I need to cut and seal off a 1/4 copper pipe (that contains a gas) so that it's air tight. I bought a crimping tool and a cutter. I plan on heating the pipe, then using the crimping tool (which looks like vice grips) to pinch the pipe shut. Next, I will cut it, pinch the end closed, then solder the end. After that, I'll remove the crimping tool. I'd like to do this without letting any of the gas out, or ai in. Will heating the pipe before crimping it help the crimper to seal the pipe, or not? Any other tips that you can offer for this procedure?

Note: This is a hobby project, and the copper pipe contains acetone and a partial vacuum. It's going to be a thermal engine (basically a giant "drinking bird")

More Directions. First, I'm going to solder a valve onto the tube. Then I am going to suck out all of the air in the tube with a vacuum pump, and close the valve. Then I am going to open the valve to suck some acetone into the tube, closing the valve when needed. Then I am going to crimp the pipe, cut off the valve, solder the pipe closed and remove the crimping tool. It's important that I don't lose any of the acetone or vacuum during the final solder step. Also, acetone is flammable and I am using a torch. The crimp seal must be nearly perfect.

  • Suck all of the air out or most of the air? Purging the bird (?!) with nitrogen before evacuating would reduce the opportunity for heartburn.
    – HABO
    Jun 7 at 13:53
  • Heating will not help the crimp action. Jun 7 at 15:14

acetone is stable at typical soldering temperatures, so that sounds feasible,

I would anneal the tube first, clean and tin the inside, clean off the flux residue then fill and proceed as described.

  • Heated with a gas torch or a soldering iron?
    – Solar Mike
    Jan 26 at 8:04
  • 1
    A torch is going to be much easier than a soldering iron, It would probably take about 200 watts to solder 1/4" tube.
    – Jasen
    Jan 26 at 10:18
  • I'm using a torch, so it's important for the crimping tool to completely close off the tube before I solder it.
    – Hoytman
    Jan 26 at 17:59

They do make 1/4" caps that can be soldered on to your 1/4" tubing which would make a better looking job. If the liquid is in the tubing when you are soldering, it may absorb the heat and may make soldering extremely difficult and if the acetone out-gasses or vaporizes from the heat similar to boiling water, soldering may be impossible. If you are preparing the tube before the liquid is inserted then the solder cap would be my choice for a "clean" job.

  • well yeah, you solder the bit that has vacuum (acetone vapour) in it, not the bit with liquid acetone, gravity can help here. best done well away from (other) fuel sources.
    – Jasen
    Jan 26 at 10:34
  • The tube will contain the acetone and the vacuum at the time of sealing. I don't want the acetone to catch on fire, nor do I want to lose the vacuum, which is why I want to use crimping tool. I want the tool to create the best seal possible.
    – Hoytman
    Jan 26 at 17:58

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