Turbine Vibration Analysis

Ele eng - welcome.

Need more information. Can tell you nothing of any use from the information given.

Is the peak a multiple of 1500, then what multiple, or is it at 1500? What is the magnitude? A scan of the spectrum would be useful too.

What size is the set, type of coupling, type of bearings etc etc etc - -----

Is the driver or the driven vibrating? Which bearing?

Also find out how many teeth are on all of the reduction gear box gears.

And what type of bearings (all), white metal, tilt pad , roller etc....

What kind of auxilliary equipment is hanging off the RGB?

Is there a mechanical lube pump?

Spectra for all bearings should be analysed. For both turbine and generator.

You analyze vibration as related to rotating speed. If you can look at it that way someone can probably give you some good advise. When you say the base speed, are you talking about rotating speed of the turbine? If so, what is the multiple. 2 times, 4 times ? That will help a lot.

There are people who make their living figuring out just what is causing a particular vibration issue. I have no idea where you are but surely there is an outfit near by who could come in and do the analysis for you.

I have seen vibration problems on turbomachinery caused by every thing from excessive oil pressure to missing blades on some of the stages. Other odd causes of vibration I have seen are a substitute coupling bolt, cracked rotor shaft, dragging seals, excessively loose fit of the pinion gear on its shaft in the gear reduction box, dragging machine guards, bad bearings on the oil pump drive gear reduction, bent speed wheel shaft extension, improper gap between the PMG rotor and stator causing it to drag when it heated up.

There are a lot of things to go wrong with a turbine, its auxiliaries and loads. Not all of them are visible without specialized equipment and skilled people to interpret the results.

If you will explain all of the available symptoms and give some information about the type of turbine, manufacturer and load perhaps one of these enlightened people will be willing to offer you a hint or two. :)

Good luck!
TT3

Vibration is on generator side

Vibration shows in 2X, 3X, 4X

vibration on all generator point vertical, horiz, axial in front and rear

vibration limits was 0.2-0.25 and increased to 0.35-0.5within 10 days

Generator is on 2 roller bearing single row bearing

Driven by turbine then reduction gear box however vibration reading for both turbine and gear box are normal

Coupling type is rigid coupling I have already checked for misalignment between generator and gear box but they re ok ( within limits)

Ele

Difficult to say for certain from a distance, but from what I can make out from the spectra that you posted (please correct me if I am not seeing this correctly they are not very clear) you have the following:

OB H you have 3x as your dominant frequency.

OB V 2x and 4x dominant with 1x quite small.

IB H lower than OB but 1x and 2x almost the same amplitude

IB V 2x is dominant frequency.

You do not have an out of balance problem. You almost certainly have a misalignment problem possibly combined with some looseness in the bearings or the foundation. Look to coupling alignment as well as the alignment of the bearings.

You may also want to look for sidebands around your 2x peaks in more detail to eliminate the possibility of this being a rotor problem - eccentric air gap or some such. Taking note of how these vibrations change from load to no load will also give you an indication of whether the rotor could be part of the problem.

When you say "rigid" coupling is this correct - no flexible element? This is not that common with two roller bearing on the generator. Are they really roller bearings or are they spherical rollers?