TGS4 said:
However, per Table 4.1 of API 579-1 (Title: Temperature Limit Used to Define the Creep Range), creep starts at 427°C for 1-1/4Cr-1/2Mo materials. Therefore, I would tend to fall back to the limit is Table 4.4.1 for compressive stresses.
Ok. Then listing the temperatures for SA 387 Gr 11 Class 2-
ASME Sec II part D, Table 1A - Note T3 Allowable stresses for temperatures of 455°C and above are values obtained from time–dependent properties. (Tensile)
ASME Sec II Part D, Table 5A - Note T7 Allowable stresses for temperatures of 500°C and above are values obtained from time–dependent properties. (tensile)
ASME Sec VIII Div 1, Part 4, Table 4.4.1 Maximum Metal Temperature for Compressive Stress Rules -425deg C (Compressive)
API/ASME FFS 579 - Table 4.1 – Temperature Limit Used To Define The Creep Range -427deg C (Most probably tensile)
Then If I look at the API 579, it directs me to Annex 2D.
API/ASME FFS 579 said:
10.5.5 Creep Buckling
10.5.5.1 b) 4)-If a numerical analysis is performed to determine the buckling load for a component, all possible buckling mode shapes shall be considered in determining the minimum buckling load for the component (see Annex 2D).
Annex 2D said:
2D.4.1 Assessment Procedure
The assessment procedures for Protection Against Collapse from Buckling shall be in accordance with VIII-2, Part 5, paragraph 5.4 except that the a RSF may be applied for load case combinations as shown in Table 2D.2 in a Type 1 or Type 2 assessment, and that the load case combinations as shown in Table 2D.4 that incorporate a RSF may be used in a Type 3 assessment.
Then If I have to use Sec VIII Div 2 Part-5, am I supposed to use Table 4.4.1? I think no (or....yes if "compressive " stress temperature limitation exists only at Table 4.4.1).
Its clearly confusing to see so many requirements. Perhaps code interpretation exists or may I suggest
VeeEng to raise code interpretation?
On side note- best option is avoid MOC that is in creep range at operating temperature. Why to make life of vessel hell when it is already experiencing lot of "stress"?