GB1264022A - Refractory heat insulating materials - Google Patents

Abstract

1,264,022. Thermal insulation. FOSECO INTERNATIONAL Ltd. 6 Oct., 1970 [6 Oct., 1969; 2 July, 1970], Nos. 49044/69 and 32217/70. Heading F2X. A refractory heat insulating material, suitable for the protection of turbine engine casings, is formed of a dry composition comprising inorganic refractory fibre and a water soluble inorganic binding agent, the composition being of a form of which the hardness, strength and density do not vary across the bulk material. Usually, though not necessarily, such a composition will be one in which the binding agent is homogeneously distributed. Preferably a wet or damp mixture of the ingredients is first formed and then dried by means of a drying method which does not cause migration of any of the components of the composition. Dielectric heating, infra-red heating or, preferably, microwave drying may be employed. The inorganic fibre is one or more of aluminosilicate, calcium silicate, asbestos, alumina, silica, zirconia and carbon fibres. The binding agent is silica sol, alumina sol, sodium silicate, potassium silicate, ethyl silicate or a metallic phosphate or borate. The composition may also include up to 10% by wt. of finely divided refractory material, e.g. alumina, silica, calcined rice husks, diatomite, kieselguhr, magnesia, silicon carbide, silicon nitride or fireclay. The insulating material may be faced or backed with a heat reflective layer such as aluminium foil, and it may if desired be faced with a refractory dressing. When used for lining turbine, aero engine or exhaust casings, the material may be secured in place by any convenient method such as adhesion, bolting or riveting, or by two or more such methods. A composite insulating material may be formed of two layers each of material according to the invention but of different densities. The lower density layer can even be honeycombed if desired. When used for lining a turbine or aero engine casing the lower density layer is preferably adjacent the casing. In a particular example, a preformed web of silica sol bonded aluminium silicate fibre, of thickness 25 mm., was adhered to the inside of a gas turbine casing with a sodium silicate based adhesive and riveted in place at the edges.