Backcountry Pilot

[a64pilot offline]

Like most subjects, there seems to be a lot of debate about the temp needed to expel water from engine oil. I'm wondering if there's an easy test to determine how much water your engine oil is holding?

Only one I know of is an oil analysis, and I guess that does not meet the "easy" requirement

[qmdv offline]

Water boils at 212 deg at sea level. Not sure what it boils at at 8000 ft. Not sure what top of green is. Just a guess at about 280 to 300.

Tim

[mtv offline]

Water also boils at a lower temperature when under pressure, and there is some small amount of positive pressure inside that engine case when its running.

Both the engine manufacturers recommend getting your oil temp up to AT LEAST 180 degrees F for 20 minutes to EVAPORATE as much water as possible. This recognizes the pressure applied within the engine, and the fact that water doesn't have to boil to evaporate.

MTV

[qmdv offline]

Water also boils at a lower temperature when under pressure,
MTV

Negative on that. You get a higher temp with no boil in a pressure cooker. You get a lower boiling temp at higher alltitude. Primary water in a nuke plant is way hot and it does not turn to steam at all. Well that is the way it was on the USS Queenfish.

Tim

[soaringhiggy offline]

That is correct, water boils cooler under less pressure.

While at sea level the boiling point of water is 212° Fahrenheit, for ever 500-foot increase in elevation, the boiling point drops one degree. Thus, at a city 5000 feet above sea level, water boils at 202°F. Credit Matt Rosenberg.

Also ice can go directly to vapor with out going through liquid, depending on the triple point with temperature and pressure.

[mtv offline]

Oops, one too many merlots tonight.

Point is, there is water in gaseous form in our atmosphere in large quantities. It doesn't have to BOIL to change to a gaseous form, but some heat helps.

As I noted, the engine manufacturers recommend a minimum of 180 degrees oil temp for at least 20 minutes per flight if possible.

This does not BOIL the water off from the oil, but it heats it sufficiently that much of it will turn to vapor, and escape via the crankcase vent.

THAT is fact, regardless of what temperature water boils at.

MTV

[qmdv offline]

Know a guy that every two weeks he would taxi his plane away from the hangers and run his engine for ten minuts. Hardly ever flew the dard thing. I told him he was doing great harm to the engine. Better to just fill the crankcase to the top with drain oil out of his John Deere than do that.

And 180 is not really very hot for oil but that is plenty to get rid of the water vapor and condensation in the crank case.

John Frank at Cessna Pilots Association says that you should fly your plane a minimum of once every two weeks with operating temps up. Not just a few touch and go's

MTV says 20 minuts and that does ring a bell.

The to much Primo at the Pearl City Tavern or the Dolphin Club never worked as an excuse for me back in 68. I am sure that MTV never hung arround those places.

Tim

[mtv offline]

Nevair!!!!

Shipwreck Kellys.....Bouncer was a friend, and ran the sonar gang on the Bonefish.

MTV

[Zzz]

Point is, there is water in gaseous form in our atmosphere in large quantities. It doesn't have to BOIL to change to a gaseous form, but some heat helps.

As I noted, the engine manufacturers recommend a minimum of 180 degrees oil temp for at least 20 minutes per flight if possible.

This does not BOIL the water off from the oil, but it heats it sufficiently that much of it will turn to vapor, and escape via the crankcase vent.

This is correct. Here is a link to a specific post that contains my entire nickel ($.05)