Evaluating the failure risk with and without failure data

Abstract

Traditionally, the risk priority number (RPN) is used to compute the failure risk by multiplying occurrence, detection, and severity factors. Claiming that the key feature of multiplying the three factors together to get the RPN is a limitation of this method, existing studies have developed the multiple criteria decision making (MCDM) approach. In this paper, we first show that the multiplication of the three factors is indeed useful not only for evaluating the failure risk based on the trade-off between the improvement cost and risk reduction but also for identifying an appropriate action to reduce the risk of a fixed failure only if failure data is available for evaluating each of the three factors. We then develop a modified method to use the well-established multiplication operation even when each factor is evaluated by an expert. A numerical example is presented to illustrate the advantage of the modified method over the previous MCDM approach in determining the effectiveness of action plans for system risk reduction when only qualitative data is available.