A number of Design Codes provide prescriptive methods for the calculation of creep and fatigue damage. The Codes tend to be very general, in some cases very conservative, and not necessary related to headers, manifolds and pipe connections which can experience multiple "on-off" and load change cycles as well as variations in temperature.
Doosan Babcock have, using the methodology described in the Codes, enhanced the analytical procedures to predict more accurately the levels of creep and fatigue damage for the complex loading operations experienced by pressure part components in modern or upgraded plant.
The resulting damage predictions can then be confirmed using other services we offer, such as NDT, metallurgy and visual inspections and surveys, to build-up a comprehensive safety case.
Although normal practice is to use as input published data, in terms of material properties and fatigue curves - as we have our owntest facilities - specifically derived data may also be used for comparison purposes - removing some of the conservatism from the analysis.
To assist the station operator assess the plant and determine how it may be operated in the future, the derived creep and fatigue damage fraction are normally presented in an interaction diagram.