IOtech products used in this application:

• ZonicBook/618E Vibration Analysis and Monitoring System • eZ-Analyst Real-Time Vibration and Acoustic Analysis Software

The ZonicBook/618E with eZ-Series software and your PC makes a real-time, portable vibration analysis monitoring system.

eZ-Analyst software working with ZonicBook/618E or 600 Series data acquisition hardware allows continuous monitoring of the vibration and acoustic characteristics of industrial equipment. By tracking these parameters over time, the engineer can detect imminent problems and make sound decisions regarding repair schedules.

IVC Technologies was asked by NUCOR to determine if vibration analysis could aid them in determining which wheels were in jeopardy of failing unexpectedly, and to help them plan future wheel replacements based on their mechanical condition.

This issue was originally approached from a vibration analysis perspective. After thorough evaluation by Allen Bailey, IVC Technologies Regional Manager – Texas Gulf Coast, the issue was escalated to the IVC Advanced Engineering Group (AEG). Directed by Bob Miller, a cohesive program was successfully developed through the collaborative efforts of this highly regarded team at IVC Technologies.

Industrial machines that are “identical” commonly vibrate differently, and cranes are no exception. Statistical analysis showed that though these cranes were the same make and model, built to the same manufacturing specifications, and perform the same jobs while in service, they would typically vibrate differently (both in amplitude and frequency).

Previous data collected with standard condition monitoring equipment was used to determine exactly what type of testing would be required to properly diagnose, predict, and set defect severities for these wheel assembly problems. The data was statistically analyzed, all known fault frequencies were then added to the database, and the wheels that were operating above the statistical alarm levels were analyzed for specific defect characteristics.

Typically, vibration data taken on cranes can show what appear to be transient events in the waveforms. Though transient events are commonly found in these systems, one must be able to mathematically link any vibration signal change to process or mechanical anomalies before assuming that an event is transient. The incorporation of process and crane operation data may need to occur in order to properly catalogue all waveform events.

IOtech’s Solution
Once the initial test data was collected, it became clear that transient vibration data collection would be best suited for this application. This was determined because of the limits on time involved with the data collection process and the many transient events that were occurring in the vibration data as the crane was being operated. IVC Technologies began investigating which type of collection device and software would best fit this scenario, and eventually decided to use the IOtech ZonicBook/618E. The ZonicBook/618E offered eight direct accelerometer inputs (IEPE) along with four dedicated tachometer inputs. In addition to being lightweight and portable, the ZonicBook/618E’s included eZ-Analyst software was easy to operate.

As with any vibration analysis based test, one should always take enough data at a high enough resolution to resolve any defect signature that might be in the system. On most cranes, many critical components have slow shaft speeds with limited run times. Because of this, a person limited to conventional vibration analysis methods (i.e. route-based data collectors) will have a difficult time collecting enough raw vibration data to perform adequate post processing analysis on the back end to offer definitive fault diagnosis. The high-speed ZonicBook/618E let IVC capture high-speed, transient data on multiple inputs which allowed them to accurately predict wheel assembly failures.

Conclusion
Since the implementation of these tests (which have been performed quarterly since 2007), no wheel failures have occurred requiring NUCOR to slow or cease production. Multiple wheels have been changed during this time frame, and an engineering spec change was implemented to further lengthen the life span of these wheel assemblies.

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