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The determination of reinspection intervals of pressure components working at high temperature and under creep load is affected by a large number of uncertainties. One of the most important factor that can be taken into account for the determination of reinspection intervals is the residual life, which can be evaluated by calculation orexperience. Another important information is given by the result of metallographic replicas which can detect the level of creep damage. Moreover useful information on defects of nature other than creep such as corrosion, fatigue, erosion etc. come from the results of NDT examinations. All these information, combined with risk assessment related to the specific component, can help the designer and the inspector to determine the reinspection intervals which allow a safe operation of the component.
A research on this subject has been carried out by ISPESL - the Italian Authority in charge of the safe operation of pressure vessels and boilers - and has brought to interesting results. The Authors propose a new risk-based method for the determination of reinspection intervals based on ISPESL experience on this field. This method has been tested using ISPESL database on plant working under creep load giving interesting results for practical application and encouraging further research in this direction.