soldering aluminum

[Larry]

My ice cream machine coil is leaking where the aluminum tubing is soldered to the evaporator shell.  Does anyone have any advice on products that they have tried and worked under pressure for aluminum? 

I never soldered aluminum before.  With the low melting point and oxidation aluminum is tricky.  Any tips on soldering?

Luckily I have a spare ice cream machine coil (doesn't everyone) and so far it is holding 200 PSI of nitrogen.  I would still like to repair the bad coil and store it away.

[mznb1u]

I am not an expert on the subject but would JB Weld work for that?  I believe they make a JB Weld product for aluminum.

  Tim

[Larry]

I don't know if it will work or not.  I'm trying to find a product that works 100%.  The ice cream evaporator is a pain in the but to remove.  You have a four foot high evaporator and about a five foot capillary tube and at least six feet of 3/8" tubing.  It's really a struggle removing it without crimping a line.  

The other coil failed the pressure test too.

[bubba]

Aluminum can be tig welded.. I'm not sure of the reaction with the oil inside the line with the weld.. I wouldn't trust any putty to create a leakproof seal.

[tkaz]

What about brazing with a propane torch?  I haven't done it before, but there are a lot of products out there, Alumalloy comes to mind.  I think it would be worth a shot.

[bubba]

I've seen that stuff, and I've tried using it a few times on some thin aluminum tubing... With aluminum, there is no real warning signs before meltdown when using a torch.. when you heat steel, brass, copper, it turns colors before any major meltdown. Aluminum goes from solid to mush pretty quickly. I'm not very experienced with it, but I don't think its easy..

[loman4ec]

silver solder is the only thing to use to solder refrig lines. I use a mapp any oxy torch and silver solder.

[Larry]

Thanks for the advice.  I knoe soldering aluminum is tough because it goes from solid to nothing in a flash.

Years ago I worked at a factory that had some form of epoxy.  I don't know what it was, but I had a friend that had an aluminum coil that was leaking and I put this over the spot and his air conditioner still works after fifteen years or more.  This epoxy was made for their metal switch gear, it wasn't your average store bought mixture.  Plus what really helped is that I used a vacuum pump on his lines until the epoxy dried.  So instead of just covering the hole, I'm sure some got sucked in to plug the small hole.

My leak is where the aluminum tubing was welded to the aluminum shell.  I might put a vacuum on and melt a bead along the edge.  It is such a small leak.  I used the machine for months and it was fine.  I couldn't find it with soap and bubbles.  I found it when I submerged it in my pool.  There was a bubble every ten seconds, only if the coil was pitched.  Standing up, sometimes it leaked, and other times it did not.

I haven't submerged the other coil yet.  I'm hoping it is a copper leak.

[Ltransam]

   Hey , Larry
                Sorry to hear Your Problem . At My Shop We haveused a Epoxy Named Devcon (I beleive You can Find it in McMaster Or Granger ??)  After it Set We can Drill & Tap It .I used it in the Bottom Pan to fill in Small -Medium Holes Still there 10 years later .But I would Have No Ideal How it Would Hold under Pressure ?  Pluse I would Mix it & then wait till it sets up a Bit .Because It Might just flow in the Hole & not Plug it .But Something to Check On 

                                                          Leonard

[Yarochrehc]

There is a two part epoxy made to repair aluminum evaporators in refrigerators that when properly cleaned and applied will last for years that will work on your leak problem. It is available at most refrigeration wholesalers, Grainger might still have it.

Putting a torch to the aluminum will usually distory it.

[Larry]

Allright I have done a little web surfing and I narrowed it down to two epoxys that should work.  Just wondering if anyone has used either of them.

Red epoxy - two part epoxy that turns red when mixed.  Can cure in by itself in two days or can be cured by using a heat gun.  The curing is complete when the epoxy turns gold.  Temperature range is -100F to 300F, bursting strength 6,000 PSI.

The other one is:

LA-CO - Heat Seal Stick.  A green pre mixed epoxy that is applied when the coil is warmed by a heat gun.  It melts on the area like a warm crayon.  Temperature up t 350F, pressure 450 PSI.

I have read great reviews on both products from different forums.

The evaporator pressures are extremly low.  The highest pressure would be when the machine is off.  The pressures will equalize and they will be what R-12 is at room temperature.  So pressure is not a factor.

Leonard I also found the product that you were talking about, but in the forums that I read, a few people heard of it but never tried it.  It seems like some pretty amazing stuff.

[SIGNGUY]

JOHNNY MAYS HERE TO TELL YOU ABOUT MIRACLE PUTTY>> MIRACLE PUTTY IS AMAZING AND WILL STICK TO ANYTHING,, NEED TO FIX A REFRIDGERATION LINE IN YOUR VINTAGE 1950'S ICE CREAM VENDOR.. MIRACLE PUTTY WILL DO THE TRICK, NEED TO MEND A BROKEN WING ON YOUR 747 AIRLINER... MIRACLE PUTTY WILL GET IT DONE.. GOT A CRACK IN YOUR GOLDEN GATE BRIDGE.. MIRACLE PUTTY...

YOU GET THE DRIFT...

JUST A SUGGESTION?

[Larry]

I actually had a friend that bought that product and gave me a tube.  I tried it on numerous things at work, and they all failed.  It has to be a product that works!!!

I ended up buying the red epoxy.  Well see what happens.  I'll try to use it soon.  I have a previous appointment with the wifes dryer afterwork.

[Larry]

Well, I took the coil into a welder and he would not touch it.  He was afraid that the leak would seap out of the sides afterwards.  He suggested a radator guy so they can dip it and then weld it.

The radiator guy said that he wasn't interseted in fooling with it either.  He recommeneded epoxy, and suggested that after I clened the area for an hour, to clean it some more.  Plus, most epoxies state that you can use the coil right away.  His advice was to leave it set overnight.

So I cleaned the coil with a wire brush,scotch brite, sandpaper, acetone, and the finally my Dremel with a wire wheel.  I leak checked it and all tha cleaning must have fused the leak.  It didn't leak after that.  So I recleaned all the soap off, heated, scuffed, and re-acetoned (a new word I made up) the coil, like the epoxy instructions recommended.  I ended up using the red epoxy and a heat gun.  Plus I put the coil in a vacuum so if there was a slight leak it would hopefully draw some material in the pinhole and plug it.

I followed the directions and it said that it was cured after the epoxy turns gold.  Just for a referance, it is red, then it turns purple, then gold.  Anyway, it is cured when it is gold.  So I took the radiators guys advice and let it set over night.  Pressure tested, vacuumed, and charged the coil.  It works great. 

[bubba]

Excellent.. Glad to hear there was some way to save the coil... hopefully it will hold up..