Abstract: The present invention is a cycle monitoring system and method that acquires, logs and analyzes analog and/or digital signals from component sensors in a process control plant such as a nuclear power plant. The system continuously monitors the sensors and records steady-state and transient phenomena. Compression of the data is performed to reduce storage load. The compression ratio for transient data is driven by a threshold indicating a measurement signficant to stress determination. Transient data is retained at a higher sampling rate, so that the parameters of transient such as the maximum value can be determined for stress analysis. The stress analysis determines pressure and thermal stresses which are used to calculate a usage factor which indicates the stress age and thus the remaining life of a component. The system provides estimates of fatigue accumulation associated with selected locations of critical power plant components.