ASME B31.3 û Restrictive Temperature Limits of CS Materials Listed in Table A-1 1

[auzie5]

Is there any way to de-rate the MDMT of A105 material used for flanges or valve bodies in B31.3 piping systems? B16.5 and B16.34 both restrict A105 to -29 deg C in their respective Pressure-Temperature charts and B31.3 Table A-1 also limits the min. temp. to -29C.

I am aware that for some materials (ex: A106 Gr. B), the MDMT without requiring impact testing is a floating value depending on the material thickness and stress ratio (see B31.3 Figures 323.2.2A/B); however, it has always been my understanding that for materials such as A105, the MDMT could not be adjusted below the values published in the specs/standards listed above.

Is this assumption correct or is there a way to de-rate the MDMT for A105 down to M45C?

Thanks in advance.

KDW

 

[metengr]

ASME Section VIII, Div 1 allows for a reduction in MDMT for flanges based on MAWP and rating of the flange, it would appear B31.1 does not provide for this approach.

 

[auzie5]

Thanks for the heads-up metengr. I had a feeling that Section VIII might provide some flexibility not permitted by B31.3 but figured it would be in Div 2. Can you reference the ASME Section VIII Div 1 clause?

Thanks again,

KDW

 

[metengr]

Yup, see the thread below;

thread794-354475

 

[auzie5]

Very helpful! Thanks metengr.

Still hoping to here back from anyone with an opinion on applying or restricting the same approach in a B31.3 piping system.

KDW