Risk analysis of corrosion failures of equipment in refining and petrochemical plants based on fuzzy set theory

• A model for risk analysis of corrosion failures of equipment is proposed.
• Fuzzy synthetic evaluation is used to analyze failure likelihood and severity.
• Fuzzy risk graph used to calculate risk index is established based on fuzzy logic.

Corrosion failures of process equipment have been one of the main sources of risk to refining and petrochemical plants. For reducing failure risk levels and optimizing inspection plans, risk analysis of equipment failures resulting from corrosion need to be implemented. However, due to the complexity and uncertainty of the refining and petrochemical units and risks, effective analyses are hard to accomplish by using conventional risk techniques. With respect to this, a new model for risk analysis of corrosion failures of equipment is developed base on fuzzy set theory. In this model, two essential parts of failure risk (i.e., failure likelihood and severity of failure consequence) are first estimated by using fuzzy synthetic evaluation, and then integrated into a risk index by fuzzy risk graph which is established based on fuzzy logic system. In order to demonstrate the feasibility of this model, an application example in an overhead system of a crude-oil distillation unit was presented. The results show that this model is effective and feasible.