Compressor air distribution piping

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I've just bought a mini-orbital grinder for grinding down welds,using miniFlex discs.Also have 2 new compressors with each having a 200litre tank (+/- 53 Gallons each).I want pneumatic tools now and will try to do spray-painting ,later, after welding panels etc (Mercedes 1959 220 S auto restoration). DRY air is the problem---I wanted to pipe the air through copper piping 42mm ID .( 1.5 inch ) I'll need about 35 m ( 115ft )for the main distribution line. (closed loop)Excluding rises, drops ,tees and drain taps I have been quoted 650 Euro ( 880 USA dollars) for this main distribution line.I have read MANY internet results on Black iron piping, copper, galvanised pipe, rubber hose and PVC (against OSHA regulations in many states ), but can't find a single bit of info on Inox , or stainless steel piping, WHY NOT???Here in Portugal (Europe) I can now buy inox tube at 48mmID (almost 2 inch) with a wall thickness of double the copper piping (at 2mm =0.078 inch ) for HALF the price.Is this Inox tubing not suitable for air supply? Why is it not used more widely?I would sweat the joints with silver solder.Copper prices have rocketed sky high , with other commodities at the moment. Any advice here, would be greatly appreciated.Thanks guys.
Reply:well over here in the us, ss pipe is ALOT more money than black pipe...
Reply:I used to work in a very large factory, full of air tools, a constant whir.  This was a huge company, know globally for their manufacturing expertise.   They did not do things cheaply, they did them right.All their piping was black iron.  They put filters and lubricators under the bench, right where the air tools were plugged in.Stainless should be OK for compressed air, just expensive.   Surprised it could be cheaper than copper.  Are the fittings readily available?I am sure that you know how to put in drops and drains, to keep the water out of the air tools.  I know that my piping accumulates quite a bit of moisture.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:You need to be sure that the stainless carries the same pressure rating as black steel, but I suspect it will.Black pipe is fine for air for tools or painting (although not for breathing), and is more than good enough for your main distribution piping.  Any scale or rust that manages to get into the airstream will certainly be caught by your water coalescing filter, whether you have these filters where you tap out from your distribution, or place one at each bench.  You can use copper or hose downstream of the filter if you're concerned about the cleanest air.
Reply:Thanks for the tip regarding breathing. I have thought of a breathing mask,for painting.I've never heard of Black pipe here, most guys tell me to use galvanized pipe.Is black pipe cheaper than galvanized in USA, or is it better regarding rust or scale?
Reply:Richard,here copper with 42mm ID is 18.55 Euro a meter.Stainless is now, with 48mm ID , 11.00Euro a meter.All fittings are available.( these prices include SALES TAX, at the moment it's running at 23% here.)
Reply:I worked in printed circuit board manufacturing plant, much of our compressed air piping was plastic.  Not PVC but an ABS. I just checked the Ryan-Herco web site: http://www.ryanherco.com/ and a 20 foot length of 1.25" is listed at $6.05.  Very economical when compared to steel or copper metal pipe.Yes, you have to use special cement and fittings and the piping must be installed downstream of the air receiver and cooler.I offer three choices: Good, Fast, & Cheap. You may pick two.Hobart AC/DC StikMate LXHarbor Freight AD HoodHarbor Freight Industrial Chop SawDeVilbis 20 Gallon, 5 HP Compressor
Reply:Here, black pipe is the same as galvanized pipe, except with a black paint coating instead of the hot dip galvanizing for rust protection.  It will rust outdoors, but is used indoors for natural gas, propane, and compressed air distribution, as well as for closed loop hydronic heating or steam heat.  The zinc in galvanizing reacts with the odorant in fuel gases (methyl or ethyl mercaptin, or similar chemicals in that family), so galvanized pipe is avoided, and black pipe is a good bit cheaper too.Stainless is outrageously expensive here (copper is cheaper, and if the cost of stainless plumbing doesn't give you a heart attack, the cost of the fittings surely will), but yes, if it is suitable for the pressure you're using then there isn't much better you can get.
Reply:Thanks for Black pipe details.Regarding ss piping,if the ID is 2inch, would you think that 0.039 inch wall thickness is adequate, or should I go to 0.078 inch (1 or 2mm wall thickness)My orbital mini sander( Wurth) runs at 90psi. Is this normal for pneumatic tools in USA?Painting with HVLP guns.(max 35psi with POR 15 anti rust)Thanks once more.
Reply:I will see if this ABS is available here, it sounds a cheap good solution.Thank you,
Reply:Typical piping used for air distribution is schedule 40 here.  A 2" schedule 40 pipe (or schedule 40s pipe if it is stainless) has a 0.154" wall thickness (almost 4mm).  I know schedule 40 is adequate for your purposes, but cannot speak for thinner pipe.  Maybe someone else here has that information.You can put a regulator at your tank set to 90psi, then have just a filter at each outlet, with a filter/regulator at the HVLP stations dropping the pressure again, which would limit the pipe to 90psi, instead of full tank pressure, if that helps, but I would say that if that small drop makes a difference you're cutting it too close (especially if that regulator fails and starts to creep).
Reply:http://www.engineeringtoolbox.com/st...ngs-d_346.htmlThis site may help you figure out the pressure rating for the stainless steel pipe.   http://www.engineeringtoolbox.com/an...pes-d_247.htmlIf 2 inch schedule 40 SS pipe is rated for 1600 psi at 200F (approx 95C),  and schedule 40 is 3.94mm thick, you can estimate the pressure rating of other thicknesses from that.  I would believe that the pressure rating of the pipe is essentially proportional to the wall thickness, so 2 mm wall pipe would have a pressure rating half that of 4 mm wall pipe, or around 800 psi.Personally, I would not want to use pipe rated less than 200 psi.  You would want some safety factor, given that pressure regulators can leak, and potentially expose the pipe to the full tank pressure.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:Thanks Richard for the link to engineers toolbox.My compressor stops pumping at 150 psi, and I have an outlet regulator which I have set at 90 psi.So I would be well under 800psi or even 200psi.I am sure the SS piping will have markings on them, and will fall under a European norm(which I will check against engineers toolbox)
Reply:Thanks for the info,2mm is definitely the minimum I'll consider