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First Starts - Crankcase condensation-a data point

BillL

Well Known Member
FYI - There are dehydrator threads, and water collection in the oil separator threads and winter flying threads. All relate to water/moisture in the crankcase and corrosion issues.

As a datapoint, yesterday I helped (watched) a 10 friend with his first engine start. We checked for leaks then cowled and he did some taxi runs to break-in the brakes. All went well. With 2100 rpm mag checks and such - I guess it was 45 min of running (correction 20 min). Very little at idle and it was preheated to 145F with a Reiff preheater system overnight. OAT was 40F with wind. Oil temp at end of testing was 165F

I have been looking at dehydrators and cobbled one together for experimentation. I thought it would be good to use on a first start because, it is cold, short run, rich and expected some blowby.

Post run, we hooked the dehydrator, powered with a little aquarium pump, the dry air into the breather pipe and moist air out the oil fill tube (540).

About an hour later, there was water collecting in the exit hose. The warm, moist air was condensing water in the hose! - He estimated 1.5 tablespoons!

We were both shocked to see that much water. The desiccant was not weighted or measured, but surely there was more water coming out via adsorption.

Now you know, definitively, how much water you could leave in the crankcase for a short engine run. Decisions about dehydrators, water returning to crankcase via oil separators and such are left to other treads, but everyone about to expose your expensive new engine to a joyful first start should take note of this situation.
 
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FYI I guess it was 45 min of running.

It sounds like it was very humid conditions, but at this point I think there should be more concern about the effect all the ground running will have on ring/cyl break in than the amount of moisture that was in the engine.
 
45 minutes of running seems like an extremely long time for a first engine start, especially with the cowl on. How high did the CHTs go?
 
Dehydrators are BS

I own a scuba compressor. Desiccant doesn't work effectively the way its being used here.
In general, we run on the order of 3000psi air over desiccant in order to get it to pull out the final bits moisture from the air for scuba purposes - prior to that its done by mechanical separation. The main point is desiccant requires high gas dwell time. That's done by high pressure and a small amount of air being essentially trapped in the desiccant path for a long time, then being allowed to exit.

The underlying theory of pumping dry air into an engine to try to evacuate moist air is fine. But the assumption here is that ambient air is at least equal in water content to the air in an engine. That is false. And even if it weren't false, the % of water content taken out of the air by running huge volumes of air thru a desiccant at ambient pressure in this fashion is minuscule. Its not doing what people think it is. It picks up a little, yes - because desiccant beads are just a chemical sponge. But they are very very little sponges not kitchen sponges.

What is happening is that large volumes of already dry ambient air (dry compared to whats inside the engine) is being forced through the sump. Thats enough to do the job expected here.

Don't believe me? How bout this. Get out of the pool in Florida and stand under a ceiling fan. Do you dry off faster? Yup. Forget that Florida is wet air already. Its drier than your pool body.

On the old thread someone suggested a shop vac to pull the moisture out. That makes sense, tho shop vacs are not explosion proof, so that's a nono. But pumping hot air thru the engine, like from hairdryer, yeah that would make sense, with careful attention to not over pressurize the crank case.
 
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This is data, implications are your department.

It sounds like it was very humid conditions,
40F ambient not a cloud in the sky, cold wind from the north. Don't know the DP.
45 minutes of running seems like an extremely long time for a first engine start, especially with the cowl on. How high did the CHTs go?
Cowl off for first few minutes. Used Lycoming recommendations for first data checks. CHT's overall less than 300F

All can draw your own conclusions on how to use the data. Maybe it was not 45 min, maybe it was 30 min (ok corrected to 20 min), I did not measure it, but this first start will now sit for 30 days while airworthiness, final pilot transition training and other systems/paperwork are completed.

Oh - desiccant - granted different types will lower the moisture to different relative humidity levels. The air was recirculated (slowly, very low space velocity), we just want the RH lower than 100%. 3 lbs of indicating silica gel was used. The Equilibrium Moisture Content / Relative Humidity Isotherm chart shows that low RH will be maintained for low EMC. You are right, for continued use, the EMC could not be allowed to increase to saturation, but we don't need it truly dry like a scuba tank. How low should the RH be? Another research study, not gonna happen.

Remember, this was a first start. The engine could not be heated thoroughly like a cruise flight. It will sit there waiting for the DAR, sign-off, flight training etc. Maybe 4 weeks. Honestly, it probably would not have done irreparable harm to have left it, but did it reduce the inception and progression? Who knows, with special oils maybe not, but mineral oil and no additives? For $20 of parts, vs a $40,000 engine, did it hurt? - no, did it help? absolutely. How much? -open for debate.

So much emotion, so little facts and data. Please, not in front of the newbies.

Meanwhile, this data stands.
 
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Just last week we put our street sweeper back in service from the winter, it has a 4 cycl Cat Diesel pony engine for the large fan, over the winter we start it once a month and shut it down. so... last week when I fired it up I raised the hopper and ran the engine at high idle, after 15-20 min I saw large amounts of steam coming from the engine, as I walked up to it I thought it had a radiator leak or something then I saw huge amounts of steam and water dripping out of the crankcase breather hose! moisture and water boiling out of the engine oil and crankcase!
So there are two contradicting missions for your engine run, One, you want the oil to get hot enough to boil off the water content, but, Two, you don't want the cylinders and rings to get hot and glazed over before you do a proper high load run to seat the rings.
 
It sounds like it was very humid conditions, but at this point I think there should be more concern about the effect all the ground running will have on ring/cyl break in than the amount of moisture that was in the engine.

One of the byproducts of hydrocarbon combustion is H20. Because the internal space of an engine is filled via blow-by gases, post-combustion, the air in there is always moisture laden.

You can see this when you first start your car. The exhaust pipes and muffler fill with water before they become hot enough to keep it from condensing/heat induced vaporization. When a car is still warming up, you can see water pouring out of the tail pipe at a stoplight.

Larry
 
So much emotion, so little facts and data. Please, not in front of the newbies.

Well, you didn't quote my post regarding an extended ground run, but it actually was for the newbies..... (keep them from thinking this is a good idea).

A first engine run (regardless of your position on doing it a year before first flight or as late as possible) for more than just a couple minutes at very low power to allow for confirming correct operation of instrumentation and confirm no leaks, is a bad idea.

If a cooling shroud (as shown on page 10 of THIS DOCUMENT) is used so that the engine can be run at maximum continuous cruise power, then an extended ground run would not be detrimental.
 
Aircraft cooling systems were NOT designed for extended ground runs. They are designed for in-flight cooling. Running on the ground does NOT produce balanced cooling for the cylinders. ESPECIALLY on a brand new engine.

Someone noted before (post was deleted) that this extended ground running of the engine can and will, in most cases, cause cylinder glazing.
They also noted that they had not been wrenching on Lycomings for 45 years. Well, I have. And it is fact, not emotion.
 
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Hey Bill,
Not wanting to pile on here but to help a little with the data point.
I have to assume some things here as the initial process is a little vague.
If you are pumping 165 degree air into a tube surrounded by 40 degree ambient air you will get condensation no matter how dry the 165 degree air is. (within reason).
Example= 120 degree air at 20% (very dry air) has a DP of 65-70 degrees.
100 degree air at 50% RH is has a DP of 75-80 degrees.

You have basically set up a system similar to a refrigerated air dryer used on a compressor.

I have no doubt the engine developed a large amount of water.

http://www.uigi.com/UIGI_IP.PDF
 
Well, you didn't quote my post regarding an extended ground run, but it actually was for the newbies..... (keep them from thinking this is a good idea).

A first engine run (regardless of your position on doing it a year before first flight or as late as possible) for more than just a couple minutes at very low power to allow for confirming correct operation of instrumentation and confirm no leaks, is a bad idea.
Scott, just 5 min was the first run for a leak check (no cowl). The last 15 min was higher power mag check and brake conditioning. I thought it was a minimum of information gathered for evaluation of a safe first flight. Caution on minimizing low power time is noted.

Hey Bill,
Not wanting to pile on here but to help a little with the data point.
I have to assume some things here as the initial process is a little vague.
If you are pumping 165 degree air into a tube surrounded by 40 degree ambient air you will get condensation no matter how dry the 165 degree air is. (within reason).
Example= 120 degree air at 20% (very dry air) has a DP of 65-70 degrees.
100 degree air at 50% RH is has a DP of 75-80 degrees.

You have basically set up a system similar to a refrigerated air dryer used on a compressor.

I have no doubt the engine developed a large amount of water.

http://www.uigi.com/UIGI_IP.PDF

EEK! I was hoping never to refer to the psychometric cart again! It is a 540, so the crankcase volume is larger. it was ambient air (temp 40F) entering the breather tube and the engine was reading 165F for oil temp. Your observation 165F steam condensing in the 40F tube is clearly what was happening. The surprise is that it accumulated so much water so quickly. It also gives credence to the shop vac procedure to evacuate the crankcase while it is still warm. Not sure what was vague in the post.

Based on Scotts comments, maybe the brake conditioning could/should be done after first touchdown, but it depends on the runway length for the first flight. This aspect is certainly worth further discussion in order to minimize the run time before reaching 65% power break-in on TO.

A little off the original topic, but Mel, I got the impression that the Lycoming nitrided steel cylinders were not as sensitive as some ultra hard ceramic coated types that need to get loaded ASAP. The engine was preheated to help avoid/delay issues. The next run is first flight. Do you think 20 min has already caused an issue?
 
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I'm not sure how sane I am to wade into this thread, but I do have a little experience (30 years) with gas dryers and desiccants in the various labs that I've worked in.

I set up a gas dryer using an aquarium pump, desiccant container (laboratory gas drying tube) and a closed loop to recirculate air through a brand new, test stand runs only, engine in my shop. Contrary to a previous post, the proper desiccant is quite effective at removing moisture at low flows and low pressures. We do this in the lab a LOT.

I have kept meticulous records on this "just for fun project". So far, I have removed more than 100ml (or 100g) of water from the crankcase environment. Of course, the engine is completely sealed. That's a given. That's also a pain in the behind to accomplish. A huge plastic garbage bag around the engine is one way...

So, it is entirely possible to remove water from your crankcase using a desiccant. It's slow, somewhat expensive, and 100% impractical to do with an engine that is on a regularly flown aircraft. But if you have a $30,000 engine sitting in your shop waiting for you to finish an airplane... it's entirely reasonable to get it dried out and keep it that way until you're ready to run it.

YMMV.
 
A little off the original topic, but Mel, I got the impression that the Lycoming nitrided steel cylinders were not as sensitive as some ultra hard ceramic coated types that need to get loaded ASAP. The engine was preheated to help avoid/delay issues. The next run is first flight. Do you think 20 min has already caused an issue?

Well 20 minutes is a long ways from the original estimate of 45, but still too long for my taste. Normally I don't like to see more than about 5 minutes of ground run on a new engine.
You are going to add another 5 minutes in preparation for that first flight. Yes the Nitride helps but does not totally prevent glazing.
No way of knowing for sure until you see if the rings "seat" properly.
Good luck.
 
A little off the original topic, but Mel, I got the impression that the Lycoming nitrided steel cylinders were not as sensitive as some ultra hard ceramic coated types that need to get loaded ASAP. The engine was preheated to help avoid/delay issues. The next run is first flight. Do you think 20 min has already caused an issue?

I have standard Lyc. nitrided cylinders. I mistakenly let one cylinder get to 450* for a minute or two in the first hour of flight and that cylinder became glazed. I had to pull it for a re-hone. Not a difficult project (honed myself), but was a full day that I would rather have been flying.

Lary
 
I struggled with trying to understand what to do with a new Engine

Where I finally ended up is that you can't hurt the break in by running it too little on the ground. But there was quite a bit of info on this site and from other sources that recommended a fair number of ground runs most for short periods of time. I went with the least ground run time feeling it was the least risk approach at least for the engine, not so much for yours truly though.
But it would be nice to fully understand what is causing the glazing of the cylinder walls. Is it just heat, so as long as you keep it under a set temperature you can run it as many times as you want? or is there something else in play here? I would have liked to have done more ground runs if that's possible without hurting the break in.
 
Where I finally ended up is that you can't hurt the break in by running it too little on the ground. But there was quite a bit of info on this site and from other sources that recommended a fair number of ground runs most for short periods of time. I went with the least ground run time feeling it was the least risk approach at least for the engine, not so much for yours truly though.
But it would be nice to fully understand what is causing the glazing of the cylinder walls. Is it just heat, so as long as you keep it under a set temperature you can run it as many times as you want? or is there something else in play here? I would have liked to have done more ground runs if that's possible without hurting the break in.

When I toured the ECI plant last fall, they explained that in their run-in cell, they perform a lengthy run-in process that begins with relatively long runs at low power settings. They have forced air cooling and can keep the cylinder temperatures low during this process.

Unfortunately, we did not discuss particular temperatures or limits for that process.
 
I have been doing a lot of research on this lately as I am about to fly with my new ECI cylinders for the first time. My main sources were the ECI break-in instructions and the guide by Mahlon that is online here a VAF. Both agree that the real enemy is heat - theoretically you can ground run as long as you want as long as you keep CHT's under control. ECI says under 400, Mahlon says 350, and both specify runs under 3-5 minutes.

For me, having installed my own FWF, I would not be satisfied with one brief, low power run. I have done about 4 separate, short runs under 3-4 minutes, max CHT about 330 degrees and usually much lower, to include brief taxi test and break wear-in, and a very brief static RPM check.

Granted, I'm not Mel or any sort of guru, but two reputable sources assured me that a few runs were just fine as long as I kept temps down. I don't know what the OP saw for CHT's, but I think that would be the most important factor. But, this is all thread drift anyways...What we can all agree on is that the best thing we can do for our engines is GO FLY!

Where I finally ended up is that you can't hurt the break in by running it too little on the ground. But there was quite a bit of info on this site and from other sources that recommended a fair number of ground runs most for short periods of time. I went with the least ground run time feeling it was the least risk approach at least for the engine, not so much for yours truly though.
But it would be nice to fully understand what is causing the glazing of the cylinder walls. Is it just heat, so as long as you keep it under a set temperature you can run it as many times as you want? or is there something else in play here? I would have liked to have done more ground runs if that's possible without hurting the break in.
 
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Chris, I did something very similar. Mine's a box-stock Lycoming YIO-320-D1A. I ran it probably five times and used a peak CHT of 350 degrees as the point to shut it down, which usually worked out to 3-4 minutes.

Just watch those temps during climb, and shallow out the climb when at a safe altitude to keep the temps in check. I had my EFIS alert set to 425 degrees, and a couple touched 440 briefly in the early going, but only for maybe 15-20 seconds until I achieved a higher airspeed. At the 40-hour mark, oil consumption is pretty low, maybe a quart every 10-12 hours, so I consider it fully broken in. The left-side exhaust pipe is always slick and gooey after a flight, so a little of that use is the oil puking out the breather tube (running it at 6 quarts).
 
I have been doing a lot of research on this lately as I am about to fly with my new ECI cylinders for the first time. My main sources were the ECI break-in instructions and the guide by Mahlon that is online here a VAF. Both agree that the real enemy is heat - theoretically you can ground run as long as you want as long as you keep CHT's under control. ECI says under 400, Mahlon says 350, and both specify runs under 3-5 minutes.

For me, having installed my own FWF, I would not be satisfied with one brief, low power run. I have done about 4 separate, short runs under 3-4 minutes, max CHT about 330 degrees and usually much lower, to include brief taxi test and break wear-in, and a very brief static RPM check.

Granted, I'm not Mel or any sort of guru, but two reputable sources assured me that a few runs were just fine as long as I kept temps down. I don't know what the OP saw for CHT's, but I think that would be the most important factor. But, this is all thread drift anyways...What we can all agree on is that the best thing we can do for our engines is GO FLY!

Glazing comes from heat; It is oxidized (i.e. burnt) oil in the valleys of the cross-hatch. However, it typically only forms before the rings and cylinder walls take a set (i.e. wearing down the peaks to a flatter surface and reducing the depth of the valleys). You'll find detailed descriptions of the reasons for it on the web, but it is about getting the correct oil film thickness to remain on the cylinder walls, as happen post-ring set.

There's no argument that the best way to seat rings is high load (i.e. MAP), though most say high power. There is some argument about whether or not you can impair the process by not introducing a high load. I think that the auto industry proves that high load is not required in most cases. How many people do you think "baby" a new car vs. running it at 75% power. I would speculate a very high percentage. Most of these cars take a set just fine and don't burn oil, even before they started using plateau honing (though glazing was more common back then), which almost eliminates the ring setting process (happens within seconds or minutes).

I am not suggesting anything but the traditional recommended break-in process. Only addiing some data points to the argument above about differing recommendations to break-in. My experience glazing a cylinder tells me it's much better to use less than 75% power to avoid excess heat. Sometimes you have to balance factors to reach an optimal result. You'll find a similar recommendation from Mike Busch.

Larry
 
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Epilog

Someone mentioned diffusion, mass transport (blah blah blah) of water vapor out the breather. Even if the terms were not spot on, it was a good thought, so I ran a little test. A few oz of water in a bottle and a 5/8" id hose about 3' long. Weighed it, hung it in my garage for 4 days. Weighed it again several times. Garage temp +20f over ambient, and below freezing temps outside lowered the dew point considerably, so not too unlike a hangar. Pretty good conditions for water loss actually.

The data? 00.1g loss after 4 days. Minuscule. So, for your first start, and with conclusions of others above:

1. Either first start and fly the same day, or
2. Do your first start, then take a vacuum and suck air through the engine (clean dust free hangar) while it is still hot, for 3-4-5 min. That should displace all (or most of) the air in the crankcase and get the steam (literally) out of there. Turn on the Reiff (if you have it) or put a light bulb under it (in a safe place) to keep it above ambient.

You should be protected even without oil additives. You can go further with a dehydrator, desiccant plugs etc, but the above is a minimum for protection of a new engine.

Thanks for the contributors to this conclusion and proper warnings about break-in.

Diffusion%2BTest.JPG
 
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