Oil and Gas - Life Assessment Methodology

Life Assessment Methodology for Coke Drums

The large pressure vessels used in the coking process (coke drums) experience large thermal gradients during each cycle due to rapid heating and cooling. The resulting temperature distributions are not axisymmetrically uniform. During the cooling portion of the cycle, typically 3 hours in length, cold water flows through channels in the coke, intermittently quenching the still hot vessel. This leads to uneven cooling and subjects the vessel to significant axial and circumferential thermal stresses. In addition to the thermal gradients, the drums often loose their cylindrical shape as bulges form due to the daily heating, cooling, pressure and weight loading. 4D engineers have characterized the stresses and strains due to these loading conditions based on extensive parametric analysis of Coke Drum applied loads, vessel geometries, and bulge geometries using analytical and numerical (finite element analysis) methods.

The parametric study results are used with field temperature, pressure and coke material property measurements and vessel geometry (determined via laser and/or light scanning) to estimate stress/strain histograms.