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  • Compressor Plumbing

    I am planning to run air overhead in my shop for greater access when using my air tools. I plan to use 3/4" copper water line which I have left over from removing a hot water baseboard heating system years ago. Is there any reason that I cannot use compression fittings to connect the sections of copper? I would rather not do any soldering in the rafters if I can avoid doing so. Will using 3/4" pipe have any effect on my pressure or volume? Where should I mount the regulator, at the compressor tank or where the rubber hose attaches to the copper tubing? My compressor is a 3 hp 220 volt 20 gal roll-around unit.

  • #2
    I can't see any reason why you couldn't use compression fittings. These fitting carry a higher WOG(water, oil, or gas) pressure rating than you're likely to be using.

    Using ¾" tubing will also not cause any problems for you either. As a matter of fact, it will actually add a little bit of capacity to the compressors storage tank, how much depends on how long of a run the tubing is.

    I think I would mount the regulator at the compressor.
    I decided to change calling the bathroom the "John" and renamed it the "Jim". I feel so much better saying I went to the Jim this morning.

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    • #3
      Not sure what the suggested working pressure is for copper pipe but it was suggested to me that I use type K copper (thick wall stuff) especially true if you have a high pressure compressor (175 PSI)

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      • #4
        Thiggy,

        I would NOT use regular copper pipe (either rigid or soft) because you run the risk of splitting or blowing out which can be dangerous! I believe that standard water or gas type copper pipe is not rated for the higher pressure that most compressors put out. In most compressor installations, iron pipe is employed. Even where thick wall copper (I'm not sure of the schedule type) is used, it is usually only in fairly short lengths.

        I've worked in a compressor manufacturing plant for thirty years (Technical Publications and Marketing) and the only place where I've seen copper pipe (rated for high pressure) is on interstage connections. Over the last several years, that has pretty much been replaced with armored flexible hose.

        Iron pipe would be best, but also take into consideration how you run the pipe. You must take into consideration that any compression of air will result in moisture separation. The warmer the air, the more moisture and especially in humid conditions, it can be a major problem, even in a small compressor. Pipe should slope away from the compressor exhaust connection and drain legs with drain valves need to be installed in any position where moisture might be collected. You must guard against any possible moisture from draining back into the the compressor cylinder as it will damage the running parts (water does not compress). Similarly, condensation can build up in any low spot in the piping and cause corrosion; hence the need for proper slope and drainage.

        Hope this helps,

        CWS

        Comment


        • #5
          COPPER TUBING, EITHER TYPE M/(THIN WALL), L (MIDDLE WALL) OR TYPE K (THICK WALL) CAN MORE THAN HANDLE THE PRESSURE. IN FACT THE BURSTING PRESSURE ON THIS PIPE IS APPROX. 1100 PSI ON TYPE M. THE PROBLEM IS IN THE COMPRESSION FITTINGS. THEY WILL WORK FINE IF YOU KEEP THEM AWAY FROM VIBRATION. I SUGGEST THAT YOU USE A STAINLESS STEEL BRAIDED WATER FLEX BETWEEN THE COMPRESSOR AND THE COPPER. 2' WOULD BE GOOD. SAME AS USED ON A WATER HEATER. APPROX COST $7. AS FAR AS THE REGULATOR GOES. IF YOU HAVE MULTIPLE OUTLETS IT WOULD BE LESS EXPENSIVE TO USE 1 REGULATOR AT THE START OF THE SYSTEM, JUST AFTER THE STAINLESS FLEX CONNECTOR. FOR THE BEST PRESSURE CONTROLL IT'S BEST TO HAVE THE REGULATOR, FILTER, OILER AT THE OUTLET OF THE SYSTEM . IT THEN CAN BE ADJUSTED TO THE EXACT PRESSURE WITHOUT THE NEED TO ADJUST FOR FRICTION LOSS. THIS WORKS BEST IF YOU ARE USING MINIMAL OUTLETS. THE 3/4'' WILL ADD VOLUME TO YOUR SYSTEM. CAUSING YOUR COMPRESSOR TO START LESS, BUT RUN LONGER. ALL DEPENDS ON HOW MUCH PIPE IS IN THE SYSTEM. NOT TO WISE TO REUSE DIRTY PIPE AS THERE ARE COTAMINENTS IN THE PIPE THAT THE FILTER WILL HAVE TO CATCH. COPPER IS NOT THAT EXPENSIVE. COMPRESSION FITTINGS FOR 3/4'' ARE. WHY NOT USE HEAVY DUTY AIR HOSE, SUCH AS FROM A JACK HAMMER 3/4''. APPROX. $.75 CENTS A FOOT. CHECK EBAY. WORKING PRESSURE APPROX 150# BURST PRESSURE APPROX. 4X GREATER. IT WILL BEND AROUND YOUR WALLS AND BE MUCH EASIER TO WORK WITH. COPPER WILL LOOK BETTER, HOSE WILL BE FASTER AND LESS EXPENSIVE. PLUS NO VIBRATION PROBLEMS. BRASS BARBED FITTINGS AND SOME HOSE CLAMPS WILL WORK GREAT. BRASS TEES TO SPLIT THE SYSTEM. SAVE SOME MONEY AND USE 1/2'' UNLESS YOUR RUNNING HIGH VOLUME TOOLS. GOOD LUCK PLUMBER RICK.

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          • #6
            CWS, I have to disagree with a lot of what you have said here. The use of copper poses no increased risk of a catastrophic system failure due to pipe bursting as you suggest, for PVC yes, but not copper. PVC is very unsafe for compressed gas use, don't even test a water system with compressed air. This 'time saver' could cost you your life. Filling a liquid system with water or other inert fluid compatable with the process fluid and then apply pressure using compressed air, but don't fill a PVC system with nothing but air, even a small volume home water system, and pump it up with air.

            You may have worked for a compressor manufacturer for 30 years, but I have worked on the installation and maintennace of large (systems powered by 3 400HP 5400CFM compressors and miles of pipe using both your "recommended" iron pipe and copper systems) and small compressed air systems for the past 28 years. In all that time the systems piped using steel pipe have required 20x the maintenance that the comparably sized copper system has.

            Both these systems were thoroughly cleaned during startup and cleanliness was ridgidly maintained during construction. the steel pipe system has been in service since 1977, and is one big PITA for our maintenance dept. The scale and rust (even though we use multiple cascaded air dryers) takes its toll on pneumatic instrumentation as well as valves and similar components in the system. Lower elevations tend to collect the majority of the rust, scale, and mositure, plant personell must periodically blow down these lines to keep them clear. We replace many parts due to wear from the grit (small scale and rust particles carries in the air) in instruments as it acts like blast media pitting the flapper and enlaring orifices which affects calibration settings and performance.

            On the other hand, the system piped in copper (BTW, our engineers choose to use K copper and silver solder all connections for a system running a normal pressure of 110 PSIG) has had very few problems in almost the same span of time (in service since ~1985).

            My choice for a home shop system would be 1/2 or 3/4 'L' copper using 95/5 solder. Stainless steel flex connections between rotating equipment and ridgidly mounted piping are a must as PlumberRick said. I agree with a regulator mounted first in the line which establishes overall system pressure and then followed by locally mounted regulators to step down pressure for each work station or equipment, adding water seperators/oilers as required to support the equipment used at the location. This keeps our system piping free of oil, provides better control of supply line pressure(no compensating for line loss as Rick said), and minimizes maintenance headaches.

            Your guidance on sloping pipe runs, water seperators, etc. I agree with you on, it does not matter what material your system is piped with if you do not install it correctly. All taps/branches off horizontal mains should be taken off the top or as close to as possible. Drops should have drip legs with full size drain valves (1/2" valve on a 1/2" drop).

            I really like the steel piped systems, they have provided much work for me. I have probably made enough money off maintenance and repairs performed on the systems piped with steel over the years to by a new pickup this year.


            Originally posted by CWSmith:
            Thiggy,

            I would NOT use regular copper pipe (either rigid or soft) because you run the risk of splitting or blowing out which can be dangerous! I believe that standard water or gas type copper pipe is not rated for the higher pressure that most compressors put out. In most compressor installations, iron pipe is employed. Even where thick wall copper (I'm not sure of the schedule type) is used, it is usually only in fairly short lengths.

            I've worked in a compressor manufacturing plant for thirty years (Technical Publications and Marketing) and the only place where I've seen copper pipe (rated for high pressure) is on interstage connections. Over the last several years, that has pretty much been replaced with armored flexible hose.

            Iron pipe would be best, but also take into consideration how you run the pipe. You must take into consideration that any compression of air will result in moisture separation. The warmer the air, the more moisture and especially in humid conditions, it can be a major problem, even in a small compressor. Pipe should slope away from the compressor exhaust connection and drain legs with drain valves need to be installed in any position where moisture might be collected. You must guard against any possible moisture from draining back into the the compressor cylinder as it will damage the running parts (water does not compress). Similarly, condensation can build up in any low spot in the piping and cause corrosion; hence the need for proper slope and drainage.

            Hope this helps,

            CWS

            Comment


            • #7
              Bob D,

              I stand corrected. Certainly your experience in actual installation stands far above mine. I was going by data and experience as it came to me as as a technical illustrator and writer of our product support manuals. While I've taken the same classes that our field service technicians and I've worked closely with both engineering and field service operations there simply is nothing better than working in the field. Perhaps I've missed something there, but I don't recall ever seeing any recommendation for copper pipe used in an installation. But of course, that doesn't mean that it doesn't happen and perhaps in petro-chem industry installations (which is where my last 20 years have been focused) there are other considerations. Either way, you are absolutely correct on the scaling and maintenance problems that steel pipe presents in large factory installations.

              So my main concern, based on what I knew, was that Thiggy didn't put himself in "harms way". Thanks for keeping me "up-to-date" and providing more in depth explanation. It is appreciated. I'll touch base with some of my old field service friends to further update my thinking.

              Thanks,

              CWS

              Comment


              • #8
                OK on the refinery applications CW, I have worked in those places too (DuPont, Hercules Chemical, Mobil, Sunoco, etc.) and there they do use steel to a large extent. I think mostly because of the harsh enviroment from caustic gasses and fluids, copper would not hold up well in these installations.

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