The proprietary remaining life estimate software developed by USTT/MP was created due to the fact that no current publicly available codes or practices that formerly addressed reformer tube remaining life, particularly a remaining life method that integrated inspection data.
We do use principles and elements of post construction standards such as API 571, API 579, R5, and/or BS7910. However, the connection is more indirect as these standards don't formally have parts or modules that reflect the complexity of reformer tube remaining life.
The USTT/MP remaining life model considers the strain accumulated in a given time, or age of the tube as a means of estimating the remaining life. This concept relies upon the precept due to historical operation strain accumulation is a valid means of projecting materials degradation and remaining tube life forward. Measured eddy current indications for wall damage are included with high priority in the analysis, since cracks indicate the actual initiation of the tube failure mode. Of course, the laser diametrical data is used for the strain measurement input in the software.
The model integrates multiple degradation mechanisms that occur in reformer tubes. These include thermal ageing/softening, strain softening, coarsening of the grain structure (especially secondary carbides), and increase of mobile dislocation density, creep void formation/cavitation and growth. The integration of multiple degradation types allows for realistic estimates of remaining life based upon strain accumulation over the age of the tube.