Insulated exhaust pipe and manufacture thereof

Abstract

An insulated exhaust pipe comprising inner and outer spaced corrugated metallic tubes separated by refractory fiber isulation. Strips of higher density refractory fiber insulation hold the low density insulation in place during operation and prevent degradation of the fiber by vibration. The pipe is made by rolling the inner tube over a layer of insulation, including strips, to which adhesive has been applied. The insulated tube is then inserted into the outer tube, rotating the insulated tube so that the corrugations of the outer tube do not damage the insulation. Specific structure for carrying out these method steps is disclosed.