Promat high temperature insulation - Properties and application information

Ceramic fibre materials and standard refractory materials differ regarding specific properties: less construction mass enabling low heat storage capacity, almost unlimited thermal shock resistance and resistance to most acids with the exception of hydrofluoric acid, phosphoric acid and strong alkalis. Despite good chemical resistance there will be acid formation in linings which are subjected to atmospheres with increased sulphur or vanadium pentoxide contents when temperatures fall below the dew point. The acid will destroy the metallic furnace casing. In such cases a vapour barrier made of metal must be installed in the insulation layer.
This must be located thermally above the dew point of the furnace gases. No effect is noticed if wetting the fibres with oil or water.
However, the thermal conductivity of the lining increases upon condensation of water.

Short circuits may occur in electrically heated furnaces as a result of condensed water. The thermal and physical properties are fully recovered after drying. The specific electric resistance of fibre boards can reach values between109 and 1013 ? cm depending on the board grade.
Due to hydrogen the silicic acid contents of ceramic fibre materials will be reduced. The proportion of H2 in the atmosphere is not decisive, however the existence of H2 is important. The concentration of silicic acid and H2 as well as the temperature (above 700 °C) determine the reaction speed. Hydrocarbons and C0 also have a reducing effect on the fibres.
The thermal conductivity of fibre products can multiply upon impregnation of the pore space with hydrogen, carbon dioxide, hydrocarbons and water.
The huge open pore space of fibre products of mostly more than 90 % by volume effects susceptibility toreactions with dusts and vapours containing alkalis, alkaline earths, phosphate, boric acid, lead, zinc, fluorine. Thus fibre products are protected against glaze vapours with protective coatings. A further reason to protect the surface is the necessity to prevent crystallised fibre parts from separating.
Fibre products are also sensitive to methane. Consequently, if the furnace with fibre is heated with gas, special attention must be given to the burner regulation and to the tightness of the gas lines. For electrically heated furnaces a nickel-free heat conductor must be ensured in the case of direct contact between fibre and heat conductor. The fibrous structure imposes natural limits on mechanical loads. Standard values for permissible gas velocities are indicated in graph 6.
RCF have been classified as a category 2 carcinogen under EU directive 67/548/EC . Therefore avoid exposure and obtain special instruction before use. Material Safety Data Sheets are available on request .