PSI - Issue 80

M. Bennebach et al. / Procedia Structural Integrity 80 (2026) 136–145 Author name / Structural Integrity Procedia 00 (2019) 000–000

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The applied loading, corresponding to the laboratory pressure cycling test is 5.3 bar in the shell and 3.8 bar in the coil. Figure 5 illustrates the resultant stress distribution and critical location.

Fig. 5. Stress field distribution from FE calculations

This finite element model will be the main source of further numerical data generation for fatigue life evaluation and intelligent sensor placement. To comply with a digital twin strategy, data from experimental campaign and in service conditions is continuously used to update the models.

3. Experimental campaign This part concerns the physical twin. The objective of the experimental phase is to target the gauges placement zones, confirm the reliability of the numerical model developed for the fatigue analysis and provide data exchange with the digital twin. Thanks to previous FE simulations, return on in service experience and pressure vessels experts feedback, an instrumentation and inspection strategy was developed. This guides us towards monitoring critical areas, with highest probability of failure, corresponding to welded zones in the bottom part of the equipment. To inspect critical areas, the multi-encoded ultrasonic inspection method according to NF EN ISO 9712 (2022), NF EN ISO 13588 (2019), and NF EN ISO 19285 (207) is involved. This method is based on the use of incidence angles of the ultrasonic waves emitted from a 5L16 type probe, to cover different inspection areas. It allows the detection of defects such as cracks, porosities, and inclusions in the welded areas. Five critical welds were selected for monitoring: the longitudinal weld of the shell, the circumferential weld that joins the shell and the half-sphere, the two corner welds that join the two coils to the vessel, and the weld that joins the half sphere to the nozzle (see Figure 6). The inspection of the welds with ultrasound revelated several defects (red circles in Figure 6). These defects were used as reference points for instrumentation. A total of eight strategic locations were identified, each located near a defect detected during the inspection of the five welds. In addition, two other locations were chosen outside of these welds for model calibration purposes.