The flanged joints are widely used in industry and its application in sub-sea equipment requires a high degree of reliability, given the environmental conditions and loads, especially in deep water conditions. The reliability of a flanged joint consists of the maintenance of its characteristic seal, being the component responsible for sealing the joint. The seal exercised by the joint is due to the action of deformation caused by clamping force of the bolt sets, the latter being critical elements of flanged joints. In order to investigate this component's failure, a numerical methodology is developed, using the Finite Element Method to evaluate the impact of the successive loss of cases in a flanged joint. It was also investigated the relaxation of tension, caused by a crack in bolt set. The study aims to know the limits of safe operation, and this paper presents the analysis of a flange class API 17D, 4 inches with 8 bolt sets, being the methodology applicable to any other flange. The numerical study was developed and simulated in ANSYS Workbench 12.1 (2010) software. The result indicates, besides the minimum number of cases necessary to maintain the seal, the increase of tension in the remaining cases of the flange, caused by the successive loss of bolt sets.
Flanged unions; failure analysis; stress analysis; finite element
