Reliability Analysis of Manufacturing Plant via Fault Tree Analysis

INTRODUCTION

FTA is a logical top-down deductive method to access or find the probability of the top event with the help of given information. FTA was introduced by H.A Watson at Bell Laboratories in 1962. Firstly, FTA was utilized by Nuclear Power Generation yet after that it wound up well known in all parts of security estimates in numerous fields (Marko et.al. 2009). It shows good results in Nuclear power generation after that it became popular in chemical process industry (Glickman, 2007, Ju et al., 2003, Zhao-Mei, 2011, Ale, 2003, Svedung et al., 2008). This technique was also used in analyzing the occupational hazards with the top event injury, staircase slipping hazard etc.(Hauptmanns et. al., 2005). A potential computer aided technique to construct FT is developed (Wang et. al., 2002). It works directly from the block diagram. This algorithm is based on loop by loop or node by node basis. Some new techniques are developed to improve the software pack of PROFAT (Probabilistic Fault Tree) initial tool to overcome these problems related to complexity of system‘s nature and in constructing the FTA of these complex systems (Khan et. al., 2000). A new concept of time analysis of safety assessment is introduced and used with FTA to reduce the complexity of computation (Magott et al., 2012). With the help of this upgrading technique, we are able to estimate the actual time dependent risk profile and it increases the applicability of FTA. Some hybrid techniques of FTA were also developed with Fuzzy logic to handle the probability of human error effectively (Kumar and Yadav, 2012, Tyagi et.al., 2010) to describe the imprecision or vagueness of events in FTA (Cheng and Mon, 1993, Chen and Yuan, 1994, Liang and Wang, 1993, Guth, 1991, Liao and Yuan, 1993, Singer, 1990, Tanaka et. al., 1983). This is most favored method for understanding logically the technique of instance of a single well- defined inadmissible event. Here inadmissible event means non-operation of the system. This method has a different way of analyzing the problem to diagnose how the system ‗may fail to function‘. As we called it is a top-down method, and we can find the failure probability of top event with the use of given failure probabilities of the subsystems. There is need to identify the event

A successful FTA depends upon the following steps: • Find the objective for the FTA • Represent the top event of the fault tree • Describe the scope of FTA • Describe the rules for FTA on which it is based • Make the fault tree • Calculation of FTA • Interpret and present the result

Notations: ni : name of subsystem ri: Reliability of subsystem Ei: failure probability of each subsystem. F: failure probability of whole system

System consists of 7 units as defined in (Devi et al. , 2017 25) paper, ni (ni, 1≤ i≤ 7) where n1 has 2 identical units which have same reliability and connected with parallel namely n11, n12 and n2 has 3 identical units namely n21, n22, n23 which have also same reliability. In the same manner n3 has 2 identical units, n4 has 5 identical units, so on which represented in the below table. Table 2 represents the subsystems, their reliabilities and corresponding units which these subsystems have contained.

Following events used in analysis as follows and shown in Figure 1: E1: represent the event that whole subsystem n1 fails when n11 and n12 are connected with AND Gate. E2: represent the event that whole subsystem n2 fails when n21, n22 and n23 are connected with AND Gate. E3: represent the event that whole subsystem n3 fails when n31 and n32 are connected with AND Gate. E4: represent the event that whole subsystem n4 fails when n41, n42, n43, n44 and n45 are connected with AND Gate. E5: represent the event that whole subsystem n5 fails and it has single unit n51,. E6: represent the event that whole subsystem n6 fails when n61, n62 and n63 are connected with AND Gate. E7: represent the event that whole subsystem n7 fails when n71, n72, n73, n74 and n75 are connected with AND Gate. Similarly failure probabilities of other subsystems are calculated below in the same manner. As shown in FTA diagram E1, E2, E3,…,E7 are the failure probabilities of the subsystem n1, n2, n3,…, n7 which are connected with OR Gate. The failure probability of the top event i.e. whole system is denoted by F so that.

FTA has been applied in this paper to estimate the failure probability of the top event of Production Machine. We got the probability of failure of production machine that is 0.146246 with the help of basic events. Considering various concepts like Marko modeling, matrix method, which have used for reliability analysis. In all mentioned approaches, difficult modeling problem, mathematical calculation and various assumption, deep knowledge and interrelationship between the subsystems makes the problem very difficult to solve. But in this paper FTA approach has overcome these problems.

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