MDMT of A36 Plate

[merton]

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

 

[JStephen]

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.

 

[IFRs]

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".

 

[TankDude]

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".

 

[gdubyuh]

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.

 

[TankDude]

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?

 

[IFRs]

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.

 

[JoeTank]

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

 

[JStephen]

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.