Simulation analysis of thermal-stress coupling for deep hole pressure retention sampling ball valves

The temperature and pressure inside the borehole are higher and higher with the increasing depth of the borehole. As a technical method to effectively obtain the in situ state of the underground core, the effective realization of the in situ pressure retention under the high temperature and pressure environment has become one of the key signs to test the reliability of pressure retention sampling. Thus, ball valves were selected as key devices for pressure retention sampling and simulation analysis of thermal-stress coupling, and the stress and deformation law of ball valves in the environmental parameters of 15,30 MPa and 0,250 ℃ were analyzed. The results of numerical simulation are as follows. ① The maximum equivalent stress and deformation values of three materials of 316L, 42CrMo and Inconel718 under the action of static pressure from 15 to 30 MPa were compared, and the 42CrMo was preferred as a material for the fabrication of ball valves, considering the cost of processing. ② The maximum deformation values of ball valves is increasing when the temperature is increasing from 0 ℃ to 250 ℃, but the growth rate is only 1.05%. The maximum equivalent force is increasing with slight fluctuation, showing an increasing overall trend. The maximum fluctuation is 12.76 MPa, which is in the effective sealing range of ball valves. The simulation results could provide theoretical data for the reliable sealing of pressure retention ball valves in the deep hole.