Saturday Jun 24 2017

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Introduction Of NDT Technology

Enhanced Vibration Monitoring (High & Low Frequency Approach)

What is it?

Vibration monitoring normally apply to rotating machine in monitoring and measuring undesired mechanical component fatigue and breakdown. All rotating machine vibrates to some degree, however, the vibration intensity become drastic as the component is reaching the end of its product life.

Vibration monitoring is essential to trigger early alarm on pre-failure component (due to wear and tear) before the related rotating machine come to failure / stoppage.

Enhanced vibration analysis integrates 2 different frequency bandwidths in analyzing the vibration signal obtained from the rotating machine.

High frequency vibration analysis, ranging up to 100kHz, enable the early detection of high frequency ‘footprint’ generated by the rotating machine, as well as, to locate and pinpointing the defects long before the said defects become a major problem.

Low frequency vibration analysis, ranging up to 20kHz, enable continuous monitoring on the deterioration rate of the said high frequency footprint before the component reach the end of its product life. Besides, low frequency vibration analysis also detecting the vibration symptom which may due to misalignment, unbalance, over tension, looseness and etc.

Thus, the enhanced vibration analysis will cover the full range of the rotating machine’s vibration symptom, filter and locate the vibration source, as well as, speed up the diagnosis and analysis process, providing a more efficient and accurate monitoring result.

How does it works?

Any high frequency signals produced will be mixed with a broad range of sound most of which need to be filtered out in order to collect good & solid high frequency data. High frequency analyzer convert high frequency signal into an audible sound for the inspector recognition and analyze based on industry standard or individual component characteristic.

As high frequency approach enable higher defect detection rate than the conventional mechanical vibration approach, cautionary step required to further trend the defect deterioration rate before the call for bearing repair being make. A stressed bearing will first appear as a crack one to three thousands below the race surface, where it is obviously cannot be seen but heard as every time a ball rolls over the top of the crack emitting an ultrasonic “squeak”.

Whereas, low frequency approach will continuously monitor the mechanical vibration signatures resulting from faults, that are known to have developed without significant contribution to the overall vibration value at its early stage.

Some of the mechanical vibration failure problems that can be detected are:

  • Rotor unbalance
  • Mechanical looseness
  • Bearing defects
  • Gear fault
  • Shaft misalignment
  • Rotation looseness or unbalance
  • Loose components
  • Fan blade unbalance
  • Soft structure and etc.

An early call for repair will cause the maintenance crew repairs the unit noting no visible defects thus damaging credibility to able to call these problems effectively. There is also problem of cost since the components could be run a long time without damage to the machine or impact to the operation. Thus, with combination of high and low frequency vibration analysis (enhanced vibration monitoring), continuous monitoring and trending is an valuable tools to recognize the components until its degradation ran farther up the failure curve. This way the components can have the last drop of usefulness squeezed out of them as possible without impacting the operation.

 

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