taiwanluthiers Posted October 23, 2012 Posted October 23, 2012 I am only using a thick titanium plate (3mm thick, about 3/4" wide) as a lead, would that work?
WSM Posted October 23, 2012 Posted October 23, 2012 I am only using a thick titanium plate (3mm thick, about 3/4" wide) as a lead, would that work? Yes, it does work. The reason we're spending so much time and energy with tubular titanium leads is to be able to seal them in compatible compression fittings. The beauty of that is they'll hold the electrodes solidly and also prevent salt creep from eating our copper electrical connections and power leads. Titanium is only 3.1% as conductive as copper, so we're filling the tubular leads with more conductive metals (like tin, nearly five times as conductive as titanium) to cut down on their resistance (which creates heat which would work against our plastic compression fittings). WSM
taiwanluthiers Posted October 23, 2012 Posted October 23, 2012 Does that mean the Ti plate will get really hot and any attempt to seal it in silicone would be futile? I have no way of welding Ti, and neither does anyone else in the area, so I was planning on just bolting the anode to the Ti plate as an extension.
Arthur Posted October 23, 2012 Posted October 23, 2012 Swede was successful in welding anode mesh to a Ti bar with a DIY spot welder made from a retired Microwave oven transformer, (remove the secondary and replace with a few turns of really fat copper wire). I'm truly surprised that there isn't a suitable spot welder in Taiwan -you don't have to tell them it's titanium! Just ask them to weld some mesh to some bar to your sketch.
taiwanluthiers Posted October 23, 2012 Posted October 23, 2012 By that I take it you mean that bolting the connection won't be enough? I read that spot welders only work on thin metal, but my Ti plate is about 3mm thick... I don't think a spot welder will work.
WSM Posted October 23, 2012 Posted October 23, 2012 By that I take it you mean that bolting the connection won't be enough? I read that spot welders only work on thin metal, but my Ti plate is about 3mm thick... I don't think a spot welder will work. I have a spot welder that runs on 110Vac and managed to weld three titanium pieces totalling about 9mm thick. It needs to run long enough to get the spot to glow before the power is shut off. In fact, my best welds on thick material were done twice (weld, flip the piece over and weld again on the same spot). WSM
WSM Posted October 23, 2012 Posted October 23, 2012 (edited) Does that mean the Ti plate will get really hot and any attempt to seal it in silicone would be futile?I have no way of welding Ti, and neither does anyone else in the area, so I was planning on just bolting the anode to the Ti plate as an extension. The titanium leads can get hot if excessive current is run through them. Even still, silicone RTV can usually handle fairly high temperatures when cured. WSM Edited October 23, 2012 by WSM
WSM Posted October 23, 2012 Posted October 23, 2012 (edited) By that I take it you mean that bolting the connection won't be enough? I read that spot welders only work on thin metal, but my Ti plate is about 3mm thick... I don't think a spot welder will work. I think bolting would work just fine if the hardware is compatible with the cell liquor and it's properly tightened. WSM Edited October 23, 2012 by WSM
taiwanluthiers Posted October 23, 2012 Posted October 23, 2012 I was thinking titanium bolts, or just stainless steel bolts coated with some kind of a barrier such as PVC...
pdfbq Posted October 23, 2012 Posted October 23, 2012 (edited) Titanium is only 3.1% as conductive as copper, so we're filling the tubular leads with more conductive metals (like tin, nearly five times as conductive as titanium) to cut down on their resistance (which creates heat which would work against our plastic compression fittings). I did not have any heat problems with my 1.5 x 25mm Ti shafts.I totally believe the 3.1% but I do not think it makes that much difference in my cell. I did some calculation.A copper shaft of 125/25/1.5 mm at 250W would loose about 0.07 watt.A Ti shaft of the same dimension would loose about 1.75 watt, less then 1%. Of course the round shafts are beautiful and better to mount but I don't think its really necessary for a first time cell. 0.125 * 1.68 * 10^-8___________________ = ~0.000056 ohm (Cu) 0.025 * 0.0015 0.125 * 4.20 * 10^-7___________________ = ~0.0014 ohm (Ti) 0.025 * 0.0015 Edited October 23, 2012 by pdfbq
WSM Posted October 23, 2012 Posted October 23, 2012 I did not have any heat problems with my 1.5 x 25mm Ti shafts.I totally believe the 3.1% but I do not think it makes that much difference in my cell.I did some calculation.A copper shaft of 125/25/1.5 mm at 250W would loose about 0.07 watt.A Ti shaft of the same dimension would loose about 1.75 watt, less then 1%.Of course the round shafts are beautiful and better to mount but I don't think its really necessary for a first time cell.0.125 * 1.68 * 10^-8___________________ = ~0.000056 ohm (Cu) 0.025 * 0.00150.125 * 4.20 * 10^-7___________________ = ~0.0014 ohm (Ti) 0.025 * 0.0015 Hi pdfbq, I suppose it has to do with how large the electrodes are, their configuration and spacing, plus how many Amperes they're drawing . WSM
pdfbq Posted October 24, 2012 Posted October 24, 2012 (edited) I suppose it has to do with how large the electrodes are, their configuration and spacing, plus how many Amperes they're drawing . Exactly. Because in a cell the electrodes are short there is not much loss. In my example i am talking about 50 amps and an electrode length of 12.5 cm.. if the length would be 25cm the loss would be double (3.5 watt) less than 1A.The spacing has not much to do with it I think. Edited October 24, 2012 by pdfbq
WSM Posted October 24, 2012 Posted October 24, 2012 Exactly. Because in a cell the electrodes are short there is not much loss. In my example i am talking about 50 amps and an electrode length of 12.5 cm.. if the length would be 25cm the loss would be double (3.5 watt) less than 1A.The spacing has not much to do with it I think. Hi pdfbq, With spacing, the furthur apart the electrodes are from each other, the higher the internal resistance of the cell (and the more energy that'll be consumed). Energy "wasted" as heat is another cell ineffiency. I use parenthesis because the heat isn't totally wasted since it improves cell efficiency. With electrodes too close to each other, we limit the fluid flow and risk shorting the electrodes together (which I think is worse). Spacing may be more important than we think...(or, it's just a picky detail). No matter what we think we know, there is always more we could know about all of this (If I don't keep learning all the time, I'm not doing it right! ). WSM
pdfbq Posted October 24, 2012 Posted October 24, 2012 I was responding to your statement of Ti being only 3.1% of the conductivity of copper.
frank Posted October 24, 2012 Posted October 24, 2012 The most popular supply for this job is the fixed 5v supply from a computer.The 'excess' voltage has to be got rid of somewhere. Power ineffiency guaranteed from the decision to use the 5vsupply. Have to get rid of the excess voltage somewhere. Be glad the excessive electrode spacing!!!
Swede Posted October 24, 2012 Posted October 24, 2012 Flat straps work fine so long as they are not driven too hard. but the majority that I've seen on commercial anodes and cathodes are sadly undersized. In one case, at 50 amps, my cathode strap easily exceeded 200 C or so, gave me a really nasty burn. As WSM said, the round shank concept came about from a total frustration in getting a decent mount using straps. They are fine for food container, desktop cells, but even then, the mounting is a bit floppy, there's gobs of salt creep, and just about any sealant that was used was destroyed by the chlorine. When the time came to make big cells, I was faced with cutting a very thin slot in a thick piece of PVC. This is essentially impossible to do. I used a machine tool to do it. The only possible way using normal tools would be to chain drill a series of small holes, and get in there with a hacksaw blade and needle files and the like to get the strap to mount. And even when you are done, you've got a floppy electrode, needing additional support external to the lid. The round shanks fit through kynar (PVDF) compression fittings after the fittings are drilled through. They are 100% rigid and leakproof. http://www.5bears.com/perc/rst04.jpg To mount, a correct hole is drilled in the lid if the lid is thick enough, and the hole tapped with what is called a tapered tap. Very common in plumbing. And decent hardware store will carry tapered pipe thread taps. The compression fitting is screwed in tight, the anode inserted from below, then the compression fitting nut is secured. A ferrule inside the nut pinches and seals the tube. Before that, I had tried all sorts of differing systems that were kludgy and did not work: http://www.5bears.com/perc/tc054.jpg http://www.5bears.com/perc/tc055.jpg http://www.5bears.com/perc/tc056.jpg All of these were super labor-intensive, and vulnerable. As far as no spot welding - if you use titanium bolts and nuts, AND clean the joint thoroughly using abrasives to strip all oxides, AND tighten the nut and bolt to a point where the joint nearly deforms, it'll work. Otherwise, electrolytes will creep between the metals, oxidize the skin, and kill the continuity.
Swede Posted October 24, 2012 Posted October 24, 2012 I did not have any heat problems with my 1.5 x 25mm Ti shafts.I totally believe the 3.1% but I do not think it makes that much difference in my cell. I did some calculation.A copper shaft of 125/25/1.5 mm at 250W would loose about 0.07 watt.A Ti shaft of the same dimension would loose about 1.75 watt, less then 1%. Of course the round shafts are beautiful and better to mount but I don't think its really necessary for a first time cell. 0.125 * 1.68 * 10^-8___________________ = ~0.000056 ohm (Cu) 0.025 * 0.0015 0.125 * 4.20 * 10^-7___________________ = ~0.0014 ohm (Ti) 0.025 * 0.0015 I may have missed it, but what current were you running? Power loss isn't so much of a factor as it is simple heating. 1.5mm x 25mm straps were what I started welding to my MMO stock after I realized smaller straps were simply overheating badly. A strap of that dimension is going to be able to handle heavy current without too much problem. With these tube anodes, there is nowhere near the Ti cross-section to carry the current, hence the filler. And the filler also precludes any electrolyte creeping up the tube if the end that is pinched closed isn't quite done properly.
pdfbq Posted October 24, 2012 Posted October 24, 2012 (edited) I may have missed it, but what current were you running? Power loss isn't so much of a factor as it is simple heating. 250W at ~5V means 50 amps. Sure, your round shafts are better and seal better, athough I don't have much problems with gluing mine in and seal with silicon.I just responded to the statement that Ti has only 3.1% of the conductivity of copper.This looks as a huge problem, the only thing I wanted to state is that most of the time it is'nt. About heating of the Ti straps. If ther're too thin/small you will probably get into trouble due to the temperature coefficient. It the strap gets warmer the resistance goes up which generates more heat etc...Bigger straps have enough time to loose this heat befor it builds up (and they generate less heat to begin with). As far as no spot welding - if you use titanium bolts and nuts, AND clean the joint thoroughly using abrasives to strip all oxides, AND tighten the nut and bolt to a point where the joint nearly deforms, it'll work. Otherwise, electrolytes will creep between the metals, oxidize the skin, and kill the continuity. The strange thing is that this is not what I experience. I just put the MMO between the strap and a little Ti plate and clamp it together with some small Ti strips.Is seems to stay OK and I am testing this. You really have to just clamp it a bit and it easy takes 25A.After a run I opened this connection and it just looked as new. I have another problem though and that is that still my anodes get poisoned in a way. I'm now thinking its the hard water I'm using.The first run goes without any problems (from fresh brine) but when I boil it down to extract NaClO3 and add new brine, this run is putting white smut on the anode and I can not get rid of it with 30%HCl. I will star a fresh run with demi water only now.. see what happens. Luckily I have a lot of MMO (still have your DeNora anode in tact by the way) so can experiment without much loss. Edited October 24, 2012 by pdfbq
WSM Posted October 26, 2012 Posted October 26, 2012 I have another problem though and that is that still my anodes get poisoned in a way. I'm now thinking its the hard water I'm using.The first run goes without any problems (from fresh brine) but when I boil it down to extract NaClO3 and add new brine, this run is putting white smut on the anode and I can not get rid of it with 30%HCl. I will star a fresh run with demi water only now.. see what happens. Hi pdfbq, I'm not familiar with that term, what is demi water? If you mean distilled or deionized water, then I understand. I've used distilled water and had good results. I even use purified water from an RO system (reverse osmosis; for household use, not industrial) and it seems to be much better than straight tap water. For me, personally, I'd rather limit the unknowns that go into my cell (as far as possible while using commercial KCl), and I know my tap water has 300ppm-400ppm dissolved solids before I filter it. I suspect those to be mostly iron, calcium and magnesium, and I'd prefer to limit those. After filtering, my water has less than 20ppm dissolved solids. WSM
Mumbles Posted October 26, 2012 Posted October 26, 2012 Demineralized is what I assumed it was. Same thing as Deionized as far as I know.
WSM Posted October 26, 2012 Posted October 26, 2012 Demineralized is what I assumed it was. Same thing as Deionized as far as I know. That makes sense. Thanks, Mumbles. WSM
Swede Posted October 30, 2012 Posted October 30, 2012 The strange thing is that this is not what I experience. I just put the MMO between the strap and a little Ti plate and clamp it together with some small Ti strips.Is seems to stay OK and I am testing this. You really have to just clamp it a bit and it easy takes 25A. After a run I opened this connection and it just looked as new. If it works, it works! There's no arguing with success. I've seen MMO pollution when operating with soda glass cells, and there was some conjecture that the alkaline electrolyte can cause glass to literally fuse to the anode. If pH control is done, then this should never be a problem, nor should it with good borosilicate glass. And yes, it could be the tap water. I've always used tap, but we do have nice soft tap water here in Texas. The other reason I'm using tap is because the KCl I'm starting with is FAR from lab grade stuff. It's crude water-softener grade, and it already carries its share of impurities, so a bit more isn't going to hurt. Again, chlorate xtals (when starting with KCl) are big, and very, very easy to wash. A good wash should eliminate most impurities. Starting with sodium presents its own challenges, and I'm guessing the potassium metathesis reaction makes some smaller xtals, which aren't going to be as pure as the slowly grown bigger ones, so starting with purer precursors makes sense.
taiwanluthiers Posted October 30, 2012 Posted October 30, 2012 How do I wire an ammeter to the cell? Do I wire it series or parallel? The meter has a + and - terminal.
WSM Posted October 30, 2012 Posted October 30, 2012 How do I wire an ammeter to the cell? Do I wire it series or parallel? The meter has a + and - terminal. In a DC (direct current) circuit, you wire a voltmeter in parallel and you wire an ammeter in series. You also use a DC shunt to protect your ammeter. The shunt passes all but a measured amount of the power to the cell so the ammeter only gets a limited amount of voltage (usually 50 or 75 millivolts) and accurately measures the current flowing in the circuit. The supplier of your ammeter should provide a wiring diagram. Contact them and see. WSM
taiwanluthiers Posted October 30, 2012 Posted October 30, 2012 Sorry, it was some chinese stuff with no diagrams, how do I shunt it? The stuff is rated up to 30A
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