I'm not sure if it is the right forum to address my question. We have GE 9E frame gas tubines and as scheduled overhaul is on the horizon we are planning the jobs to be done. We suspect that misalignment is high between Gas turbine and generator bearings. We'd like to check it using laser alignment equipment. As per my experiance we need to uncouple the units to take the readings. However the timing of outage is short and coupling bolts are not availaable at site. GE specialists when we consulted them say that it is OK to check alignment without uncoupling units, on coupled machine. My concern is if the readings will be reliable in this case.?
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Gas turbine alignment 2
- Thread starter DUISENM69
- Start date
in my experience of laser alignment equipment, the alignment is normally carried out with units coupled together e.g. pumps. The following link is to a company we use and they have recently launched a package for gas turbine alignment.
I'm not familar with CTs, but I'm interested in your question.
Is the CT rotor to generator coupling "solid", or is it through a flexiable section.
If the coupling is a flexable section like a gear/spline coupling hub or the dry flex plate type, then coupling checking while assembled may work. (the theroy is that it will, but I had a very bad experance on a feed pump turbine)
If the coupling is solid, I don't see how it can work (thus the reason for my intrest in resposes to your question) an alternative to coupling check could be measuring bearing loading with a swing check.
When I searched the site mentioned in K9ine responses, I only saw their shaft alignment equipment on flexibale couplings.
Do you have a non OEM consulatant to ask? I know of several in the US that if I was faced with this problem I would have to contact.
Good luck with your overhaul.
Is the CT rotor to generator coupling "solid", or is it through a flexiable section.
If the coupling is a flexable section like a gear/spline coupling hub or the dry flex plate type, then coupling checking while assembled may work. (the theroy is that it will, but I had a very bad experance on a feed pump turbine)
If the coupling is solid, I don't see how it can work (thus the reason for my intrest in resposes to your question) an alternative to coupling check could be measuring bearing loading with a swing check.
When I searched the site mentioned in K9ine responses, I only saw their shaft alignment equipment on flexibale couplings.
Do you have a non OEM consulatant to ask? I know of several in the US that if I was faced with this problem I would have to contact.
Good luck with your overhaul.
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- #4
No flex plate coupling will carry this load. We reuse coupling bolts on the frame 6 units without problem. Also, if they have been lubed during assembly they should come apart ok. The coupling is flexible in terms of 70,000 HP but not for a laser alignment. If you check with laser and with shafts coupled you will always be wondering if the figures are correct. However if you do aligmnet check coupled and the figures are much greater than the bearing clearances will allow (and are repeatable in both directions of rotation) you will know roughly what your moves should be.
Regards
Regards
- Thread starter
- #5
Adam1,
Thanks for your reply you put in right words what my doubts were. I think we will do it coupled. Anyway it will not take too much time. We are still awaiting final confirmation from GE.
We understand that the bolts can be reused but anything may happen during dismantling and we would not like to bear LDs just because of one or two bolts.
Best regards,
Duisen
Thanks for your reply you put in right words what my doubts were. I think we will do it coupled. Anyway it will not take too much time. We are still awaiting final confirmation from GE.
We understand that the bolts can be reused but anything may happen during dismantling and we would not like to bear LDs just because of one or two bolts.
Best regards,
Duisen
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1
- #6
MDAAlignment
Mechanical
Not sure if you have done this alignment check or not, but I was involved with laser alignment at GE for years and have some experience in the area. The question about whether or not to break a coupling on a 7EA had come up many times in the US fleet. I believe that the 9E has the same type of Tube coupling as the 7EA. This design is not truely a Rigid/solid coupling but is more of a "Flexible Tube". How much flex, nobody could really tell me. My recommendation to those aligning this type of coupling is to break the coupling before measuring with a laser. If the coupling is in relatively good alignment, laser measurement taken with the coupling bolted and the coupling unbolted should be relatively close. The further out of alignment the rotors are however, the greater the difference between the two measuring methods.
When the tubular coupling shaft is connecting 2 shafts that have a gross missalignment, the shaft will tend to pull the shafts into a straigher line, than they would be in when unbolted, making the measured rim and face readings appear better than they truely are. This is why I do not recommend leaving the coupling bolted when taking readings. When it is broken, you truely know what you have. If you leave it bolted, you really do not know what your alignment is.
The couplings on frame 5 and 6 are truely a flexible design, and using the laser with the couplings bolted is definitely the way to go.
Hope this helps.
When the tubular coupling shaft is connecting 2 shafts that have a gross missalignment, the shaft will tend to pull the shafts into a straigher line, than they would be in when unbolted, making the measured rim and face readings appear better than they truely are. This is why I do not recommend leaving the coupling bolted when taking readings. When it is broken, you truely know what you have. If you leave it bolted, you really do not know what your alignment is.
The couplings on frame 5 and 6 are truely a flexible design, and using the laser with the couplings bolted is definitely the way to go.
Hope this helps.
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