Others Pre dryer

[Alan]

Most PCP users have some sort of high-pressure pump to refill their airguns and/or portable tanks. Most have some sort of device to trap or absorb moisture in the compressed air column. Higher end units might be equipped with high pressure post filters. The former ones are very inefficient, and require regular replacement of the (treated?) filter cartridge. The latter ones have two drawbacks. The filter cartridges are expensive (≈$20 each), and you can’t tell if they’re still being effective. Further, the extra volume they contain requires pressurizing before your airgun starts to refill. Read that as extra wear and tear on the pump. But there is an alternative, and that is a pre dryer.

The photo shows one I put together. I won’t make apologies for the photo, because form always follows function! The filter housings may be purchased from Amazon https://www.amazon.com/YOEDAF-Housi...prefix=empty+filter+cartridge,aps,134&sr=8-32 for under $15 each. The half inch fittings and plastic tubing are available from Ace Hardware, Home Depot, and Lowes. The filter’s outlet hose is fed into the inlet fitting on my Hill EC-3000 compressor. But it isn’t the housings which make the filter unique, it is what’s in them!

The right one is filled with 3A Molecular Sieve material, an industrial desiccant. It too may be purchased from Amazon (https://www.amazon.com/Wisesorb-Pre...-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1 The 3A refers to the molecular size it can absorb, and in this case, water vapor. In fact type 3A Molecular Sieves will reduce water in an air stream to 0.001 mg/liter air. Read that as very effective. However, like post dryers, you can’t tell when it can no longer absorb moisture. There is solution!

The left housing is filled with Silica Gel, another industrial desiccant. In this case, the Silica Gel changes color as it nears its limit of trapping moisture. Once the blue color (there are other colors available) changes to pink, you know it is time to recharge it. And here is how that is done.

For the record, 3A Molecular Sieve material can also be recharged. Unfortunately, the necessary equipment is rather expensive and cumbersome. So it is cheaper to toss it out (it’s environmentally safe to do so). The Silica Gel, on the other hand, can be easily recharged in a microwave oven. Fill up a Mason jar full of Silica Gel, and heat for about 1.5 minutes on high power. Be careful, it will be HOT! Take it out of the microwave, and allow the remaining moisture to evaporate. Once cool, put the lid back on and save for the next recharge.

All of this “stuff” will set you back about $75 depending on the quantity of desiccant you buy. A gallon jug of 3A Molecular Sieve is about $35 (about 10 refills). The reusable Silica Gel is about $10 for a quart jar full.

The bottom line? The setup is indeed effective! I shoot about 300 rounds a week, which is about 8 refills (120 BAR back up to 250 BAR). The pre dryer has had about 10,000 rounds worth of air drawn through it, and I’ve only needed to change the 3A Molecular Sieve material once! And, the best part is, when I open the air bleed valve, no moisture is expelled!

 

[hameditor]

Great idea!!!!!

Everyone needs dry air for their PCPs and this looks a good practical way to do it.

Thanks for sharing.

 

[Madeintheuk]

I like the idea, I’ve just heard so much about the compression of air causing water vapor that would normally be non existent at atmospheric pressure. i think it wouldn’t hurt to add this to your system, but I don’t think I’d rely on it purely to remove all moisture from my compressed air. If this was the case, scuba, and scba compressors would have been using this method already.

 

[Alan]

It is true that air used for breathing is post dried, and here are some of the reasons. Breathing air must be free of contaminates, especially oils and other volatiles. The methods used to remove these contaminates are best preformed under pressure. Besides zeolites, other porous materials are used, as is activated charcoal and fritted glass filters. The latter's minute porous structure require high pressures to force the air through them, hence post drying. And calling the post-dried air dry is a bit of an oxymoron, as some moisture still remains. In fact, for some SCUBA uses, it is added along with other needed gases such as argon.

Hidden in these statements is the question... How dry (percentage wise) of contaminates, water included, do you need removed? Under pressure, zeolites also remove some oils, including silicon oil, often used as lubricant for the moving parts in a high pressure compressors. Silicon oil does not diesel like petroleum oil can, and is actually beneficial to the innards of airguns. This is one of the reasons for pre drying.

By the way, zeolites (as used for molecular sieves) are made up of hydrated metal aluminosilicate compounds, and in some forms, are found in nature. Hence, the environmentally safe label.

 

[Madeintheuk]

You’ve convinced me. I would like to see both in action. Pre and post. My water separator between my compressor and bottle does a phenomenal job, but I do see minute amounts getting past it that the cotton filter at the end of my hose picks up. It can’t hurt to pre dry first, and keep what I have in line, and see if it affects the amount of moisture I purge from my separator after the fact.

Thanks for the info. I guess I’m hitting Amazon tonight, and putting one of these together!

 

[Webbsa]

Most PCP users have some sort of high-pressure pump to refill their airguns and/or portable tanks. Most have some sort of device to trap or absorb moisture in the compressed air column. Higher end units might be equipped with high pressure post filters. The former ones are very inefficient, and require regular replacement of the (treated?) filter cartridge. The latter ones have two drawbacks. The filter cartridges are expensive (≈$20 each), and you can’t tell if they’re still being effective. Further, the extra volume they contain requires pressurizing before your airgun starts to refill. Read that as extra wear and tear on the pump. But there is an alternative, and that is a pre dryer.

View attachment 701The photo shows one I put together. I won’t make apologies for the photo, because form always follows function! The filter housings may be purchased from Amazon https://www.amazon.com/YOEDAF-Housi...prefix=empty+filter+cartridge,aps,134&sr=8-32 for under $15 each. The half inch fittings and plastic tubing are available from Ace Hardware, Home Depot, and Lowes. The filter’s outlet hose is fed into the inlet fitting on my Hill EC-3000 compressor. But it isn’t the housings which make the filter unique, it is what’s in them!

The right one is filled with 3A Molecular Sieve material, an industrial desiccant. It too may be purchased from Amazon (https://www.amazon.com/Wisesorb-Pre...-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1 The 3A refers to the molecular size it can absorb, and in this case, water vapor. In fact type 3A Molecular Sieves will reduce water in an air stream to 0.001 mg/liter air. Read that as very effective. However, like post dryers, you can’t tell when it can no longer absorb moisture. There is solution!

The left housing is filled with Silica Gel, another industrial desiccant. In this case, the Silica Gel changes color as it nears its limit of trapping moisture. Once the blue color (there are other colors available) changes to pink, you know it is time to recharge it. And here is how that is done.

For the record, 3A Molecular Sieve material can also be recharged. Unfortunately, the necessary equipment is rather expensive and cumbersome. So it is cheaper to toss it out (it’s environmentally safe to do so). The Silica Gel, on the other hand, can be easily recharged in a microwave oven. Fill up a Mason jar full of Silica Gel, and heat for about 1.5 minutes on high power. Be careful, it will be HOT! Take it out of the microwave, and allow the remaining moisture to evaporate. Once cool, put the lid back on and save for the next recharge.

All of this “stuff” will set you back about $75 depending on the quantity of desiccant you buy. A gallon jug of 3A Molecular Sieve is about $35 (about 10 refills). The reusable Silica Gel is about $10 for a quart jar full.

The bottom line? The setup is indeed effective! I shoot about 300 rounds a week, which is about 8 refills (120 BAR back up to 250 BAR). The pre dryer has had about 10,000 rounds worth of air drawn through it, and I’ve only needed to change the 3A Molecular Sieve material once! And, the best part is, when I open the air bleed valve, no moisture is expelled!

Do you think that would put a restriction on the incoming air to compressor? That would be my only concern.

 

[Webbsa]

Most PCP users have some sort of high-pressure pump to refill their airguns and/or portable tanks. Most have some sort of device to trap or absorb moisture in the compressed air column. Higher end units might be equipped with high pressure post filters. The former ones are very inefficient, and require regular replacement of the (treated?) filter cartridge. The latter ones have two drawbacks. The filter cartridges are expensive (≈$20 each), and you can’t tell if they’re still being effective. Further, the extra volume they contain requires pressurizing before your airgun starts to refill. Read that as extra wear and tear on the pump. But there is an alternative, and that is a pre dryer.

View attachment 701The photo shows one I put together. I won’t make apologies for the photo, because form always follows function! The filter housings may be purchased from Amazon https://www.amazon.com/YOEDAF-Housi...prefix=empty+filter+cartridge,aps,134&sr=8-32 for under $15 each. The half inch fittings and plastic tubing are available from Ace Hardware, Home Depot, and Lowes. The filter’s outlet hose is fed into the inlet fitting on my Hill EC-3000 compressor. But it isn’t the housings which make the filter unique, it is what’s in them!

The right one is filled with 3A Molecular Sieve material, an industrial desiccant. It too may be purchased from Amazon (https://www.amazon.com/Wisesorb-Pre...-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1 The 3A refers to the molecular size it can absorb, and in this case, water vapor. In fact type 3A Molecular Sieves will reduce water in an air stream to 0.001 mg/liter air. Read that as very effective. However, like post dryers, you can’t tell when it can no longer absorb moisture. There is solution!

The left housing is filled with Silica Gel, another industrial desiccant. In this case, the Silica Gel changes color as it nears its limit of trapping moisture. Once the blue color (there are other colors available) changes to pink, you know it is time to recharge it. And here is how that is done.

For the record, 3A Molecular Sieve material can also be recharged. Unfortunately, the necessary equipment is rather expensive and cumbersome. So it is cheaper to toss it out (it’s environmentally safe to do so). The Silica Gel, on the other hand, can be easily recharged in a microwave oven. Fill up a Mason jar full of Silica Gel, and heat for about 1.5 minutes on high power. Be careful, it will be HOT! Take it out of the microwave, and allow the remaining moisture to evaporate. Once cool, put the lid back on and save for the next recharge.

All of this “stuff” will set you back about $75 depending on the quantity of desiccant you buy. A gallon jug of 3A Molecular Sieve is about $35 (about 10 refills). The reusable Silica Gel is about $10 for a quart jar full.

The bottom line? The setup is indeed effective! I shoot about 300 rounds a week, which is about 8 refills (120 BAR back up to 250 BAR). The pre dryer has had about 10,000 rounds worth of air drawn through it, and I’ve only needed to change the 3A Molecular Sieve material once! And, the best part is, when I open the air bleed valve, no moisture is expelled!

Do you think that would put a restriction on the incoming air to compressor? That would be my only concern.

 

[Alan]

No. In fact, you can easily draw a breath through it.

 

[rcs9250]

Do you think that would put a restriction on the incoming air to compressor? That would be my only concern.

I think you have a legitimate concern. One thing you do not want to do is pull a vacuum (or reduced intake pressure). If I were to add something to the intake side I would definitely install a differential pressure gauge and make sure it was at zero while compressor ran.

 

[Alan]

My compressor is a Hill EC-3000. The inlet air filter, if you can call it that, looks and feels like a dental dam. It has more back pressure than the pre dryer.

By the way, I used this for several years on an Omega Charger, and now about three years on the Hill. No issues whatsoever ever!

 

[Webbsa]

My compressor is a Hill EC-3000. The inlet air filter, if you can call it that, looks and feels like a dental dam. It has more back pressure than the pre dryer.

By the way, I used this for several years on an Omega Charger, and now about three years on the Hill. No issues whatsoever ever!

Sounds good. Was just curious. Been looking for an idea like this

 

[oOmpH]

Pre-drying your air is the way to go.

Home made systems can definitely help but have some short comings. To really be effective an air drying system needs a pressure maintaining valve and a space for the air/pressure to build up to the point where it condensates before it goes into the filtering system. Also called, regulated condensation. Active carbon filters as a second stage, desiccant beads as 3rd stage - which needs to be tightly packed, you just can't throw them in a tube to avoid channeling - where the air will just go in between the beads - and finally a 4rd stage with some micro fiber cloth.

Thats why professional pre-drying systems are rather expensive. Guess you could also make this yourself but theres quite some science behind it.

Now, anything will help and @Alan system is very clever.

 

[Alan]

The filter housings do had defusers build into them. But even then, this is NOT a cure all! This said, it is a good alternative to post dryers which have a serious drawback—you cannot tell when the cartridge needs to be replaced! And at ≈$20 each, they're expensive too.

Activated charcoal isn't there to trap moisture, but other airborne contaminates such as oils and aromatic alcohols. Those are things you do not want in breathing air, as contaminates in air for SCBA use.

And I do have to say, too many folks are hung up on advertising hype. After all, we're not breathing PCP air! Fact is, the silicon oil used to lube some high pressure compressors will not diesel, and acts as a lubricant for other moving parts inside airguns, like valves.

 

[oOmpH]

The filter housings do had defusers build into them. But even then, this is NOT a cure all! This said, it is a good alternative to post dryers which have a serious drawback—you cannot tell when the cartridge needs to be replaced! And at ≈$20 each, they're expensive too.

Activated charcoal isn't there to trap moisture, but other airborne contaminates such as oils and aromatic alcohols. Those are things you do not want in breathing air, as contaminates in air for SCBA use.

And I do have to say, too many folks are hung up on advertising hype. After all, we're not breathing PCP air! Fact is, the silicon oil used to lube some high pressure compressors will not diesel, and acts as a lubricant for other moving parts inside airguns, like valves.

Active carbon does trap water molecules and to good effect. It only becomes less effective in high humidity hence why combo with desiccant is ideal. I don't believe companies just put this together for marketing reasons and does serves a purpose.

But again... kudos for your system.

 

[Alan]

Active carbon does trap water molecules and to good effect. It only becomes less effective in high humidity hence why combo with desiccant is ideal. I don't believe companies just put this together for marketing reasons and does serves a purpose.

But again... kudos for your system.

I don't mean to start an argument, but active charcoal is not a desiccant. Even common backing soda will absorb some moisture. Its use in high pressure filters is to absorb volatiles; oils, alcohol, and in some cases, ethers.

 

[rcs9250]

Dry charcoal will absorb moisture up to what’s called EMC, Equilibrium Moisture Content. It does not hold nearly the amount of moisture that a dessicant or molecular sieve does by volume but it does absorb moisture. Don’t believe it? Take two pieces of charcoal out of a bag. Put one in a ziplock bag and leave the other one out in the humidity for several days, then crush the two. The humidity exposed one crumbles very readily.

 

[oOmpH]

Dry charcoal will absorb moisture up to what’s called EMC, Equilibrium Moisture Content. It does not hold nearly the amount of moisture that a dessicant or molecular sieve does by volume but it does absorb moisture. Don’t believe it? Take two pieces of charcoal out of a bag. Put one in a ziplock bag and leave the other one out in the humidity for several days, then crush the two. The humidity exposed one crumbles very readily.

Right on, what i was trying to say put in good factual writing.

 

[Alan]

I think you missed my point. Even common wheat flour will absorb moisture, but using it as a desiccant would be ridiculous. Activated charcoal also absorbs moisture, but its use in high-pressure filters is not to absorb water molecules. It is there to absorb unwanted gas molecules, like esters and alcohols. In fact, common, high-pressure filter cartridges use molecular sieves (typically 3A) to absorb the moisture molecules, not specifically activated charcoal!

There is a term called moisture sorption isotherm applied to desiccants. It is their ability to hold moisture, and in all cases, their effectiveness to absorb moisture is related to temperature of the medium. We need to remember that any gas (including air) gets hot when compressed. I've yet to see any high-pressure dryer use a radiator to cool the air before drying, save for those used for SCUBA and SCBA use.

The question remains, can we absorb all of the moisture by using filters, pre or post? Obviously no! At lease not without spending literally thousands of dollars for the requite hardware. In the mean time, the pre compressed dryer is a low cost methodology for removing a decent amount of moisture.

 

[rcs9250]

Watching.

 

[AtlasAirguns]

Usually prefilters or "inlet" filters do little to nothing from what I've studied and observed over time. You will also get an thing called traveling or channeling where the air will "travel" or "channel" through the easiest passage possible around whatever medium you are trying to capture the moisture with. The best filters are the inline filters placed after condensation occurs. Also, the air on an inline filter is being forced through when it is hot, and hot air is what carries moisture to your reservoir. The issue for the prefilters is no condensing has occured and the air is still at ambient temperature. If you run another filter after the condensation occurs you should find that you are missing the majority of moisture. I don't think what you have going will hurt at all, except of course if you the air is having a hard time being pulled into the compressor but, then if it isn't, then it is likely channeling. Interesting idea though. Have you ran tests on how effective it is at capturing moisture with and without?

Just reread your post. You state that the filter reduces the moisture to "0.001 mg/liter air," what is the moisture level in a liter of air prior to your filter?

Thanks for sharing,
Atlas