Using the Higher Stress Value Material for Vessel Design

[neilbonner]

I have an ASME VIII Div.1 Cast Pressure Vessel SA351 Grade CF8M with integral flanged connections.

In ASME II Part D there are two listings for SA351-CF8M

The first has a higher Max. Allowable Stress Values, but an additional note G5 which states:

"Due to the relatively low yield strength of these materials, these higher stress values were established at temperatures where the short– time tensile properties govern to permit the use of these alloys where slightly greater deformation is acceptable. The stress values in this range exceed 662/3% but do not exceed 90% of the yield strength at temperature. Use of these stresses may result in dimensional changes due to permanent strain. These stress values are not recommended for the flanges of gasketed joints or other applications where slight amounts of distortion can cause leakage or malfunction"

My question is can I use the higher stress values for the Head, Shell & Nozzles and just use the pressure-temperature rating from B16.5 to cover the flanges as per UG-44?

Thanks
Neil

 

[SnTMan]

neilbonner generally speaking, I'd say you would be OK provided your flanges meet dimensional requirements and so forth of B16.5.

Regards,

Mike