Life in plant - challenges and solutions

Power plant structures operating at high temperatures are designed for a lengthy explicit or implied minimum life, dictated by the expected life-consuming damage mechanisms like corrosion, creep, fatigue and other forms of wear and tear. The actually realised damage shows highest rates at locations of the most adverse combination of material properties (weakness e.g. in welds), loads (mechanical, environmental, thermal) and other features like geometry and deviations from the intended condition. In case of no additional surprises, the technically justified life is likely to nevertheless differ from the assumptions in design. The explicit or implied "safety factors" will offer on average some extended life and service potential to components even after operation up to and beyond the nominal design life. To avoid surprises, it remains wise be well informed of the evolving material and component condition of an ageing plant. The common questions are when and how should one measure to achieve the required confidence for decisions to run, repair or replace. In this paper we contemplate the challenges for managing the life of critical components of current and future power plants. Radical changes may happen in the merit order of plants by e.g. shifting fuel prices or public policies, and this could naturally affect the need, available budget and planning to maintain a given plant. Less impact is expected in the established principles of the technical operations like monitoring, inspections and interpretation of the results. However, changes are likely in selected areas related to materials and component lifing.