Bending black iron pipe....

Hey Gang,

I'm in the thinking stage of designing my air supply piping for the new shop. For simplicity and lower cost, I'm planning in using black iron pipe for this. Most things I read says that a long radius elbow will result in less pressure drop at the end of the line. Problem is, none of the plumbing supplies I've talked to know of any "stock" item of this description. One did offer a solution of obtaining some seamless, having it male threaded on the ends, and then having it bent. Gonna cost me some $$$$ compared to regular elbows.

Anyhow, I've got a few thoughts on how to tackle this....

1) Given a large enough radius, is it safe to bend standard black iron pipe? Let's say 1.5 foot radius. (175 psi worth of air inside)

2) Use two 45* elbows about a foot apart to complete the 90* bend.

3) Just design a loop system and forget about it. (loop means that air comes from 2 directions to the point of use.) I can put all the high use stuff closer to the compressor to eliminate the pressure drop where I need it.

So, what say you guys? Am I taking too many hits from Dan's crack pipe, or do you have some suggestions?

TIA

 

By long radius they are talking butt weld fittings and not threaded. You can get them in all kinds of different radiuses (or however you spell it) but for an air line I wouldn't worry too much about it.

We went with PVC pressure pipe on our air lines because it is a whole lot cheaper and will not rust, but I have also done several in black and galvanized pipe. The main shop I work out of is the one I did the PVC lines in and we have had it in there for nearly three years without a single problem. I use a paint gun from it pretty regularly with a regulator on the gun and have never had any issues with loss of pressure and we have just standard 90's and tees in the line. As far as bending, as long as it is done right you shouldn't have much problems with it on the black pipe, but it can sometimes weaken the seams of std black welded pipe.

For my part, even though I sell black pipe here, cost wise I will never do another one with steel. Just my .02.

 

I humbly submit the following, courtesy of TP Tools...they have lots of air line supplies.

 

Thanks Ron, I am familiar with TP. That's what started all of this!

 

From the looks of it there, judging by the tees, they are just using the standard radius on the 90's and they have a flex hose from the compressor. I you are worried about pressure loss, you might look into a stiff flex hose for the bends to give you a longer radius. Knowing how machine shops charge for bending and threading, it might be cheaper going the flex route. Like I said though, I have never had any issues with pressure loss, especially if you use 3/4" or 1" pipe and you consider the fact that if you run a good bit of pipe it is like having a bigger tank and helps your compressor out quite a bit.

 

Old Bill

I am in the air compressor industry.
We use a lot of copper pipe TYPE L for are plumbing, go one size larger than the outlet on the compressor tank, a loop system is grate if you have a shop full of people.
Use standard elbows and tee,s 95/5 solder. flex line at compressor
Take the drops off of the top of main line to help with water getting into you tools.

PLEASE DO NOT USE PVC PIPE BECAUSE IT CAN EXPLODE, AND OSHA AND THE FIRE DEPT WILL NOT ALLOW IT.

Andrew
Rio Rancho New Mexico USA

79 CJ6 134/T90/D18 Warn od

 

This is very true depending on how you run it. Cost was a big issue for the guy in the case where we used it though and copper was also out of the question.

 

From what I've read, I'll be using either black iron or copper. Copper would be a definate if I were in a more humid climate, but as it is, I believe that I can get away with black iron with a little maintainance. Thanks for the advice on the elbows and T's.

 

Bill, I'm a Ind Pipefitter by trade, if you're wanting to keep the pressure up go with a larger dia. ,say 1" ( or larger as this also becomes a resevoir)for the run from the compressor all around the shop,use 45deg elbows in corners and 3/4" drops at work stations.Galvanized pipe has less friction drop than galvanized also and will give you cleaner air.

 

Uh, did you mean to say something slightly different?

Thanks for the input guys. I know that it's just a guy's garage, but I wanna do this RIGHT. Point of pride you know!

 

I think he meant that Black iron pipe will have less friction than galvanized pipe. It will give you cleaner air because the galvanize on the inside of the pipe can tend to flake off which is also the reason you never use galvanized for LP/Natual gas piping. It flakes off and clogs up the gas nozzles.

 

What I meant to say was galvanized has less friction drop than black pipe.The condensation that forms in pipe leads to rust in the black.The fire protection gurus,Viking ,Grinnel and Industrial Insurers have "RECOMMENDED" that we use galvanized pipe because of the fact it has less friction drop.Any new fire protection sprinklers that we put in has to be in galvanized pipe.
I cant give you the mathmatical figures, just what the 'Gurus' (engineers)told us.

 

NOW you tell me about the bigger 1" pipe acting as an air reservoir! After I just bought a buttload of 1/2" pipe and fittings!

And how many of us really have to worry about "friction drop" affecting our garage tinkering?

 

Ron, if you only plan on running under 50 feet or so, then you'll probably never even notice. I'm only going this way because I plan on running air all around the shop (for convenience), and that's going to be about 125' or more. That, and I have a bad habit of totally overthinking/overbuilding/overengineering everything I get into.... R)

 

That's not necessarily a bad thing, you're a man after my own heart! I was just thinking, Jeez, worrying about the air pressure/volume loss from the friction of the air moving through the pipe? (That IS what you're talking about, right?) In a production shop using lots of air at lots of work stations, sure, I can see that. I think the 1" pipe is a great idea, but not from the friction aspect. In my little dinky garage, and for what I'll be doing, I think I'll be fine with the 1/2" pipe. If I have a 20' long system, that'll be a miracle. More like 12' -15'.

How big a shop are you building? (You lucky s.o.b. you!)R)

 

24' x 36'. Yes I am!

I wasn't really TOO worried about friction/pressure loss, but I knew I was going to be putting air around the perimeter of the shop and wanted to be sure I wasn't putting unnecessary restrictions either. I've settled on 1" around the perimiter with 3/4" drops every 5' or so in the main work area, and a couple in the car bays. (in case I wanna air up the tires, I have a hose right there.) Kinda like outlets, it's difficult to have too many.

 

kinda on topic...regarding the 1" black pipe that is....
got tired of blowing out/breaking those cheesy aluminum lawn chairs.
friend made up 3 or 4 of these for our sand dune group.
no more rivet blowouts, no more chair blowing over into the fire ring, no more inconsiderate duners ruuning over our chairs (without major damage to their machine)
that's right, folding chair made out of 1' schedule 80 black pipe and bed frame rails
needs new webbing, about 20 years old now, just couldn't bear to throw it away
oh yea, it weighs about 20 lbs (without the webbing)
hard to haul around to say the least
when you have the time Thad, bend one of these up
for the ECJ5er who has everything

 

So did any duners run over one of those? R)

 

nope