Integrity checks of existing pipelines are in general based on ILI runs. Stress analyses are not indented for replacing ILI runs, but for providing additional information about the integrity of existing pipelines. The additional information, derived from stress analyses, can be following:
- Identify locations with high stresses due to operating conditions
- Code compliance check for modified operating conditions, e.g. elevated temperatures
- Integrity checks for geohazard scenarios, e.g. landslides and seismic faults
- Sensitivity study regarding pipe-soil interaction, e.g. for upheaval buckling
- Sensitivity study regarding operating conditions and pipe parameters
- Strain based design to identify limit states
In the past decades the stress analysis of pipelines (code compliance check) was based on the wall thickness calculation due to internal pressure, but not on the actual (as-built) alignment of the entire pipeline due to lack of required hardware and software, hence the above mentioned information is not available for existing pipelines.
Nowadays, hardware and software allows in principle such analyses, but the effort and costs are high without effective pre- and postprocessing routines. Stress analyses of 100 km pipeline per day is possible with effective pre- and postprocessing routines in combination with the commercial software ABAQUS. Such pre- and postprocessing software was developed by the author and was applied in the last few years for the integrity check of some thousand kilometers of pipelines for modified operating conditions and zones prone to geohazards.