Reliability of the furnace in an existing industrial continuous catalytic reforming unit was investigated with the fuzzy fault tree analysis method. A fault tree was developed considering failure of the reforming furnace to be a top event. Thirty-one minimum cut sets were achieved by qualitative analysis with the ascending method. The concept of fuzzy number of the fuzzy sets theory was applied to describe the probability of basic event occurrence in the fault tree

and the fuzzy failure probabilities of the middle events and the top event were calculated with fuzzy AND and OR operators. Among all middle events the probability of tube failure is highest

and the tube failure probability in the radiant chamber is clearly higher than that in convection chamber

showing that the radiant chamber tube is a weak part in the furnace. The results show that the fuzzy fault tree proposed is an effective method of reliability analysis for petrochemical equipments and its calculation results are more reasonable than those of the conventional fault tree.