... used to the general structure and mechanical structure. Structural seamless steel pipe is used to the general structure and mechanical structure. ... pipeline,vessel,equipment,pipe fittings and mechanical structure.Size range: 1 " nominal through 24 "ODWall Thickness up through 4 " thickSpecifications & Grades ... /C, SA-335 P5, P9, P11, P22, P91SA-333, Grade 1/6 , SA-213 T5, T9, T11, T22, T91API 5LB & X ...