Fault Tree Analysis advantages

Simplified equations and fault tree analysis will be used to determine the PFDavg of the SIF shown in Figure 13-3. One advantage in using the fault tree approach for the PFDavg calculation for this SIF is that most engineering personnel are familiar with the development and analysis of fault trees. This enables them to better understand the operation of complex safety instrumented functions by reviewing its associated fault tree. 

Define the four commonly used symbols to perform fault tree analysis. What are the main advantages and disadvantages of fault tree... 

Software System Hazard Analysis This type of analysis is conducted similar to a hardware system hazard analysis (SHA), analyzing software functional processing steps to determine whether they may have any particular hazardous effect on the system. The analysis utilizes a hazard-risk index to illustrate the severity of each potential failure. The main advantage to this method is in its ability to positively identify safety-critical hardware and software functions as well as consider the effect of the human element in system software operations. The results of the software SHA, which identifies single-point failures or errors within a system, can often be used to assist in the development of a software fault tree analysis or, to some degree, a system FMEA. However, as with the other various SWHA techniques briefly described above, this method is also time-consuming and costly to perform. 

Fault Tree Analysis - working backwards from a failure or potential failure, this logical procedure identifies all the possible causes, and hence, the origins of that failure. The fault tree consists of branches connected by AND and OR nodes - all the branches below an AND node need to coincide for the event above the node to occur, but only one of the branches below an OR node is required to condition the same. In these terms, a cause-effect map of failure is constructed. The advantage of such analysis is that it codifies a common understanding of the intrinsic logic of failure possibility. 

Qualitative reliability analysis are used to identify possible ways in which a system can fail. The calculation can result in all combinations of components and human failures that lead to safety (protection) system failure, which prevents the safety system to shut-down the reactor upon request. For this analysis a top-down logic model, known as a Master Logic Diagram (MLD), similar to a fault-tree, could advantageously be used with a top event of a safety system failure upon request. The results of this analysis can be used to prove the fulfillment of the important single failure design criteria. 

The objectives of this standardized observational technique are risk assessment as well as effectiveness evaluation of traffic facilities, not estimations regarding the quantity of accidents [35]. Thereby, conflicts have a probability to become accidents, which does not mean that accidents can be predicted with the method [35]. The transition probabilities between conflicts and accidents, as needed, for example, in the above-mentioned fault tree analyses, can be assessed [42]. Compared to accident analysis, investigating conflicts has the following advantages [35] ... 

One of the advantages of the fault tree method is its adaptability to mathematical analysis. The probabilities of the basic events at the bottom of the tree must be known or estimated. Analysis then moves up the tree with the aid of Boolean algebra. We are interested in two possible relationships between events leading to a step up the tree. First, either of the two events may suffice. Chlorine escapes when its rate of flow is too high OR the rate of supply of NaOH is too low. Either failure causes a gas release even if the... 

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