Stress Wave Identifies Defected Bearing in Gearbox

PCMS Engineering, in partnership with Radicon UK, was asked to perform an independent health assessment check using stress wave analysis on the mixer reduction gearbox at Contitech in Hungary, to determine if the internal components were fit for operational purpose.  Figure 1 shows the general arrangement of the gearbox.

The Challenge

The operational requirements, size and complexity of the gearbox makes maintaining and accessing the internal workings difficult. To assess the condition of the mixer gearbox, the following tests were performed by PCMS Engineering:

  • Vibration Analysis with Gearbox Off Load
  • Vibration Analysis with Gearbox Under Load
  • Stress Wave Analysis with Gearbox Off Load
  • Stress Wave Analysis with Gearbox Under Load
  • Endoscopic Inspection

The Solution

  • Emerson Process Management CSI2140 4 Channel Analyser
  • 100mV/g Accelerometers with Magnet Mounts
  • AMS Machinery Health Analyser Software
  • DART System Endoscope

Measurements were taken at each bearing location in the horizontal, vertical and axial directions. During the test, the gearbox was operated at a recorded speed of 646 RPM Input and 32 RPM Output.

The Results

The stress wave data taken from output shaft 1, Non-Drive End bearing, shows the first indications of stress as a result of a defected bearing. The dominant frequency within this data set is at 387.7Hz.  Overlaying the known bearing calculable frequencies reveals that the 387.7Hz frequency matches the Inner Race defect frequency of the bearing.

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Figure 1

Figure 1