I’ve just made myself a little burnout kiln from Shinagawa
insulating fire brick. My heat source is a 15kw Sievert burner bottom
centre, firing upwards. I could do with some help with venting it. I
was thinking perhaps I need a variable vent-hole.
The kiln capacity is 7 litres (1.8 US gal). 150mm (6in) above the
burner is a kiln shelf with an inch space on two sides. A device
under the shelf splits the heat to help it flow around the shelf.
From the shelf to the kiln top it’s 135mm (5in) and near the top I
have an analogue probe. The top lid is two fire bricks, and the kiln
works well with a approx 10mm (1/2in) vent gap - just a slot -
between the bricks.
It’ll get to 650C in about 10min. About the vent, I tried with a
30mm vent hole at top centre, but it needs to be much bigger when the
burner is working on full. I worry about wasting energy once the
kiln’s up to heat and the burner’s just maintaining 650C.
The vent as I see it needs to be big enough when operating at fast
heat-up at 200kPa, and only as big to allow the burner to run
efficiently when turned down for maintaining a soak temp.
Would a vent hole be better at both these jobs than a vent slot?
Anyone have a variable vent-hole idea that’s also low-tech?
Details. The Sievert 2954 burner is mounted on a Sievert 3025
support, the one with a cast iron base and valve at the end of a long
brass pipe. It’s on a regulator at 200kPa (28 psi). This burner I
already use under a tripod with st/steel mesh to anneal sil, gold and
copper (hence this post runs on from the previous one on annealling
Cu). The mesh is useful as a means to hold the workpiece, as it
doesn’t get too hot and I can raise/lower to control the heat.
Sievert make other big burners, according to this LPG Torches
pamphlet I have, and the one I prefer is 42mm dia, 15kW, with a short
150mm flame length. The weed-killer burner they have is 50mm dia,
86kW, and a 2 foot flame.
Kiln photos are at