Compressor Capacity to Supply a Pressure-Pot Spray-Gun

      Reliable and powerful air supply matters for pressure-pot equipment. Here are tips on sizing up your unit. July 18, 2008

Question
I am a one man shop and do an occasional kitchen. I spray waterbased dyes and clears. My main clear finish is the Becker 318. It has 38% solids so it is a little thick for water.

I would like to know what type of system I should get. I think a Kremlin or the like is not in the budget right now. Is a pressure pot in the mix? I have a 6 gallon Porter Cable compressor. 6.8cfm@90psi and 8.6cfm@40psi with a free flow of 10.1cfm at 6psi

Forum Responses
(Finishing Forum)
From contributor A:
I also am a one man shop. I used a gravity feed HVLP gun for the longest time with great results. I have just added a 2 quart pressure pot and gun to the arsenal. The pot is nice for when you have a lot of spraying to do as you don't have to refill as often. The gravity feed gun is nice because it is super fast to clean and switch finishes. If I were to only have one, I would just buy a gravity feed.



From contributor B:
I've never tried a pressure pot, but I'd be concerned that you'll be operating at the very limits of your compressor's capacity. I used to use a small, portable compressor (2 HP, 10 gallon) to run an HVLP gravity gun. Because the compressor was running almost constantly during spraying, it never got a chance to cool down. This meant the air stayed warm, and carried a lot of water vapor into the hose where it condensed and caused finish problems. I was able to work around this by slowing down the work, but of course this cut into my productivity.

Last year I bought a second-hand 5HP stationary compressor, stuck it in the basement and ran copper tubing out to the shop. I think I spent around $800 for the used compressor, a few parts to bring it up to snuff, plus the pipe and necessary electrical components to hook it up. Jobs that used to drive my old compressor to the brink of mechanical failure are a walk in the park for this machine. I guess my point is that you should keep that old "penny-wise, pound-foolish" warning in mind.



From contributor A:
Contributor B is right on - your compressor will not keep up at all. I use an 80 gallon 5HP that delivers 18.5cfm @ 100psi and it still kicks on every 3 or 4 minutes while spraying. Your little 6 gallon tank will be drained almost immediately, forcing it to run continuously and even then the pump won't be able to keep up with the gun.

You definitely need to upgrade the compressor. One of those big box store jobs that are 5HP and 60 gallon will work, but for a little more dough, you can get an industrial unit as mentioned and you won't be replacing it for a long time.



From contributor C:
The Craftsman 5hp 25 Gallon compressor is the most common one I see out there, and it seems to give great reliability so long as they haven't goofed with their motor and piston. I used one for several years spraying a lot of lacquer and it worked fine.

As far as spraying guns, I have personally found that the mid range HVLP guns are as good as the high end HVLP's (talking gravity feed guns here). I used a CA Technologies Jaguar gravity feed for several years and it's a good gun, but has its limitations. I moved from the state I was working in and now work for a company that uses archaic conventional stuff, but I personally bought a Porter Cable gravity feed HVLP that, in my opinion, sprays a better finish than the CAT Jaguar.



From contributor A:
I have a Devilbiss Finishline gun that sprays quite well. I also have the Porter Cable gun that also sprays quite well. I have used the CAT Jaguar and didn't like it as it wasn't comfortable in my hand. I now also have a Devilbiss CVi gravity feed and a Devilbiss CVi pressure feed gun. Hands down these are the ones I always reach for. I love them and highly recommend them. If they are out of your price range, the Devilbiss Finishline kit is quite a good deal as you get a couple tips and a little touch up gun. The other guns are now reserved for spraying junk (anything but sealers, lacquers, and conversion varnish).


From contributor C:
I had a problem with the Jaguar's aluminum cup. It would pool up some finish in the threads where it threaded to the top of the gun, and occasionally drip grey goop onto what I was spraying. It just came loose too easily. And yes, it was uncomfortable to use.


From the original questioner:
I screwed up. I have a 6 hp. 25 gallon. Not 6 gallon. My fault. Sorry.


From contributor B:
Were the "6.8cfm@90psi and 8.6cfm@40psi" ratings also wrong? Those numbers are not consistent with a 6HP compressor, regardless of tank size, unless it's 'peak horsepower' (A.K.A. "B.S." horsepower).


From the original questioner:
That's what the tag on the tank says. I copied of the internet the information and pasted onto this forum.


From contributor B:
I understand. I don't mean any offense or to suggest you copied the information incorrectly. What you've got is a creatively marketed product. Your 6 HP compressor won't even come close to keeping up with a real 5-horse unit. I still believe you'll be pushing at the limits of your compressor's capacity with pretty much any gun available, which is not to say you can't make it work for the short term.

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