Dual Certification Materials - What to use in Calculations? 1

[dalea60]

When your actual material has Dual Certification, such as SA-240 304/SA-240 /304L, how do you decide whether to select allowable stress in Section II-D for SA-240 304 or SA-240 304L?

Dual certification is coming up more and more since in reality our inventory consists of the same material under two part numbers, one for 304 & another for 304L.

Thanks,
Dale

 

[marty007]

I could have sworn there was a code section that addresses this, but I couldn't find it in my 1-min search.

In general, you must be consistent. If you use dual certified materials, you can treat it as either material, but you must be consistent in your choice. If you use the higher allowable stresses of the 304 straight grade, then all of your procedures and material tracking must ensure that 304 is being used.

For example, if our customer has specified 304L and we want to utilize the higher allowable strength of 304 by using dual certified materials, the way our AI and our ASME auditor has indicated we should proceed is as follows:
[ul]
[li]In the calculations, we use the higher allowable stress values of the straight grade SA-240-304[/li]
[li]In the BOM, we list the straight grade SA-240-304[/li]
[li]On the drawing, we add a note indicating that all materials must be dual certified 304/304L for weldability/corrosion resistant properties of 304L[/li]
[/ul]

We used to put 304/304L directly in our BOM, while using 304 grade in our calculations/fabrication. There is nothing per-se wrong with us building the vessel this way as long as our purchasing department understands it must be dual certified, but the ASME auditor didn't like the potential issues that this could raise in the future. If someone wants to repair the unit, and reads the BOM as though they can use either 304 or 304L, and procures straight grade 304L, then they are no longer in compliance with the calculations that depend on the higher allowable stress of the dual certified 304/304L. You should qualify the BOM is some way as I described above.

I hope that's clear.

 

[jte]

I think marty007's post is pretty clear. There are some prior discussions around this on E-T as well, for example thread404-212268.

Recognizing that Code Interpretations are not "code" directly, you should probably take a look at Interpretation VIII-1-89-269.

 

[dalea60]

marty007 & jte,

Thanks for the replies.

If we change our part number description to indicate dual certification 304/304L then the BOM is going to show that. It hadn't been discussed but having the drawings note dual certification is required makes sense.

Thanks,
Dale

 

[bayardwv]

We do as marty007 explains, calculating as straight grade, calling out the material on dwg as straight grade, with a note the part must be dual grade.
See ASME Section VIII Div.1 UG-4 (a) and UG-23(a)

 

[GenB]

Guys. What about when the customer's p.o. calls for say 316L so it should show in the ASME Data Sheet as 316L. I think that not on all cases you have the luxury of calculating to a higher strength grade and get away with it. Awaiting...

 

[Don56]

Remember that the Code sets minimum standards. If the customer further restricts the requirements, so be it. If they want the design to a lower stress factor they will pay for a heavier vessel. Discussion with the customer is always a good thing for clarifying the details.