Will propane flame melt copper brazing?

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I have a heat exchanger made up of stainless steel plates brazed together with copper filler. I have collected some crud inside the exchanger that I can't for the life of me get out. I was thinking of just placing the heat exchanger on my propane turkey fryer on low for an hour or so to try to incinerate the crud inside and turn it into ash. However, I don't want to melt the copper brazing and make the unit useless. I have little experience with brazing, and never with copper. Does anyone know if a propane flame will heat the brazing to the point of melting?
Thanks.
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On Mon, 11 Apr 2011 09:17:45 -0700, Smitty Two

My turkey fryer is about 3700F. It cooks a turkey in 3 seconds.
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Learn how to clean HVAC components like a professional...
You are either using the wrong cleaner, the wrong cleaning tools OR not repeating the process enough times...
If you have removed the component from its normally installed location you could consider attempting to clean it in the dishwasher if it will fit, or pressure washing it...
~~ Evan
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I actually use this device for homebrewing, so it is already off the intended use. I could use caustic soda, but would prefer to do this without chemicals. I doubt that the flame is really 3700 degrees, as that would likely melt the stainless steel as well, and I know that's not the case.
Anyone else?
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most likely it is proteins that coagulate out of the solution when the hot beer (wort) cools quickly along with little bits of hops that aren't caught in the pre-filter before entering the heat exchanger. They probably started getting caught in the channels of the heat exchanger but I didn't notice until liquid got caught in there as well so I could hear it when I shake it. I've tried boiling in trisodium phosphate, soaking in oxyclean, acid-based cleanser, bleach, turning a pressure washer on it, and baking in the oven at 400 degrees for an hour. Nothing can seem to get these deposits out....so I thought to try incinerating them.
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The adiabatic temperature is actually 3596 degrees. The fact that the flame is that hot does not mean it will instantly melt the metal. You have to take in the factors for conduction, thermal mass, etc.
Given your lack of physics knowledge, good chance no matter what you do you will f--- it up. Uneven heating can cuase other problemsw ith warping. I'd use a caustic cleaner and boil it out. Try a radiator shop.
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Also note that that is the temperature of the hottest part of the core of the flame. Unless you have your exchanger a few millimeters from the burner it won't experience anything like that temp. But I can't really give you a useful approximation of what you WILL get.
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Yeah, I *DO* have something else...
Ask a rather dumb question without completely outlining your problem and how you are using something in a NON-Standard application and then complain at the replies...
Ok...
I was correct... You are using the wrong cleaner...
You need something which will strip all biological residues off of a metal surface... You are looking for specialized cleaning chemicals used for crime scene clean ups and scouring/cleaning hospitals...
You will have to find a local source for industrial cleansers as that is what you need, you maybe homebrewing, but that is an industrial process and you would therefore need industrial cleaners to deal with the leftover residues because your dish detergent and the stuff you can buy at Home Depot just aren't going to cut it...
~~ Evan
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Thank you for your reply. I go back and forth between trying to provide too many details and just the basics. If I say everything I tried up front, and the specifics of my setup, then someone is sure to tell me how dumb I am for doing what I've already tried instead of helping me fix the problem.
TO give the details - The unit is self-contained with four garden hose connectors - two for cold water and two for hot beer (wort). That is the only access I have to the insides, which consist of 20 plates (10 water, 10 beer). I will try pressure washing, as well as using some industrial cleansers. I know other homebrewers have used caustic soda with great results so I guess I will give that a shot.
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Try washing soda first -- it's a lot more caustic than baking soda, but not nearly as dangerous as caustic soda (aka lye). If you do use caustic soda, make sure to wear rubber gloves and eye protection.
Washing soda is available in many grocery stores on the same aisle as laundry detergents. The most common brand is Arm & Hammer -- the box looks pretty much like the familiar box of Arm & Hammer baking soda, except it's a lot bigger.
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snipped-for-privacy@example.com (Doug Miller) wrote in wrote:

do you mean "borax"? (sodium tetraborate)it is often used as a brazing/welding flux. best to mix with boric acid,from what I've read,75/25 ratio is good.

Or 20 Mule Team Borax.

propane is not hot enough for brazing,but OK for soldering. you need oxy-MAPP or oxy-acetylene for brazing.
--
Jim Yanik
jyanik
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No, I mean washing soda (sodium carbonate).

Which is, obviously, borax, NOT washing soda.
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Not exactly. Others have said that caustic soda run through a recirculating pump will eventually eat through the crud, but I have no pump to do this. So I propose to try just putting the exchanger into a heated bath with caustic soda in it. I have no idea if this will be successful or not, therefore I thought I would solicit opinions on the incineration idea.
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I'd sure try washing soda first. It's quite effective, and much cheaper and much safer than lye.
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Soaking in a stagnant bath will remove some of your build up...
However, it is when you circulate a warm solution through the inside of the device you need cleaned that you will have the best performance -- the circulation of the cleaning solution provides a scouring action...
How do you circulate your beer and water through this heat exchanger ?
Probably worth investing in a small pump which you can get with hose threads on it for cleaning your set up...
~~ Evan
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On Apr 11, 7:43pm, "Stormin Mormon"

You can solder with a propane torch, but you can't braze. Solder melts around 450F, brazing at around 1200F. That's why you need a MAPP or acetylene torch to braze. Also, with something large like a heat exchanger, it's obviously going to be capable of dissipating a lot of the heat coming off that turkey fryer.
So, my answer would be it won't have sufficient heat to effect the brazed joints. If you want to do a test, get a piece of brazing rod and hold it on the flame. However, I also agree with others that have suggested there may be a better solution, eg a solvent, that could get the crud out, depending on what it is. Depending on what it is, the fire approach might just turn it into crud that still will not come off.
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snipped-for-privacy@optonline.net wrote:
<SNIP to here>

<SNIP from here>
I have brazed with propane before, though generally only on smallish things. I find brass braze and bronze braze to require temperatures that achieve a glow of "cherry red", which I consider a "dimmish neon slightly reddish orange". As in around 1500 F.
A turkey frier sounds to me like closer to one of those things used to melt lead for soldering in-street plumbing that gets soldered, or whatever it is they use those burners for. I think one of those can probably be used to disassemble a brass-brazed-lugged bicycle frame, though maybe with some difficulty.
Then again, is the heat exchanger brazed with brass or bronze braze, or is it silver-soldered / silver-brazed? "Silver solder" ("silver braze") melts at a lower temperature than brass and bronze brazes do. If the heat exchanger is silver-brazed, then I think a turkey frier's frame can melt the braze.
Now for another thing: Why use a turkey frier rather than a propane torch? Using a turkey frier even as directed seems adventurous enough to me, let alone abusing a turkey frier. That sounds to me very adventurous, possibly outright dangerous. A propane torch sounds to me so much more suitable. I wonder if the OP is trolling.
--
- Don ( snipped-for-privacy@misty.com)

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The specifications say that the unit is brazed with 99.9% copper and the plates are made up of 304 stainless steel. Just for reference, the unit that I'm referring to is shown here: http://www.dudadiesel.com/choose_item.php?id=HX2330BWC
I get the impression that the term "heat exchanger" means different things in different applications, so I apologize for the confusion. I actually got my hands on some 100% pure lye and tried making a solution according to the directions on the bottle mixed 1 Tbsp to 1 cup of water and let it sit in the heat exchanger for 30 minutes. I heated it up to about 160-180 degrees but again, had no method for agitating the solution inside the device. After 30-40 minutes I rinsed and the solution was slightly bluish in color - I'm guessing a reaction to the copper...but it was still clogged. Do you think I should try again with a stronger concentration?
As for the torch vs. turkey fryer, I just thought that a torch would have to be swept over the exchanger to make sure I was heating evenly, while a turkey fryer would apply heat over more of the unit at one time.
I have considered one of those drill-powered pumps, and maybe I will try to pick one up to see how it works as I know that the agitation is one of the key facets I'm still missing. My only issue is that I don't know what the insides are made of and don't want it to melt with the lye circulating through it. Thanks again everyone for your suggestions, even those who are a little forceful with their responses!
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Matt wrote:

<SNIP from here>
Should this be correct, then I would only slightly fear ruining this thing with a propane flame, even one by a turkey frier.
I have melted copper wires with propane torches before, but not any substantial copper objects. Copper requires over 1900, nearly 2000 degrees F to melt. That temperature achieves a bright yellow-orange, almost orangish-yellow glow.
My experience is that a propane flame cannot melt even fine wires of most grades of steel, but can melt fine wires of a few, nothing steel more substantial than fine wires. Different steels melt at different temperatures generally ~2300-2700 F, which results in a glow getting into put-a-spot-in-your-eyes brightness with color of whitish orange-yellow.
Mere "red heat" may tarnish some stainless steels, and there is some chance of "thermal shock" causing a crack in or adjacent to one of the braze joints. I would worry about that more than about melting 99.9% copper braze, if the documentation is correct.
--
- Don ( snipped-for-privacy@misty.com)

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Mix enough solution to fill it and immerse it. Put it on the turkey fryer and let it boil for a half hour. Attach an external line out of the pot and you may be able to pressurize one side to for the liquid through it.
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