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Re-rating MDMT of a non-carbon/low alloy steel

Re-rating MDMT of a non-carbon/low alloy steel

Re-rating MDMT of a non-carbon/low alloy steel

Hello all,

I am trying to find a section in ASME BPVC Section VIII Div. 1 that explains how to lower a pressure vessel’s MDMT (without impact testing) when the material is not carbon or low alloy steel. I’ve read UCS-66, UCS-67, UCS-68, Figure UCS-66.1, and Figure UCS-66.2 but all of those procedures are only for carbon and low alloy steels.

I’m trying to lower the MDMT of a vessel constructed from SA-240 316L by 5oF.

Also, from a curious engineer standpoint I would like to know how to lower the MDMT (without impact testing) for other materials such as other high alloy steels, or aluminum alloys.

Any experience for this situation would be greatly appreciated,


RE: Re-rating MDMT of a non-carbon/low alloy steel

First, ASME B&PV Code, Section VIII, Div 1 is a construction code and not an in-service code. Lowering the MDMT is an alteration, so you either follow the requirements of the NBIC or API 510.

RE: Re-rating MDMT of a non-carbon/low alloy steel

Second, learn the code...

Part UCS is specific to carbon and low alloy steels. If you want to look into the rules for other materials, read Parts UHA and UNF.

RE: Re-rating MDMT of a non-carbon/low alloy steel

Thank you for all of your help. I looked under UHA and UNF and found what I was looking for.

For anyone else looking for this information, I made a quick list summarizing what is in the codebooks (Minimum temperature without needing impact testing)

ASME B31.3 (2016)
  • austenitic stainless steel (w/o filler metal)
    carbon <= 0.1% -150F
  • austenitic weld metal (w/filler metal)
    carbon <= 0.1% -150F
    carbon > 0.1% -55F
ASME Sec. VIII Div. 1 UNF (2017)
  • wrought aluminum -452F
  • copper/alloys -325F
  • nickel/alloys -325F
  • cast aluminum alloys -325F
  • titanium alloys -75F
  • zirconium alloys -75F
ASME Sec. VIII Div. 1 UHA (2017)
  • austenitic chromium-nickel stainless steels
    carbon <= 0.1% -320F
    carbon > 0.1% -55F
    castings -20F
  • austenitic chromium-manganese-nickel stainless steels
    carbon <= 0.1% -320F
    carbon > 0.1% -55F
    castings -20F

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