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OLi

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Reply with quote  #16 
I would use standard output 100mV/g accels unless the Bently adapted ones give a more adapted output. I have seen Bently modules for standard or at least using IEPE 100mV/g sensors but it may be a newer version. Only reason to go down to 10mV/g sensor would be if you risk overloading them but that should not be the case if your gbx is reasonably healthy. Olov
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Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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Jmed

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Reply with quote  #17 
##Only reason to go down to 10mV/g sensor would be if you risk overloading them but that should not be the case if your gbx is reasonably healthy##

@oli
##when you overloading the 100mv/g ones## why you only think regarding the gbx vibration levels while the blower vibration levels are much higher ?

Jmed

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Reply with quote  #18 
@Johan
Still waiting for your comment on my post 8 days ago.
John from PA

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Reply with quote  #19 
An accelerometer on the steam turbine is an option under API 612.  Some guidance as to what you may learn can be found in the thread at http://www.eng-tips.com/viewthread.cfm?qid=90836.  

You probably should review API 670, the turbo machinery instrumentation specification.  Beyond defining the instrumentation needs, it has extensive details on the proper way of mounting the various devices.  Specifically, and as OLI has already stated, it calls for the accelerometer to meet

Principal axis sensitivity 100 mV/g ± 5 %
Amplitude linearity: 1 % from 0.1 g peak to 50 g peak d
Frequency response e: ±3 dB from 10 Hz to 10 kHz, referenced to the actual measured principal axis

This type device is readily available from a long list of vendors including GE/BN.

OLi

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Reply with quote  #20 
Steamturbine or blower rarely generate frequencies in the range that a GBX easily do by design so monitoring a hi speed hi load gbx with good results are more demanding and challenging compared to the other cases IMHO. In most cases people don't look at the problems but just pass them by using under rated transducers, mechanical filters or electrical filters, damping etc and thus not getting the monitoring they one day may need. Honestly it may not be so often. I have only seen, heard of 2-3 turbine related gbx cases here in 20 years but once in a while it can be worth it, delivery of a turbine gbx is at best months even just for the internals. 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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