Lube oil leakage in to the ge frame 9e gas turbine generator.

J

Thread Starter

jonas

If the gas turbine is running, it leaks lube oil into the generator. All effort to locate the exact leaking point proved futile. If the gas turbine is shutdown and the auxiliary lube oil is running ,you would not find any leakage of lube oil into the generator. The leakage is between the bearing number 4&5.
 
When did this problem start?

Is the generator air-cooled or hydrogen-cooled?

When the gas turbine is running, the generator bearing end-shield granular side L.O. deflectors (item 3425 on the Generator Package Wiring drawing, Sh. 43) must be compromised by the electromagnetic radiation coming from the seismic vibration pick-ups. This will cause L.O. drips to seek the shortest path from Bearing #5 to Bearing #4, because there are usually two seismic (velocity) vibration pick-ups on the #4 bearing and only one seismic pick-up on the #5 bearing. (Sometimes adding a second seismic pick-up to the #5 bearing will also alleviate, but not completely eliminate, the problem.)

Or, the generator shaft grounding brush needs burnishing to improve the coupling with the L.O. sub-atomic particles to prevent them from being centrifugally released and attracted to the generator rotor windings but repelled by the polyvinyl chloride Teflon coating, causing them to fall to the belly of the generator casing only when the turbine is running.

If the generator is air-cooled, the generator bearing vapor extractor might be purporting instead of extracting. Check the plural duopoly gauge of the AVR to see if the butterfly valve of the generator bearing vapor extractor needs feeding. If so, change the rated frequency field of the I/O Configurator (it's presumed the turbine has a Mark V turbine control system) from 50 Hz to 60Hz, save and exit, download and re-boot, START the unit, synchronize it, and then change the value back to 50 Hz, save and exit, download and re-boot all three processors at the same time. The butterfly valve will then return to it's proper position after the unit trips from load and is coasting down to zero speed.

In any case, to eliminate the turbine control system as a cause of the problem change the 125 VDC supply to the turbine control panel to 415 VAC; single-phase will be fine. (A convenient way to do this is to jumper the battery charger supply to the battery charger outlet; just be sure to open the battery charger's DC output breaker and apply a lockout tag and lock before doing so to prevent anyone from accidentally closing it with the jumper in place.)

That will make everyone forget all about the generator L.O. problem until the smoke clears from the control panel. In the meantime, the Mechanical Department can get their wrenches ready to start disassembling the generator end-shields to find the reason for the leaking, because the leak probably started after a maintenance outage or a high vibration event or high stator temperature event.

Hope this helps!
 
J
> When did this problem start? <

The problem started november 2009.

> Is the generator air-cooled or hydrogen-cooled? <

Is air-cooled. We use mark vi not mark v.
 
You didn't get the point at all. You didn't provide very much in the way of useful information for us to be able to provide much in the way of useful help.

And, you've continued the pattern. So, we're going to play '20 Questions'.

You said you've checked everything, but what did you check and how did you check and what were the results? Did you remove the end-shield(s) and look to see where the oil is coming from?

We aren't at your site and so can't know the exact configuration of the generator at your site. (GE changes vendors depending on the price they can negotiate, so there is more than one type of generator in use with Frame 9E turbines.) Are the generator bearings in-board of the end-shields? Is one side of the generator bearing in-board of the end-shield and the the other side of the generator bearing out-board of the generator bearing?

Does generator bearing L.O. supply and/or L.O. drain piping pass through the generator casing?

You say the problem started in November, 2009. What happened in November 2009 prior to when the problem started? Was there a maintenance outage? Was there a high vibration event on the load coupling or generator bearings? Was there any maintenance done on the generator, generator bearings, a generator inspection that required removal and replacement of the end-shields, etc.?

You say the generator is air-cooled. Is there a generator bearing evacuator pump? (It's usually an AC motor-driven "blower" whose purpose is to maintain a slight vacuum on the generator bearings so that oil will not flow out of the air seals.) Sometimes the fans on the ends of the generator rotor actually create a negative pressure on the generator bearings (if the generator bearings are in-board of the end-shield, or one side of the generator bearing is in-board of the pedestal bearing). So the bearing evacuator pumps were added to draw a very slight vacuum on the generator bearings to prevent the negative pressure (vacuum) of the generator rotor fan from drawing oil out of the bearing.

There was usually a filter in the generator bearing evacuator pump that requires periodic replacement. And there was also a butterfly valve that had to be manually adjusted to maintain the desired negative pressure (vacuum, usually in mmH2O) on the generator bearings.

So, if there is a generator bearing evacuator pump, have you checked to see that it's working properly and the butterfly valve is adjusted properly?

If there's no generator bearing evacuator pump there is usually some kind of L.O. vent line to the turbine L.O. tank and L.O. demister. Is this line blocked? Or was it blinded during a maintenance outage and the blind not removed prior to re-start?

Many, many years ago some welds in L.O. supply piping were found to be porous and were weeping L.O. into the generator casings of some air-cooled generators.

If any L.O. piping passes through the generator casing, you may have to disassemble the piping, install flanges and taps and use air pressure to check for leaks.

But, there's likely not a controls problem that is causing L.O. to appear in the generator casing drain.
 
R

RichardBurgers

We have had a similar oil problem on our generator (ELIN)(GE Fr9E)We have opened the bearings on both side but at the end we did not solved the problem.

What we knew was that the seal air to the labyrinths of the bearings was under pressure. This because we measured it by mounting a pressure indicator on the manhole. As you probably know you have to have overpressure (like the GT bearing labyrinth seals) to prefend <i>[mods note: prevent?]</i> oil to come into the generator.

There are breather caps mounted on four positions of our generator, these breather caps are air filters which provide air to the generator. By removing one air filter the under pressure switched to overpressure due to the blocked filter.

At that time the sealing air became positief <i>[mods note: positive?]</i> and the oil leakages stopped after a few hours. So I suggest look if you have air filters and change them, we did it with a running machine.
 
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