Fatigue and Cyclic Service Analysis for CRN Registration

Pressure vessels and piping systems subjected to repeated pressure or temperature cycles are vulnerable to fatigue cracking. When equipment operates in cyclic service, CRN applications must include fatigue analysis. Kopfkino provides ASME-compliant fatigue analysis as part of CRN registration packages.

When Is Fatigue Analysis Required?

• Autoclaves: equipment that cycles to full pressure multiple times per day
• Reactor vessels with frequent startup/shutdown cycles
• Pressure vessels in reciprocating compressor service (high-frequency pulsation)
• Vessels subject to thermal shock — rapid heating or cooling
• Heat exchangers with large tube-to-shell temperature differentials

ASME Fatigue Analysis Methods

• Elastic fatigue analysis: S-N curves from ASME Division 2 Annex 3-F
• Elastic-plastic fatigue analysis for high-strain, low-cycle conditions
• Cycle counting methods for variable amplitude loading (rainflow counting)
• Cumulative damage (Miner's rule) for multi-amplitude spectra

Frequently Asked Questions

Do autoclave CRN submissions always require fatigue analysis?

Not always, but usually. Most autoclaves exceed ASME fatigue screening limits due to their repeated pressure cycles. Kopfkino screens every autoclave project for fatigue requirements.