NDLI: The Influence of Switch Temperature on Coke Drum Fatigue Life

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Marangone, Fa´bio De Castro Tinoco, Ediberto Bastos Gomes, Carlos Eduardo Simo˜es
Copyright Year	2010
Abstract	Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.
Sponsorship	Pressure Vessels and Piping Division
Starting Page	999
Ending Page	1006
Page Count	8
File Format	PDF
ISBN	9780791849224
DOI	10.1115/PVP2010-25422
e-ISBN	9780791838785
Volume Number	ASME 2010 Pressure Vessels and Piping Conference: Volume 3
Conference Proceedings	ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference
Language	English
Publisher Date	2010-07-18
Publisher Place	Bellevue, Washington, USA
Access Restriction	Subscribed
Subject Keyword	Water Fatigue life Cycles Stress concentration Temperature Cooling Bending (stress) Coke Equilibrium (physics) Thermocouples Vessels Switches Shells Fracture (materials) Pressure Stress Transients (dynamics) Temperature gradient Concretes Heating Pressure vessels Quenching (metalworking) Finite element analysis Thermal analysis
Content Type	Text
Resource Type	Article

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