Patent ID: 8693853

Claim:
A radiant tube assembly ( 12 ), comprising: at least one tubular structure ( 14 , 16 , 22 , or 24 ), each tubular structure ( 14 , 16 , 22 , or 24 ) having a length and an external surface ( 15 ) exposed along the length thereof, and a thermal protective layer ( 18 ) disposed upon at least one external surface ( 15 ) thereof, wherein the thermal protective layer ( 18 ) has a. from about 5% to about 40% of an inorganic adhesive, from about 45% to about 92% of a filler, and from about 1% to about 20% of one or more emissivity agents; or b. from about 5% to about 60% of colloidal silica, colloidal alumina, or combinations thereof; from about 23% to about 79% of a filler; and from about 1% to about 20% of one or more emissivity agents.