PSI - Issue 60

Sreerag M N et al. / Procedia Structural Integrity 60 (2024) 20–35 Sreerag M N/ Structural Integrity Procedia 00 (2023) 000 – 000

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As described in the previous section, as length of long seam repair increase in axial direction, the resisting circumferential area having lower weld property increases and the failure pressure is expected to decrease. To study this effect, a parametric study is done for estimating the failure pressure by varying the repair length i.e. 20 mm, 40mm, 60 mm, 80mm,100mm, 200mm and 500mm with R1/R2 weld properties in the virgin weld (R0). Results are summarized in the table 6. For the study with R1 repair, it is found that for an axial repair length of 500mm and weld bead width of 30 mm failure pressure matches with the failure pressure of model having entire long seam R1 weld. For the study with R2 repair, it is found that for an axial repair length of 500mm and weld bead width of 30 mm failure pressure is 82 ksc which is only 1.62% less than the failure pressure of model having entire long seam R2 weld.

Table 6: Parametric study to estimate the failure pressure for different R1/R2 long seam weld repairs in Virgin weld (R0) Axial length of R0 weld and repair in the virgin (R0) long seam weld BP (ksc) % decrease in the failure pressure w.r.t R0 failure pressure Axial length of R0 and weld repair in the virgin long seam weld BP (ksc)

% decrease in the failure pressure w.r.t R0 failure pressure

92.0 91.9 91.9 91.8 91.7 91.2 90.4

Full R0 weld

0.00 0.11 0.11 0.22 0.33 0.87 1.74

Full R0 weld

92.0 91.7 90.7 90.2 89.5 86.6 82.0

0.00 0.33 1.41 1.96 2.72 5.87

20mm R1 repair 60 mm R1 repair 80 mm R1 repair 100mm R1 repair 200mm R1 repair 500mm R1 repair

20mm R2 repair 60 mm R2 repair 80 mm R2 repair 100mm R2 repair 200mm R2 repair 500mm R2 repair

10.87

From past experience in fabricating over 50 numbers of Ø3.2mm segments, the repair length in long seam weld will be usually less than the 100mm. FE failure pressure is estimated for 100mm long seam weld repair (with R1, R2 and R3 weld repair) in a virgin long seam weld. Table 7 summarizes the results.

Table 7: Failure pressure for 100mm length weld repair Weld condition in long seam

Failure pressure, ksc

No L/s weld

97.37 92.00 90.05 80.69 77.50 90.99 89.52 88.40

Full virgin weld (R0)

Full R1 weld Full R2 weld Full R3 weld

Virgin weld with 100mm R1 repair Virgin weld with 100mm R2 repair Virgin weld with 100mm R3 repair

When the entire long seam weld is virgin weld, the failure pressure is 92 ksc which is the realistic failure pressure. For this case the failure pressure reduces by 5.8% from failure pressure for a seamless shell. Further for 100mm long repairs in the virgin weld, the reduction in the failure pressure is 1.1%, 2.7%, 3.9% from 92ksc for R1, R2 and R3 weld repair respectively. As discussed earlier, reason for this is due to 100mm long resisting area in the long seam with 30mm weld bead having lower properties for resisting the hoop load.