5 minute riser failure.

So I need some new advice on the 5 minute riser.

I noticed some material obsuring my port. So took the bell off and inside I found out that the outer galvanized pipe has been exposed to to the fire and destroyed it.

I purposefully cut the metal far back to not be near the fire but it looks like that occured anyway. I then stuck it with clay slip and some cob to seal it. Looks like that has not held up

Can anyone advice me on the most current method for ensuring this does not happen before I make a new one. Are there any tricks or things to watch out for when attaching the port of the firebox to the 5 minute riser.

Hi Fraser;
Yup that metal got too hot. ​
Rather than cob and slip, on mine I used super wool strips.
I then stuffed as much more MSW as I could around the opening to help keep the gasses where they belong.

I see a couple of options you could consider.

One would be to use fire brick  to insert just  inside the riser. Sort of a slightly  extended port.
It would still need super wool  rather than cob as a final seal.

Another option would be to have the port entering a round (hex) Insulated firebrick chamber  and then simply sit an uncut 5 minute riser on top.
That could be sealed with simple cob.
If insulated bricks are available they would be the best option.

Fraser,  Here is my similar experience. Perhaps it may be of help: RMH-upgrades-repairs

So guys.

I was in a real rush to get it back up and running due to being on a Ship in winter and with a 3 month old baby.

But looking at Gerrys examples i think i came up with a similiar solution.

I used what i had at hand. I made photos but they did not save properly  so i will do my best to describe.

I decided that the pipe holding my morgens superwool was wide enough to apply two layers. It was the same as pictured earlier. Using my tin snips i removed some extra metal.
I also drilled some small holes to thread stainless steel wire to hold the wool up and ensure it does not splip down.

I noticed on other 5 minute risers i have build that that can happen. On donkeyboard someone mentioned that it is often done on Raku kilns. So i figured its worth a try.

As for the port i made shims out of leftover ceramic fibre board which have held up incredibly well in the firebox.
The shims where 2.5cm wide 2.5 thick. 2 21cm long and a top peice to make it 6cm as an inside measure. Picture stone hedge.

Then the first layer of the two mogen super wool. I traced some paper the size of the outside of the shims. Then traced this to the first layer and cut it.

I put the riser in position with the shims. Then spay painted the inside layer of the wool.
I removed it and cut this painted part out.

Placing it back it and sealing the two sides with more wool and clay.

First burn with very rockety. Gasification really obvious and lvely plumes from secondary air intake.

I do notice. Less heat from the barrel and I think that i am seeing quicker temps in the bench.
I think the position of the riser is slighly further back than before and cramping my back bypass. Leading to more heat going into the bench. It is definatly a different less intense heat from the bell.

Would the two layers of wool make such a big difference. I thought if anything the burn would be hotter and cleaner.

Im not sure.

Wish i had those photos.
Tip dont make photos with forum upload, rather make then with you camera phone and then upload from files