Good afternoon,
I have an elbow in material ASTM A403 WP321. The maximum design temperature is 450°C and on ASME B31.3 Table A-1 I found its allowable stress for design calculation: 16.7 ksi. Up to now everything ok.
During following production testing I have to find, in addition to room temperature mechanical properties, its hot yield strength at 450°C. Which is the minimum acceptance criteria? ASME B31.3 (2012 edition) para 302.3 explains how the values of Table A-1 are computed, but I'm not able to understand which minimum hot yield strenght must be reached (in case we decide to test the material at its max design temp.) This value is not directly reported on the Code, I think it can be "extracted" from the Code formulas and principles. I thought this value could be 18.56 ksi as per ASME IID Tab Y-1 (even if the values of this table are not minimum to be guaranteed, but "average" values computed through interpolation). On the contrary my client told me the minimum value should be 25.05 (16.7 x 3/2) according to ASME B31.3 2012 §302.3.2 (d) (3). This same para states the allowable stress (listed in Tab A-1) shall be the lower between 2/3 of Sy (I understand specified minimum yield strength at room temp, to say 205 MPa for ASTM A403 WP321) and 90% of yield strength at temperature. If we use ASME IID Tab Y-1 as yield strenth at temperature and we compute its 90%, we exactly find 16.7 ksi. This gave "strength" to my opinion, but I really don't know which is the right option, or whether both of them are wrong..
Please, which is your suggestion and help?
Thanks so much
I have an elbow in material ASTM A403 WP321. The maximum design temperature is 450°C and on ASME B31.3 Table A-1 I found its allowable stress for design calculation: 16.7 ksi. Up to now everything ok.
During following production testing I have to find, in addition to room temperature mechanical properties, its hot yield strength at 450°C. Which is the minimum acceptance criteria? ASME B31.3 (2012 edition) para 302.3 explains how the values of Table A-1 are computed, but I'm not able to understand which minimum hot yield strenght must be reached (in case we decide to test the material at its max design temp.) This value is not directly reported on the Code, I think it can be "extracted" from the Code formulas and principles. I thought this value could be 18.56 ksi as per ASME IID Tab Y-1 (even if the values of this table are not minimum to be guaranteed, but "average" values computed through interpolation). On the contrary my client told me the minimum value should be 25.05 (16.7 x 3/2) according to ASME B31.3 2012 §302.3.2 (d) (3). This same para states the allowable stress (listed in Tab A-1) shall be the lower between 2/3 of Sy (I understand specified minimum yield strength at room temp, to say 205 MPa for ASTM A403 WP321) and 90% of yield strength at temperature. If we use ASME IID Tab Y-1 as yield strenth at temperature and we compute its 90%, we exactly find 16.7 ksi. This gave "strength" to my opinion, but I really don't know which is the right option, or whether both of them are wrong..
Please, which is your suggestion and help?
Thanks so much