Salt water resistor for a load
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  1. #1
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    Salt water resistor for a load

    Anyone experiment with this? I took a 5 gallon bucket and dissolved about a half a cup of table salt in water. Took two pieces of 1/2" copper pipe, each about 18" long and suspended them downwards into the water through a piece of 2x4 that spanned the lid of the plastic pail. Hooked up the welder I am testing and ran current through it. Could only get around 100 amps by my estimation to flow. Current increased as the temperature rose, and the bucket was quickly boiling water.

    Anyone try this? What would I need to do to get more amperage to flow? Moving the electrodes closer didn't seem to make a difference. More surface area? I'd like to have around 200 amps flowing so I could test the current control circuitry under load.

    Tim

  2. #2
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    Re: Salt water resistor for a load

    I'm kinda missing the point, but yeah more surface area will do it.

    Keep in mind that the bucket of salt water will not be a bucket of salt water for long. The sodium chloride will break down undder electrolosis. Chlorine gas will bubble out, leaving only sodium. The sodium reacts with the water to form sodium hydroxide (lye). Something to think about when handling and disposing of the solution...

    Baking soda is a better choice than salt. It carries current better, and doesn't become a caustic solution.
    Last edited by Joe H; 12-29-2008 at 06:03 PM.

  3. #3
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    Re: Salt water resistor for a load

    To a degree, adding more salt to the solution should increase its conductivity.
    Are you reading the current value with a clamp-on meter on one cable? That would be a good way to check any ammeter on the machine.

    In the early days of arc welding, the LaGrange-HoHo process was developed; with it, the article to be welded was connected to one pole and a bucket of water connected to the other pole. Sometimes the first connection was to a blacksmith's tongs which would hold the item as it was dipped into the water. When current was turned on, the part would soon turn red when it would be removed from the water and forged or forge-welded. I don't know if today's standard welders have the needed power characteristics for this. The water here also uses some ionizing compound like sodium carbonate to lessen the voltage necessary.

    Hey, Denrep;
    Do you and Alfred need another experiment to try? I've been meaning to test this for years, but other things keep coming up....
    Last edited by Oldiron2; 12-29-2008 at 06:18 PM.

  4. #4
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    Re: Salt water resistor for a load

    The reason for doing this is to provide a sufficient load to test the machine for a number of minutes while I troubleshoot the circuitry. I needed something inexpensive that would absorb the energy of probably 5-10kw without striking an arc.

    I'll try the baking soda solution and see how that works.

    I did not notice any chlorine like smell during operation of the load for probably a cumulative total of 5-10 minutes. The water did turn yellow and the one electrode became covered in what looked like copper scale.

    From what I've read, this method has been used for years to test large generators and I'd found some obscure references to it for testing welding equipment and radio transmitters.

    Current was measured from the welder's hall device which produces 1.6volts per 100 amps output. Best I could get with my setup was 1.7 volts. The welder is not properly controlling current output and with a welding rod it produces over 300 amps and burns up the rod pronto. Also, not a convenient way of absorbing energy while I take measurements and eventually go over the controller circuitry with an oscilloscope.

  5. #5
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    Re: Salt water resistor for a load

    If one bucket pulls 100 amps, why not run two buckets in parallel?

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  6. #6
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    Re: Salt water resistor for a load

    Sounds like I could both heat and chorinate the neighbours pool all with one device.

  7. #7
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    Re: Salt water resistor for a load

    Tried baking soda, and I can't get the same current flow. Not sure how much to dissolve in the bucket, but it only flowed about half the current. I then added some salt, and it jumped up to around 100 amps again.

  8. #8
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    Re: Salt water resistor for a load

    Quote Originally Posted by Tim View Post
    The reason for doing this is to provide a sufficient load to test the machine for a number of minutes while I troubleshoot the circuitry. I needed something inexpensive that would absorb the energy of probably 5-10kw without striking an arc....
    Clamp a carbon between the leads and drop it in pail of water.

    I've used the "poor-boy load bank" many times.

    When I load tested a machine recently, I dunked the leads in a wheelbarrow full of water. I'm almost positive I took the pictures, but I can't find them right now.

    Good Luck
    Last edited by denrep; 01-02-2009 at 08:03 PM.

  9. #9
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    Re: Salt water resistor for a load

    I tried a 3/32 steel tig filler rod underwater, and it draws plenty of amps of without melting down. I'll have to pick up a carbon arc rod next time I'm out and about near a welding supply store. I've never had use for one yet, so I don't have one lying around. The tig rod provided a load long enough to observe the waveform of the output on the oscilloscope, which was my objective. So far I'm finding everything right, and nothing wrong yet as I continue to troubleshoot this Syncro 250 that is stuck on full output. Hall device puts out up to 8 volts which I run the machine into the dead short underwater. That's a reading of 500 amps, if the hall device is correct.

  10. #10
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    Re: Salt water resistor for a load

    straight tap water is mildly conductive. the impurities in it cause it to have lower resistivity than distilled and de-ionized water, which its pretty much non-conductive..

    salinity will affect resistivity, as will plate area. keep in mind you can melt electrodes tat aren't capably of passing the current. they could burn thru the bucket, contct and arc-flash in front of you, causing you to possible have a bad and/or expensive day.

    Joe H, thanks for the chem lesson!!
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  11. #11
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    Re: Salt water resistor for a load

    Quote Originally Posted by denrep View Post
    Clamp a carbon between the leads and drop it in pail of water.

    I've used the "poor-boy load bank" many times.

    When I load tested a machine recently, I dunked the leads in a wheelbarrow full of water. I'm almost positive I took the pictures, but I can't find them right now.

    Good Luck
    I know it's late, but I just stumbled into the pics.
    Not dunked in water, but anyway, you'll get the idea:

    Attachment 29476
    Last edited by denrep; 08-24-2009 at 12:14 PM.

  12. #12
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    Re: Salt water resistor for a load

    Aren't you going to get oxygen and hydrogen gas by putting that much current
    through water? What's going to happen when that hydrogen reaches a spark
    from the welder?

  13. #13
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    Re: Salt water resistor for a load

    Eric, that's probably why they usually put those kind of systems outdoors or on the roof tops. I have read they use salt water loads to test large generators, like locomotives. Luckily I'm done with this science experiment now, the welder is fixed.

  14. #14
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    Re: Salt water resistor for a load

    how about nipple clamps?
    plenty tough and union made.

  15. #15

    Re: Salt water resistor for a load

    i built a handheld carbon arc welder using a carbon arc furnace design. i used a saltwater variable resister. it works great but the water gets hot to fast. anyone know of a good replacement for it.

  16. #16
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    Re: Salt water resistor for a load

    Quote Originally Posted by whitehendrix! View Post
    straight tap water is mildly conductive. the impurities in it cause it to have lower resistivity than distilled and de-ionized water, which its pretty much non-conductive.. ....
    My father once told me that when they tested ships generators in WW2; the water in the Willamette river, at Portland, was so free of minerals they had to have a man shoveling salt into the river to raise the conductivity sufficently to allow the tests to proceed.

    I have watched salt box tests of generators, where the volume of the box was measured in cubic yards, with a fire hose connected to replace the heated water with cold for cooling.
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  17. #17
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    Re: Salt water resistor for a load

    50 years ago or so I welde a car frame together with 6011(then called farmers rod) and a salt water welder. the same thing you guys are doing except useing the salt water to lower the voltage and up the amperage on a 220 line. Mac

  18. #18
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    Re: Salt water resistor for a load

    Salt-water rheostats are common in electroplating.

  19. #19
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    Re: Salt water resistor for a load

    bolleoy said, "i used a saltwater variable resister. it works great but the water gets hot to fast. anyone know of a good replacement for it?"

    C&H Surplus in the Los Angeles area had a bunch of very large, very low value resistors at their Pasadena store before shutting down a couple of years ago. One of the original store owners has opened a smaller store in Duarte with some of the old stock. I'm not sure, but think I saw a few of those huge resistors in his new store. I'm not local to the store, but try to get by there once or twice a year while on family visits to the LA area. His number is 1-626-256-7907 and his website is www.candhsurplus.com. I don't see these resistors listed in his online catalog but that may just mean he only has a few left.

    These are the type of resistors that are slung under transit vehicles to dissipate braking energy, not something you mount on a circuit board or inside an instrument box. They are edge-wound coils of resistive bar stock about a foot or more long and from two to 6 inches in diameter, depending upon resistance and power rating. They have resistances in the tenths or hundredths of ohms and current ratings of hundreds of amps. I have one in my lap right now that is a foot long and 5 inches in diameter rated at 0.069 ohms and 170 amps. That would be about 12 volts. I assume that rating is for ambient air cooling and that it could be increased with aggressive fan cooling and increased substantially by dunking in CLEAN water. No electrolysis, no chemicals, and no disposal problem,

    I paid $25 for it several years ago at the Pasadena store. "Might need this someday."

    awright

  20. #20
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    Cool EAsy Bake Oven

    How about using common "Oven Heating Elements" . I would mount them in a cage with a fan or submerged in a water tank (dahh...water heater elements???) The elements are cheep and easy to find and are rated at 220V so they won't go up in flames. You can configure them in parallel to provide the desired load.

  21. #21
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    Re: Salt water resistor for a load

    You can detect chlorine well by inhaling deeply - if you die then it was chlorine.

    Seriously - don't underestimate how deadly chlorine gas can be. This can be done safely, but you have to make sure the area is well ventilated.

    Can't count how many folks have died by mixing ammonia and bleach - they find out it was a bad idea when they stop breathing permanently.
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  22. #22
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    Re: Salt water resistor for a load

    Water heater elements are very handy high power resistors for many purposes and I have recommended them as electronic loads many times elsewhere. However, in this application it will take quite a few of them to make up a load of suitably low resistance.

    Just to take a random example, the resistor I described in my post above has resistance of 0.069 ohms and a current rating of 170 amps. E = I*R tells us that this current would occur with about 12 volts applied to the resistor - a reasonable value for testing a mid-sized welder.

    A 3.5 KW 220 volt water heater element costing in the neighborhood of $20 has a resistance of R = (E^2)/P = 48400/3500 = 13.82 ohms. You will require 200 elements in parallel to get a 0.069 ohm resistor bank. (This surprises even me.) Of course, you would then have a 700KW load (if submerged in water).

    awright

  23. #23
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    Re: Salt water resistor for a load

    Coils of steel lumber strapping in water.
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  24. #24
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    Re: Salt water resistor for a load

    Quote Originally Posted by Tim View Post
    Eric, that's probably why they usually put those kind of systems outdoors or on the roof tops. I have read they use salt water loads to test large generators, like locomotives. Luckily I'm done with this science experiment now, the welder is fixed.
    So after all that are ya gona tell us ?
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  25. #25
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    Re: Salt water resistor for a load

    Quote Originally Posted by the Q View Post
    how about nipple clamps?
    So what is the current indicator??? OH Never mind. Sounds like a 3 stooges thing.
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