The Effect of Strain Hardening on Mechanical Properties of Line Pipes for the Application of Pressure-Containing Sleeves

Abstract

The pressure-containing encirclement sleeve (Type B) is one of the most widely employed oil and gas pipeline repair methods. It is used for both in-service pipelines and various types of defect repairs, including leakage and nonleakage defects, cracks, and internal and external metal loss. According to the pipeline design pressure, Type B sleeves are opted for due to the possibility of leakage and the consequent pressurization of the sleeve. Thus, the pipe commonly used has similar characteristics to those employed in the pipeline. In this research, the multistage strain hardening method was used to expand the pipelines’ internal diameter, using it as a pressure-containing encirclement sleeve. An experimental investigation was conducted to assess the mechanical and physical properties of the sleeve made from line pipes 915 and 1,067 mm in diameter. FEM was employed to evaluate the sleeve’s stress analysis. The results demonstrated that the characteristics of the pressure-containing sleeve, produced using strain hardening, met the appropriate standard requirements. The mechanical and physical properties of the sleeve improved following strain hardening. Furthermore, the maximum operating pressure of the pressure-containing sleeve increased following the cold working method, often exceeding that of the repaired pipelines.