Introduction

Pressure vessels are subjected to fluctuating loads either mechanical or thermal depending on their service subject. This loading is dangerous than other loadings as the structure will experience sudden failure without any prior indication. Hence fatigue calculations need to be part of design of a vessel.

Process equipment manufacturer from India & Abroad approached ANALYZER to seek assistance in evaluating the design of their newly developed vessels to multiple fatigue loadings using simulation techniques & provide the solution in case of any observed fatigue failure.

Workflow

• Determining the various loading conditions affecting fatigue strength of the pressure vessel.
• Preparing FEA Model for pressure vessel
• Performing the Fatigue calculations as per ASME BPVC Sec. VIII Div. 2 Part 5 & Annexure 3.F
• Preparing an easy-to-understand report for the performed FEA.

Challenges

• Preparing structured hexahedral mesh of Complete Pressure Vessel without losing critical areas of peak stresses like nozzle fillets.
• SN Curve Selection for material of construction of different parts
• Fatigue calculations for multiple fatigue loadings during complete life of vessel.

SOLUTION

The pressure vessel was analysed using Finite Element Method to determine the induced stresses due to various cyclic loadings. To assess fatigue strength for the vessel, guidelines from ASME BPVC (Boilers & Pressure Vessels Code) Section VIII Div. 2 part 5 & Annexure 3.F was utilized. The fatigue calculations were performed & fatigue damage factor is found much below unit value. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

BENEFITS

• Better insights on design modifications for alternate applications
• Optimized design with reduced material cost
• Reduced manufacturing time