I have a question regarding allowable stresses in ASME Section II, Division D
Thread Content
When performing calculations for the strength of boilers and determining the thickness of pipes, the material used is SA213-TP347H. Referring to ASME Edition 2015, Volume II, Section D, P102, rows 3 and 4 both specify SA213-TP347H as the material. So which row’s allowable stress should be chosen? For the SA213-T91 material, in P46, rows 15 and 16 also specify T91 as the material; however, row 15 indicates a thickness of less than or equal to 75, while row 16 specifies a thickness greater than 75. Thus, it is possible to determine the appropriate value based on the thickness of the pipe. Is that correct? I hope experts who are aware of this can respond; thank you! !
The SA213-TP347H material has two sets of allowable stresses, similar to the fact that stainless steels also have two types of allowable stresses according to national standards; the principle is the same. The criteria for determining allowable stresses are clearly explained in Volume D. Or check the instructions for betting on G5. SA213-T91 pipes are specified based on their thickness.
Thanks for the advice, boss! I checked the explanations for G5, T8, and T9 – is it correct to understand it this way? When the temperature is 620 or higher, it’s T9, which means choosing the fourth row ； When the temperature is greater than or equal to 595 and less than 620, it is T8; select the third row ； Also, flanges connected by gaskets or slight deformation can cause leaks or failures; in such cases, G5 (the one in the third row) is not chosen ； For ordinary TP347H material, one can choose the option in the third row – is that what it means??
G5 specifies the conditions under which the allowable stress for this row cannot be used, while T8 and T9 state that for the allowable stresses in these two rows, when the temperature is higher than 595 degrees and 620 degrees respectively, the allowable stress is determined by the creep limit.
It’s simply high stress and low stress; high stress should not be used for components that are subject to slight deformation, such as flanged tube sheets
Thank you for the guidance! ! So, when calculating the thickness of the pipes used in general design, G5 is chosen based on the material of those pipes, and the allowable stress value from the third row can be used, right?