UCS 66 1

[dungun]

Hi
I have 16mm SA516 gr 70 N, And specify the MDMT as -50F, but my fabricator say MDMT shall be at -48F only based on UCS66 chart. Fabricator refuse to put -50F as MDMT. Mechanical Consultant say fabricator confuse on the UCS66 meant for Impact Requirement. Which is correct??

 

[metengr]

UCS-66 of ASME Section VIII, Div 1 is meant to provide guidance for impact testing of materials and exemptions to impact testing of materials based on service temperature. Minimum Design Metal Temperature (MDMT) is established by the designer, and materials are selected to meet this temperature using UCS-66.

For your case, the minimum temperature for exemption to impact testing based on my review of Curve D in Figure UCS-66 is approximately -43 deg F. Lower service temperatures for this material require impact testing.

 

[dungun]

Hi metengr
If that material SA 516 Gr 70N, have been Impact Tested at
-50F then the MDMT -50F is correct.and can be used. right?.
Thanks

 

[metengr]

If the material meets the minimum impact test requirements for use at -50 deg F, yes it can be used.

 

[Cluain]

One must always remember when dealing with lower temperatures, to take advantage of Fig UCS66.1 if possible.
Using it in conjunction with fig UCS 66 will surprise you sometimes. Note, you may want to look at UCS 67 there's a nice exemption for welds there too.
Regards.