PSI - Issue 75

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Fabrice Deleau et al. / Procedia Structural Integrity 75 (2025) 392–418 Deleau Fabrice, Emmanuel Persent, Guillaume Coudouel, Guillaume Perrin/ Structural Integrity Procedia (2025)

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Keywords: Fatigue; Stress range methodoly estimation; Prototype test; Acoustic Emision, Riser

1. Clip-Riser ® product Fatigue design analysis The first generation of the Clip-Riser ® was developed during the 1980’s by IFPEN especially for ultra -deep water drilling operations up to 10,000 ft. It was a double breech-block type connector with a rotating ring. The main advantage of this boltless connector is that it allows very fast make-up or break-out of the riser joints. The Clip-Riser ® has been used intensively over the past 25 years. Most of the customers appreciate the reliability and the operational benefits provided by this connection. A new generation called i-Clip-Riser TM (Fig. 1) is currently under development. It offers larger load carrying capabilities through load-sharing while maintaining the quick and simple connection in the previous boltless Clip Riser ® design without preload. An update of our design methodologies is thus necessary for the fatigue design optimization. A Finite Element (FE) model of the connector has been developed to perform various calculations for design validation. The i-Clip FE model is quite large, with 4.2 million degrees of freedom (DOF), making the calculations very time-consuming. An overview of the global FE model of the i-Clip is illustrated in Fig. 1, the main pipe ID is 21.25 inch with 1 inch thickness .

Fig. 1: Finite Element global overview (Von Mises Stress), hot spot location

The critical zones of the global model from the i-Clip connector, built using 2.5%Cr – 1%Mo steel (ASTM A182 F22, Table 1) were identified by analysing results from the 4,000 kips (17,793 kN) tension elastic analysis. The Hot spot (peak of Von Mises stress) in the overall connector is located in the lug groove. A mesh convergence analysis was preliminarily performed, validating that a mesh size of 4 mm and linear elements were sufficient to achieve good representativeness (error less than 5%). The critical zone, such as the lug groove, requires a finer mesh, with a size smaller than 10% of the radius of curvature. The edges of the lugs are significantly affected by bearing stress due to the geometry of their lug contact. However, based on our product knowledge, it can be concluded that this stress does not determine fatigue resistance. Therefore, the following study focuses on the fatigue in the lug grooves. To ensure the accuracy in the numerical analysis while optimizing computational time, a sub model was used for this critical area, incorporating enhanced geometric representation, mesh refinement, and improved elastic-plastic material law. In addition to the future qualification tests at scale 1, other experimental investigations on small-sized prototype (Fig. 2) were performed to validate our product design and optimization, as the product architecture and mechanical operations are specific and presents a triaxial stress state.