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MDMT of A36 Plate

MDMT of A36 Plate

MDMT of A36 Plate

(OP)
Can A36 plate be used for a storage tank when MDMT is stated as -20F or is additional testing of material required.

What is the MDMT of A36 Plate?

Thank you

RE: MDMT of A36 Plate

In API-650, there is a chart showing minimum metal temperature without impact testing as a function of thickness.  I don't think it goes down to -20 for regular A36.

You can also use A36-mod, which lets you use it at lower temperatures.

Also, I believe, Appendix A lets you use A36 down to -20 F.

I don't think API 12F or 12D consider design metal temperature.

RE: MDMT of A36 Plate

According to the chart in API 650, A36 or A36MOD can NOT be used at -20DegF Design Metal Temperature for any thickness.  Appendix A specifically limits the temperature of A36 and A36MOD (Group I and II) materials to above -20DegF.  Please be clear of the definition of "Design Metal Temperature".

RE: MDMT of A36 Plate

If the MDMT is specified or shown on Fig. 4-2 as -20 Deg. F. then you can add 15 Deg. F to that, for a value of -5 Deg. F, at which (by my interpretation) A36M would work for thicknesses less than about 5/8".

RE: MDMT of A36 Plate

I thought that if the MDMT is stated on a tank data sheet, then that is the MDMT that is adhered to.  If no MDMT is stated, then you can use API-650, 11th Ed.,  Fig. 4-2 to determine the MDMT as 'lowest one day mean temp + 15 degrees'?  

I don't know if this is expressed in API-650, but it is stated in API-620, 10th Ed., 4.2.1.2.

RE: MDMT of A36 Plate

You could be correct gdubyuh.  Now that I have looked in the 11th Edition, it appears that this provision has been removed.  It was Section 2.2.9.5 in Add. 4 of the 10th Edition.  Section 2 became Section 4 in the 11th Edition, and there is no 4.4.9.5.  Does anyone have any input on this?  Is it in another section that I'm not finding?

RE: MDMT of A36 Plate

The API 650 11th edition is no different from the 10th edition in this respect.  Minimum Design Metal Temperature equals Lowest One-Day Mean Temperature plus 15 DegF.  See section 3.4 in the 11th edition.  Note: this is without impact testing.  See section 4.2.9 if you want to use the material below it's MDMT.

RE: MDMT of A36 Plate

It sure gets confusing when we mix terms from other Codes and Standards.  MDMT is an ASME term and DMT is an API term.

Joe Tank

RE: MDMT of A36 Plate

Just checking the wording in Appendix A, and I see it lets you extend that range to -40 when killed fine-grain materials are used.

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