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A Safe Solvent

Discussion in 'Electronic Basics' started by Randy Gross, Nov 14, 2003.

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  1. Randy Gross

    Randy Gross Guest

    Greetings,

    Has anyone used, or know of, a safe method/solvent for removing varnish
    from windings that won't ruin the insulation?

    Randy Gross
     

  2. To the best that I've been able to ascertain plain old over the counter ~70%
    concentration rubbing (isopropyl) alcohol seems to make the varnish all
    rubbery without damaging the insulation. Certainly my testing methods of
    the winding enamel haven't been scientific in the slightest being that I
    hold the belief new wire is a good investement. A basic resistance
    measurement along with physically scratching the enamel test were the extent
    of my investigations. In those tests it seemed to me the enamel was pretty
    much the same as it was prior to exposure to the rubbing alcohol. YMMV with
    different enamel insulations and more scientific testing.

    Unless you heat the alcohol it will take a very long time to make a
    significant impact on the varnish (likely in the days to weeks range). I've
    sucessfully used a sealed jar heated on a stovetop to about 100 deg. C in a
    pot of water to heat the alcohol to accelerate the process. It takes less
    than 30 minutes of heating to achieve good results. Not everyone likes the
    sounds of this idea on the grounds that it sounds risky to them. Rubbing
    alcohol boils at under 100 deg. C (at 1 atm pressure) so it must be enclosed
    in a sealed container with enough integrity not to burst or leak
    significantly. Isopropyl alcohol of 70% or more is flammable (and perhaps
    with just the right stoichiometric mix somewhat explosive) so keep that in
    mind.
     
  3. Mac

    Mac Guest

    It doesn't seem THAT dangerous on an electric range. But on a gas range,
    it seems too dangerous to be reasonable.

    What scares me the most about it is that if the container fails
    catastrophically, you will have a sudden burst of alcohol vapor in close
    proximity to an open flame with no time to react. It could definitely
    start a fire, singe some hair, or maybe even blow out a window.

    It would be much safer to do this without the hot-water bath but with a
    lab-supply hot-plate. I'd still make sure I had a large fire-extinguisher
    handy.

    Come to think of it, I don't think I would do this even with an electric
    range. Not worth the risk.
    Alcohol vapor mixed with air is super flammable. If the fuel/air mix is
    just right, a cup (~250mL) could probably blow the roof off of your house.
    At any rate, I've heard that a quarter cup of gasoline, totally vaporized,
    and mixed properly with air, is equivalent to one stick of TNT. I don't
    know how true it is, but I think alcohol has at least 50% of the chemical
    potential energy as gasoline, and it is easier to ignite.

    Mac
    --
     
  4. Jeff

    Jeff Guest

    Gasoline has about 38,000 kj/l worth of energy. A 1/4 cup of gasoline would
    therfore contain about 10,000 kj. If vaporized, and properly mixed with air,
    it would almost burn instantly. Anyone know how much energy is in a stick of
    TNT?
     
  5. http://octopus.gma.org/surfing/weather/andypwer.pdf displays 4.2x10^15 Joules/megaton of TNT, which implies there are 46,000 kJ/kg in TNT. I have no idea how much mass is in a stick of TNT, but if we assume it is 1/4kg (12,000 kJ), then 1/4 cup of gasoline works out as a reasonable comparison.
     
  6. Although my calculations do agree that alcohol has somewhere around 50% of the energy storage of gasoline and that gasoline is comparable to TNT, I seriously don't think anyone needs to worry about explosions removing roofs or windows from your home. It simply won't happen with 30% water contamination using ambient air (versus a pure oxygen atmosphere or a highly compressed, properly mixed internal combustion engine). If you read various sites, such as [ http://www.violetwand.org/fire.htm ], there is evidence that people ignite alcohol on their signficant others using Tesla wands in their bedrooms/torcher chambers. If a human body can withstand an alcohol fire, I should think a stove top/floor/etc. could as well (assuming someone is actively paying attention to it).
     
  7. N. Thornton

    N. Thornton Guest


    Fritz, the OP said safe :)

    Regards, NT
     
  8. Tim Shoppa

    Tim Shoppa Guest

    If it does leak, it just evaporates. I'm all for safety and using
    proper containers, but it's just not that big a deal. As it evaporates,
    the alcohol goes away before the water... leaving you with water.

    Now, if you're going to be heating a sealed container of isopropyl,
    that's a different safety matter. I would rather have the container
    fail at low pressure than at high pressure!

    Tim.
     
  9. Randy Gross

    Randy Gross Guest

    I can see from this discussion, by general consensus, that the method works
    and, there is an element of danger. I agree that the container should be
    capable of pressure relief and can be as simple as a drilled hole in the
    cap, covered with a rubber flap, and enough weight applied to maintain a
    reasonable level of pressure. Vented vapor can be routed away from the heat
    source or, better yet, boil this wicked brew in Mother Natures' kitchen.

    Thanks Guys,

    Randy Gross




















    <>...
    : > Rubbing
    : > alcohol boils at under 100 deg. C (at 1 atm pressure) so it must be
    enclosed
    : > in a sealed container with enough integrity not to burst or leak
    : > significantly.
    :
    : If it does leak, it just evaporates. I'm all for safety and using
    : proper containers, but it's just not that big a deal. As it evaporates,
    : the alcohol goes away before the water... leaving you with water.
    :
    : Now, if you're going to be heating a sealed container of isopropyl,
    : that's a different safety matter. I would rather have the container
    : fail at low pressure than at high pressure!
    :
    : Tim.
    :
     
  10. -------------
    That is correct, liquid petroleate fuels are near the highest energy
    densities, well above solid explosives, even pure organic nitrates.
    That is why kerosine and liquid oxygen is still the second most powerful
    fuel for rockets next to pure H2 and O2.

    -Steve
     
  11. ------------
    Actually it depends totally on the conditions of combustion, since
    alcohol evaporates off any surface due to its own combustion
    temperatures, whereas if prevented from doing so, for instance
    with a focused torch or liquid fuel engine, could immolate a
    human body all the way to ammonia, mineral oxides, H2O, and CO2.

    -Steve
     
  12. Chris Carlen

    Chris Carlen Guest


    Hydrocarbon fuels will have much greater energy per mass than high
    explosives. It is the rate of energy release of explosives that gives
    them their kick. They acheive the highest peak power outputs compared
    to other chemical energy sources, but lower total energy outputs.

    An analogy is high power pulsed lasers. I work with lasers that can
    easily exceed the 220 Megawatts power output level. That's right, I
    said 220 MW!!!

    But since the pulse only lasts 8ns, the total energy delivered is about
    1.76J. But the high rate of energy delivery, coupled with delivering
    that energy over a very small area, translates into considerable
    destructive power. These sorts of lasers can blow holes in metal sheets
    and optical elements.

    Check out these photos for an example:

    http://home.earthlink.net/~crobc/laser-photos/index.htm

    The red and blue lasers in these photos are a dramatization. The laser
    that actually blew the window (about 1" dia. x 1/8" thick crystalline
    quartz) was invisible 266nm UV radiation at about 16 MW .


    Good day!
     
  13. IIRC, F2 and H2 have the highest specific impulse of any chemical
    reaction. O2 and petroleum fuels are in the 250S range, while H2
    &F2 are close to 400. However, F is rather nasty stuff (being the
    most electronegative of all elements) thing to deal with, in just
    about every way. F2 has been used as rocket propellant though.
     
  14. Bob Masta

    Bob Masta Guest

    As I recall, the military was experimenting a while back with
    weapons that used air and fuel, with some means of volatilizing
    the fuel to some optimum state just before ignition. Haven't
    heard anything about this in a while, so I don't know if this is
    still ongoing. I think Hollywood also picked up on this project
    a few years back for a Dustin Hoffman movie where the
    military was going to use one of these weapons to destroy
    a town infected with a virus.



    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
  15. Sure. FAE's are still around. These are one type of hyperbaric
    explosives (primary damage is by over-pressure). The "daisy-
    cutters" are another. In Desert Storm the US used them on Iraq.
    The story was that the Brit field commanders thought the US had
    gone nuclear when they were used. Indeed they've been called the
    "poor man's nuke".
    Seems reasonable, for Hollywood.
     

  16. Yeah they were wrong in that movie (was it called Outbreak?). Fuel Air
    Explosives aren't the most powerful non-nuclear weapon in the US arsenal.
    Rather the MOAB (Mother Of All Bombs, aka, Massive Ordinance Air Burst) is.
    IIRC the MOAB has a yeild of something like 25 tons of TNT, whereas
    Hiroshima had a yeild of about 14.5 kilotons of TNT. Still a far cry from
    even relatively small nuclear bombs, but they do make much smaller nuclear
    bombs than used on Hiroshima.

    For some extra reading:

    http://www.twin-towers.net/moab_bomb.htm

    http://www.opendemocracy.net/debates/article-2-88-1028.jsp
     
  17.  
  18. IIRC, the Russians (Germans) were experimenting with H2-F2
    engines in the early 50's, IIRC. The US had some research here
    too. Enough research that both sides built production
    capabilities for F2. Both (eventually) found the hazards of a
    rocket full of F2 falling where one didn't want it (at the time
    this was a frequent occurrence), outweighed the advantages.

    HFL is a similar nasty that has been used.
     
  19. I suppose since MOAB is a hyperbaric bomb, it could be considered
    an FAE (it is fuel rich, so does depend on air, and do go bang).
    I hadn't considered this angle on FAE before though. Perhaps
    this is where they're going?
     
  20. Mac

    Mac Guest

    Well, I never said anything about anyone getting hurt, other than singed
    hair, but it doesn't take much pressure to blow out a window in your
    house. I admit that blowing the roof off is not very likely, unless your
    house is small and tightly sealed.

    Also, the scenario I'm envisioning is one where the alcohol is in, say, a
    glass jar. The alcohol, at 100 C, builds up enough pressure to rupture the
    jar (I don't know if this is likely -- depends on the pp of isopropanol at
    100 C, I guess). Now, released from the pressure of the jar, the alcohol
    vaporizes instantly, and mixes in with the air. Shortly after rupturing,
    the fuel-air mix is ignited by the flame of the burner. The combustion
    releases a lot of energy, and I could see it breaking a window, if the
    window were close and closed. I definitely wouldn't expect anyone to die
    (except maybe in the subsequent fire).

    Anyway, I guess we've gotten pretty far afield from electronics. ;-)

    Mac
    --
     
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