A large iron ore mine in Western Australia managed to avoid a catastrophic vibrating screen failure. The issue was swiftly identified and addressed after being flagged by an alarm on their Waites Wireless system. 

The Waites monitoring system detected a loose bolt at the drive end of one of the screen exciters (Figure 1).

The condition monitoring team investigated and collected data with a handheld data collector to validate the existence of an issue, especially since there were no previous indications of bearing frequencies two days prior. The data analysis confirmed significant impacts occurring at the screen’s operational speed as was identified by the Waites system.  Impacts such as these typically results from a loose component. A subsequent visual inspection validated the vibration analysis, clearly revealing the presence of a loose bolt.

Maintenance initiated a notification within the system to document the critical repair requirement.  A potentially dangerous failure from a rapidly developing failure mode was avoided by having access to online condition data and alarms from the Waites Wireless system.

DETAILED FINDINGS:

The Waites ImpactVue time waveform displayed a series of periodic impacts at the running speed of the exciter (Figure 2).  The time waveform from the handheld data collector echoed these results (Figure 3). The vibration signal pattern closely resembled patterns observed in previous instances of bolt failures. Subsequent visual inspection verified the presence of a minimum of one loose bolt (Figure 4), with a total of three bolts found to be either loose or fractured on this exciter.