Fatigue Analysis and Life Assessment of Pressurized Structures

Abstract

One of the common practices used in the industry for safe operation of in-service components is to assess the fitness for service of the components during the service life. A Fitness for service assessment is required to evaluate the structural integrity of the structure under consideration and safely evaluate the remaining life of the equipment. The most popular standard currently being used in the industry is API-579-1/ASME FFS-1, because of its standardized assessment methods and procedures. It is the objective of this thesis to apply the assessment techniques included in the API 579 to a knock out vessel installed at the purge gas service in a petrochemical industry, the vessel under consideration has been exposed to low temperatures, and has recently changed service and location. Some erosion and pitting is also present on the vessel exterior based on preliminary inspection before installation, the study is motivated by the need to conduct a safer operation of pressurized vessels. The API 579 is applied to assess the possibility of brittle fracture in the vessel due to low temperatures and the change of service and location of the vessel, the possibility of general metal loss due to the erosion on the surface in the vessel, and the effects of pitting corrosion on the main vessel exterior is also investigated. The assessment is conducted in a Fitness-forservice software IntegriWISE for the calculation of Fitness-for-service parameters used for determining the safety of operation of the vessel. The results obtained from the assessment are then validated by comparison with the benchmark ASME calculations given in the API 579 Fitness-for-Service Manual (June 2016). The assessment is conducted beginning from Level 1 of Fitness-for-service assessment in the software and then proceeded further if the results of the previous assessment are unacceptable. The results so obtained from the conducted assessment indicate that the vessel was safe for operation, and future operation as per design parameters can be carried out with further inspections to ensure the safe operation of the knock out vessel, A mobile application for the computation of the assessment parameters was also developed.