Quote:
Originally Posted by AC_Hacker
And as an additional factor, the HX shoud have sweat fittings on one side. My curent HP has a slow leak, and it looks like its coming from a pipe-thread fitting. There may be a way to seal it up but I don't know what that way us yet... teflon tape seems to have its limits.
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Have you considered 45% silver rod and just brazing up the fittings? You need some good flux and quite a bit of heat, but it should be doable with Mapp gas. I've certainly brazed copper-brass-steel here by just brazing up the fittings after they are screwed together.
You have to be _really_ careful brazing up to brass though. I melted the first two fittings before I got the temperature right. It became _much_ easier when I used 45% silver rod though.
I know you can braze pretty much anything to anything with the right rod and flux.
The problem you get with interference fittings like you are using (even with teflon tape) is the uneven coefficient of expansion of the metals when subjected to extreme temperatures. You screw them together nice and tight at ambient, then you shove evaporating propane into them and drop them right down below the frost point. The brass shrinks slightly more than the steel and you have a leak.
For leak detection, add plenty of glycerine to the soapy water. It sticks around _much_ longer and you get to pick far slower leaks. There is better stuff available from refrigeration suppliers that appears to defy the laws of physics with how long it leaves a workable film, but glycerine is cheap and you leak sounds like it's big enough to be picked a bit more easily.
I've been watching this thread pretty closely as it's similar to something I've been working on myself. I'm lucky enough to have a huge aquifer about 8M under my place, so I have a couple of separated bores and loads of 20 Degree C water to play with. I'm rejecting heat into it rather than sucking it out however.