Load Gear Oil Leakage GE 6B Gas Turbine


Thread Starter


when we are going to base load (45MW); on load gear (FLENDER) oil leak is starting.

somehow at 40MW everything is OK. but after 40 MW when we are increasing the power the leak is starting from both sides of Load gear. Turbine side and Gen side. according to readings everything seems OK. Oil temperature, bearing temperatures, vibrations, vacuums etc.

we are just trying to find out what is the reason for this leak. on the other hand we have 6 turbines. all of them are same and just one of them has that problem.

If it is a mechanical damage at seals inside the load gear box, why that leak start after 40MW.

can any one help?
Dear EserBP,

I am not very familiar with the 6B units but will offer these suggestions and questions.

On the units I am familiar with there is typically some sort of mist eliminator system, that draws a slightly negative pressure on the oil system, does your 6B have this type of system?

Typically there is a manually operated butterfly valve to control the negative pressure being drawn on the system, does yours have this?

Typically this valve is set to some sort of position when the unit is at base or max load. This is because as the load rises the pressure inside the bearing cavities rises due to bearing pressurization from some compressor extraction. This is usually around 2-5" H20. Usually the vacuum will be higher at lower loads since bearing pressurization pressure is less. I would suspect that your oil tank vacuum, or vacuum at the gearbox is less than needed at the higher loads.

I would verify proper vacuum at baseload in the lube oil reservoir and at the gearbox. It is possible that a seal or drain is damaged, but I would be checking these basics first. Please write back with your findings, the more information the better.

at first i would like to thank you for your reply.

it is true that we have mist eliminator system with negative pressure for oil system. And on mist eliminator we have butterfly valve to control negative pressure.

when we had low load as you mentioned we have higher vacuum, but on the other hand when we are increasing the power however vacuum pressure is decreasing, we have enough pressure. we are not getting less than 2"H20 which is normal value according to Op.Manuel.

besides that we increase the vacuum, till 4-5"H2O by butterfly valve and using the seconder mist eliminator pump, still we have leak but less than before.

and also we checked all drain lines, vacuum lines, filters, oil pumps, mist eliminator pumps, flows, temperatures, vibrations etc..

as i mentioned before we have six same type of turbines and just last one giving that problem to us. we compare all readings with other units, and everything looking normal but the leak.

that's why i thought it can be mechanical problem, but from both side of the shafts (Low speed and high speed) of load gear we have leaks; so it makes me confused. how it can be possible the seals are damaged from both sides.

and i want to repeat my question again, if we have mechanical problem why it is starting just before the maximum load?

The fact that you can decrease the severity of the oil leak by increasing the vacuum on the gear box indicates the gear box casing isn't experiencing the vacuum you think it might be. This presumes you are not measuring the vacuum <b>at</b> the gear box.

Have you contacted the gear box manufacturer for assistance?

I have seen cases where slight differences in machining or installation have caused similar problems in similar multi-unit installations.

You also didn't say if the unit experiencing the leak had ever had any vibration issues.
Just had the same problem on four Frame 6 with new Flender horizontal box. Firstly we increased the vacuum but this did not totally correct the problem. We have a fully enclosed #2 bearing coupling guard and we felt that it was causing a slight "air whirl" problem and adding to the gearbox pressure. We opened the bottom of the guard and added some perforated material and this did the trick. We are now getting some proper guards manufactured.

These were new machines, so this was a design problem. If your machines were OK at high load before and this has suddenly just happened, then this won't be the cause. If you have always had this problem, then it may be worth trying.
Dear CSA,

thank you for reply;

because of that fact we directly measure vacuum from the gear box by manometer and it was almost same value with the Mark-VI readings.

we are in commissioning and starting steps and that's why there were no vibration problem before and also we do not have now.

we contact with the manufacturer and they suggest to send someone for check. but because of work permits and other think it will take time for them to come here. before they will come we want to do whatever we can do.

today we are going to re-test. and we will see.
we change the flow by VPR press. regulating valve)
Mr. Johnston;

is has not suddenly happened, from the beginning we have this problem.

we also think about the "air whirl" can cause. So we check the deflectors but everything is looking normal. without manufacturer approval we can not open the casing to see is there any problem on labyrinth seals because of the warranty issues.

the question in my mind is why it is starting just before the base load not before. and leak is starting from both sides of Load Gear.low speed shaft and high speed shaft.

oils are spraying between the shaft and casing. when we are comparing this unit with others everything is looking same, but there should be something different which we could not find out yet.
Bob Johnston,

Can you post pictures of the modification to a hosting site and then post the link to the pictures, please?

Dear Sir,

How did the re-test went on?

> today we are going to re-test. and we will see.
> we change the flow by VPR press.
Hey Bob,

Similar situation here as well on a Fr6, Flender GB (vertically stacked), leaking GB on generator end. The gearbox is leaking lube oil on the low speed shaft. The existing generator (BHEL) was replaced with a Brush Generator and the commissioning checks are in process, at FSNL is when it was discovered that the oil is leaking on that section.

1. The coupling guard that you added the perforated material, was the coupling guard exposed on the bottom or was it completely enclosed? How much perforated material did you add? Our guard is fully enclosed with the exception of 5:30pmg to 6:30pm on the bottom and two small patches (4inches x 8inches) of perforated material at the top. Do you think more perforated material is required or just a small amount is needed to break the air whirl?

2. The butterfly valve that is discussed, is this standard? I was assigned several Fr6 units in California and none of them had a butterfly valve. I checked the P&ID to be sure and it sure isn&#8217;t. Where would it be installed?