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Calculating Absolute Shaft Vibration

Is there a way to create a feature to calculate absolute shaft vibration.  I have eddy current probes and velocity probes installed and would like to calculate the absolute and trend it.

Thanks,

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Re: Calculating Absolute Shaft Vibration

What does "absolute" mean to you?

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Re: Calculating Absolute Shaft Vibration

This is a request that we've heard a couple times and hopefully we'll be able to get to it in the near future.  So the short answer is that as of Insight 3.6 you can't do this natively.

For the calculation, would you expect that it would be the sum of the prox probe pk-pk feature and the (integrated) velocity probe pk-pk?

Are your sensors mounted in the same direction or would we need to account for different probe angles?  Without having thought too much about it, seems like this could be accomplished with some relatively simple vector math.  With this approach, would you want to see the result in terms of maybe something like absolute vertical and absolute horizontal?

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Re: Calculating Absolute Shaft Vibration

Thanks Alan.

Yes, this is the perfect test case. This is a large turbine with both prox probes and velocity coils in the same location and direction.  We are getting the calculation from the control system already, so this gives us a way to check our math and phase angles.

We can calculate both directions (X, Y).

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Re: Calculating Absolute Shaft Vibration

RavinsFan

Sorry, I should have put more description into the question.

On turbo machinery (fluid film sleeve bearings) we like to see this measurement.

Shaft Absolute
Shaft Absolute is the measurement of the shaft's motion relative to free space (or absolute). Shaft Absolute can be measured two (2) ways, the first being electronically summing the signals of both a Eddy Probe measuring shaft relative and a accelerometer measuring case absolute, the second being using a shaft rider which is a spring mounted device that physically rides on the surface of the shaft, normally a velocity sensor integrated to displacement is mounted on top of the shaft rider. Shaft Absolute is normally used where the rotating assembly is five (5) or more times heavier than the case of the machine.

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