clothing and face protection can guard against the effects of radiated heat when the
furnace is open.
When the product is opened during operation there is considerable radiated heat. Do
not keep any flammable objects near the product, nor objects which could be damaged
by radiated heat.
6.3
Opening the Door
Take great care when loading or unloading the furnace chamber. See
section 6.2. Before removing a hot object from the furnace, ensure a
suitable surface is available on which to put it.
Do not open the door at high temperatures. If possible, do not open it above 200 °C. If
it is necessary to load or unload work at elevated temperatures, keep the door open for
as short a period as possible. The insulation cools quickly and may crack through
thermal shock.
The heating elements and the insulation are very susceptible to mechanical shock. At all
times operate the door gently to avoid mechanical shock.
6.4
Insulation Cracking
In these furnaces the insulation material is susceptible to surface cracking as a result of
high temperature cycling; this is a normal occurrence and such cracking is not
detrimental to the performance of the furnace.
6.5
Atmospheres & Corrosive Materials
In oxidising atmospheres, metal oxides react with the silica layer on the surface of the
elements and may lead to premature failure. Protect the elements from splashes of
molten metal and dust when loading the furnace and from fumes developed when
melting, especially from fluxes. Also avoid compounds with a high alkali content.
The furnace is designed for use up to its maximum temperature in oxidising
atmospheres, but can be operated successfully in neutral or carburising atmospheres. It
may be used with nitrogen, argon or helium atmospheres to 1600 °C. Reducing
atmospheres are not recommended. Sulphur dioxide is not harmful in low
concentrations. However chlorine and fluorine attacks oxidised elements and should be
avoided. A harmful gas is produced and collects in poorly ventilated spaces.
The furnace is not recommended for burning off carbonaceous materials. Other
Carbolite Gero furnaces are available for this application.
When an optional gas inlet is fitted there is a label near the inlet saying "INERT GAS
ONLY".
The chamber is not gas tight, the gas usage may be high and the chamber is always
likely to contain some air. Residual oxygen of approximately 1% to 2% is to be
expected.
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6.0 Operation
