widespread water system monitoring in steel processing extends well pump life and alerts operators of costly malfunctions.

Minimal Updates

For six years, Nucor used a private radio system to control the five well pumps. The Federal Communications Commission’s narrowbanding ruling, which went into effect in 2013, made the radio system obsolete. The ruling reduced communication channel bandwidth from 25 to 12.5 kilohertz. The frequency of the radios was outside the new bandwidth requirement. Steve Long, the facilities electrician for Nucor Crawfordsville, manages the electrical equipment for water treatment, input plant water, offsite wells, potable wells and sewer system. The decrease in radio use left him with significant system complications. Long briefly considered upgrading to a new private radio system that could interface with Nucor’s existing control system. However, the cost to upgrade the radios was almost equal to implementing a managed cellular supervisory control and data acquisition (SCADA) system. Unlike the radio system, the managed SCADA system provided more features and did not require regular equipment upgrades. Long and his team selected the managed SCADA system, which included a technology guarantee. This eliminated system obsolescence and ensured up-to-date radio components. The system remotely controls the well pumps and offers additional features, such as real-time alarms, a Web interface and data reports. The entire managed SCADA system was installed and operating in three days.

Managed SCADA Advantages

Nucor’s SCADA system maintains the amount of steel-processing water in the Crawfordsville lagoon. The analog reading at the lagoon prompts automatic commands to turn well pumps on and off. The high lagoon level threshold is set at 7½ feet; the low level is 6 feet. The system controls the pumps based on these parameters. Water from the remote wells is fed through one pipeline to the lagoon. The managed SCADA system ensures the pipeline is never overburdened by too many pumps running concurrently. “We only want two pumps running at the same time—three at the most—because of pressure restrictions on the waterline,” Long said. “We were able to set up the SCADA system so that no more than three pumps run together. I’m also able to access the Web portal at any time to see if the pumps are running or not. ” The system dispatches alarms to Long and operators when a loss of station power occurs. “During power outages, it can take the power company several hours to restore power,” Long said. “Without power, the pumps don’t run. Prior to using the managed SCADA system, we had no indicators to let us know when the power was out, which was frustrating. It would take two to three hours before anyone could see that the lagoon level had dropped.” “This was a problem because it would take just as long to get the level back up. Water is a necessity for processing steel—there would be big problems without it.” If power goes out or a well pump fails, Long can now remotely activate a well pump at another station by accessing the secure Web portal from a desktop computer or smartphone. This keeps water flowing to the lagoon and prevents it from getting too low. Long primarily accesses the Web portal through an industrial touchscreen PC that was installed along with the managed SCADA system. The touchscreen is mounted outside the control panel. The managed SCADA Web interface is remains running on the PC so operators can view live data at all times. Operators use the Web portal to check pump status and track system activity. Graphs and reports verify that the lagoon level is within parameters. If it falls outside the set parameters, real-time low- and high-level alarms are sent to the operators.

System Transparency

Each Nucor well pump has a flow meter monitored by the SCADA system. Low flow alarms help personnel address problems before they escalate. Early warnings allow them to visit the well site, identify the problem and fix it in a timely manner. Trending flow data can be obtained through the Web portal. Each station generates a flow report from the flow rate and flow pulse data. Flow data, which operators use to track water loss and detect pipe leaks, can be downloaded to a spreadsheet for comparative studies or viewed in graphical or tabular format. System transparency has been a major benefit to the bottom line. “We have a lot more visibility with the wells than we did with the previous system,” Long said. “It’s nice to be able to see what’s going on. Sometimes, there is not enough of me to go around. This is why the managed SCADA system has helped me so much. It’s user-friendly and dependable, and it has made my life easier.”