| There are numerous urea enterprises in China. Compressors and pumps are the key operating equipment in a urea unit. Once an accident occurs in a compressor or a pump, the consequence would be serious. In the actual production, the urea unit accident which is caused by compressor or pump occurs frequently. If the reasonable and effective risk analysis is carried on, and the result is applied to guide the inspection and maintenance of the equipment, the risk would be reduced, the reliability would be improved, and the level of safety in production would be raised.Analysis of failure probability and failure consequence is included in risk analysis of urea unit. First of all, failure analysis which includes failure mode and reason is carried on the compressors and pumps in the urea unit. On that basis, the effect factors of failure are utilized to do failure probability analysis. The factor set which affects to estimate the failure probability is determined, which includes design and material selection, manufacturing and installation, operation status, inspection and repair history, and management level.According to API581, the failure consequence is analyzed. The factor set which affects to estimate the failure consequence is established. And personnel casualty, property loss, environmental impact, reputation loss are included in the set. According to the grade division of failure concequence developed by General Administration of Quality Supervision, Inspection and Quarantine of P. R. C, combined the other pertinent data and experience, the failure consequence grade is compartmentalized.Fuzzy comprehensive evaluation method is used to get the grade of failure probability and consequence. Integrating with risk matrix, the risk grade of compressors and pumps in the urea unit can be calculated. Then, an example to illustrate how to use this method and the proper measures to reduce the risk are given. The visual risk analysis software is designed, which is a constituent part of the risk analysis system of urea unit. The software is programmed in Java language. It has some merits, including the vivid menu layer, the comprehensive content, the friendly man-computer interface, and good feasibility, so that the software can adapt the common operators in the plants. |
