Spiral steel pipe type is made by strip, seamless steel tube type is made by round steel, difference is very big, production process different:spiral tube is to use strip steel welding, can see the weld;

ASTM A179-Standard Specification for Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes

Longitudinal welded pipe is one of the welded pipes. Due to different production processes, longitudinal welded pipes can be divided into high-frequency longitudinal welded pipes and submerged arc welded longitudinal welded pipes

A fitting is a weldable pipe fitting that allows for change of direction of flow, to branch off, reduce pipe size or attach auxiliary equipment.

In general, structural pipe is a type of steel construction pipe that meets certain standards of chemical composition and mechanical properties.

API 5CT is standard technical specifications for steel casing and tubing pipes used for oil wells in petroleum and natural gas industries.