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12.0 WHAT ARE YOU MEASURING?
Vibration is the behavior of a machine’s mechanical components as
they react to internal or external forces. Since most rotating machinery
problems show themselves as excessive vibration, we use vibration
signals as an indication of a machine’s mechanical condition. Also, each
mechanical problem or defect generates vibration in its own unique way.
We therefore analyze the “type” of vibration to identify its cause and take
appropriate repair action. With overall vibration monitoring (VIB ISO)
using the EXAMINER 1000, analysis of the cause of excess vibration relates
to the monitoring equipment’s probe position; either horizontal, vertical,
or axial.
Horizontal:
typically, unbalanced shafts tend to cause excess radial
(horizontal and vertical) vibrations, depending on the machine support
design.
Vertical:
excessive vertica
l vib
ration can indicate mechanical looseness as
well as imbalance.
Axial:
excessive axial vibration is a strong indicator of misalignment.
It’s important to note that these are general guidelines and that knowledge
of your machinery and proper hand-held probe techniques are necessary
to accurately analyze the cause of excessive vibration.
12.1 Multi‑Parameter Monitoring
Use different measurement types to monitor your machinery for
changes. This allows for early detection of specific machinery problems
that may not show under normal overall vibration monitoring. For
example, if a rolling element bearing has a defect on its outer race,
each roller will strike the defect as it goes by and cause a small,
repetitive vibration signal. However, this vibration signal is of such low
amplitude that under normal overall vibration monitoring, it is lost in
the machine’s rotational and structural vibration signals. Acceleration
Enveloping can measure these signals better than overall readings. Use
