#WishIknew – What does vibration analysis detect?


When you have a question about process automation that needs a short answer, let us know with #WishIknew and @Visaya! We’ll reply with a #WishIknew post. It’ll give a quick explanation, then some related articles, videos, or reviews if you want to know more.

I wish I knew what vibration analysis detects!

Okay, let’s start by classifying the methods based on the problems they solve. We have three categories:

  1. Equilibrium problems have to do with structural or mechanical changes from static or repetitive loadings.
  2. Eigenvalue problems, as an extension of equilibrium problems, can identify events such as resonance and buckling.
  3. Propagation problems outline the stresses of a system under time-varying loading.  

So vibration analysis consists of listening to a machine. As each component vibrates, it makes its own special noise that leaves a “fingerprint” in the spectrum as a linear pattern.

Now let’s talk about some basic terms in the study of vibration signals. So consider a rotating fan with n number of vanes and a constant energy supply. This fan would have a specific simple harmonic motion (SHM) of a certain frequencyamplitude, and time.

Let’s assume the fan rotates five times a second. Okay, suppose we add weight on one of the vanes. Now, its SHM changes, which means changes to its frequency, amplitude, and time.

  • Frequency: The vibration on the fan will produce twice as much effect, so the frequency increases from 5 hertz to 10 to compensate for the loss.
  • Amplitude: The amplitude will increase proportionally to the speed because of the weight on the vane. The weight causes an imbalance, which in turn causes irregular amplitudes.
  • Time: The time decrease, as it and frequency are inversely proportional to each other. To compensate for the weight, the wave takes more time to complete its oscillation.

So vibration analysis sure does detect a lot of interesting stuff! If only I could detect your state of mind right now. Hmmm, I see either a clear mind with no doubts or a nitpicky one ready to fire questions. Feel free to fire them all!

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