Abstract

A Nuclear Power Plant (NPP) consists of normally operating and emergency standby systems and components. The failure of any operating component will lead to a change in the state of the plant. Control of the processes in the plant is an essential part of the plant operation. The most common control element in the process control systems is the control valve. The control valve manipulates a flowing fluid, such as steam, water, gas, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point. In order to ensure the high reliability of the system, component reliability should be ensured. In this paper working principle of control valve and different failure modes by which control valve can fail has been discussed. Reliability of the control valve has been estimated from the mechanistic models by using structural reliability methods.

Key words: Control valves, reliability, mechanistic models, FORM.