Question: Why does Table 5-1 in NB/T47003.1 list two allowable stresses for stainless steel materials at 100°C?
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Why does Table 5-1 in NB/T47003.1 list two allowable stresses for stainless steel materials at 100°C? In high-stress areas such as 0Cr18Ni9, the allowable stresses at 100°C are 137 MPa and 130 MPa. What are the principles behind these allowable stress values?
One is a steel plate, and the other is a flange
High-stress rows are only suitable for components that can tolerate a small amount of permanent deformation; they cannot be used in flanges or other applications where even a slight amount of permanent deformation could lead to leakage or failure. This is the description in the standard. It can be understood that this stress value can be applied to the head and cylinder nozzles, etc. For flanges, tube sheets and forgings made of steel plates should use low stress values.
What was mentioned were “137MPa and 130MPa”; this is an error in the table editing within the standard. The columns related to strength at room temperature should be left blank, but the values ended up in those columns. If you look at the table for steel pipes further down, you’ll understand. It’s difficult for beginners to figure this out. As a standard, careful attention should be paid during editing to avoid such errors before it’s released.