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Minimum Humidity for long term storage of computer equipment?

Discussion in 'Electronic Components' started by Peter Olcott, Apr 18, 2006.

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  1. Peter Olcott

    Peter Olcott Guest

    Is there a minimum level of relative humidity, below which computer equipment is

    I bought some antique handheld computers. I want to keep them in pristine
    condition for a very long time, fifty years or more. I want to know the ideal
    environmental conditions to store these computers. I am probably going to store
    these in a bank vault. I can greatly reduce the relative humidity using a
    commercial desiccant such as drierite.

    Thanks for your help.
  2. Jim Thompson

    Jim Thompson Guest

    Is the bank vault hermetically sealed? Or your packaging? If not,
    long term, they will return to ambient conditions.

    ...Jim Thompson
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | | 1962 |

    Old Latin teachers never die...they just decline
  3. Peter Olcott

    Peter Olcott Guest

    My vacuum packaging is hermetically sealed.
  4. If you have vaccuum packaging, isn't humidity irrelevant? And, what about
    dry nitrogen? For those time scales, you'll want to remove oxygen, not just
    water vapour. Vacuum isn't a good idea, as you'll lose plasticisers and
    other chemicals that prolong the life of capacitors, and maybe have hazards
    that can cause bother in other people's space, but if you have a hermetic
    seal with the volume filled with dry nitrogen at atmospheric pressure, you
    can't go far wrong, as far as I know.
  5. Peter Olcott

    Peter Olcott Guest

    It is nothing like a prefect vacuum, I am only using a foodsaver meat packaging
    machine. The idea is to make the package fit tightly, removing all the excess
    What about reducing the relative humidity to zero?
    I can't go to this extreme, what is the next cheaper option?
  6. If you cant go to a gas refill station and get some nitrogen, next best
    thing would maybe be get the small co2 cylinders like used for paintball,
    and purge the containers with co2 gas. It will drive out all the oxygen,
    which is what causes rust with water vapor. Also use the desecant to absorb
    any remaining moisture.

    Still nitrogen is best!
  7. Ken Finney

    Ken Finney Guest

    Backfill the bags with dry nitrogen (MIL-PRF-27401, Type 1 Gas, Grade C
    (99.995%)), and use Mitsubishi Gas Chemeical American dessicant type RP-5.
  8. Peter Olcott

    Peter Olcott Guest

    How could this be packaged to retain the nitrogen / co2 ?
  9. Guest

    Guest Guest

    : My vacuum packaging is hermetically sealed.

    Might be good if all of this sealing didn't generate Electrostatic
    Discharge also. Often, pressurized air/vacuum can generate ESD.

    I don't know why it's important to keep the computer vs. storing the
    data instead. It's likely the capacitors will eventually depolarize
    over time if they're not powered up.

    some things to think about....

  10. Peter Olcott

    Peter Olcott Guest

    I want to store the computers because there has only been one computer made that
    I can use in direct sunlight, fit inside my pocket, with a large enough screen
    and keyboard that I can do C++ programming. HP 200LX. They quit making these ten
    years ago, and no one has made anything like them since. I bought four of them
    so that I will never run out.
  11. Peter Olcott

    Peter Olcott Guest

    Is there anyone that can do this as a service?
  12. I don't think there's a minimum humidity, so go ahead and use plenty
    of desiccant.
    Do these computers have rechargable batteries? If so, there's not
    much you can do...

    There are commercial oxygen absorbers that look very similar to
    desiccants that'll make your air into nitrogen for you. However, your
    vacuum-packed plastic may not be as water-tight as you think. I'd
    also put a humidity indicator card in each one so you can keep an eye
    on the humidity levels.
  13. Peter Olcott

    Peter Olcott Guest

    They take any kind of AA penlight battery, I am currently using Duracell 2500
    mAh, and getting seventeen hours of continuous use. Before I had the units
    upgraded to double their speed they got twenty-seven hours of continuous use.
    They run all the programs from the original IBM PC at (an upgraded speed of)
    about 1/3 faster than the original IBM AT.
  14. Ken Finney

    Ken Finney Guest

    Well, White Sands Missle Range.... ;^)

    Since vacuum is being used, just using the the dessicant is probably good
    enough. Mitsubishi has changed their numbering system, and apparently in is
    know known as "RP A-type".
  15. Ken Finney

    Ken Finney Guest

    Good point, Aluminum Electrolytic capacitors may not work after 10 years.
  16. Ken Finney

    Ken Finney Guest

    Forgot to add:
  17. Nothing extreme about dry nitrogen. :) It's the single most abundant gas in
    the atmosphere, and you can get it in welder's gas cannisters. To seal it,
    just use a plastic bag in a cardboard box, with some freshly baked silica
    gel sachets in the bag with the gear. If you can seal the bag so it acts
    like an air pillow and resists loss of gas when you try to squeeze it, that
    will be fine. As the inside and outside will equalise at atmospheric
    pressure, even a pinhole leak won't do much harm for many months, so long
    as the box resists compression.

    Pack gear, put gel sachet, flush from gas cannister through a tube through
    the almost closed bag for a couple of minutes, remove tube, seal, squeeze
    to test seal. Close box.

    Test seal every year for first five years, by squeezing the bag. :) It's
    very cheap, very basic, and very easy.
  18. Peter Olcott

    Peter Olcott Guest

    The only thing that I would not know how do, after your excellent explanation
    would be to find the most cost-effective source of nitrogen gas. It would be
    nice If I could buy a couple of cubic feet at Wal-Mart for $2.99. Also would
    nitrogen gas be reactive with CaSO4, CoCl2 ?
    (That is the composition of my "drierite" desiccant).
  19. Thnkyou. :)
    I'm not sure about the reaction, but I doubt it, nitrogen is chosen for
    being largely inert. On the other hand it's associated with interesting and
    often violent chemistry, so it's worth checking with the maker of your
    dessicant. Basic rule is: if a thing doesn't react much with air over time,
    ir definetely WILL NOT react with nitrogen under similar temperature and
    pressure, as air is mostly nitrogen already.
  20. Peter Olcott

    Peter Olcott Guest

    How can I get nitrogen least expensively?
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