1. Accident Investigations and Case Histories
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Accident Investigations and Case Histories
University of Missouri - Rolla
ChE 258
Chemical Process Safety

2. Overview Introduction Layered Investigations Investigation summary
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Overview
Introduction
Layered Investigations
Investigation summary
Case Histories
Diagnosis (forensic engineering)
Group Presentations
Example
This presentation is intended to provide a broad introduction to the process of risk assessment and consequence analysis.
The introduction highlights the need and benefits of risk management.
The risk assessment process includes linking hazards to possible outcomes, as well as determining the magnitude and probability of potential consequences – Consequence Analysis and Risk Analysis.
Safety by Design outlines strategies for implementing risk management decisions.
Finally, the role of risk assessment in the design and operation of plants and processes is addressed.
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3. 12/6/2018
Introduction
Accident investigations and case studies provide opportunities to learn how to prevent similar accidents from occurring.
Learn from someone else’s mistakes (don’t need to put your hand in a fire to know it will be burnt).
Most companies willingly share this information to improve safety across the industry.
Flixborough, Seveso, Bhopal, Piper Alpha, Pasadena, and Channelview were major process accidents that attracted widespread media coverage. The fatalities, and in some incidents environmental damage, are unacceptable.
In each of these instances, elements of process safety management (PSM), as outlined in the OSHA standard, might have prevented the incident. The Pasadena, Texas, incident stimulated the promulgation of the OSHA standard.
These incidents continue to serve as reminders that safety in the chemical process industries cannot be taken for granted.
Note: Supplemental slides are available for each of these accidents and could be included in the lecture at this point.
The OSHA standard contains fourteen elements of Process Safety Management: 1 Employee Participation, 2 Process Safety Information, 3 Process Hazards Analysis, 4 Operating Procedures, 5 Training, 6 Contractors, 7 Prestartup Safety Review, 8 Mechanical Integrity, 9 Hot Work, 10 Management of Change, 11 Incident Investigation, 12 Emergency Planning and Response, 13 Compliance Audits, and 14 Trade Secrets.
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From Sutton, I Process Safety Management, 2nd Edition, Southwestern Books, Houston Texas
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4. Center for Chemical Process Safety (CCPS) UMR Connection
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Center for Chemical Process Safety (CCPS)
UMR Connection
Dr. Randy Freeman, UMR alumnus and Academy member (1997), has held several leadership positions in CCPS
Dr. Joseph Louvar (author of textbook), UMR alumnus and Academy Member (2000), has served in the associated organization, SACHE which is the CCPS undergraduate Education Committee

5. Accident Investigations.
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Accident Investigations.
Most modern accident investigations use the “layered” concept.
First layer - Immediate technical recommendations
Second layer - Recommendations to avoid hazard
Third layer - Recommendation to improve management system
The layered approach helps to uncover the underlying causes
Some accidents will occur, but through effective process safety management programs
(a) the frequency of occurrence can be reduced, and
(b) the magnitude of the consequences can be mitigated.
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6. Layered Accident Investigations
WHAT is the purpose of the operation involved in the accident?
WHAT equipment failed?
WHAT material leaked (exploded, decomposed, etc)?
WHICH people could have performed better?

7. Questions for Layered Accident Investigations1
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Questions for Layered Accident Investigations1
WHAT is the purpose of the operation involved in the accident?
WHY do we do this?
WHAT could we do instead?
HOW else could we do it?
WHEN else could we do it?
WHERE else could we do it?
1 from Trevor Kletz, Process Plants: A Handbook for Inherently Safer Design (Philadelphia: Taylor & Francis, 1998), p 175
Engineers and managers should appreciate the importance of proper approaches to safety and how to implement appropriate safety policies. Safety and environmental concerns are added to the requirements of industries to be financially efficient and profitable.
Techniques are now available to ensure safety, reliability, and environmental protection. These are key elements of risk management.
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8. Questions for Layered Accident Investigations1
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Questions for Layered Accident Investigations1
WHAT equipment failed?
HOW can we prevent failure or make it less likely?
HOW can we detect failure or approaching failure?
HOW can we control failure (i.e., minimize consequences)?
WHAT does this equipment do?
WHAT other equipment could we use instead?
WHAT could we do instead?
1 from Trevor Kletz, Process Plants: A Handbook for Inherently Safer Design (Philadelphia: Taylor & Francis, 1998), p 175
Engineers and managers should appreciate the importance of proper approaches to safety and how to implement appropriate safety policies. Safety and environmental concerns are added to the requirements of industries to be financially efficient and profitable.
Techniques are now available to ensure safety, reliability, and environmental protection. These are key elements of risk management.
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9. Questions for Layered Accident Investigations1
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Questions for Layered Accident Investigations1
WHAT material leaked (exploded, decomposed, etc)?
HOW can we prevent a leak (explosion, decomposition, etc.)?
HOW can we detect a leak or approaching leak (etc.)?
WHAT does this material do?
WHAT material could we use instead?
WHAT safer form could we use the original material in?
WHAT could we do instead?
1 from Trevor Kletz, Process Plants: A Handbook for Inherently Safer Design (Philadelphia: Taylor & Francis, 1998), p 175
Engineers and managers should appreciate the importance of proper approaches to safety and how to implement appropriate safety policies. Safety and environmental concerns are added to the requirements of industries to be financially efficient and profitable.
Techniques are now available to ensure safety, reliability, and environmental protection. These are key elements of risk management.
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10. Questions for Layered Accident Investigations1
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Questions for Layered Accident Investigations1
WHICH people could have performed better?
Consider people who might supervise, train, inspect, check, or design better than they did. Also consider people who might construct, operate and maintain.
WHAT could they have done better?
HOW can we help them to perform better? (Consider training, instructions, inspections, audits, etc., as well as changes to design)
1 from Trevor Kletz, Process Plants: A Handbook for Inherently Safer Design (Philadelphia: Taylor & Francis, 1998), p 175
Engineers and managers should appreciate the importance of proper approaches to safety and how to implement appropriate safety policies. Safety and environmental concerns are added to the requirements of industries to be financially efficient and profitable.
Techniques are now available to ensure safety, reliability, and environmental protection. These are key elements of risk management.
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11. Example 12-1 Pool Accident
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Example Pool Accident
A drowning accident occurred during an open swim period. Approximately 100 children, ranging between 5 and 16 years old, were in and around a pool. An older child unknowingly pushed a 5 year old into the deep water. The pool is relatively crowded, and the 5 year old slipped under the water without being noticed by others, including the lifeguard.
The following definitions are taken from the Center for Chemical Process Safety, , Guidelines for Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, NY.
A Consequence is the direct, undesirable result of an accident sequence usually involving a fire, explosion, or release of toxic material. Consequence descriptions may be qualitative or quantitative estimates of the effects of an accident in terms of factors such as health impacts, economic loss, and environmental damage.
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12. Example 12-1 Pool Accident - Layered Investigation
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Example Pool Accident - Layered Investigation
First layer:
Immediate technical recommendations
1) Paint pool depths at the pool edges.
2) Add more lifeguards.
3) Reduce the number of swimmers.
The following definitions are taken from the Center for Chemical Process Safety, , Guidelines for Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, NY.
A Consequence is the direct, undesirable result of an accident sequence usually involving a fire, explosion, or release of toxic material. Consequence descriptions may be qualitative or quantitative estimates of the effects of an accident in terms of factors such as health impacts, economic loss, and environmental damage.
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13. Example 12-1 Pool Accident - Layered Investigation
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Example Pool Accident - Layered Investigation
Second layer:
Avoiding the hazard
1) Prohibit horseplay.
2) Zone pool to keep smaller children at shallow end of pool.
3) Add swimming lessons for all age groups.
4) Give all new swimmers (especially young children) a pool orientation.
5) Add a roving lifeguard to monitor and control pool behavior.
The following definitions are taken from the Center for Chemical Process Safety, , Guidelines for Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, NY.
A Consequence is the direct, undesirable result of an accident sequence usually involving a fire, explosion, or release of toxic material. Consequence descriptions may be qualitative or quantitative estimates of the effects of an accident in terms of factors such as health impacts, economic loss, and environmental damage.
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14. Example 12-1 Pool Accident - Layered Investigation
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Example Pool Accident - Layered Investigation
Third Layer:
Improving the management system
1) Train lifeguards to alert supervision of observed potential problems.
2) Assign supervisor to make formal (documented) audits on a regular basis.
The following definitions are taken from the Center for Chemical Process Safety, , Guidelines for Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, NY.
A Consequence is the direct, undesirable result of an accident sequence usually involving a fire, explosion, or release of toxic material. Consequence descriptions may be qualitative or quantitative estimates of the effects of an accident in terms of factors such as health impacts, economic loss, and environmental damage.
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15. Formal Accident Investigation Process
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Formal Accident Investigation Process
Establish investigation team ASAP
Brief survey of information available (on site if possible)
Set objectives and delegate responsibilities
Preincident facts gathered and organized
Accident facts gathered and organized including detail examinations and photos
Research and analyses to clarify perplexing evidence
Report
The following definitions are taken from the Center for Chemical Process Safety, , Guidelines for Hazard Evaluation Procedures, American Institute of Chemical Engineers, New York, NY.
A Consequence is the direct, undesirable result of an accident sequence usually involving a fire, explosion, or release of toxic material. Consequence descriptions may be qualitative or quantitative estimates of the effects of an accident in terms of factors such as health impacts, economic loss, and environmental damage.
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16. Formal Accident Investigation Report
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Formal Accident Investigation Report
Introduction
Process description (equipment and chemistry)
Incident description
Investigation results
Discussion
Conclusions
Layered recommendations
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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17. Accident Investigation Summary
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Accident Investigation Summary
Complete formal accident investigation reports are detailed and not as useful for the average inquirer. Recently the “Investigation Summary”, a one to two page summary, has been used to spread information
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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18. 12/6/2018
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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19. 12/6/2018
Case Histories
Case histories are written descriptions of accidents, including the causes, consequences, and methods required to prevent similar events. They are written by the personnel with the hands-on experience; the ones who know and appreciate the accident and accident prevention methods
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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20. Case Histories “One learns from history or is doomed to repeat it”
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Case Histories
“One learns from history or is doomed to repeat it”
Especially true for safety; anyone working in the chemical industry can learn from case histories and avoid hazardous situations or ignore history and be involved in potentially life threatening accidents
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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21. 12/6/2018
Forensic Engineering
The chapter contains several interesting tidbits to reconstruct what happened in an accident.
Burning rates for wood
Effects on metal at different T
Pressure rise with deflagration
Pressure rise with detonation
Bursting pressures
Eq. 12-4, 12-5 Cylindrical
Eq. 12-6, 12-7 Spherical
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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22. Can work in either direction
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Vessel Failure
Can work in either direction
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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23. Group Presentation Two or three groups give presentation each day
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Group Presentation
Two or three groups give presentation each day
Can use chalk board, models, PowerPoint, overheads, etc.
If using PowerPoint, must have it preloaded and ready to run.
Please hurry to class. We are on a tight schedule and need to start ASAP or earlier!
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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24. 12/6/2018
Group Presentation
Plan on a 12 minute presentation with some questions at the end
Must be prepared to answer question (audience must be prepared to ask questions)
All group members must participate
Grading given as group
Rest of class will give a written evaluation of presentation
Participation as an evaluator is graded
Risk assessment is often a part of the hazard evaluation procedure. For example, the scope of a Hazard and Operability (HAZOP) study may include risk analysis.
Thus, in practice, the risk assessment procedure often includes:
Identification of the hazard
Analysis of the consequences
Development of quantitative estimates of probability and consequences
Identification and ranking of areas for improvement.
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25. Group Presentations
Since I need to be out of town on Monday, April 30, we will NOT have presentations that day. You can use the day to study for other classes or prepare you presentation.
On Wednesday we will have only two presentations to allow us time to work the bugs out. After that, there will be three groups present each day.

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Risk analysis will provide information about the relative ranking of hazards, that is
(a) the relative importance of systems and equipment that contribute to hazards and
(b) the potential gains to be made by improving reliability of systems and equipment.
This information provides a basis for decisions on appropriate actions.
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27. 12/6/2018
Risk analysis will provide information about the relative ranking of hazards, that is
(a) the relative importance of systems and equipment that contribute to hazards and
(b) the potential gains to be made by improving reliability of systems and equipment.
This information provides a basis for decisions on appropriate actions.
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