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Moistue content be inside a cylinder where a vacuum is pulled 25-30HG?

  1. Sep 1, 2010 #1
    What would the moistue content be inside a cylinder where a vacuum is pulled 25-30HG? Could such a cylinder be used to "dry out" something?
     
  2. jcsd
  3. Sep 2, 2010 #2
    Re: Vacuum

    What does pulled 25-30 HG. You mean pulled from that to zero? Or pulled from something else to that? If pulled to zero, then the moisture content would be zero, as the cylinder would contain a vacuum. Please clarify.
     
  4. Sep 2, 2010 #3
    Re: Vacuum

    I am sorry. I am not experienced in physics.

    I thought about making a container to keep my welding rods dry and to "dry" wet ones. My idea was to have a metal or plastic round canister and hook a vacuum pump to it similar to what HVAC technicians do and vacuum the guage until it reads 25-30 hg. My understand is this would "boil out" the moisture in the container. I am not sure if I would be able to open the top or not with a vacuum though.

    Wet welding rods are hard to weld with. Some get wet just sittign out in the humidity. So sorry for my unscientific explanation. I am just tryign to learn more from a physics standpoint.
     
  5. Sep 2, 2010 #4

    stewartcs

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    Re: Vacuum

    You'll need to keep the lid of the container closed in order to keep the vacuum.

    As soon as you open the lid, the rods will start to absorb moisture again (I don't know at what rate) so you'll have put them in the device, close the device, dry them by drawing a vacuum, equalize the pressure with atmospheric, open the device, take one out, close the device again and draw the vacuum again to keep them dry.

    You may need to purge the container with dry Nitrogen to help speed up the drying process.

    CS
     
  6. Sep 2, 2010 #5
    Re: Vacuum

    So by saying equalizing the pressure to atmospheric I should add some sort of pressure relief valve to depress before opening?

    The only time the lid would be open would be when a rod has to be used.

    My only problem is I dont know how well a small vacuum pump would remove moisture. I sometimes use an old refrigerator pump. I would liek to have some sort of msall pump I could mount on the container.
     
  7. Sep 2, 2010 #6

    Mech_Engineer

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    Re: Vacuum

    You might consider just getting a dry purge box that you can use some dessicant and/or dry nitrogen in. My guess is if you're a welder you have access to a gas supply company, ask how much a bottle of dry N2 is and then look into purge boxes. Worst case, all you really need is a sealed box of some kind (even Tupperware would probably work) and some silica dessicant packets.
     
    Last edited: Sep 2, 2010
  8. Sep 2, 2010 #7

    stewartcs

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    Re: Vacuum

    Yes you would need some type of valve to equalize the pressure. You most likely will not be able to even open the lid without equalizing the pressure (there would be a very large net force from the atmospheric pressure acting on the lid).

    However, using desiccant like Mech_Engineer suggested may certainly be the simpler and cheaper route.

    CS
     
  9. Sep 2, 2010 #8
    Re: Vacuum

    But desicant would not "dry" an already wet rod would it?
     
  10. Sep 2, 2010 #9

    RonL

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    Re: Vacuum

    Well I'm from the stone age, we used a hot box, generally an old discarded refrigerator with a low wattage light bulb that burned all the time, the heat moved the moisture out on a continual basis.
    Unless you just want to experiment with vacuum ??

    Ron
     
  11. Sep 2, 2010 #10
    Re: Vacuum

    I dont have room for a refrigerator but admitt I like to experiment. :)
     
  12. Sep 2, 2010 #11

    RonL

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    Re: Vacuum

    With vacuum, as long as there is moisture to boil away the vacuum pump will have to be running, once an acceptable level is reached a seal will have to be maintained, as was mentioned before.

    A very small box can be made, if just a few rods need to be kept dry, you might use an old computer case, it would not even need to be insulated just closed enough to hold more heat inside than the outside temperature.

    Let your mind wander a little:smile:

    Ron

    Also sometime back I figured the cost of burning a large bulb off of a set of christmas lights, one blub at our local rates, cost just one cent for a 24 hour day (30 cents/month).
     
    Last edited: Sep 2, 2010
  13. Sep 2, 2010 #12

    stewartcs

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    Re: Vacuum

    It would depend on how much desiccant you have. Desiccant can become saturated and not absorb any more moisture so you'll need to make sure your rods are not soaked!

    CS
     
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