Straight Radiant Tube for Industrial Furnaces Custom Flange-Mounted Radiant Tubes | OEM Manufacturing | FH® Alloy FH® Alloy manufactures straight radiant tubes for industrial furnaces and heat treatment equipment, providing custom solutions for indirect heating systems used in a wide range of thermal processing applications. Straight radiant tubes are widely used in furnace systems that require stable heat transfer, controlled furnace atmosphere, convenient installation, and