Bends are widely used in water supply and drainage systems, pipelines of steam and hot water, main and field oil and gas pipelines, process pipelines in the oil, gas, chemical and petrochemical industries.They are produced of carbon and alloy steel of ordinary quality, high quality, that have cold-resistant and heat-resistant properties, and resistance to aggressive media.
The shape and technical requirements for the production are regulated by corresponding GOST, OST and Technical specifications.
According to methods of manufacturing there are following types of bends:
- Short radius bend
The method of pulling through horn-shaped core having certain geometric parameters is used for their manufacturing.
- Bent branches
cold bending method
Due to high stresses in the metal during deformation, cold bending produces bends with large bending radiuses (from 5Du), small bending angles and wall thickness.
hot bending method
For the production of thick-walled bends at high pressure with the required radius and bending angle it is required to heat the deformation zone during the bending process. For these purposes is used HFC induction heating.
- Sectional-welded bends
Bends are made of several pieces (sections) joined by welding. As a rule, they are produced of carbon and low-alloy steel.
- Stamp-welded bends
This type is widely used in main and field pipelines with diameter up to 1420 mm and operating pressure up to 9.8 MPa. Manufactured by the method of hot stamping. Electric-welded tubes and metal sheets are used as blanks.
- Turned taps (triangles)
This type is produced by machine processing of the blank. Bar sections or forging (with normalized mechanical properties) are used as blank. This type is widely used in high pressure pipeline systems up to 100MPa.