Method of determining a hem edge radius in the production of large diameter pipes

Pipeline transportation systems including large diameter pipes as their integral part are considered to be dangerous man-made objects. Their break down and failures result in serious dangers for people, engineering and natural objects. Therefore, they must meet the demands in reliability and safety. The current development of the production of large diameter electric welded pipes depends on the requirements of the fuel companies. Due to the depletion of traditional fields and the desire to expand markets fuel companies are forced to transfer to the production and transportation of hydrocarbons in new conditions. The development of new projects, for example, “Power of Siberia” envisages running of pipelines in tectonic activity areas, which also increases the demand in pipe reliability. One of the trends of the production of large diameter electric-welded pipes is the increase of the strength group. The increase of reliability and efficiency of large diameter electric-welded pipes is achieved not only by the increase of mechanical properties of pipe steels by their doping, but also by the increase of geometric requirements for welded pipes. In the production of large diameter pipes basic geometric requirements are the following: the deviation of the outer pipe diameter, roundness, and deviation from the theoretical circle. Disruption in the production technology leads to defects in pipes. Geometric defects in pipes are formed in billets. One of the principal geometric defects in pipe production is deviation from the theoretical circle. Correction of this defect is accomplished by calibrating on a mechanical expander. Deviation from the theoretical circle is due to the wrong selection of the radius of the near-edge zone during hem edge forming on the press. The method for calculating and determining the radius of hem edge forming after back springing is offered.