What Works: Vibration monitoring saves bearings

In Worthington Steel’s Porter, Ind. plant, flat rolled steel is run through a pickling system to remove the oxide scale that forms on the coil surface during steelmaking. The pickle bath is a diluted solution of inorganic acid, usually hydrochloric. The oxide scale must be removed because it is an abrasive that decreases formability and the life of stamping dies in drawing applications, and prevents adhesion of metallic coatings and paint.

“The rollers on the pickling line at Worthington Steel were going through approximately two sets of bearings per year,” says Ken Patterson, a predictive maintenance engineer for electrical contracting firm Koontz-Wagner (www.koontz-wagner.com). At a cost of approximately $75,000 per bearing set plus downtime costs for stopping the production line, the roller bearings called for a robust monitoring solution.

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Drawing on his background in predictive maintenance including vibration analysis, infrared and ultrasound testing, Patterson recommended that Worthington Steel install the ProSmart monitoring system from ITT (www.ittmc.com).

The ProSmart system continuously collects, sorts and analyzes data at the machine without human intervention. Historical trends, FFTs and band alarms provide the tools for a predictive maintenance program, at a cost comparable to a walk-around program and often much less than traditional online condition monitoring systems.

There are many different causes of vibration, so one important requirement is the ability to measure, diagnose and differentiate normal operational vibration from damaging vibration. At Worthington Steel, the pickling machine rollers are jolted as each roll of steel ends. The system was programmed with a delay so it doesn’t alarm this short-term event, but continues to provide alarm notification for sustained vibration problems.

The vibration monitoring system on the pickling line rollers shows equipment status at a glance, allows remote monitoring and diagnosis and alarms via e-mail and telephone if a problem starts to occur.

The system uses wireless technology to transmit machine health data to and over the Internet. When machine vibration, temperature, or any other process parameter exceeds established limits, it provides notification within seconds by e-mail or telephone. As the gateway to the Internet, the ProSmart Communication Module provides a secure connection to the ProNet user interface via LAN, DSL, cell, or 802.11 wireless routers. This wireless architecture reduces installation cost and complexity.

The Worthington system proved its worth one Monday when, on starting up again after a weekend shutdown, “We began to get vibration alarms all over the place,” Patterson recalls. “I got an alarm notification on both voice mail and e-mail that there was a very large radial vibration on the three top rolls. At the time, I didn’t suspect that it was a bearing failure, as no bearing frequencies were present and all three top rolls were reacting in the same manner.”

While Patterson traveled the 90 miles to the plant for further investigation, the pickling process was reduced to half-speed to minimize vibration for the balance of the steel run. Analysis revealed that the hydraulic units, which provide the pressure for the rolls on the steel, were left on through the weekend instead of being raised to the standby position. Leaving the rolls down under pressure caused flat spots on each of the three top rollers. When the rollers resumed production, the flat spots caused damaging vibration on each rotation. The alarm probably saved the bearings on the rollers, Patterson says. “If the process had run at full speed for any length of time without any wireless notification that there was a vibration issue, the bearings would have been torn up.”

Using ProSmart’s advanced diagnostic tools to continuously monitor machine health (locally and/or remotely), and deliver key data directly and wirelessly, allowed Worthington Steel to avoid damage to key rotating equipment. The early warning enabled them to actively manage an equipment problem, thus avoiding the expense of damaged machinery and plant downtime.