Steam turbine oil leakage from front bearing housing

I have seen oil leakage from labrynth seals reduced by using an air scavenging system at the oil tank. An air oil seperator (fan + oil mist filter) is used to remove air from the tank which creates a negative pressure in the tank and return lines. Most return line in a large circulating system are not flooded with oil and have an air space above the oil level. Unless you have some low spots on your return piping creating a trap the negative air pressure is on the whole system drawing air into the labrynth seal instead of a positive pressure on the oil side pushing oil out. This is often used to prevent oil migration from teh bearing housings into the generator thru labrynth seals.

We to have the same negative pressure system as the guy from the USA.We once found a large oil leak from the shaft bearing labrinth seals , the cause was found to be a closed valve to the oil mist eliminator system causing a positve pressure in the bearings

What a great site this is !!! We are currently trying to put a similiar turbine online and are experiencing the exact same issue with oil leakage. We will modify this system to induce negative pressure.
My only question regarding negative air pressure through a labrynth seal would be:
Have you seen a increase in particulate contamination? When this system is taken off line the labrynth would not be sealed, correct?

Thanks again,

Jim

This is an interesting subject as we have been trialling breather vent contamination filters on rail drives for several years,
if we cause the labrynth seal to leak in these drives we loose the drive to the repair shop and so far with our trials we have not had any suggestion of a leak so far no matter how restrictive we make the breather vent filter. This indicates to us the dynamic "pressures" generated in labrynth seals is fairly "robust" with no leaks.
If oil gets in these labrynth seals the highly contaminated environment rapidly cuts the seal out causing the drive to be pulled.

With the situation "akif" mentions the concerns become how the labrynth seal handles oil inside the seal because we see this cause failures in more contaminated environments and the other area how much contamination is being returned to the reservoir via the seals return oil line.

Maybe this seal is designed to leak???
but I have never encountered this situation before the with the only time we note seal leaks being gearbox over full and oil getting in the seal's labrynth when the drive is stationary or the seal is damaged.

We are interested in any info on Labrynth Seals as when we attempted to restrict the OEM 50 µm Breather Filter !!! the OEM Engineers objected strongly saying the seals would leak, no wrong ,so far zero
making Akif's seal leakage seem very abnormal,

This reply is not going to solve this message's difficulty so hopefully other experiences in this field may "think tank" some info to assist here from others and we may also get additional info assisting our research

Regards Rob S

Jim,
The designe I have seen still have a vent breather on top of the tank to allow ait to be pulled in under the breather is an orifice plate to give some restriction. I'm sure there is a target negative pressure you are seeking which I would guess (not an engineer) to be only a few inches of water. This should not draw enough air through the labrynth to adversly effect you particle counts if you are using an oil conditioning module such as a vacuum dehydrator or centrifuge to continuously clean your oil.

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Normally the bearing and the labrinth should be made apart. No oil of the bearing can be enter the seal. I do not know whether oil is supplied to the seal itself for sealing like steam that is given to labrinth seals. If so this type of observation is possible. But I feel that this is abnormal.

Having worked with many of the big OEM`s they all say Oil Leakage is normal building Coupling Guards with drains to link up with the main reservoir etc... We have sealed the shafts with Laberinth no contact seals, that work for Sulzer, Weir, Renk, Allens, David Brown etc

If you need a oermanent fix that does not leak oil or wear out! Email me.