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Vibration Analysis

This is by and large the most widely extended technique employed in the field of predictive maintenance, because it is used to detect with a high level of certainty a wide range of defects in rotating equipment.

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By means of comparing different measurements taken over a period of time, we can establish patterns and can anticipate part failure with a high level of certainty.  Because of this, it is important to take measurements over regular intervals, which will allow more accurate diagnoses, especially if taken over shorter intervals.

What is it?

It is the measurement of vibrations at different points of the machine and in different directions, using transducers which convert a given physical magnitude (displacement, speed, acceleration) in electrical signals which are received by an analyzer.  The most widely users transducers are accelerometers.

 

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The analyzer is capable of processing these electrical signals and by using the Fast Fourier Transform (FFT) we visualize the spectrum of vibration, which is nothing more than a graph where we represent in the abscissa the different frequencies of vibration (which indicates the nature of the fault) and in the ordinate the amplitude of vibration at each frequency (which gives us an idea of the severity of failure)

 


The study of these spectra, for every point and direction, and its evolution over time is what allows us to establish definite conclusions about the condition of the machine as a whole and the state of its different parts.

 

Advantages

  • It can be used with practically every type of rotating machinery
  • It detects a large majority of the types of failure of rotating machinery
  • Well-established and accurate technique

Disadvantages

  • Although it is easy to collect data, analysis and establishment of conclusions is complex, requiring highly-trained and experienced personnel

 

ventilador_de_horno_pqWhat types of failure does it detect?

  • Problems with bearings
  • Unbalance
  • Misalignments
  • Clearances and looseness
  • Loose bolts
  • Rubbing or blows
  • Inadequate work support or is in poor condition
  • Lubrication failure (either too much or too little)
  • Problems arising from electrical motors (broken bars, phase imbalance, stator eccentricity, etc...)
  • Non-level electric motor supports
  • Gear problems
  • Cavitation or flow turbulences in pumps, fans, turbines, etc…
  • Fissures in or failure of impellor rotor blades, turbine rotors or a fan blades
  • Practically the wide whole range of the most typical types of failure in rotating machinery are detected con an adequate vibration analysis.

 

Applications

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This method of analysis is performed in practically every type of rotating machinery.  Classic examples are pumps, reducers, motors, turbines, rollers, fans, centrifugal pumps, etc…

It should be noted that the methods used can vary according to machinery and application, so that the predictive maintenance service is adapted towards the requirements of each customer.

Method of Deployment

Whichever way we choose to measure and process the data, it is always necessary to create and set up the parameters of a database  which contains the kinds of machines, the points to be measured, the magnitudes which will be measured, alarm levels, failure modes, etc…

 

Data Acquisition

Manual Method

A technician directly measures a previously assigned point with a vibration data collector and a portable accelerometer. This can be done by an Adendo technician or the customer's own staff, provided they have a data collector. This is especially interesting for companies with a large number of machines, or various companies within the same group, because the investment in a single data collector for them all pays for itself very quickly.

In machines with difficult or restricted access,  accelerometers are installed permanently at each required point and associated direction, and these are wired to a junction box where the operator connects the data collector and records the action.

 

Machine Monitoring

The accelerometers (and other variables to be controlled such as temperature, pressure, etc ...), instead of being wired to a simple junction box, are wired to a unit capable of collecting, processing and storing data. This process can be performed intermittently (multiplexed systems) or in continuous mode for machines that require comprehensive monitoring.

Data Processing

When it is the case that one of our technicians makes the readings, obviously, we will load that information to the existing database, analyze it and draft the corresponding report, advising the customer immediately if any alarms are observed.

In cases where data acquisition is performed by the client's own staff, they can send the information via the Internet, and we update and maintain their database, analyze the information and issue a report.

On monitored systems, this process can even be executed automatically, sending data via the Internet, GSM or radio at the time of capture.

 
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