Hello,
I am new to the forum and also new to Vibration Analysis. Can someone tell me what frequencies I should expect to find in a "Roller Bearing Envelope"- apart from that of Bearings. Also should the 1x be present?


Thanks
Jamie

See Table 1 in:

http://vibrotek.com/article.php?article=articles/new94vi/index.htm


1x may be present. If so, it is usually caused by revolution of the bearing load zone around the oouter race which is usually caused by unbalance.

quote:

1x may be present [in the demod spectrum]. If so, it is usually caused by revolution of the bearing load zone around the oouter race which is usually caused by unbalance.

I have often seen in the regular spectrum the 1x sidebands around harmonics of fault frequency that you describe. For example around BPFO we associate by theory with a rotating load as you say. 1x sidebands around BFPI comes from steady direction load and rotating inner race... load at location of defect is still varying once per revolution.

BUT, if we envelope this, we get lower order fault frequency harmonics with 1x sidebands. I don't see how or why it would show up as 1x. I believe you are mistaken on that point (which doesn't happen often). Please let me know if you disagree.

1x and 1x harmonics in the demod spectrum I would assume comes from something in the time waveform repeating at 1x - perhaps loosenss causing impacting at 1x.

It's generally poor practice to demodulate parts of the spectrum that contain harmonics of fault frequencies as the simple demodulators in most data collectors can't distinguish between the broadband signals that bearings under load emit and the narrow band signals that are found in low frequency data.

Inner race flaws are normally associated with demodulated signals produced at the characteristic inner race modulating frequencies modulated at shaft rotating frequencies because the position of the inner race flaws varies at shaft rotating frequency.