How to Choose the Right Filter for Your Application
Aug. 25, 2025
How to Choose the Right Filter for Your Application
Paint booth and filtration for air lines, help | Page 2
Aftercoolers and intercoolers are different animals. Intercoolers are between the pump outlet and the tank and always have their own pressure relief valve on them for a two-stage compressor pump. Look at the fin tubes or cast pipes feeding the cylinders--they likely have relief valves too for a good reason. Aftercoolers are somewhere in the piping external to the air receiver tank.
Intercoolers between the second stage cylinder outlet and the tank are "problem children"...........subject to fatigue and stress corrosion cracking in use. Nature of the service and metallurgy for dissimilar copper tubing/aluminum fin brazing making them cheaply helps contribute to this. All copper fin is way, way too expensive for such a use. Automotive transmission type coolers are not designed for compressed air service or pressurized cycling on and off of the compressor pump they are attached to. Don't be fooled by a pressure rating on one made of aluminum alone. That often kills these things prematurely. Blow one of the return bends out in operation--watch-out you are likely on the uphill side of the pressure cut-off switch for regulating the tank being at or below 175psi. Especially if you forget to turn the electrical switch off at night or leave it on all the time and go out for a while. All your manufacturer's warranties for a new compressor will be voided doing so. Likely--your insurance policy as well if there is a problem.
Contrary to what many end-users think--the secondary design purpose of the air tank is to create a moisture condensing reservoir in these small sized air tanks. The primary purpose is to create an air mass energy supply that can be withdrawn at a desired rate constantly--10 cfm or so for an RP type gun that does not vary as a typical use example. Preferably, all the moisture condensate should be in the air tank alone and drained off at least daily before going home. That's how every air compressor manufacturer of these small compressors intends their equipment be used. But that's not likely to happen if you have a theoretical 5-7 minute window at most for drawing down your tank from 175psi to 90psi and adding more in the mix as the compressor kicks in to replenish that withdrawn for paint spraying. I use automatic drains and I am glad I do but they are overkill for home use.
Chris Hamilton's post shows an engineered system for the piping that has been in a lot of publications for small sized commercial compressors and light manufacturing, body-shops, etc..... It is very successful and dates back decades when all industrial compressors were horizontal tanks in the 's as shown in the picture were standard practice. It is standard engineering text-book stuff for fluid mechanics, etc.....In , it is still a good first choice for someone at home setting up or a small business from 5 to 7.5HP, 80 gallon, 175psi, 15-25 cfm pump output set-up. It is already engineered for you. No liability for design for you, any employees with OSHA hazard mitigation concerns go away if in a commercial application and consistent with an institutional code for such using the materials below. Your insurance agent could never balk about you installing that or using it--provided the pressure relief valve on your tank protects the piping. Other things I see on this forum about pressure piping........not so much so and uses of copper. Providing three vertical drop legs paths for the second round of condensate from cooling air in the pipe to fall out into and drain off is very good.
In the air distribution pipe--you will never be any better than the ambient temperature and that relative humidity wherever you are working unless you refrigerate. Dessicant is mostly ineffective because of the time exposure of the air flow to strip it out of the moving air mass for many climates. You will get some moisture out but not much in a moving air stream--not enough time. Good for gun safes, and static air spaces. For a very dry hot or cold climate or dry and high elevation users maybe enough alone in some locations and seldom use.
For "aftercooler coils"--best to have drain taps or use compressed nitrogen or heavy argon to force out condensate lying in any horizontal coils through bleed taps on either side of the coil from time to time when in operation. The one in the Igloo cooler picture does not appear to have any way to remove condensate forming in the loop bottoms. I keep a cylinder of nitrogen handy for this on mine and at times--augmenting air flow.
But people can forget about the most important part--the final air expansion out your spray gun. Pull the trigger on your gun and feel the "cool" air. Why is it cooler? The compressed air pressure went from 30psi or so from the inlet into your gun to zero-gauge pressure just outside the fan spray pattern. Hence, a large rapid expansion in the air volume and a temperature drop of the airflow exiting the spray gun. If the temperature drops here below whatever the atmospheric temperature dewpoint is--you are going to get water drops either in your stream or off the metal surfaces of your gun end when you are spraying. Look at your car's exhaust pipe tip on a humid 45-50F day and the engine is running--many look like a leaky faucet right at the end of the tail pipe for this very reason. I followed a brand new Audi today and it looked like a garden hose dripping a line of water drops out in front of me. I looked really close at a stop light and the condensate from whatever water vapor was in the exhaust gas was forming just on the very bottom of the edge of the tailpipe to atmosphere interface where the pressure of the exhaust just went to atmosphere and gave up its energy in a rapid manner.
Only refrigerated driers with enough passes through them will condense what remains for a third "below ambient temperature dewpoint" drop out" right before your booth or spray area if that's how you want to use your compressed air for most locations with appreciable humidity. If you live on either coast or the hot humid summers in the south-east USA--that is the best insurance policy for successful dry air with no likelihood of moisture in your spraying. Otherwise, it is just a crap shoot depending on the weather if you don't have a nice climate-controlled work area at 70F to work in and the air your compressor pulls in. Most people are not so blessed.
I played with compressed nitrogen cylinders and ganged some together in a manifold with a high flow regulator and was astounded at the difference using a gas with all the same sized molecules for spraying a host of finishes and no moisture in my spraying gas. Lays out what I sprayed like glass. Most of the welding grade nitrogen is 99% for non-military work or very heavy plasma cutting. Could work well for giving things a boost if desired on marginal sized compressor set-ups.
.
Look at the two large threaded bushing in your air tank shell--should have two on the cylindrical shell usually opposite side to where the weld is in the shell going the long way up and down on a vertical tank. One is about 2 NPS in size and the one inside that should be 3/4" with a plug in it. That's the manufacturers way to nudge the user to plumb with 3/4 NPS threaded steel pipe for the plumbing---not copper tube. Sweat soldering is not recognized for joining copper for compressed air use by any acknowledged pressure piping code--it is fine for potable water. Usually, it is "silver brazing" for copper and compressed gases. I shutter to think what used to be common 50% silver alloy brazing wire is now per lb in $$$$.
The original poster asked about 1" galvanized steel pipe. Good choice, I use pipe A-53B in 1 NPS or 3/4" NPS in same material specification either STD wall or XH thickness. Forged steel A-105 Class or threaded fitting are a bit more money than class 150 cast iron hardware store stuff but are way easier to work with. Avoid cast iron or ductile iron fittings if you can. Too much garbage now from overseas with badly cut pipe threads. If you are near a Ferguson they will set you up better than any box store ever could.
Intercoolers between the second stage cylinder outlet and the tank are "problem children"...........subject to fatigue and stress corrosion cracking in use. Nature of the service and metallurgy for dissimilar copper tubing/aluminum fin brazing making them cheaply helps contribute to this. All copper fin is way, way too expensive for such a use. Automotive transmission type coolers are not designed for compressed air service or pressurized cycling on and off of the compressor pump they are attached to. Don't be fooled by a pressure rating on one made of aluminum alone. That often kills these things prematurely. Blow one of the return bends out in operation--watch-out you are likely on the uphill side of the pressure cut-off switch for regulating the tank being at or below 175psi. Especially if you forget to turn the electrical switch off at night or leave it on all the time and go out for a while. All your manufacturer's warranties for a new compressor will be voided doing so. Likely--your insurance policy as well if there is a problem.
Contrary to what many end-users think--the secondary design purpose of the air tank is to create a moisture condensing reservoir in these small sized air tanks. The primary purpose is to create an air mass energy supply that can be withdrawn at a desired rate constantly--10 cfm or so for an RP type gun that does not vary as a typical use example. Preferably, all the moisture condensate should be in the air tank alone and drained off at least daily before going home. That's how every air compressor manufacturer of these small compressors intends their equipment be used. But that's not likely to happen if you have a theoretical 5-7 minute window at most for drawing down your tank from 175psi to 90psi and adding more in the mix as the compressor kicks in to replenish that withdrawn for paint spraying. I use automatic drains and I am glad I do but they are overkill for home use.
Chris Hamilton's post shows an engineered system for the piping that has been in a lot of publications for small sized commercial compressors and light manufacturing, body-shops, etc..... It is very successful and dates back decades when all industrial compressors were horizontal tanks in the 's as shown in the picture were standard practice. It is standard engineering text-book stuff for fluid mechanics, etc.....In , it is still a good first choice for someone at home setting up or a small business from 5 to 7.5HP, 80 gallon, 175psi, 15-25 cfm pump output set-up. It is already engineered for you. No liability for design for you, any employees with OSHA hazard mitigation concerns go away if in a commercial application and consistent with an institutional code for such using the materials below. Your insurance agent could never balk about you installing that or using it--provided the pressure relief valve on your tank protects the piping. Other things I see on this forum about pressure piping........not so much so and uses of copper. Providing three vertical drop legs paths for the second round of condensate from cooling air in the pipe to fall out into and drain off is very good.
In the air distribution pipe--you will never be any better than the ambient temperature and that relative humidity wherever you are working unless you refrigerate. Dessicant is mostly ineffective because of the time exposure of the air flow to strip it out of the moving air mass for many climates. You will get some moisture out but not much in a moving air stream--not enough time. Good for gun safes, and static air spaces. For a very dry hot or cold climate or dry and high elevation users maybe enough alone in some locations and seldom use.
For "aftercooler coils"--best to have drain taps or use compressed nitrogen or heavy argon to force out condensate lying in any horizontal coils through bleed taps on either side of the coil from time to time when in operation. The one in the Igloo cooler picture does not appear to have any way to remove condensate forming in the loop bottoms. I keep a cylinder of nitrogen handy for this on mine and at times--augmenting air flow.
But people can forget about the most important part--the final air expansion out your spray gun. Pull the trigger on your gun and feel the "cool" air. Why is it cooler? The compressed air pressure went from 30psi or so from the inlet into your gun to zero-gauge pressure just outside the fan spray pattern. Hence, a large rapid expansion in the air volume and a temperature drop of the airflow exiting the spray gun. If the temperature drops here below whatever the atmospheric temperature dewpoint is--you are going to get water drops either in your stream or off the metal surfaces of your gun end when you are spraying. Look at your car's exhaust pipe tip on a humid 45-50F day and the engine is running--many look like a leaky faucet right at the end of the tail pipe for this very reason. I followed a brand new Audi today and it looked like a garden hose dripping a line of water drops out in front of me. I looked really close at a stop light and the condensate from whatever water vapor was in the exhaust gas was forming just on the very bottom of the edge of the tailpipe to atmosphere interface where the pressure of the exhaust just went to atmosphere and gave up its energy in a rapid manner.
Only refrigerated driers with enough passes through them will condense what remains for a third "below ambient temperature dewpoint" drop out" right before your booth or spray area if that's how you want to use your compressed air for most locations with appreciable humidity. If you live on either coast or the hot humid summers in the south-east USA--that is the best insurance policy for successful dry air with no likelihood of moisture in your spraying. Otherwise, it is just a crap shoot depending on the weather if you don't have a nice climate-controlled work area at 70F to work in and the air your compressor pulls in. Most people are not so blessed.
I played with compressed nitrogen cylinders and ganged some together in a manifold with a high flow regulator and was astounded at the difference using a gas with all the same sized molecules for spraying a host of finishes and no moisture in my spraying gas. Lays out what I sprayed like glass. Most of the welding grade nitrogen is 99% for non-military work or very heavy plasma cutting. Could work well for giving things a boost if desired on marginal sized compressor set-ups.
.
Look at the two large threaded bushing in your air tank shell--should have two on the cylindrical shell usually opposite side to where the weld is in the shell going the long way up and down on a vertical tank. One is about 2 NPS in size and the one inside that should be 3/4" with a plug in it. That's the manufacturers way to nudge the user to plumb with 3/4 NPS threaded steel pipe for the plumbing---not copper tube. Sweat soldering is not recognized for joining copper for compressed air use by any acknowledged pressure piping code--it is fine for potable water. Usually, it is "silver brazing" for copper and compressed gases. I shutter to think what used to be common 50% silver alloy brazing wire is now per lb in $$$$.
The original poster asked about 1" galvanized steel pipe. Good choice, I use pipe A-53B in 1 NPS or 3/4" NPS in same material specification either STD wall or XH thickness. Forged steel A-105 Class or threaded fitting are a bit more money than class 150 cast iron hardware store stuff but are way easier to work with. Avoid cast iron or ductile iron fittings if you can. Too much garbage now from overseas with badly cut pipe threads. If you are near a Ferguson they will set you up better than any box store ever could.