C-1/2 MO vs 1CR-1/2MO: A Comparative Study of Coke Drum Shell Materials
J. Fernando, E. Falo, M. Iverson, H. Kwok, S. Yuen, H. Guo, L. Wong, L. Chan
To mitigate the impact of severe thermal loads during operation, two different design methodologies are typically adopted when selecting base metal materials for coke drum fabrication. Here is a study that investigates eight coke drums from the same upgrader unit, six of which were fabricated using C1/2Mo Alloy, with the remaining two fabricated using a 1Cr1/2Mo alloy. An extensive experimental testing program excavated from all eight coke drums is undertaken along with an assessment of historical data available for both sets of drums, to quantify the performance of each base metal material.
Designing Coke Drum Skirt Details to Avoid Failure
J. Fernando, J. Bedoya, M. Ackman, N. Nemade, H. Kwok, L. Chan
Given the susceptibility of skirt-to-vessel attachment welds to fatigue damage, most contemporary coke drums incorporate keyholes into skirt designs to relieve stress at the attachment weld. Here is a study that aims to extend a proposed linear regression modeling approach to fatigue assessment of the vessel side of attachment welds and the top keyhole, to provide a more comprehensive estimate of fatigue performance. The proposed models together provide a methodology to quickly optimize skirt design, while significantly reducing the upfront computational effort involved.
Coke Drum Wall Thickness Sizing Based on Measured Operating Quench Loads
J. Fernando, E. Falo, H. Kwok, M. Iverson, L. Wong, S. Yuen, K. Lee, L. Chan
Coke drums experience severe thermo-mechanical loading while pyrolyzing heavy crude oil residuum, and have therefore become canonical examples of low cycle thermal fatigue failure. Here is a study that co-opts 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. A fatigue assessment methodology that incorporates the cumulative impact of the defined forcing function on the estimated shell fatigue life is presented.
Key Learnings from Large-Bore Compressor Piping Design of a Carbon Capture System
J. Fernando, L. Chan, H. Kwok, S. Yuen, S. Roberts
Thermo-mechanical loading and nominal pipe size are two critical considerations in the design/engineering of large-bore piping configurations. Here is a study that outlines several important design features that should be considered when designing systems that require large-bore piping, using the successful retrofit of a carbon capture and storage (CCS) facility as a case study.
Optimizing Coke Drum Keyhole Dimensions Using Statistical Modeling
J. Fernando, H. Kwok, L. Chan, J. Penso
Keyholes have become an important consideration in coke drum skirt design. Here is a study that investigates keyhole designs for two commonly used skirt designs to identify functional trends between keyhole parameters and stress, and proposes a simple linear regression model to quickly assess the fatigue performance of a keyhole design.
Local Post Weld Heat Treatment of a Pressure Vessel: A Postmortem Evaluation
S. Yuen, A.B. Mackay, D. McArthur, H. Kwok, J. Fernando, L. Wong
There are currently established industry guidelines on the placement of heating coils and insulation, but no standard analytical technique, engineering protocol or acceptance criteria. Here is a study that is a postmortem evaluation of a process tower that suffered significant distortion after a local post weld heat treatment (PWHT). Additional analytical techniques are also tested using Finite Element Analysis (FEA) to determine which method best predicts the deformation experienced by the pressure vessel in question.
On the Effect of Rising Liquid on Coke Drum Skirt Fatigue Life
J. Fernando, H. Kwok, L. Chan, M. Iverson, F. Ju, S. Yuen
Accurate modeling of the heat transfer from the fluid to the vessel is of critical important in the analysis of coke drums. Here is a study that focuses on comparing two temperature methodologies with different degrees of complexity by estimating fatigue life at the skirt-to-vessel attachment weld for two common skirt designs.
Reliability Improvement Concept on Welded Lip-Seal Heat Exchanger Flange Joints
S. Yuen, J. Fernando, J. Penso, H. Kwok, D. Serate
Lip-seal flange joints are commonly used in high-pressure heat exchanger design when there exists a significant temperature differential along the circumference of the heat exchanger flanges. Here is a study that investigates several special joint design features that aim to improve the reliability of such joints, particularly looking at stress distributions at critical locations of the joint to compare designs.
On the Effect of Hot-Box Size on Coke Drum Skirt Fatigue Life
J. Fernando, L. Wong, H. Kwok, L. Chan
Fatigue failure is commonly observed at the skirt-to-shell attachment weld, due to thermal gradients that develop during heating and cooling cycles. To reduce temperature differences between the coke drum shell and skirt near the attachment weld, “hot-boxes” are often implemented in skirt designs. Here is a study that investigates the effect of hot-box emissivity and height on the fatigue life of the attachment weld for skirt designs with and without keyholes.
Coke Drum Keyhole Optimization with Alloy Weld Overlay
J. Fernando, E. Falo, H. Kwok, M. Iverson, L. Wong, S. Yuen, L. Chan
To increase fatigue life of attachment welds, vertical slots and keyholes are often machined in a circumferential pattern near the top of the skirt to increase local flexibility near the weld. Here is a study that investigates a new keyhole design consisting of N06625 overlay at the keyhole locations and also conducts a sensitivity study to determine the effect of fillet size on fatigue life.
Integral Mean of Yield Concept Applied to Thermal Hotspots – Validation of a Level 2 Damage Assessment Method
H. Kwok, S. Yuen, J. Penso
A Level 2 assessment methodology is developed, which invokes the concept of integral mean of yield and a refence volume to determine the reduction of load capacity caused by hot spot damage. Here is a study that investigates the accuracy of this assessment by comparing the results of the Level 2 assessment with a Level 3 assessment (inelastic finite element analysis).