PSI - Issue 42

Chmelko et al. / Procedia Structural Integrity 42 (2022) 315–320 Chmelko,V. at all: / Structural Integrity Procedia 00 (2022) 000–000

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2

stage protection practically excludes exceeding its permissible values. Nevertheless, in the operation of pressure pipelines destruction does occur [3]. These accidents are dangerous because they can damage the environment or endanger people's lives. The cause of these accidents is most often a synergy of several factors that need to be identified and evaluated computationally. For pipelines with detected corrosion defects, ASME or DNV standards are generally used. The calculation of the failure pressure according to ASME B31G is based on a comparison with the yield strength of the material used. Only the length and depth of the defect is considered (Figure 1), being the length in the direction of the pipe centerline. The maximum possible defect depth is 0.8 times the remaining wall thickness. The failure pressure of the site under consideration is according to [4]: = ( + 68,95 ) 2 � 1−0 , 85 1− 0 . 8 5 � , kde = � 1 + 0,6275 � √ � 2 − 0,003375 � √ � 4 (1)

Fig. 1 Longitudinally (axially) oriented corrosion defect on a pipeline according to ASME B31G

The calculation of the burst pressure according to the DNV-RP-F101 criterion is based on the ultimate stress of the material. The DNV method also considers a quadrilateral defect profile of the maximum length and depth of the actual defect (Figure 2). The maximum possible defect depth is 0.85 times the remaining wall thickness.

Fig. 2 Substitution of multiple defects by a single defect according to DNV-RP-F101

The burst pressure of the section under consideration is according to [5]: = 0.9 2 − � 1− 1− � = � 1 + 0,31 � √ � 2

(2)

The calculated limited pressures according to equations (1) and (2) for a small defect length of 10mm and pipe material properties Rm=540MPa, Re=340MPa) are in Table 1