Abstract
When using the risk priority number method to perform a criticality analysis of the failure modes of mechanical products, different subjective factors exist on the part of experts regarding the severity level (S), occurrence probability level (O), and failure modes. The estimation of the detection difficulty level (D) is different, which causes the problem of inaccurate evaluation of the criticality of failure modes. This study proposes a harm analysis method that combines group decision-making and fuzzy comprehensive evaluation. The similarity and difference between an individual expert and the group are used in group decision-making to assign the weight of the expert, thus reducing the influence of subjective factors on the evaluation results. On the basis of the fuzzy comprehensive evaluation method, the weight of three risk elements (S, O, and D) is determined, and a hazard ranking of the interval obtained by group decision-making is performed. The CA (criticality analysis) improvement method is used to analyze the hazard posed by low-temperature shut-off valves. Results indicate that this method can effectively assess the weak links of the low-temperature shut-off valves and improve the accuracy of the hazard evaluation in comparison with the risk priority coefficient method.
Highlights
Cryogenic shut-off valve is one of the most commonly used valves in cryogenic systems
A hazardous analysis of the various failure modes of cryogenic shut-off valves must be conducted to improve the reliability of these valves and identify their weak links. e risk priority number (RPN) method can intuitively reveal the degree of harm of the product failure mode, and its results are widely used in the formulation and implementation of improvement measures
According to the national standard G/JB Z1391-2006, the severity level (S), occurrence probability level (O), and detected difficulty level (D) of a failure mode can be divided into 10 scores or 5 score levels. e severity level is used to evaluate the final degree of influence of a certain failure mode, the occurrence probability level is the possibility of a failure mode occurring, and the detected difficulty level represents the difficulty of detection during use. e higher the values of the evaluation factors are, the greater the harmful effect of the failure mode is on the product. e specific scoring standards are shown in Tables 1 and 2. It can be seen from the above discussion that the evaluation of the risk priority coefficient method is simple and intuitive, the RPN value in each failure mode can be calculated separately according to the formula combined with the expert score; it still has limitations
Summary
Cryogenic shut-off valve is one of the most commonly used valves in cryogenic systems. Is study uses an analysis method that combines group decision-making and fuzzy comprehensive evaluation and fully considers the influence of the subjective factors of experts. E specific scoring standards are shown in Tables 1 and 2 It can be seen from the above discussion that the evaluation of the risk priority coefficient method is simple and intuitive, the RPN value in each failure mode can be calculated separately according to the formula combined with the expert score; it still has limitations. This study uses a method that combines group decision-making and fuzzy comprehensive evaluation to analyze the failure mode. On the basis of the comprehensive fuzzy evaluation, the weight distribution of the three risk elements in RPN and the membership degree of the expert comprehensive evaluation interval are determined.
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