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Engine Dehydrator?


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I built my own. Almost certainly overkill with this size compressor. I run it on a timer, 5 minutes per day, and after every flight for about 5 to 10 minutes. I have to regenerate my desiccant every 4 months or so. (Dallas humidity level.)

Is it necessary? Is it helpful? But it makes me feel better.

Dryer 1.JPG

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37 minutes ago, Mooney_Mike said:

That appears to be an open loop system you have built. Thoughts on a closed loop system? Seems like the closed loop would have the advantage of not taking in ambient air all the time.

I agree in theory. (Assuming the only value of a closed loop is to alleviate the necessity of continually drying the ambient air.)

If I were having to regenerate the desiccant frequently, I might go to the effort to design a way to suck the air back out of the engine and run it through the compressor again. But having to cook the beads with about the frequency of oil changes, doesn't seem worth it to me.

Incidentally, if I can offer any other information about my system, feel free to PM me.

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There were plans available for a system using desiccant in a Tupperware container, with a fish pump to move air and a lightbulb to heat and dry the desiccant at some timed interval.  Can't recall where I saw it, but it theoretically gave the desiccant a long life. Will try to find the instructions.

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I'm glad someone made a new thread on these. I ordered everything from Amazon. Basically a fish tank pump (that supposedly works fine with air), brass nipple fittings, gallon of desiccant, and some snap-lock Tupperware style containers. I also purchased a $10 digital hygrometer that will sit inside one of the Tupperware containers. Not sure how I'll route the vinyl tubing - I'm thinking dry air to oil fill tube and the two suction tubes to the exhaust pipe and oil breather tube. I'll upload a photo of the supplies tomorrow.


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The idea of a closed loop system is wonderful.

To do this you would have to take into account every location air can enter the engine...

1) intake system

2) four or six exhaust valves

3) engine case vent

4) exhaust pipes are not well sealed at the expansion joints.

 

An interesting side benefit of Don's system. Compressing the air first makes the moisture fall out of solution. Then it expands and it becomes pretty low RH before it goes to the drying system... don't forget to drain the compressor's tank.

Don is one part mechanical engineer, another part process engineer, and a third part Legal guy.... :)

 

keep in mind the valves are not all open at the same time.  This leads to RH challenges in some of the cylinders.  There are special moisture absorbing plugs that are used for this that go in the spark plug holes.

Also keep in mind RH is relative, warming the air lowers the RH.

Oxidation is a chemical reaction.  Chemical reactions are temperature dependent. Lowering the temperature by 10°C cuts the rate in half (generally) 

Compress the air, Cool the air, expand the air, Dry the air, then use...  then drain the compressor...

Put extra thought into how you get the dry air to flow into the engine block at one end and out the other end...  think about all the places the air doesn't go.  Don't push air up the exhaust system, this can put some dirty rusty exhaust system bits into the cylinders if you lose control of the air system...

 

Ordinary PP ideas. Not a mechanic...

Best regards,

-a-

 

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42 minutes ago, Mooney_Mike said:

http://www.barkeraircraft.com/Engine-dryer-kit.html

I just ordered the above kit. I like how it is "fully automatic" and a closed loop system.

 

 

I have one and dont use it, as the moisture tends to condensate on the glass pickle jar vs vent to the atmosphere, and recontaminates the desiccant. Instead, I use a modified version of the original barkeraircraft design where I introduce a jar of kitty litter into the system on the intake side and the return air is from the crankcase overflow. I dont worry about sealing intakes etc, as I am only concerned with the crankcase humidity. I let it run 100% of the time and change desiccant about every 3 weeks during the humid July Aug months. Once you dry the air in the crankcase, it stays dry. Works great. The Kitty litter takes the oil vapor out and keeps it from contaminating the desiccant.

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I made one and used a bunch last year, but finally realized that I fly too often for it ever to be an issue.

Someone did a test by frying roller bearings in different aviation oils and letting them sit for periods of time in high humidity controlled environment.   The particular oil I use gave 22 days of protection in high humidity.  I fly every week.  If I know I'm going away for a period of time during the spring or summer, I'll hook it up for peace of mind.

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4 hours ago, Browncbr1 said:

I made one and used a bunch last year, but finally realized that I fly too often for it ever to be an issue.

Someone did a test by frying roller bearings in different aviation oils and letting them sit for periods of time in high humidity controlled environment.   The particular oil I use gave 22 days of protection in high humidity.  I fly every week.  If I know I'm going away for a period of time during the spring or summer, I'll hook it up for peace of mind.

Depending on where you live, in the morning water condenses on the case and cam.  It won't be 22 days of protection in that case. 

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I suggest you look closely at the chemistry of the desiccants you are using and their corrosive properties.  Sometimes Calcium or Magnesium Chlorides are used and the last thing I would want to do is to blow dusts of these materials inside my engine. They are corrosive to carbon steel.  Silica gels are less of an issue. 

Edited by Gary0747
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A dehumidifier is basically an air conditioner which rewarms the air, so for an uninsulated hangar you would need 5-10 tons of air-conditioning to start with.  basically it's not really feasible.

Edited by jetdriven
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