When the vibration
characteristics of components such as planetary gears change,
the components require careful visual inspection. With a little
experience, and a practiced eye, tooth contact pattern changes,
wear and damage are easy to identify. However, not all parts
of the toothing or roller bearings are always visible. In
one instance, the operator of a cable car was only able to
feel local tooth damage in a gear with his hands. In other
sectors, oil analyses and filter checks need to be used in
an attempt to determine the degree of wear.
The true state of the gears can only be assessed by dismantling
the components – a lengthy and costly procedure. At
times, components can be partially dismantled, but even here
there are limits. Figure 1 shows a partially dismantled gear
in which only a section of the sun gear is visible. It is
for this reason that in the shipping industry, certain drives
that require monitoring are completely dismantled every five
years.
An alternative to dismantling components is video endoscopic
inspection. Experienced service technicians know where the
component must be checked for damage. The image on the cover
of this brochure shows videoscopic inspection of a planetary
gear in a wind turbine. The head of the videoscope is inserted
through bore holes and then positioned properly. Using a joy
stick, the head can be turned through 300 degrees using a
servo motor (Fig. 2). The live images appear on the monitor.
Informative photos can be saved and processed further if necessary.
Practical experience in the field has shown that in planetary
gears and slow-running drive components, videoscopic inspection
should be used in combination with vibration analysis. When
frequency selective vibrations change, the machine component
determined to be the cause of the problem can be carefully
videoscoped in the affected area, making aberrations and damage
faster and easier to find.
The PRÜFTECHNIK Diagnostic Center has already successfully
integrated videoscopy into its extensive service offer. For
example, using this method, it was possible to avoid dismantling
the gear of a wind turbine (Fig. 3 & 4), instead performing
diagnoses more frequently. |
