We have power generation Gas turbines (Frame 9- Type: PG9171E) in our company coupled to Alstom generators. At this time we have some technical problems as follows:

Severe oil mist contamination on the Generator rotor and stator due to transmission of oil mists produced in the generator bearings. Do you have solution for this problem? Is it necessary to have modification or changing of oil seals?

mail:[email protected]

 

Don't you have vapour extraction pump installed at that unit?

this vapour extraction pump sucks the vapour/mist from bearing top and throws out, little similar to mist eliminator.

It is very low capacity motor+blower set. (0.37KW).

 

Dear Sir

Thank you for your fast reply.

In reply to your question, We don't have any vacuum or extraction pump for eliminate vapors.

 

Is this a new problem? Usual question - have you been doing any maintenance? Sounds like a seal problem, how old is the machine? Can you please give as much more information as possible?

 

Dear einollahmoslehi;

I'm not familiar with Frame9 and even with no experience Alstom generator :-((

Usually GT lube oil is used to lubricate and cool down gen's bearings. And the vapor/mist <b>extractor</b> OR vapor/mist <b>separator</b> is installed/connected to the lube oil tank. If this system does NOT work properly, lube oil pressure will build up somewhere on the drain lines AND this somewhere could be the Gen's bearing. So you may need to check the lube oil tank pressure. Gen's bearing seals are usually very basic twin or triple Oring/Spring seals of both bearing sides. If lube oil is passing through these seals that means sealing is gone.

What about bearing temperature trend? Is there any changes? You may have bearing rubbing/wear?

Hope this is helpful
Regards
Karim

 

This is the first time after 10 years of installation that we have maintenance and rotor removal on this generators. our electrical Dep. believe that these generators do not need to any major overhaul and rotor checking and removal.

 

Did you remove the rotor or not?

 

hi,

it will be good to check the performance of oil mist eliminator. how much is the vacuum?

 

Dear einollahmoslehi;

> our electrical Dep. believe that these generators do not
> need to any major overhaul and rotor checking and removal.

Same thinking, here where I am, Over 10 years without maintenance and we lost PMG (Power Magnet Generator) and hopefully, We were lucky that time, we lost only the PMG and some exciter diodes. See thread:
http://control.com/thread/1443271297

The PMG bearings (ZZ ball bearing type) were stacked and Stator/Rotor completely Burnt.

After this incident, Inspections have been performed on the others gens and only the PMG bearings have been replaced. (we didn't followed the OEM recommendations, we just replaced bearings). The Gen OEM recommends replacing PMG every 12.000 running hours.

Regards
Karim

 

Yes, we remove the rotor, clean it and send it for balance check.

 

Hi Einollah,

some Alsthom generators employ sealing air on the generator bearings to prevent oil mist from coming out of the bearings. This sealing air is taken from the generator shaft fans (same air ducts that are supplying cooling air to the main exciter). However, be sure that the supply is taken from the high pressure side (cold air supply to exciter) and not from the discharge (hot air return). as I have seen one case where the connection was wrong, and the generator ended up filled with oil mist.

 

Dear Einollah Moslehi,

I just came across your question and would like to discuss your problem as we are specialists in handling the vacuum and oil mist problem. We already solved this kind of problem at several GE turbine types like frame 3, 5, 6, 9 and various others.

If you are interested, just drop us an e-mail at [email protected] and your mail will be answered quickly.

Best wishes
Christopher Franke

>We have power generation Gas turbines (Frame 9- Type:
>PG9171E) in our company coupled to Alstom generators. At
>this time we have some technical problems as follows:
>
>Severe oil mist contamination on the Generator rotor and
>stator due to transmission of oil mists produced in the
>generator bearings. Do you have solution for this problem?
>Is it necessary to have modification or changing of oil
>seals?
>
>mail:[email protected]

 

Hi Dear
If you have a problem in oil tank vacuum it will be clear and oil mist or fumes appeared in all bearing never the less bearing Number #2.

Do have any oil leaks or spillages on other bearing?

If not, then it means your problem is due to oil seals at generator which in most causes as per my experience occurred in NDS( none drive side).

Also you have to check gen. fans and fans filters and do good cleaning before restarting.

Best Luck