Comparison of Residual Stress Relief Processes for Crude Oil Storage Tank Roof Plates

Residual stress relief processes for crude oil storage tank roof plates mainly include overall heat treatment (stress relief by holding at 500℃), local heat treatment (infrared heating of the weld zone), and temperature difference stretching method (reverse stress field elimination). Overall heat treatment releases stress through recrystallization, but consumes a lot of energy. Local heat treatment can reduce stress peaks by 30%-50% and is suitable for simple welds. The temperature difference stretching method achieves 50%-70% stress relief through precise temperature control Δt, but is sensitive to process parameters.

Process selection needs to comprehensively consider the structural characteristics of the tank roof: 1) Segmented overall heat treatment is recommended for large-diameter tank roofs, combined with internal combustion heating to control deformation; 2) A combination of local heat treatment + vibration aging is recommended for complex weld areas, reducing costs by 40%; 3) The temperature difference stretching method is suitable for thin-plate structures (thickness ≤ 12mm), and heat input needs to be controlled to avoid grain coarsening. After using infrared local heat treatment on a certain 100,000 m³ storage tank, the ellipticity error of the tank roof decreased from 8‰ to 3‰.

Optimization directions include: 1) Developing digital twin models to predict stress distribution and guide process parameter optimization; 2) Introducing Hauke PT aging technology, which can achieve a stress relief rate of 80%-100%; 3) Establishing a residual stress-fatigue life correlation database to provide quantitative basis for process selection.