Boilers

Any views on stainless steel boilers. Has been suggested by a fried, a coded welder, for a 5 in Shay? Was going to go down the copper route but this an attractive alternative as the intention was to leave the model bright metal.

The first boiler I made, for a 5" Terrier was in aerospace certified 316 Stainless Steel and was welded by an aerospace certified welder.

It could not be accepted as there was no class for it, ( I'm going back many years). So I learn't my lesson and consulted the club boiler inspector before building another but things may be different now.

Brian

You certainly won't be able to have it tested by a club inspector as the scheme only covers copper and steel. Speak with a professional boiler inspector and insurance company to see what the costs will be for design approval, initial and yearly testing and insurance.

I made one (Aerospace quality 316 ss in 1965 ) for a 5" Firefly, but never proceeded to insurance test stage as by then it was discovered that over a period of time (apparently) you would possibly experience 'brittle fracture' along the waterline between water and steam. I believe that Australia has a different 'take' on the subject. it was a bit of a sweat belting hell out of the backhead to form the 1/2" flange, firebox also but I did it with jab rock formers and a club hammer, cold. I did pressure test cold to 200psi and all was Ok. tube Joints were silver soldered, the backhead , barrel etc were argon welded by a coded welder.
BobH

Austenitic stainless and (very) hot water are not a good combination, you can get pitting and stress corrosion cracking. I think there are grades of SS that would be OK but whether you can get them in small quantities/thin sheets is anyone's guess. As others have said, you're not likely to get a ticket from a club inspector, and to do it via an insurance comany as a one off would cost as much as a copper boiler. In any case, you want some cladding to keep the heat in, so make that out of SS and no-one will know.

Hi John,

As mentioned by Bob other countries (Australia) may accept stainless steel boilers. This one is in "Duplex" steel, not 316.

Thor

Plenty of stainless ones across Europe.

Here are a few recipes

en.wikipedia.org/wiki/Materials_for_ressure_vessels

I don't think the OP was considering a nuclear fired boiler.

Hi all, what’s the feeling about having a brazed joint on the boiler barrel. The joint is a butt joint and it’s also rivetted.

Copper boiler? Silver soldering = brazing with silver alloy, that's normal.

Russell