Fault symbols

Other information that can be obtained from such map is the location of faults, the status and location of wells and the location of the fluid contacts. Figure 5.45 shows some of the most frequently used map symbols. Structural maps are used in the planning of development activities such as well trajectories/targets and the estimation of reserves. 

The foUowiag symbols are used ia fault tree constmction to display the iaterrelationships between equipment failures and a specific accident ... 

The TRANSFER IN symbol iadicates that the fault tree is developed further at the occurreace of the corresponding TRANSFER OUT symbol. 

This section describes the most commonly used method for complex systems analysis - fault tree analysis. The previous section introduced cutsets as physically cutting through an RED, here, cuiscis. ire presented mathematically. The symbols of fault trees are introduced and a heuristic... 

Figure 3.4.4-1 summarizes conventional fault tree symbols. The many symbols are daunting, but remember that the computer only performs AND (Boolean multiplication) and OR (Boolean addition) operations. All else are combinations of these. 

For an expanded discussion of the symbol meanings, refer to the Fault Tree Handbook, NUREG-0492. 

Some of the features of GO (EPRI NP-3123) are given in Table 3.4.6-2. A GO model is networks GO operators to represent a system. It can be constructed from engineering drawings by replacing system elements (valves, switches, etc.) with one or more GO symbols. The GO computer code quantifies the GO model for system reliability, availability, identification of system fault sequences, and relative importance in rank of the constituent elements. 

It IS necessary to convert the symbolic fault graph into a form suitable for mathematical imilysis by forming an adjacency matrix to show nearest-neighbor connections and required input lor an "AND" gate. 

Fig. 3.6-1 The Saphire Main Menu and the Fault Tree Editor Menu. Symbols are selected and pasted into the working space...

The fault tree symbols and their definitions are presented in Table 16.6.1. The construction of tlie fault tree for a tmik overflow c.xaniple is demonstrated in Figure 16.6.1. 

Bums and Hazzan demonstrated tlie use of event tree and fault tree analysis in tlie study of a potential accident sequence leading to a toxic vapor release at an industrial chemical process plant. The initiator of tlie accident sequence studied is event P, the failure of a plant programmable automatic controller. Tliis event, in conjunction willi the success or failure of a process water system (a glycol cooling system) mid an operator-manual shutdown of tlie distillation system produced minor, moderate, or major release of toxic material as indicated in Fig. 21.4.1. The symbols W, G, O represent tlie events listed ... 

General considerations of data availability lead immediately to the recognition that detection systems are more likely to be designed as comprehensive numeric-symbolic interpreters as illustrated in Fig. 3. State description systems may be configured as shown in either Fig. 3 or Fig. 4. Fault classification systems are most likely to require the symbolic-symbolic mapping to compensate for limited data as shown in Fig. 4. Many practical data interpretation problems involve all three kinds of interpreters. In all situations, there is a clear need for interpretation systems to adapt to and evolve with changing process conditions and ever-increasing experience. 

With the view that a KBS interpreter is a method for mapping from input data in the form of intermediate symbolic state descriptions to labels of interest, four families of approaches are described here, each offering inference mechanisms and related knowledge representations that can be used to solve interpretation problems namely, model-based approaches, digraphs, fault trees, and tables. These methods have been heavily used... 

The fault tree is a graphic representation of the relationships between basic events and the selected top event. Table 4.24 presents the standard symbols used in fault tree construction to show these relationships. 

TRANSFER OUT symbol. Transfer symbols are used to transfer off-page or to avoid repeating identical logic (with identical events) in several places in a fault tree. 

The flat tire example is pictured using a fault tree logic diagram, shown in Figure 11-12. The circles denote basic events and the rectangles denote intermediate events. The fishlike symbol represents the OR logic function. It means that either of the input events will cause the output state to occur. As shown in Figure 11 -12, the flat tire is caused by either debris on the road or tire failure. Similarly, the tire failure is caused by either a defective tire or a worn tire. 

TRANSFER Symbols Used to transfer the fault tree... 

In the opening segment the facilitator should discuss the importance of and methods for choosing the top event and any preestablished and existing boundaries of the investigation. If multiple events are involved, it is best to start with the last event in the time sequence. It may be appropriate, depending on the nature of the occurrence, to formally review the rules and symbols used in logic tree or fault tree development or whichever other formal method will be used. 

EXTERNAL or HOUSE Event The EXTERNAL or HOUSE event represents a condition or an event that is assumed to exist as a boundary condition for the fault tree. The HOUSE symbol also implies that the event has a high probability of occurring. 

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