Re: Stainless steel boiler/exchanger?
Posted: Fri Apr 12, 2019 11:55 pm
I've found that moving fast and stuffing rod is the key to TIG welding SS, as it keeps heat down. If your bead starts turning brown its too hot, I shoot for a silver/gold color with a little blue being the "warning". For something like this I would probably tack the tube sheets in, then cap the tube holes with cover plates and some threaded rod and purge the inside while seal welding the tube sheet to the shell. Then I think I'd countersink the holes about 1/3rd of the way through the tube sheet and silver solder them in.
The picture of the SS boiler looks well done, it appears the shell was TIG welded to the tube sheets and the tubes themselves were silver soldered?
My background is based in industrial fabrication, and one of the recent projects we bid was a large cooling exchanger about 30' long, basically a pipe bundle submerged in a big open top steel tub. The bundle had been replaced several times and they had tried stainless and it cracked, but it was also in a bare steel tank with chlorinated city water just dumped into it. We didn't make the SS bundle so I have no idea if it was assembled correctly, purged, passivated, etc.
Another wrench to throw into the works is SIB tig rod, I've used this on some work recently and been pleased with the way it welds at a lower temperature than stainless and steel melt. Because this will be a 10" pipe boiler I'll have some space to work and likely use 1/2" to 3/4" tubing with .065" wall, so I'll have a bit more meat to work with in the weld department.
The picture of the SS boiler looks well done, it appears the shell was TIG welded to the tube sheets and the tubes themselves were silver soldered?
My background is based in industrial fabrication, and one of the recent projects we bid was a large cooling exchanger about 30' long, basically a pipe bundle submerged in a big open top steel tub. The bundle had been replaced several times and they had tried stainless and it cracked, but it was also in a bare steel tank with chlorinated city water just dumped into it. We didn't make the SS bundle so I have no idea if it was assembled correctly, purged, passivated, etc.
Another wrench to throw into the works is SIB tig rod, I've used this on some work recently and been pleased with the way it welds at a lower temperature than stainless and steel melt. Because this will be a 10" pipe boiler I'll have some space to work and likely use 1/2" to 3/4" tubing with .065" wall, so I'll have a bit more meat to work with in the weld department.