Steel tank thickness...

Hi again!

In my batch box rocket stove water boiler I'm about to place a water filled steel tank in the upper part of the barrel as a heat exchanger. The riser will blast the tank from below and at the impact point I will weld a 1/2" steel plate for protection. Though... are there other considerations I have to make regarding the steel wall thickness of this tank? I have lots of quite thin barrels I could use, but these have walls barely 1/25".

Thanks for any comments!
Henric

Hi Henric.

Have you watched so called "Mallorca build" by Peter van der Berg? He used steel T-bars in the ceiling of the masonry bell. They just absorb the heat and transfer it to bricks above. You can also make an experiment - fill a balloon with water and put it over a candle - it will not burst, because water is absorbing the heat. I would not use any extra plate. If it was my tank I would weld it from 1.5mm thick 316 stainless steel so there would be no corrosion inside of the tank and the water could be even used for drinking. Stainless pots with water/food are put directly over the flame and everything is fine.

Thanks Christobal!

I will use the water to heat my house, so... no drinking  ... though, using stainless steel is probably preferred from a corrosion perspective. I do have a stripped stainless steel water heater tank with enamel on the inside, and I might use this... The tank wall thickness is probably still max 1/25" but hopefully it can be kept cool from the rotating water.

I assume you will not let this be a pressure vessel?
I have a copper tank fed by coils off a flue, its about 20 gauge material and a volume of about 300L.

Thanks John!

I was planning of keeping the heat exchanger loop open for now. Excess pressure can leave the tank thtough a vertical pipe on the top of the heat exchanger tank. The heated water is normally, however, supposed to circulate out of the rocket stove and into a coil in my main tank (the one actually feeding the radiators).

I think you will need a bronze pump to circulate through the radiators.