Structural Analysis by Finite Element Method in Ball Valves to Improve Their Mechanical Properties

Abstract

Thermoelectric power plants have steam lines that are mainly structured by pipes, y-pattern globe valves and ball valves. According to international databases (Rogers in The Guardian 18, 2011 [7]), the most common problems in valves are erosion and material thermal expansion that produce pressure drop, heat loss, material leakage and crack nucleation. For these reasons, while engineering process is applied, structural analyses are generated to show the material behavior under a linear external agent (Stolarski et al. in Engineering analysis with ANSYS software. Butterworth-Heinemann, 2018 [8]). However, the steam tends to behave in a saturated way before it becomes in a superheated steam to improve thermal efficiency and work capability. So, through Mollier diagrams, ASME and ASTM standards, mechanical properties of materials and the boundary conditions that supply a fixed value constrain, and contact constrains presented in ball valves. It’s proposed a variable structural elastic-linear static analysis with an isotropic material using the Finite Element Method. Where a homogeneous behavior in the variation of pressure and temperature represent the structural changes of the valve while is working with saturated and superheated steam with the aim to consider and understand the critical components of the assembly, which in this case of study are; the body, the ball and the seats. In such a way that, applying a load similar to the fluid characteristics and unloading the system, total displacements and principal stresses can be obtained during each step. And through Von Mises failure theory. It can be obtained the more prone areas to failure by elongations/contractions that could affect the correct function of the valve during service.