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dehydrator condition after a season

A5555

Well Known Member
on my last flight I noticed my oil temp was only 158F as I have not blocked my oil cooler. I attached the dehydrator an pulled the engine humidity down.

going on my second year this dehydrator material looks OK. I have a closed loop system and just let it run 24/7.

IMG_20211025_141051.jpg
 
on my last flight I noticed my oil temp was only 158F as I have not blocked my oil cooler. I attached the dehydrator an pulled the engine humidity down.

going on my second year this dehydrator material looks OK. I have a closed loop system and just let it run 24/7.

IMG_20211025_141051.jpg

Sure looks like the closed loop system is a good method.

I've got the black max electric dryer, and I run it all the time, but since it does not have humidity monitoring, I can't honestly say that I *know* it's working. I am kind of looking out for an easy to use humidity checker - I've got one of those USB logging temperature/humidity monitors that I used for a while, but it requires regular removal, boot windoze, read the data, etc.

The blackmax guy needs to add two things: humidity monitoring to confirm it's working right, and a bit of heat to solve the pre-heat problem.

Perhaps I can send the dry air output of the black max to some beads to look for color change...
 
return line sensor

cheap engine return line sensor. all this does is indicate it's doing something. the lowest reading capable is 10%.

reading from the cool spring days last year. these were before is started using the cowl inlet air dams permanently in the Winter.

all mounted is an old luggage case so I can be the traveling dehydrator man. :)

IMG_20200403_152017.jpg


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No more black beads.

Steve, All the black beads are why I switched to a 5 min purge in advance of providing dry air though the bead bed. The purge gets the super water rich and oil vapors out of the crankcase fast. The purge uses a mattress inflator.
 
Steve, All the black beads are why I switched to a 5 min purge in advance of providing dry air though the bead bed. The purge gets the super water rich and oil vapors out of the crankcase fast. The purge uses a mattress inflator.

yeah, a 30 minute purge without the return line connected is now my plan. extend the life of the beads!
 
I built a dehydrator. I use it religiously despite the fact that there's no objective evidence that it has a positive effect on preventing corrosion. However, my rationale is that if moisture/condensation in the engine contributes to corrosion then it makes sense that limiting moisture standing in the engine is a positive thing. An IC engine generates a lot of water, and additionally, every time the crankcase temp crosses the dew point, condensation occurs. I could keep the engine on a heater 24/7 and keep the crankcase temps above the dew point, or I can manage the humidity inside the crankcase and control the dew point/prevent condensation that way.

I have 15 lbs of silica gel and use 7.5 lbs at a time in my dehydrator. I run it open loop (closed loop is likely better, I agree) and every 2-3 weeks in the summer I exchange orange for blue silica and pop the orange stuff in the oven for a few hours to turn it back blue. Then repeat. I do connect a return line from my crankcase vent (Antisplat separator) just to keep track of the outgoing crankcase humidity. The aquarium pump I use doesn't support a return line. I do have such a pump...I just haven't gotten around to hooking it up yet. As it is, I consistently see humidity in the return air at about 10-15% with ambient humidity in the 50-75% range.

Again, this is all empirical. No data to support dehydrators as being efficacious in establishing TBO, but I proceed because it's cheap, easy, and the doctrine of "can't hurt/might help".

ETA: I did use a mattress inflator for awhile as a purge...kind of fell out of that habit. Also, I did struggle with a good way to connect the inflow to the oil dipstick...finally settled on a plain old rubber stopper.
 
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Two Thumbs Up!

yeah, a 30 minute purge without the return line connected is now my plan. extend the life of the beads!

That should be pretty good, I bought some flow meters, then did some calculations for % of original gas removed for a 7000 in^3 volume. 99% is removed with the mattress blower in 3 min, and 30 min for the desiccant pump. Calculations were roughly verified via humidity measurements. I have flow rates if you want them.

The 30 min purge should also push out most of the moisture the beads have been eating, yield much longer bead life (r.e. moisture).
 
A possible point of correction.

Good paper. Good read. Here in Humid AF Florida, lots of extra precautions are needed to protect your investment. The day/night temperature swings here help airframes and PPs to “breath” in moisture every day/night cycle. If ignored, it can make things ugly, quick.

The publisher stated there are areas within a PP that the use of a dehydrator could be ineffective because of stagnant air concerns. This is probably less of a concern than it appears at first glance.

Fluid chemistry gravitates toward equilibrium. Given time at condition, wetter air will become drier if in fluid contact with such (and vice versa). I’ve engineered many types of driers into steam turbine lube oil systems where the oil becomes over saturated. Vacuum dehydrators are very effective in drying this fluid to levels below it’s typical “natural” water content. Despite the saying, oil and water do mix to a degree. Even though only a very small portion of the oil actually processed, the tendency for said equilibrium completes the job. Will be buying or building a dehydrator if I can ever get this build finished.

Slight drift but relevant to the posted paper, I’m a big time fan of the Aircraft Specialties Lubricants (Camguard) engineers. If you ever get to speak with or come across an article from Edward Kollin, take advantage of it.
 
Dehydrator data

This is data I collected with and without a closed loop dehydrator. The temperature and humidity sensors were inside the crankcase.
 

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Good paper. Good read. Here in Humid AF Florida, lots of extra precautions are needed to protect your investment. The day/night temperature swings here help airframes and PPs to “breath” in moisture every day/night cycle. If ignored, it can make things ugly, quick.

I sure would like to see some test results to support this. While the engine mass could be a factor, we also have barometric issues and standing water in the engine. Mass transport process also may weight in.

My assertion is that ambient humidity has no bearing on the crankcase humidity -in or out. Combustion chambers with open valves are another story, but not what we are addressing with the typical dehydrators.

Lots of OWT so I ran a test. I took at juice bottle dryed it then added some water. The cap modified with 5/8" ID hose to represent the breather tube. I prepared for change. If there was breathing then there would be loss of mass. Short version. After 3 months in my garage the test was terminated as no change in mass could be measured. Lots of temperature change in there from normal changes and sudden due to opening and closing of the door. Everything a hangar would have but the stabilizing thermal effect of a crankcase.
 
...
My assertion is that ambient humidity has no bearing on the crankcase humidity -in or out. Combustion chambers with open valves are another story, but not what we are addressing with the typical dehydrators.

...

Not to ignore your other interesting comments - is there a position that has all intake and exhaust valves closed? I'd guess this position, but not 100% sure.

Lycoming Engine All Valves Closed.png

(Stolen from this video: https://www.youtube.com/watch?v=gIdXLMVP6VU)
 
I sure would like to see some test results to support this. While the engine mass could be a factor, we also have barometric issues and standing water in the engine. Mass transport process also may weight in.

My assertion is that ambient humidity has no bearing on the crankcase humidity -in or out. Combustion chambers with open valves are another story, but not what we are addressing with the typical dehydrators.

Lots of OWT so I ran a test. I took at juice bottle dryed it then added some water. The cap modified with 5/8" ID hose to represent the breather tube. I prepared for change. If there was breathing then there would be loss of mass. Short version. After 3 months in my garage the test was terminated as no change in mass could be measured. Lots of temperature change in there from normal changes and sudden due to opening and closing of the door. Everything a hangar would have but the stabilizing thermal effect of a crankcase.
As I said, there’s no good data to demonstrate that using a dehydrator will make a difference in getting an engine to TBO. It seems reasonable to draw that conclusion, but inductive reasoning is all we have to support it. OTOH, I have about $30 in my dehydrator and after a flight I can hook it up in 60 seconds. The time and money that it costs me is negligible in the scheme of aircraft ownership, so…why not?
 
@ BillL

I respect your posts. You're one of the good guys who actually backs-up his statements with related theories and application versus anecdote; hence my respect.

Your quote: My assertion is that ambient humidity has no bearing on the crankcase humidity -in or out

I'm surprised by this but maybe I'm not completely following all of your logic. Relative volumes, Delta T spreads (winter months with sunny days), alphas of the relevant materials especially relative to air, etc.

In my early experience, our initial go-to test for this phenomena was actually a Ph test (coastal air) and followed by measuring air quality with data logging when needed. For mission critical systems, we wound up reclassifying enclosures, adding trickle purges, adding space heaters/keeping motor field windings juiced, etc.

Following your logic, an engine dehydrator would be of zero benefit. Unlike your other posts, I'm not in agreement.

Respectfully,
msf
 
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@ BillL

I respect your posts. You're one of the good guys who actually backs-up his statements with related theories and application versus anecdote; hence my respect.

My assertion is that ambient humidity has no bearing on the crankcase humidity -in or out

I'm surprised by this but maybe I'm not completely following all of your logic. Relative volumes, Delta T spreads (winter months with sunny days), alphas of the relevant materials especially relative to air, etc.

In my early experience, our early go-to test for this phenomena was actually a Ph test (coastal air) and followed by measuring air quality with data logging when needed. For mission critical systems, we wound up reclassifying enclosures, adding trickle purges, adding space heaters/keeping motor field windings juiced, etc.

Following your logic, an engine dehydrator would be of zero benefit. Unlike your other posts, I'm not in agreement.

Respectfully,
msf
Maybe I did not make the statement clear. My bad, I quibble that Florida humidity is worse for crankcase humidity than Phoenix. I assert is it bad in both cases and no beneficial difference, thus a crankcase dehydrator is beneficial to both.

So the question is: what the RH of the crankcase is in a humid environment like key west vs phoenix. At shutdown the crankcase is filled with mostly combustion products and that means high amount of water lb water/lb Dry air. And we know that exhaust will condense water a temperatures well above any typical ambient. The result is that on shutdown saturation will occur and condense water. So how does ambient RH affect that with time or at all? My experiment indicates very little in this regard.

OK now, lets dry the crankcase after shutdown, assume instantly. Will the humidity in the closed crankcase change? How, what is the process? Breathing? How long does it take? Granted my experiment says mass transport can be eliminated as a significant factor, and barometric changes too. Thermal mass, though, was not a factor included in this test and may change the result.

Is there any anecdotal evidence to say the engine in florida has higher internal corrosion than Phoenix? I don't know, but in years of looking for others experience have never seen any.

So, I will stand by my assertion until evidence or experiment can change that. Data is always welcome and a time based test of crankcase humidity after being purged and desiccated, is of great interest. I am always ready to be schooled!!:D
 
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Regarding the monitoring of the humidity in the engine, I noticed what was I think Steve's little humidity sensor in a plastic case in this thread in an above post. I just thought I'd give a tip on a way that I really like, for a hanger that does have wifi connectivity.

Go on Amazon and search up "Yolink Humidity sensor". You'll find a nice little unit for about $25 (does require a hub, but I find their hub to be very reliable). It's It's a little box about 2" x 2" x .75" or so, with an LCD screen. Shows temperature and humidity. I bought a bunch of these. I have one in each hangar, one that I put on the top of the engine under the cowl in the winter that shows my engines warmth, so I can see when my heater is on and if it's all warmed up. I also threw one inside each of the cases that house my dehydrator desiccant packs. With the latter ones, I can monitor and alert on the humidity on my phone. What I find is that after a flight, I get a big spike in humidity, and after the system runs for a while it drops real low. I average around 10-14% humidity in the system. I use that as an indicator on when to regenerate my media. When I see humidity hit 20%, I just swap it out, bake it up for 3 hours at 265F, and put it in the jug ready to go for the next swap. Only have had to do it a a couple times since winter I believe.

Anyway, for those who built it DIY, if you have wifi, give that yolink one a try.
 
I

Lots of OWT so I ran a test. I took at juice bottle dryed it then added some water. The cap modified with 5/8" ID hose to represent the breather tube. I prepared for change. If there was breathing then there would be loss of mass. Short version. After 3 months in my garage the test was terminated as no change in mass could be measured. Lots of temperature change in there from normal changes and sudden due to opening and closing of the door. Everything a hangar would have but the stabilizing thermal effect of a crankcase.

Surprised by that result. I would have expected some water loss. A more relevant test would be to measure the humidity level inside the bottle. Not sure we can assume that the lack of water mass elimination directly correlates to a constant high humidity of the air mass in that bottle. I would expect that that air inside the bottle matches the ambient humidity level.

Larry
 
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RV8CH - I have been using multiple Elitech GSP-6 data loggers. I also have made some inline meters that show the return air from the engine (see photo) in addition to a meter in the media chamber to monitor the air going into the engine.
 

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Surprised by that result. I would have expected some water loss. A more relevant test would be to measure the humidity level inside the bottle. Not sure we can assume that the lack of water mass elimination directly correlates to a constant high humidity of the air mass in that bottle. I would expect that that air inside the bottle matches the ambient humidity level.

Larry
I was surprised as well. :eek:

Good idea, I am considering an in-the-bottle humidity test. Dry the air, then add a 20" tube of 5/8" ID and a humidity meter inside. I'll have to think about the thermal mass effect and how to simulate that. More thinking about a way to simulate the breathing effect of temperature and barometric changes is also needed.

To the humidity level in the bottle with liquid water - -it will remain at saturation or 100%. In the law books somewhere. With breathing, it would have seemed there would have been some loss, but maybe the loss was within the measurement accuracy and repeatability error.
 
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