Maintenance planning of power plant elements based on avoided risk value

In the world's power sector, a large number of operating coal-fired power units are characterized by a relatively long service life. These power units often constitute the basic source of energy in individual national electric power systems; this implies that their reliability affects the reliability of the entire system of a given country. Therefore, the assessment of the current technical state of the power unit elements and of the risk related to their further operation is an issue of considerable importance. In this paper, we present an analysis of the assessment of the probability of the failure of steam piping being a critical element of the power unit. Theoretical calculations of the probability of failure are presented and a method for its estimation using non-destructive testing of the steel metallographic microstructure is proposed. Further, a rational estimation method of the optimal time to replace the steam pipelines is proposed on the basis of the avoided risk value and the modified net present value index of the discounted cash flows related to the risk.