Pottery in Australia Vol 17 No 1 Autumn 1978

efractory fire-brick structure of the same size. On this basis it would not take
many firings to pay for the higher cost of the ceramic fibre with savings in fuel.
As the kiln design evolved, a new approach was found to several previously
accepted methods of kiln construction. The first of these changes was achieved
with the kiln frame. In conventional construction techniques in which refractory
bricks are used the supporting framework and outer cladding is generally formed
from heavy steel structural elements. This method of construction, however,
becomes redundant when light-weight fibre insulation is utilized. Instead lightgauge
metal panels can be used.
A reinforced hollow panel fabricated from sheet metal was developed for this
purpose. Ribs were incorporated in the panel for stiffening purposes. By modifying
the panels, channels could be created through which cooling air would be
circulated when the kiln was in operation. The circulated air, which is preheated
by this operation, could then be directed to the burners as the main air supply for
combustion.
This would have a three-fold advantage. Firstly, by raising the temperature
of the incoming combustion air the efficiency of combustion would increase,
thereby reducing the fuel usage. Secondly, raising the starting temperature of the
incoming air would enable a higher ceiling temperature to be attained and permit
the use of simple burners. Thirdly, by providing a moving air stream over the kiln
outer surfaces, less insulation could be used without risk of overheating.
The anchoring pins used for supporting the fibre insulation are generally in
the form of threaded stainless steel rods. Most fibre-kiln manufacturers fix the
rods to the steel backing plate by spot welding, but a number of failures have
.. resulted from this technique. A more reliable fixing method was therefore sought
; for this kiln design. The result is that rods pass through the panels and are fixed
on either side with nuts. A nut-shaped recess was punched into the outer face of
the panels to prevent the outer nuts from protruding, and a spacing tube inserted
over each rod within the duct cavity. The rods therefore pass through two layers
of the panelling, 25 mm apart, and when clamped up they are completely rigid
and incapable of being tom out. The outer surface is covered with a metal sheet,
hiding. the recessed nuts from view and providing further strength and rigidity.
Figure 1 shows the technique which was used.
The stainless steel rods which are fitted to the panels are used to support
flanged refractory tubes which in turn clamp the fibre in place. Because of the
permeable nature of ceramic fibre, kiln gases can penetrate and condense on the
surface of the metal supporting panel. The condensate is generally acidic and as a
result corrosion can quickly set in. The inside faces of the supporting panels were
therefore coated with a heat- and acid-resistant polyester acrylic before the fibre
lining was installed.
The panels bolt together to form the four sides and top of the kiln and are
designed to sit on a rigid hearth containing the burners and flue. The panels are
extremely light in weight, each complete side of the kiln weighing only 29 kg. This
feature then led to another break from conventional kiln design. The light-weight
panels have eliminated the need for a heavy hinged-door, or the primitive wicket
door which has to be built up and dismantled with each firing. Instead the whole
side of the kiln can be lifted aside by one person. This means that access can be
made through the front, side, back or top of the kiln, or through two sides if
necessary. The kiln can even be used as a top hat structure by lifting the whole of
the fibre insulated top section aside, by using a simple hoist. This enables the
advantages of a top hat kiln to be achieved at a fraction of the usual cost.
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