Bends are bended by complete sets a set of bending equipment for bending. Bends can be manufactured by the cool simmering and hot pushing two technologies. No matter which kind of machine equipment or pipe, most of them use bends for oil transportation, gas transportation, fluid transportation, bridge construction project, etc. The materials for bends include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metal and plastic.

Classification of bends
Carbon steel bends: ASTM/ASME A234 WPB, WPC
Alloy bends: ASTM/ASME A234 WP 1-WP 12
Stainless steel bends: ASTM/ASME A403
Low temperature steel bends: ASTM/ASME A402 WPL3-WPL 6
High performance steel bends: ASTM/ASME A860 WPHY 42-46-52-60-65-70

The bend can be divided into the long-radius bend and the short-radius bend according to their radius of curvature. The long-radius bend means that its radius of curvature equals 1.5 times the outer diameter of pipes, that is, R=1.5D. The short-radius bend means that its radius of curvature equals the outer diameter of pipes, that is, R=1.0D.(D is the diameter of the bend. R is the radius of curvature.) According to the pressure rating, bends can be divided into 17 kinds, including SCH5s, SCH10s, SCH10, SCH20, SCH30, SCH40s, STD, SCH40, SCH60, SCH80s, XS; SCH80