Announcement

Collapse
No announcement yet.

compressed air lines - copper unions

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • compressed air lines - copper unions

    I am installing a compressed air system in my small shop, using 1/2 inch copper. In the past I have used the copper unions in the piping around the filter regulator on the compressor outlet. Thinking I would be able to disassemble if needed to repair or change out the regulator. I haven't been able to get the unions leak tight. Is there a trick? They should make-up without any dope or tape on the big nut, right?
    Thanks

  • #2
    yes they should, but unfortunately most are made overseas and the quality control is not the greatest. Sealant or tape on the threads will work and lapping the sealing surfaces will help also. extra work that you shouldn't have to do but it's luck of the draw anymore. Jim

    Comment


    • #3
      I usually paint a little pipe dope on the mating faces, which seems to do the trick.

      Comment


      • #4
        Originally posted by jmm03 View Post
        yes they should, but unfortunately most are made overseas and the quality control is not the greatest. .....
        I expect so. I have found iron pipe fittings that leaked, both around the (malformed) threads, and right through the iron... Made in "cheap labor" countries, of course.
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #5
          Okay, here's the hot setup in my shop..... SharkBite fittings. I have both copper, and a run of PEX tube. They're the push to lock type, sealed with an oring . There's a release ring for disassembly. No Leekey. They also work on pvc pipe. Or so they claim, I don't use pvc. There's several brands at the different outlets.
          I cut it off twice; it's still too short
          Oregon, USA

          Comment


          • #6
            Thanks, guys. I will try the smear of dope on the mating surfaces; if that doesn't go well, I will cut off the unions and go with the shark bite. I didn't realize the shark bite could be de-coupled. That seems like a good approach.

            Comment


            • #7
              Any dings in the sealing faces will result in a leaker. Inspect before you buy.

              Comment


              • #8
                I was taught to anneal (red heat) the union seats......….then assemble dry.
                BudB

                Comment


                • #9
                  Just finished a similar job (in 3/4). Union was leaking when done. Let it run for a few hours and retightend it, all good.

                  Comment


                  • #10
                    lap the unions. chuck them in a lathe and run them in for a few seconds with brasso or some other consumable abrasive such as comet or bon-ami.

                    Comment


                    • #11
                      Throw an O-ring in it.
                      I just need one more tool,just one!

                      Comment


                      • #12
                        Originally posted by wierdscience View Post
                        Throw an O-ring in it.
                        You'd probably need to cut a grove in one of the faces to constrain it.

                        Comment


                        • #13
                          These are compression fittings, correct? The ones with a two threaded parts and an additional little piece between them? Don't put any teflon tape or any other sort of goop on compression fittings, at best it won't do anything. The seal is made with that little cone or ball that goes on the end of the tube. It grips to the tube then presses up against the inside of the fitting. When I screw these up usually I didn't get the little cone/ball to seat straight, and it wasn't clamping onto the tube properly. That or I pushed the tube in too far, preventing the little ball/cone from seating on the fitting. The former requires a new little ball/cone, but the latter can be remedied by taking a little bit of the stickout off with a dremel. I have also seen some fittings where the mating surfaces were bad, but it was really obvious like a large dent or gouge.

                          Comment


                          • #14
                            Unions do have a preferred direction, the flow should come out of the nut side. Installing them backwards can cause leaks in high pressure systems. Also, 1/2 inch does limit your airflow, 3/4 will handle more than twice the flow. Keep your lines short and you should be alright with half inch.

                            Comment


                            • #15
                              Originally posted by AssertiveWall View Post
                              These are compression fittings, correct? The ones with a two threaded parts and an additional little piece between them? Don't put any teflon tape or any other sort of goop on compression fittings, at best it won't do anything. The seal is made with that little cone or ball that goes on the end of the tube. It grips to the tube then presses up against the inside of the fitting. When I screw these up usually I didn't get the little cone/ball to seat straight, and it wasn't clamping onto the tube properly. That or I pushed the tube in too far, preventing the little ball/cone from seating on the fitting. The former requires a new little ball/cone, but the latter can be remedied by taking a little bit of the stickout off with a dremel. I have also seen some fittings where the mating surfaces were bad, but it was really obvious like a large dent or gouge.
                              No, sweated unions like this
                              https://www.amazon.com/Everflow-Supp...s%2C285&sr=8-1

                              Originally posted by Jerrythepilot
                              Unions do have a preferred direction, the flow should come out of the nut side. Installing them backwards can cause leaks in high pressure systems.
                              Thanks, I didn't know that.

                              Comment

                              Working...
                              X