High Vibration in a Gas Turbine

Respected Members;

We have face a very critical situation regarding the vibration in a Gas Turbine CENTAUR 40 model by Solar Turbines.

Before explanation of the nature of the vibration, I share the machine design data for reach the root cause.

1. 11 Stage Axial compressor.

2. 15015 RPM of the Turbine engine.

3. Two shaft Gas Turbine.

4. There are 3 tilt Pad bearings on turbine engine side.

5. First critical speed about 28 % and second critical speed at 56%.

6. OR36 with NVGATE and Vibroport 41 is used to capture the FFT or Time wave forms. There is no option in the turbine for phase analysis.

Now i explain the fault for diagnostic.

 When the turbine start every thing is going fine. No High vibration found at any frequency.

When engine reaches at 87% the Peak at 2X is going to increase while 1 X is not increasing and 2X reaches at the alarm value as speed increase but 2 X goes down when engine achieved 92 % RPM.  It means the vibration found high between 87 to 92 % RPM band and just on the diffuser section  where bearing # 2 found. 

On the other hand the vibration on bearing 1 and bearing 3 is well with in limit.

Here i attached some data in picture format which helpful for discussion.

I describe the file name and their detail

1. GP-V and GP_H.JPG shows the spectrum during 87 to 92% band.

2. SKID_SPECTRUM.JPG  shows the FFT at skid base.

3. support_FWD.JPG shows the FFT at support FWD side of the engine.

File 2 and 3 FFT taken to check the soft footing and looseness.

The other is the view of the diffuse section where velocity probes are attached.

Here is also attach a Time wave form get by cross chanel.

One thing i observe this vibration is also occur at deceleration at the same band.

also if i stay the engine between this band for 6 to 10 minutes the 2 X peak starts to goes down but still high.

If more data required please feel free to ask and advise me how i fix it?

GP_H means Gas producer Horizontal, and GP_V means at vertical.

Regards 

GP_VERTCAL AND HORZ AT ENGINESKID AND SUPPORTSKID_SPECTRUMSUPPRT FWDTIME WAVE FORMVIEW_TURBINE

Attachments

Photos (6)
Original Post

When engine reaches at 87% the Peak at 2X is going to increase while 1 X is not increasing and 2X reaches at the alarm value as speed increase but 2 X goes down when engine achieved 92 % RPM.  It means the vibration found high between 87 to 92 % RPM band and just on the diffuser section  where bearing # 2 found. 

What do you mean by alarm value?  Is this a value that you have decided and not Solar?  Do you not have other vibration transducers on a Solar turbine, which are monitored with actual alarms?

You give but 1 turbine speed.  There are two speeds.  Any comment?

 

Hello, Good day

The alarm value is given by the OEM that set the value 0.17IPS FOR A SINGLE PEAK BETWEEN 15 hz to 2khz. 

The over all alarm value is 0.25 IPS.

I understand ur next question about two speeds, that 87 to ,92 percent the peak at 2X is going to high but before and after this speed band its value is well within limit

If u have any other meaning please explain little more

Regards

Interesting, the Solar turbines that I have seen use shaft relative probes for the bearings (forget old Saturns for this).  Are these Solar supplied?  On an epicyclic output gear?  Some other Solar 'custom (or selectable) feature?'  

I am surprised that I haven't run into these alarms from Solar and am interested in finding out more.

The meaningfulness of this frequency range on a gas turbine, I am more familiar.  Most manufacturers do not use that high a frequency, perhaps not that low either.  Many other frequencies (particularly with seismic measurements) will show up on a GT.  Blading, all that flow energy, especially in the exhaust, depending upon the location bleed valves (and these can have vibration faults as well as other faults).  They have flexible supports and a flexible casing.  Is there some p[lace to find this information on the Solar site; otherwise, I'll have to ask a Solar guy who is onsite.  

Bill, the Centaur 40 gas turbine generator arrangement is a single-shaft gt with tilt pad bearings. The monitoring system on the turbine is velocity based. The gearbox is an epicyclic, planetary arrangement as I recall and it has an accelerometer based system. The 4-pole generator can be equipped with proximity probes.

In the mechanical drive the Centaur 40 gt is a two-shaft, still with tilt pad bearings. The instrumentation system is velocity based. I do not recall ever seeing one with proximity probes, although that is not to say they might exist.

Early on the OP stated the turbine was a two-shaft, so I assume this is a mechanical drive arrangement although the driven machine hasn't been mentioned.

 

The original post indicated that his turbine was a two shafts GT.

1. 11 Stage Axial compressor.

2. 15015 RPM of the Turbine engine.

3. Two shaft Gas Turbine.

4. There are 3 tilt Pad bearings on turbine engine side.

It does matter what we are talking about.  We have both types of Centaurs.  The closest Solar turbine to me is in the next building, but it is one of those rarer Mercury 50's.  

William_C._Foiles posted:

The closest Solar turbine to me is in the next building, but it is one of those rarer Mercury 50's.  

LOL, at my former gear employer, they used to refer to the Mercury 50 as the "regurgitated" as opposed to Solar's name "Recuperated".  We were never fortunate enough to get the contract to supply the epicyclic gearboxes.

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