Reliability Risk Assessment Of High Temperature Bolted Flange System

With the development of process industry equipment toward the large type and high parameters, the reliability of bolted flanged joint system is considered more and more important for long period and safe service at high temperature. The failure of bolted flanged connections will lead to enormous economic loss, serious environment pollution and personal injury accidents at elevated temperature. So it's important significance to make reliability analysis and risk assessment of bolted flange system. In this paper, main researches are as follows:1. In industrial production, many of equipment work at high temperature and high pressure. Because of long period service at high temperature, bolts in flange system will be of irreversible plastic deformation and destroyed by high temperature creep. In order to research characteristics of the 25Cr2MoVA bolt material, creep test at 550℃was carried out, and then a creep constitutive equation of the material was derived based on test data.2. In recent years, owing to the great number of flange joints and complexity of work condition, the failure rate of flanged joint system is increasing continuously. To analyze the reliability of bolted flanged system conveniently, the fault tree of joint system was constructed on the basis of investigating work conditions and combining with reference literatures. The minimal cut sets of fault tree were established with the Semanderes'method, and found out bottom events which were easily invalidated. The structure importance of these events was calculated. All these provided a method of failure analysis of bolted flanged joints at elevated temperature.3. In this paper, by using the deformation equation of compatibility, which was based on bolt creep of flange system at high temperature, the leakage failure probability was calculated by limit equation of leakage rate. According to the fault tree of bolted flanged joint system at high temperature, the total failure probability of the joint system at high temperature was estimated with the method of expert assessment and fuzzy mathematics principles.4. Because of complexity and uncertainty of operation conditions, it is...