Causes of uncertainty in FTA method and use of fuzzy logic to solve this problem

Increasing the number and capacity of chemical industries in the recent years and their complexity leads to more industrial accidents. Due to consequences of such accidents a high cost imposed to industry, society and the environment. This makes safety analysis more important. Therefore qualitative and quantitative hazard analyses are essential for the identification and quantification of these hazards related to chemical industries. Fault tree analysis (FTA) is an established technique in hazard identification. This technique has the advantage of being both qualitative and quantitative, if the probabilities and frequencies of the basic events are known. However, people when using FTA often suffers from a lack of detailed data on failure rates, uncertainties in available data, imprecision and vagueness. This may lead to uncertainty in results and process risk level. Fuzzy logic deals with uncertainty and imprecision, and is an efficient tool for solving problems where knowledge of uncertainty may occur.In this paper traditional fault tree analysis was combined with fuzzy set theory. In the fuzzy method, all variables are replaced by fuzzy numbers in the process of fuzzification and subsequently fuzzy probability of the top event is used for fault tree

Keywords:

fault tree analysis , uncertainty , fuzzy logic , fuzzy operator