We made secondary combustion stoves, not just catalytic models. Tubes and baffles are parts sold by every single manufacturer. Some are warranted to a greater degree than others. To assume these parts are not prone to ever fail, well that's not accurate. I can appreciate catalytic combustors can fail as well. But I'll clarify "fail". It's different than having a depreciation of ability to burn exactly the same as day 1.
Failure was rampant beginning way back in 1984. Oregon passed emissions regulations and hundreds of manufacturers placed cats into stoves. The vast majority used one of two ceramic substrates. If you look at these substrates with an electron microscope before washcoat and precious metals are applied, they look rather smooth. Once the washcoat and precious metals are applied, they take on the appearance of an English muffin. This adds tremendous surface area and creates turbulence.
When repeatedly subjected to temperatures in excess of 1600F, a conversion of alpha alumina to gamma alumina takes place and the English muffin appearance flattens out loosing tremendous surface area. It usually won't be long before the combustor begins thermal degradation. Lest you feel the metal substrates are "better", the same loss of surface area still happens and rather than fracture, they become less effective and can start to plug. This is the truest meaning of "fail".
Now, most secondary combustion stoves are build robustly. I have a friend that made one of the highest regarded wood stoves on the market. Due to emissions regulations requiring fewer and fewer P.M. concentrations, the minimum allowable air setting have been increased, meaning you can't cover as much of the hole as you could previously. I and others watched in person what happened to that incredible stove when temps dropped below -20F. It began to glow...flue collar and areas of the top. The owner of the stove company was stunned.
Stack effect, the difference between inside and outside temperatures, increases as that difference increases. Mind you this is precisely what caused so many cat stoves to fail and even a few, less robust design secondary combustion stoves to "fail".
I can appreciate that every stove made today is cleaner burning, more efficient and better designed than ever before. And what must happen is design and engineering need to keep up with the influences or impacts wood heaters are subjected by ever changing regulations.
Thank you
BKVP
