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MG MGB Technical - Air Lines Black Iron or Galvanized

I am about to run the air lines in my new shop and am planning on using steel pipe. I had purchased some galvanized pipe and a trusted friend of mine suggested I should have gotten the black iron pipe instead of galvanized. I went the galvanized route thinking this would help minimize the rust build up inside due to the moisture build up as the heated(compressed) air cooled. My friend said the galvanized coating tended to flake off over time. Now I am confused. What is the best to use...black or galvanized?
Frank

And the rust won't flake off the iron piping -- fat chance.

This is a bit off topic but as an engineer respopnsible for the design and build of large steelmill equipment including compressed air systems there can be no doubt that galvanised is the way to go. Rather than fall out with the friend it may be best to say that it is a done deal and you are stuck with the galv.
Iain MacKintosh

Maleable Iron is recommended

The galv coating process will embritle the steel
resulting in lower pressure to burst rate.

However since your not going to push 200+ psi
don't sweat it. In fact I've seen shops run
PVC (gawd why?!) and it holds up to the 120lb
they use there.

iron pipe!! but do use 3/8 - or 1/2 and step
down to a 1/4npt at the coupler so you CAN get
flow at higher cfm's. Use select untyte teflon
thread sealer at the joints...

Cheers!
HowY

Thanks guys for both responses...I had used galvanized on a much smaller scale with no problems. Sounds like both will work fine. The black pipe is cheaper but not by much.
Frank

I used 3/4" nylon tubing with slip-fit and compression connectors. It's the same stuff that's used on large trucks and in industrial appilications. All of the concrete plants that I was around for 18 years used it to good effect. Simple to run, durable (TOUGH AS NAILS AND YOU CAN FORGET ABOUT RUST) and much less bulky than pipe of any kind. Industrial supply houses and truck dealerships carry it. Larger sizes are available, too.
David
David

Error........ I used 1/2", not 3/4".
Dave
David

I had a friend who had run PVC in his shop. He went to bed one night and the next morning he found he compressor running. Went into his shop and found his PVC air line had shattered,leaving sharp scrapnel everwhere, some of it even sticking into the sheetrock walls. No PVC pipe air lines for me, thank you! How ya doing, Howard? Didn't know you came here!
gerry masterman

A couple of other tricks to help with water in the lines.

Run outlet pipe from compressor via a tee connection with a vertical riser on the upper side of the tee, and a dropper with a drain cock below.

Run horizontal pipes with a slight fall to just past the last connection. Put in a 90deg bend with a dropper with a drain cock on the end.

Connect air take off droppers from the horizontal line with tee connections pointing upwards, then use two 90deg bends to come down to your outlet point.

Cheers
Ian F

Ian Fraser

Copper tubing. 1/2" works okay as long as your not running miles of it.
Steve Mc

FWIW...I have found a reference in my TP catalog that sells the bead blasting cabinet that I purchased that they also recommend the black pipe...stating as my friend said that over time the galvanized tends to flake off and clogs up the regulators/filters.
Frank

Gerry, I know someone who suffered the same consequences of using PVC. It was even the expesive green stuff that's supposed to be rated for use as air line.

David, the major downfall of PVC for air use is that PVC doesn't absorb the heat from compressed air as quickly as metal piping. This allows a higher concentration of moisture to enter your tools.

Personally, I have 3/4" copper lines in my shop. They are silver-soldered (brazed) together and are well protected from damage. I run 175psi and would rather have black iron, but it wasn't in the budget at the time.
Jeff Schlemmer

This thread was discussed between 22/04/2004 and 26/04/2004

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