PCP compressor Filter

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Sorry, after reading this thread I am more confused....


🅐
WHAT filter medium should be used for airgunning?
➊ silical gel beads
➋ desiccant
➌ molecular sieve
➍ activated charcoal


🅑
If I only fill up my gun's 0.5L bottle from 120 to 250bar, do I really need to fill such a huge filter every time?
The volume of the filter seems to rival my airbottle.... 🤔


Thanks for any pointers,

Matthias
 
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JungleShooter said:
Sorry, after reading this thread I am more confused....


🅐
WHAT filter medium should be used for airgunning?
➊ silical gel beads
➋ desiccant
➌ molecular sieve
➍ activated charcoal


🅑
If I only fill up my gun's 0.5L bottle from 120 to 250bar, do I really need to fill such a huge filter every time?
The volume of the filter seems to rival my airbottle.... 🤔


Thanks for any pointers,

Matthias
Click to expand...
To your first question, "A":

Both Silica Gel Beads and Molecular Sieve are desiccants - meaning they adsorb water vapor directly out of the air stream. Not in your list is zeolite that could also be used. Activated charcoal will not dry the air stream at all - it is used to absorb VOCs (volatile organic compounds) like oil and gas vapors for breathing quality air. We air gunners do not need to use activated charcoal in our filters.

As for which desiccants to use, they all have advantages and disadvantages. Make the choice that works best for you:
Silica Gel - cheap and easily rechargable via heating in pretty much any oven, and readily available in an "indicating" bead that lets you know when it needs to be recharged. But does not "dry" as deeply as Molecular Sieve - that said, I used it on its own for years (in a large enough amount) and had no issues with it (I since added a small Molecular Sieve filter after mine just in case). It will dry to an ambient pressure dew point of -45 degrees F.

Molecular Sieve - the best for drying, but is more expensive, hard to come by with indicating beads, and is basically not rechargable without a high temperature kiln (no home oven can get hot enough).

Zeolite - a lot like Silica Gel, and a good choice if you have easy access to it.

To question "B" I'd say it all gets down to how hot the air charge gets leaving your compressor. That said, I would want to use one, but I would go for something a bit smaller for your use - one of the medium sized filters could work. Most of those only come with cotton filters, but you could make your own desiccants insert for it using a bit of old "transparency" film and short filter caps to keep it separate from the metal housing to avoid corrosion.
 
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AlanMcD said:
To your first question, "A":

Both Silica Gel Beads and Molecular Sieve are desiccants - meaning they adsorb water vapor directly out of the air stream. Not in your list is zeolite that could also be used. Activated charcoal will not dry the air stream at all - it is used to absorb VOCs (volatile organic compounds) like oil and gas vapors for breathing quality air. We air gunners do not need to use activated charcoal in our filters.

As for which desiccants to use, they all have advantages and disadvantages. Make the choice that works best for you:
Silica Gel - cheap and easily rechargable via heating in pretty much any oven, and readily available in an "indicating" bead that lets you know when it needs to be recharged. But does not "dry" as deeply as Molecular Sieve - that said, I used it on its own for years (in a large enough amount) and had no issues with it (I since added a small Molecular Sieve filter after mine just in case). It will dry to an ambient pressure dew point of -45 degrees F.

Molecular Sieve - the best for drying, but is more expensive, hard to come by with indicating beads, and is basically not rechargable without a high temperature kiln (no home oven can get hot enough).

Zeolite - a lot like Silica Gel, and a good choice if you have easy access to it.

To question "B" I'd say it all gets down to how hot the air charge gets leaving your compressor. That said, I would want to use one, but I would go for something a bit smaller for your use - one of the medium sized filters could work. Most of those only come with cotton filters, but you could make your own desiccants insert for it using a bit of old "transparency" film and short filter caps to keep it separate from the metal housing to avoid corrosion.
Click to expand...


Alan, for that response I have to report you.
Report you to the board.
To your feedback board, to be specific.

Because different from most of the fluff that gets posted on forums — your answer is
• substantial,
• answered precisely my questions, and
• went beyond my questions to include things I missed.


Thank you! 🤝🏼

Matthias
 
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OK... noob here. Be gentle :) In reading above, it indicates to not quickly relieve pressure from the filter below 2000psi in order to keep the media from rapidly expanding. However, I also recall seeing that one should open the relief valve on the compressor prior to starting or stopping the pump.

Do the filter containers incorporate a check valve or operable inline valves to maintain pressure in the filter?

Also...What about putting a larger volume of desiccant media on the intake of the pump, rather than the output? This would not help oil emissions, but would get the air dry prior to compression.
 
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KS_Paperpuncher said:
OK... noob here. Be gentle :) In reading above, it indicates to not quickly relieve pressure from the filter below 2000psi in order to keep the media from rapidly expanding. However, I also recall seeing that one should open the relief valve on the compressor prior to starting or stopping the pump.

Do the filter containers incorporate a check valve or operable inline valves to maintain pressure in the filter?

Also...What about putting a larger volume of desiccant media on the intake of the pump, rather than the output? This would not help oil emissions, but would get the air dry prior to compression.
Click to expand...
Read #35 & 36 to get an understanding of why pre filtering is not efficient and not worth the effort.
https://www.airgunnation.com/threads/moisture-in-pcp-airguns.1321274/page-2#post-1839752
 
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JungleShooter said:
Sorry, after reading this thread I am more confused....


🅐
WHAT filter medium should be used for airgunning?
➊ silical gel beads
➋ desiccant
➌ molecular sieve
➍ activated charcoal


🅑
If I only fill up my gun's 0.5L bottle from 120 to 250bar, do I really need to fill such a huge filter every time?
The volume of the filter seems to rival my airbottle.... 🤔


Thanks for any pointers,

Matthias
Click to expand...
When I got my PCP compressor and was looking at filters that use desiccant I contacted Dry & Dry a supplier of silica gel beads asking bout using them in an air line that could have up to 4500 psi, here's the response I got.

<quote>
Dear Allen,

Thank you for reaching out with your question about using our silica beads in your high-pressure PCP air gun setup.

While silica gel beads are excellent for moisture removal in many settings, they are not the best choice for applications reaching 4500 psi. Under such high pressure, silica gel beads may not hold up effectively and could fragment, potentially affecting the performance of your equipment.

For high-pressure systems like yours, we recommend looking into molecular sieves or activated alumina desiccants. These materials are more durable in extreme pressure environments and are widely used for moisture control in compressed air systems.

Unfortunately, we don’t carry molecular sieves or activated alumina, so you may need to source them from another supplier.

Please feel free to reach out if there’s anything else we can assist you with.

Thank you again, and we hope this information helps.
</quote>
 
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Here is how I get it done. The two big filters stay pressurized most all the time. I check them twice a year and if the indicating beads are 1/2 or more changed color, then I change all the media. The media filter is filled about half and half with indicating Silica and molecular sieve with cotton fiber discs top, bottom and center about 1/2" each. I almost never fill a gun just my 9L tank from 220 to 310 Bar once or twice a week. I purge the HPA Pump every 5 or so minutes during fill and the Separator at the end of a fill; not long enough to loose all the pressure in the 2 filters. I open the purge valve just enough to see if there is any water present. The cotton in the small black filter seems to do most of the work! I dry that one after every fill.
Maybe this winter I'll get around to hanging PVC from the ceiling to clamp the 2 big filters to.

My HPA Setup.jpg
 
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rc4fun said:
Here is how I get it done. The two big filters stay pressurized most all the time. I check them twice a year and if the indicating beads are 1/2 or more changed color, then I change all the media. The media filter is filled about half and half with indicating Silica and molecular sieve with cotton fiber discs top, bottom and center about 1/2" each. I almost never fill a gun just my 9L tank from 220 to 310 Bar once or twice a week. I purge the HPA Pump every 5 or so minutes during fill and the Separator at the end of a fill; not long enough to loose all the pressure in the 2 filters. I open the purge valve just enough to see if there is any water present. The cotton in the small black filter seems to do most of the work! I dry that one after every fill.
Maybe this winter I'll get around to hanging PVC from the ceiling to clamp the 2 big filters to.

View attachment 520684
Click to expand...
I come with updates, as the compressor is almost here! Even though it arrives from a warehouse in Europe, the process has been... well, I guess it's time to move on.

So, couple of questions, as per usual:


1. how do the filters remain fully pressurized if they do not have a PMV attached to them? Also, like we've previously discussed before, having them under pressure at all times doesn't really matter unless you're filling from 0, correct? If the bottle has 1.5-2k PSI in it, it shouldn't be a problem.

2. unfortunately they were only able to ship me the compressor version with auto-stop, meaning it stops when the desired pressure is achieved; even though it's the more expensive version (got it at the base price, so a win I guess?) I now face another issue: if I have to open the bleed valve before the compressor is stopped, does that mean I just select the compressor to work until 3.1k PSI but check the pressure myself and just stop it when it reaches 3k while opening the valve first?
 
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I just bought one of the gold filters with the internal cartridge. Mine has desiccant, molecular sieve, and charcoal. For some reason, the manufacturer stacked the three components such that incoming air first encounters the charcoal, then the molecular sieve, and finally the desiccant. This seems backwards. Does any one know why the cartridge is stacked this way?

Thanks

JackHughs
 
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@Lynx 1. There is a one way valve instead of a PMV. Keeping the filter pressured all the time saves the compressor from having to fill them from empty every time.
2. You can turn the set point higher and open the bleed valve at the desired pressure. Or turn it back on after opening the valve, it's an abrupt stop.

@JachHughs Yep it's backwards someone had a bad day or you just have the whole thing upside-down. It should be semitrical so in & out is only the label.
 
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rc4fun said:
@Lynx 1. There is a one way valve instead of a PMV. Keeping the filter pressured all the time saves the compressor from having to fill them from empty every time.
2. You can turn the set point higher and open the bleed valve at the desired pressure. Or turn it back on after opening the valve, it's an abrupt stop.

@JachHughs Yep it's backwards someone had a bad day or you just have the whole thing upside-down. It should be semitrical so in & out is only the label.
Click to expand...
Wait, hold on... so if you have a one way valve, means the air only gets in, without getting out, correct? Damn... does that mean I could've used something like this on the compressor I showed you and still use the gold filter? Because I opted out of the big one thinking it was too much for the little guy (and I was talked into the fact that cotton would suffice for my small 0.8l bottles, especially at only 3000 PSI)
 
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