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Fusable plug for 5″ gauge

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Fusable plug for 5″ gauge

Home › Forums › Locomotives › Fusable plug for 5″ gauge

Viewing 10 posts - 1 through 10 (of 10 total)
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  • 15 April 2015 at 07:21 #186440
    andrew winks
    Participant
      @andrewwinks64215

      Hi all, anyone with experience making a fusable plug for a copper boiler firebox?

      I have a 3/8 ME bush in place in the crown. The plug I believe is drilled and filled with low(ish) temp soft solder but I've also heard of some with a copper rivet sweated in. Advice greatly appreciated.

      15 April 2015 at 07:21 #1392
      andrew winks
      Participant
        @andrewwinks64215
        15 April 2015 at 10:21 #186451
        Dave Bond 1
        Participant
          @davebond1

          The copper rivet is I believe designed to blow out leaving a large hole. Just filling with soft solder there is a small risk that the plug re-seals as it cools during pressure release as not all solder would be ejected from the plug.

          15 April 2015 at 10:30 #186453
          Steambuff
          Participant
            @steambuff

            I don't think the plug would reseal if you filled it with Solder or (usually) White-Metal as it would drop into the fire as it melts and the pressure would tend to blow it into the fire as well.

            Dave

            15 April 2015 at 11:34 #186460
            Neil Wyatt
            Moderator
              @neilwyatt

              I think the head of the rivet inside the firebox is stop stop the fire eroding away the plug.

              15 April 2015 at 12:39 #186468
              andrew winks
              Participant
                @andrewwinks64215

                I agree Dave, once the solder softened and gave way, steam blow would continue until the boiler pressure dropped to atmosphere. Yes, Neil, I would agree the rivet would protect the caulk. My thoughts would be a 1/8" copper rivet sweated in a very sloppy clearance fit in the corresponding hole drilled in the gunmetal plug. Solder, perhaps comsol, gets the highest temp.

                15 April 2015 at 12:58 #186471
                JasonB
                Moderator
                  @jasonb

                  All the posts I have read in the past on traction engine forums say solder is a NO NO. The Aussie code is tin for presures upto 150psi and pure lead over 150psi.

                  J

                  15 April 2015 at 13:15 #186477
                  Paul Lousick
                  Participant
                    @paullousick59116

                    Extract from Australian model code for boilers. (max. pressure for models is 100 psi)

                    fusible plugs.jpg

                    Tin melts at 232 °C (450 °F) ,    Lead melts at 327.5 °C (621.5 °F)

                    Paul.

                    Edited By Paul Lousick on 15/04/2015 13:19:45

                    15 April 2015 at 13:24 #186478
                    andrew winks
                    Participant
                      @andrewwinks64215

                      Thanks Paul, I do have a copy of the Au code but wondered where tin could actually be sourced. Thats why i was also thinking solder with high tin content.

                      15 April 2015 at 13:26 #186479
                      andrew winks
                      Participant
                        @andrewwinks64215

                        My comment earlier about comsol is certainly incorrect, melting temp too high

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