New blast door.

[brickie in oz]

I made a new blast door for the oven today, all cut with a plasma cutter.

[chidding]

Re: New blast door.

Nice man, looks badass

Can someone explain to me how the more i block off the door of my pizza oven, the harder my fire roars, I understand it creates some sort of vacuum, but it blows my mind, i could watch it for hours haha.

[brickie in oz]

Re: New blast door.

My oven roars like a train with the blast door on it, same, I could watch it for ages.
I even had it huffing like a train some time ago too with the blast door on.

[Johnny the oven man]

Re: New blast door.

I made a new blast door for the oven today, all cut with a plasma cutter.

You have way too much time on your hands brickie...............

[Lburou]

Re: New blast door.

Is that a self portrait Allen?

[shuboyje]

Re: New blast door.

I personally feel the blast door works by decreasing the turbulence in the oven opening thus increasing airflow.

[brickie in oz]

Re: New blast door.

Isnt it just a restriction like a venturi?
Reduces flow but increase velocity or something like that?

Who cares, it works a treat.

[chidding]

Re: New blast door.

Question:

I have a double skin stainless flue which is insulated. i thought it would be cold on the outside but with my latest fires (still curing) but getting really big fires.. its getting almost untouchable.

I have been having a blast door on the entire time.. with really maybe 2 inches air at the bottom...

Soo.. would this cause the air going up the flue to be hotter because it has less cool air flowing up the chimney? If so, ill just avoid the blast door once the fire gets roaring.

Or am i going to have to live with a hot chimney?

just worried about rendering up against it.. and it passing through a rubber boot.

[brickie in oz]

Re: New blast door.

Does the double skin have vents cut in top and bottom, the ones Ive seen installed in houses usually do?
This must create an airflow that helps keep the outer skin cool, without it I would imagine the heat just transferring from the inner skin to the outer via the air gap?

Those silicon boots are good to about 500c from memory.

[chidding]

Re: New blast door.

Nah it's got ceramic fibre insulation between it. 1inch of it. Barely an air gap.
Silicone boot is a black dektite so unsure of
Temp.

Is my theory possibly right?

[brickie in oz]

Re: New blast door.

With 1" of CF the outer wouldnt even get warm, I made a gas forge out of an old SSteel beer keg and used 1" CF, you could "almost" put your hand on the keg outer when the inside is 1200c.

Maybe the CF is damp and transferring the heat?

[chidding]

Re: New blast door.

With 1" of CF the outer wouldnt even get warm, I made a gas forge out of an old SSteel beer keg and used 1" CF, you could "almost" put your hand on the keg outer when the inside is 1200c.

Maybe the CF is damp and transferring the heat?

could be possble, was fairly dry when i was using it.. and after a week of fires should definately have evaporated by now.. but ill test my theory of no blast door with a huge fire and see how i go.

Appreciate the help.

[GianniFocaccia]

Re: New blast door.

Isnt it just a restriction like a venturi? Reduces flow but increase velocity or something like that?

My guess is that a blast door operates much like the dampers on either end of a wood smoker, restricting air in by the firebox, and limiting smoke out at the top of the smoke stack. This allows the user to 'tune' the smoker, more to control temperature, but in the process, control the rate of the burn and thus fuel usage.

I would think that with several well-placed (adjustable) vents, a blast door could accomplish the same thing, and since firebrick will absorb heat only so fast, maybe a controlled oven burn would be a more efficient and gentler method of firing the oven.

Based on you guys' experience in adjusting your doors to get maximum venturi effect, is there an optimum vent size that you would recommend? It appears that maybe an adjustable vertical slot (like Al's) could work as well. And yes, I know it wouldn't take me long to learn how to stare at a fired tuned by a blast door!
John

[chidding]

Re: New blast door.

Vent size is really dependent on entry size and done size. Easiest way to determine the best size is make a decent fire. Then grab some mdf or any flat wood and cover half the door. Give it ten seconds and keep lowering an inch or so till it looks like the air flow is blowing out the fire rather than accelerating. Similar to starting a fire with only coal left, you need to blow quite hard... But not so hard you blow the fire
Out

[mrchipster]

Re: New blast door.

This sounds like fun. Optimal Blast door design for cool looking fire.

Design criteria

1) Door must be at least partially made of glass or have significant viewing area (so you can see the fire). Otherwise what is the point.

2) Vent(s) must be able to be moved to various locations so as to optimize venting based on fire criteria.
a) fire size
b) fire location in oven
c) retained heat of oven (new or old fire)
d) size of oven
e) size of inner arch

3) Positions must be able to be recorded or marked so repeatable chugging/huffing or blast furnace flames can be achieved.

4) Camera must be able to be used with the door to record the event(s).

Any other design criteria is welcome.

Chip