Emerson Exchange 365

North Star BlueScope Steel’s Delta, Ohio, facility turns scrap metal into coiled steel slabs for use in the manufacture of a wide variety of products, from wheel rims and pipes to butane tanks and highway guard rails. “Reliability at every point,” is the company’s motto, and indeed maintaining the reliability of the plant’s equipment has proven essential to keeping its loyal customers satisfied over the years.

At the heart of North Star BlueScope’s operation is its state-of-the-art six-stand direct charge rolling mill, which transforms raw steel slabs into hot-rolled coils. The mill was originally designed for 90 mm-thick slabs, but in 2005 the company stepped up production output significantly by increasing the slab thickness to 100 mm. Soon after the change, the mill began suffering from bearing failures and other mechanical issues, but engineers didn’t have the equipment health data they needed to determine the root causes of the breakdowns.

This week the 2014 Emerson Global Users Exchange, Keith Hoffman of North Star BlueScope, along with Emerson’s Dan Phillips and Barry Coultas of Equipment & Controls, Inc., discussed how they solved the problem with asset management technology—and protected North Star’s reputation for quality in the process.

The first step was to install new wireless torque monitoring systems on the gear spindle shafts that drive the work rolls in the mill stands. This involved fitting the shafts with wireless telemetry transmitters that send torque data to nearby receiver antennas linked to a CSI 6500 Data Processor on the plant’s local area network. “We replaced the first generation telemetry system and its cumbersome brass hoop antenna with new transmitters that have extended life battery packs and better environmental protection,” Hoffman said. “The installation took just two hours from start to finish.”

The project team chose a data sampling rate of 500 Hz, which is high enough to record the actual torque at the point when the slabs impact the rolls without truncating peak values on the readout. This proved to be crucial. When operators rolled the first slab after a scheduled outage, the transmitter recorded a torque level that was five times higher than the mill’s design specifications. There was no apparent damage to the drivetrain components, but to be safe, the team removed the spindle in question and analyzed the torque trend data more closely using Emerson’s PeakVue technology.

“The additional ‘intelligence’ that is now available with the new monitoring system prompted us to physically inspect the spindle, which revealed that cracks had in fact started to form,” Hoffman said. “Removing and repairing the spindle prior to failure helped us avoid costly downtime. The system also enabled us to detect a bad bearing in the pinion stand, saving us $1.2 million that we would have otherwise lost from unscheduled downtime.”

“We have plans to continue installing torque meters and CSI receivers on all our critical rolling stands and down-coilers,” Hoffman concluded. “In addition to the unplanned downtime it should save us, the new asset management system has changed our entire approach to maintenance. Now we’re much more proactive, rather than waiting until we run our equipment to failure before we address a problem. The results speak for themselves.”

Those attending Emerson Exchange can visit the Industrial Automation area of the technology exhibits to see live-streaming torque and vibration data from the roughing stand drivetrain.