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  • Shop air distribution plan

    Early in the New Year the plan is to wire in the big compressor I was GIVEN (Howzatt for a tool gloat ) and plumb some distribution to a few key areas of the shop.

    After looking at the options I've decided on 3/4" Schedule 40 plastic for the main runs with 1/2" Sched 40 or perhaps switch to PEX for the one lighter duty 35' run off one end of the L and across to the pedestrian door. The use of that run will be primarily topping up vehicle tires but it will also be used for some lighter to medium duty air tool use. If I need more then the welding area end of the main 3/4" run is easily accessed by opening the vehicle door.

    There is also a plasma cutter in my near future so that's partly the reasoning for the 3/4" main runs.

    The Sched 40 plastic pipe choice is pretty much chiseled in stone. I don't want to deal with possible corrosion issues with black pipe and I don't want to pay for copper. And Pex does not have as good a working pressure with the 3/4" size being just a bit too close to what I would like to be able to run in the pipe and the idea that the fittings fit into the pipe and thus create a bit of a restriction. And it's all bendy instead of nice and straight... .

    The compressor will sit in the corner of the shop in what was supposed to be the under bench open concept "storage" area. I'll also be closing it in with a couple of sound reduction panels and an intake muffler.

    The distribution is as follows;
    1. Compressor feeds into the middle of the 3/4" main distribution "L" with one leg 18.5' and the other 24'.
    2. A 1/2" run off one end of the main L will extend roughly 30' to the pedestrian door to be used primarily for topping up tires and light to medium air tool use. If I need lots of air I can open the vehicle door to access an end of the main 3/4" run with a suitable hi flow fitting that will also be used with the plasma cutter.
    3. The main run legs will terminate with a T that has a condensation collector stub off the lower side with a bleed valve. The air will come off the upper side. I'll extend the upper side up off the main run by at least a few inches, more likely a foot or bit more, to aid with encouraging any condensation to run down into the collector stub.
    4. There will be a couple or three fittings off the main "L" at key points. I'll use reducing T fittings with their outputs off the upper side.
    5. The main "L" will have both legs sloped by some amount between 1/8 and 1/4" per foot to encourage any condensation to run to the end and be collected.
    6. The main run legs will be sloped between 1/8 and 1/4" per foot towards the ends to encourage any condensation to flow outwards and into the collector stubs.



    So now the question.... Do any of you see any glaring errors or omissions in this plan?

    The other part of the plan is that I'm going to have multiple connectors on the ends to allow for installing local regulators for light duty air use but still have easy access to the full line pressure which I'm planning on running at around 90 psi. The direct line connectors will likely also be fitted with ball shutoff valves since I've wrestled with trying to connect dry break connectors at high pressure and it can be rather comical at times...

  • #2
    I pulled up a video from back in 2005 which shows the air system I built with black iron. I would feed one end of your air system with the compressor (vs. feeding the middle) because the longer the run, the more time and chance for the moisture to condense on the inside of the piping. Also, if you look at my system, it's always going down-hill and any water will end up in one of the many drip legs. Also, all drops rise up and off the main feeds. Even each regulator rising up again and off each branch.

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    • #3
      I'd probably do sch 80 as it has a 50% higher rating, but I'm sure sch 40 would be fine.
      "Let me recommend the best medicine in the
      world: a long journey, at a mild season, through a pleasant
      country, in easy stages."
      ~ James Madison

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      • #4
        And here is what I used as a guide when I built my system. Notice all of the rise-ups everywhere to help drop moisture from the air.. This is what I should do again in my new shop, but not interested in doing all of that black iron pipe work again. I got my black iron pipe work fix installing my shop heater so all set with that for now

        Last edited by 3 Phase Lightbulb; 12-12-2017, 06:24 PM.

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        • #5
          Holy Crap!
          DO NOT USE PVC PIPE FOR AIR! It is not legal because it is dangerous. When PVC fails under pressure it does so explosively! I have had PVC pipe burst from air in lines causing water hammer that created a high pressure. PEX is crosslinked polyethylene that tears erraticly relieving pressure slowly.

          Please be safe.
          P

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          • #6
            Who mentioned PVC???
            Location- Rugby, Warwickshire. UK

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            • #7
              I believe PVC is actually the strongest plastic pipe. You can get 600psi SCH-40 pipe.

              Here is some cheap 1/2" SCH-40 PVC pipe rated at 315psi

              https://www.lowes.com/pd/Charlotte-P...ipe/1000080799

              EDIT: Sorry, wrong link!!!
              Last edited by 3 Phase Lightbulb; 12-12-2017, 07:41 PM.

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              • #8
                Originally posted by Mark Rand View Post
                Who mentioned PVC???
                Sched 40 plastic...what else might it imply?

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                • #9
                  Originally posted by Mark Rand View Post
                  Who mentioned PVC???
                  The OP did.....

                  Originally posted by BCRider View Post
                  ......

                  The Sched 40 plastic pipe choice is pretty much chiseled in stone. I don't want to deal with possible corrosion issues with black pipe .....
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #10
                    Originally posted by 3 Phase Lightbulb View Post
                    I believe PVC is actually the strongest plastic pipe. You can get 600psi SCH-40 pipe.
                    ...
                    Yes, but not for compressed gases! "Illegal" for that. The dangers are probably greatly exaggerated, but it true that when it fails, it shatters into shrapnel like pieces. Makes me nervous and I'm not at all a safety weinie.

                    Bob

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                    • #11
                      I would not worry about the PVC pipe bursting, but I would be worried about the joints not holding. It seems PVC pipe joints that are not threaded rely completely on the glue alone to hold slip fittings together(?) Do they make special glue when using PVC pipe for long term pressure applications?

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                      • #12
                        Originally posted by Bob Engelhardt View Post
                        Yes, but not for compressed gases! "Illegal" for that. The dangers are probably greatly exaggerated, but it true that when it fails, it shatters into shrapnel like pieces. Makes me nervous and I'm not at all a safety weinie.

                        Bob
                        They sell PVC pipe specifically for pressure applications. They also sell PVC pipe not rated for pressure applications.

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                        • #13
                          Originally posted by 3 Phase Lightbulb View Post
                          I would not worry about the PVC pipe bursting, but I would be worried about the joints not holding. It seems PVC pipe joints that are not threaded rely completely on the glue alone to hold slip fittings together(?) Do they make special glue when using PVC pipe for long term pressure applications?
                          With hard PVC it really is less "gluing" and more "solvent welding". Section a joint sometime.
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #14
                            Originally posted by 3 Phase Lightbulb View Post
                            They sell PVC pipe specifically for pressure applications. ...
                            I don't think so. I couldn't find any by Googling "compressed air PVC". Only prohibitions against it. There are other plastics rated for compressed air. Maybe I wasn't searching on the right terms & maybe you have a link(?).

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                            • #15
                              My shop air is distributed by 1/2" sch. 40 PVC pipe. I installed it 25+ years ago - not a single problem. I used the regular purple primer and PVC glue. The regulated pressure in my shop is 100 psi, the unregulated (for the sandblaster) is 145-175 psi.

                              In response to the usual hysterical screams about "deadly shrapnel" on RCM I conducted a test. After donning appropriate safety gear (motorcycle jacket and helmet) I whanged one of the down legs with a hammer. Had to hit it twice before it broke. The PVC shards flew as far as 10 feet. Sharp edges, but not something you could cut yourself on.

                              Ho hum.

                              -js
                              There are no stupid questions. But there are lots of stupid answers. This is the internet.

                              Location: SF Bay Area

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