Coatimundi
HUMS is a fantastic safety tool but not perfect. One problem is that there is so much data, that a "top level" reporting system is needed to interface between all the data and the engineers. This reporting system uses various thresholds and triggers - anything below the trigger / threshold is not presented "in the face" of the engineer, but can be viewed by delving into the raw data.
The thresholds have to be set somehow, and in the early days of HUMS it was mostly guesswork. Various events and experience with false alarms etc have allowed the thresholds to be refined over the years. But since there has not been a previous failure of this shaft, there was no information to allow refinement of the appropriate thresholds. Now there is, so hopefully another small improvement to HUMS will result.
For the time being, the operators now know to keep a close eye on this parameter pending refinement of the thresholds.
HC