MDMT for duplex stainless steel

[aard]

I want you to help me how to select an MDMT for a duplex stainless steel SA-182 according to Sec VII div 1. When I have a carbon steel is easier to me but when I go to part CS but in this case I'm a little lost when I go to UHA. Which parameters of the design I need to know the MDMT?

As you can see I'm a little lost but I want to hear your comments.

Thanks

 

[metengr]

The minimum design metal temperature is the lowest service temperature anticipated or expected under design conditions. Once this value has been established, you determine if the proposed material requires impact testing per ASME Section VIII Div 1 requirements.

 

[aard]

but can I stablish this factor under SEC VIII div 1 o just for process data?

 

[pdiculous963]

Take a look at nonmadatory Appendix JJ of Sec. VIII-1 for flowcharts to help with the high alloy toughness rules. For duplex stainless steels, in my experience, there are very few cases where impact testing is not required. The vessel either needs to be very thin or under very little stress.

 

[aard]

Mmmm ok ok let me check. by the way my main doubt is about impact test for a tube sheet, my thickness is 2,874" the material is SA-182, MAWP 151 psi, design temperature 151°F, the MDMT I picked first is 32°F but I Know is high for duplex (I pick this value because was the original MDMT for a CS tubesheet but the tubesheest is required in duplex ss). My conclusion is that I will need impact test but I want to solve first my doubt with MDMT.

 

[metengr]

aard;
Forget about duplex ss for the moment, is 32 deg F the lowest expected exposure temperature (aka MDMT) in service?

 

[aard]

Yes, this was the MDMT when the tubesheet was in CS but now is duplex and this should cange, inst it?

 

[aard]

change*

 

[aard]

or this is not a necessary scenario?

 

[metengr]

No, it should not change because this is not a material issue it is a design variable. So, now you have your MDMT, you determine if your proposed material requires impact testing.

 

[aard]

When you say is a design variable you mean that is a process design variable? because the mechanical design is changing when I change the original material to other with different metallurgy

 

[metengr]

Process design variable.

 

[aard]

good. Thanks

 

[SJones]

Irrespective of MDMT and code requirements, Charpy test the stuff anyway for quality control purposes - review ASTM A923 and NACE Corrosion 2012, Paper 2012-1096. At that thickness of material, I would be recommending a NORSOK M-650 qualification of the manufacturer, incorporating fracture toughness testing for use in an engineering critical assessment.



Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[weldstan]

AS Steve stated, Charpy test the material for determining appropriate characteristics/quality of the material - not because of the MDMT determined for the material due to the process/service conditions.

 

[EdStainless]

While A923 is not a test for the sake of impact toughness, it does use low temp impact to demonstrate that the material was heat treated correctly.
All duplex stainless should be tested to A923, thick material can use the impact test and thin material the corrosion test.
You may want a second impact test at a higher temp than A923 requires to use as a basis in the design.

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P.E. Metallurgy, Plymouth Tube