Risk Evaluation of Boiler Tube Using FMEA

Traditional FMEA (failure mode and effect analysis) analysis has some drawbacks so that affect the risk evaluation and correction action. It is very difficult for three risk factors to be evaluated precisely. Simultaneously, traditional FMEA doesn´t consider the relative importance of three risk factors. The critical problem is that same RPN (risk priority number) can be obtained by different combination of three risk factors. So, the fuzzy logic is introduced into traditional FMEA to solve above problems. The rating of three factors is expressed as triangular fuzzy number and the relative importance among O (occurrence), S (severity) and D (detection) is also considered as triangular number, so the new fuzzy FMEA method is presented. In calculating the risk priority of failure modes, introduces ¿ cut and satisfactory index ß to obtain crisp number by defuzzification. So the failure mode with maximum risk priority is identified to correct. Finally, this method is applied in the risk evaluation of boiler tube.