A new silver choice for batch box riser stubs

Hi all;
For years now the gold standard riser stub of choice has been RA330.
This material has been literally tested under heavy fire!
Matt Walker from walker stoves has been intensely burning with one for many years now with no degradation in the metal at all!
A plain carbon steel stub will last 3 months of heavy use before spalling drastically!
The cost of this high-heat alloy is astronomical. I currently sell a 6" piece for $85, my cost after bulk buying is almost $82!  
I use these in both of my batch boxes and have sold many to happy new batch box builders.
We expect this material to last the life of the entire stove or longer!

Introducing  RA253 MA!
A new choice from rolled alloy with a temperature rating of only 100F lower than RA330.
In the extreme environment at the port of a batch box during a full burn, temps are over 1800F
RA330 is rated to be used indefinitely in a 2000F environment and has lived up to its claims!
Plain carbon steel degrades quickly above 1500F it has spalled in as little as 12 weeks!
RA253 MA is rated to work indefinitely in a 1900F environment...
Will it last a lifetime?  Only many years of hard use will tell us for sure.
I predict this stub will easily outlast the purchaser in an insulated dwelling with only a few daily fires.
Will it last in an extremely hot, all-day burning RMH in an uninsulated building?
Only time will tell.
For now, I am calling RA253 MA a Silver Choice in high-end Batch box riser stubs...
Years from now it may prove to be a Gold choice equal to RA330 in longevity!
These RA253 MA riser stubs are now in stock for $60 at https://dragontechrmh.com/

Here is a link showing the effects of spalling.
https://permies.com/t/170270/High-Heat-Spalling
And another about the quick change secondary tube.
https://permies.com/t/154223/Quick-Change-secondary-air-stub

Hi all;
It's been a month now since the testing of the RA253 began.
It is installed in our 6" batch, The studio dragon.
I have seen this stub glowing orange while reloading.
I would take a picture, but the heat rolling out the open door is more than I care to expose Liz's camera to.
As you can see in the current photo the stub is still in as new condition!
Our studio Dragon is an extreme burning batch. She is burning nonstop hot, all day every day.
Way more than any "homeowner stove".
If this RA253 continues to perform at this level it may be the new "lifetime" stub, replacing the RA330 for a third less cash!
I recently sold an RA253 stub to Paul at Wheatonville.
I expect that he will install this in his new shop batch box!
I look forward to the reports on its performance.

Thomas,

Is the entire 2" diameter being used or you make some slit in the pipe to adjust the amount of air flowing?

The innovators (Matt, and Peter) experimented with putting slits in the stubs and determined that they were not helpful.
The full 2" is open, however, the secondary tubes increase in size with larger batch boxes.

Thank you for the reply. So for 160 mm CSA you would also use 2"? How high? What about the horizontal part providing the air - the same like in normal cobra design?

Yes,  a 160mm would use a 2.5x1.5 tube with a 6" tall 2" riser.
3 x1.5" is also acceptable with a 160mm.
The cobra is shorter to delay spalling issues. (EDIT) The horizontal is the same as the cobra.
By using the Ra stubs we have eliminated the spalling problem.

Thank you Thomas. Is it done for savings or regular cobra is still better? Either way I'm going to TIG weld entire cobra from RA330.

I believe Matt went with the 2" round pipe for cost & convenience.
Peter made the cobra shorter as it seemed the stubs stopped degrading around 4" of height.
A 4" cobra made with RA should be a lifetime stub.
I suggest you copy my quick-change design to remove the stub for ash cleaning.