Just look these plots.
Steam turbine drive end side shaft vibration fluctuating 60µm to 10 µm continuously.
We observed this fluctuation only in turbine drive end side only, Non drive end side it is ok. How can we avoid this problem????????????

Thanks.
Ranga

STG_A.xls (198 Kb, 94 downloads)

The data suggests a classic rub.

Have you done any maintenance on this machine recently? What sort of seals are present? Have the seals been disturbed?

You might want try a couple of manually initiated trips and restarts to see if this overcomes the problem

Are you running the turbine under reduced load? Reduce speed and see.
Regards

Gents,
now there is no fluctuation,
we found that LP extration steam flow not steady we adjust this .please refer the attached plots.

thanks,
Ranga

Book1.xls (114 Kb, 51 downloads)

looks like Buzz called it

I have read about phase and amplitude fluctuation as a sequence which starts with a rub generating heat and causing shaft to bow, then the rub clears itself, shaft cools down and straightens out, then rub starts all over again, and so on.

Sounds OK, but why the rest of the plots do not support the "rub" theory?

Could shaft's CL average position within the annulus ( plot is not provided) shed some light?

Also, could orbits acquired at MAX vibration amplitude help to recognize a rub?

What is the clearance in this bearing?

David_G, at least within the plot formats submitted there is one other format that shows a subtle indicator of a rub. That is the relatively flat side to the direct orbit.

You are correct as well in that other formats also might support the conclusion.

John from PA

There are other subtle clues such as a constant shifting phase lag against rotation and polar plot shape with reference to the heavy spot. The normal heavy spot is ~170 degrees and polar plot with rub has highest amplitude around this area. The opposite site of the polar plot at 330 degrees, the vibration is ~ .5 mils PK-PK. The total change in rotor displacement is the highest amplitude plus the smallest for this particular case, which could have been up to 3 mils.