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9070 Vibration Analysis Copyright © 2012 Test Products International, Inc.
In order to perform a vibration analysis it is important that the run-
ning speed of the machine is entered correctly. This is done using
the “Setup Wizard” as described in Section
2.3.1 of this user guide.
The frequency ranges of the bands are based on the following multiples
of running speed
2
:
1X (Unbalance):
The level of vibration in the frequency band based on the running speed
is usually indicative of how well balanced the machine is. A large
vibration at the running speed usually indicates that the machine is out
of balance. However even a very well balanced machine will usually
show some vibration at the running speed but this figure should ideally
be quite low (e.g. typically less than about 2 mm/sec or .11 in/sec for a
medium sized machine).
2X (Misalignment):
Vibration in the frequency band centered at twice the running speed is a
possible indication of misalignment. This is based on the fact that shaft
misalignment can result in a double peak in the waveform due to there
being two different centres of gravity (one from each shaft). In other
words the accelerometer picks up a peak as each centre of gravity
passes by and hence there will be two positive and two negative peaks
each revolution of the shaft. This will typically give rise to a vibration
signal at double the running speed of the machine.
3X (Looseness):
Vibration in the frequency band centered at 3 times running speed is a
possible indication that something may be loose (e.g. loose mounting
bolts, weak foundations etc.) as it is not usual to see third order vibration
in a machine unless there is some structural looseness that is being
“excited” by the vibration of the machine.
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2
Multiples of running speed are often referred to as “orders”
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