Mechanical performance study of 140 MPa ram blowout preventers at 180°C high temperature

With the advancement of deep oil and gas resource development, the reliability of blowout preventers (BOPs) under extreme working conditions faces significant challenges. This study focuses on a 2FZ28-140 ram BOP, systematically investigating the mechanical properties of its shell material, F22 M, in high-temperature environments. Through tensile tests at 22°C and 180°C combined with a microscopic fracture morphology analysis, the influence mechanism of temperature on the material's mechanical properties was revealed: at high temperatures, the yield strength decreased by 7.0%, while the number and size of dimples on the fracture surface increased, indicating that the material still maintains excellent toughness. By establishing a thermo-mechanical coupling model, this study comprehensively evaluated the stress distribution characteristics of the shell under full pressure, semi-sealing, and full-sealing conditions. The research found that under normal temperature, the stress concentration zone under the full-pressure conditions is located at the intersection line of the ram cavity (maximum stress of 512 MPa), while at high temperatures, due to thermal expansion constraints, the stress concentration shifts to the flange bolt holes (607 MPa), which remains below the material's yield strength. Through theoretical calculations and numerical simulations, it was verified that the shell strength meets design requirements at high temperatures, and the coupling effects of stress distribution and thermal loads were elucidated. A safety evaluation method is proposed for BOPs based on multi-physics coupling, providing critical theoretical support for the structural optimization and reliability design of BOPs under extreme conditions. It enhances the safety and service life of BOPs in deep oil and gas drilling and production, demonstrating a significant engineering application value.