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Generator Bearing Leaking , GE 9E
Oil and vapor leakage from generator bearing #5 after installing orifice at the discharge pipe of the mist eliminator

We have a problem in lube oil sys which oil escaped and showring from the mist eliminator discharge chimney (vaccum value 152 mmh2o at baseloade). We changed the filters and flushed the piping and checked the loop seal however the problem still existing.

After that GE Advisor recommended installing orifice at the mist eliminator discharge pipe. After installing this orifice the vacuum value decreased to 85 mmh2o but after few days we found vapor and oil showering at bearing #5.

Is this because of installing the orifice?

The generator is air cooled generator.

Thanks.

MOmar91,

There sure are a lot of oil problems at your site....

Some units have two L.O. Mist Eliminators--one for the turbine (and accessory and load compartment and #2 bearing), and one for the generator. How is your unit configured?

A lot of times there is visible plume exiting the L.O. Mist Eliminator when the pressure is properly set while the unit is running at Base Load (sometimes it more visible than others). And, often, there is little or no plume when the unit is at Base Load, but it's the vapours (plume) from Part Load operation that cause the oil to condense and make the big mess. (This is true of both the "main" L.O. Mist Eliminator AND the Generator L.O. Mist Eliminator.)

Most L.O. Mist Eliminators only have a variable adjustment which is to be set to a specific vacuum when the unit is at Base Load--but when the unit is a Part Load the vacuum is MUCH higher and that's what causes the plume (vapours). What's really needed is a variable orifice that automatically controls the vacuum to a constant value regardless of load. That can be done with a self-contained controller and orifice; it doesn't have to be done through the Mark*.

If the problem worse after installing the orifice recommended by GE, it would seem the orifice is the source of the problem.

How old is this unit?

What Mark* version does the unit have?

Most of the time the problem of oil vapours at the discharge of the L.O. Mist Eliminator are the result of poor maintenance, or "excessive" vacuum at Part Load--and if the unit is run a lot at Part Load as opposed to Base Load, that could be the issue (Part Load Operation). You might need to find a positioner and self-contained controller for the L.O. Mist Eliminator to control the vacuum to help eliminate the oil vapour condensation.

If it's the turbine L.O. Mist Eliminator that has the problem, I believe it gets some "pressure" from the #2 Bearing vent "fire hydrant" and I've seen those improperly installed and cause problems, too. So, if the problem started after a maintenance outage where the #2 Brg. vent "fire hydrant" was removed and re-installed, you might want to consider checking that for proper installation.

>There sure are a lot of oil problems at your site....

* yes we have problems in another units like lube oil header pressure low (1 bar) and lube oil sys pressure low 4.8 bar.

>Some units have two L.O. Mist Eliminators--one for the
>turbine (and accessory and load compartment and #2 bearing),
>and one for the generator. How is your unit configured?

*we have 8 gas turbines, 4 with only one blower and 4 with two blowers but intake from the same point in the lub oil tank which one running and the second is standby but this unit have one.

>A lot of times there is visible plume exiting the L.O. Mist
>Eliminator when the pressure is properly set while the unit
>is running at Base Load (sometimes it more visible than
>others). And, often, there is little or no plume when the
>--- snipped by moderator ---
>regardless of load. That can be done with a self-contained
>controller and orifice; it doesn't have to be done through
>the Mark*.

*yes adjustable check calve with spring

>How old is this unit?

*running 8000 hrs only

>What Mark* version does the unit have?

*mark vi e

>If it's the turbine L.O. Mist Eliminator that has the
>problem, I believe it gets some "pressure" from the #2
>Bearing vent "fire hydrant" and I've seen those improperly
>installed and cause problems, too. So, if the problem
>started after a maintenance outage where the #2 Brg. vent
>"fire hydrant" was removed and re-installed, you might want
>to consider checking that for proper installation.

*No we didn't remove the fire hydrant.

Today we will remove the orifice and i will check cooling and sealing orifices maybe find its out of the size.

Thanks