Investigation On Maintenance Strategy Of Bolted Flanged Connections

In process industries, the leakage accidents caused by the failure of sealing systems take place frequently in these latter days. By regarding all factors influencing the reliability of the connections, the appropriate bolted flanged connections can be designed or selected to decrease the risk of the leakage accidents and improve the security of the equipment or pipeline. It is necessary to investigate the efficient maintenance technology for the bolted flanged connections in order to reduce the failure rate of the connections and keep the equipment or pipeline working reliably.Based on the reliability theory, the fuzzy logic inference method and the logical decision method, the reliability centered maintenance (RCM) intelligent decision technology for the bolted flanged connections of some key equipment in Yangtze Petrochemical Corporation was developed in this thesis. The main research work and conclusions are summarized as follows:(1) The performances of the metal octagonal gaskets and the creep characteristic of the bolt material at elevated temperature were investigated experimentally. The corresponding characterization equations were obtained by regression analysis method.(2) The random distribution regularity of the parameters were investigated, such as the operation pressure and temperature, main structural dimensions of the parts in the connections, material yielding stresses of the parts and the pretightening loads etc. According to the interference model of stress and strength, the reliability evaluation method for the bolted flanged connections was built, based on the tightness analysis method. The maintenance period of the sealing systems can be ascertained by using the visual calculating software developed in this thesis.(3) In consideration of the variation of the operation conditions and different types of the media, and on the basis of the expert experiences, the qualitative analysis of the failure causes and consequences of the bolted flanged connections was carried out by using the failure mode, effect and criticality analysis (FMECA) method. The...