Use a FILTER

If you have 10% humidity and you compress several gallons of air do you not put water in your compressed air?

When I lived in the Willamette Valley in Oregon, I used to use Harbor Freight dessicant filters. They would turn color sitting for a few days without use. My bleed valve would spit water when the I filled from my tank, but my Shoebox’s and compressor ran hot even with a fan on them. Folks used to say people drown when they fall off their bikes in Oregon.

Where I live now is in a 1200 year drought cycle, most days I see the humidity at 25 %, if you run a hot compressor you will still get water vapor. Compressors that fill fast will always produce heat and water. When I first got my Altaros booster I tried to run it on my old Harbor Freight compressor, then with one CAT compressor and no fan, I made air and water.

Using three compressors and a 12 inch fan on each and three large dessicant filters resulted in mo water vaper when I bleed my fill lines.

That can be avoided with filters and cold running compressors, or slow filling with a hand pump.

The little disposable compressors with filters that look like they need a string attached for removal, fill fast, produce heat and thus water. The filters saturate too fast to keep water out and the compresser do not produce enough air to run with a proper filter. Once wet those filters contribute to the problem.

It is all about heat. If your bleed valve feels moist or spits when you bleed the system after a fill, you have water vapor.

RC
 
Nope, longer then that usually two to three and in all of this time I've never found even a hint.

My point.. Which ever rifle, no matter the reason or how long ago for the tear down you would have noticed your source of air was creating moisture and would have done something about it... That 1st or 5th rifle you have had apart gave you the confidence that your air source is giving dry air.. not everybody will tear their rifle down to inspect... (Especially if they are questioning their source of air they should) Which in my opinion is a danger to themselves and others if they bought the rifle from said person..

The OP was wise when he noticed a issue to do a tear down to catch a potential hospital bill..
 
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My point.. Which ever rifle, no matter the reason or how long ago for the tear down you would have noticed your source of air was creating moisture and would have done something about it... That 1st or 5th rifle you have had apart gave you the confidence that your air source is giving dry air.. not everybody will tear their rifle down to inspect... (Especially if they are questioning their source of air they should) Which in my opinion is a danger to themselves and others if they bought the rifle from said person..

The OP was wise when he noticed a issue to do a tear down to catch a potential hospital bill..
My point is that I use what is considered the worse method of filling and in very humid environment and I've never seen damage in the dozen and dozen of guns I had,.....I think it comes down to human mistakes and poor materials used by gun manufacturers.
 
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Matter is neither created or destroyed, unless converted to energy via a nuclear reaction. So pumping with or without heat, fast or slow doesn't create more or less water than is already in the air. Compressing air more slowly, other things being equal will be cooler. Cooler air has a lower dew point so less water will be in vapor form and more will be in liquid form that can be easily remove with a coalescer filter or cooling tower before it goes into your gun or tank. When you compress air from 1 bar to 300 bars and if you don't removing any of the water molecules by condensing, filtering and desiccant then trust me every one of those water molecules will be in your gun or tank! Whether you see any of that water as a liquid will depend on the temperature of the air and concentration of water e.g. moles per liter. That's why it is recommend to use a desiccant filter on the high pressure side where the water is more concentrated and easily to get a lower final water content.

e.g if you start off with 30% humidity at 1 bar removing 99% (sounds great and hard to do) of the water before compressing it to 300 bar then the tank will have about 3 times the density of water inside the tank compare to the water density of the ambient air before compressing it!
 
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This folks is why you use dry air to fill your gun. Thank you Brian at Veradium Air for being my airgun doctor. I personally filter my compressor. This is a newly purchased used rifle. View attachment 343309View attachment 343310View attachment 343311View attachment 343312

Yup! I see this kind of build up on fittings before my air drier but not after. I clean these fittings and tubes out periodically as well. Good thread to give guys a visual of what can happen!
 
Matter is neither created or destroyed, unless converted to energy via a nuclear reaction. So pumping with or without heat, fast or slow doesn't create more or less water than is already in the air. Compressing air more slowly, other things being equal will be cooler. Cooler air has a lower dew point so less water will be in vapor form and more will be in liquid form that can be easily remove with a coalescer filter or cooling tower before it goes into your gun or tank. When you compress air from 1 bar to 300 bars and if you don't removing any of the water molecules by condensing, filtering and desiccant then trust me every one of those water molecules will be in your gun or tank! Whether you see any of that water as a liquid will depend on the temperature of the air and concentration of water e.g. moles per liter. That's why it is recommend to use a desiccant filter on the high pressure side where the water is more concentrated and easily to get a lower final water content.

e.g if you start off with 30% humidity at 1 bar removing 99% (sounds great and hard to do) of the water before compressing it to 300 bar then the tank will have about 3 times the density of water inside the tank compare to the water density of the ambient air before compressing it!
Congrats!! Somebody finally got it right!! Compressing air is basically a closed system, and the amount of water molecules going into it still exist after compression – the question is more about “what happens to them?”

Very few people ever understand this topic properly – in truth it is fairly simple, but it is not common knowledge, and the typical ways of talking about it to “simplify” things makes it worse – specifically, the use of the term “relative humidity.”

Relative humidity (RH) is great for things like the weather report, where we want to compare the levels of humidity in air under different temperatures, but with basically constant pressures. In the realm of air compression, nothing it constant, so nothing is relative – we vary pressure greatly, and temperature too through the act of compression (don’t be fooled by the fact that our tanks start and eventually end at the same temperature – the air charge temperature during compression can probably approach 200F, depending on the compressor!).

We need to think and work in terms of absolute humidity, meaning the amount of water vapor contained in a standard unit of air, like 1 cubic meter at atmospheric pressure and a given “room” temperature. To facilitate it I will list a table of values of the amount of water vapor in grams that can exist in 1 cubic meter of air at 68 degrees F:
  • 68F, atmospheric pressure: 17.5 grams per cubic meter (maximum amount, at 100% RH - likely less)
  • 68F, 125 psi, 1.8 grams
  • 68F, 2000 psi, 0.1 gram
  • 68F, 3000 psi, 0.09 gram
  • 68F, 4500 psi, 0.06 gram
So think of that first data point and put it into practice – if you have 68F air at a low 15% RH, then there will be about 2.6 grams of water per cubic meter of air. You can’t see it, but it is there. Compress it to 3000 psi, and about 2.5 grams of water will have to condense out to liquid, which conveniently equals 2.5 ccs of water (boy I wish we switched to the metric system back in the 70s . . . ). Even though we don’t shoot at only 125 psi, I did include the data for air at that pressure for two reasons: first to illustrate how the maximum carrying capacity for water vapor falls off rapidly, and second to show how much can be removed “naturally” by the first stage of compression for those using either a Shoebox or air booster pumps. Air is much easier to "dry" with desiccants at 125 psi than at ambient temperature (and easier again at higher pressures - but higher pressure is not needed for desiccants to work; it only impacts how much desiccant is needed based on the amount of vapor needed to be captured).

Here is the first thing to remember going forward: in almost every situation after that first data point in the list, the air is going to be at 100% humidity once the conditions stabilize. So you have to realize this fact: air coming out of a compressor is at 100% humidity (either relative or absolute for those conditions) regardless of what it was going into the compressor. This will be true pretty much anywhere on the planet, other than running a compressor outside in Antarctica in the middle of winter . . .

Now here is the where the second really important point comes in: change the temperature of the air charge and we change the amount of water vapor it can hold. And when we compress air it gets hotter - a lot hotter, especially with the small fast pumps like Yong Hengs (if the water cooled head is getting ~50C, the air that is heating that head will be much hotter than that). And that means that the air charge can hold more water vapor in it when it comes out of the compressor – water vapor that will condense out to liquid when the charge cools back to ambient. Here is data like above, but at higher temperature, like what might be coming out of a compressor:
  • 150F, 3000 psi, 0.9 gram
  • 200F, 3000 psi, 3 gram
and
  • 150F, 4500 psi, 0.6 gram
  • 200F, 4500 psi, 2 gram
Notice that at 150F the air is holding ten times the water vapor as at 68F (and even more if hotter than that). So that means that if we take “nice dry air” from our 15% RH room and compress it to 3000 psi for a direct fill with a Yong Heng, and assume the air charge outlet temp is 150F, we will get about 1.7 ccs of water to condense and vent out for every cubic meter we compress, but that still leaves 0.9 ccs to pass into the reservoir as vapor – of which about 0.8 ccs will condense out to water when the charge cools to ambient (Note: people often say “heat makes more water” but that is not correct – heat allows more vapor to pass and condense later). So without some form of active water vapor management, liquid water will end up in the tank or gun. Anything that cools the air charge down helps condense out more water, and that is why coalescing “filters” work well (if I were running one, I’d put it in a bucket of ice water to further cool down the air charge).

Obviously we don’t pump a whole cubic meter into our guns in one refill, but this illustrates what happens, and liquid water will build up over time. For most air rifles about 30 fills will use this amount of air, depending on reservoir size and start and end pressures.

Also, this helps to illustrate why hand pumps – used properly – work so well. If we pump slowly, the air charge cools in the base of the pump before going into the gun. Add in frequent cool-down breaks for the pump – no more than about 50 pump strokes or so, then venting the line and letting it cool for 10-15 minutes – and the air charge stays cool enough that there really is nothing to condense out. Maybe a tiny amount, but it will likely flash to vapor again as the pressure in the gun drops (since lower pressure air can hold a bit more vapor). Done right, handpumping won’t lead to condensed water in guns, even in Hawaii😉.

Hope that helps!
 
Matter is neither created or destroyed, unless converted to energy via a nuclear reaction. So pumping with or without heat, fast or slow doesn't create more or less water than is already in the air. Compressing air more slowly, other things being equal will be cooler. Cooler air has a lower dew point so less water will be in vapor form and more will be in liquid form that can be easily remove with a coalescer filter or cooling tower before it goes into your gun or tank. When you compress air from 1 bar to 300 bars and if you don't removing any of the water molecules by condensing, filtering and desiccant then trust me every one of those water molecules will be in your gun or tank! Whether you see any of that water as a liquid will depend on the temperature of the air and concentration of water e.g. moles per liter. That's why it is recommend to use a desiccant filter on the high pressure side where the water is more concentrated and easily to get a lower final water content.

e.g if you start off with 30% humidity at 1 bar removing 99% (sounds great and hard to do) of the water before compressing it to 300 bar then the tank will have about 3 times the density of water inside the tank compare to the water density of the ambient air before compressing it!
We convert matter into energy all of the time but don't know how to convert energy into matter. Now plant life can convert energy into matter when plants and trees grow using light energy from the Sun. When I fill my tanks with my F10 my shop compressor is at the lowest point. It feeds the shop air to the F10 thru a coil type hose. The F10's compressed air has to climb another foot to reach the tank valve and thus the tank. I've been spending the last 2 days filling my 66 cuft scba tank from empty. The air temperature has been in the mid 40s where I'm filling the tank and I'm very sure there is no Liquid water getting into my tank. Today I'll finish filling it as it's up to 3600 psi now.
 
We convert matter into energy all of the time but don't know how to convert energy into matter. Now plant life can convert energy into matter when plants and trees grow using light energy from the Sun. When I fill my tanks with my F10 my shop compressor is at the lowest point. It feeds the shop air to the F10 thru a coil type hose. The F10's compressed air has to climb another foot to reach the tank valve and thus the tank. I've been spending the last 2 days filling my 66 cuft scba tank from empty. The air temperature has been in the mid 40s where I'm filling the tank and I'm very sure there is no Liquid water getting into my tank. Today I'll finish filling it as it's up to 3600 psi now.
A few things . . .

First, we do not convert matter into energy all the time, nor do plants convert energy into matter . . . we use chemical reactions to release energy, but preserve the mass of the system "all the time." And plants do the same in reverse using the energy from the sun - they do not create matter, but "rearrange" it with increased chemical energy obtained from the sun. If what you say were true, then the Earth would be gaining mass over the billions of years of plant growth from being exposed to sunlight. Mass is preserved in all these chemical reactions . . . .

Second, while you are almost certainly not putting any "liquid water" directly into your tank as you run your Shoebox, unless you are using an air dryer somewhere in the chain of compression you almost certainly are passing water vapor into the tank at a level that will condense into liquid water later when everything cools down. Gravity does not stop water vapor from going uphill, even if it does stop liquid water from doing so. What you believe does not matter - physics trumps our thinking. Not trying to offend, but such is reality . . . . the data is in the long post I wrote above, with the difference in your case being that the air coming out of a Shoebox likely won't be as hot as that from a Yong Heng - but still enough to carry excess water vapor (maybe around 0.5 gram per cubic meter).
 
Then why after filling my scba tank for 4 years when I opened it up it was completely dry inside? Oh, and descant will not remove moisture from the air fast enough to dry it before it reaches a airgun or tank. I used to use descant for drying test specimens for decades in my 30+ years working in aerospace. I worked for a aerospace material manufacture for 16 of those years where we had to test tensiles, compressions, flexes, and sandwich test coupons both wet and dry along with chemical exposures like jet fuels, hydrolic fluids, deicers, humidity like 95% RH @160f for 30 or more days. Then static test the test coupons at temperatures from -75f all the way up to 550f.
 
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There are two explanations and both probably work together. The first and most powerful is because as the pressure in the tank drops during use, the remaining air that is under lower pressure can hold more vapor, so all or most of the vapor that condenses out when the air charge cools can evaporate and go back to vapor. So there is probably very little that remains as liquid water through the cycle (but some is still likely, if only as a few drops, or moisture spread out on the wall of the tank. This is likely with Shoebox compressors as the air charge is cooler than what we get out of faster compressors.

The second is that because when we drain the tank of all pressure, the air rapidly drops from being at (or very near) 100% saturated to very dry - only a few percent humidity or less. Once the tank gets down to 10 bar or less, even though very cool from having been vented, any remaining liquid water will evaporate very rapidly - as it was doing the whole time the tank was venting and being blown out with the air as vapor. Do note that all these pictures that we see of signs of corrosion in tanks are of dry conditions - they are never "wet" as the water has already evaporated away.

It is not at all surprising to me that the tank is dry when checked after filling with a Shoebox - although I would be more surprised if it were bone dry from lots of filling with Yong Heng type pumps and no drier in the path. What is really important is the visual inspection, not the presence of water. The concern is that the aluminum liner in the tank could corrode. If you have no signs of that then you should be good to go - that is a sign that the first mechanism is doing the job, and not that the second one. But to me, it is still worthwhile taking steps to make sure water never gets into the tank, even with a Shoebox set up that seems to work well - it is so easy to "dry" the air before after it comes out of the shop compressor, eliminating all risk going forward.
 
Well, I'll be able to see if there is any Condensation in the tank after I let it sit for a day or two. 1 of the main reasons I removed the valve is so I could remove the straw that all fireman scba valves come with to keep any liquid buildup from being sucked in to the regulator feeding the fireman's mask. I will leave it for like I said a day or two with the valve at the bottom. I'll then barely crack the valve and see if anything comes out. I know when I use to fill my liberty with my yong Heng clone the inside of my air tube use to have droplets. I can Guarantee that air tube had liquid water in it. You can tell by the green oxidation from the brass. Plus you have dissimilar metals in contact with each other which will result in electrolysis.
 
This folks is why you use dry air to fill your gun. Thank you Brian at Veradium Air for being my airgun doctor. I personally filter my compressor. This is a newly purchased used rifle. View attachment 343309View attachment 343310View attachment 343311View attachment 343312
My cheap Chinese compressor has two inline filters. One for moisture removal (mechanical) followed by a desiccant/oil capture unit. Happened by accident as I ordered two different types of in-line dryer units without understanding how they actually functioned. My air is definitely dry and clean.
 
NOOBIE ALERT
I just got my air gun a couple of weeks ago and am still facing a steep learning curve. An earlier post contained this:

"Cooler air has a lower dew point so less water will be in vapor form and more will be in liquid form that can be easily remove with a coalescer filter or cooling tower before it goes into your gun or tank."

I am not sure just what these two types of filters are but I did buy this filter on Amazon and suspect it is a cooling tower. I also have a cheap inline cotton/whatever filter that came with my compressor which may or may not be a coalescer filter. In fact there may be more than two types of filters.
In any case what I am looking for is specific advice on should I use both of my current filters at the same time or just the cooling tower filter; or are there other better options.

Any additional advice welcome.

 
Ragebot,

I'd say there are three broad categories of "filters": Coalescing (remove contaminants by getting them to stick together (coalesce) and drop of out of the airflow - works great for removing water/oil mist in air flow, especially when combined with coolers to reduce the air charge temp and drive more condensation), absorptive (uses physical media to directly capture contaminants, like the tampon type - requires the contaminants to be "big enough" to be captured, thus does not work for vaporized contaminants), and adsorptive (uses a media to adsorb contaminants directly, such as desiccant or charcoal, that capture gaseous contaminants directly).

The one you linked to is a coalesing filter, and the other probably has a filter pad making it a absortive filter. Whether or not these are enough for you depends on the situation - what compressor are you using, and how do you use it? Fill tanks then fill guns? Fill guns directly? What pressures? Different uses lead to different results with different filters likely needed (although using a desiccant filter in the system after the compressor is never a bad thing, unless you are hand pumping - then it works against you).

Let us know more . . . .
 
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Ragebot,

I'd say there are three broad categories of "filters": Coalescing (remove contaminants by getting them to stick together (coalesce) and drop of out of the airflow - works great for removing water mist in air flow, especially when combined with coolers to reduce the air charge temp and drive more condensation), absorptive (uses physical media to directly capture contaminants, like the tampon type - requires the contaminants to be "big enough" to be captured), and adsorptive (uses a media to adsorb contaminants, such as desiccant or charcoal that can capture gaseous contaminants directly).

The one you linked to is a coalesing filter, and the other probably has a filter pad making it a absortive filter. Whether or not these are enough for your situation depends on the situation - what compressor are you using, and how do you use it? Fill tanks then fill guns? Fill guns directly? What pressures? Different uses lead to different results with different filters likely needed (although using a desiccant filter in the system after the compressor is never a bad thing, unless you are hand pumping - then it works against you).

Let us know more
Two air guns so far; Hatsan .30 (250 bar) Blitz which I just got delivered and have never fired or filled and AEA Challenger Pro (up to 300 bar but maybe 260 the first time) in .357 which I have filled and taken to the range once with satisfactory results. Also have two compressors a Heng Young and a GX CS3. As I found out too late the Blitz needs a special fitting for the probe to fill and it is suppose to arrive today. Also have a Sightmark scope I used to make this vid at 25 yards. No tank yet but looking into a SCUBA tank since I have a 42 foot catamaran I cruise on in season so probably filling directly to start but that is not written in stone.

 
I live where it's supppper dry🤯 do I need the filter on my hand pump?....
Hill mk4(if anyone was one or a link to one) mine was just pump and hose👀
I stopped using my Hill pump because of moisture issues. The filter they come with is useless money grabbing garbage imo. I now use an Alkin W31, mainly because I hated pumping. It is much more fun to fill a large scba tank and use that to supply the gun from time to time or the whole time while shooting.
 
With that compressor and usage, I would want to use a desiccant filter in the path. There is lots of good info in this thread: https://www.airgunnation.com/threads/joe-b-400-00-filter-worth-the-money.1286648/

Also in that thread is a link to the one I would buy: https://nuvair.com/personal-filter-din.html

Do know that I do not use these - I have a Shoebox compressor (which I love) and I filter the air after the shop compressor but before the Shoebox does it's thing (since I have access to the air already compressed to 125 psi before it enters the unit). But if I had a Yong Heng, I would use the nuvair filter - do make sure you have a way to close it off from atmospheric air when not in use, to prolong it's life. Since you will have to get fittings for it, I would include a line that can loop back on itself and seal it off with male-female connection . . .
 
Great link with lots of good intel. One of my good friends is a big time physics guy who made stuff for an international tier lab and over the weekend helped make a stand for my setup so far. I just ordered a desiccant filter as the final step in my setup and will mod the system when it arrives. As an aside if I had to do this all over again I would probably buy one of the $US3k+ SCUBA compressors so everything was in one system and I did not have to add anything. Thx 4 the help guys.