Nuclear Power Cases

Event: Site personnel reported slightly elevated motor vibration and requested diagnosis of the unit.

Diagnostic conclusion: Compared with international standards, the vibration level was marginally acceptable. Energy was present at 25 Hz and its second harmonic, with substantial energy at 1437.5 Hz and sidebands spaced at the rotational frequency. The motor was diagnosed with shaft misalignment.

Site verification: The motor was realigned during scheduled maintenance, after which vibration returned to the normal range.