OT: high temp epoxies

[oliver1850]

Despite my and the local welding shop's attempts to braze up cracks in my expensive German wood burning cast iron boiler, we still have some cracks due to it cooling too quickly. I'm thinking about trying to epoxy them. The cracks are inside the firebox, but probably won't see much direct flame. Water temp is usually in the 160 degree range so the casting will stay pretty cool. JB makes a high heat epoxy that's supposed to be good to a continuous temp of 400F. I'm wondering if there's an epoxy that's also a good conductor of heat, perhaps something that incorporates metal powder?

[Ken Robb]

I'm curious: what do you use the boiler for? Room heat, hot water, moonshine?

[oliver1850]

Heats the house. I also have one of the fabricated steel boilers that look like a small shed. That boiler is vented out the top, so won't work with 2nd story radiators without a heat exchanger. The German boiler is designed for a closed system. My setup runs about 10 psi.

[paredown]

All I remember is my father (who was a crack welder) talking about the difficulty of welding cast.

I bit the bullet this spring and bought a full set of new manifolds and burn tubes for my stove--I assumed repair was not possible. Are parts not available for the boiler?

I guess the trade-off is cost--if the goop is not expensive then it is worth a try?

[sokyroadie]

Despite my and the local welding shop's attempts to braze up cracks in my expensive German wood burning cast iron boiler, we still have some cracks due to it cooling too quickly. I'm thinking about trying to epoxy them. The cracks are inside the firebox, but probably won't see much direct flame. Water temp is usually in the 160 degree range so the casting will stay pretty cool. JB makes a high heat epoxy that's supposed to be good to a continuous temp of 400F. I'm wondering if there's an epoxy that's also a good conductor of heat, perhaps something that incorporates metal powder?

Their stuff is fantastic, but you will pay dearly. We have used it to build up compressor heads, pumps etc - the super metal is what we use.

http://www.belzona.com/en/products/purpose/metal-repair.aspx

Jeff

[oliver1850]

All I remember is my father (who was a crack welder) talking about the difficulty of welding cast.

I bit the bullet this spring and bought a full set of new manifolds and burn tubes for my stove--I assumed repair was not possible. Are parts not available for the boiler?

I guess the trade-off is cost--if the goop is not expensive then it is worth a try?

I have not been able to find a dealer to even get a price on a boiler section. Not sure the current boiler (mine is over 30 years old) part is compatible.

But yes, I'm guessing one boiler section would be $1000 or more. Worth a shot at nursing it through another year or two.

[ultraman6970]

Probably u read this already...

http://www.lincolnelectric.com/en-us/support/welding-how-to/Pages/welding-cast-iron-detail.aspx


https://www.youtube.com/watch?v=Pq0wfU4ZaKk

https://www.youtube.com/watch?v=Yopcz-IYDyQ

[oliver1850]

Their stuff is fantastic, but you will pay dearly. We have used it to build up compressor heads, pumps etc - the super metal is what we use.

http://www.belzona.com/en/products/purpose/metal-repair.aspx

Jeff

Thanks Jeff. That sounds like what I had in mind, but the 1511 high temp isn't rated for higher temps than the JB high heat. I didn't see anything about conductivity on either product's site, though the Belzona does mention that steel is incorporated in the compound.

Do you know anything about Permatex 84333? Seems to be a high heat compound that has titanium. It's listed by many vendors as a stick, and appears to be packaged in a single container. Always leaves me frustrated when vendors use the same low resolution stock photos of the package with unreadable description and instructions. Permatex site was no more informative. These companies need some competent folks in their marketing departments...

[oliver1850]

Probably u read this already...

http://www.lincolnelectric.com/en-us/support/welding-how-to/Pages/welding-cast-iron-detail.aspx


https://www.youtube.com/watch?v=Pq0wfU4ZaKk

https://www.youtube.com/watch?v=Yopcz-IYDyQ

Problem with cast is getting it up to temp and cooling it down gradually after brazing so that it doesn't crack. Don't know anyone that has an oven big enough for the boiler section. I tried keeping it warm with the torch as it cooled but it's hard to judge temp and it cracked every time. Welding shop had similar results.

[Tandem Rider]

CH Mcguinness is a company in the Quad cities, they have a guy who can weld, not braze it if anyone can. Brazing will not hold on a boiler. They have an R stamp, this is required for legal and insurance reasons to weld on a pressure vessel. I'm hoping they can still weld it after attempts at brazing.

[pbarry]

Your inclination to use a chemical bonding process is the right one. The metal is extremely brittle at this point and any further attempt at a welding or brazing solution will probably fail. You might look into fabricating new panels as another option. Thick plate would last a few years or more.