FTA diagram - Hazard analysis

The FTA diagram example "Hazard analysis" was redesigned from the illustration of the article "Hazard Analysis Methodologies" from the Occupational Safety & Health Administration (OSHA) website.
"A fault tree analysis is a quantitative assessment of all of the undesirable outcomes, such as a toxic gas release or explosion, which could result from a specific initiating event. It begins with a graphic representation (using logic symbols) of all possible sequences of events that could result in an incident. The resulting diagram looks like a tree with many branches — each branch listing the sequential events (failures) for different independent paths to the top event. Probabilities (using failure rate data) are assigned to each event and then used to calculate the probability of occurrence of the undesired event. ...
This technique is particularly useful in evaluating the effect of alternative actions on reducing the probability of occurrence of the undesired event."
[osha.gov/ SLTC/ etools/ safetyhealth/ mod4_ tools_ methodologies.html]
The FTA diagram example "Hazard analysis" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Fault Tree Analysis Diagrams solution from the Engineering area of ConceptDraw Solution Park.

The vector stencils library "Fault tree analysis diagrams" contains 12 symbols for drawing Fault Tree Analysis (FTA) diagrams.
"Fault tree analysis (FTA) is a top down, deductive failure analysis in which an undesired state of a system is analyzed using Boolean logic to combine a series of lower-level events. This analysis method is mainly used in the fields of safety engineering and reliability engineering to understand how systems can fail, to identify the best ways to reduce risk or to determine (or get a feeling for) event rates of a safety accident or a particular system level (functional) failure. FTA is used in the aerospace, nuclear power, chemical and process, pharmaceutical, petrochemical and other high-hazard industries; but is also used in fields as diverse as risk factor identification relating to social service system failure.
In aerospace, the more general term "system Failure Condition" is used for the "undesired state" / Top event of the fault tree. These conditions are classified by the severity of their effects. The most severe conditions require the most extensive fault tree analysis. These "system Failure Conditions" and their classification are often previously determined in the functional Hazard analysis." [Fault tree analysis. Wikipedia]
The shapes example "Fault tree analysis diagrams" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Fault Tree Analysis Diagrams solution from the Engineering area of ConceptDraw Solution Park.

This FTA diagram example was redesigned from the Wikipedia Commons file: Example Code Fault Tree.jpg. [commons.wikimedia.org/ wiki/ File:Example_ Code_ Fault_ Tree.jpg]
"Use of Software Fault Tree Analysis.
Any SFTA must be preceded by a hazard analysis of the entire system. The information in the hazard analysis identifies those undesired events in the system that can cause serious consequences. It should be noted that in comple x systems not all hazards can be predetermined.
In this respect the technique does not claim to produce consistent results irrespective of the analyst. It is dependent on the judgment of the individual as to when to stop the process and which hazards to analyze.
The SFTA can be used at different stages of the software life cycle, beginning at the software requirements phase. At that early stage, only the bare minimum of the software will be defined, though the system will usually have a preliminary design. Only a very high-level SFTA will be able to be performed. However, as the software design progresses, and the code is developed, the SFTA can be “fleshed out” with the new information. High-level blocks can be broken down into specific components (modules, classes, methods, etc.)." [NASA Software Safety Guidebook. hq.nasa.gov/ office/ codeq/ doctree/ 871913.pdf]
The FTA diagram example "Code fault tree" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Fault Tree Analysis Diagrams solution from the Engineering area of ConceptDraw Solution Park.

"Fault tree analysis (FTA) ... can be used to:
(1) understand the logic leading to the top event / undesired state.
(2) show compliance with the (input) system safety / reliability requirements.
(3) prioritize the contributors leading to the top event - Creating the Critical Equipment/ Parts/ Events lists for different importance measures.
(4) monitor and control the safety performance of the complex system (e.g., is a particular aircraft safe to fly when fuel valve x malfunctions? For how long is it allowed to fly with the valve malfunction?).
(5) minimize and optimize resources.
(6) assist in designing a system. The FTA can be used as a design tool that helps to create (output / lower level) requirements.
(7) function as a diagnostic tool to identify and correct causes of the top event. It can help with the creation of diagnostic manuals / processes." [Fault tree analysis. Wikipedia]
The fault tree analysis diagram template for the ConceptDraw PRO diagramming and vector drawing software is included in the Fault Tree Analysis Diagrams solution from the Engineering area of ConceptDraw Solution Park.