Fault Tree Analysis A graphical tool for representing the relationships among a variety of expected and unexpected events that may contribute to a particular type of system failure.
How to understand it (a) an 'and' combination (b) an 'or'' combination.
Fig. 2. Logical And and Or in Fault Tree Analysis
How to understand it inhibit gate, (AND) Two failure event box: combination events and basic events basic events real root events or may simply not be developed further.
Classic Fault Tree Gates Name of GateClassic FTA SymbolDescription AND The output event occurs if all input events occur. OR The output event occurs if at least one of the input events occurs. Voting OR (k-out-of-n) The output event occurs if k or more of the input events occur.
Classic Fault Tree Gates Name of Gate Classic FTA Symbol Description Inhibit The input event occurs if all input events occur and an additional conditional event Priority AND The output event occurs if all input events occur in a specific sequence. XOR The output event occurs if exactly one input event occurs.
Traditional Fault Tree Event Symbols Primary Event Block Classic FTA Symbol Description Basic Event A basic initiating fault (or failure event). External Event (House Event) An event that is normally expected to occur. Undeveloped Event An event which is no further developed. It is a basic event that does not need further resolution. Conditioning Event A specific condition or restriction that can apply to any gate.