Firetube Boiler Project - Leak Troubles

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Blondihacks
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Firetube Boiler Project - Leak Troubles

Post by Blondihacks »

Hello everyone!

I come to you all seeking assistance with my boiler project. It’s a 4” vertical fire tube design with 26 tubes, based on the ones in Alex Weiss’ book. Operating pressure will be 60psi, so I’m looking for 120 on the hydrostatic test. I knew silver soldering it would be the biggest challenge, so I’ve been meticulous in preparation. Every joint has a verified 1-3 thou clearance, everything was spotlessly clean, and I have a good hearth. This is my second boiler. The first was a 4” pot boiler with a handful of fittings in the shell, and it was challenging, but I got it done. This boiler is more challenging, but I felt I could do it.

I am using the Sievert propane torch that many people recommend (especially Kozo), with both the 1” and 2” tips. It has no difficulty getting the entire boiler up to temperature in a minute or so, so sufficient heat is definitely not a problem. I am using Safety Silv 56 silver solder (1/16”) and their matching white flux.

I started by trying to silver solder it using the method in Alex Weiss’ book. Essentially “all at once”. He recommends setting up all the parts, fluxing every joint, putting a ring of solder around every joint, then heating the whole thing up to silver solder temperature all at once. This seemed to work pretty well- I got nice looking joints for the most part, and only had four leaks initially- two tube ends and a couple of spots around the tube sheets.

That’s when everything went sideways. Every time I tried to fix one of those leaks, I created two more. I spent weeks fixing leak after leak, only to have another joint crack somewhere else. I have redone every joint probably four or five times at this point. I can’t figure out how to fix a leak without creating a new one.

Things I have tried:

1) Fluxing and reheating the entire tube sheet so everything reflows nicely again. This generally fixes a couple of leaks, but creates new ones.

2) Adding solder and doing #1 again. Similar results, but now there’s a lot more solder around.

3) Heating just the area of the leak, protecting other areas with fire brick or ceramic wool. I succeed in fixing the leak, but the heat shield doesn’t prevent cracking other joints.

4) Heating up the entire boiler to near solder temperature with propane, then heating just the leak area with my small acetylene brazing torch. This tends not to work at all- the acetylene brazing tip can’t heat the area faster than the heat bleeds away and you never get the solder to flow.

5) I have tried all the above with more heat and less heat, using variations of the 1” and 2” tips on the Sievert.


I pickle in Sparex #2 for 5 minutes and wash in water before and after every solder attempt. Everything is clean at all times.

I have tried Kozo Hiraoka’s method of heating up one joint at a time, and Alex Weiss’ method of heating the whole thing up at once. I know that you need to heat the back of the joint or the metal near the joint, not the solder itself so that the metal will pull the solder into the joint. However, with a tube sheet in an assembled boiler, this is impossible, so I am forced to heat the joint from above which I know is not ideal. I know now that I should have soldered the fire tubes into the tube sheets first, then soldered that assembly into the shell. However it’s too late for that, and surely I’m not the first person to need to fix a fire tube leak after assembly?

At this point, I am seriously considering cutting the whole thing apart and starting over (or giving up). I’m completely out of ideas and I have been at this for over a month, just on leak fixing alone. I’ve gone through 30lbs of propane, 2 MC tanks of acetylene, and nearly $100 of solder in the attempts. I have hydro-tested it 30 or 40 times. This may be the most expensive model boiler ever built.

At one point I had it holding 100 psi with one remaining seeping tube, but then trying to fix that last leak created three more much worse ones and it has been an endless downhill cycle like that ever since.

If anyone has ideas, I’m all ears. If you want details on all the prep work and setup to confirm I did things properly, I have done a video series covering everything I have done. I won’t post it unless asked, since I’m not here to solicit traffic for my YouTube channel. I’m just looking for help with this project.

Thank you in advance for any advice anyone has.

-Quinn
hoppercar
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Re: Firetube Boiler Project - Leak Troubles

Post by hoppercar »

Reminds me of what ol bob Maynard always said,.....I would rather build 3:steel boilers than 1 copper one
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Harold_V
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Re: Firetube Boiler Project - Leak Troubles

Post by Harold_V »

Speaking from the perspective of a guy who used to refine precious metals, one of the reasons (alloyed) gold is refined is because the base metals contained within are oxidized when it is melted repeatedly. The user experiences inclusions that may not be obvious until such time the item cast is polished. Once that happens, there's not much a person can do besides diluting the existing alloy with fresh alloy, or refining. The refining process, when properly done, removes all of the base metals so the recovered values can be re-alloyed.

I made mention because my fear is that by the repeated heating you've reported the silver solder may have oxidized to the point where it no longer flows as it should. I've had that experience on more than one occasion. Not much you can do about it unless you can disassemble the boiler to individual components, at which time you could mechanically remove the solder. I know of no acid that will dissolve the solder without dissolving the copper from which the boiler is made.

It should be noted that silver is difficult to oxidize, but the copper contained within oxidizes readily, especially if you're using cadmium free silver solder.

It will be interesting to read how you resolve your problem, for which I offer my sympathy.

Welcome to the board.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
David Powell
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Re: Firetube Boiler Project - Leak Troubles

Post by David Powell »

Sorry to be the bearer of bad news but, probably your boiler is now beyond salvation.. Best you sell it for scrap and begin again with fresh material and the experience which you now have. I have built a few copper boilers, had great success with most and a few frustrating failures just about paralleling your adventures.
Whatever you do DO NOT sandblast your failure and then hope you will be able to silver solder it. That definitely was a total failure for me.
Regards David Powell.
jscarmozza
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Re: Firetube Boiler Project - Leak Troubles

Post by jscarmozza »

I never made a boiler, but for other things I always had better outcomes with the black flux rather than the white. I am curious to hear what you do and the results, good luck with the project.
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milwiron
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Re: Firetube Boiler Project - Leak Troubles

Post by milwiron »

Hi Blondihacks,
Welcome to the forum, good people here. I have seen some of your videos, nicely done!
I'd be tempted to try a slightly lower temp alloy like Easy-Flo 45 and black flux to fix the leaks. Yes, Easy-Flo 45 contains cadmium so use good ventilation. Black flux is usually considered for higher temp silver solders but it will work for Easy-Flo and provides better protection.
Good luck,
Denny
Last edited by milwiron on Sun Aug 08, 2021 8:09 am, edited 1 time in total.
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gwrdriver
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Re: Firetube Boiler Project - Leak Troubles

Post by gwrdriver »

Quinn,
I hate to be the co-bearer of bad news but I tend to agree with David, your boiler is probably beyond salvation. It's possible in the right hands it could be salvaged but what I suspect is in attempting the reheats, despite attempts to thoroughly clean the metal, some flux and oxide remains hidden in joints which renders them contaminated with no possibility of making them clean. These places will always repel solder. We know that silver solder, once melted, takes more heat to remelt than it did the first time so the tendency then is to add more heat (if a little is good, more is better?) , which only makes matters worse by solidifying the contaminates.

But . . . . .

What is it's present condition re weeps/leaks? Had you stopped at the 100psi/1-weep point the boiler might have been caulked from the inside and all would be well enough. If you are still only dealing with true weeps, and not a full leak, there may still be a chance for survival by caulking.

For future reference, my technique for a 4" boiler, of which I've built several, would have been to solder one end first, the end nearest to any side bushings and solder those in the process, and then pickle, assemble, and solder the other end.
Last edited by gwrdriver on Sun Aug 08, 2021 9:51 am, edited 1 time in total.
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Blondihacks
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Re: Firetube Boiler Project - Leak Troubles

Post by Blondihacks »

Thanks for the replies everyone! At this point we’re talking full leaks, not weeping, unfortunately.

My follow-up question then is, what is the correct way to fix a fire tube leak after initial assembly? I need to understand what went wrong here before attempting it again. I repaired the initial leaks by pickling, refluxing, adding a little more solder if it looked like it needed it, and reheating that joint. From the very start, each time I did that, another joint would fail. However I know people do this all the time, so there must be a correct way. Most people don’t get 52 fire tube ends perfect on their first try. I’ve read many build logs and everyone always has a few leaks, then fixes them at the end (but nobody explains how they did it)
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gwrdriver
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Re: Firetube Boiler Project - Leak Troubles

Post by gwrdriver »

I've never had that may tubes to solder in such a relatively small diameter and this doesn't help you now, but if I had such a job to do, rather than plan to touch each tube end with the solder wire, or make circlets of solder, I would consider buying (or making up) a silver solder paste, or at least many small snippets of solder, and float them in a pool of flux around the tube nest. Flux is cheap, solder, well maybe not so cheap, but cheaper than scrapping a boiler.

Normally I am NOT a fan of Kozo's technique of floating snippets of solder everywhere, for good reason, but in such a situation as this I think it would improve chances of all sound joints on the first heat which should be the objective. When you float snippets of solder in flux you are telling the solder "It's OK with me if you go wherever you want to go, or not." So if I should do that I would always stand by with the scratch tool and solder wire, just in case.
GWRdriver
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baggo
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Re: Firetube Boiler Project - Leak Troubles

Post by baggo »

Hi Quinn,

You are not alone in this 'chasing leaks' lark. I know several builders of boilers that have tried to seal leaks by silver soldering again and finished up with more leaks than when they started!

When I was watching your video on fitting the boiler tubes and end plates I was thinking 'that's an awful lot of clearance for the solder'. Personally, I would never use the recommended clearances as I think they are far too big. So long as the tubes etc. are a sliding fit into the respective hole then the solder will penetrate the joint with no problems. The thicker the solder in the joint then the more prone it will be to crack due to differential cooling. Also some solders are not very good at gap filling. I've no experience of the Harris solders though as in the UK we tend to use Johnson Matthey or Cup Alloys solders.

Have you tried wrapping the outside of the boiler with a thermal blanket to stop it cooling down so quickly after the soldering? (Wrap it around the boiler before soldering). That may help to prevent cracking of the joints due to too rapid cooling.

If you do have to start again (and I hope that you don't) consider soldering in the bushes first with a higher melting point solder. Those joints then shouldn't be affected by the subsequent heating to do the rest with your 56% solder.

There is another way to seal the leaks but ONLY if the boiler is structurally sound. That is to caulk the leaks with a high melting point soft solder such as Comsol. That melts at about 305°C so won't involve reheating the boiler to such a high temperature. It does tend to be frowned upon over here nowadays by some people (usually those that have never built a boiler) but it's a perfectly safe and valid way to fix a leak (in my opinion anyway). You do then have to be more careful about the water level in the boiler and not let it get too low.

Don't give up and good luck with it.

John
Last edited by baggo on Sun Aug 08, 2021 11:49 am, edited 1 time in total.
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Bill Shields
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Re: Firetube Boiler Project - Leak Troubles

Post by Bill Shields »

picture of leaky area(s) ?
Too many things going on to bother listing them.
Blondihacks
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Re: Firetube Boiler Project - Leak Troubles

Post by Blondihacks »

Pictures!

Here is the entire boiler, on its (final?) failed hydro test:
Image

This is what it looked like after the very first heating. To my eye, those joints mostly looked good:
Image

But there were a couple pinholes here and there, and along the road to fixing them, things got better, then started to get worse again, and then it was all downhill.

Here's an example of the problem I was having. Fixing two adjacent tubes caused fractures to appear in the joint on this one:
Image

Then fixing that joint caused cracks elsewhere, and so on. I couldn't ever get ahead of the problems.

Here is the top tube plate now, which is having all the trouble (the bottom one worked well- only one leak which I fixed).

Image

Obviously there is excess solder there. That's the result of adding too much solder as I tried to spot-fix tubes, then finally I started refluxing and reheating the entire tube sheet, which covered the whole thing with solder due to how much excess I had applied.

I think four of those tubes are leaking right now, but I actually don't remember which ones. I didn't note them this time because I suspect I'm done trying to fix them unless someone has a suggestion.

The consensus seems to be that I will have to cut this apart, salvage what I can, and start again. I've made my peace with that, but I want to know how people do go about fixing leaking tubes after that first heating so that I'm not right back here in another month. :oops:
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