KILNS & FURNACES
Electric in air to 1800°C • Research • Heat treatment
Controlled atmosphere • Melting • Gas, Natural/LPG to 2300°C
Tetlow Kiln Pty. Ltd. ABN: 26 166 832 300 54 Howleys Road, Notting Hill, 3168 Victoria Australia
T: +61 3 8545 8296 F: +61 3 9544 2723 E: info@tetlow.com.au www.tetlow.com.au
11.3 FIRST FIRING OF ELEMENTS
It is recommended that the first firing of a new kiln’s elements is a slow firing, with the kiln
empty, to a temperature of 1050°C. The cycle is outlined below, and is also referred to as a
pre-oxidisation or re-oxidisation cycle.
Do not fit ceramic close off bungs to vent holes during dry out firing.
You should heat up to 1050°C with a ramp up time of seven (7) hours, (roughly 150°C per
hour)
Hold at 1050°C for four (4) hours
Turn off the elements and allow to cool with the door closed until the furnace is below
200°C
The elements will now be oxidized and ready for use, and added benefit is this will enable
the cement to mature/dry and to remove moisture from the brickwork.
11.4 SPECIAL NOTE IF THE KILN IS TO HAVE A REDUCTION ATMOSPHERE
The durability of electric elements in air at high temperature is greatly increased by an oxide
surface layer formed by a reaction with oxygen from the air, as noted above in the section
“first firing”. The protective nature of this oxide layer is proportional to its area and depth.
Foreign matter usually interferes with the formation of the oxide layer, and this causes a
reduced life. At high temperatures the protective layer of element materials consists almost
entirely of aluminium oxide. This has a light grey colour and good chemical resistance. At
temperatures below 1000°C (1832°F) the oxide layer has a dark colour since the aluminium
oxide is impure.
If exposed to gases with a low oxygen content (including during Reduction Firing) the oxide
layer may be attacked by reducing gases including nitrogen. The kiln may be used in low
oxygen atmosphere (including Reduction Firing) provided you have first performed a pre-
oxidisation cycle as noted above. It is also necessary to perform a re-oxidisation cycle
periodically (frequency will depend on your particular application).
SECTION 12 - KILN ACCESSORIES AND INSTRUMENTATION
12.1 ENERGY REGULATOR
This is purely a device which controls the rate of temperature increase through control of
the heat input to the kiln. It comprises a timed switching device, with the time of activation
being variable from 0 to 100% of the time.
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