Can anyone help me about the below plot orbit.i am expecting orbit looks like some rub.vib is 40mic.it is steam turbine and 10000rpm.please share ur views.spectreum has 1x and 0.5x.there is no reverse procession at that time in waterfall and orbit.if it is a run what kind of rub it is either it occured in bearing or some other??

Thanks in advance.

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A rub is a good possibility.   I would plot (track) 1X amp and phase over time, also.

Depends upon the steam turbine if this is a worry or not.  Is there anything running at 1/2 X?  Cross-compound turbines will show this on the HP - and it could be normal.  Some TGs have excitors with a 1 to 2 speed ratio; those two can have this and be normal.

I did see a cross-compound turbine with a cracked pedestal show this on the HP, but this was not your usual case.  In that case the 1/2 X was probably mostly forced form the LP, but the effect may have been exaggerated.  

The difficulty of such cases (possible rub) is that identifying the exact location of the rubbing is difficult while the machine is running. Is it in the bearing, seals of the bearings, shaft end seals, inter-stage seals etc? Also, you would be lucky if you can fix the problem without shutting down the turbine.

 

Please keep us posted on the findings.

Regards- Ali M. Al-Shurafa

 

 

reddy33 posted:

Can anyone help me about the below plot orbit.i am expecting orbit looks like some rub.vib is 40mic.it is steam turbine and 10000rpm.please share ur views.spectreum has 1x and 0.5x.there is no reverse procession at that time in waterfall and orbit.if it is a run what kind of rub it is either it occured in bearing or some other??

Thanks in advance.

It is looks like your buying a car and you doesn't know the details of what you are buying. Anyhow, this is my perception in your limited data. Based on your orbit plot, its like a fluid problem ( likely fluid instabilities). But, if this orbit is from the steam Turbine side DE or NDE it is unlike an fluid issue due to tilting pad type bearing. But if it is in Generator its likely a cause. (i am not rooting that its most likely the cause with your given limited data). Please check the process related parameters like main steam temp , pressure and flow, thus this will help to figure out your problem.

Regards,

RG

Rotating Guy posted:

 

reddy33 posted:

Can anyone help me about the below plot orbit.i am expecting orbit looks like some rub.vib is 40mic.it is steam turbine and 10000rpm.please share ur views.spectreum has 1x and 0.5x.there is no reverse procession at that time in waterfall and orbit.if it is a run what kind of rub it is either it occured in bearing or some other??

Thanks in advance.

It is looks like your buying a car and you doesn't know the details of what you are buying. Anyhow, this is my perception in your limited data. Based on your orbit plot, its like a fluid problem ( likely fluid instabilities). But, if this orbit is from the steam Turbine side DE or NDE it is unlike an fluid issue due to tilting pad type bearing. But if it is in Generator its likely a cause. (i am not rooting that its most likely the cause with your given limited data). Please check the process related parameters like main steam temp , pressure and flow, thus this will help to figure out your problem.

Regards,

RG

Fluid induced instability doesn't occur with high 1x. Also oil whirl or whip will not lock at exact sub integer like .5x

For the limited amount of data in this case we can suspect rub or looseness or brg over clearance. The provided data is not enough judge.

Also like what ali al shurfa said if it is rub then where it is happening. Another question will be what is causing it bcz rub is secondary defect.

Vib282 posted:
Rotating Guy posted:

 

reddy33 posted:

Can anyone help me about the below plot orbit.i am expecting orbit looks like some rub.vib is 40mic.it is steam turbine and 10000rpm.please share ur views.spectreum has 1x and 0.5x.there is no reverse procession at that time in waterfall and orbit.if it is a run what kind of rub it is either it occured in bearing or some other??

Thanks in advance.

It is looks like your buying a car and you doesn't know the details of what you are buying. Anyhow, this is my perception in your limited data. Based on your orbit plot, its like a fluid problem ( likely fluid instabilities). But, if this orbit is from the steam Turbine side DE or NDE it is unlike an fluid issue due to tilting pad type bearing. But if it is in Generator its likely a cause. (i am not rooting that its most likely the cause with your given limited data). Please check the process related parameters like main steam temp , pressure and flow, thus this will help to figure out your problem.

Regards,

RG

Fluid induced instability doesn't occur with high 1x. Also oil whirl or whip will not lock at exact sub integer like .5x

For the limited amount of data in this case we can suspect rub or looseness or brg over clearance. The provided data is not enough judge.

Also like what ali al shurfa said if it is rub then where it is happening. Another question will be what is causing it bcz rub is secondary defect.

1. Process Parameter - MST, MSP, MSF and etc.

2. Alignment - Thermal growth, in certain parameters, MST affect the thermal growth of rotor thus it leads to rub and fliud instabilities.

3. Oil Temperature

4. etc. 

What brings the high 1x? unbalance? misalignment? also why is there 0.5x? Rub? what knid of rub? partial rub? dynamic fluid force? thermal unbalance? there is a lot of speculation will foreseen in the given limited data. Anyhow. i will stick to fluid instabilities.

As far my experience concern and with my case studies and analysis., fluid instabilities will relate to 0.5x to 0.8x.

Cheer up! 

RG

Everything you wanted to know about rubs can be found in a presentation by John Yu, PhD of GE/BN.  See Rub, Morton Effect, Parametric Excitation, and Shaft Crack in Rotating Machinery - Real Cases.  John's a former co-worker of mine from days prior to my retirement.

Another good article on the Morton Effect, a phenomenon that has characteristics to a rub can be found at Morton Effect.  

here are the few plots for further discussion.

hintn 25-07-19 morning 6:52AM there was a sudden drop in RPM from 10500 to 10000RPM with in a min span RPM reached to 10500RPM during same time orbit seperated.upto 3days occassionally  observed seperated orbit same time 0.5X peak observed

 thanks 

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Hi All,

Can anyone help me what's wrong with our Generator by the orbit plot & spectrum details attached?

Generator is driven by Steam Turbine running at 3600 RPM. This is a newly installed equipment and on commissioning stage. My initial observation, there is a misalignment on the shaft of the Generator.

Please see the attached data.

Thank you very much.

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white walker posted:

here are the few plots for further discussion.

hintn 25-07-19 morning 6:52AM there was a sudden drop in RPM from 10500 to 10000RPM with in a min span RPM reached to 10500RPM during same time orbit seperated.upto 3days occassionally  observed seperated orbit same time 0.5X peak observed

 thanks 

do you mean that when speed reduced the 0.5x vanished ??

white walker posted:

here are the few plots for further discussion.

hintn 25-07-19 morning 6:52AM there was a sudden drop in RPM from 10500 to 10000RPM with in a min span RPM reached to 10500RPM during same time orbit seperated.upto 3days occassionally  observed seperated orbit same time 0.5X peak observed

 thanks 

Hi, can you share more detail please, also if you share the filtered orbit also please share the unfiltered, i cannot seen your purpose on sharing 1x filtered orbit alone. 

Why there is a sudden drop of RPM? have you gone in any testing? or your running steady state operation then the RPM sudden change? any problem in line frequency?

How many bearing do you have? 4 bearing? if 4, can you share to use the data of Bearing 2,3,4 = Turbine DE, Gen DE an NDE.

Also whats the point in sharing polar plot and SCL plot during steady state? 

When you share a data to someone else for review please give as much a right details. 

regards,

rg

maximize posted:

Hi All,

Can anyone help me what's wrong with our Generator by the orbit plot & spectrum details attached?

Generator is driven by Steam Turbine running at 3600 RPM. This is a newly installed equipment and on commissioning stage. My initial observation, there is a misalignment on the shaft of the Generator.

Please see the attached data.

Thank you very much.

Please start your own post

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