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!
I installed that "new secondary air stub" on November 12th 2021.
As of today, Feb 25th 2022 it's shot,
My photo show's its current condition.
This batchbox sees severe use. It runs non stop apx 12hrs a day all winter.
3.5 months is a reasonable time to expect a piece of plain steel to last at those temperatures.
With my quick change secondary tube.
It will take just a minute to change that worn out part with a new replacement.
A standard 6" long piece of 2" schedule 40 pipe is around $5
I have decided to replace it with a stub of high heat RA330 at $80 .
Time will tell, but I expect this to be the last stub I ever need.
I will update photo's at the end of burning season this year and again Mid burn season next year.