Can any one help me on following
1)What Is MDMT and Its enfluence in design calculations?
I would also like to know method to calculate MDMT of any Metal as per ASME

Hello manojkumar
MDMT is obviously minimum design metal temperature.It is the lowest temperature upto which that particular material can be used without impact testing.It means it should not be more than minimum design temperature.
MDMT can be calculated as per UCS-66 of ASME Sec VIII div 1.As per the relevent curve(A,B,C or D) of the material used and the nominal thickness of shell/head,the graph gives MDMT on y-axis.
Regards,
Abhijit Dutta

Hi abhijit
just a comment, depending upon process, engineer will select MDMT for the equipment. At that particular value, one can check from UCS-66, if impact test is required

Hi jack
thanks for the comment.For more clarity to manoj it is like that.
Due to process reason if the minimum temperature is going below MDMT then impact testing is required.
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abhijit

Thank you all for your kind attention.

Regards

Hello folks

When low temperature is to be encountered, and the material of construction is carbon steel (eg: SA 516 70) remember to order it in the normalised condition - especially if it is over 1/2 inch (12 mm) thick.

Dear Ray Delaforce,

Whats the adantage of ordering carbon steel material in normalised condition for low temperature application.

Mahesh
maheshpatelgg@yahoo.com

Hello Mahesh

If you look at ASME Section VIII, Division 1, paragraph UCS-66 and the accompanying graph you will see the advantage. Graph USC-66 has four curves labeled A, B, C and D. If you have a material that qualifies as a curve D material, you can see that it can be subjected to a lower temperature than a curve A material. Let us look at an example.

Suppose we have a 1 inch thick plate. If treated as a curve A material, we can go down to 68 degrees F before impact testing is required. But, if the 1 inch plate can be treated as a curve D material we can go down to minus 30 degrees F before impact testing is required.

The lowest temperature to which a component can be subjected is called the MDMT or: Minimum Design Metal Temperature.

Now, an SA 516 70 plate in the un-normalised condition can be treated as a curve B material. If the plate is normalised, it can be treated as a curve D material.

To avoid having to impact materials, it is better that the MDMT of the material is lower on the UCS-66 graph.

Can anyone tell me why stainless stell material can go for very low temperature servise? and how low it can go, which paragraph in ASME code book should i look for it?

Thanks

Hello eveyone,

Is MDMT really relevant for SA-321 material? and what one should do to remove the error if it's coming below the specified value (-29 C in my case).

Ankit