Moisture and rust in the air tube.

[joel w]

So a few weeks ago I had a big leak at the o-ring on the fill adapter assembly. I took it apart and see that rust had formed inside the tube and was actually pushing the oring and deforming it... I can see some slight pitting in the tube, but since I have had some bad experiences with high pressure (not with PCP airguns) in the past I am a little "gunshy" about using a rusty tube.  I also had rust starting to deform the orings around the front guage block oring.   

Anyways I ordered a new tube for $40 and replaced it yesterday. I took it all apart, I cleaned it all up buffed the aluminum bits that were also oxidizing and replaced all the orings.  It's super clean and all silicone greased up, all reassembled and no leaks. Yay...

So now, I have read all the posts here on trying to remove moisture from hand pumping but they were mostly* older posts (2011 ish).  Just wondering if anyone has found a better way over the last few years to keep the moisture out of these guns while using the hand pump or is it time to "bite the bullet" and buy a tank and shoebox?   I have seen lots of desiccant water filters and water traps but do any of them really work?. 

Edit: To explain more and be fair... I believe the rust was started from a small embedded speck of iron (probably from a grinder wheel) in the leading edge of the aluminum depinger I fabricated when I first got my Mrod.  It's my fault, not Crosmans...

Thanks Joel

[nervoustrigger]

Hi Joel,

I made one based on fellow GTA member ten.ring's concept and wrote it up into a little PDF.  If you are interested, grab a copy from my Dropbox folder.

I don't think you can realistically expect to ever get bone-dry air unless you could somehow store a sufficient volume of air and let it dwell with a healthy volume of desiccant for a length of time.  Some will say get SCUBA air from a shop but if you don't have the money for a tank or a fill shop within reasonable driving distance, that's little consolation.

I've seen little inline desiccant driers about the size of a D-cell battery and unfortunately they don't have much chance of drawing moisture out of the air.  They are just too small and the air molecules don't rub elbows with enough desiccant on the way through to do a proper job.  Also, the volume of desiccant is so little that even if it were effective, it would saturate with moisture so quickly that you'd need to bake it in the oven to dry it out after just a few uses.

Even with a liter of desiccant, I still found a small amount of condensation in my air tube after 3 months of shooting.  Well, shooting a lot and therefore I was pumping a lot.  But luckily there was not the slightest hint of rust or even discoloration so I dried it out and applied a thin coating of silicone oil to the inside of the tube before reassembling.  Admittedly, it had been filled a handful of times before I made the drier so I don't know how much that contributed. 

Another thing, I live in an area with extremely high humidity so I make an effort to do all of my filling indoors where the air is a bit drier from the air conditioner.

I hope this helps.

[edit]spelling[/edit]

[Frank in Fairfield]

So a few weeks ago I had a big leak at the o-ring on the fill adapter assembly. I took it apart and see that rust had formed inside the tube and was actually pushing the oring and deforming it... I can see some slight pitting in the tube, but since I have had some bad experiences with high pressure (not with PCP airguns) in the past I am a little "gunshy" about using a rusty tube.  I also had rust starting to deform the orings around the front guage block oring.   

Anyways I ordered a new tube for $40 and replaced it yesterday. I took it all apart, I cleaned it all up buffed the aluminum bits that were also oxidizing and replaced all the orings.  It's super clean and all silicone greased up, all reassembled and no leaks. Yay...

So now, I have read all the posts here on trying to remove moisture from hand pumping but they were mostly* older posts (2011 ish).  Just wondering if anyone has found a better way over the last few years to keep the moisture out of these guns while using the hand pump or is it time to "bite the bullet" and buy a tank and shoebox?   I have seen lots of desiccant water filters and water traps but do any of them really work?. 

Edit: To explain more and be fair... I believe the rust was started from a small embedded speck of iron (probably from a grinder wheel) in the leading edge of the aluminum depinger I fabricated when I first got my Mrod.  It's my fault, not Crosmans...

Thanks Joel

Joel, I have a question:
Did your new air tube have a new serial number on it? The Marauder serial number is there on new rifles. I was just wondering...

[joel w]

Thanks Jason for the PDF and the advice..

Frank, Yes the new tube does have a 9 digit number and the safety warning. 

[pyroboy33]

I was actually just going to start a topic about this but I see you beat me to it  . So here's my story: In a couple weeks I am going to purchase a Cricket which is a fairly nice chunk of change. So in my preparation for it I rebuilt my faithful benji hand pump and remembered how with my 4 other PCP's I had owned I never disassembled the airtubes in any of them but with the Air Venturi adapter for my old rainstorm I had noticed small droplets of water on it after filling the gun. That tells me that there is probably a small amount of moisture entering the airtubes. Needless to say there was no way in heck that I would want to convert a $1600 PCP into a $1600 water gun  . So after searching around on the forums I saw some pictures of hand pumps with small desiccant  filters on them similar to the hill pump. So I took a trip to Lowes and for about $20 bucks I got a air dryer and the necessary fittings. Nervous Trigger does have a point that these small filters aren't perfect but I know that it will be a upgrade from the pumps previous state. Also in my defense I do live in a pretty dry and arid area (around 10% humidity) so I think the filter will work out pretty well. I havent used it yet as I don't have my new gun, but I will try to report back here once I do. Here are some pics:



Let me know any questions comments or concerns y'all have.
                           Cheers
                                       -Caleb C.

[Frank in Fairfield]

Thanks Jason for the PDF and the advice..

Frank, Yes the new tube does have a 9 digit number and the safety warning.

ok

[Frank in Fairfield]

I was actually just going to start a topic about this but I see you beat me to it  . So here's my story: In a couple weeks I am going to purchase a Cricket which is a fairly nice chunk of change. So in my preparation for it I rebuilt my faithful benji hand pump and remembered how with my 4 other PCP's I had owned I never disassembled the airtubes in any of them but with the Air Venturi adapter for my old rainstorm I had noticed small droplets of water on it after filling the gun. That tells me that there is probably a small amount of moisture entering the airtubes. Needless to say there was no way in heck that I would want to convert a $1600 PCP into a $1600 water gun  . So after searching around on the forums I saw some pictures of hand pumps with small desiccant  filters on them similar to the hill pump. So I took a trip to Lowes and for about $20 bucks I got a air dryer and the necessary fittings. Nervous Trigger does have a point that these small filters aren't perfect but I know that it will be a upgrade from the pumps previous state. Also in my defense I do live in a pretty dry and arid area (around 10% humidity) so I think the filter will work out pretty well. I havent used it yet as I don't have my new gun, but I will try to report back here once I do. Here are some pics:



Let me know any questions comments or concerns y'all have.
                           Cheers
                                       -Caleb C.

I have a 4500psi tank but keep my Benji nearby. I would like to put the filter on. Caleb, do you have part numbers at Lowe's?

[joel w]

It is 36% humidity here today and almost 90 degrees. I am guilty of shooting on rainy days here from a covered shelter but hey, this is the Seattle area so if I was going to wait for sunny days, it might be a long time before I could shoot.. 

Since I already have a gas regulator for 5ft tanks, I am thinking of getting a few nitrogen tanks and be done with it. No moisture there...

[Ribbonstone]

If you can swing a Nitrogen fill system and have a local supplier, would certainly be the best way to be sure of a dry fill.

[joel w]

Cool.  Seems like a cheaper route than the shoebox and I might then still have moisture issues at that  from what I have read.

I am thinking even if the tank runs down to under 2k, I can still use it and top the gun off with the pump since I think (as I understand it) the nitrogen should help pull some moisture out with it. 

[Ribbonstone]

You can research it in your area and see if it's an option.  Lots of discussions on it in the past, dug this old one up from the OLD GTA:
http://www.gatewaytoairguns.com/airguns/index.php?topic=20853.0

[joel w]

Ohhh. Old Archives?  Some how I have missed those, got some more reading to do...Thank you sir..

[Frank in Fairfield]

Bought the filter today at Lowe's.
They didn't have the step-down adaptor.
Went to OSH (soon they will be Lowe's).
A little plumber's tape, Voila.
I have 4500psi Carbon Fiber tank but the Benji pump is always nearby.
Thanks for the idea, Jason...

[Bullit]

One of the downfalls to High pressure air powered air guns.  Only with high cost drier system, can you get dry air.  Dive shops spend money to provide you good dry air.  Hand pumps can't be fixed with those small screw in dessicant chambers...but they do help...if you maintain them properly.  Still doesn't help your rifle that's gonna eventually get moisture problems.  HPAC=Steam damage.  I wish I could offer one...I'd be rich.   But it would be so expensive, that it probably wouldn't sell.   Look into Parker-Hannifin air handling for building a drier system, or just get a tank and bite the bullet.

[joel w]

so apparently my regulator that I have is not rated to 4500 -6000 psi. And they absolutely will not rent a tank without the correct regulator. 
so I went with the regular 5 foot tank and I plan on feeding my pump 50 psi with that. 

12 or 15 pumps dry nitrogen compared to 50 pumps with  wet air...Seems to be a no brainer.

[daveb50]

Would it be possible to use CorrosinX in the air tube and other components, or would it not be compatiable with high pressure air? On the electric RC forum we use it to waterproof electrical components, such as radio receivers and servo motors. They are submerged in CorrosionX,  then drained and let dry a day before using. I have used it and it works excellent for that purpose.

[GarthThomas]

I sort of smeared silicone grease inside my tube, just a thin layer but it was visible before assembly.

[joel w]

Dave, I don't know one way or the other on that product, hopefully someone will chime in.

 I also silicone greased everything just encase because I was blown away at how much moisture was inside mine after only a few months of use. For the cost of a $50 regulator, $9 month nitrogen tank rental(will be buying a tank), $10 fill, some misc low pressure fittings and never having to worry about moisture, rust or oxidation again is well worth it IMO.  Also supplying low pressure to the pump will let me use every last bit of nitrogen in the tank and keep moisture out of the pump to boot.