6 / 2020-04-10 00:31:24

Fracture failure analysis of the HP main steam control valve stem in a nuclear power plant

valve Stem; fracture analysis; fluid-structure coupling; fatigue fracture

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The high-pressure main steam control valve is an important device to control the start and stop of steam turbine and power change. a HP main steam control valve stem in a nuclear power plant broke during service. In this paper, materials of the valve stem and the ball joint head, as well as the fracture surface were experimentally analyzed. The hydrodynamic model and the structural contact model of the valve stem and the ball joint are established. Based on the CFD dynamic grid technology and the finite element method, the fluid structure coupling characteristics of the valve are analyzed. The results of material experiment analysis are consistent with the results of finite element simulation. The comprehensive analysis shows that the failure reason of the valve stem is: the change of opening of HP main steam control valve causes the significant pressure fluctuation in the pipeline and the valve. Under the action of fluctuating pressure load, the valve stem and the ball joint thread is subjected to alternating stress with a high average stress, which causes the wear and fatigue failure of the thread tooth surface.