Soft copper tubing?

Discussion in 'General Engine Discussion' started by Shopgeezer, May 12, 2019.

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  1. May 12, 2019 #1

    Shopgeezer

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    So in looking for brass and bronze tubing for steam engines and boilers (which is expensive and hard to bend) I came across soft copper tubing for HVAC use. This is available in large rolls and is cheap and easy to bend. Is there any problem using the soft copper tubing for a steam installation? I would think that it could take pressure well.
     
  2. May 12, 2019 #2

    kwoodhands

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    I think your soft tubing would be ideal. If I had some on hand it would have saved me time and trouble. I tried to bend a 90° bend with 7/32 copper pipe. Used a small tubing bender made for it. After kinking the pipe 3 times I annealed the pipe and still kinked it. Then filled the 10" long pipe with 60/40 solder and then made a successful bend. Real PITA to fill a small pipe with solder. I could only by tubing locally in 100'-0" rolls but had the pipe on hand. Now I have a nice blob of solder with no use for it.
    mike
     
  3. May 12, 2019 #3

    Shopgeezer

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    On one of these threads a fellow mentioned Cerrobend for filling tubes for bending. It is a low temp metal that will melt in boiling water, and can be reused many times. I found some on Ebay in various forms. Small ingots are around $12 each. I think I will order some in case I have to bend hard tubing. Might want to build an exhaust for a V 12 engine someday.
     
  4. May 13, 2019 #4

    retailer

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    The 'soft ' copper tubing sold for HVAC use is I believe just plain copper tube that has been annealed - it stays soft for few bends and gradually work hardens and then needs to be annealed to bring it back to a 'soft' state. I have a few meters of this tubing left behind by the guys that installed our ducted HVAC system, the work hardening can be felt as you bend the tube back and forth a few times it gradually becomes harder and harder to bend.
     
  5. May 13, 2019 #5

    Charles Lamont

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    Copper is the thing to use for steam piping, not brass or bronze. Your HVAC tube may not be suitable for firetube boiler flues though, as it may well be too thin for significant external pressure. In some jurisdictions only certified materials can be used to get a boiler certificate.
     
  6. May 13, 2019 #6

    chrsbrbnk

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    a lot of these questions need the size of the boiler and the pressures you intend to run. then comes the question of where your going to run it
     
  7. May 15, 2019 #7

    Shopgeezer

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    Well the boiler will be somewhere around 6”X 3” and no more than 50 lbs pressure. Polished wood display stands at first but my ultimate aim is RC steam boats up to about 60” keel.
     
  8. May 15, 2019 #8

    Rod Cole

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    HVAC I think will be "L" gauge which is second heaviest there is still "K" which is even heavier (thicker). K is usually used underground for water supply. From reading I am to believe L would be good enough for 100 lbs of steam pressure. But before you build it's not that hard to find facts for the materials needed. Being K, in my experience was used for underground water, I can't say much about small sizes. We were using 3/4" and 1".~
     
  9. May 16, 2019 #9

    Shopgeezer

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  10. May 16, 2019 #10

    Rod Cole

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    You might still want the Cerro-bend (or how ever it's spelled). You forsure don't want to freeze water in copper to bend it. Having spent many years in the plumbing business, I've replaced plenty of copper tubing that froze, expanded and then split lengthwise. I've used those benders and they're fine if you don't need to tight a radius~
     
  11. May 17, 2019 #11

    BruceInSD

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    I have used Cerrobend and it is dead easy to use. I got a pound for $15 on eBay. That is a lot because it is reusable. Annealing is important as well. I had been told that not annealing was my problem. It didn't work the first try because I never got it above the annealing temperature. Most alloys of copper need to get above 700 F or 400 C . My rule of thumb is just barely red. As soon as I see red I move on.
     
  12. May 17, 2019 #12

    Shopgeezer

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    I would think that the soft copper HVAC tubing wouldn’t need annealing, at least for the first few bends. I expect that it would work harden so a lot of bends in a tight space would probably require annealing.
     
  13. May 19, 2019 #13

    Kenny Broomfield

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    For bending pipe I've always heard of filling with sand capping both ends and bending. I have not used this though on small pipe below about 1 inch myself, so I can't day how it would work although I've no reason to suspect it would not.

    Kenny
     
  14. May 21, 2019 #14

    TSutrina

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    My father said that it is impossible to get the sand out of the tube because some grains may be sharp and create a pocket and are stuck to it. He used salt which is soluble in water and as a crystal shape is known and very strong.
     
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  15. May 22, 2019 #15

    Andy Munns

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    I worked on steamships and sand bent steam and water pipes in steel and copper. ESSENTIAL that sand is ABSOLUTELY dry. Use river sand not beach sand. Cap one end and trickle in sand tapping and tamping - Then plug other end. Heat to red and bend focusing heat on inner part so that this thickens. I always over bent 10% and pulled back - This pulls bend circular again and not slightly flattened.
    We also did jacketed (double) wet exhaust pipes in copper for diesel boats and speedboats. Our coppersmith taught us how to do this. Pipes were well annealed, assembled, then brazed one end. Inner pipe and jacket then filled with molten Sodium Thiosulfate (photo fixer). This melted at 50 deg. C. from memory. When cold we hauled pipes to shape cold on slab using chain blocks. Only gentle bends possible. Inner pipes could be 3" and up to 5". Heat and melt out filler. Any residual filler washed out in service.
     
  16. May 22, 2019 #16

    chrsbrbnk

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    the glass beads for bead blasting work really well they are dry fill the tube completely and easily and come back out pretty easy after uncapping
     
  17. Jun 1, 2019 #17

    steveastrouk

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    Another vote for the fine salt as a bending aid. I've had to make dozens of fine, tight precision pancake coils in copper and stainless for professional works with it. Filling with Woods metal is also good, but harder to remove
     
  18. Jun 2, 2019 #18

    olympic

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    These work all right for gentle bends in annealed copper, but they can't handle tight ones, at least in my experience.
     
  19. Jun 2, 2019 #19

    Dubi

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    Something new to me. Used sand to bend aluminium tubing but never salt. Being finer it should result in much more even forms. Thank you.
     
  20. Jun 2, 2019 #20

    john_reese

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    The best reference I have found for specifications and availability is here; https://www.mcmaster.com/copper-tubing.
    For short radius bends there are inexpensive tubing benders available. Check the auto parts stores or Amazon. I was never a fan of the spring type benders that slip over the tubing.

    If using coiled tubing straightening can be a problem. I cut off a length and rough straighten it by hand. Then I lay it on the bench and place a board over it. Using the board I roll the tubing back and forth on the bench until it is straight.
     

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