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29 Cards in this Set
- Front
- Back
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Benefits of Layers of Protection Analysis (LOPA) |
-Help provide the basis for a clear, functional specification for IPLs -Reduces subjectivity in the decision making process -Assists in identifying which safeguards should be emphasized during training, daily operations and maintenance -Facilitates the determination of more precise cause-consequence pairs - Other scenarios or issues may be revealed -Takes less time than a QRA |
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Types of Layers in LOPA |
-Protection Layers: Basic controls and monitoring, prevention layer, mitigation layer, plant emergency response, and community emergency response -Independent Protection Layers: Device, system, or action that acts to prevent a scenario from proceeding to its undesired consequence, regardless of the initiating event, action or failure of any other protection layer associated with the scenario, or any other element of the scenario. Not all safeguards are IPLs but all IPLs are safeguards. |
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Limitations of Preliminary Hazard Analysis (PHA) |
- Fails to identify risks of combined hazards or co-existing system failure modes. -Insufficient/inappropriate targets or operational phases chosen results in flawed evaluation. |
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Advantages of Preliminary Hazard Analysis
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-log of primary system hazards and their corresponding risks -logically based evaluation of system's weak points -decision making info for management on allocation of resources -quick review and delineation of most significant system risks. |
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Steps to do a PHA
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- identify resources to be protected; targets
- identify and observe acceptable levels of risk - define analysis scope; system boundaries and operating phases. - state all assumptions -detect and confirm all hazards to the system |
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Limitations of Fault Tree Analysis (FTA)
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–Can only address one undesirable condition at a time –for probabilistic assessment may not fit or run on conventional PC-based software. –Generation of accurate probabilistic assessment may require significant time and resources. –Events or conditions under the same logic gate must be independent of each other. –Flawed if common causes have not been identified. –Events or conditions at any level must be independent and immediate contributors to the next level event or condition. –Failure rate of each initiator must be constant and predictable. –Not accurate unless all significant contributors of faults or failures are anticipated. |
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What do Performance Shaping Factors do?
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-effect performance in a system -Influence Error Rates -internal: training and skill, practice and experience, or stress -External: actions by supervisors, plant policies, physical requirements -psychological: high tool speed, heavy task load, or threats such as loss of job -physiological: Hunger or thirst, Pain or Discomfort,or fatigue |
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Why do vapor cloud dispersion modeling?
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· It determines the zone of vulnerability · It determines the extent of the vapor cloud · It determines if its flammable or toxic at that given point |
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Limitations of Failure Modes and Effects Analysis (FMEA)
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-Not efficient for identifying combinations of equipment failures
-Human errors not generally examined. Effects of miss-operation can be described by an equipment failure mode or by the causes of a failure -External events not easily addressed |
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Phases in Systems Life Cycle
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-Conceptual Trade Studies
-Concept Definition -Design and Development -Fabrication integration, test and evaluation -Operations -Decommissioning/disposal/recycle |
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What is Event Tree Analysis (ETA)
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-a forward or bottom up symbolic logic modeling technique generated in both success and failure domains.
-The system or initiating challenge may be a failure or fault, an undesirable event or a normal system operation. |
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What is Fault Tree Analysis (FTA) and when is it applicable?
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Tool to analyze defined hazard anddetermine exactly how it manifestation is possible and to determine how likelyit is to occur – a quantitative method.
Trace failure pathways from apre-determined, undesirable condition or event – Called the “Top Event”. |
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What is a risk assessment matrix?
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-tool to conduct subjective risk assessments -expressed in severity and probability - Pre-determinedguide to evaluate identified hazards |
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What are energy sources in Energy Flow and Barrier Analysis (EFBA)?
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o Electrical
o Mechanical o Chemical o Radiation |
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Year of BP Amoco refinery explosion?
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2005 |
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What information is on a safety data sheet?
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-comprehensive information about a substance or mixture for use in workplace chemical management |
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Path Set |
A group of fault tree initiators that if none of them occurs, will guarantee that the TOP event cannot occur. |
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Wha is the Technique for Human Error Rate Prediction (THERP) method?
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-method for predicting human error rates and evaluating the degradation of a human-machine system likely to be caused by human errors in association with factors such as equipment reliability, procedures, and other factors. -uses performance-shaping factors to make judgments about particular situations. |
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Qualities of a risk communicator.
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-Be a good listener
-Have common sense -Have real sincerity -Be sensitive to the audience |
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Know what Piper Alpha did and about the incident.
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-Technicians removed and checked safety valves which were essential in preventing dangerous build-up of liquid gas. -Forgot to replace one of the valves -a technician pressed a start button for the liquid gas pumps and the world‘s most expensive oil rig accident was set in motion. -The world’s worst off-shore oil disaster -167 workers died -Cost $3.4 Billion |
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Know about deviations in HAZOPS
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-Guide Words: no, more, less, as well as, part of, reverse, other than -Parameters: flow, pressure, temperature, composition, level, addition, cooling, location Ex. "no cooling": loss of cooling. "less temperature": lower temperature |
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Why use Cause and Effect Analysis?
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-Focusing on causes not symptoms capturing the collective knowledge and experience of a group -Provides a picture of why an effect is happening -Establishing a sound basis for further data gathering and action -can also be used to identify all of the areas that need to be tackled to generate a positive effect |
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Know about the risk contours.
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-useful to provide guides, convention and acceptance limits for risk assessment. -Risk should be evaluated for worst credible case, not worst conceivable case. -Failure to assume credible may result in an optimistic analysis and will result in a non-viable analysis |
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Advantages of Risk Assessment Matrix |
-Useful for engineering
-treats relationship between severity and probability in assessing risk for a hazard -avoids unknowingly accepting intolerable and senseless risk -Allows operating decisions to be made -improves resource distribution for mitigation of loss resources |
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Advantages of Energy Flow and Barrier Analysis (EFBA) |
-Systematic approach to dealing with hazards associated with energy sources -Focus on system energy is an effective way to identify source of the danger -Effective way to determine effectiveness of existing barriers or determine new ones. |
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Limitations of Cause and Effect Analysis |
Not well suited for extremely complicated problems, especially with problem that has many causes or when problems are interrelated
-Similar causes likely to appear in repetitive manner, complicating the analysis by making it very difficult to identify causes due to multiple factors |
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Minimal Cut Set |
A group of the least amount of initiators that will, if they all occur, will cause the TOP event to occur.
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Cut Set |
Any group of initiators that will, if they all occur, cause the TOP event to occur
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Minimal Path Set |
A group of the least amount of fault tree initiators that if none of them occurs, will guarantee that the TOP event cannot occur.
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