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weller

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Reply with quote  #16 
I like the idea presented in the paper of using multiple parameters and assigning a risk value. This might help "standardize" the fault methodology. It also seems to help when making a call for equipment repair. Its not and end all but our groups goal is accurate and repeatable analysis to further reliability.
dnk

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Reply with quote  #17 
I always used all three, demode, acceleration and velocity. I would trend acceleration until I saw harmonics in velocity. At that point I would write a W.O. to get replacement on the schedule. When I saw harmonics with side bands, would notify maintenance manager to replace at earliest opportunity.
electricpete

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Reply with quote  #18 

Quote:
I like the idea presented in the paper of using multiple parameters and assigning a risk value. This might help "standardize" the fault methodology. It also seems to help when making a call for equipment repair. Its not and end all but our groups goal is accurate and repeatable analysis to further reliability.

I didn’t notice that, but seems relevant to our discussion.

Here’s equation 4
(I’d post a screenshot, but it was Graney  [rofl]
.....haha. I wrote this whole post just so I could get that joke in!):

ARI = sqrt(DFI^2 + B^2)

Where

ARI = Aggregate Risk Indicator

B = Bearing stage estimate… what “stage” the failure is in (1-4) based on the other methods of the paper, like tables 1,2,3.

DFI = Discrete Frequency Indicator – assigned 1-4 based on relationship of overall velocity to the lower alarm value (1 less than alarm, 2 at alarmk 3 1.5x alarm, 4 2x alarm).  The idea being that if velocity is high, the defect may be more loaded (misalignment, unbalance). Or maybe some other factors. 

It seems like a reasonable construct in theory.  First impression though… I don’t foresee I’ll be using it for any decision making.

Ralph Stewart

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Reply with quote  #19 
Quote:
so far no negative feedback


Sounds like you are doing something right,[smile] not to say the "Techos" are not right in their work also. Just the difference in people, one group is comfortable with velocity and another with Acceleration.

Can't judge one or the other until proven which one is or is not wrong.

I once talked to a guy some 30 plus years ago at a CSI "User's Conference" (old name for the conference) who analyzed totally in displacement. Hard to comprehend that, but he did not state any frequency area of the data he had to analyze. May have all been "slow" 1x with the bearing's frequencies also being quite low.[confused]

Use of both, Velocity and Acceleration, probably would be the thing to do. But that is just me and my opinion.[cool] 

Happy Vibrations and Have a Great Day,
Ralph

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Ralph Stewart
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ericpostrado

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Reply with quote  #20 
Early bearing defects  can be found only  in the the higher frequency , normally we are using acceleration , "peakvue "  for CSI  and  g's  ( acceleration ) for Microlog. The good thing for  "peakue "its separated the Low Frequency like looseness , imbalance etc. 
In my opinion If we will use velocity for bearing defects it is too late for us to have a good planning since the equipment  already in the Failure stage. 
OLi

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Reply with quote  #21 
That is if you only look at the velocity 10-1000Hz, if you let the velocity give you data up to 12kHz or more it will also serve you more information.
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