Oil/water separator for 74 cu ft pcp tank

[MrWolf]

I recently acquired an Air Venturi Avenger in 25 cal along with a Yong Heng compressor. My plan is to get a 74 cu ft pcp tank. Trying to stay USA made and found one at TopGun Airguns. I am also trying to determine what is true or not concerning the water/oil separators. They have the Alpha In-Line Moisture Filter but is is $400! The claim is the moisture can generate acid and attack the metal in other separators which could result in a boom someday with the 4500 psi pressure. There are plenty of Chinese ones on Amazon ranging from inexpensive to several hundred dollars.

I do not know enough about the risks, etc to determine what is realistic and necessary. I figure after finally taking the plunge into pcp, there may be others down the road so I am trying to go the correct route upfront. Any suggestions?

Thanks and Merry Christmas.

Ron

[georgerkahn]

I recently acquired an Air Venturi Avenger in 25 cal along with a Yong Heng compressor. My plan is to get a 74 cu ft pcp tank. Trying to stay USA made and found one at TopGun Airguns. I am also trying to determine what is true or not concerning the water/oil separators. They have the Alpha In-Line Moisture Filter but is is $400! The claim is the moisture can generate acid and attack the metal in other separators which could result in a boom someday with the 4500 psi pressure. There are plenty of Chinese ones on Amazon ranging from inexpensive to several hundred dollars.

I do not know enough about the risks, etc to determine what is realistic and necessary. I figure after finally taking the plunge into pcp, there may be others down the road so I am trying to go the correct route upfront. Any suggestions?

Thanks and Merry Christmas.

Ron

I hope I understood your question to hopefully advise my solution (?) to my similar question. What I did was to locate parts list for my Nomad II compressor, and purchased an extra in-line dryer complemented with a bag of inserts for it. I needed also purchase another quick-fit connector to enable problem-fee insertion into the air line. I pasted a Brother QL 1 18" x 3 1/2" label on it, and pencil on a mark each time I use it. At the fifth use, I open it up and remove/discard the filter material, replacing with new; I blacken marked group in anticipation of starting a new one.
Similar add-ons can also be purchased from the folks who make the Hill hand-pumps, but as I have the Nomad II, I went with that brand. As humidity is quite high when/where I often fill -- it seemed like a good solution and so far... it seems to have done OK.
geo

[MrWolf]

Thanks geo, I could have been a lil clearer in what I was asking.
1)Basically are the fancy separators really needed or get one rated for 90%+ and
2) Do I need to worry about a potential bomb from the acid produced eating at the metal as the TopGun stated or is it a marketing ploy?
I don't know enough so asking our folks here.
Thanks
Ron

[MrWolf]

Bump to see if anyone knows about these oil/water separators.

[elmacgyver0]

I always see these in the high-pressure line.
I don't know anything about these yet so take what I say with a grain of salt.
Would it be possible to dry the air on the inlet (low pressure) side.
Then you wouldn't risk a high-pressure explosion?
You could make a drier out of a 5-gallon bucket and desiccant, perhaps eve cat litter.
Just a thought, perhaps dumb.

[elmacgyver0]

Obviously wouldn't do anything about oil, but is that a big problem?

[andy h]

Coltri sub do a refillable high pressure personal inline filter for about $200 using silica gel and charcoal , That will capture moisture and oil as oil typically travels as an emulsion with water.
https://nuvair.com/media/catalog/pro...op900930_1.jpg
Over here they are $150 but the shipping should be less than $50
https://www.godive.net/products/personal-air-filter/

[BLAHUT]

If you are concerned, you can look into filters for filling scuba tanks for people breathing, the compressed air ?? I use a hand pump, has the filter built in..

[MrWolf]

The TopGuns site is the one that makes reference to acid as a byproduct of the filtering process. He states:

We gaurantee our AlphaFilter is the best for the following reasons:

1). We use Molecular Sieve, (not Silica Gel); Recognized in the industry as being the “best”, it is used in almost all breathing filters and other types of high pressure filters where one needs to “scrub” the air.

Property Molecular Sieve CaO CaSO4 Montmorillonite Clay Silica Gel
Absorptive Capacity at low H2O Concentrations Excellent Excellent Good Fair Poor
Rate of Absorption Excellent Poor Good Good Good
Capacity for Water @ 77F 40% RH High High Low Medium High
Separation by Molecular Sizes Yes No No No No
Absorptive Capacity at Elevated Temperatures Excellent Good Good Poor Poor
2. Moisture separation works best at High Pressure. When filling a tank with an inline filter, ensure the filter has some kind of the proper valving mechanism to allow the pressure to build up, prior to flow through the filter. The pressure needs to be held back up inside the filter to a point, and then allowed to flow through the filter media. (That’s the reason for the gold thing on the top of our filter). It costs us more, but without the proper valving, the air and moisture basically rushes over the media at low pressures, and doesn’t get scrubbed. Also the filter media needs a “dwell time” as well as high pressure to work best. Simply running air through a cylinder with a filter element doesn’t work well, and using loose packed beads doesn’t work at all. Make sure the filter has the proper valving to allow pressure to build up before the air runs through it.

3. Filters require a place to let out the condensate. If the filter is working, it should be collecting moisture and it needs to be let out immediately. Letting the condensate sit in the filter allows the moisture to saturate the filter media, rendering it useless.

4. One can’t just pack beads in a cylinder for 2 VERY important reasons.

a) It doesn’t work because of “Channeling” : We’d all like to just make a filter that uses cheap beads packed in a cylinder, but the first issue is that without proper packing, “channeling” will occur between the media. Simply put, channeling is the situation where air just goes around the individual filter “beads” instead of being “scrubbed”. In order to work, the media need to be properly “jam packed” into the a container element, and this filter element put in a filter tube. Filter elements are manufactured to be “jam packed”. Putting the media into a tube doesn’t pack it tight enough to prevent channeling at high pressures. Replacement filter elements are inexpensive, so it isn’t an issue.

b) Most importantly SAFETY. NEVER make a high pressure filter where the filter material directly touches the cylinder walls of a high pressure filter. This is filter element 101. The moisture in filter media leaches acid, and hence must not come in direct contact with the filter tube. Acid that leaches out will eventually make it to the walls of the vessel and threads on the end-caps of the filter, weakening them, and eventually causing the high possibility of catastrophic failure. This point can’t be stressed enough.

Points A) & B) are why every high pressure filter uses media that is jam-packed into either a plastic or stainless steel sleeve. So it works, and works SAFELY!

We would rather see you use no filter at all, and ruin an airgun, that use an unsafe product, and risk the dangers of doing so.

Was hoping one of our folks has experience in this area. I sure don't. To old to risk an injury just because I am being "frugal" (cheap). Figure I have time to look as I just need a tank and filter as I now have everything else. To cold to shoot outside or go to garage to fill a tank. Thanks
Ron

[W.R.Buchanan]

OK if there is any "ACID" generated by compressing air, I have yet to see it in the nearly 50 years I've been compressing air, at home and in my shop. My solution to Air Compressor Tanks rusting out from the inside, is to use Amsoil 20-50 Racing Oil in my Shop Compressors. This oil is synthetic based and when used in the compressor pump it blows thru past the Piston Rings and coats the inside of the tank thus eliminating any possibility of Rusting thru. Been doing this for 40 years! and neither of my currently 3 compressors have rusted thru or are even close. IE: No Rusty Water comes out when I drain them.

However it appears that this Acid is generated by the filter media? My Airgun compressor came with an Inline filter which has a cylindrical piece of Cotton or some such material? like they put in your mouth at the Dentist as the Filter Media. It came with a few extras as well. I figure you are supposed to change them out occasionally?

Maybe "Racing," who is the Resident Airgun Guru has some knowledge of this phenomenon?

No one has ever mentioned anything like this here before, but if we look at some big Airgun Sites maybe something will show up.

But Ron,,, I don't think it will affect you in any way for the foreseeable future so I wouldn't worry about it.

Randy

[andy h]

The corrosion noted I have encountered during my 18 years of working with high pressure (up to 10,000 psi) air and filtration systems , I first encountered it on the early breathing air filters that only went upto 3500psi , They used a aluminium filter housing with a aluminium repackable filter cartridge inside and used charcoal and alumina filtration media , After a few years the alloy filter cartridge used to corrode badly looking like an old black powder shotgun barrel that was not cleaned enough ,Pitted through extreme corrosion due to the contact with the alumina media and the residual moisture creating corrosion spots , This can also happen with molecular sieve so now the filter cartridge tubes are made of polycarbonate as a standard to eliminate contact between any potential corrosion causing media and the filter main pressure wall.

Regarding removing moisture from the air , There should be a PMV pressure maintaining valve fitted to the outlet of the compressor to maintain at least 1500psi in the filter to efficiently remove/compress the moisture from the air in the filter but Yong Heng/Vevor etc do not have a real filtration system or a PMV so as the compressor starts it is moving and compressing air at a lower pressure not efficiently removing the moisture content until you get above about 1000 psi so fitting an extra filter in the line to your cylinder or gun as in a diving personal filter can only help.

With the filter media and air channeling you use small grain/diameter filter media not using stuff the size of peas or chunks out of the BBQ bag , Real filter media as in Molecular sieve 13x is about 1/16th in diameter and charcoal or silica gel particles are not much bigger allowing a decent packing density in the filter to remove water and oil , Remember you do not need breathing quality air so co2/co and other possible contminants do not need to be removed so fancy chemical filter media is not required.

[MrWolf]

Randy and andy h - Thanks. That is what I was looking for, real world usage. I figure with the fairly recent development of fairly inexpensive (cheap) Chinese high pressure pumps, more folks will be using them and problems will start becoming more prevalent. I am definitely putting in an inline filter but have no clue which is acceptable for my usage (non breathing air). I have seen mechanical ones that have no internal media components on Amazon such as "30Mpa High Pressure Air Filter External Water Oil Separator Filtration for Air Compressor Air Pump" for around $130. No idea if they actually work for pcp usage. I was leaning towards one of the cartridge based types until I had read about the "acid" produced which andy h has actually seen and explained. I am old enough and not Superman anymore, so spending a bit more to save a potential injury is a lot more important which is why I am being anal on this.
The reseller of the Yong Heng compressor (lifetime warranty or however long they are around) recommends AW 46 Hydraulic oil which I got. I will be getting the Amsoil 20-50 Racing Oil for my regular compressors as I lost a good tank to pin holes in the bottom of the tank (thanks Randy).
Thanks again guys for taking the time to explain this to me. Like I said I know nothing about these filters other than the cheap filters I had used on my other compressors which I was neglect in maintaining and had a failed tank. 4500 psi is lot more than my lil 100+ psi so I am being extra cautious. Happy New Year!
Ron

[andy h]

If you are looking at flters I would go for the diving one's as they have been designed and tested to work at the advertised pressures, Some of the aliexpress/amazon chinese filters have way to short thread length's and thin wall's together with the end seal's being in the wrong place allowing the air at pressure to act directly on the filter wall's where the thread's are machined , The threads should only really be subject to a mechanical force pushing the end plug out but with the seal in the wrong place you also get a radial force from the 300 bar (4350psi), air pushing the thin thread machined wall's outwards and that can result in the end plug blowing out at pressure and the only way to prevent this is by making the filter with thicker wall's but that mean's more metal usage and cost to the manufacturer.

The pressurised area should be between both of the end seal's with no thread's machined between them to cause a weakened area of the pressure bearing area , Do a search and you will find account's with pictures of these filter's that have had a catastrophic pressure burst .

Modern filtation filter shell's have a wall thickness coming up to 3/4" of an inch and not the 5/16" - 3/8" of these chinese filter's ,The 3/8" wall thickness is just useable with the seals in the correct place and with long enough threads with a small volume filter.

[dverna]

Ron,

This is a good thread.

It prompted a call to the dive shop I use to fill my tank. I assumed it would be dry air but wanted to be sure. Sure enough, they confirmed the air is dry.

The information from andy h is extremely valuable......thank you sir for posting.

I was looking at getting a pump but have decided it is not worth it. $300+ for a "cheap" pump and another $400 for a "good" filter. Then add in $50 for each replacement cartridge. If the cartridge lasts 10 fills that is $5/fill for filter cost. I get my tank filled for $15 so it works out to a saving $10/fill. Driving to the dive shop is 165 mile round trip, but we go to the area a half dozen times a year to shop so not really a special trip unless I screw up and not monitor the tank. It will take a long time to recoup $700.

I only have .177 and .22 air guns with small tubes and get about 200 fills per 75 cu ft tank. If I had larger caliber air guns using more air the savings would be higher. 200 fills is about 4000 shots with the .22's and over 8000 with the .177 target pistols I have.

I am with Ron on this. These things become bombs if they fail. Not a wise place to save a few dollars.

[W.R.Buchanan]

Don: I looked at tanks but they were way more than the little compressor I bought. I had no idea that you got 200 fills per charge. I can get tanks filled at a friends shop that sells Airsoft Guns and is 15 min away from me. But a tank that can handle 4300psi is not cheap and and well above the cost of that little compressor. As far as these things rotting out and blowing up I prefer to remain skeptical on that. If that did occur it seems like it would be a situation where the usage was so high that it would be well beyond what any of us could ever do. Point being I ain't worried about it.


Randy.

[dverna]

Randy,
Airguns of Arizona has a tank fill calculator. I cannot post the link from my iPad...too stupid. Just do a search.

Like most things related to our addiction, one solution is not the best for everyone. I prefer a tank and no regrets going that route. I have the tank tethered to to gun as most of my shooting is off the bench. I am investing in an external pressure regulator so I can shoot without having to stop to refill. Using an external regulator will also provide a consistent pressure for each shot.

[elmacgyver0]

I fill my guns in my basement where I run 2 dehumidifiers.
I use a hand pump; I need the exercise anyway.
From any videos I have watched, the compressors seem to last only about a year no matter how much you pay for them.
Of course, I guess it is how much you use them.
For me they might last my lifetime.

[Racing]

Thx Randy.
Sry for being a tad late to the party, but here goes.

Rant on in short!


This acid pitch.. Listen, there´s something way more concerning to it than that - if ever. That is NOT saying that the acidic action is to be taken lightly however!

To those that might not know, i´m a rather nished engineer (aeronautic engineer as it´s called). That is NOT saying i´m some kind of know it all, it´s just me stating that i spent a number of years studying stuff like this at a university level.


One of the major drawbacks of "yellow" metals as well as aluminium (and most of it´s mixes) is what´s known as work hardening.
This we can these days within limits use what´s known as FEM analysis to look at (from a numerical point of view) and as far as i´m concerned way way way to few PCP gunners check the man´s date on their bottles for instance. Thus life span of details like this is often regarded in "cycles".

As we anodize aluminium it, within reason, changes properties. Normally anodizing aluminium will hand as a stronger surface layer which can be of use for certain/many applications.

Enter chinese made parts.
Full disclosure here.. I do not in any way or form regard chinese made parts with some sort of "rule it all" ills or as being inherently bad. What i DO know though is that they will "shortcut" at the wink of an eye if let to, and will do so willingly.

Cause see, apart from that there work hardening above when we set a given design into production we also reference what tools to be used and so forth, down to nomers like "Ra" for surface finish and what not.
Yep.
I´ve seen pics of a ripped open such gold colored filter too, of course i have, but i very strongly doubt this failure to be a matter of any "acid" attacking the material.
No. I have not gotten to take a closer look at the actual ripped/torn areas of said filter. Such pics can tell LOADS of why the thing failed AND how - albeit not to be 100 conclusive from a photo or two over the internet.

More than likely what happened to that filter was one of two possibles. Without having seen pictures of the actual "tear" i bet that such pics will show some sort of stress raiser-s, in one way or another.

Plz be adviced that the pressures we´re dealing with here is NOT "like the shop compressor". Far from it. Pressure already at the levels we´re talking here both can and will kill you if you let it...

QC for chinese made aluminium products is all over the map, to be candid. Stress in turn can very well "kill" aluminium (especially so cast or pressure cast) in a heartbeat with said stress raiser, or voids or whatever along those lines.

True is that acids present will deteriorate materials, no matter if rust or oxidation, but then please also be adviced that parts like a pressure vessel is designed and made with what´s known as a "safety factor", in plain english. In short as they´re NOT to fail (like happend) parts like these are ALWAYS "over engineered".

Can/is water moisture be an issue with aluminium?
You bet! But certainly not in a heartbeat, which is my point here. Can/is acidic particles be a part of what we´re talking here? Sure, as it´s present basically no matter what.
That´s however NOT saying in a concentration or at a level where it becomes an issue for the life span of said part.

As some of you are aware i even weld up my own tanks, and then out of steel. Have i made plenums and what have you out of aluminium? Sure.. but then out of guaranteed European made aluminium. Often times either 7075T651 speced or Alumec or similar (in short the higher end stuff). What´s more, yes i know very well how to run a lathe or how to swing a TIG welder, thank you very much.
Can this be calculated for/on? Sure. From an engineering standpoint as far as absolute values it´s even so simple i wouldn´t be surprised if there´s online calculators available on the matter. (No, i have not checked.. LOL)

FEM/numerical stress analysis though.. another matter. In short taking life span into account. Be adviced that a part that is designed to perform over 10 million cycles is considered to have "eternal life".

So. Without going into absolute detail on the matter ( apart from my rather generic standpoint per above) let the following guide you...
For these parts, as well as the tanks/tube-s on your gun, if you check closely and see even the smallest nick, the smallest irregularity... replace. Replace right now.
Do NOT put pressure to that part ever again. Just scrap it, as in bin time. Right now. Ditto for threads of said parts. Be REAL anal about this, it might save yours or someone elses life. Slam it with a sledge hammer if you wish, to be certain NOONE will ever attempt reusing the part in case.

Fact is that i´m kind of flabbergasted by with which "whatever" attitude this is handled by the PCP industry. Them generic Chinese made replacement parts with their markings...
However. It´s rare that a given such vessel will show problems, as new, at a given static pressure. The largest strain comes from going either up or down in pressure. (In contrast to o-rings which can basically fail.. cause it´s tuesday)

Next time you fill your PCP up try something as simple as just taking a "temp reading" with your hand. These differences in temps and pressure will "age" the material, and when designed AND manufactured correctly this is taken into account. Parts inherent are designed to take this, within given realms. Safety factor, as mentioned above.

In short, make it a habit to check condition of your compressor and/or scuba fittings. When threads get hurt or injured, bin time. Do NOT play around with this or shrug at it. Check the pressure hose and its fittings. If kinked, replace.
For filters, if threads look the LEAST off, replace. Stress raisers, visible such, replace. Be VERY mindful about the dates imprinted on the bottle or tank. If even close to EOL (end of life) replace.

We had an incident on behalf of Kral over here a few yrs back where some idiot claims it was a production flaw that made the bottle on his Kral Puncher go boom.
Kral importer had to basically redo his entire garage (where he kept the compressor). My take? Bull leftovers. This was yet another idiot that didn´t adhere to that it says "200 bar max fill pressure" on the bottle. I can about guarantee it was.. Passing them 200 by any appreciable amount on a repeated basis.. Do YOU know how much that reduces said life span? If not, stick to LESS than them 200 is my pro advice.

On that note?
NEVER EVER trust them "Mickey Mouse" gauges on your rifles, no i do not CARE if you own the most expensive Daystate whatever there is!
NEVER.
Often times the gauge on your scuba tank WILL be referenced and if it´s not ask the ppl at your local divers store to do so. Have at least ONE gauge around that´s been referenced/calibrated when playing around with PCP´s. Calibration runs out in turn.. so remember to redo that on a period basis.

Be adviced that them "Mickey Mouse" gauges that are on our guns are thought to be a very crude estimate AT BEST. I´ve had a Hatsan in the door that told 220 bar when the pressure IRL was 140. I´ve had an Artemis telling 150 when IRL we saw approx 180.
The stock FX gauge on my one Impact shows approx 300 bar when in practice approx 260.
NEVER EVER trust one of them "mini" whatever gauges. Have ONE gauge that is referenced/calibrated.. it is VERY cheap insurance my friends!

As for getting all the moisture out of the compressed air, well.. a topic for another day maybe but be adviced that moisture for a PCP gun won´t really kill anything, maybe apart from performance.
"Oh my compressor carries filters X and Y and is guaranteed to..." Yeah. Whatever.
I recap. Not even at the scuba centers do we see completely "dry" air from a tech point of view, so what i´m saying is.. do what you can within reason but for your own sake.. try n keep it real.

Most that shoot PCP´s sooner or later get to the point where an o-ring will fail. You´ve heard me comment on this before. Well. As far as i see it if you ain´t all thumbs it might be a good idea to get acquainted with how your gun is put together and how to pick it apart.
Not only to remedy that blown out o-ring but to be able to visually inspect the innards of your gun, and... well.. even clean it out!

I bet that sooner or later this becomes second nature and all of a sudden you´re at the point where you will tear your PCP to pieces on a "service schedule".
At that point in time, good for you.

When it comes to this *rap lads, keep it safe. No matter what, always err on the safe side.

[MrWolf]

Thanks folks. I have learned quite a bit from the various discussions. Seems opinions vary but the issue of inspecting parts and failures is a very real concern at these pressures. Was just telling my gf today on something totally unrelated that I should not have gone the cheaper route as the unit is not working as it should all the time. That unit failing will not hurt me, but at 4500 psi a failure COULD. The odds are probably low that anything will happen but I am to old and already broken. I have also read not to trust the gages and to get a good one. There are times it would be nice not being so rural that I could get a tank filled (not many in these mountains) or have possibly gone the nitrogen route but they are not a quick drive for me as I can't drive long distances yet (they burned the Left side nerves above and below my surgery today - err yesterday morning. In a bit of pain from a gotcha when he was doing it but almost to where I can sleep).
I am glad that there are varying opinions on this. Gives a good perspective. Thanks and always appreciate info.
Ron

[W.R.Buchanan]

Racing: I just read and understood every word of your post. Once I got the hang of your dialect I was good to go. Thanks for the info!

Randy Not to be cornfused with your "Randy Andy" over there!