Reid Harvey on sun 10 dec 00
Dear Clayart Friends,
Every couple of years I build a kiln, but I am not an expert, especially
when it comes to gas connections, air to gas and correct port and flue
sizes. In other words, 'I NEED HELP!' To top it we are attempting to
work with materials on hand, to build a temporary kiln, interior of only
18 inches cubed. This will be a short term, prototype kiln for
production of earthenware water purifiers, urgently needed by the poor
of Bangladesh. I would be grateful if someone could give some insights
on the correct use of a venturi burner, purchased in the U.S.
The burner is a Buzzer, VNB 150, perhaps 16 to 18 inches overall length,
but with nozzle diameter 2 3/8 inch. From our first attempts I am
concluding that in addition to improper gas pressure the secondary area
was excessive, so we may need to rig up some kind of a register, to make
this adjustable. And I believe the gas line needs to be a full 1/2 inch,
whereas we've been using a bit smaller, in my perhaps mistaken
assumption that we could get away with this, the burner capacity greater
than a kiln of this volume would indicate.
We are using one wall thickness of local, Bangladeshi firebrick of good
quality, backed with an insulation of applied mud, about an inch thick.
(Our kiln is on the roof of our workshop, in a downtown location of
Dhaka, the prinicpal city here.) I would prefer a cross draft
arrangement, but where temporary it has seemed a lot more convenient to
make it updraft, with the thought that we can tolerate a bit of uneven
heating. But in our two firings to present we have not even reached a
dull red.
We are using high pressure regulators on each of the two gas cylinders
connected, and in addition a second regulator, to the specs provided by
the burner manufacturer. Having two regulators between bottle and burner
has seemed a bit odd to me, but appears acceptable to my, perhaps
uniformed thinking. I would imagine it better to skip the two local
regulators, using only the one that is to specs. I do know that we also
need to pay attention to the p.s.i. reading, the gauge indicating
between 1.0 and 15.0, but cannot locate any reference to the best p.s.i.
amount, given our combination of variables.
Our first task has been locating all of the various fittings, and now we
are familiar with some of the vendors. But if we could work with the
materials we have, and not start from scratch with Bangladeshi burners
it would save us a bit of time and effort. Any insights from friends on
the list would be greatly appreciated.
Kind regards to all,
Reid Harvey
Ceramiques d'Afrique, now relocated to South Asia
http:/www.geocities.com/ceramafrique/
P.S. More on the earthenware purifiers a bit later. First adaptation to
Bangladeshi clay materials has been very promising, and we believe we
can make a water purifier that is affordable to the poorest of
Bangladeshi poor.
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