Hello, I am working on a 1977 vessel, which has some corrosion on the bottom and top 2:1 semi-elliptical heads. UT survey shows corrosion in a band below the weld on bottom head. The questions are as follows:
1) the head material is SA-455A, section II I have has stress value for SA-455 but not the SA-455A, can someone tell what is the stress value/tensile strength for SA-455A plate ≤0.38". the vessel is designed to ASME sec VIII div 1, MAWP 125 psi @ max 450 F min -20 F?
2) why the manufacturer data report/name plate for many of the vessels I have come across have a lower MAWP than what I would calculate based on equations in ASME section VIII div 1 code, even when I use the higher safety factor of 4 for stress values which I believe was in use at that time?
3) I have re-rated a few vessels for lower MAWP in the past but wonder what would it take to re-rate the vessel for a higher MAWP, provided I have the calculations that show a higher MAWP than one on data report?
Appreciate your help. thanks.
1) the head material is SA-455A, section II I have has stress value for SA-455 but not the SA-455A, can someone tell what is the stress value/tensile strength for SA-455A plate ≤0.38". the vessel is designed to ASME sec VIII div 1, MAWP 125 psi @ max 450 F min -20 F?
2) why the manufacturer data report/name plate for many of the vessels I have come across have a lower MAWP than what I would calculate based on equations in ASME section VIII div 1 code, even when I use the higher safety factor of 4 for stress values which I believe was in use at that time?
3) I have re-rated a few vessels for lower MAWP in the past but wonder what would it take to re-rate the vessel for a higher MAWP, provided I have the calculations that show a higher MAWP than one on data report?
Appreciate your help. thanks.
