Field case · Condition monitoring
Fan drive-end NU314M: BPFI at 389.4 Hz with shaft-speed sidebands, and the inner race at teardown
Quick answer
An automated diagnosis flagged a severe bearing fault at the drive end of a fan. The envelope spectrum showed BPFI at 389.4 Hz with sidebands at shaft speed (quoted as 48.6 Hz). The NU314M was replaced, the inner race was damaged, and the vibration energy in the time waveform fell.
What the case covers
- The application
- What the diagnosis said
- The arithmetic
- Decision
- After the change
- What to take from it
Takeaway. A BPFI line with shaft-speed sidebands, confirmed by a damaged inner race, is the textbook case. Always compare waveforms before and after the repair.
Read the full case, with the data and the numbers