BSF – Ball pass frequency – rolling element fault

They are characterized by the presence of harmonic peaks of the rolling element wear frequency (BSF) in the spectrum. In most cases, the harmonic peak marked with the highest amplitude indicates the number of damaged balls or rollers. They are usually accompanied by defects on the outer and inner ring tracks.

E.g. for the SKF 22228 bearing, the frequencies are calculated for 1500 revolutions:

So in the spectrum we would see 1x BSF peak at 89.1Hz and harmonics 2x, 3x, … then sidebands of the cage frequency around them, in our case 10.8Hz, i.e. 1xBSF = 89.1 +10.8Hz -10.8Hz

Examples of damage to rolling elements: