Questions regarding Air/Oil Separators

I am think of having one of these Air/Oil Separators installed on my R182
(Lycoming O-540) at annual this summer.

I have a couple of questions:

1) Do they actually work and keep the oily mess off the bottom of the plane?
2) I think there are at least two different ones available - which is the
best?
3) Are there any problems with them?

Thanks,

DB

DB, I've been through 4 of these. The original (brand unknown) that came
with my plane (a Navion with wet vacuum pump). Then I tried an Eclipse
separator, which was worthless. Next I tried an M20 turbos dual
installation (one for crankcase breather, the second for the wet pump).
In fact my Navion was the test bed for the M20 wet vacuum separator.
Look at the pictures on their website; that's my firewall. Still not
happy with the results, so I went with an Airwolf, which handles both
the vac pump AND the crankcase breather. Absolutely clean and dry for
over a year now. The plumbing is a bit more complicated, and the unit
itself is a bit larger, but it actually does what it's supposed to. And
does it very, very well.

Rip

Doodybutch wrote:
I am think of having one of these Air/Oil Separators installed on my R182
(Lycoming O-540) at annual this summer.

I have a couple of questions:

1) Do they actually work and keep the oily mess off the bottom of the plane?
2) I think there are at least two different ones available - which is the
best?
3) Are there any problems with them?

Thanks,

DB

Doodybutch wrote:

I am think of having one of these Air/Oil Separators installed on my R182
(Lycoming O-540) at annual this summer.

I have a couple of questions:

1) Do they actually work and keep the oily mess off the bottom of the plane?
2) I think there are at least two different ones available - which is the
best?
3) Are there any problems with them?

My PA 24 250 arrived with a Walker (now Airwolf, I believe) air/oil sep
installed. It's designed to handle both the breather and a wet vacuum
pump, but since I have a dry pump at the moment (to be remedied when the
thing starts to act up) one fitting is plugged off. It works VERY well;
if I have any complaint it's that it's on the largish side and whoever
installed selected a firewall location designed to maximize annoyance
when changing the oil filter.

On Sat, 10 Apr 2004 08:15:25 -0400, "Doodybutch"
wrote:

I am think of having one of these Air/Oil Separators installed on my R182
(Lycoming O-540) at annual this summer.

I have a couple of questions:

1) Do they actually work and keep the oily mess off the bottom of the plane?
2) I think there are at least two different ones available - which is the
best?
3) Are there any problems with them?

Thanks,

DB


The following is an excerpt from Sacramento Skyranch's monthly
newsletter (hopefully not breaking any copyright rules here). Quite an
eye-opener on the whole Air/Oil Separator issue. The Sacramento
Skyranch website is at www.sacskyranch.com and is full of very
interesting info.



Crankcase Distillation of Water by Air Oil Separators

The burning of 40 gallons of fuel during a flight produces 40 gallons
of water. Although most of the water goes out the exhaust as a gas,
some ends up in the engine crankcase as byproducts of combustion. In
cold weather we can sometimes see this crankcase water as droplets on
the oil dipstick or rocker box. Engines, such as the Lycoming
O-235-L2C, often have rust inside the rocker covers where the water
condenses and collects inside the cover. How is water that is
produced as a byproduct of combustion, and finds its way into the
engine crankcase, removed from the engine?

Your engine is a distillery in which we add combustion byproducts,
including water and unburned fuel into a oil bath; agitate and aerate
with the crankshaft and other rotating parts; heat until the more
volatile products, principally water, vaporizes into a gas and flows
thru a pipe called the crankcase breather into the cooler atmosphere.
This is illustrated as such:

[Sorry, I can't paste the picture in here]


Usually we think that we need to raise the temperature of the
distillery to the boiling point of water 212 degrees F. (-2 degrees
per 1,000 feet above sea level) to separate the water from the oil.
However, since the water, oil, and other byproducts are being
thoroughly mixed, the water forms a azetrope (constant boiling
mixture) with some of the other compounds which changes the mixture's
boiling point. We end up with a range of boiling temperatures,
possibly lower and higher.

A contaminate that has a higher boiling temperature than water, when
mixed with water to form a azetrope, lowers the contaminants boiling
temperature so that the distillation of water from our sump also
removes other contaminants from the oil. This is the milky white
mixture you sometimes see on the engine breather, dipstick or other
condensing surface.

Corrosion pitting is the most common reason camshaft lobes and
followers are damaged (2nd might be stuck valves). Making sure your
distillery is functioning properly by removing water from the engine
crankcase is important if you want to prevent corrosion damage to your
engine. Normally, you need not worry; operate the distillery often and
make sure you completely warm it up. Ground running the distillery
just adds water and doesn't produce steam -- you need to fly your
distillery to fully heat it up.

Every distillery has a condenser that turns the distilled vapors back
into liquid form. With engines we prefer that condensation occurs in
the atmosphere or in a vent line that slopes downward. Now lets modify
the distillery and add what is commonly called a "air/oil separator"
to our system. I use the more accurate term "gas/liquid separator"
since our separator cannot tell the difference between air and any
other gas, or oil and any other liquid. If our gas/liquid separator is
cooler than our oil sump, then our gas/liquid separator also becomes a
condenser with a return line back to the engine. Oil, along with any
distilled liquids, are returned to the engine.

Take for example a worst case scenario. You mount our gas/liquid
separator in a cold area of the engine compartment. You attach it to a
large heat sink called the firewall. Everything you have done has
increased your condenser's efficiency at condensing water and other
vapors into a liquid. Now you're engine pumps the condensate back into
the engine along with some engine oil. You couldn't design a better
way of trapping water in your engine.

The warmer our gas/liquid separator, the less efficient our distillery
is at condensing water and pumping it back into the engine.

3) Are there any problems with them?

Thanks,

DB


The following is an excerpt from Sacramento Skyranch's monthly
newsletter (hopefully not breaking any copyright rules here). Quite an
eye-opener on the whole Air/Oil Separator issue. The Sacramento
Skyranch website is at www.sacskyranch.com and is full of very
interesting info.

Victor at Victor Engines in Palo Alto claims he can always tell which
engines have had air oil separators. More corrosion.

What one needs for the next level is a decanter at the bottom of
the Walker type-- oil goes back into engine, water gets dumped.

On Twin Bonanzas, Dave Monti tells me that the oil separator
outputs got dumped into the exhaust augmentor. Perfect solution...
the trash gets burned, not put back in the engine.

Bill Hale

Crankcase Distillation of Water by Air Oil Separators

On Mon, 12 Apr 2004 17:32:26 GMT, Chris
wrote:

On Sat, 10 Apr 2004 08:15:25 -0400, "Doodybutch"
wrote:

I am think of having one of these Air/Oil Separators installed on my R182
(Lycoming O-540) at annual this summer.

I have a couple of questions:

1) Do they actually work and keep the oily mess off the bottom of the plane?
2) I think there are at least two different ones available - which is the
best?
3) Are there any problems with them?

Thanks,

DB


The following is an excerpt from Sacramento Skyranch's monthly
newsletter (hopefully not breaking any copyright rules here). Quite an
eye-opener on the whole Air/Oil Separator issue. The Sacramento
Skyranch website is at www.sacskyranch.com and is full of very
interesting info.

I strongly disagree with them based on experience although with a
bigger engine.

I have the Deshannon air/oil seperator on my IO470N. I also use a
preheater and once the temperature is cold enough to use it it stays
on 24 X 7 except for when the plane is flying. The oil companies used
to say not to do that. Now they say it's a good idea. course the
engine compartment is also completely wrapped with two layers of the
new space age blankets.

The oil stays clear until near 20 hours. The cylinders look like they
were polished on the insides.

That and the ABS mechanic spoke highly of them.

OTOH mine is mounted on the rear of the engine and that sucker gets
hot.

Like many things some swear by them and some swear at them.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Air Oil Separators like the Walker & BDS...

So I've thought that an interesting experiment would
be to arrange a can to catch the liquid coming out
of the separator... then go for a couple of flights
and see what was in the can.

On the Walker, one could modify it so the oil return drain
stuck up into the bottom of the unit a bit; then add
a separate drain at the very bottom, which would be for
manually draining water. That might decant the oil.

But the total amounts might overwhelm such a system.
I wonder how much actually goes thru there on an average
flight?

It also seems to me that the wet vacuum pump should exhaust
directly into the crankcase. That would provide a fresh
air douche. Somewhere near the front would be good.

As the famous chemist Cliff Hach mentioned awhile ago...
"Hell, cars have had positive crankcase ventilation since
1932!"

The water on the dipstick isn't a good thing. Cliff once
measured the PH and found that it was TWO!

Bill Hale