Exploratory study on load and resistance factor design of pressure vessel for subsea blowout preventers

An exploratory study on pressure vessel design procedures based on load and resistance factor design method for subsea blowout preventers subjected to external hydrostatic pressure is presented. Based on the procedures of working stress design method, the performance function of load and resistance factor design method is presented, and the design code is calibrated. The sensitivity analysis is done in order to investigate the effect of statistical characteristics of variables on the partial safety factors and design thickness of pressure vessel. The design procedures and results are compared with those of the traditional working stress design method. The results show that the load and resistance factor design method provides consistent reliability among the components of pressure vessel such as cylindrical shell and hemispherical head, and the method is less conservative than the working stress design method. Besides the conventional material of UNS S31603 stainless steel for subsea pressure vessel, UNS S31803 duplex stainless steel is also used, which could cause economic design results. Furthermore, the validity of the design results is confirmed by performing finite element model analysis by means of ANSYS software, which shows that the design thickness is secure enough when the pressure vessel works in 3000 m ultra-deep seawater regions.