a General question for ALL rocket mass heaters

[joshua4511111]

I'm in the process of buying a home with the intent of putting in a rocket mass heater. I realize that RMH have no long term history in that they are relatively "NEW" for a good heating system. My question has to do with the longevity of the barrel above the heat riser. Being that it is relatively 'thin' metal'... How long can I reasonably expect the 30 or 55 gal drum to last? Assuming I would be routinely using the RMH consistently of 3-5 times a week and the fact that an efficient burn tube throws out temp. about 1000 degrees F...How long can I expect the top to last before having to replace the barrel???? Again, I am assuming 'regular and routine" use... would not the top bar (for instant heat" 'burn out' or be unusable after a period of time??? Would I not have to replace the barrel after 1-2 years? Does it not get that hot to 'burn off/out the metal of the barrel? Thanks in advance for any helpful information.
bob

[pa_friendly_guy]

The barrel burning out in time is a normal part of the unit. It should last more than the 2 years you mentioned, but it will eventually burn out. I have hear about welding a sacrificial steel plate to the inside of the lid to extend the life of the barrel. I liked the idea. A 1/4 inch steel plate should take the heat and extend the barrels life for some years.

[matt walker]

You can expect it last quite a while, perhaps even decades. In order to burn away the steel, you need both heat and oxygen. Those two rarely exist in that location at the same time. Secondly, in most builds, replacing the barrel takes very little time or effort. In my opinion, it is not a part of the build to worry too much about.

[joshua4511111]

Thanks for the reply. Matt, I hope you are correct about the barrel lasting andthe build. I just don't want to wake up one morning with a house full of smoke or worst yet, on fire.

[joshua4511111]

Along the same lines as my previous question. It seems that the recommendations for the heat riser is to use 'a tube within a tube (like a 6' pipe in a 10-12 inch vent pipe that is insulated with vermiculite). I have read that with the intense heat generated in the combustion chamber and heat riser, that the inner most pipe would eventually fail or burn away (its very thin galvanized aluminum). Assuming that is true about the burning away, would the heat riser (make as described (mixing vermiculate with refractory cement) also not be distorted/ destroyed (mandating a rebuild of the riser ????? ? Or is this too, NOT something to be concerned about???

[matt walker]

With regards to the barrel, if it does fail it will do so slowly, with pinhole leaks as though it was rusting out. You would know it was compromised long before a dangerous situation developed.

The internal riser sleeve absolutely will burn away if the stove is running correctly, no matter how thick the metal used is. That is the reason for the insulative fill to be structurally sound on it's own. Thus the refractory cement or the like. My home system is just fire clay and perlite and its fine after continual use for two winters.