Unbalance in compressor

[insptman]

We have problem in compressor vibration while unbalance increase in Outboard side (suction side). While we overhoul the compressor, we found in Inboard side (Discharge side) there are foreign material stuck in impeller (around 75 grams weight).
Can anyone explain this phenomena ? Why material that stuck in Inboard side made vibration increase in Outboard side ?

 

[GregLocock]

If you measure the influence coefficients for a two plane balance this may explain what is going on.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[insptman]

Thanks Greg,

This compressor consist of Recycle and Make up in single Shaft. It's mean Suction of Make up to be Outboard side and Discharge of Recycle to be outboard side. What we found only the clearance of Inboard bearing more than outboard bearing.

Best regards

 

[TPL]

Assuming this machine is monitored with proximity probes, what chance is there that the probes have been incorrectly labelled - ie those at the suction end are labelled as discharge end - easily done if the junction box containing the proximitors resembles a birs nest?

 

[Strong]

If this is a high speed centrifugal compressor operating above one or more critical speeds, then the rotor is considered flexible. I am not surprised that the opposite end showed higher vibrations than the end with the "apparent unbalance", especially if the impellers are overhung and outside the bearings. It may also depend on how it was originally "balanced". Make sure that it is rebalanced with proper procedure to precision tolerance.

Walt