Help! My boiler leaks

[Wrecks]

I'm about at wit's end trying to patch the leaks in my boiler and need suggestions. It's a 3/4" scale climax as designed by Kozo Hiraoka. I've been plugging leaks for about a dozen heating rounds now, and I've got one leak that keep recurring, and one that's just really hard to get to. The leaks are very small, the boiler will hold 100PSI for several minutes. I'm using a big sievert propane torch, with a 32mm tip.

The recurring leak is on the foundation ring. That's the first picture. The solder looks good, but the water springs from the center of an apparently solid flood of solder. When I patch this, I've been using a dremel to grind down to bare copper, then melting a 1/4" piece of solder where the leak is. Three times, same result. I don't understand. On this leak, I don't know what to do other that keep trying. Any suggestions?

The hard to get to leak is inside the firebox, around one of the flue pipes, way in the deepest corner. It's shown in the second image. I can't melt solder back there. The flame doesn't want to go way inside, and the whole inner box heats up.  The solder just won't melt in the back, but I'm afraid joints will melt in the front. With this leak, I think I'm going to heat the whole inner box up as much as I dare and then use a spot torch with mapp and oxygen to melt a ring of solder.

Does anyone have any other suggestions? I've come too far to fail. I'm very worried.

My wife suggested radiator stop-leak, and after I told her that I couldn't do that, I started wondering why I couldn't? Why not?

The third image is a shot of my dog checking out my progress to date.

[crueby]

Back when I did my New Shay, that foundation ring was the one I struggled with the most. Grinding it out to the bare metal was the right thing to do, gives the best chance to fix it. One possibility - you mention it was a big area of solder, is there a large gap that you are filling with the solder? If so, a better way would be to grind it out again, and make a small copper piece that fills the gap closely. The silver solder is not good at filling voids, anything more that a tiny crack needs to be filled with metal first. I have had a number of places like that with a seemingly narrow gap that the solder would not fill properly, only solution was to hammer some copper wire flat and push it in, then solder it again.

Which silver solder and which flux are you using? I find that for repair spots like that it works better if I use the 'Easy' or 'Extra Easy' grade of silver solder, since it melts at a slightly lower temperature but more importantly it seems to melt to a lower viscosity and flows into gaps better. For flux, there are a lot of choices, I've settled on the Harris Black flux, before that I was using the Tenacity 5 white flux, before that the Harris White. Each step up gave longer heating time before the flux burns off and stops working.
Hope some of that helps. The model overall is looking great!
Chris

[Wrecks]

I'm using Harris Safety Silv 56. I am also using the black flux. And yes, under all that solder is a relatively large hole, maybe 15 thousandths wide. I was hoping that once I'd filled it with solder it would quit being a problem. If I can find it, I could drill it out and insert some wire.

[crueby]

Yeah, thats pretty wide to fill with just solder. Better to fill it with some copper first - either hammer some wire flat, or trim a slice off a larger bit of scrap and file it to fit. Thick chunks of the solder tend to hold gas bubbles and such, you want to have gaps down to just a couple thou.


As for the other leak up inside the firebox, I had similar issues with staybolts up there, finally got lucky. I don't have any tips for that one.

[Jo]

As for the other leak up inside the firebox, I had similar issues with staybolts up there, finally got lucky. I don't have any tips for that one.

Make yourself a boiler tube expander and expand the tube a little against the inner tube plate.

Jo

[john mills]

for those spots the gas torch will be hard to get the local area .I use the gas to generally heat the whole boiler the last bit use a oxygen acetylene to bring the local area the last higher temperature it can get at those inner places while the gas supplies the main heat
that is were a helper is needed. don't try all the heating with the oxy torch it is too concentrated and too higher temperature but can bring those local area a little hotter to make the spots that don't want to run properly.
john

[Firebird]

You have my sympathies.

I'm currently battling with a Sweet pea boiler which can be seen on the Sweet pea face book page.
As well as the usual propane torch I have oxy/propane torch as well which will get into tight spots without extinguishing.
I also have a long neck sievert torch which will work in enclosed spaces. See Cup alloys web site (usual disclaimer) for details.
The Sweetpea boiler is my 3rd boiler and I have had issues with all 3 but patience is the key, you will get there eventually with it.

Good luck, stick with it.

Cheers

Rich

[Wrecks]

Thanks everyone for the advice and encouragement.

I worked on the foundation ring this afternoon. The image shows the pits I found under the solder. I drilled these out and filled the holes with copper rivets. This has corrected this leak, but another showed up right beside it on the inner vertical seam.

I've got a buddy coming over Monday and we're going to tackle the tube wall joint. I'll need four hands. I'm going to make some shields for three of the four firebox walls and heat up the tube wall with the big propane torch. Then, I'll try to melt the solder with a mapp-oxygen torch.

The boiler has had just these two problem areas for the last 4 heating cycles, and I've had it up to 100PSI during testing. I need to go to 200psi for the final pressure test. Do I need to be concerned with all this heating and cooling? Are the other joints getting brittle?  I'm worried that when I go to 200, it'll release a flood.

[crueby]

You don't have to worry about the  copper getting brittle, heat just anneals it, unlike steel where it hardens with proper heat and cool cycles. Copper and brass only harden with working it, hammering, bending, etc.

[Wrecks]

Well, I botched it. I used the shields, and they worked great. I exposed the area I wanted to repair and blasted the interior of the firebox. The exposed area melted solder with no problem. After the first small repair on two tubes, I still had a leak so I decided to do all the tubes. I thought this worked great. The entire tube area was flooded with solder. But I had reused the shield sheets and they were steel. A large amount of fire scale dropped off the sheets into the melted flux and solder. On testing, I had many more leaks now. It was as if the solder were porous. I don't really know if the debris caused it, but the solder looks really bad.

I made a few mistakes with this boiler. It was a bit twisted and some of the bushings weren't exactly where they should have been, so I don't feel too bad about starting over and applying what I've learned to make a better one. Except that I REALLY don't want problems inside the firebox and I'm not sure why they showed up.

One thing I noticed is that none of the threaded ends of any of the stay bolts leaked. Maybe the threads help with the solder sealing. What if I threaded the firebox ends of the tubes? Could that help prevent tube leaks in the firebox?

Also, Kozo specifically says to use a small amount of solder for repairs. I've worked under the assumption that more solder is better. When I repaired, I'd always attempt to solder a whole segment, not a spot. Which is better, spot repairs or area repairs? In general, is more solder better than less solder?

[crueby]

Ouch!

I gotta go with Kozo on this one (as in most things). The strength of silver solder is inside a clean close fitting joint. Extra pools of solder on the surface do nothing but waste solder and hide other problems, it adds no strength to the joint. As you mentioned, the threaded stay rods/bolts worked well as is - they are a nice close fit with surface area between the two pieces where the solder can wick in. The hard solder, unlike soft electrical solder, does not fill wider gaps with any strength, it will stretch and crack in thick sections. The wicking into the joint is key - when you heat up the two pieces of metal, after the flux goes clear, you can see the solder flow and wick into the joint. It wants enough solder to flow all the way through the joint, but not a lot more. Same with heat - after it flows well, you dont want a lot more heat for a long time, though if there there is not an even heat, the solder will flow onto and stick to the side that is hot enough, and ignore the other piece that is still too cool. Its an art of balance. If you've ever used superglue, some of the same lessons apply - a clean thick close fitting joint with just enough glue, too wide a gap or a knife edge on one side or a big blob of glue doesn't work. Dirt or oxidation/ruse are bad too, will prevent a solid connection.

[Wrecks]

Thanks, Creuby. That makes a lot of sense. And it’ll save me a lot of money spent on solder.

[tghs]

can't remember where I read it, most likely when researching boiler making,, something to the effect of "you use enough solder to make nice tight joints, no so much as your final product needs hallmarks"

[rick41]

Wicking Loctite will plug small boiler leaks.
Rick

[crueby]

Wicking Loctite will plug small boiler leaks.
Rick

But won't the heat break it down? Especially around the firebox area.  How hot can the wicking type resist? Could be good for pipes and other fittings if its okay above the temp of the steam. Which number loctite is it?

[rick41]

I used #290 to seal several pinhole leaks in my Rob Roy boiler.  Worked very well.  The temp range for #290 is up to 300F.  Steam temp is 324F @ 80 PSI,  350F @ 120 PSI.  I realize these temperatures are higher than the working temp range of the loctite.  However, my belief is that those temps are for failure of a Joint.  To seal a weep in the boiler you just need to get a sealant into a very small gap.  There have been many "fix's" for weeping leaks such as ginger etal.  The reason I chose wicking loctite is because it will wick into the gap.  Loctite #272 is rated up to 450F, but I don't know if it will wick in as it is recommended to apply before assembly.  My gut feeling is it would wick enough to seal a minor leak.  Just my thoughts. 

[rick41]

https://modeleng.proboards.com/thread/14064/loctite

check out this site for more discussion on using loctite to seal boiler leaks.

Rick