Coke Drum Wall Thickness Sizing Based on Measured Operating Quench Loads

Coke drums experience severe thermo-mechanical loading during operation, and incur a significant portion of their total damage during the quenching period. The loading during the quenching period causes the cylindrical shell of coke drums to rapidly develop flaws and exhibit bulging patterns. To mitigate against this type of damage requires an understanding of how to incorporate the thermal loading into damage assessments. The current study uses temperature measurements to first categorize the loading during quench into four types of thermal events: cold spot thermal gradients, hot spot thermal gradients, axial thermal gradients, and circumferential thermal gradients. The probability distribution functions for each type of thermal event are then characterized using measured temperature and strain data, to be used as the forcing function to evaluate damage on the vessel. A fatigue assessment methodology that incorporates the cumulative impact of the defined forcing function on the estimated shell fatigue life is presented.