Page 268 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 4 .5 Gear and Coupling Best Practices

Vibration is the result of a system being acted on by an excitation.
This excitation produces a dynamic force by the relationship:
F DYNAMIC =Ma
Where: M = Mass (Weight/g)
2
g = Acceleration due to gravity (386 IN/SEC )
2
a = Acceleration of mass M (IN/SEC )
Vibration can be:
Lateral
Axial
Torsional

Fig 4.5.8 Vibration

Fig 4.5.9 Excitation forces with examples

should be discussed with the machinery vendor prior to
establishing levels:
Application (critical or general purpose)
Potential loss of revenue
Application characteristics (prone to fouling, liquid,
unbalance, etc.)
Bearing clearance
Speed
Rotor actual response (Bode Plot)
Rotor mode shapes (at critical and operating speeds)

Figure 4.5.11 presents a vibration severity chart with
recommended action, and a schematic of a shaft vibration and
shaft displacement monitor are shown in Figure 4.5.12.
As mentioned above, vibration is measured unfiltered or
presents ‘overall vibration’. Figure 4.5.13 shows a vibration
signal in the unfiltered and filtered conditions. All vibration di-
agnostic work (troubleshooting) relies heavily on filtered vibra-
tion to supply valuable information to determine the root cause
Fig 4.5.10 Non contact displacement measuring system of the vibration.

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