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4. Diagnostic tools
4.1 RC (constant resolution) or FFT (fast Fourier transform) spectrum and zoom
It's a representation of vibration amplitude in acceleration on a linear frequency axis. With current technology, its resolution is generally 400 lines. The spectrum obtained will therefore be a curve passing through 400 points evenly spaced in frequency.
The frequency band is defined prior to on-site measurements. A distinction is made between :
LF spectra (low frequencies [0-50 Hz]) ;
MF spectra (medium frequencies [0-500 Hz]) ;
HF spectra (high frequencies [0-10,000 Hz]) ;
high-resolution zoom [f 1 ...
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Software
Main analysis software available :
SENTINEL - (Bruël and Kjaer)
SURVAODIAG - (Steel Diagnostic)
Standardization
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- Vibrations mécaniques. Évaluation des vibrations des machines par mesurages sur les parties non tournantes. Partie 1 : Directives générales Partie 2 : Turboalternateurs installés sur fondation radier, excédant 50 MW Partie 3 : Machines industrielles de puissance nominale supérieure à 15 kW et de vitesse nominale entre 120 tr/min et 15 000 tr/min, lorsqu'elles sont...
Appendice
1. Mathematical background
1.1. Vibration: quantification, vocabulary
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Quantification
Like any movement, vibrations recorded during routes can be quantified by three fundamental quantities:
travel ;
the speed of this displacement ;
the acceleration...
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