Air compressor - Cooling the air

[RoatanBill]

I'm looking at a Quincy 60g compressor with a 1/2" outlet. Humidity on the island is high year round, as is the temperature. I need to cool off the air before it hits a filter/moisture trap/regulator and on to a paint gun.

I've seen pictures of copper plumbing up and down a wall with multiple drains and loads of connectors (points for leaks) and I was wondering if my plan has any down side experienced people might recognize.

I'm considering a 60' coil of 1/2" ID copper (rated to 800PSI) roughly 30" in diameter where I'll gently form the coil into a pyramidal slinky shape so that any condensation always runs down hill. I'll suspend the coil above the compressor, properly supported, with rubber hose as input and output to handle vibration. If necessary, I'll add a piece of copper pipe and valve just before the regulator assembly to catch gross amounts of water.

Can anyone see a down side to this?

[Gamble]

As long as you have a way to drain it you should be fine.
Why not a compressed air dryer?
https://www.harborfreight.com/compre...yer-40211.html

^I have this and love it.

Few minor issues with it:
*you need to provide and install your own 110v plug and the cable is a little short
*no fittings included. I spent about $80 on fittings, valves and making a bypass in a H configuration
*Expect minor shipping damage as UPS is a bunch of as*holes

Aside from that it will be the best $400 you ever spent. My air is dry to the bone and this thing runs very quiet.
Here is my setup:
compressor --> air dryer --> regulator --> motor guard --> hypertherm air filtration kit -->plasma cutter

Everything else is T'd off after the motor guard. I also used the rapid air plumbing system with drains at each drop and a T or 3 way fitting at each end

[RoatanBill]

The Quincy outputs 175PSI. That air dryer maxes out at 140PSI. I could put the unit after a regulator.

The compressor I'm replacing is a cheap HF compressor. It still works, but doesn't put out enough air volume to properly run a 3M spray gun. I thought about plumbing in its 27g reservoir to hold regulated air and could put the dryer in that loop.

After doing business with Harbor Freight for over 15 years, they turned down a $600 order because of a new company policy that states they won't ship to a freight forwarder. I always paid my bills and even got thank you notes from the owner for all the large orders I submitted. Then they cut me off due to some BS new policy. I ship everything through my freight forwarder in Miami and it's never been an issue with anyone else. Amazon sends thousands of dollars worth of stuff to me each year via the forwarder.

I hadn't thought about an air dryer as the ones I noticed were overkill and too expensive. I'll think about it. Thanks for the suggestion. Just the copper coil is $175, so the dryer looks attractive.

[rexcormack]

RoatanBill,

I would call their customer service number 1-800-444-3353 and explain your history with their company.

If you go here and scroll don to international orders it clearly states that they "recommend" freight forwarders.

https://www.harborfreight.com/custom...elivery.html#5

[RoatanBill]

Been there, done that. They're web site is outdated. I even used their web site as evidence when I called them the last time.

I had an issue with an order about 6 months before they told me to get lost. I'd never had an issue before, so I called customer service. The woman indicated that it was the freight forwarder address that held up the order. I explained my long history and she put the order through. Then, later, on another large order, no amount of customer service contact was going to get the order released.

I'd get 2 or 3 orders a year for several hundred dollars each, as I have to clear customs on the island and that's expensive. The fewer orders the cheaper for me in terms of customs broker fees, lawyer fees, insurance fees, ocean freight fees, etc. Whatever the price of something is to get it to Miami, add 50% to get it to me on the island.

Last month, my wife went to NY to visit relatives and she brought back HF stuff in her luggage.

[RoatanBill]

I checked my email folder and found their last reply to me. Here it is:

Dear William,

Thank you for your interest with Harbor Freight Tools.

Due to a recent business change, Harbor Freight will no longer be shipping to any freight forwarders, brokers, and/or warehouse distributions centers.

Order 9482195 has been cancelled.

We apologize again, for any inconvenience this may cause.

Best Regards,
Cynthia
Inbound Sales Department
Harbor Freight Tools
P.O. Box 6010
Camarillo, CA 93012

[Bistineau]

Been there, done that.

Last month, my wife went to NY to visit relatives and she brought back HF stuff in her luggage.

Have you thought about getting your orders sent to your wife's relatives in NY and have THEM forward you your items?

[tweake]

The Quincy outputs 175PSI. That air dryer maxes out at 140PSI. I could put the unit after a regulator.

The compressor I'm replacing is a cheap HF compressor. It still works, but doesn't put out enough air volume to properly run a 3M spray gun. I thought about plumbing in its 27g reservoir to hold regulated air and could put the dryer in that loop...........


I hadn't thought about an air dryer as the ones I noticed were overkill and too expensive. I'll think about it. Thanks for the suggestion. Just the copper coil is $175, so the dryer looks attractive.

even with the dryer you still need the cooler.
to fit the dryer you could simply fit a regulator before it to limit the pressure. also fit a dry tank after the dryer will help a bit to.

cooper coil will work fine, but it needs cool air. putting it above the compressor is not good as that will get all the hot air off the compressor.
need to put it away from the compressor or in front of the compressors fan so it sucks air over it.
if the room is hot, have a look at mounting the cooler pipe outside. its commonly done with commercial setups.

fit an auto drain at the end of the cooper pipe. (or filter regulator with auto drain).

[RoatanBill]

Bistineau: Yes, I've considered it. I already pay for freight from X to Miami and then from Miami to Roatan. Adding a 3rd freight leg adds cost, adds time and my 90 year old parents in NY shouldn't provide the solution to a stupid corporate policy.

I have yet to figure out what problem HF was solving or avoiding. As long as they get paid, they should ship to anywhere I request. They successfully did it for over a decade in my case, so why not continue? I went to the US Postal Service to find out if there's some regulation that doesn't allow this discrimination for an address, but was told that they can do what they want.

Tweake: I thought the dryer did it's job by being a cooler. How else would one get moisture out of air? I'll research that further.

[Bistineau]

Tweake: I thought the dryer did it's job by being a cooler. How else would one get moisture out of air? I'll research that further.

Yes the air dryer is nothing more than a small refrigeration unit that cools the air to condense the moisture, it comes out much cooler than it goes in. We have one on a water treatment plant at work. An Inger-Soll Rand unit. We use air pressure into a hydro-pneumatic tank to pressurize the water system. It quit working a couple of decades ago and we didn't bother getting it fixed or replaced. Figured what's the point of drying air, only to pipe it into a WATER tank?
The 60' coil of copper tubing submerged in a cool tank of water or better yet some ice will cool the air nicely. I used a similar set up on an air supply line to a sand blasting hood. Was like air conditioning from the neck up. Much more bearable to sand blast that way in July in south Arkinsaw.

[RoatanBill]

This discussion has made me think through what I'm actually trying to accomplish. Thank you all for helping me realize my goal was simplistic.

I was just thinking of cooling the air down to atmospheric which would be 95 degrees for most of the year. Now I see that's not nearly enough to get rid of the moisture in the air no matter how much copper plumbing I'm willing to invest in if ambient air is the heat sink.

I definitely need the refrigeration to drop out the bulk of the moisture before it hits my Hypertherm 45XP or 3M spray gun. The other air tools I own would also benefit from the reduced moisture, but I lube them up enough to help insulate them from corrosion and I'm just not that concerned about them.

I'm going to forget about copper plumbing. You guys saved me from a malinvestment and wasted time and effort.

[tweake]

Tweake: I thought the dryer did it's job by being a cooler. How else would one get moisture out of air? I'll research that further.

yes a refrigerated dryer works by cooling, but they actually have a maximum inlet air temp which most compressors air output is well over. most of them are not designed to handle hot air direct from the compressor.
you can buy ones that are, they have a built in air-air cooler before the refrigerated part. the last standard type i looked at the maximum inlet temp was not much more than what the ambient air temp is in my shed. so even with a cooler its only going to be just under maximum.

some cheap skates do a dirty trick by putting a bigger dryer in after the compressor to compensate for lack of cooler. but its hard on the dryer, it has to work a whole lot more. heat is what kills dryers, having them work flat out in a hot shed is really hard on them.
also fitting a larger dryer uses more power, something you have to watch if your maxing out the power with welders/plasmas etc.
fitting a cooler is cheap and efficient. it handles the bulk of the heat with little to no power and is reliable.

also a thing to watch is a lot of the cheap refrigerated dryers leave out the 2nd heat exchanger. get one of a scraped unit and fit it, that will make it work a whole lot better and reduce another issue.
easy way to tell if you have one without that heat exchanger is measure the output air temp. if its way colder than inlet air temp then its missing the heat exchanger.

[tweake]

This discussion has made me think through what I'm actually trying to accomplish. Thank you all for helping me realize my goal was simplistic.

I was just thinking of cooling the air down to atmospheric which would be 95 degrees for most of the year. Now I see that's not nearly enough to get rid of the moisture in the air no matter how much copper plumbing I'm willing to invest in if ambient air is the heat sink.

I definitely need the refrigeration to drop out the bulk of the moisture before it hits my Hypertherm 45XP or 3M spray gun. The other air tools I own would also benefit from the reduced moisture, but I lube them up enough to help insulate them from corrosion and I'm just not that concerned about them.

I'm going to forget about copper plumbing. You guys saved me from a malinvestment and wasted time and effort.

keep in mind that you do not need to get rid of all the moisture in the compressed air. a refrigerated dryer will not do that anyway.
cooling down to ambient air temp will actually remove the bulk of the water.
refrigerated dryer does remove a bit more, desiccant or membrane dryer removes even more.
because you use the air pressure at a lower pressure than what the compressor makes, due to the air expanding when pressure is lowered, the airs humidity goes down. same water content but more volume of air. this means its not going condense in your lines, build up water and cause problems.

fitting a cooler on between the compressor and the tank is a good way of doing it. fitting a cooler where the pressure and temps are the highest makes it more efficient, so you can do all the cooling with a small cooler.
it also makes the check valve more reliable.
if you can fit one above the tank, the water will end up in the tank and you won't need a water trap. you can then drain the tank as per usual.

[RoatanBill]

Tweake:

I understand your points.

What are you using?

Here's my dilemma - Warranty means nothing to me on the island as I can't take advantage of it. Shipping, customs duty in both directions, etc makes any attempt to take advantage of a warranty uneconomic as the expense is usually too high. The HF dryer has many glowing testimonials but it also has numerous recent detractors. I don't want to take a chance on a device that appears to have a significant failure rate as well as not directly supporting the pressure the Quincy outputs. The fact that HF told me to bugger off is also a consideration.

Checking other available dryers leads to sticker shock. I make $0 from my welding. I weld for myself and my wife's business. The compressor is mostly for painting steel projects. Spending $1300 for a compressor, plus, plus, plus to get it to me is a significant expense. Adding a new electrical line, filters, regulators, etc easily brings my bill to $2,500. I can't justify spending another grand, plus, plus, plus for a dryer from a more reputable manufacturer. If I was making money with this equipment, that would be a different situation.

So, I'm back to square one.

[ironmangq]

Upsize the coil to 3/4 to help with frictional flow losses and put a drop leg and drain valve at the bottom. I've seen others do something similar, saw one who put the coil in a barrel of water to help with cooling and had a drop leg after the barrel cooler to catch the water.

[tweake]

Tweake:

I understand your points.

What are you using?

at home i have a small portable 3hp with a Derale tube and fin oil cooler i fitted to it between compressor and tank. (which is the most powerful i can run due to power limits)
have a cheap desiccant filter fitted as well (after the usual filter water separator) which i have started trailing. so far it has a fair bit of restriction, doesn't last long and desiccant is hard to get locally.
not sure if i will keep that.

at work we run a 7hp 140psi compressor to run a couple of machines. it has 30 yards of piping to the machines and i use that has the cooler. pipes are sloped and have drop legs fitted.
however the main reason we get away with not using a dryer is that the pipes go right past the air conditioner. so they get cooled by that and more water is caught by the drop leg and finally the filter reg. we are typically 80% humidity and on the high humidity days it will fill that filter reg.
its not the best setup but boss won't spend more on the plant. as long a the pipes are treated as a "wet" system (so you don't get water build up in the pipes) you can get away with it.

i can understand cost. compressed air is not cheap. thats one of the problems i find is that even pro's cut corners to keep costs down but that can back fire.
i had a guy who runs a similar plant who had water fill the pipes, flooded the water trap and machine. with cost of new rams, solenoids and loss of production, it cost him more than what a dryer cost. but the compressed air crowd never told him he needed a dryer, he had no idea what one was.
unfortunately they have now done the dirty trick of fitting the new dryer straight to the compressor. compressor and dryer in a small shed, in summer, that dryer will not last long.
they cut corners so often it becomes normal.

to add: with a 175psi compressor, if your often using low pressure (HVLP spray gun etc) then the pressure drop works for you. just fitting a primary cooler should work fine. thats also the starting point, so i would fit that then see if there is any issues. if there is signs of water issues then add a dryer of some sort.

[Tiggatoo]

See this post in another thread
http://weldingweb.com/vbb/showthread.php...57#post8634457

[RoatanBill]

Ironmangq: I considered the larger size but that would have to come out of Miami. 1/2" is the best I can find on the island.

I happen to have access to 4 large chest freezers that my wife uses as part of her business. I thought of just making blocks of ICE and running a coil inside a container that could hold really cold ice water. I've got temperature recording equipment (again, the wife's business) so I could test input and output temps to see what I get with X feet of copper. I haven't found a large piece of copper pipe to act as the water catchment, so that will probably come out of Miami too. I want to keep it all copper to avoid corrosion issues. I've never tried to fuse copper with TIG but have some silicon bronze available for experimentation or have the local A/C guy braze the joints.

Tweake: With my temps almost always at 95 degrees and super high humidity, I'm going to have to force cool the air to the plasma cutter and paint gun at a minimum to drop out the water. I'm not spending another wad of cash on a professional cooler/dryer as my use is too intermittent to warrant the expenditure.

I'll see how much water collects in the bottom of the compressor tank after the metal has cooled off to ambient temps. I read it takes 6.5 minutes on initial startup. That's my control for an experiment. The air inside the tank will still be saturated with water and from that air, I'll see how much more I can squeeze out by dropping the air to below 40 degrees. The tank on my existing HF compressor could be the output for the experiment. I expect to see absolutely no water in that tank. Because the HF tank has a large surface area, the air inside it will warm rapidly so the plasma and paint gear will see warm air; I think.

[RoatanBill]

Tigattoo: I read the whole thread and followed the links for other threads. Interesting stuff.

[Virgil5]

Why not just slip a coil of copper into the bottom of the wife's freezer when she ain't looking and use that.

[RoatanBill]

Virgil5: The freezers are too far away from where the compressor will be.

If the ice works, I have 2 old refer compressors from rotted out refrigeration equipment and might ask the local A/C guy to help me fabricobble something together. When I'm painting, I just know I'll forget to add ice when it's needed and a refer unit will just turn itself on and off as required.

[davec]

Lots of good ideas. Let me throw a different angle at you. Instead of trying to paint with an air compressor, have you considered an HVLP system with a blower? Yes, it will still cost a few hundred or more, but you avoid a lot of the air drying problems, for the most part. Perhaps you are in too humid of an environment, but it is another possible direction on how to fix the problem you have.

You can look up the tables on dewpoint vs temp and pressure. You know what is ambient. Then you pressurize it to 175PSI and whatever temp the compressor tank ends up at. So you can calculate the dewpoint in the tank. Then you can check out cooling that air at the same pressure to ambient temp and see what the dewpoint is now. That would be an example of putting a fan on the copper coil you described. My understanding is that -40 is the target dewpoint for dried compressed air. You won't get that from an ambient copper coil, but see how close it comes for starters. That would give you something to work from and decide if you really need more drying and an idea of how much.

I'm curious to see what you find. It is a Thermodynamics I problem...

[tweake]

Tweake: With my temps almost always at 95 degrees and super high humidity, I'm going to have to force cool the air to the plasma cutter and paint gun at a minimum to drop out the water. I'm not spending another wad of cash on a professional cooler/dryer as my use is too intermittent to warrant the expenditure.

I'll see how much water collects in the bottom of the compressor tank after the metal has cooled off to ambient temps. I read it takes 6.5 minutes on initial startup. That's my control for an experiment. The air inside the tank will still be saturated with water and from that air, I'll see how much more I can squeeze out by dropping the air to below 40 degrees. The tank on my existing HF compressor could be the output for the experiment. I expect to see absolutely no water in that tank. Because the HF tank has a large surface area, the air inside it will warm rapidly so the plasma and paint gear will see warm air; I think.

its hotter than that in our shed where the compressor is and at times just as humid.
however your high pressure is an advantage. there is a good chance of not having to force cool (ie use ice or refrigerated cooler).

[RoatanBill]

DaveC: I'm an EE/Professional Software Developer turned retired jack of all trades to keep my wife's business going. I remember hearing about thermodynamics in college, but I've slept since then.

I'm taking the brute force approach to do the most I can with what I've got and it has to be enough because I'm it around here. The level of competency for anything you care to name is absolutely abysmal. Ask a guy if he's a plumber and he'll say yes and show up with only a machete for the job. That's why I'm on this site; there are no welders I can talk to on the island because all they run are buzz boxes and there welds look like Fido's butt. The local "gas" supplier doesn't stock CO2 or Argon. As a matter of fact, he wanted to know what Argon was when I asked about it.

I had an HVLP gun for a number of years and it worked out OK, but the last project forced me to make a change. I bought the 3M Accuspray system only to discover that my ElCheapo compressor wasn't going to do the job. I really like the spray gun for the 30 seconds it works properly till the compressor starts up and then runs continuously if I attempt to push it, which I do, and I know I shouldn't. The primer or paint gets sputtered on to the metal, not sprayed.

I'm committed to the path I've started on due to stubbornness, lack of knowledge about alternatives and I'm getting too old to keep reinventing the wheel. Besides, the ElCheapo compressor is sounding pretty awful and I think it's about to send me a smoke signal. I need a compressor for the plasma cutter and other air tools.

The environment I work in is pretty extreme. I weld and paint in full tropical sun because I don't have the space to do otherwise. I TIG inside a 20' shipping container to eliminate wind and it's at 95 to 105 degrees which is ambient almost year round. I know this isn't how it's supposed to be done but that's the way it is.

[tweake]

My understanding is that -40 is the target dewpoint for dried compressed air. You won't get that from an ambient copper coil, but see how close it comes for starters. That would give you something to work from and decide if you really need more drying and an idea of how much.
.

good point. really need to know what dew point is actually required.
-40 dew point takes a bit of doing. refrigerated dryer doesn't go that low. you would have to go desiccant or membrane. both get complicated quickly.

i priced a membrane setup for work and that was a bit cheaper than a refrigerated dryer but lower flowing which suited our machines.
there is options out there.

i don't know the paint system, what pressure or dew point it requires.