What size air lines do you use in your shop?

PVC for Compressed air use in any wall thickness is BAD business.

I have it in my shop and it's been there for 15+ years.
It has never exploded but it does crack and leak and needs to be repaired every so often due to becoming brittle with age.
I plan on replacing it with Sch 40 Black Pipe soon as I get the time and extra bux to do it. Rusting with Black pipe is not an issue......it would take 50 or more years to rust thin enough to be any danger. The filters before your regulators catch any small rust particles that get free in the system

I would NEVER use PVC again for air lines.

 

Well if that is the case as you say then as I said, use a compliant gun over an HVLP gun due to the much superior trans/compliant gun's atomization of components by the shear physical design of the air passage ways in the gun and the superior atomization structure capabilities of the air cap.

The details in the craftsmanship of applying multiple coats of lacquer is not just so you will have enough paint to do the necessary buffing to bring to shine when completed, the craftsmanship is in applying multiple "thin" layers. Because with lacquer thick layers will come back to bite you in the ass when things start shrinking and cracking.

An underground or under slab air line will trap the water in the line if it is below the tank level of the compressor and this will eventually come back to bite you as well because the I.D. of the pipe line will be reduced thereby speeding up the air flow as well as restricting it.

Regarding buying Chung-king steel pipe at the big box stores. If you don't want it then don't buy it. Go to a dedicated contractor plumbing house and spec for U.S. pipe. It is still made here and you can get it. The threading will be superior as well. When assembling use commercial grade monster pipe tape over the threads with a coating of shark pipe sealer over that then thread your components together.

 

When I built my last shop I looked into PVC. A friend pointed out that the pressure rating of PVC decreases with temperature, a lot.

Since it can get really cold in the shop I put in black iron pipe and expect to do the same in the new shop that I am building.

 

This is the right idea !. The trick is to get the air expanding as soon as it leaves the hot compressor's out ports. Ideally, one should have an adjacent expansion tank with drain right next to your compressor then the manifold system connected and going from there. Actually in a sense this is what a cooler unit does anyways but adds a coolant to create a cold wall environment for the moist air to condense onto quickly as the air passes by.

 

i never liked the way my hvlp gun laid the paint down. when i moved my shop i redid all the lines and installed a large pressure regulator after the dryer, instead of using the one mounted at the gun, and the gun works much better.

 

I heard that PVC failure occurs at the fittings not the pipe. Mine is 3/4 copper.

 

Gotta love the HAMB! I'm replacing my copper system with a 1.5" galvanized setup including the "high flow" fittings.

 

Well it hasn't bit yet, nor do I expect it ever will. I think the surface (craftsmanship) was good enough to allow the lacquer to do what it does best, no?

 

Has anyone tired/had any luck with those blue plastic type piping kits?


The price has come down on these type kits and it seems like you can do a standard double car garage for not too much money

any thoughts?
Bobby

 

So what are these high flow fittings you speak of ?

 

Good question. First learned of them in whtbaron's post# 50 and was about to research myself. Can you help, whtbaron<label for="rb_iconid_5"></label>

 

Take and pickup a common air coupler or nipple and take a good long look through the center bore of it. What you will see is a reduction in the through put I.D. port size. This is because of the design. Let's say you start out with a 3/8 inch I.D. hose. Then you connect one of these common pieces to the end of your hose. Well now the I.D. is gonna be restricted to what your coupler or nipple I.D. is and that is usually at least 5/32 less and sometime even more. Especially with an HVLP ( High Volume Low Pressure ) gun you want a constant High Volume as the name implies. So in restricting the flow of air you are restricting the volume of air because PV=nRT.

DeVilbiss sells what is called HVLP High Flow Couplers. You can buy them on line from Len at the body shop store or TCP sells them as do many other jobber supply sites on the internet. These high flow couplers and nipples maintain the same I.D. throughput for whatever I.D. size your are working with and need 3/8, 1/4 etc.

 

I used all copper1-1/4" down to 1/2" for service. I also have two automatic IR water dropouts, one near the compressor and one near the end of the main distribution line and I have manual dropouts at each service drop. Only the water dropouts have 3/8" pipe.

 

If you want compressed air to cool in the lines and condense out the moisture, no common material can beat copper for doing the job.

One preious post claims steel is superior and goes on about radiant heat transfer in some description that went over my head even though I've been a mechanical engineer for 40 years and have a fair bit of both practical experience and schooling in heat transfer.

The simple fact is that the only way heat passes from inside a tube to the outside is by conduction, not convection or radiation. The speed with which the heat will travel thru the tube wall is dependent on the thermal conductivity of the tube material and the wall thickness of the tube. The higher the thermal conductivity, the faster the heat transfer. And the thinner the tube wall, the faster the transfer as well.

So, if you compare copper's thermal conductivity of 400 to that of steel at 43, you'd expect the copper to shed heat to its exterior a bit more than 9 times faster than steel. Then, when you look at the typical wall thickness of copper tube suitable for air piping, Type M hard copper, as compared to Sch 40 steel pipe, you find the steel pipe's wall is more than twice as thick as the copper tube's wall.

Conservatively, you'd expect the copper to transfer heat twice as fast as steel strictly due to difference in wall thickness. But, when you look at the combination of wall thickness and conductivity, the copper will conduct heat from its interior to its exterior wall about 19 times as fast as steel pipe of the same approximate size.

Once the heat is at the exterior wall of the tube, the cooling of the tube is dependent on radiant and convective transfer. The brown varnish like coating on typical steel pipe also impedes both radiant and convective transfer, so the steel pipe loses even more ground in the race to cool the compressed air in the pipe.

None of this is magic. Its just the sort of stuff many mechanical engineers work with every day. And I'm not saying steel pipe makes an inferior air piping system, but just simply stating the fact that, if you want the piping system to cool the air, then copper will do that better than any other piping material.

If a person decides to go with a copper tube air system, its best to avoid the home centers and get your material directly from a plumbing and piping supply house. They will stock Type M copper, which is the thinnest wall of the 3 common types of copper tubing. Because it has the thinnest wall, its also the cheapest of the 3 types. But it still has a safe working pressure above 500 psi when made up with soft soldered joints in any of the sizes commonly used for air systems.

All that said, in a larger shop it makes sense to use a refrigerated air dryer after the compressor and then run the air piping system using the most economical material that's suitable for the use, and without having to worry about pitching the lines or adding multiple drain points to the system. If the moisture never makes it into the system, then you don't have to be concerned with how to get it out.

 

I've had about 80 ft of 1" sch. 40 under 120 lbs. pressure 24/7 for at least 6 yrs. The pipe runs in my ceiling where the temp gets over 120 in the summer and at times near freezing in the winter.

As far as volume goes the imprtant thing about your compressor is not the HP or the size of the tank but rather the CFM output.

 

About 7yrs ago there was a push in my area to convert all the standard fittings we've used for decades to these high flow/volume fittings. One shop I was in had them. I noticed something right away, IT MADE NO DIFFERENCE IN THE QUALITY OR TIMING OF MY WORK.

My "P" sheets and spray gun paper work says 25PSI at the gun. Even with the cheapo screw-down regulators at the entry of the spray gun the pressure STAYS at 25 as long as I pull the trigger. High volume fittings or standard 1/4" pipe versions. Why is hard for some to understand that the VOLUME is the material and not the air? Not directed at you vic...

 

You can't make the main header to large. As previously stated it acts as a resevoir and helps to maintain pressure longer.Also the smaller and longer the run the greater the pressure drop. A storage tank on the end of the line is a great help.
A refrigerated air dryer(expensive) of proper size is the best way to eliminate moisture.

 

pvc is fine ,been in my shop for 10 plus years. Do yourself a favor and at the bottom of your drop downs plumb a tee. Attach your valve to the horizonial end and put a drain petcock in the lower one(even if you have a dryer) it will save your tools.

 

I just installed a system like this ( 3/4") from "Eastwood" very nice system and not all that expensive.

 

My shop is only a 2 car garage so I buy a 50' roll of the black Goodyear hose and cut it in half and use 2-25' lines

 

That's essentially truck air brake hose. The trucks use a different type of fitting, though. I have it in the basement, and it's worked well for the past 20 years. The flexibility is handy in that it can be pulled through holes in joists or studs almost like romex.

 

I use those fittings on my TAFC.

 

. . . As said earlier it is physics which dictates copper is not as good of radiant convector of heat however, it is an excellent transducer along it's own axis of heat. That means if you want it to loose it's heat build up efficiently the only physical way is to add an air flow across it which in turn becomes the radiant conductor and transfer agent of the heat. This is not someones opinion this is how different types of metal react to heat. Plastic cannot radiate or covert heat but it is an excellent insulator of heat and damn easy to install no matter what else it cannot do.

Anyways I have said my soap box sermon. My recommendation is for folks to use whatever manifold material you think is the best because after all you know best and what you have selected to use is therefore apparently the best for you no matter what and because no doubt about and no matter what anyone else says your the boss of your shop.

 

I've got an uncle that brags that he's been drunk driving for 25 years and ain't killed no one yet. Much like saying PVC is fine for shop air. It's still wrong. Ron

 

I've had 3/4"(?) PVC for 10 years in my shop (suggested from friends that have it for twice that so far). It's rated at 450 PSI. My guess if it did fail, it would split somewhat in slow motion and not be a problem. I've had several of those cheapie 25 foot coiled air hoses split that way. I'm not saying it's right, but it's what I have, and that's how long I've had it. Oh, and I close a ball valve at my compressor each night

 

Interesting. Says 150 PSI, and that's right where I run my compressor. I'm not sure I'd be OK with that

 

That doesn't appear to be the SAE rated brake line. I got mine through NAPA, and it uses "wedding band" compression fittings instead of the "push in" type in the illustration. That stuff is low pressure compared to mine.

 

My shop is also a 2 car garage. I have a ball valve at the compressor (I shut it of every night) that connects to the quick connect attached to my 50' red (or maybe this one is yellow) rubber hose. At the other end is another quick connect that I connect my air tools to. One hose, 50', I can reach stuff outside my shop. If I need it, I have a 2nd 50' hose (that one maybe black, if it matters) I can connect to the 1st hose. I have to change the hoses about every 5 years. I drain the water out of the compressor every morning. This system has worked well for me for 20 years. Gene

 

That blue tubing is PEX not nylon air brake tubing. Vary different stuff!
I do it the simple way, 50' 1/2" air hose with a water separator plumbed in right off the tank, good enough for air tools, not for paint. For painting I have a desiccant drier/filter and one air hose that I only use when painting.