When using the WRC 107 module in Caesar, if I choose the duplex SS plate material SA 240 UNS 31803 (my vessel material), the database gives the hot and cold allowable stress intensities, Smh, Smc. When referring to ASME BPV Section II Part D for the material properties, this material is not listed in Table 2A used for Section VIII Division 2 analysis (allowable stress intensities), but it is listed in the Table 1A used for Section VIII Division 1 analysis (allowable stresses). Why is this and other duplex materials listed in Table 1A but not in Table 2A? Secondly, where do the allowable stress intensities that the Caesar WRC 107 module lists for this material come from?

Hi Mark,

I checked with our CAESAR II development group and determined that the database the program uses is the Division 1 material database. As you noted, the Duplex SS material UNS 31803 is in this table.

Presumably the vessel has been designed correctly for primary membrane stress determination using the appropriate Code (Div 1, Div 2, ...) for internal pressure. So that check in the stress summation should always be OK. The other results are in the form of stress intensity. Logically, it follows that we should compare stress intensity results to some sort of stress intensity allowable. This is where the Division 2 database comes in handy. As you also noted, not all materials in Division 1 are approved for use in Division 2.

To cloud the water even further, it may be that in the higher temperature ranges the allowables for materials in Division 1 may be higher than the Design Stress Intensities listed in Division 2. Note that in many cases the maximum allowed temperature in Division 2 may be lower than the maximum allowed for Div 1.

You can of course by pass the database selection and type in your own values in the hot and cold stress fields. Perhaps in the future it would be nice to have a database selction option in the CAESAR II Local Stress Analysis module.

I am wondering if the latest version of Caesar II corrected material database for Duplex stainless steel. I had pointed out twice that the material database(thermal expansion/elastic modulus) of Alloy 2205 in Caesar II was incorrect.

ASME B31.3 does not provide the thermal expansion/elastic modulus of Duplex stainless steel but ASME BPV Section II does it.

The material information for Alloy 2205 are;

Duplex stainless steel(UNS S31803)
1) Brand name : Alloy 2205
2) Material group in B31.3 : 22Cr-5Ni-3Mo (P-No. 10H)
3) ASTM Spec. No. : A789-S31803 or A790-S31803
4) Allowable stress in B31.3 : Table A-1.
5) Thermal coefficient in B31.3 : Table C-3 does not specify it for 22Cr-5Ni-3Mo
6) Caesar II material D/B : material # (339) and (340)----this may have wrong thermal expansion/elastic modulus.

I would use Div.1 allowable(Table 1A) for WRC 107 calculation in lieu of Div.2 even if vessel design/material specification is Div.2. If I check the nozzle stress with Finite Element Analysis instead of simple calculation, then Div.2 allowable(Table 2A) could be used.

Complex issues.

If you are qualifying an ASME B31.3 component by rules in other codes (e.g. flange design rules in Section VIII, Div 1, or detailed FEA per Section VIII, Div 2, Appendix 4), you are generally required by B31.3 to use the B31.3 allowable stresses.

However, a nozzle analysis on a pressure vessel would be per the pressure vessel code. If you do a detailed stress analysis of a nozzle for external loads using FEA or WRC 107 for a Div 1 vessel, what allowable stresses to use? It is my opinion that it would be most appropriate to use the Div 1 allowable stress for a Div 1 vessel.