The engineering task
A pressure vessel is repeatedly started, heated, pressurised, emptied and cooled. Its history contains several cycle types with different pressure and temperature ranges. Nozzles, transitions, welds and tubesheets have local stress concentrations that are not revealed by static pressure design.
Fatigue requires realistic load spectra. A simplified assessment is valid only within its scope; otherwise stress ranges are determined by detail and evaluated against fatigue curves with cumulative damage.
Required design data
- Load spectrum with pressure, temperature and external-load ranges
- Geometry of fatigue-critical details
- Materials, weld details and surface condition
- Design life and count of every cycle type
Technical solution approach
Decompose the load history
Divide operation into countable pressure, temperature and combined cycles.
Select critical locations
Prioritise geometric discontinuities and regions with alternating wetting or heating.
Check simplified assessment
Apply AD 2000 S1 where loads and details remain within its scope.
Perform detailed assessment
For uncovered locations, determine stress ranges to S2 and compare them with appropriate fatigue curves.
Accumulate total damage
Sum partial damage from all cycle types and convert the result into an operating or inspection strategy.
Expected deliverables
Suitable SOL ALPHA modules
The modules form a technically plausible toolchain. Their final selection and sequence will be confirmed during the later calculation against the applicable code and project conditions.