Steel pipes and tubes can be manufactured in different methods, the main methods are electric resistance welding (ERW), fusion welding (EFW), double submerged arc welding (DSAW) and seamless pipe manufacturing (SMLS). The seamless pipe manufacturing process starts with the transformation of raw materials into steel bars. In different types of rolling mills steel bars are formed into a solid round shape, called billet, which is heated and pushed or pulled over a piercing rod producing a hollow tube or shell. Due to the heating production process seamless pipes are normalized and should have a consistent steel pattern throughout its range.
Seamless tubes are mostly used to transport high pressure gas or fluid within the oil & gas, petrochemical, chemical and power industries. As the manufacturing process does not include any welding, seamless pipes are perceived to be more non-corroding and to withstand higher operating pressure and mechanical stress than welded steel pipes (according to ASME). Despite higher initial costs seamless pipes are more cost-effective when taking potential of defects, replacement and comprehensive tests for welded pipes into consideration.
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