Test & measurement


Fundamentals oF vibration analysis


Any machine with moving parts is designed to operate within a predefined level of vibration, but when this exceeds a certain threshold, it may be an indication that the machine is deteriorating. Therefore, vibration is a useful tool for investigating the status of rotating machinery, such as electric motors, pumps and generators. Here, Houghton International’s Chris Robson discusses the importance of vibration analysis. The data collected using either of these


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n any machine, the amount of vibration depends on a number of factors - the exciting force, the closeness of frequency


of these exciting forces to structural resonances or their multiples (harmonics), and the restraints the machine structure imposes to vibration. Vibration analysis is a non-intrusive, fast response, preventative maintenance solution that measures the vibration characteristics in rotating equipment based on three main parameters - velocity, displacement and acceleration. As part of a predictive maintenance strategy,


vibration analysis can prove crucial to predicting breakage, planning appropriate repair and substituting damaged parts before disaster strikes.


How does IT woRk? An accelerometer is used to collect vibration readings which are analysed by software systems to detect anomalies with the machine. Its sensors are connected to the vibrating structure and read the incoming electrical voltage generated by the piezoelectric crystal. The analysis can be conducted on either the time waveforms (amplitude versus time) or on the frequency spectrum (amplitude versus frequency) by applying a Fourier transform on the time waveforms or on both.


26 November 2021 Instrumentation Monthly A complex machine has many components,


each generating its own vibration. Critical components like bearings, impellers and shafts in large rotating equipment require a more in- depth evaluation. In this case, a spectrum analysis is better to get a clearer picture of the vibration frequency.


methods is then recorded using a vibration transducer at various points around an electric motor, pump or generator. A qualified engineer will then analyse the findings, flag issues and recommend actions to prevent breakdown.


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