Design and Analysis of Ball Valve for Cryogen Flow Isolation at -196°C

Abstract

Cryogenic ball valve is used in low temperature applications like transfer of LNG, Nitrogen, Hydrogen Oxygen, Argon and Helium. Designing the components of cryogenic ball valve is very critical because at lower temperature the gradient of contraction rate for the seat material and body material leads to leakage through valve and leakage of cryogens is not only dangerous, but also very expensive. In this dissertation, Design and analysis of ball valve for cryogen flow isolation at -196°C temperature is included. The detail design of cryogenic ball valve components namely body, side piece, ball, stem, seat holder, bonnet is carried out as per the design requirements stipulated by various relevant standards like API 6D, ASME B16.34, ASME B 16.5, BS 6364. 3D models of various parts and assembly for the cryogenic ball valve are created using Creo parametric 2.0. Finite element analysis for critical components of cryogenic ball valve is carried out using ANSYS and the values of von Mises stress and total deformation are obtained for required boundary conditions. The results obtained from finite element analysis are validated using standard analytical calculations and found in good agreement with each other. The computational fluid dynamics (CFD) analysis is performed for each 10° rotation of ball to obtain detail fluid characteristics passing through the cryogenic ball valve at various locations. The pressure and velocity contours are plotted which indicates the change of pressure and velocity profile with respect to position of ball in the valve. This analysis helps to identify the region of vortices and possibilities of cavitation in the valve. Design optimization of body is performed which leads to reduce unnecessary weight and ultimately saves the material cost.