equipment, consult the manufacturer's technical
baseline with the current readings to check the
manual.
machinery condition. It can also be used to
The basic instrument for a vibration preventive
troubleshoot equipment for suspected problems
maintenance program is the vibration meter.
and to verify that proper repairs have been made
Figure 3-28 shows a typical vibration meter used
to overhauled equipment.
The principle of vibration analysis is based
on board ships. This is a portable, handheld unit
on the fact that all machines vibrate. These
that is used for periodic machinery checks. It
measures the overall vibration of a machine,
vibrations are caused by the allowable tolerance
errors that are inherent in the machines
which is essentially a summation of all the
vibrations present in the machine at the measure-
manufacture; they form the baseline vibration
signature of the individual machine. Similar
ment point.
The portable, battery-powered meter is
machines have similar vibration signatures
supplied with a carrying case. This case holds the
that differ from each other only by their
instrument instruction manual, vibration pickup,
manufacturing and installation tolerances.
When a machine's vibration signature changes
4-foot pickup cable, 9-inch probe, magnetic
under its standard operating conditions, the
holder, magnetic shield, and meter carrying strap.
indication is that an impending defect is starting
Vibration Analyzers
to change the machine's mechanical condition.
The vibration analyzer provides a vibration
Different defects cause the vibration signature to
change in different ways; thus, the vibration
measurement capability beyond that available in
signature provides a means of determining the
the vibration meter. The vibration meter's
source of the problem as well as warning of the
function is to determine the mechanical condition
problem itself.
of machinery by measuring overall vibration
amplitude. When the meter detects a mechanical
Vibration Meter
defect, however, it is not capable of pinpointing
the specific cause. This is the purpose of the
The information that we provide on vibration
vibration analyzer.
meters is a general description of the meters.
A vibration analyzer (fig. 3-29) contains a
tunable filter and a stroboscopic light. You use
For information concerning operation of this
Figure 3-29.--Model 350 vibration analyzer.
3-21
