leaking solder joint- pointers

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rye-me-a-river
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leaking solder joint- pointers

Post by rye-me-a-river »

All -- just joined the forum and have a few questions of the newbie variety....

I am just commissioning my first still, and don't have a lot of experience with Soldering. I ran a vinegar solution through the still yesterday and was overall pleased with what I saw. Except one seam looked like it had a few bad spots -- this is high up in the 2" column, just before the 90 degree and my reducing section. I could see just a bit of vapor coming from this area: as I looked closely I can tell where the leaks are because the vinegar condensate did me the courtesy of discoloring (cleaning) my copper as it ran out. There are about three spots like this on this joint and so my questions are the following:

1. I am running a propane burner and am cognizant of a potential interaction between alcohol vapor and the flame, but maybe this is so miniscule as to not to worry- ie, is this the type of thing that is best addressed with paste on a case-by-case basis (I am not sure my OCD will allow that....)?
2. Assuming I want to fix the joint, what is the best process for re-soldering: do I need to try to take apart the joint, clean and resolder or can I spot-solder by melting, fluxing?

Thanks for any advice....

CMAR
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StillerBoy
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Re: leaking solder joint- pointers

Post by StillerBoy »

From what I can observed, you tried to melt the solder, which is what most beginners do.. you need to apply heat away from the area you intend to solder, in other words, at a joint, you apply heat ( the tip of the blue flame) on both sides of the joint, not at the joint, which has been clean and fluxed with the appropriate paste.. as you heat the joint, you touch the solder at the joint, if it melt, it will run.. if the joint is still too cold, the solder will not melt, continue to heat the joint, and at one point the solder will melt and solder the area..

To re-solder your joint, first clean it as best as you can with some steelwool, clean, then added some paste, and heat as mention about.. at one point it will become liquidity, and seal the joint..

Apply heat away from the area you intend to solder.. if your paste start to smoke, you are heating it to fast, or you are applying heat directly at the paste or both.. the trick is to heat it up slowly, and on each side of the joint..

Mars
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HDNB
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Re: leaking solder joint- pointers

Post by HDNB »

solder also flows by capillary action towards heat. so apply the solder to the far side of the joint from the heat...and the heat will pull it around.
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rye-me-a-river
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Re: leaking solder joint- pointers

Post by rye-me-a-river »

great -- I'll try that this week after the column finishes drying out. thanks for the advice!
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Oldvine Zin
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Re: leaking solder joint- pointers

Post by Oldvine Zin »

HDNB wrote:solder also flows by capillary action towards heat. so apply the solder to the far side of the joint from the heat...and the heat will pull it around.
+1 :thumbup:
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Re: leaking solder joint- pointers

Post by zapata »

No leaks are acceptable, fix it for sure.
Agree it looks like the parts werent hot enough to melt and wick the solder. I've fixed similar so it is possible, might be easier with liquid flux like harris/radnor stay clean. I think the liquid flux is more likely to soak into the small gaps better than paste. Just soak all around the joint, inside and out, from various angles to really get the flux inside the joint. You can get a small bottle of stayclean in a <$10 kit from most welding suppliers, or internet of course. Then heat up everything evenly and target the heat as the boys said after everything is pretty warm. I like a 2nd heat source in addition to the torch. A heat gun blowing through or across the tube for example gets everything uniformly warmed up and makes it easier for me to work the torch without the mass of copper sucking all your heat away. Even preheating the whole thing in a gas grill at about 250-300*F works well, though it depends on the size of that piece and what else is attached to it.

If you have well soldered joints nearby, wrap them in a wet rag so you don't undo them, though if they are all look like that it might not hurt to reflow the solder anyway.

One of my first solder projects was my cross flow condenser, and a lot of the joints werent pretty, but held pressure. After 10 years or so of use a few joints developed leaks and I managed to get them fixed as described. Luckily I caght them because I've adopted the habit of pressure testing every rig before every run right before power on. I just put an inflated balloon on the condenser (and vent if reflux) and leave it to leak down if it will while I sort out collection jars, gather reading material, make a sandwich, take a leak etc. Was blown away to 1 day find leaks in my old reliable still head and thankful for catching it safely. I thought it'd be far more likely to catch a mis-seated triclamp than an old solder joint. Now I'll definitely pressure test for every run forever, even if I don't see another leak in 20 years.
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Oldvine Zin
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Re: leaking solder joint- pointers

Post by Oldvine Zin »

:thumbup: to what zapata said. A mistake that I see quite often with newbee soldering is trying to paint on the solder like it was a brush, instead you should use the flame as a brush to move the solder. Solder will follow the heat if the temps are right.

Good luck and stay safe
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Expat
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Re: leaking solder joint- pointers

Post by Expat »

Wise master plumber I once knew said, Solder should be used like an ice pick, not like a paintbrush.
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