Tripod incident investigations
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Transcript of Tripod incident investigations
Tripod Incident Investigations
The tripod method is a way of conducting incident analysis. It is mostly used for high risk, complex incidents, since it is a very extensive and detailed method. Training is highly recommended when using the tripod method.
The Three Step Principle of Use!
A Tripod Beta tree is built in three steps. The first step is to ask the question: ‘what happened?’. All the events that happened in the incident are listed as a chain of events. The next step is to identify the barriers that failed to stop this chain of events. The question that is asked in this step is: ‘How did it happen?’. When all the events and the failed barriers in between are identified, the reason for failure of these barriers is analyzed. The last question for this step is: ‘Why did it happen?’. For each of the failed barriers a causation path is identified.
One of the most important aspects of Tripod Beta is that it assumes that human behavior resulting in failures is influenced (determined) by latent failures in the context of an organization. If these latent failures are not addressed, only symptoms are being tackled. This is why a human behavior theory is a key element of Tripod Beta.
What is an Incident? A sequence of logically and chronologically
related deviating events involving an incident that results in injury to personnel or damage to the environment or material assets.
Three phases in Incident investigation
Collecting evidence and facts
• Human or testamentary evidence Human or testamentary evidence includes witness statements and
observations.
• Physical evidence Physical evidence is matter related to the Incident (e.g. equipment,
parts, debris, hardware, and other physical items).
• Documentary evidence Documentary evidence includes paper and electronic information,
such as records, reports, procedures, and documentation.
Analysis of evidence and facts
• What happened where and when?• Why did it happen?
types of causal factors: Direct cause Contributing causes Root causes
Methods for Incident investigation
• TRIPOD• Barrier analysis • Change analysis. • Events and causal factors analysis
OTHER Incident INVESTIGATION METHODS
• Fault tree analysis• Root cause analysis • Events and causal factors charting (ECFC) • Event tree analysis• MORT • Systematic Cause Analysis Technique (SCAT) • (Sequential timed events plotting) • MTO-analysis • Incident Analysis and Barrier Function (AEB) Method • Acci-map
TRIPOD _BETA
DefinitionAdvantages Phases:
• Diagram Tripod_beta• Hazard conduct• Incident causation model
Diagram Tripod_betaElements
• Event• Hazard• Target
Hazard conduct
Swiss cheese model
- Organisations manage risk using ‘barriers’
- Barriers – use of equipment, design of plant (redundancy, overflows, etc.), following rules, procedures, standards…
…… usually barriers are people doing a job
- Barriers are ‘functions’
Why incidents happen (1)
Why incidents happen (2)
Incidents happen when barriers fail.
Why do barriers fail? The Tripod causation path
An organisation
Error / violation promoting conditions
That influences the personCreates To take action or inaction
That causes barriers to fail
That result in
Incidents, incidents and business upsets
• SMS• Leadership• Culture
• Performance influencing factors (PIFs)
- Competence- Fatigue- Environment- Supervision- Task- Etc.
• Human action or inaction• slips, lapses,
mistakes, violations
Underlying causes
Immediate causes
Preconditions
Knowledge.energyinst.org
Why do barriers fail? The Tripod causation path
An organisation
Error / violation promoting conditions
That influences the personCreates To take action or inaction
That causes barriers to fail
That result in
Incidents, incidents and business upsets
• SMS• Leadership• Culture
• Performance influencing factors (PIFs)
- Competence- Fatigue- Environment- Supervision- Task- Etc.
• Human action or inaction• slips, lapses,
mistakes, violations
Underlying causes
Immediate causes
Preconditions
Types of human failure – the ‘immediate cause’
Intended actions Unintended actions
Violations Mistake SlipLapse
Errors
Human factors – the ‘PIFs’ (two similar models)
Job Individual
Organisation
Task complexity.Facilities.Environment
Culture, leadership, supervisors, rules and procedures
Personality, psychology, height, weight, competency, fatigue
1. Organisational change (and transition management) 2. Staffing arrangements and workload3. Training and competence (and supervision)4. Fatigue (from shiftwork and overtime)5. Human factors in design:
(a) General(b) Alarm handling(c) Control rooms(d) Ergonomics – design of interfaces(e) Ergonomics – health ergonomics
6. Procedures (especially safety critical procedures)7. Organisational culture (and development)8. Communications and interfaces9. Integration of human factors into risk assessment and investigations (including
Safety Management Systems)10. Managing human failure (including maintenance error)
Human factors Top 10 issues
EventFailed barrier
EventEvent - Agent
EventObject
Agent
Object
Failed barrierFailed barrier
Immediate causePreconditionUnderlying
cause
Investigation (e.g. Tripod Beta)