Modal and structural analysis on a main feed water regulating valve under different loading conditions

Abstract

As a key device influencing the safety and the economy of nuclear power plants simultaneously, the main feed water regulating valve (MFWRV) controls the flow rate flowing to the steam generator. In this work, modal and structural analysis is conducted under different loading conditions to investigate vibration characteristics and mechanical characteristics of MFWRV. The results show that the combination of loading conditions has little effect on the natural frequency and the mode shape of MFWRV. However, it influences the results of structural analysis significantly. Compared with the fixed internal pressure, the variable internal pressure promoted the maximum stress intensity when the valve opening (L/Lmax) is smaller than 80%. The maximum deformation when the seismic load is considered is almost three times as large as it when the seismic is not considered. The seismic load always has a positive effect on the maximum gap (gmax) between the valve core and the sleeve. However, the variable internal pressure only has a positive effect on gmax relative to the fixed internal pressure when L/Lmax = 40 ~ 90%. Besides, the variable internal pressure has an evident negative effect on the maximum sliding distance (sdmax) between the valve core and the sleeve relative to the fixed internal pressure under the low and the middle valve opening. This work provides a reference for the structural design of the main feed water valve and other similar valves.