Closed-End Straight Radiant Tube for Industrial Furnaces Custom Round-Flange Radiant Tube Assembly with Extended Inner Connection Tube | FH® Alloy FH® Alloy manufactures closed-end straight radiant tubes for industrial furnaces and heat treatment equipment, providing custom solutions for customers who require indirect heating, stable installation, and customized end connection structures. Compared with standard straight radiant tubes, this type features a closed-end