Time wave form analysis

[zipped]

Friends, i am naive to vibration analysis. Can you help in understanding time wave form. What all parameters do we check in this particular type and for what purposes?

 

[IRstuff]

Generally, the time behavior for steady state vibration is less interesting than the spectral behavior.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[zipped]

Thanks but i would like to learn time wave form analysis.

 

[DLite30]

First google result.

http://www.unitechinc.com/pdf/IntroductiontoTimeWaveformAnalysis.pdf

 

[zipped]

Thanks DliteE30.
Actually i have already downloaded the same file. But the thing is they have given a very general examples of waveform having patterns. In actual we rarely see these patterns.
I have a problem with interpreting waveform not having any pattern.

 

[DLite30]

I think that time-wave data is helpful in trying to visualize the motion of the equipment, especially if the amplitude is in terms of displacement.

If you have an unknown wave form where you can't easiy pickout individual motions or waves, that's where the spectral data helps. Look at the specta, that shows you the frequency peaks, and from there you can go back and try to pick out the wave forms.

Some hardware/software systems let you go back and filter out certain frequencies and review the wave data with some of the "nosie" removed from the wave form.

As with any vibration analysis, you need first to understand the nature of the equipment, and what it's normal vibration signature is, and how abnormalties show themselves (like misalignment or oil whirl) and that way any deviation in the waveform data or spectal data can be detected...and data trending is the way to do that, which wave form comparison is not really practical...it's best to compare historical spectral data.

 

[IRstuff]

Typicall, waveform analysis is done by doing the Fourier transform, particularly if there are multiple frequencies involved. Unless there's something obvious, as in the example, time series analysis is generally very unproductive.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[zipped]

thanx for your valuable responses.

 

[zipped]

My next doubt is related to some terminologies related to vibration.
1. what is overall vibration value?
2. what is peakvue?
3. what is coast down?
4. what is waterfall?

 

[tomirvine]

Here is a paper on signal analysis:

http://www.vibrationdata.com/Shock_and_Vibration_Signal_Analysis.pdf

Tom Irvine

 

[electricpete]

1. what is overall vibration value?
In rotating equipment vibration, usually it is meant as roughly the same as an rms value. There is quite a bit of variability in meaning of this term. Digital vs analog overall. Sometimes in US rotating equipment vibration, the rms value is multipled by sqrt(2) and called pk/0 (different than true pk/0). Recently I heard someone claim on maintenanceforums.com that overall should only be used to refer to "instantaneous" value.

2. what is peakvue?
proprietary enveloped or demodulated type parameter used by CSI, primarily for early detection of rolling bearing defects

3. what is coast down?
A coastdown test is done by gathering data during the time when a motor is powered off and the machine coasts to rest. Analysis of phase and magnitude changes during this period can tell a lot about critical speeds.

4. what is waterfall?
A series of spectra taken at different times. If you will, the x axis is frequency, y axis is magnitude, and z axis is time.

=====================================
(2B)+(2B)' ?