Axiall movement

Dear all

What courses of high axial movement at gas turbine? I face to axial displacement alarm limit of Siemens Sgt 600gas turbine. They have six sets of gas turbine which only one of them have high axial movement. All operation conditions and process were the same.

Pls, share your opinion.

Best regards 

Original Post

Aziz,

 

Analyzing axial position is a bit tricky, unlike what some operators think. Please share more details so the members can help.

 

For instance, post shaft position, unit load and thrust bearing temp with time. Has the unit been repaired recently? Is this issue old or recent?

 

Regards- Ali M. Al-Shurafa

Shurafa posted:

Aziz,

 

Analyzing axial position is a bit tricky, unlike what some operators think. Please share more details so the members can help.

 

For instance, post shaft position, unit load and thrust bearing temp with time. Has the unit been repaired recently? Is this issue old or recent?

 

Regards- Ali M. Al-Shurafa

Dear Ali

All process parameters are ok. All vibrations are ok. This turbine installed 3 years ago. For the first start axially movement up to. 0.18mm.after that this moment growing up slowly up to  -0.22 mm )alarm limit. trip value for this turbine is 0.3mm.where  should  I 

Regards

How does this value compare to the axial float check?  This may not be too alarming.

Depending upon the design of a gas turbine, the thrust balance may change from one side (of thrust) to the other during a start and the loading; the manufacturer would have such details.  Data from your other turbines could help explain this.  

You should measure the axial float accurately and repeatably.  To do so one needs to push evenly and consistently.  The manufacturer may have a procedure for this.  I have seen manufacturers with some variance on their own measurements.  A good measurement will help evaluate your data. 

Comparing to other turbines can help give a reference.  Tracking vs. loading can determine the typical affect for this design.  

William_C._Foiles posted:

How does this value compare to the axial float check?  This may not be too alarming.

Depending upon the design of a gas turbine, the thrust balance may change from one side (of thrust) to the other during a start and the loading; the manufacturer would have such details.  Data from your other turbines could help explain this.  

You should measure the axial float accurately and repeatably.  To do so one needs to push evenly and consistently.  The manufacturer may have a procedure for this.  I have seen manufacturers with some variance on their own measurements.  A good measurement will help evaluate your data. 

Comparing to other turbines can help give a reference.  Tracking vs. loading can determine the typical effect for this design.  

Thanks, Williams

Other turbines work under limit axially movement value .all turbines at the same load and speed.

  I am suspicious to zero setting of the axial sensor. I agree with you. I seem not real alarm. Now we can not shut down to check axially floating.

But as you mentioned if we tracking this axial movement vs load, we should see increasing of this value by a load of operation. you mean by comparing this condition to another turbine we should expect the same change of axial movement?

I've only worked on one of those machines and as best I recall it used a double helical gearbox to reduce the power turbine speed from about 7700 RPM down to the generator speed.  So as "William" has stated 

"You should measure the axial float accurately and repeatably.  To do so one needs to push evenly and consistently.  The manufacturer may have a procedure for this."

It may even be difficult to compare axial float settings from turbine to turbine.  Things like physical positioning of the rotors in the gearbox and coupling pre-stretch (if used) may have large impact on the running data.

aziz58 posted:

Thanks, Williams

Other turbines work under limit axially movement value .all turbines at the same load and speed.

  I am suspicious to zero setting of the axial sensor. I agree with you. I seem not real alarm. Now we can not shut down to check axially floating.

But as you mentioned if we tracking this axial movement vs load, we should see increasing of this value by a load of operation. you mean by comparing this condition to another turbine we should expect the same change of axial movement?

My intent was not imply that axial position would necessarily purely increase with loading.  The position may change directions, depending upon the turbine design.

Add Reply

×
×
×
×