Straight Radiant Tube with Round Flange for Industrial Furnaces Custom Heat-Resistant Radiant Tube Assembly | Drawing-Based Manufacturing | FH® Alloy FH® Alloy manufactures straight radiant tubes with custom round flange connections for industrial furnaces, heat treatment equipment, and indirect heating systems. This type of radiant tube features a long straight tube body combined with a machined circular flange, end connection, and supporting structure, making it suitable