Hot Rod Forum banner

2 compressors, which should i get?

9K views 39 replies 12 participants last post by  oldred 
#1 ·
#27 ·
Quote from OldRed.
==========================================================
x711, From your discription it sounds like you have your dryer mounted on the tank? If so it will not do much good in that location and really should be located well downstream from the compressor itself or at least run the air through a cooler between the tank and dryer. There was a discussion here about water in the air lines just in the last few days.
==========================================================

Well lets think about this for a sec and then follow it up with some hard
data. As the compressor runs it generates heat, this heat will condense
the air and the end result is water. Since water is heavier than air it
will make its way to the bottom of the tank and also into your air lines
espically if they are made of copper or brass.

So the idea is to keep water out of your air lines as you have to spray
with this air.

My dryer/water trap is mounted on the tank and coupled via brass tubing.
It basically hangs off the tank by about 6" or so.

Today I primed some parts over about 3 hours 65% of the time was used
to paint. I used a Finex FX300 with 1.8 needle made by sharpe.
The primer was well atomized and lay down smooth and flat. Alot better than
what you typically get from a spray can.

I measured the air temperature prior to starting. The ambient air was at 63
degrees F where the compressor is located, the actual air humidity was at
48.9%.

During the spraying the compressor cut on 5 times for a couple of seconds
over this period of time to re-charge the tank. "This did not hamper gun operation"

When I was completed I checked the tank and air/dryer for water.

The tank contained 2 tablespoons of water/oil. The dryer/water trap
contained 10 drops of water. I had not checked my air lines for water
since day one as I have been using the compressor about 3 to 4 times
a week lately. When I checked my 50ft air line I found no trace of water.

The results of the tank water check can be somewhat incorrect. Here
is why. Compressed air is getting forced through a small drain plug. This
drain plug will cool down with the passing air and thus condense right at that point which in-turn creates water.

I have no idea what others on here use for their air setup so I can only
comment on what I have.

What I have works! for me in my garrage setup. :)

Thanks X.
 
#28 ·
I was doing a search and came across this thread. I haven't been reading the tool posts because I am trying to learn how to paint. It may be too late for you but I bought the Kobalt that old red was referring to. I am very much pleased with it. It seems like a good compressor. It was originally $797.00 but I was able to get a 10% discount by putting it on my Lowe's card. I just sent the full payment check in today so I won't have to pay any interest. I hate to pay interest. That is money I can buy another tool with. Not all Lowe's carry this compressor. I couldn't even find it on their website. If you haven't bought one yet do a search on Kobalt because I posted all of the specs on this site. Good luck with anything whatever you buy.

Danny
 
#29 ·
X711, I hate to disagree but you are wrong about almost everything except the compressor generating heat. "this heat will condense the AIR :confused: ? and the end result is water"? I would suggest you refresh your self on physical science , Where do you think this water comes from? Anyway what really happens is that the hotter the air the more water it will hold in VAPOR form and until this air is cooled to allow the WATER VAPOR to condense(this is the dew point principle) into a mist in the air and droplets on the tank and pipe walls then the dryer(actually a water separator) cannot do much to remove it. A water separator works by spinning the air as it passes through thus using centrifugal force to sling the heavier condensed water out of the air allowing it to be collected in the housing of the unit. Water vapor, however, is for all practical purposes unaffected by centrifugal force and passes through into the air line where it cools and condenses into liquid water on the hose walls allowing it to exit into your tools,paint or whatever. The air coming directly from the tank is still hot unless the compressor has been sitting idle so most of the water contained is still in vapor form due to the higher temperature and thus will be unaffected by the centrifugal force of the spinning air in the separator that is why the air must be cooled by some method before the water can be removed. This is most commonly done by using a length of METAL pipe between the tank and the separator but sometimes a cooler is used. This is common industry practice and just plain common knowledge and if you take the time to research air plumbing systems you will find that these principles are incorporated into almost every design except for the systems that use a refrigerated dryer to cool the air before water removal.
 
#30 ·
re:compressors, which should i get?

OldRed, I did my research in advance and have seen many air layout diagrams.

With my setup "Home Garrage" the actual run to my gun is minimal so I dont
see any problems with what I have now. If I had more space and the budjet
I would put in a chiller or move the water trap/dryer further down the line
away from the tank as an experiment to see if anything could be gained.

Currently though I see little advantage to this as I am not running into
any problems laying down paint or primer.

But if I can draw on your experience, what would be the advantage of
re-doing what I have. Any advice is most welcome.

Also I am curious are you in a body shop or have you got a home setup.

What type of compressor / dryer system / gun etc do you use.

Is your measured air temperature at the end of the line cooler /warmer
than the area you paint in.

Thanks in advance. X
 
#31 ·
X711, There was a thread here recently about water in air lines that pretty well covers the basics of removing water from compressed air. It really does not surprise me that you had very little water in your air considering the conditions mentioned and the fact that you only sprayed some primer over a 3 hr period. Usually water is not much of a problem with moderate use unless the air is really humid but if you tried to use something like a sandblaster on a hot humid day with the set-up you have described you would run into big problems. The purpose of locating the separator(dryer) a good distance from the tank is to use the pipe as a cooler that is why it's best to use metal line for this but if this is not possible, which in many cases it's not, then a cooler of some type is sometimes used. The bottom line is that in conditions of high humidity(common summer time weather) hot air from the tank is loaded with moisture in the form of water vapor and this air must be cooled to a point where that vapor is condensed into liquid water before it is passed through the separator or it will pass on into the lines and condense there as the air continues to cool. If all you notice is water droplets on a tool such as a DA sander then that will not be much of a problem but when a bunch of water drops hit that $300 a gallon paint then the importance of a properly set-up plumbing system becomes all to apparent. As for my set-up I only paint as a hobby but I have installed air systems as part of my welding business for over 30 years.

BTW whatever you use to dry the air I would still strongly recommend a disposable in-line filter when painting just to be sure.
 
#33 ·
What not to buy

I wish I had seen this thead earlier, My son and I bought a commpressor, it was a 60 gal. 6hp 220V, it was a good compressor, it would put out enough air to run my sand blaster non stop if I wanted to push it, BUT , it has a V-twin pump on it, one of the oilless type compressors, you could look up under the plastic cover on it and see the bottom of the pistons,cylinder walls and the rods, it has sealed bearings on the rods and the wrist pins,

I turned it on one day and heard a weird noise and seen a puff of dust come out of it, I didn't think much of it at the time but from that day on I noticed it was takeing longer than normal to build up air pessure and shut off and I would run out of air very quickly when doing any sand blasting,

It was out of warrenty by this time , I put a new filter in it but that didn't help a bit, I took the plastic cover off of it and looked at the bottom of the pistons and noticed a lot of scareing and scratches on the cylinder walls, so I took it apart, the pistons on this thing are only like an inch tall, they have a neopreme(sp?) ring on them instead of a steel one and the rings on both pistons were worn down the metal on the pistons :(

What had happened is ,I have a lot of those wasp called Mud Dobbers around here and they had built their nest up under it on the cylinder walls,it had been a while between uses giveing them the time to build their nest, their nest being made of dirt and sand ate the rings right up on it when I turned it on, this was the noise and the puff of dust I had seen earlier, I looked and parts of the nest were laying on the floor under it,

This a poor design if you asked me, I wrote to the company that made the commpressor and complained about it but I never heard a thing from them, I also asked for a parts list so I could rebuild it , they have yet to send me that either,I bought a new smaller compressor with a twin cylinder that is sealed completely up, the old fashion kind that you have to put oil in ;) ,so if any of you have this type of compressor here is a tip for you,

You might want to take some small mesh screen and put it around the top of the compressor, like window screen, and tape it along the bottom of the tank to keep these wasp out, it is a shame that a tiny wasp can destroy a $600.00 machine but they can, I hope this helps some of you :)

This is a Charge Air Pro, Made by the Devilbiss Air Power Co. by the way :(
 
#34 ·
Bugs, I have seen those dang things destroy good equipment before and not long ago I lost a variable displacement hydraulic pump that cost nearly $1500 plus a whole day of labor :mad: because one had built it's mud nest inside either the pump or the line. I know this is what happened because we found parts of the little critters inside. I have found this problem sevral times and cleaned it out before anything bad happened but that time I missed it. You have brought up a very good point here that IMO should have been a new thread because this happens so often and is overlooked so much.

Thanks for the heads up you just may have saved someone a lot of money and headaches
 
#37 ·
I looked at the Kolbalt 80 gallon, compressors in Lowes last night, I sure did like it,and they are priced very good too,I wonder if they'ed take the small one I bought there in on trade for one :D Just kidding, I like my 20gal,5hp,alright,like I said though as soon as I get my shop done I think I will plumb it on top of the 60gallon tank I have that's under the compressor that the mud dobbers ruined, then I will have more air volume for my sand blaster,and what ever(if my future son-in-law ever returns it) :)
 
#38 ·
I wouldn't get a craftsman comp. Me and my fam. has 3 oil less 2 25 gal, and a 60 gal. I just bought the 60 Gal 6 months ago have not used it that much but my brothers 4 years old used normal and grandpa's hardly used comp. make noises. Dad's old old old campbell used all the time! paint, DA, impact..... still going strong! :thumbup:

My vote will have to be Campbell Hausfeld, wait and save some more money.
Don't be like me and impatient and end up with a junk comp. Home depot has husky comp that are made by CH:

http://www.homedepot.com/prel80/HDU...=Search&cm_pla=D-25X&cm_ite=bid10092250-husky

Offers 175 PSI maximum pressure and air delivery 15.1/13.7 SCFM @ 90/175 PSI.

$869.00 :D
 
#39 ·
Well, I decided to go with the IR compressor. It arrived a few days ago and I have been using a DA sander with no problems. I noticed water in the lines, so I am going to read up on the solution on these forums before I use my spray gun.

Thanks again for everyones help. I am sure I will need more later.

-Josh
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top