Smart Wireless technology from Emerson Process Management has helped North Star Bluescope Steel improve furnace control at its mini-mill in Delta, Ohio. As a result, the mill has been able to boost production by as much as one batch per day, cut maintenance costs by $200,000 annually, and improve worker safety, say the manufacturers.
Emerson's self-organizing wireless network, based on the IEC 62591 (WirelessHart) standard, collects data used to control the temperature of cooling panels and water-cooled burners on the mill’s electric arc furnace. This data is critical to safe furnace operation. Overheating cooling panels can lead to major furnace damage, with a blown-out panel costing as much as $20,000 to repair. Production time is also lost when the furnace must be shut down during maintenance or repairs.
“Better temperature control through wireless has allowed us to add up to one additional batch per day,” says Rob Kearney, maintenance supervisor for North Star Bluescope Steel. "With each batch worth as much as $200,000, that's a significant advantage."
Emerson’s wireless solution replaced a hard-wired monitoring network with hundreds of wiring junctions. The old network suffered frequent measurement failures in the mill's harsh environment, with its high electromagnetic field, flying slag, vibration, moisture, and temperatures as high as 3,000°F (1,649°C).
“Between nine and 12 measurements per week would fail due to high temperatures or physical damage to sensors, cable or conduit," Kearney says. "And when a measurement point fails, the furnace must be shut down. The new wireless solution eliminated almost 100 percent of the cable and conduit - which reduced maintenance costs by $200,000 annually. The new wireless solution has been up and running for four months without a single failure.”
The wireless network includes 32 of Emerson's Rosemount wireless temperature transmitters; 28 are used for control and four for monitoring. The transmitters send their data to a Smart Wireless Gateway, which interfaces with the mill’s transformer-regulation and burner-control system.
According to Kearney, the furnace’s cooling panels are operating consistently at a safe temperature, and there is less maintenance required around the hot furnace shell, where ambient temperatures can be 140°F (60°C).