Summary
Every heat up, cooldown, pressure swing, and unplanned transient consumes a measurable fraction of a component’s fatigue life, and most plants track that consumption against design-basis cycle counts set decades ago with deliberate conservatism. The result is a widening gap between assumed and actual damage — one that becomes expensive the moment an operator has to justify continued operation, defend a license renewal position, or explain a limiting location to a regulator. Structural Integrity Associates (SIA) has spent more than 30 years closing that gap for nuclear power plants and industrial operators, and our engineers help write the industry guidance that shapes how metal fatigue is managed.
SI:FatiguePro is the software expression of that experience. Developed in partnership with the Electric Power Research Institute (EPRI) and now the most widely used fatigue monitoring application in the U.S. nuclear industry, it converts data your existing plant instrumentation already produces into a continuously updated picture of fatigue usage. Automated Cycle Counting applies event-specific pattern-recognition logic to raw instrument data, categorizing transients against design basis definitions rather than waiting on manual logs. Cycle-Based Fatigue then recalculates usage from those counted events instead of design transient allowances. Stress-Based Fatigue monitoring goes further, replacing the single-stress-term methodology of EPRI FatiguePro 3.0 with multi-axial stress calculations that combine thermal, mechanical, and pressure contributions while accounting for component geometry, material, and operating conditions.
SI:FatiguePro, in its fourth release, includes the analytical depth that modern fatigue management programs require. Environmentally-Assisted Fatigue is calculated internally through NUREG-based Fen multipliers driven by actual plant data rather than bounding assumptions. A fatigue crack growth module evaluates postulated flaws in monitored components to support flaw tolerance and ASME Section XI Appendix L evaluations. Linear projection of cycles and usage shows how much margin remains and when it runs out, and a Thermal Transient Library makes “what-if” simulation straightforward. The application is configured for each site, and its reach extends well past the reactor building — SI:FatiguePro monitors hydrogen fueling station tank arrays to demonstrate that service conditions are less severe than design, and it supports high-pressure wellhead equipment subject to BSEE load monitoring requirements.
What makes that worth doing is the decisions it enables. Historical operating data carries fewer limiting assumptions than original design analysis, so documented usage frequently reveals margin that conservatism had hidden — margin that supports operation through the original design life and into extended operation, and that answers the questions regulators, insurers, and state inspectors ask about pressure components and piping systems under cyclic duty. SIA pairs the software with the surrounding program: EAF analysis, fitness-for-service assessment under API 579-1/ASME FFS-1, fatigue management consulting and handbooks, inspection services targeted at minimizing detectable flaw size, design modification, and repair support. Explore the broader asset performance management portfolio or contact Structural Integrity Associates to discuss fatigue monitoring at your facility.