Study On The Risk Assessment And Risk Management For In-service Safety Valves Of Petrochemical Equipment

As a new technology the risk engineering is involved in many scientific fields.The purpose to research it is to turn the project danger to security and compromise theproject cost. In this paper, the risk assessment of in-service valves is given based onRBI method and the inspection period of off-line valves is decided by the risk grade.The inspection interval of low-risk safety valve could be prolonged so that the cost ofinspection is reduced. In this paper the spring loading safety valve is taken as theresearch object and the total research work is as follows: 1. The failure probability of the safety valve's spring is calculated. The springfailure has two modes, the fracture failure and sealing failure due to the decreasing ofspring's stiffness because of spring's stress relaxation. Based on the reliabilityengineering, the fracture failure probability is calculated with first-ordersecond-moment method; combining the examination of the spring's stress laxity, thesealing failure probability is calculated with improved linear second order momentmethod. The maximum of the two failure probabilities is used to determine the springfailure factor's grade. 2. The safety valve's basic performance requests are analyzed, and the factorsresulting in the failure of safety valve are spring failure, operating status, recordingand management level. These failure factors are assessed comprehensively ondiscipline extenics method. The result of this assessment is the failure likelihoodgrade. 3. The analysis of important injury accident owing to the failure of safety valve isconducted and by calculating injury radius the seriousness of human casualty andestablishment loss are determined. The consequence factors are human casualty,equipment damage, business losing, environment pollution and toxicity, and thefailure consequence is graded with the extenics assessment. 4. When the failure likelihood grade and consequence grade are both given, therisk category of safety valves is evaluated by a risk matrix, and the inspection period iof safety valves is determined by the risk category. 5. The risk assessment software is developed with the object-oriented method.The software system has friendly and wieldy interface. Since the class-designedmethod is used to perform this assessment software, the system is maintained andexpanded easily, furthermore it is developed on J2EE platform and the advantage ofplatform independence of Java program langrage is full used so that the riskassessment software is adapt for different type of operating system.