parts and melting points..

[mark grossman]

i am building a cob house with rocket stove in southern mexico. parts here are tough to get for free. ducting/metal tubes are not in supply, no one uses them. so i found a place that sells 10" galvanized steel with a melting point of 785 F. this would be the tubing to exit the stove into the bench. ianto says the temperature will be in that area up to 700F. but i do not want to risk melting. or am i over reacting? i could have a local welder make me a tube for the start, maybe like the first 6 feet, out of plain steel, with a much higher melting point. any thoughts or ideas? mark

[Donkey]

Hello Mark, and welcome.

I would be wary of using galvanized too close to the high heat portions of the stove..
Temps CAN get higher than those youve stated above.
Either way, when it comes to the health of yourself and your family/friends, it probably pays to over-react somewhat.

Youve got the right idea.. Start the galvie a few feet on and use something else for the high temp bits.. You could perhaps build tunnels out of brick or just make a cardboard form and build over it with high sand content cob.

Course, there is a possible risk there, Ianto and others have pointed out that the porous nature of cob could allow Carbon Monoxide to seep through. Its my feeling that it shouldnt pose a problem. For most of the burn cycle of a well built rocket stove it should be burning the CO off, and the rest of the time the chimney (whatever, etc) is keeping flow going, gasses present should be taking the path of least resistance. That is, outside.
Still, no one has answered this question as of yet. Seems like an important one.

[markgrossman]

just wanted to correct my silly mind fart, i can get 8", i did not mean 10" galvanized pipe.

[ernie]

or you can chuck the galv into a pit fire and just burn the coating off.