RBI and probabilistic life assessment for components of coal and co-fired power plants

Risk-based inspection (RBI) is not always applied in power plants that are generally not seen to carry similar safety and other hazards as e.g. some branches of the chemical industry. Hence the supporting standardization, industrial guidelines and available services for RBI activities have not been as well established in the power industry. Such support has been addressed for example in the European projects RIMAP, iNTeg-Risk and SafeLife-X, with results that include recommendations towards the evolving European standardization on risk-based assessments. This paper aims to explore the benefits of probabilistic life assessment in supporting RBI and related maintenance planning. The details in the input information, including the progression rates of the active damage mechanisms, will affect the associated uncertainty in the probability of failure, predicted minimum life, and the resulting conclusions on next inspections. However, successful probabilistic treatment of the input information can allow realistic treatments of the models for the indicated or postulated damage mechanisms, and by using for example Monte Carlo approach, the outcome prediction is not sensitive to the mathematical formulation of the individual or combined damage mechanism models. The examples have been selected from components subjected to high temperature service in applications where one can expect unavoidable damage accumulation in long term operation, and/or multiple mechanisms affecting the component life. Implications are discussed in terms of implementation in RBI and other aspects of managing the assets.