I replaced the original secondary air tube in our greenhouse batchbox late last season, it had spalled down to unusable condition.
At that time I installed the original prototype Dragontech quick change secondary supply tube in its place.
Yesterday in 15 minutes I replaced the carbon steel riser stub with a new one!
Simply twist and lift the old degraded stub out and drop in a new one!
15 minutes included cleaning all the ash from the firebox .
With my Dragontech design door I was able to simply slide the secondary tube back 6-8" .
This facilitated removing the ash build up in the slotted port entering the riser.
With all the ash removed the air tube slid right back into place without ever removing the door!
Unfortunately I made this repair early in the morning and did not take the time to document the process.
It really couldn't have been any faster or easier!
We burn that rocket hot , nonstop all day everyday from September- April or beyond.
I expect to change the riser stub again before the end of burning season.
At $5 or so for a replacement stub I can do this as many times as needed.
Or for $80 or so I could use a RA330 stub from Dragontech and never need to replace it again!