Turbine Bearing Vibration and Oil Leak


We had vibration on bearing 2. The mist eliminator filter was choked so there was no sufficient vacuum for a period of time before the vibration happened. The clean side of the Air inlet filters was dirty (but not that much), also bore scope showed that the turbine buckets are dusty. Now @ the outage we have inspected the bearing 2 and found Oil leak in the bearing 2 area. Furthermore, we have opened the oil deflector and the seal ring and there was high amount of carbon in these rings. the holes on the bearing 2 casing that allow the air from BN to enter and cool was chocked with carbon.

According to GE (based on what I have understood from them). the reason for this problem is as follows

First the BN Fan takes filtered air from the inlet air and deliver that air to cool bearing 2 area. some of that air will enter through the holes in the bearing casing and then into the holes in the seal ring to cool that area. After that this air will go to the lube oil tank by the help of the vacuum created by the mist eliminator. So if you don't have clean air from the BN + no enough vacuum in the oil tank this case (carbon) would happen. this carbon if reached a certain amount, then the vibration will show up.

What we have done now is:

1- changed the filter in the mist eliminator
2- changed the inlet air filters
3- changed the oil deflector and seal ring with a new one

But still we have not run the unit.

Please can you explain this case for me in details (like how BN enters the holes and go to the tank, also why there are holes between the oil deflector and seal ring). and I don't get how the holes which air gets through got chocked. please elaborate on the issue

see the picture for the oil deflector, seal ring and the carbon


Thank you

This forum is primarily for controls-related issues. Controls often includes field devices and instruments (solenoids; valves; fans; etc.), but this is pretty far off.
Thank you CSA. It seems i got a little bit excited. Because based on the replies of experts on this forum, they don't only know how a parameter is kept under control, but they tell you the importance of controlling it and what happens when it goes out of control. So you experts have a knowledge that is beyond the control. Anyway. Maybe you have some information on the BN and its important and why it should always supply air to the seal ring.

Thank you again


> We had vibration on bearing 2?

Is it related to Brg coking?
Why it happens in frame 7FA gas turbine?

Is it related vacuum in lube oil tank?


Asish Thomas

>> We had vibration on bearing 2?
>Is it related to Brg coking?
>Why it happens in frame 7FA gas turbine?
>Is it related vacuum in lube oil tank?

Do you face bearing coking in frame 7FA? We are experiencing the same and are planning to go for a replacement of the seal as we are losing a lot of oil (approximately 2 barrels a day) through the seals. several theories have been put forward but I would like to know more from those who have been facing the same problem.