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Finite element evaluation of the support-induced restraint effect on the limit loads of surface cracked tubes

Heat exchangers are widely used in electric power plants as well as petrochemical facilities. Typical heat exchangers consist of a number of thin-walled tubes, supports, a main body, and so on. Operating experience of the heat exchangers has shown that cracks of various morphologies frequently occur in the tubes. Therefore, an accurate integrity assessment of the cracked tube is very important from the viewpoint of safety and reliability. The heat exchanger tubes are supported at regular intervals by the supports and rotations of the tubes are restrained. In the authors' previous study, it was revealed that the limit loads for circumferential through-wall cracks are significantly affected by the supports and existing limit load solutions without considering the support-induced restraint effect differ from the actual failure load. However, the effect of the supports on the global limit load of surface cracked tubes has not been fully investigated. This paper provides detailed global limit load solutions for the tubes with circumferential surface cracks considering the restraint effect of the supports. Such solutions are developed based on three-dimensional finite element analyses. The resulting limit load solutions can be simply used in practical integrity assessment of the heat exchanger tubes.