Engine Dehumidifiers/De-Hydrators

[M20F-1968]

There are a few engine dehydrators made that drop relative humidity by using dessicant crystals, in either an open loop or closed loop system.  There are also plans to make a system.

Who has experience with these, are they worth the effort (I am in a hangar which I keep at 48 degrees in winter and ambient temp and humidity in summer in MA).  Any info would be helpful.  

This link has a number of references:  https://www.pilotsofamerica.com/community/threads/engine-dehydrators.55078/

John Breda

[Bryan]

I just bought an “Engine Saver” from spruce but only been hooked up a couple of days. Besides the ease of use, I don’t have much to contribute yet.

In the summer, I have been opening my oil cap to allow some of the humidity to escape but unsure how much it helped. Here in central AR, we are pretty humid so I am hoping this will help.

[carusoam]

There is a near current thread discussing leaving heat on as a method of minimizing rh in the engine...

But, it takes some additional effort to do that...

One MSer included graphs of RH captured from inside the engine during the experiment...

Best regards,

-a-

[DonMuncy]

John,

I have one I designed and built, which I have been using for 10 years. Picture in my album. I have no idea whether it helps or not. Like many things in aviation maintenance, we never have "proof" of their value. But it is a fairly cheap way to increase your odds.  

[amillet]

I bought this from Aircraft Spruce and used it on my 1st engine when I didn’t fly for about 6 weeks due to rotator cuff surgery.  I discovered later that the breather tube where the dry air is directed into has a “whistle slot” that probably let 90% of the dry air escape. You’d have to take the cowl off to cover it up.

An excerpt from an edition of the Lycoming Flyer, entitled "The Whistle Slot", states:

"Moisture is expelled from the engine crankcase through the breather tube which often extends through the bottom of the engine cowling into the air stream. Under very cold conditions, this moisture may freeze and continue a buildup of ice until the tube is completely blocked. It is normal practice for the airframe manufacturer to provide some means of preventing freeze-up of the crankcase breather tube. The breather tube may be insulated, it may be designed so the end is located in a hot area, it may be equipped with an electric heater, or it may incorporate a hole, notch or slot which is often called a "whistle slot." 

The operator of any aircraft should know which method is used for preventing freezing of the breather tube, and should insure that the configuration is maintained as specified by the airframe manufacturer. Because of its simplicity, the "whistle slot" is often used. Although the end of the tube may extend into the air stream, a notch or hole in the tube is located in a warm area near the engine where freezing is extremely unlikely. When a breather tube with whistle slot is changed, the new tube must be of the same design."

I don’t know if that contributed to engine only getting to 1812 hours when it started making metal?

[CaptRJM]

I built a recirculating system and have used it for over 10 years. I live in Coastal NC and the humidity is always high.  We have borescoped my crankcase and don’t see any evidence of corrosion. 

Part of my system is I turned a “plug” that goes up the vent line past the “whistle slot” so the dry air doesn’t vent to atmosphere. 

I’ve looked at Don’s design and when I build a replacement in the next few months it will be something similar to his. 

[INA201]

I place this Stanley heater under the left cowl flap and turn on low.  I put a cowl plug on the left and plug half of the right side and the right cowl flap remains open as does the left of course. The engine compartment and engine temp remains at a minimum of twenty degrees higher than ambient temperature. On the cool misty zero temperature dew point spread days there is no condensation on the engine or components.  I would assume that the dew point inside the crank case also stays high enough to avoid condensation.  I guess I could test this theory by putting water inside a bare steel tube and keep one warm and one ambient and the rust would show pretty quickly. I’m too lazy to test it out.

[Bryan]

The EngineSaver I bought has a long enough straw insert and plug to go past the “whistle slot” and explicitly directs you on how to use concerning this.

[Danb]

I’ve had an engine dehumidifier for a few years I have no clue if it helps? Peace of mind 

[DMM]

I use a homemade closed loop dehumidifier.  This morning the RH in the hangar was 67% at 50 degrees F.  The air in the crankcase was 34%.  Hopefully this improves my odds - who knows for sure. 

[jetdriven]

I think RH below 40-50% definitely helps. There are times in the morning the case and the prop are dripping with condensation.  It’s raining inside your engine too 

[jaylw314]

49 minutes ago, jetdriven said:

I think RH below 40-50% definitely helps. There are times in the morning the case and the prop are dripping with condensation.  It’s raining inside your engine too 

Egads, even in a hangar?

I'm in Oregon, and even with all the rain on the ground and a breezy hangar, the hangar keeps the temperature from changing fast enough to develop much condensation, even when there's condensation on cars parked outside.  Then again, we don't exactly have a tropical climate...

[Browncbr1]

I built one, but it’s a lot of hassle to reset the crystals every so often.   So, I just fly the plane at least once per week and leave preheat on in winter time.  If I have to leave the plane alone for more than 2 weeks, I’ll hook it up though.  

[Marauder]

I built one, but it’s a lot of hassle to reset the crystals every so often.   So, I just fly the plane at least once per week and leave preheat on in winter time.  If I have to leave the plane alone for more than 2 weeks, I’ll hook it up though.  

Get 2 or 3 of these. Once they get saturated, you pop another one in and plug the saturated one in to renew it.




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[Danb]

Where do you put that rascal Chris 

[Marauder]

Where do you put that rascal Chris 

Inside a seal case that has a vacuum pump pulling air from the engine and back into the engine. Once it gets saturated, pop another one in the box and recharge the saturated one.


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[Gary0747]

I would never use one of these systems if the desiccant they used contained magnesium or calcium chloride salts.    Several even commercial systems have attempted to use these materials.  It is possible to create very fine particulate chloride salts that you do not want inside your engine.  Very corrosive.  

[jaylw314]

1 hour ago, Gary0747 said:

I would never use one of these systems if the desiccant they used contained magnesium or calcium chloride salts.    Several even commercial systems have attempted to use these materials.  It is possible to create very fine particulate chloride salts that you do not want inside your engine.  Very corrosive.  

If it is what I have seen, they usually use large silica gel beads with a moisture-sensitive dye to tell you when it needs recharging.  Nifty, but gets saturated quickly and doesn't lower humidity as much as calcium salts

[Gary0747]

Some use silica gel but some use the chloride salts mentioned which are easier regenerated since there is no thermal degradation issues like silica gel has.  Silica gel should be fine to use but avoid the salts.