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VibraMac

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Reply with quote  #1 
Has any body attempted to LS balance turbo-compressor impellers on the spare pinion and has proved successful.  Want to check balance the inidividual impellers without strippng the compressor.  Considering taking the operational impellers off the pinion that is in the compressor and balance them on the spare pinion and then refit them.  Type of pinion/impeller arrangement is attached.

th[5].jpg 

Have had success on a slightly different situation, where the impeller was removed, cleaned and refitted after suffering from a leaking cooler.   

OLi

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Reply with quote  #2 
What op speed? What residual unbalance required? I worry about the centering reproducability from place to place. At least keep track of angular/phase disc position on the shafts so you replace as much as possible to the same place. Is the balancing speed within the OEM suggested? I once balanced a gasturbine disc by finding out the residual unbalance when placed in a fixture in the balancing machine as it was running fine before taking it out, then some worn blades was replaced and we trim the residual unbalance to be as near as the original as we could. I didn't have to go to Greece to trim on site so it worked. 
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VibraMac

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Reply with quote  #3 
OP speed is 12750 rpm.  Situation is the pinion/impellers were balanced and fitted; however, stage 2 rubbed on start up upsetting the balance.  To prevent a complete compresssor strip (6 stages) and 5 days to strip and rebulild,  the idea was to rebalance the impeller after repair.  The original unit was balanced to VDI 2060: G1 and the impellers sent for balancing would comply.  The impellers are located on the pinion by hirth tooth and a single locating pin (ie can only go on one way).
OLi

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Reply with quote  #4 
So if you balance them to next better, G 0.4 I think you would then in principle be ok but it may be a bit fiddly. Would you have the plan B option to trim assembled?
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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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VibraMac

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Reply with quote  #5 
Plan B - Attempt to trim balance in-situ is possible (done once before); however, very time consuming.  Taking and refitting pipework, GV etc as well as the impeller to fit weight behind the wheel and to repeat a minimum of three times. 

I believe my proposal would suffice to achieve satisfactory results to at least get the compressor into service (no production for the past 11 days and tanks are empty!!!!!). 


 
OLi

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Reply with quote  #6 
It is worth a try and in worst case you have a plan B. Balancing a nuke turbine is minimum 3 day turnaround for a weight modification/insertion so some luck and patience is always good to have. I think it should work, only thing you can't control is the residual unbalance of the spare compared with the operatinga and repeatability of the centering/mounting operation but it is not much to do part from hoping they are of good and about equal quality and they should be that I guess, how they add up in the end you will eventually find out. Hoping for the best. Olov
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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
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