圧力機器の供用適性評価技術

第3報 FEM解析例による減肉評価法の比較

抄録

This is the third report (Part 3) in a series of interpretations of general and local metal loss assessment procedures specified in the Fitness-for-Service (FFS) assessment procedure developed by the PAJ⁄JPCA FFS task group based on API RP 579.
This report is aimed at understanding the safety margin for failure, as described in Section 5 (Local metal loss assessment in API RP 579, 2000) , by using a modeled pressure vessel. First, the cylindrical pressure vessel that has no corrosion allowance (nominal thickness=minimum required thickness) is modeled; further, the vessel is provided with a local metal loss that is equal to acceptable limits, as prescribed by the local metal loss assessment. Next, an FEM plastic analysis is performed for this modeled pressure vessel and the failure pressure is calculated.
It is found that the failure pressure of acceptable limits in Section 5 is 3. 4 times the designed pressure;further, approximately 90% of the pressure vessel exhibits no local metal loss.