APU Oil Consumption High


Thread Starter


After preventive maintenance for our Air proccessing unit which oil filter, oil separator cartridge, air filter, and coalescence filter were changed and increase oil level, we observed that the oil escaped from air dryer silencer while purging.

We checked all connections (not clogged) and oil separator position but the oil consumption still high .

Why the oil escaped from the dryer silencer?

All of the Air Processing Units (sometimes called Air Processing "Skids") I have worked on used for cooling and drying the air which is used for the self-cleaning turbine air inlet filter system as the air is drawn from the axial compressor discharge (often, it also had a pressure regulator). The APU only consisted of a finned tube heat exchanger, a dryer with desiccant (usually two cylinders with a small, self-contained control system for switching between the two and sometimes an electric heater to help remove moisture from the desiccant), and \a float-type water drain. Some APUs had electric fans to move air over the finned tube heat exchanger.

I'm not familiar with the APU you are describing; it seems to have some kind of electric motor-driven compressor which uses oil for lubrication. If possible, can you please post the P&ID for the APU to a web-sharing or file-sharing site for review and then post a link to the location? Does the APU dry air from the axial compressor discharge when the turbine is running, and switch to the electric motor-driven compressor when the turbine is not running

If there's a oil-filled compressor it would sound as if there is a leak into the air stream--most likely the compressor piston ring(s). But that's guess based on the information provided. And, further, if there is a desiccant dryer if the oil gets into the desiccant it will ruin the desiccant.

It might also be possible that too much oil was added to the compressor.

But without understanding the APU configuration and operation, that's about all that can be said based on the information provided.
Dear CSA,

Our APU like any one installed with GT GE frame 9E (Ervor company). It consist of axial compressor, air/oil separator, heat exchanger cooler, filters, regulators, and air dryer. The compressor discharge is air and oil (use for comp. Lubricant) which separated by air/oil separator the oil back to oil reservoir, and the air pass through the cooler to the air dryer. It must be air only without any oil.

In our case after made preventive maintenance some of oil not separated, and went to dryer with the air which escaped from silencer during shifting between to cylinder. Yes in this case the oil mixed with the desiccant.

I will try upload the p&id.

Thanks for the link. My anti-virus software won't let me access the location because it has detected the Trojan virus.... (Which is one reason why control.com won't let anyone post files to the site.)

And, just for future information: Every GE-design Frame 9E heavy duty gas turbine <b><i>IS NOT</b></i> like every other GE-design Frame 9E heavy duty gas turbine. The axial compressor and turbine are usually very similar, but the package and auxiliaries can be <b><i>VERY</b></i> different.

And if GE-Belfort was involved in any way, then standardization is lost and gone forever.

I was able to look at the P&ID you made available; thanks.

There IS a dual source for the compressed air for the GT and auxiliaries--axial compressor discharge/extraction, and an electric motor-driven compressor (I think the symbol on the P&ID is for a centrifugal compressor, and I wonder if the compressor is actually a (multi-)piston reciprocating compressor--but that's not the point.

It would seem the only place where oil can get into the air stream is from the electric motor-driven compressor (CMP 301). UNLESS, there is oil coming from the GT axial compressor... which would NOT be good; not good at all.

My first response still stands even after looking at the P&ID: The source of the oil is the CMP 301. OR, the axial compressor, which would mean the turbine #1 bearing is leaking. That ought to be pretty easy to check--there's probably a manual drain valve somewhere in the extraction piping before the CLR 201 cooler, and if you open that drain valve and oil comes out of it, then it most likely is coming from the GT axial compressor.

Please write back to let us know what you find. If oil is in the desiccant, the desiccant is going to need to be replaced.
Dear CSA,

You are right only the oil comes from the aux. Compressor (screw compressor). When the aux compressor stopped and the compressed air from GT, no oil escaped from the dryer. But when the GT load reduced to 60 MW and the self cleaning start the air pressure dropped in the tank so the aux compressor running and find oil escaped from the dryer silencer while shifting between two cylinders then we checked oil level, it was decreased.

The dryer desiccant became saturated with oil so we will replace it but after solving the problem.