Konseptstudie for levetidsforlengelse i konstruksjoner
In light of the current situation on the Norwegian continental shelf with respect to the increase in the number of aging facilities, there is currently a great need for knowledge about the challenges of aging mechanisms and lifetime extension. The challenges of operating beyond the design lifetime is not due to the SSC's specific age, but to operations and maintenance organizations' ability to predict and verify the condition of the individual SSC, as well as their ability and willingness to perform proper maintenance. In the nuclear industry has this problem been on the agenda since the late 70's, this to verify if it was technically safe to operate the power plants beyond the 40 year operational limit. The question that needed to be answered was whether the aging effects could be handled in a responsible manner so that power plants could operate within the original safety margins in the extension period. To answer this question, it was put into effect several research projects to determine the effect of aging on nuclear power plants. Over time, the information from these projects has been used to develop and improve a system for evaluating safe implementation of life extension for nuclear power plants. To increase knowledge about aging mechanisms, it is important to establish maintenance systems that capture trends of degradation in SSC’s. On behalf of this documentation it will be possible to develop new state of the art evaluation systems for verification of condition. In addition, it would be natural to maintain the exchange of experience between industries with similar issues such as the nuclear power industry. For load-bearing structures are the greatest challenges in the operational phase associated with the verification of integrity, after either modifications that provide load changes in structure, or degradation and modifications that change the capacity of the structure. In addition, it may be difficult to update the analysis in accordance with the regulatory changes for load calculations, and to implement the updated meteorological data such as wave loads, ocean current and wind. The capability to establish good structural analysis models are therefore entirely dependent on exact status data and documentation from design, fabrication and installation phase. At the condition assessment of the load-bearing structures, there will also be important with accurate inspections. The reason for this is that the aging mechanisms can occur in all phases of the design life of the load-bearing structures, this is due to variations in operating environment and stresses that it is not taken into account in the design criteria. Therefore the focus of life extension concept for load-bearing structures should be at risk management, through the use of updated analytical models for the structure based on the DFI-, inspection- and maintenance data. For load-bearing structures the notion of safe operating time should be used rather than design life. This is because the design life will be object of change as a result of updated status data, re-analysis and regulatory changes.