Fatigue Life Prediction Model for Welded Seams of High-Pressure Water Injection Crude Oil Storage Tanks

The fatigue life prediction model for welded seams of high-pressure water injection crude oil storage tanks mainly adopts the structural stress method. It calculates the true stress through the force/moment of the weld node and evaluates the life by combining the SN curve and Miners linear cumulative damage theory. Key parameters include welding residual stress (process-related), stress concentration factor (a 0.1 increase reduces life by 15%-20%), and environmental corrosion effects (life is only 1/3 of normal in a strongly corrosive environment).

In practical applications, it is necessary to consider dynamic load transfer paths and material performance degradation, as shown in the case of deep-sea oil and gas equipment. The model quantifies the influence of stress amplitude through S-N curves (including safety factors) and integrates factors such as residual stress and geometric discontinuities, with error controlled within 15%.

Technical difficulties include: 1) Welding parameter deviation for dissimilar materials should be ≤5%; 2) Corrosion environment requires accelerated test correction; 3) Fracture mechanics models need to be introduced under multiaxial stress. After a 100,000 m³ storage tank adopted this model, the predicted life and the measured deviation