It’s not easy to stay dry under a waterfall, but that’s just one of the environmental conditions Emerson’s Rosemount 248 and 648 temperature transmitters must handle when they’re monitoring bearing pressure and lubrication for rollers conveying hot steel at the Ternium Steel facility in Monterrey, Mexico.
The company is unusual because it digs iron ore from its own mines, manufactures steel and value-added products, and even markets and distributes them. However, it still has to deal with the traditional chores of hot rolling, such as routine bearing assays and regular roller replacements.
“Lube oil for bearings and cooling water are the blood of a hot-rolling system,” said Oliver Rodriguez, key account manager at Emerson, who presented “Revolutionizing steel mill efficiency: Ternium’s wireless solution saves $650K monthly” at Emerson Exchange 2025 in San Antonio, Texas. “Bearing over-temperature due to poor or unmonitored lubrication increases product scrap and rework, reduces revenue, and increases process shutdowns that can take a full day to fix.”
Lacking online monitoring, Rodriguez added that Ternium’s staff often used a thermal gun during manual rounds. However, so much water is used to cool the new metal sheets that it was difficult to get accurate temperature measurements, or even check the lubrication oil’s outflow temperature with an RTD. Other problems included preventive and sometimes unneeded roller replacements that were both costly and time-consuming.
“This is why we wanted to test WirelessHART’s self-organizing, self-healing network,” said Rodriguez. “It can use multiple pathways to reach its gateway, and provide robust, reliable communications despite Ternium’s harsh plant conditions.”
Picking appropriate wireless parts
To determine the right components for Ternium’s new wireless network, Rodriguez reported it needed devices with accuracy of ±0.225 °C, two-year stability and Callendar-Van-Dusen sensor matching for improved accuracy. Beyond WirelessHART and a self-repairing network, the steel plant also required external antennas with standard and extended ranges, field-replaceable Emerson SmartPower modules with up to 10 years of maintenance-free operation, and simple, wire-free installation.
“To monitor lube oil temperature on bearings on each side of the rolls, we deployed Emerson’s Rosemount 248 and 648 temperature transmitters that were housed in tight enclosures to prevent water intrusion. We also added Rosemount 214C Temperature Sensors and Rosemount 1410 wireless gateways,” said Rodriguez. “WirelessHART allows easy replacement because maintenance technicians can remove their whole assembly without worrying about wires. This reduces replacement time to just mechanical installation.”
Once temperature measurements and other data reach the gateways, they are transferred to Ternium’s distributed control system, where a bearing temperature topping 85 °C will trigger a bearing replacement alarm to keep it from melting or getting stuck. Detecting these events early avoids damage and inevitably longer interruptions to production.
Rodriguez added that Ternium established its WirelessHART network with just 24 I/O points on two dozen bearings but recently expanded it to 48 I/O points. So far, the steel plant has eliminated unnecessary process shutdowns on six production lines, eliminated manual rounds for temperature measurements, improved operator performance, eliminated rework and in total saved about $650,000 per month.
