Circular hollow structural sections (round HSS) are typically produced to structural tolerances and standards such as ASTM A500 or A513, while standard and mechanical pipe in this category is produced to pressure or fluid-service specifications. The applicable product standard, wall-thickness-to-diameter ratio, and end-use documentation are the primary classification factors. Antidumping orders on circular welded pipe and on HSS are often separate, so correct classification directly affects duty liability.

Yes, the US has maintained antidumping and countervailing duty orders on circular welded pipe from multiple origins over many years. Importers should query the CBP ADD/CVD search tool and the USITC order database using the specific HTS subheading and country of origin before entry. Scope rulings from the Department of Commerce can clarify whether a particular product specification falls within an active order.