12 December, 2018 - Wednesday
Vibration diagnostics offers a way to reliably determine the condition of the machine and detect defects during normal operating conditions without demembering the machine (fan, pump, compressor, centrifuge, gear boxes, turbines etc.). Some of the defects can be:
- unbalance of rotors in electrical motors or driven machines;
- misalignment of couplings;
- misalignment of belts and pulleys;
- looseness between the machinery and the foundation;
- bearing defects (e.g. outer and inner race, rotational element);
- gear box defects (e.g. crackee/broken tooth, gear eccentricity);
- resonance (e.g. the machine's natural frequency matches the machine's working frequency);
- electrical faults in electrical motors (e.g. eccentric rotor, broken armature) etc.
How to determine the type and scale of a problem?
A time component and the frequency spectra of the vibration is recorded at the measuring points of the machine (commonly bearings) during normal operation conditions. By analyzing and evaluating the spectras the condition of the machine is determined along with mechanical defects if there are such. The determination of the defects is on the bases of the dominant frequencies on the frequency spectras and according to the differences on the time spectras.
It is commonly known that every type of defect causes vibrations on a specific frequency. The amplitude of that frequency is proportional to the scale of the mailfunction. According to this, by recording the amplitude-frequency characteristics of the vibrations, we can determine the:
- type (from the frequency of the vibrations),
- scale of defect (from the amplitude of the vibrations).
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