We are currently implementing a combined cycle power plant project. We have purchased 4x LM6000 PC Sprint gas turbines from GE Power Systems and 2x26 MW condensing steam turbines from GE Thermodyn/France.

We have witnessed factory running test for steam turbines at GE Thermodn France. Each steam turbine is 26 MW, condensing, impulse type, 4200 rpm. The gearbox and generators is at steam inlet side of the turbine. During the test, we noticed that there is lube oil leaking from labyrinth seal of front bearing towards the coupling which connects turbine to gearbox. We objected and requested to correct the situation but GE Thermodyn said that the oil leakage is normal and therefore they have put a totally closed coupling guard and a 11/2" piping underneath to return the oil collected at coupling guard to the oil tank.

We would like to take your comments/remarks regarding this situation. Did you meet such a conditions?

Awaiting for your kind reply,

Best Regards,

Akif Ozmen
HABAS A.S.

e-mail : akif.ozmen@habas.com.tr and/or cryon@superonline.com
Tel : +90 216 4525600 ext:485
Fax : +90 216 4522570
Fuat Pasa Sok. No:26
Soganlik Kartal
81570 Istanbul
TURKEY

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 message has been edited. Last edited by: 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.

I think i will use this discussion opportunity to share details on two products that we import and market in India. Both find application in sealing of turbine joints.

Hylomar M, the first product is a unique nonhardening sealant originally developed by Rolls Roycefor sealing of Aircraft engines. Today the product is used extensively in the power gen industry for sealing metal-to-metal joints at high temperatures, in the presence of oils.

The product is a permanently plastic, very adhesive sealing compound based on polyurethane. Due to its excellent thermal, mechanical and chemical resistance, the sealing compound is especially suited for highly stressed joints. The material can handle temperatures upto 250 deg c and upto + 300 deg c for short time. Hylomar M is resistant against mineral oils, synthetic oils, fuels, additives, gases, water, antifreeze, etc.

I will try and add the picture of one of the key application areas - the pedestal bearing parting planes. Other areas include oil joints in turbines, engines, high temperature gear box flanges, as a gasket dressing product on pre-formed gaskets for better sealing in the presence of oils and fuels, diesel engines cylinder head gasket, inlet manifolds, oil sumps, etc. You can see more details on www.projectsalescorp.com

The 2nd product is Stag B Compound, referred to as Stag Jointing Paste Type 'B' a product of Kommerling, UK. The product is used for sealing applications where the highest temperature resistance is required. It has been used for sealing of turbine flanges for over two decades now.

Reddish brown in color, this thick consistency paste is resistant to a wide variety of chemicals, apart from the highest temperatures.

Again, our website contains more info or you could also log onto www.stagb.blogspot.com

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.