High temperature expansion joint

Claim 1

An expansion joint for use in flexibly joining two adjacent spaced apart ducts through which flows gas at a temperature of 400° F. to 800° F., said joint comprising: (a) a pair of spaced apart frames adapted to be connected to the opposed faces of said ducts, with each frame having a central opening therethrough corresponding in size and shape to the internal configuration of the ducts; (b) spacer means extending outwardly from each of said frames to support the ends of a flexible boot at a distance spaced apart from the duct and the hot gases which flow therethrough; and (c) a flexible boot affixed at each end to said spacer means and spanning the space between said pair of frames, said boot comprising: (i) an innermost layer comprising an asbestos fabric coated with aluminum and silica; (ii) next outwardly from said innermost layer and adjacent thereto, a fibrous insulating batt; (iii) next outwardly from said fibrous batt and adjacent thereto, a middle layer comprising an asbestos fabric coated with aluminum; (iv) next outwardly from said middle layer and adjacent thereto, a vapor barrier comprising a heat resistant polymeric film; and (v) adjacent to said vapor barrier an outermost layer comprising an asbestos fabric coated with a fluorocarbon elastomer.