Furnace insulation

Figure 6 27. Automated DTA apparatus of Wendlandt and Bradicy (wy -.atuple-holder plate B. furnace. C. furnace platform assembly D. -amplecapiltm tube K. furnace insulation F. cooling fan.

Refractories are materials capable of withstanding high temperatures and not degrading in a furnace environment when in contact with corrosive liquids and gases. Refractory insulators are used in high-temperature applications to reduce heat losses and to save fuel. Table 9.5 lists some of the important furnace insulation materials together with their maximum usable temperature and thermal con-... 

Table 9.6 lists some of the important crucible materials. Crucibles and other furnace equipment such as boats and setter plates must meet the same requirements as refractory materials used for furnace insulation, i.e., they must be able to withstand high temperatures and also contact with any corrosive liquids or gases used. Items such as crucibles and boats should also possess good thermal... 

Carbon monoxide (CO) is a deadly gas that can form from a reaction between trapped moisture (for example, in the furnace insulation) and carbon. The source of carbon may be the graphite used in some furnaces for heating elements or in graphite-felt insulation. Problems can be avoided by ensuring that the furnace is kept dry. Domestic CO alarms can be installed in the laboratory area as an added precaution. 

The silica-based fibres are typified by Quartzel (Saint-Gobain, France), which while having slightly inferior fire and heat performance to alumina-based fibres (see Table 8.5), are available as continuous filament yams, rovings, and chopped strands (each comprising 9 or 14 pm diameter filaments) and sewing threads, filament-based nonwovens, and wetlaid papers. Continuous filament yams may be knitted and woven to yield fabrics with applications in furnace insulation, combustion chamber insulation in aircraft, ablative composites for military and other markets, and hot corrosive gas and liquid filtration. 

Figure 10.11 Construction of furnace insulation from rigid board insulation material. Source Reprinted from Technical literature of Fiber Material Inc., Biddeford, Maine, USA.

The material must not be used in the presence of air above 200° C. These products are particularly useful for vacuum furnace insulation [70] and can be used in vacuum or in the presence of an inert gas up to 2750°C. 

Bielefeldt I, A space age material for vacuum furnace insulation, Heat Treating Magazine. 

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