ASTM 213 steel tube is commonly used in heat exchangers and superheaters. Commonly used dimensions (outer diameter x wall thickness) are mainly Φ19mmx2mm, Φ25mmx2.5mm and Φ38mmx2.5mm seamless steel tubes. Standard tube lengths are 1.5, 2.0, 3.0, 4.5, 6.0, 9.0m, etc. The use of small tube diameter can increase the heat transfer area per unit volume, compact structure, reduce metal consumption, and increase heat transfer coefficient.