Undeveloped events

Undeveloped event - An event le not developed further either becauee it is of Insufficient conaequence or becauae information Is unavailable. 

UNDEVELOPED Event An event that cannot be developed further due to lack of suitable i nformat ion. 

UNDEVELOPED Event The UNDEVELOPED event represents a fault event that is not examined further because information is unavailable or because its consequence is judged insignificant. In this book, the diamond with Why inside it is used to indicate events which were not developed in the examples, but should be developed in actual investigations. 

The quantitative evaluation of the fault tree is done by analyzing the structure of levels using the Boolean algebra to determine the minimum combinations of terminal events or minimum sets of faults that lead to the undesired event. Its probability is calculated based on the probabilities of the basic events and undeveloped events to be evaluated from available historical data. 

Continue down the FT until you reach a fundamental triggering event that (a) cannot be usefully deconstructed any further, (b) at which the failure probability can be justified or (c) where you have reached the scope (see Section 4.2.1) of the FTA. These events are at the bottom of the FT and are referred to as either Basic Events or Undeveloped Events ... 

An undeveloped event represents an event where further development is either not possible or would serve no benefit. This event type is mostly used when the probability is already orders of magnitude smaller than other contributors to a gate, such that the gate probability is dominated by other inputs. It is therefore of no benefit to expend further effort in developing this part of the FT. 

UNDEVELOPED event - an event that has not been developed either because it is developed in a separate assessment, the contribution is negligible or there is insufficient information to develop further... 

UNDEVELOPED EVENT ONE THAT, BY EITHERCHOICE OR NECESSITY, WILL NOT BE DEVELOPED FURTHER... 

The primary symbols used for most analytical trees have been used in the MORT event tree as well. These include the rectangle (primary or top event, and secondary, contributory or main events), the diamond (undeveloped event), the circle (basic event), the and gate, the or gate, the oval (conditional or constraint symbol), and the triangle (transfer gate or symbol). In addition to these symbols, the MORT... 

Undeveloped event Undeveloped event of known causes... 

A diamond represents an undeveloped event. It is an event that an analyst chooses not to analyze. Although it may merit further analysis, an undeveloped event may simply be a curiosity or may not be critical to the problem at hand. Analyses may result in assigning a probability to an undeveloped event. Sometimes there is an undeveloped event, but the analysis team may have deeper knowledge about that branch of the tree. Some people use a double diamond for undeveloped events. 

Quantitative Analysis of Fault Trees Quantitative analysis begins at the bottom end of each branch. One must assign a probability to each basic and normal event. One may also assign a probability of occurrence to each undeveloped event. 

Undeveloped Event Diamonds represent events that are not developed further either because the event contributes insignificantly to the top event or information relevant to further development is unavailable. 

FTA termination Fault ttee is terminated either at basic event, which represents the lowest level events, ot it is terminated at undeveloped event (which is not... 

The creation of a fault tree begins with the identification of the top event. This event can be as broad and general as Total System Failure or as narrow and specific as Component X Malfunction. This top event will be placed at the top of the tree and all subsequent events that lead to the main event will be placed as branches on the tree. Figure 12.1 illustrates the beginning of a simple fault tree, with the location of the top event, the placement of contributing events, and undeveloped events, down to the basic (or root) events. As the user moves from the top event downward, each level of the tree will materialize. In order to proceed from one level to the next, the analyst must continually ask the fundamental question What could cause this event to occur As causal events are identified, they are placed in position on the fault tree (Figure 12.1). 

Undeveloped Event As pertains to fault tree analysis (FTA) and/or the Management Oversight and Risk Tree (MORT), an identified fault event that will not be developed further because its occurrence has been determined insignificant with regard to its effect on the top event, or insufficient data exist to further evaluate the event, or the event is too complex for the purpose of a specific evaluation. Represented graphically by a diamond shape. 

A diamond describes an undeveloped event for which no further analysis is required or for which information is unavailable to develop the event further. Undeveloped events are de facto boundary conditions to the problan. Any fault can be left undeveloped if you cannot ascertain how it occurs (what its inputs are) or if they are not important to the next event. 

Basic event A fault tree event that is sufficiendy basic that no further development is necessary (e.g., equipment item failure, human failure, or external event). See also Undeveloped Event. 

Undeveloped event A base event that is not developed because of insuflheient consequence or because information is unavailable. 

Undeveloped event (diamond) Failure which is at the lowest event of examination by the fault tree, but can be further expanded. 

Undeveloped events are events that could be broken down into subcomponents, but, for the purposes of the model under development, are not broken down further. 

An example of an undeveloped event may be the failure of the instrument air supply. An undeveloped event symbol and a single failure rate can be used to model the instrument air supply rather than model all of the components. FTA treats undeveloped events in the same way as basic events. 

Also, this example shows an undeveloped event (crew error), which in this example is not developed further because it does not contribute to the occurrence of the top event. 

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