Is there any provision to add mass for mass balancing of Compressor-Turbine Shaft without opening any Compressor casing? We need to conduct mass balancing of the Compressor as Vibration is alarming. The mass unbalance has been identified as the root cause of vibration after conducting vibration analysis.

Please let us know if there is any provision or not.

 

This prompts more questions than answers. It is possible to trim balance a Frame 6 at the accessory coupling bolts or at the load coupling bolts to try and reduce particularly start-up high vibrations.

Questions are, how did you arrive at this increased vibration situation? Have you just completed an overhaul? Did you re-bucket any of the rotor stages? Did you do any re-alignment. Before you rush into field balancing you need to see if it is feasible. If the cause is any of the above it would be much more sensible to correct the problem at the root cause. Can you show us some results of your vibration analysis?

 

Dear Bob Johnston,

Thanks for your reply. As I can't attach documents here therefore, I'm unable to give you the vibration analysis result. The status of the turbine was given in the following thread. Please go through the link-
http://www.control.com/thread/1334256071#1334413028

Here I want to add some more information that During the last shutdown of above 8 months the compressor and turbine was not protected well. Therefore the compressor rotor was rusted much and it lost some mass. Another information, During the vibration analysis axial movement of the compressor-turbine rotor was found 8-30 m/s below 20 MW and 20-35mm/s above 22 MW which indicates another problem in addition to mass unbalance.

Please share your feelings.

<b>moderator's note:</b> people often upload documents to one of the download sites for people. You might try that.

 

Still your information is pretty basic to discuss or make a decision on vibrations. You state some axial vibrations but don't say which location they were taken at and what is the predominant frequency. Anyway, given the rotor corrossion that you have described and the axial problems (which look like possible mis-alignment), I would say that you have no recourse but to remove the rotor, get it unstacked and re-stacked and then high speed balanced. I don't know where you are located, or I could suggest some repairers who could help.

 

Dear Bob,

The axial vibration measurement has been taken from No.-1 Bearing side and the Axial vibration is the predominant one. The location of the turbine is in Bangladesh.

 

Looking over the history of the machine, It kind of looks like you have maybe been experiencing some kind of axial problem even before changing the inactive thrust. It's not very normal to have to replace inactive thrust bearings and now you are experiencing high x1 axial. Maybe some damage was done to a compressor stage after your cleaning process and this is causing unusual axial forces. A good vibration analyst could maybe help, I certainly wouldn't advise a field balance. I think the rotor needs to come out. BHEL in India should be able to help (If you don't know them, Google for them).

Where are you in Bangladesh? I've done a few jobs there, one in Mymensingh and another near Sylhet.