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Stress Engineering Services
April 2001
Stress Engineering Services for Coke Drum Health Monitoring And Reliability Improvement
April 12, 2001
Stress Engineering Services, Inc
1
Stress Engineering Services, Inc. is a multi-discipline professional engineering consulting firm headquartered in Houston, TX with offices in five major U.S. cities. SES has a staff of more than 130 mechanical, metallurgical, electrical, chemical, civil and marine engineers with an average of between 15 and 20 years of practical plant experience. SES combines this experience with the latest engineering software tools and materials engineering knowledge to provide “Health Monitoring Technology” for fixed equipment to assist plant personnel solve daily engineering problems in an effort to improve plant integrity, safety and profitability. SES personnel have extensive coke drum experience in design, analysis, monitoring, inspection, acoustic emission testing, repair and life extension of coke drums, including projects for 12 different coke drum operators on 46 drums where over 1500 coking cycles have been monitored to date with strain gages and thermocouples including AE tests on 44 drums during cyclic operation. SES now provides an unprecedented opportunity to operators of Delayed Cokers to monitor and improve the “Health” and economics of reliable coke drum operation.
SES DrumBeat
1
Stress Engineering Services
April 2001
SES Engineering Services to Owners, Operators, and Designers of Delayed Coke Drums….. ?
Health Monitoring Systems ? ? ?
?
Defect Identification and Assessment ? ?
?
?
Short and Long Term Strain Monitoring of Coke Drum Response to Daily Operation Cause and Effect of Operation on Drum Damage Integration into local DCS ?
Acoustic Emission Testing Inspection Planning & Coordination
?
?
?
April 12, 2001
? ?
Skirt Shell
?
Piping and Nozzles
Life Assessment and Extension Recommendations Metallurgical Consulting and Testing ? ?
Crack Growth Prediction Fracture Mechanics and Probabilistic Crack Growth evaluations using actual operating data ? Low Cycle Fatigue Damage Accumulation Bulge Analysis ? Severity of bulges and growth rate
Drum Design and Modeling Using Actual Operating Transients
? ? ?
Weld Repair Procedures Creep Analysis and Omega Testing
Heater Condition and Life Assessment Root Cause Failure Analysis Forensic and Litigation Support
Stress Engineering Services, Inc
2
The SES Coke Drum team is continuing to expand and develop in scope and experience. Our team of leading experts include: Richard Boswell P.E. Mechanical Design, Claudio Allevato ASNT LIII in Acoustic Emission, Jim Albert P.E. Systems Integration a nd Bobby Wright P.E., Maintenance. All with over 10 years practical coke drum experience. Other key individuals include: Mechanical
Electrical & Systems Integration
Glenn Aucoin, P.E.
Ron Morrison, P.E.
Mac Samman, Ph.D., P.E.
Bruce Maughs
Greg Garic, P.E.
Melody May
Materials, Metallurgical and Fracture Mechanics Bernie Schulze
James Buchannan
Paul Kovach, P.E.
Peter Carter, Ph.D.
Ken Riggs, Ph.D., P.E.
Doug Marriott, Ph.D.
Leo Vega
Kim Flesner, P.E. Civil Mike Effenberger, P.E. Chemical Lori Hasselbring, Ph.D., P.E.
SES DrumBeat
2
Stress Engineering Services
April 2001
SES DrumBeat Coke Drum Structural Health Monitoring Program
April 12, 2001
Stress Engineering Services, Inc
3
SES Coke Drum experience has evolved into an organized approach described as a “Health Monitoring System”. As cycles of drum operations are collected, the tools to assimilate and evaluate large volumes of data efficiently has been named SESDrumBeat. SES’s goal is to build a database so that the effects of daily operation on drum health can be assessed and understood. Once there is an improved understanding then a plan for corrective action can be implemented to Optimize drum operation versus drum reliability creating “Best Practices” for each refinery and operation.
SES DrumBeat
3
Stress Engineering Services
April 2001
Benefits of SES Program to Coke Drum Operators Record and analyze actual measurements from drum response to daily operation essential to accurately assess, predict and extend drum Health ? Achieve a better understanding of cause and effect of operation and processes on drum reliability ? Allow Operators to monitor, improve and optimize daily operation versus drum damage to create “Best Practices” ? Make and Save Operators $$$$$$$$$$$$$$$$$$ ?
April 12, 2001
Stress Engineering Services, Inc
4
SES is currently building a relational database to store and compare different operating scenarios versus drum response and damage. From this database of more than 1500 cycles of strain and temperature data, we plan to build a “Best Practices” for each location and set of drums versus different operators, procedures, feed stocks, etc. Eventually, it is thought that we can create algorithms and procedures from which you can control drum operation.
SES DrumBeat
4
Stress Engineering Services
April 2001
What SES does to improve Coke Drum Economics and Reliability: 1.
2.
3. 4.
5.
6.
Install High Temperature Strain Gages, Thermocouples and Intrinsically safe system to monitor Shell and Skirt Regions Hook Intrinsically Safe Logger into Local DCS or Directly to SES Retrieve Strain and Process Data routinely Evaluate trends of recorded strain and damage versus daily operation: Cause and Effect Provide Prompt Feedback and Analysis to Operators to allow for improvement Provide Engineering Analysis and Support to Extend Life April 12, 2001
Stress Engineering Services, Inc
5
Coke Drum Operators can improve the reliability of their existing and new coke drums by having SES install strain gages to monitor the vessels structural performance versus daily operation. Both the cylindrical shell and the supporting skirt can be protected through improved knowledge of consequence resulting from operation of the drum. SES can tie directly into local DCS making it easier for the operator to evaluate, control and improve operation. Transient measurements of actual operating practices can be used as loading conditions for Finite Element Models to calculate peak stress for fatigue calculations. This will provide operators with ideal transients and control parameters for both the shell and skirt regions. Stress ranges measured for each cycle are used to provide a probabilistic summation of fatigue damage. This information is used to assess and predict the progression of cracking and to evaluate the effects of modified operating practices.
SES DrumBeat
5
Stress Engineering Services
April 2001
Temperature distribution soon after Switching
April 12, 2001
Stress Engineering Services, Inc
6
SES has been involved with the design and modeling of many new a nd existing coke drums expanding our knowledge and experience to compare and evaluate different operating procedures and transients. From this experience SES can advise on practices and transients to minimize damage and cracking to improve drum life.
SES DrumBeat
6
Stress Engineering Services
April 2001
Skirt is forced outward during Fill transient
April 12, 2001
Stress Engineering Services, Inc
7
SES uses the latest FEA modeling software and analysis techniques to evaluate “actual” measured strain and temperature response to operation. Experience has shown that design assumptions and reality are often different, resulting in an overestimated design life. This real data improves SES’s understanding of drum stresses versus damage accumulation and the resulting impact of drum life.
SES DrumBeat
7
Stress Engineering Services
April 2001
High Temperature Strain Gage with Intrinsically Safe Instrumentation
April 12, 2001
Stress Engineering Services, Inc
8
SES has designed and built intrinsically safe boxes for the harsh coke drum environment to house our “Health Monitoring System”. One of the first SES systems was built and installed in 1997 and is still working today. SES routinely installs over 4000 strain gages per year which has improved our gage installation practices so that we have gages reliably lasting for a 1 year or more.
SES DrumBeat
8
Stress Engineering Services
April 2001
Structural Health Monitoring Data Processing Tasks ?
Review Recorded Data for – High Temperature Strain Gages – Thermocouples
? ? ? ? ? ?
Correct Readings for Temperature Error Calculate each pair for Bi-Axial Principal Stress and Stress Intensity Determine Stress Range each Cycle Compile Histograms and Damage Accumulation Evaluate Process Cause and Structural Effect Compare Different Operating Procedures for resulting Structural Damage
April 12, 2001
Stress Engineering Services, Inc
9
These are the fundamental procedures used to process strain gage measurements into cumulative damage while determining which aspects of the operations adversely affect drum reliability and could possibly be modified to enhance the life of the drum and minimize failures and lost profit.
SES DrumBeat
9
Stress Engineering Services
April 2001
Measured Stress is caused by several conditions ?
Measured Stress is due to – Pressure – Gravity and Hydrostatic – Thermal gradients – Flattening of Bulges – Solid Coke Interference – Solid Coke Friction – Ring Bending from Bulge Diameters
April 12, 2001
?
Stress is composed of – Average stress in wall : Membrane – Bending Stress inside/outside wall – Secondary Stress for Geometric Equilibrium – Peak Stress at defects, undercuts, weld caps, radius transition
?
Stress measurement on OD is independent of source of stress
Stress Engineering Services, Inc
10
By measuring actual drum stress at strategic locations, we can estimate the rate of damage accumulation from low cycle fatigue for the skirt and shell. There have been many discussions over the past decade as to the actual cause of the fatigue stress and bulge formation. These discussions focus on the role of the hardened coke inside the drum, and how steam and water flow through it to cool the hot mass: streng th and permeability are functions of feedstock and process batch procedures. Consequently, the result is difficult to predict from analysis a lone. Measurement and interpretation is essential for low cycle fatigue and fracture mechanics assessments. In other words, high stress and cracking happens in all drums sooner or later, the question is can we learn to improve the way we operate the drums to reduce the rate of damage.
SES DrumBeat
10
Stress Engineering Services
April 2001
Typical Coking Cycle for Process and Stress
April 12, 2001
Stress Engineering Services, Inc
11
Question: What effect do operators have on drum reliability? The Coke Drum Cycle 1. Initial Steam pressure check for leaks. 2. Pre-warm using overhead vapor from adjacent drum into top of drum. 3. Switch and begin filling with hot oil into bottom of drum. 4. Continue filling drum as valuable vapor is recovered and residual solidify leaving a series of flow channels similar to the trunk and branches of a tree. 5. Switch out of the drum. 6. Begin a steam purge to remove remaining vapors. 7. Begin water flow into bottom of drum. 8. Continue water until solid mass is cool and vapor temperature is low. 9. Drain water. 10. Begin drilling pilot hole from top. 11. When blade bit reaches bottom, begin hydraulic cutting of the solid coke from the bottom up, retracting the drill stem into the derrick. 12. Collect solidified coke and ship to customers.
SES DrumBeat
11
Stress Engineering Services
April 2001
Plot Stress Range for each Cycle
April 12, 2001
Stress Engineering Services, Inc
12
High stress happens in nearly all drums sooner or later, the consequence is a ratcheting fatigue and crack growth propagation. What are you doing as an operator to damage the drums that you can change or improve? SES’s goal is to help you understand what you are doing or not doing that hurts you and provide recommendations to improve. Stress range (max to min) varies from cycle to cycle, Some are higher than yield strength of the steel, and others are much lower. This is likely caused by variations in the flow channels developed near the inside wall due to operation and process changes. Local water/steam channels cause local relative cooling placing the shell in local hoop and axial tensions. The stress range at the skirt is dependent upon the skirt bending stress created during Fill (which pushes the skirt outward) and Quench (which pulls the hot top part of the skirt back inward). What is good for the skirt area may be bad for the shell and vice versa.
SES DrumBeat
12
Stress Engineering Services
April 2001
Histogram of Stress Ranges describes how often a stress happens
April 12, 2001
Stress Engineering Services, Inc
13
Stress range (max to min) varies from cycle to cycle, Some are higher than yield strength of the steel, and others are much lower. The variations in cycle performance are described in a histogram showing frequency of occurrence in a form described with Weibull parameters traditionally used for mechanical reliability. If eno ugh cycles are recorded, the “Goodness of Fit” is very high and the accuracy of the assessment improves.
SES DrumBeat
13
Stress Engineering Services
April 2001
Calculate Fatigue Damage for each Stress Component and Determine Cycle Life
April 12, 2001
Stress Engineering Services, Inc
14
The Low Cycle Fatigue can be described in a Miner’s Rule summation of the damage created from the stress range experienced. For any given stress range, an allowable cyclic life can be calculated using functions as described in ASME Section VIII, Div 3 for fatigue. The actual number of cycles used is compared to the number allowed for each stress range, and this is the Unit Damage Ratio. When the summation of all Unit Damage Ratios equals 1.0 (unity), the life is consumed and cracks will need to be repaired. This leads to a projected number of cycles that a specific histogram could operate in. This approximates a random Monte Carlo simulation of the cycle life. Note: One extremely severe cycle of over 100,000 psi can reduce cycle life by 800-1000 cycles or 2 -3 years depending on the drum.
SES DrumBeat
14
Stress Engineering Services
April 2001
Histogram of Stress Ranges and Damage for Low Cycle Fatigue
April 12, 2001
Stress Engineering Services, Inc
15
Some cycles consume a large percentage of the allowable damage as shown in this chart. Many lower ranged cycles combined together do not equal the damage created in a single high stress cycle. Changes to drum operation are intended to not only “move the histogram to the left” shifting to a lower stressed operation, b ut are also intended to reduce the likelihood of the “bell ringing bingos” that create the most damage.
SES DrumBeat
15
Stress Engineering Services
April 2001
Integration With SES “DrumBeat” Analysis On-line Sensors
DCS Information
Critical Control Factors
SES Operator Logs
Observations Outputs
Operational Intelligence to reduce fatigue damage Remaining Life Assessments April 12, 2001
Fatigue crack Growth Prediction Low Cycle Fatigue Damage Accumulation
Stress Engineering Services, Inc
16
SES is building a relational database of most parameters which may affect drum reliability. SES routinely measures mechanical response and is working to tie damage directly to daily operation. The challenge is to gain more information about how operators, processes and feed stocks affect the drums and what to do about it. It is relatively easy for SES to measure strain, temperature, acoustic emission signals and process information. It is more difficult to include the effect of critical control factors like, people, operations, processes due to changes in feed stocks and adherence to or not adhering to procedures. However, there may be greater benefit in understanding and improving operating practices and education of personnel eve n though it is probably the most difficult to achieve.
SES DrumBeat
16
Stress Engineering Services
April 2001
The Future DrumBeat…. An Automated and On Site Structural Health Monitoring System for Improved Reliability of Delayed Coke Drums
April 12, 2001
Stress Engineering Services, Inc
17
SES resources are easily reviewed on the World Wide Web! Please visit and contact us at our web site or give us a phone call. Stress Engineering Services 13800 Westfair East Houston, Texas 77041 281-955-2900 281-955-2638 fax www.stress.com
SES DrumBeat
17
Stress Engineering Services
April 2001
SES Drumbeat Information Links ?
Remaining Life Evaluations of Coke Drums (pdf)
?
Assessing Structural Integrity of Coke Drums (pdf)
?
SES DrumBeat PowerPoint notes (pdf)
?
Stress Engineering Services at www.stress.com
April 12, 2001
Stress Engineering Services, Inc
18
Here are some important documents you may be interested in relating to SES’s coke drum work.
SES DrumBeat
18
Stress Engineering Services
April 2001
SES DrumBeat Coke Drum Structural Health Monitoring System ?
?
?
SES DrumBeat is a collection of procedures for processing strain gage, thermocouple, and process data measured on a coke drum. SES DrumBeat is becoming an automated software to routinely manage large volumes of data in real time for cyclic damage accumulation. SES DrumBeat will become an on-site system available to provide clients with continuous update on coke drum operation.
?
SESDrumBeat.com is under development to provide clients a secure access to their results.
?
CokeDrum.com is under development to provide clients with information about SES and coke drum services. Stress.com is the Stress Engineering Services web site for complete introduction to our upstream and downstream engineering services.
?
April 12, 2001
Stress Engineering Services, Inc
19
SES resources are easily reviewed on the World Wide Web! Please visit and contact us at our web site or give us a phone call. Stress Engineering Services 13800 Westfair East Houston, Texas 77041 281-955-2900 281-955-2638 fax www.stress.com
SES DrumBeat
19
Stress Engineering Services
April 2001
Stress Engineering Services, Inc 13800 Westfair East Houston, Texas 77041 281--955 281 955--2900 www.stress.com This CD is the property of Stress Engineering Services Inc. The information herein is confidential and is issued on the understanding that no part thereof shall be copied or communicated to a third party without authorization in writing from Stress Engineering Services Inc. April 12, 2001
SES DrumBeat
Stress Engineering Services, Inc
20
20
April 2001
Stress Engineering Services for Coke Drum Health Monitoring And Reliability Improvement
April 12, 2001
Stress Engineering Services, Inc
1
Stress Engineering Services, Inc. is a multi-discipline professional engineering consulting firm headquartered in Houston, TX with offices in five major U.S. cities. SES has a staff of more than 130 mechanical, metallurgical, electrical, chemical, civil and marine engineers with an average of between 15 and 20 years of practical plant experience. SES combines this experience with the latest engineering software tools and materials engineering knowledge to provide “Health Monitoring Technology” for fixed equipment to assist plant personnel solve daily engineering problems in an effort to improve plant integrity, safety and profitability. SES personnel have extensive coke drum experience in design, analysis, monitoring, inspection, acoustic emission testing, repair and life extension of coke drums, including projects for 12 different coke drum operators on 46 drums where over 1500 coking cycles have been monitored to date with strain gages and thermocouples including AE tests on 44 drums during cyclic operation. SES now provides an unprecedented opportunity to operators of Delayed Cokers to monitor and improve the “Health” and economics of reliable coke drum operation.
SES DrumBeat
1
Stress Engineering Services
April 2001
SES Engineering Services to Owners, Operators, and Designers of Delayed Coke Drums….. ?
Health Monitoring Systems ? ? ?
?
Defect Identification and Assessment ? ?
?
?
Short and Long Term Strain Monitoring of Coke Drum Response to Daily Operation Cause and Effect of Operation on Drum Damage Integration into local DCS ?
Acoustic Emission Testing Inspection Planning & Coordination
?
?
?
April 12, 2001
? ?
Skirt Shell
?
Piping and Nozzles
Life Assessment and Extension Recommendations Metallurgical Consulting and Testing ? ?
Crack Growth Prediction Fracture Mechanics and Probabilistic Crack Growth evaluations using actual operating data ? Low Cycle Fatigue Damage Accumulation Bulge Analysis ? Severity of bulges and growth rate
Drum Design and Modeling Using Actual Operating Transients
? ? ?
Weld Repair Procedures Creep Analysis and Omega Testing
Heater Condition and Life Assessment Root Cause Failure Analysis Forensic and Litigation Support
Stress Engineering Services, Inc
2
The SES Coke Drum team is continuing to expand and develop in scope and experience. Our team of leading experts include: Richard Boswell P.E. Mechanical Design, Claudio Allevato ASNT LIII in Acoustic Emission, Jim Albert P.E. Systems Integration a nd Bobby Wright P.E., Maintenance. All with over 10 years practical coke drum experience. Other key individuals include: Mechanical
Electrical & Systems Integration
Glenn Aucoin, P.E.
Ron Morrison, P.E.
Mac Samman, Ph.D., P.E.
Bruce Maughs
Greg Garic, P.E.
Melody May
Materials, Metallurgical and Fracture Mechanics Bernie Schulze
James Buchannan
Paul Kovach, P.E.
Peter Carter, Ph.D.
Ken Riggs, Ph.D., P.E.
Doug Marriott, Ph.D.
Leo Vega
Kim Flesner, P.E. Civil Mike Effenberger, P.E. Chemical Lori Hasselbring, Ph.D., P.E.
SES DrumBeat
2
Stress Engineering Services
April 2001
SES DrumBeat Coke Drum Structural Health Monitoring Program
April 12, 2001
Stress Engineering Services, Inc
3
SES Coke Drum experience has evolved into an organized approach described as a “Health Monitoring System”. As cycles of drum operations are collected, the tools to assimilate and evaluate large volumes of data efficiently has been named SESDrumBeat. SES’s goal is to build a database so that the effects of daily operation on drum health can be assessed and understood. Once there is an improved understanding then a plan for corrective action can be implemented to Optimize drum operation versus drum reliability creating “Best Practices” for each refinery and operation.
SES DrumBeat
3
Stress Engineering Services
April 2001
Benefits of SES Program to Coke Drum Operators Record and analyze actual measurements from drum response to daily operation essential to accurately assess, predict and extend drum Health ? Achieve a better understanding of cause and effect of operation and processes on drum reliability ? Allow Operators to monitor, improve and optimize daily operation versus drum damage to create “Best Practices” ? Make and Save Operators $$$$$$$$$$$$$$$$$$ ?
April 12, 2001
Stress Engineering Services, Inc
4
SES is currently building a relational database to store and compare different operating scenarios versus drum response and damage. From this database of more than 1500 cycles of strain and temperature data, we plan to build a “Best Practices” for each location and set of drums versus different operators, procedures, feed stocks, etc. Eventually, it is thought that we can create algorithms and procedures from which you can control drum operation.
SES DrumBeat
4
Stress Engineering Services
April 2001
What SES does to improve Coke Drum Economics and Reliability: 1.
2.
3. 4.
5.
6.
Install High Temperature Strain Gages, Thermocouples and Intrinsically safe system to monitor Shell and Skirt Regions Hook Intrinsically Safe Logger into Local DCS or Directly to SES Retrieve Strain and Process Data routinely Evaluate trends of recorded strain and damage versus daily operation: Cause and Effect Provide Prompt Feedback and Analysis to Operators to allow for improvement Provide Engineering Analysis and Support to Extend Life April 12, 2001
Stress Engineering Services, Inc
5
Coke Drum Operators can improve the reliability of their existing and new coke drums by having SES install strain gages to monitor the vessels structural performance versus daily operation. Both the cylindrical shell and the supporting skirt can be protected through improved knowledge of consequence resulting from operation of the drum. SES can tie directly into local DCS making it easier for the operator to evaluate, control and improve operation. Transient measurements of actual operating practices can be used as loading conditions for Finite Element Models to calculate peak stress for fatigue calculations. This will provide operators with ideal transients and control parameters for both the shell and skirt regions. Stress ranges measured for each cycle are used to provide a probabilistic summation of fatigue damage. This information is used to assess and predict the progression of cracking and to evaluate the effects of modified operating practices.
SES DrumBeat
5
Stress Engineering Services
April 2001
Temperature distribution soon after Switching
April 12, 2001
Stress Engineering Services, Inc
6
SES has been involved with the design and modeling of many new a nd existing coke drums expanding our knowledge and experience to compare and evaluate different operating procedures and transients. From this experience SES can advise on practices and transients to minimize damage and cracking to improve drum life.
SES DrumBeat
6
Stress Engineering Services
April 2001
Skirt is forced outward during Fill transient
April 12, 2001
Stress Engineering Services, Inc
7
SES uses the latest FEA modeling software and analysis techniques to evaluate “actual” measured strain and temperature response to operation. Experience has shown that design assumptions and reality are often different, resulting in an overestimated design life. This real data improves SES’s understanding of drum stresses versus damage accumulation and the resulting impact of drum life.
SES DrumBeat
7
Stress Engineering Services
April 2001
High Temperature Strain Gage with Intrinsically Safe Instrumentation
April 12, 2001
Stress Engineering Services, Inc
8
SES has designed and built intrinsically safe boxes for the harsh coke drum environment to house our “Health Monitoring System”. One of the first SES systems was built and installed in 1997 and is still working today. SES routinely installs over 4000 strain gages per year which has improved our gage installation practices so that we have gages reliably lasting for a 1 year or more.
SES DrumBeat
8
Stress Engineering Services
April 2001
Structural Health Monitoring Data Processing Tasks ?
Review Recorded Data for – High Temperature Strain Gages – Thermocouples
? ? ? ? ? ?
Correct Readings for Temperature Error Calculate each pair for Bi-Axial Principal Stress and Stress Intensity Determine Stress Range each Cycle Compile Histograms and Damage Accumulation Evaluate Process Cause and Structural Effect Compare Different Operating Procedures for resulting Structural Damage
April 12, 2001
Stress Engineering Services, Inc
9
These are the fundamental procedures used to process strain gage measurements into cumulative damage while determining which aspects of the operations adversely affect drum reliability and could possibly be modified to enhance the life of the drum and minimize failures and lost profit.
SES DrumBeat
9
Stress Engineering Services
April 2001
Measured Stress is caused by several conditions ?
Measured Stress is due to – Pressure – Gravity and Hydrostatic – Thermal gradients – Flattening of Bulges – Solid Coke Interference – Solid Coke Friction – Ring Bending from Bulge Diameters
April 12, 2001
?
Stress is composed of – Average stress in wall : Membrane – Bending Stress inside/outside wall – Secondary Stress for Geometric Equilibrium – Peak Stress at defects, undercuts, weld caps, radius transition
?
Stress measurement on OD is independent of source of stress
Stress Engineering Services, Inc
10
By measuring actual drum stress at strategic locations, we can estimate the rate of damage accumulation from low cycle fatigue for the skirt and shell. There have been many discussions over the past decade as to the actual cause of the fatigue stress and bulge formation. These discussions focus on the role of the hardened coke inside the drum, and how steam and water flow through it to cool the hot mass: streng th and permeability are functions of feedstock and process batch procedures. Consequently, the result is difficult to predict from analysis a lone. Measurement and interpretation is essential for low cycle fatigue and fracture mechanics assessments. In other words, high stress and cracking happens in all drums sooner or later, the question is can we learn to improve the way we operate the drums to reduce the rate of damage.
SES DrumBeat
10
Stress Engineering Services
April 2001
Typical Coking Cycle for Process and Stress
April 12, 2001
Stress Engineering Services, Inc
11
Question: What effect do operators have on drum reliability? The Coke Drum Cycle 1. Initial Steam pressure check for leaks. 2. Pre-warm using overhead vapor from adjacent drum into top of drum. 3. Switch and begin filling with hot oil into bottom of drum. 4. Continue filling drum as valuable vapor is recovered and residual solidify leaving a series of flow channels similar to the trunk and branches of a tree. 5. Switch out of the drum. 6. Begin a steam purge to remove remaining vapors. 7. Begin water flow into bottom of drum. 8. Continue water until solid mass is cool and vapor temperature is low. 9. Drain water. 10. Begin drilling pilot hole from top. 11. When blade bit reaches bottom, begin hydraulic cutting of the solid coke from the bottom up, retracting the drill stem into the derrick. 12. Collect solidified coke and ship to customers.
SES DrumBeat
11
Stress Engineering Services
April 2001
Plot Stress Range for each Cycle
April 12, 2001
Stress Engineering Services, Inc
12
High stress happens in nearly all drums sooner or later, the consequence is a ratcheting fatigue and crack growth propagation. What are you doing as an operator to damage the drums that you can change or improve? SES’s goal is to help you understand what you are doing or not doing that hurts you and provide recommendations to improve. Stress range (max to min) varies from cycle to cycle, Some are higher than yield strength of the steel, and others are much lower. This is likely caused by variations in the flow channels developed near the inside wall due to operation and process changes. Local water/steam channels cause local relative cooling placing the shell in local hoop and axial tensions. The stress range at the skirt is dependent upon the skirt bending stress created during Fill (which pushes the skirt outward) and Quench (which pulls the hot top part of the skirt back inward). What is good for the skirt area may be bad for the shell and vice versa.
SES DrumBeat
12
Stress Engineering Services
April 2001
Histogram of Stress Ranges describes how often a stress happens
April 12, 2001
Stress Engineering Services, Inc
13
Stress range (max to min) varies from cycle to cycle, Some are higher than yield strength of the steel, and others are much lower. The variations in cycle performance are described in a histogram showing frequency of occurrence in a form described with Weibull parameters traditionally used for mechanical reliability. If eno ugh cycles are recorded, the “Goodness of Fit” is very high and the accuracy of the assessment improves.
SES DrumBeat
13
Stress Engineering Services
April 2001
Calculate Fatigue Damage for each Stress Component and Determine Cycle Life
April 12, 2001
Stress Engineering Services, Inc
14
The Low Cycle Fatigue can be described in a Miner’s Rule summation of the damage created from the stress range experienced. For any given stress range, an allowable cyclic life can be calculated using functions as described in ASME Section VIII, Div 3 for fatigue. The actual number of cycles used is compared to the number allowed for each stress range, and this is the Unit Damage Ratio. When the summation of all Unit Damage Ratios equals 1.0 (unity), the life is consumed and cracks will need to be repaired. This leads to a projected number of cycles that a specific histogram could operate in. This approximates a random Monte Carlo simulation of the cycle life. Note: One extremely severe cycle of over 100,000 psi can reduce cycle life by 800-1000 cycles or 2 -3 years depending on the drum.
SES DrumBeat
14
Stress Engineering Services
April 2001
Histogram of Stress Ranges and Damage for Low Cycle Fatigue
April 12, 2001
Stress Engineering Services, Inc
15
Some cycles consume a large percentage of the allowable damage as shown in this chart. Many lower ranged cycles combined together do not equal the damage created in a single high stress cycle. Changes to drum operation are intended to not only “move the histogram to the left” shifting to a lower stressed operation, b ut are also intended to reduce the likelihood of the “bell ringing bingos” that create the most damage.
SES DrumBeat
15
Stress Engineering Services
April 2001
Integration With SES “DrumBeat” Analysis On-line Sensors
DCS Information
Critical Control Factors
SES Operator Logs
Observations Outputs
Operational Intelligence to reduce fatigue damage Remaining Life Assessments April 12, 2001
Fatigue crack Growth Prediction Low Cycle Fatigue Damage Accumulation
Stress Engineering Services, Inc
16
SES is building a relational database of most parameters which may affect drum reliability. SES routinely measures mechanical response and is working to tie damage directly to daily operation. The challenge is to gain more information about how operators, processes and feed stocks affect the drums and what to do about it. It is relatively easy for SES to measure strain, temperature, acoustic emission signals and process information. It is more difficult to include the effect of critical control factors like, people, operations, processes due to changes in feed stocks and adherence to or not adhering to procedures. However, there may be greater benefit in understanding and improving operating practices and education of personnel eve n though it is probably the most difficult to achieve.
SES DrumBeat
16
Stress Engineering Services
April 2001
The Future DrumBeat…. An Automated and On Site Structural Health Monitoring System for Improved Reliability of Delayed Coke Drums
April 12, 2001
Stress Engineering Services, Inc
17
SES resources are easily reviewed on the World Wide Web! Please visit and contact us at our web site or give us a phone call. Stress Engineering Services 13800 Westfair East Houston, Texas 77041 281-955-2900 281-955-2638 fax www.stress.com
SES DrumBeat
17
Stress Engineering Services
April 2001
SES Drumbeat Information Links ?
Remaining Life Evaluations of Coke Drums (pdf)
?
Assessing Structural Integrity of Coke Drums (pdf)
?
SES DrumBeat PowerPoint notes (pdf)
?
Stress Engineering Services at www.stress.com
April 12, 2001
Stress Engineering Services, Inc
18
Here are some important documents you may be interested in relating to SES’s coke drum work.
SES DrumBeat
18
Stress Engineering Services
April 2001
SES DrumBeat Coke Drum Structural Health Monitoring System ?
?
?
SES DrumBeat is a collection of procedures for processing strain gage, thermocouple, and process data measured on a coke drum. SES DrumBeat is becoming an automated software to routinely manage large volumes of data in real time for cyclic damage accumulation. SES DrumBeat will become an on-site system available to provide clients with continuous update on coke drum operation.
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SESDrumBeat.com is under development to provide clients a secure access to their results.
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CokeDrum.com is under development to provide clients with information about SES and coke drum services. Stress.com is the Stress Engineering Services web site for complete introduction to our upstream and downstream engineering services.
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April 12, 2001
Stress Engineering Services, Inc
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SES resources are easily reviewed on the World Wide Web! Please visit and contact us at our web site or give us a phone call. Stress Engineering Services 13800 Westfair East Houston, Texas 77041 281-955-2900 281-955-2638 fax www.stress.com
SES DrumBeat
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Stress Engineering Services
April 2001
Stress Engineering Services, Inc 13800 Westfair East Houston, Texas 77041 281--955 281 955--2900 www.stress.com This CD is the property of Stress Engineering Services Inc. The information herein is confidential and is issued on the understanding that no part thereof shall be copied or communicated to a third party without authorization in writing from Stress Engineering Services Inc. April 12, 2001
SES DrumBeat
Stress Engineering Services, Inc
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