One more time on running air lines

midnight sun · July 06, 2004, 07:35:29 PM

I know we have gone over this subject before (several times) but its always nice to have a refresher course.

Im getting ready (again) to plumb my air lines. Have decided on using 3/4" L copper lines. Ive been reading articles here and there and one point of confusion/debate is the angle of the airlines. There are two trends of thought apparently. I have always thought that you run the air lines uphill, away from the compressor so that any moisture would drain back into the compressor. There is another train of thought that says run them downhill so that the moisture drains to your end of line flush out points. To me that would bring moisture where you dont want it, to your tools, etc.

Also what type of "flexible" line should be used between the compressor and the rigid pipe? Would a hydraulic hose work?

Any comments and added suggestions/websites are always welcome!

Later

SKR8PN · July 06, 2004, 07:55:16 PM

Run the air lines so it drains AWAY from your compressor. The flex line on mine,I had made up for high pressure air. Install a drier with a trap,just off your flex line.Then,install drops below the point of your quick disconnects, with a drains in them. That way,your compressor will trap some air, your drier will take the rest,and your lines will trap any residual,which you can drain,and you are good to go.

jaybee · July 06, 2004, 07:59:29 PM

The installation will be easier, but what's the cost comparison of copper vs iron?

purplepickup · July 06, 2004, 09:08:15 PM

Sharpe Manufacturing has a diagram of my favorite layout http://www.sharpe1.com/dr-pipe.htm . Notice they recommend at least 3/4" pipe with 1 1/4" as optimum. That gives you a lot more air storage. You could even plumb in another storage tank.

I haven't gotten around to plumbing my shop yet but I've thought hard about copper too for two reasons. First, it is durable and easy. Second, it conducts heat really good which means the air gets cooled quicker and more moisture condenses out the further away from the compressor it gets. I'd put my paint run at the furthest point from the compressor.

I'm curious to hear comments about using copper too. I figure cost isn't too much of an issue since this is one of those things you only want to do once and want it to be done good. If it gets too expensive I could do some now and add on later.

Mac · July 06, 2004, 09:36:59 PM

Quote from: "jaybee"The installation will be easier, but what's the cost comparison of copper vs iron?

I'm gearing up for air line plumbing too and recently at the "Depot" I priced 3/4 Schd L copper at $10.99 and 1" iron at $11.99 each 10 ft lengths. Price is about a toss up but think I'm going copper. Ease of assembly, heat disipation and rust free.

Mac

1FATGMC · July 06, 2004, 10:15:33 PM

Quote from: "purplepickup"I figure cost isn't too much of an issue

This couldn't be a statement from the George I know, could it

.

Just kidding George as I'm probably tighter with my money than anyone.

Quote from: "purplepickup"since this is one of those things you only want to do once .

About 6 years ago I had a compressor go bad and it pumped a lot of oil into the lines. I couldn't really get it out so I just used those lines for my air tools and put in new ones that I used with my paint gun.

I'm putting in lines now in my shop and I'm going with the "no-no" pvc. I'm using 3/4" (rated to almost 500 psi) and most of the lines will be covered in a way that it would be very hard to hit them with something.

On a further note the other day I screwed a female pvc fitting to an iron pipe by the compressor and put it on to far so that it caused it to later split while under pressure (my system is only 125 psi). The pvc didn't explode or anything the air just started to leak out the crack that went down the fitting and a couple inches of the pvc pipe. I have now replaced it with a male fitting screwed into a female iron fitting. This way the pvc fitting is surrounded by the iron fitting.

I've used the pvc in the past with no problems, but I know a lot of guys really don't like it.

I do use a "fresh air system" while painting, so I do some safety things right

.

c ya, Sum

58 Yeoman · July 06, 2004, 10:36:23 PM

Before my divorce, I had a 26X32' garage, and plumbed it with 3/4" pvc, and never had any problems, either. I had just used an air hose to connect the compressor to the wall pipes. Now, my garage is 28X28', and I just use a hose reel with a 50' hose.

But, I am interested in a fresh air system. I could probably sneak a Scott Air pack from work, but they are kinda heavy for my kind of work.

Where could I find a 'hobbyist' type system?

1FATGMC · July 06, 2004, 10:55:45 PM

Quote from: "58 Yeoman"
Where could I find a 'hobbyist' type system?

I got a Hobby Air from Len at:

http://www.autobodystore.com/cgi-bin/config.pl?index

I bought the one that is a little larger and is suppose to handle 2 lines (haven't done that) and have been very happy with it.

It was about $450 with the unit, a hood, and two lines 3-4 years ago. I feel much safer painting now and highly recommend getting one. Even the primers are VERY bad for you now.

c ya, Sum

Bruce Dorsi · July 07, 2004, 12:58:57 AM

Quote from: "midnight sun"
I have always thought that you run the air lines uphill, away from the compressor so that any moisture would drain back into the compressor. There is another train of thought that says run them downhill so that the moisture drains to your end of line flush out points. To me that would bring moisture where you dont want it, to your tools, etc.

Also what type of "flexible" line should be used between the compressor and the rigid pipe? Would a hydraulic hose work?

As I understand it, as the hot/warm air travels through the pipe and cools, moisture will condense and drain to the lower end. ....I don't think it really matters too much which end is lower, as long as a drain is incorporated there. However, it seems to me, that if the water and air are moving in the same direction, there is less chance of the water being carried away from the low point.

There should be a vertical pipe "drop" tee'd in at the lowest point, and the drain petcock should be at the bottom of this pipe. ....This pipe acts as a reservoir to (hopefully) keep collected water out of the air lines. I would consider installing one "drop" on each wall where the tubing is run.

Also, it is advisable to take your "taps" for tools off the top of the pipe, as opposed to the side or bottom of the pipe.

Hydraulic hose will indeed work for a flexible connection. ....Since your air pressure will probably never exceed 200 psi, there is no need to go for 1 or 2 wire braid hose, if you can find hydraulic hose with just fabric braid. (Hose used for jackhammers should work well.) ....Too stiff is not good, and some of the wire-reinforced hoses are VERY stiff.

Use 3/4" ID or larger hose, and try to incorporate a 12"-24" hose length.

I also agree with your choice of 3/4" copper. Installation is easier and later modifications or additions are easily accomplished without the need to thread pipe.

If your layout allows, it is desirable to run the pipe in a complete loop around the shop. ...You will have less pressure drop at the "taps" with this layout.

I know Sumner and others have used PVC piping with no problems. .....There IS a PVC pipe which is approved for compressed air lines, but it is more expensive and less common than the run-of-the-mill Schedule 40 PVC from the home centers. .......The biggest problem with the PVC pipe is that the pressure rating drops drastically as the temperature increases. I believe that the common schedule 40 PVC is rated at 74 degrees F. Most compressed air will exceed that temperature by quite a bit. ....Also,the PVC piping will not dissipate the heat as easily as copper.

river1 · July 07, 2004, 02:16:24 AM

just a quick note on the PVC issue. mu local Lowes has a sign on every bin of PVC parts. NOT TO BE USED FOR COMPRESSED AIR

the cost issue is not that big (from what i remember) and ease of installation (to me) is about the same so i went with copper type L.

later jim

sirstude · July 07, 2004, 09:24:45 AM

I have 3/4 copper in my garage. It runs up from the compressor, with a flex line that I had made up at the local CAT rental place. Then it runs around the top of the shop. I have drops that tee from the bottom of the top run that come down to about 3 feet up from the floor. The quick connect tees out of that drop about a foot from the bottom. I have a ball valve at the bottom of the drop down that I crack to drain the water. I came off the bottom of the main line to make sure I got the water to drop out of that line. I don't seem to have any moisture at the tool with this set up. I used copper because I had access to a bunch of it at the time. Also easier to work with for me than iron.

Doug

Bib_Overalls · July 07, 2004, 10:24:28 AM

I used Schedule 80 PVC (the grey stuff). With threaded joints the rating is about the same as glued Schedul 40. But with glued joints the rating almost doubles. White Schedule 40 is not UV resistant. If you use it outside it will get brittle and eventually fail. Outside lines should be threaded iron pipe or copper tubing. Since the air coming out of a compressor is hot the first 10 feet of any system should be iron pipe or copper. PVC lines usually fail at the joints and most often, when the lines are rapidly pressurized. If you use Schedule 40 consider using Schedule 80 fittings at any transition to threaded metal pipe. Schedule 40 fittings will split if you run the tapered pipe threads in to far.

C9 · July 07, 2004, 10:39:37 AM

What do you think about setting up the compressor/air lines with regular air hose?

I'm thinking of going that way in the new garage - which looks to be 24 x 30'.

Compressor with drier at one end of the garage with a vertical galvanized pipe up to the rafters for a moisture trap etc, regular black rubber air hose strung from there, along the rafters to the middle of the garage for a tap to a hose reel, from there to the other end of the garage with another black rubber hose connected to a down pipe with drain valve near floor level.
That end would have the moisture trapped valved pressure regulated pipe manifold which gets bolted to the wall.
Hydraulic hose is used in the pressure regulated manifold as a connector, but the majority of it is galvanized pipe.

Seems like it ought to work.
I've had a black rubber hose connected directly to the compressor for about 15 years.
The hose remains pressurized and neatly coiled.

Nice part about the hose is you can easily reroute it and the other nice part is it's not too expensive.

sirstude · July 07, 2004, 10:42:32 AM

The thing to keep in mind is it takes about 20-25 feet to cool the air enough to get the water to drop out, or so I have read. I would think that the condensation could puddle in the rubber hose where it will droop between the rafters.

Doug

enjenjo · July 07, 2004, 10:57:51 AM

Quote from: "C9"What do you think about setting up the compressor/air lines with regular air hose?

I'm thinking of going that way in the new garage - which looks to be 24 x 30'.

Compressor with drier at one end of the garage with a vertical galvanized pipe up to the rafters for a moisture trap etc, regular black rubber air hose strung from there, along the rafters to the middle of the garage for a tap to a hose reel, from there to the other end of the garage with another black rubber hose connected to a down pipe with drain valve near floor level.
That end would have the moisture trapped valved pressure regulated pipe manifold which gets bolted to the wall.
Hydraulic hose is used in the pressure regulated manifold as a connector, but the majority of it is galvanized pipe.

Seems like it ought to work.
I've had a black rubber hose connected directly to the compressor for about 15 years.
The hose remains pressurized and neatly coiled.

Nice part about the hose is you can easily reroute it and the other nice part is it's not too expensive.

The problem with rubber hose, it insulates the air so well, that it doesn't cool before it comes out the end, leaving a lot of moisture in the air. Not a consideration in the desert, but a big thing here in Ohio.

Parker Hannifin and Weatherhead among others make a nylon plastic air line for trucks in up to 3/4" tube sizes. It's rated for 200 psi at 100 degress C in the larger sizes, much higher pressure in the smaller sizes. It uses compression fittings to connect. You might look into it.