Page 128 - Intro Predictive Maintenance
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Vibration Monitoring and Analysis 119
Figure 7–3 Example of a typical time-domain vibration profile for a piece of
machinery.
Figure 7–4 Discrete (harmonic) and total
(nonharmonic) time-domain vibration curves.
this is not practical because of variations in day-to-day plant operations and changes
in running speed. This significantly affects the profile and makes it impossible to
compare historical data.
Frequency-Domain
From a practical standpoint, simple harmonic vibration functions are related to the cir-
cular frequencies of the rotating or moving components. Therefore, these frequencies
are some multiple of the basic running speed of the machine-train, which is expressed
