N/A Moisture in PCP airguns

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Xcaliber

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Sep 7, 2024
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Whenever i had to purge the plenum to reduce the reg setting, there's always some moisture being shoot out of the bottle connector, those inline filter from compressor can't seems to keep the moisture out completely.

Do you guys purge the plenum once awhile to get rid of the built up water from the system as part of the routine maintenance? i would imagine there's going to be some corrosion in the chamber and plenum from most PCP guns after a few years right?
 
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Moisture and rust depend on a few things:

What is your relative humidity?
Do you use silicone oil every fill?
Do you have the corrosion triangle present?

Triangle: Water, Metal, Oxygen

Remove one and the effect ends. But we can't remove any of them completely, right? Then we coat or pasivate the metal so the metal surface is no longer reachable by the water or Oxygen.

Oils do that well but petroleum products can diesel causing damage.

Silicone oil does not diesel, it coats very well, it gets along with viton and rubber, it's cheap and readily available.
 
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Xcaliber said:
I keep my airguns and compressor in the basement with climate control, RH usually around 45~50% year around.

How do you use silicone oil on every fill? just drip a few drops into quick connect before running the compressor?
Click to expand...

Correct, right in the male foster, just like a foley...

TMI?
 
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Adding oil on ever refill might be a bit excessive, I'm just thinking it may end up having spoonful of oil collected in the reservoir and plenum quickly no? When high amount of oil and grease being compressed constantly at 200~250 bar, i'm not sure if they would eventually gunk up and clogging up stuff? Just thinking out loud, have no idea how it would react under high pressure. If the gun is used frequently and being refilled several times a week, maybe once a month with oil in the refill port to coat all the internal parts would suffice?

I think i'll just have to do a complete tear down on my airguns once every two years as part of the necessary maintenance to check over all the seals/o'rings and be on the lookout for corrosion.
 
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Xcaliber said:
I keep my airguns and compressor in the basement with climate control, RH usually around 45~50% year around.

How do you use silicone oil on every fill? just drip a few drops into quick connect before running the compressor?
Click to expand...
I have two compressors. In low humidity I will use my water cooled compressor in my garage with a filter.
In higher humidity, I have a slower but quieter compresser that I use in a spare bedroom wher the AC keeps the air reasonably dry and the quiet compressor does not make the wife cranky. You know, that happy wife thing?

Anyway. I have had no moisture issues in the years I have been doing the PCP thing.
 
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Xcaliber said:
Adding oil on ever refill might be a bit excessive, I'm just thinking it may end up having spoonful of oil collected in the reservoir and plenum quickly no? When high amount of oil and grease being compressed constantly at 200~250 bar, i'm not sure if they would eventually gunk up and clogging up stuff? If the gun is used frequently and being refilled several times a week, maybe once a month with oil in the refill port to coat all the internal parts would suffice?
Click to expand...

Whatever! 😊

Thin silicone oil will just be expelled. It won't flood anything. Don't use high viscosity silicone oil, use the water-thin stuff.
 
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Firewalker said:
I've quite literally inspected hundreds of gun bottles and have yet to see standing water or silicone oil in a PCP.

Pumpers and break-actions?

Flood those with silicone oil!! They are always rusty and moist. Yuck!
Click to expand...
interesting, i was expecting the other way around where pump action and break barrel would have the least amount corrosion issues. lol
 
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Regarding adding silicone oil to the fill port, I tried this approach in my first PCP but when I eventually took it apart, I could not find any evidence that the silicone oil atomizes and migrates through the system. There was a little bit just beyond the check valve on the air tube walls but everything else was bone dry as best I could tell (e.g. wiping a finger on metal surfaces and then observing the surface with light reflecting at a shallow angle).

When I want silicone on internal surfaces, I apply it directly to them. For example, for an air tube I'll wrap a piece of foam from a JSB tin around a dowel, secure it with a zip tie, apply a generous amount of silicone oil to it, and sweep it in and out of the tube.
 
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nervoustrig said:
Regarding adding silicone oil to the fill port, I tried this approach in my first PCP but when I eventually took it apart, I could not find any evidence that the silicone oil atomizes and migrates through the system. There was a little bit just beyond the check valve on the air tube walls but everything else was bone dry as best I could tell (e.g. wiping a finger on metal surfaces and then observing the surface with light reflecting at a shallow angle).

When I want silicone on internal surfaces, I apply it directly to them. For example, for an air tube I'll wrap a piece of foam from a JSB tin around a dowel, secure it with a zip tie, apply a generous amount of silicone oil to it, and sweep it in and out of the tube.
Click to expand...

so some if not most of it got expelled through normal use? if you didn't find any rust or corrosion then it was doing the job right? that would be optimal you didn't find much residue coating all over the internal parts after prolong adding them on every refill. 🥳
 
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Xcaliber said:
if you didn't find any rust or corrosion then it was doing the job right?
Click to expand...

Well, despite living in the humid southeast and using hand pumps to fill my PCPs for several years, I have never found water droplets in any of them, doing nothing more than putting a quart container of desiccant on the intake and pumping indoors. Nevertheless I like to apply silicone oil for peace of mind.

The one time I found rust was in the unpressurized region of an air tube, where a paintball tank block was inserted into the end of the tube.
 
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