Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery

7Managing Critical Machinery Vibration Data

By Robert X. Perez

Beware of False Positives and False Negatives

Field vibration analysis errors and sensor issues can result in erroneous conclusions, which in turn can lead to unnecessary repairs or missed mechanical faults. Analysis accuracy is of paramount importance when monitoring critical machines in order to control maintenance costs and reduce risks to acceptable levels. In addition, a disciplined sensor selection, installation, and testing program are required to ensure the fidelity of critical sensors throughout their lifetime.

Figure 7.1 Regularly monitoring machinery condition is a vital part of any machinery reliability program.

Organization can reduce potential vibration analysis mistakes and errors by adopting various data collection and maintenance strategies aimed at improving the validity and reliability of the vibration data (Figure 7.1). Before we discuss some recommended data collection strategies, let’s explore the four possible outcomes from a machinery vibration analysis:

• True Positive (TP) The problem detected is real: This is the expected outcome from a vibration analysis when an actual machine fault is encountered. With the proper training and equipment, the analyst is expected to detect true machinery faults in their early stages in most cases.
• True Negative (TN) There is a correct indication that ...