ABSTRACT
The analysis of operating experiences, e.g. using failure and maintenance data, gives valuable information on components' behaviour in their operational environment. This knowledge can be used to reveal weaknesses and ageing in components, and to plan more effective maintenance and test practices to improve the component reliability.
Reliability engineering offers both qualitative and quantitative methods for data analyses. Failure mode and effects analysis (FMEA) and maintenance effects and criticality analysis (MECA) are systematic analysis methods which are commonly used in the design stage. In this chapter their use in the analysis of operating experiences is demonstrated through a case study.
The efficient use of operating experiences requires systematic data collection practices, which are widely used in the nuclear industry. Our study is based on data obtained from TVO 1 and 2 nuclear power plants' failure data collection system. We describe an analysis of motor operated valve operating experiences in four safety related systems. The data consist of 181 failure and maintenance descriptions, which have been reported during the observation period 1 January 1981 to 31 December 1989. The analyses cover failures of both the closing valve itself and its electromechanical actuator.
130 In the qualitative analyses, classifications were made on valve parts, failure modes, causes, effects, detection, and criticality, and recurring failure causes and significant problem areas in valve operability were studied and identified. The failure and maintenance descriptions are documented on particular FMEA and MECA sheets, from which data are easily retrievable and updatable for further analyses. As examples of quantitative studies, statistical analyses concerning repair and unavailability times and failure trends are demonstrated.
