Intake filter on compressor, is it worth it?

[ImpactX]

I see on YouTube guys are using plastic bottle fill with drydry beads and a hose connected to the intake of their compressor. Air venturi also sell one pre made for $130. I have a hill mk3 hand pump that came with a dry filter and just use that connect a hose from the intake on the compressor. I can't tell a difference cause when bleeding there will always be moisture and oil coming out when bleed. Anyone have test or theories about using an intake filter. Does it work and it is worth it? In my opinion intake filter is just trash. It is the output filter that is more important to keep moisture and oil out of our guns and tank. Heat and condensation will always create moisture inside the compressor no matter how dry the air going into it is. That is just my thought.

 

[Brent]

I think you are right drying efforts are better served on the compressed pressure side of the unit. My thoughts are restrictions in the intake side trying to pre-filter just adds load stress on the unit with not much benefit of actual drying. 

 

[dc8cappie]

In Florida any Moisture removal is good. I have a desiccant water filter on the intake and need to dry desiccant after two or three 88cu tank refills. Water out of the gun is better then in.

 

[john8]

I'm not concerned about the moisture content of the air on the input side. What concerns me is the intake of particle matter that can cause premature compressor failure. On my AV 4500 I plumbed in a cheap tuxing filter using the fiber core. I drilled a series of 1/4" holes for the intake side so that I don't restrict the air intake, then plumbed an air line to the compressor.

 

[dizzums]

not if you run it indoors .. if i was running it outside in the summer 90% humidity i probably would want one but no plans to do that ...

 

[douger]

any filter is better than none 

 

[Peashooter]

Out on a limb here but ill say a particle filter yes, in regard to moisture, that i agree should be better fought on the output side of things.

Even if some form of drying of air on the intake probably help too, but i think ( never owned a compressor ) that the proper equipment on the output side are able to take care of moisture.

 

[TN_Yankee]

Yes, drying on the output (i.e. high pressure) side is much more effective than drying on the input. Cool air, and high pressure air, can hold less moisture than warm, and low pressure air. Warm air can keep more water vapor molecules suspended, because the air molecules themselves are bouncing around more than when cool. High pressure/compressed air has less space available between the air molecules to hold water vapor molecules.

Time is another factor. The longer air containing water vapor molecules can remain in contact with desiccant, the more moisture can be removed.

Having said that, you do have to pay more attention when drying on the output, as fittings & containers need to be rated at more than the expected pressure level (for safety). Fittings & containers on the input side can be about anything.

Many do find that using desiccant on the input makes a noticeable difference, and as @douger said above, any filtering is better than none. However, for most users, atmospheric pressure air compressed to upwards of 4500psi/310 bar is going to be fully saturated, no matter how dry it was to start with, simply because it's being squeezed into 1/310th the space (standard atmospheric pressure is 14.7psi or about 1 bar). So, while that high pressure air can't hold as much moisture as lower pressure air, it's also hot due to being compressed, so that increases its moisture capacity.

So, compress your air (use desiccant on the intake if you want), then cool it quickly & let it spend a little time traveling through desiccant on its way out. Add a large coalescing filter before the output desiccant if you're in a more humid environment. They don't have a filtering medium to replace, so that helps offset their higher cost, plus they'll help your desiccant last longer.

Some good threads on this topic: https://www.gatewaytoairguns.org/GTA/index.php?topic=139845.msg1407834#msg1407834, and https://www.gatewaytoairguns.org/GTA/index.php?topic=140456.msg1416031#msg1416031.

That Air Venturi filter in the original post is a serious rip-off. 1) Being open to the atmosphere, it won't take long to saturate, 2) silica gel is more effective than molecular sieve at moderate & higher humidity levels (i.e. what you have in your house), and 3) it isn't built well enough to repurpose it for use on the high pressure output.

 

[davelarson]

Isn’t the moisture happening inside of the compressor as the air is being compressed? Or inside the hand pump/air tube as it’s working to fill the reservoir? Seems like the filter on the intake is a moot point, you are pulling air through the desiccant, and making moisture inside the compressor. At least that’s how I understand it.

My first gun was a marauder filled with a hand pump. I was shooting a LOT and it was winter, I would fill the gun, and shoot out the window over and over. I was blown away by the accuracy of a airgun and couldn’t put it down lol! I remember noticing a tiny bit of moisture on the foster fitting when I would bleed the pump. 
Then I decided to try an after market barrel and sent the gun to a guy who was going to tune the gun and put on the new barrel. Long story short was the air tube was rusty and damaged from moisture. He sent me pictures of it, and it was really bad. I was topping off the gun in the warm house, and sticking out the window into zero degrees over and over for thousands of shots ( like you do when you get a airgun for the first time ).

The gun was filled no other way so all the moisture came from hand pumping. I now use a compressor and am always amazed by how much moisture comes out when I bleed as the bottle is filling.

 

[cwcarrera]

Living in Florida humidity is a constant concern when filling my SCBA bottle. I always use my compressor in the garage to avoid making the inside of the house stink from the purged water / oil mix that is unavoidable. My garage can typically be anywhere from 70 to 85% RH in the summer so I was looking for some way to reduce the moisture that the compressor is taking in. What I came up with is running a (relatively) high capacity de-humidifier and feeding the output into the input of the compressor. I start up the de-humidifier about 30 minutes before I want to run the compressor and with a 75% RH in my garage I typically have a less than 30% RH coming out of the de-humidifier that is fed into the compressor. The Hatsan Lightning has pretty good moisture removal and automatic purge as standard equipment and I also have an additional molecular sieve as final filtration on the output. I have never seen any evidence of moisture in any of my airguns when I have done service work on them. As they say, a picture is worth a thousand words...

 

[TN_Yankee]

That's a unique idea - I've never seen that before!

 

[Fglass]

Looks like I need to buy another dehumidifier. Thanks for sharing. 

 

[cwcarrera]

Looks like I need to buy another dehumidifier. Thanks for sharing.

I had to replace mine a couple of months ago and bought this one... https://www.homedepot.com/p/Frigidaire-High-Humidity-50-Pint-Capacity-Dehumidifier-FFAD5033W1/312546305

I have been very happy with the performance and it was very well rated in all the reviews I read.

 

[Ezana4CE]

Living in Florida humidity is a constant concern when filling my SCBA bottle. I always use my compressor in the garage to avoid making the inside of the house stink from the purged water / oil mix that is unavoidable. My garage can typically be anywhere from 70 to 85% RH in the summer so I was looking for some way to reduce the moisture that the compressor is taking in. What I came up with is running a (relatively) high capacity de-humidifier and feeding the output into the input of the compressor. I start up the de-humidifier about 30 minutes before I want to run the compressor and with a 75% RH in my garage I typically have a less than 30% RH coming out of the de-humidifier that is fed into the compressor. The Hatsan Lightning has pretty good moisture removal and automatic purge as standard equipment and I also have an additional molecular sieve as final filtration on the output. I have never seen any evidence of moisture in any of my airguns when I have done service work on them. As they say, a picture is worth a thousand words...

@cwcarrera I like this idea. I don’t think I’ve seen this done before. How exactly did you manage to capture and redirect the dehumidified air into the tube? Does this dehumidifier come equipped to do this? 

 

[cwcarrera]

The dehumidifier has two outlets, one on each side. The black box on the side of the dehumidifier is a metal bread pan that is velcro'd to one of the outlets. I have a piece of PVC attached to the bread pan that the hose is connected to and that sends the dehumidified air directly into the input of the air filter housing on stage 1 of the compressor. My new dehumidifier has a single output on the top of the cabinet and I am just using a small bungie cord to hold the bread pan in place on that setup.

 

[Ezana4CE]

@cwcarrera I wouldn’t have guessed that was a bread pan. Thanks for the response. I’m not sure how much funneling the dehumidifier air in that fashion will help to reduce condensation upon compression, but living in a humid region I see the benefit of running a dehumidifier. Have you had any success reducing the RH in the entire garage by running the dehumidifier as you normally would? If so, does that tend to saturate your intake any filter faster?

 

[cwcarrera]

I have a 3 car garage and have found that running the dehumidifier non-stop for days on end will not bring the RH in the entire garage down below about 50%. And of course if you open a door at any time to take a car out or in, any headway in reducing humidity is lost. If I check the RH coming directly out of the dehumidifier after about 30 minutes of run time my hygrometer typically shows <30% RH. Thus the reason for capturing that 'dry' air and funneling it directly to the compressor input rather than trying to dry out the entire garage (which will never happen in Florida). The intake filter on my compressor is not a moisture filter, just a pleated paper particulate filter.

 

[Ezana4CE]

@cwcarrera Understood. Thanks for the clarification. 

 

[cwcarrera]

Hey Dave, BTW, my dog is prettier than yours! And sometimes she winks at me! Emmie is her name, she is a sweetie.

Chip

 

[Ezana4CE]

Hey Dave, BTW, my dog is prettier than yours! And sometimes she winks at me! Emmie is her name, she is a sweetie.

Chip

Sometimes pretty women wink at me so I have no qualms about your dog winking at you. 


Ok I’m lying….. a little. They aren’t always pretty. Mostly just old …., but they are ladies. Human ladies. So there’s that. Lol.