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Vibrations in machines are usually
an undesirable and disruptive occurrence that impinges on
machine reliability and service life, and reduces the quality
of products produced or processed on the machines. Yet every
machine and drive also generates vibrations that the user,
manufacturer or operator can take advantage of for purposes
of process monitoring and condition diagnosis.
It’s much like a general checkup with a physician.
Electrodes are affixed to certain points on the body and an
electrocardiogram is made. The cardiologist evaluates the
‘heart vibrations’ over time and makes a diagnosis
of the patient’s current state of health.
Before suitable diagnostic procedures and measurement points
can be selected, the following information on the machine
should be available:
• structural design
• interaction between individual components
• characteristic diagnosis parameters and their threshold
values
• potential faults and mechanisms that may lead to damage
Every rotating machine component, be it a roller bearing,
gear pair or shaft, generates more or less synchronous vibrations
and has a natural vibration frequency, which at the begining
of the component’s service life has a ‘healthy’
amplitude and shape. Incipient damage such as wear, imbalance
and misalignment alters the excitations at this frequency
or creates new excitations. Often, the excitation amplitude
will increase.
Modern vibration analyzers use frequency, order and phase
analyses as well as cepstra to evaluate these changes. Each
of these methods has its limitations and must be configured
for the application at hand, a task that generally requires
in-depth knowledge of the machine.
Seminars are an excellent way to gain a general idea of
the available procedures and diagnostic methods. The most
effective approach is to have a trainer join you on location.
As you introduce Condition Monitoring to your maintenance
program, PRÜFTECHNIK will provide ongoing support as
well as training of your future specialists.
For example, figure 1 shows the measurement locations on
a conveyor drive. Together with the PRÜFTECHNIK trainer,
you will develop diagnostic strategies on the basis of this
diagram, lay down the corresponding routes and program the
measurement functions into the VIBXPERT FFT data collector
and vibration analyzer. Benchmark measurements are then taken
and jointly evaluated. Potential faults and their consequences
are discussed and the results are documented in an initial
report. A follow-up service takes place 3 to 6 months later.
At that time, the measured results will be evaluated and the
machines are inspected jointly if necessary.
Condition-based maintenance
is becoming a reality.
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