Online valve monitoring, also called “ValveWatch,” is a state-of-the-art method for improving the reliability of safety critical valves during operation. This well-known method has been used for almost two decades to reveal the possible failures of valves, actuators and control systems. This paper reviews some of the existing literature about ValveWatch technology to provide more detailed information about this online monitoring approach and its benefits. The possible causes and effects of failures associated with safety critical valves based on the existing literature are identified and summarized in this paper. Safety critical valves mainly include Emergency Shut Down and Process Shut Down (PSD) valves connected to Process Shut Down (PSD) systems. Three types of sensors that comprise part of the ValveWatch system will be identified and explained in this paper: the stain gauge, the dynamic pressure gauge and the static pressure gauge on the actuator. The function and logic of these three sensors are explained in this paper. All of the problems associated with valves, actuators and control system are identified and listed in a table and the probability of detecting these failures through visual inspection as well as online monitoring is assessed. A method of utilizing equations to calculate the probability of failure detection for valves, actuators, control system and the whole assembly through visual inspection as well as using sensors is developed. Additionally, the methodology given in functional safety and International Electrotechnical Commission 61,508 to calculate Diagnosis Coverage is used in this paper, and future research work to address condition monitoring for pressure safety valves and check valves is proposed. A Separate research is required to improve the reliability of the ValveWatch system.
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