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Dual Certified materials

Dual Certified materials

Dual Certified materials

When we use Dual certified material grades, what shall be the criteria.
SA 516 gr 60 / 70
SA 387 Gr 11 Cl 1 / Cl 2
SA 387 Gr 12 Cl 1 / Cl 2
SA 240 Gr 304L / 304
SA 316 Gr 316L / 316

1. Does it mean, for the raw materials, the Chemical Composition shall not exceed maximum limits of Lower grade and Mechanical Properties shall not be lower than minimum limits of Higher grade.
2. In case of Austenitic stainless Steels, when Lower allowable stress are required to be used in the Design of Tube sheets , Bolted Covers and Girth Flanges, does it imply that we have to use lower allowable stress of Lower Grade or can we use lower allowable stress of Higher grade?

RE: Dual Certified materials


2. In case of Austenitic stainless Steels, when Lower allowable stress are required to be used in the Design of Tube sheets , Bolted Covers and Girth Flanges, does it imply that we have to use lower allowable stress of Lower Grade or can we use lower allowable stress of Higher grade?

The Code captures this is in (I think) note G5. It's not obligatory/manadatory, but a cautionary note. Use at own discretion

RE: Dual Certified materials

Dual Certified material must meet the requirements of both specifications.
Once you pick a specification, stick with only that specification. Such as choosing 304 rather than 304L, forget about 304L and use 304 values only.
Basically it is only dual material until you choose which spec you are following.

RE: Dual Certified materials

You have to meet all of the chemistry restrictions for both grades (so the ranges must overlap) and the higher of the mechanical strength and the higher elongation/toughness.
In many cases minor distortion isn't an issue (HX tubes) so you use the higher allowable of the two.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Dual Certified materials

Thank you XL83NL / david339933 / EdStainless for you remarks.

However, the question especially for Austenitic Stainless Steel would be, when the Client specifies in their data sheets, lower grade MOC EX 304L or 316L and agrees for using dual grade materials, is it necessary to follow in Design, code allowable stress of 304L / 316L instead of that of 304 / 316.

RE: Dual Certified materials

I'm not certain dual certification be achieved with
SA-387 Gr 11 Cl 1 / Cl 2
SA-387 Gr 12 Cl 1 / Cl 2
ASME SA-387 is not specific on heat treatments, but I've always understood class 2 to indicate quench and tempered. Class 1 is the more commonly used condition by far.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Dual Certified materials

DK44 - Yes...the customer is choosing the spec for you. They choose 304L, use only 304L values.

RE: Dual Certified materials

Thank you david339933 (Industrial) for your understanding.
Having selected L Grade in such circumstances, in applying G5 rule as required by client, we have to use Lower allowable stress of L grade for the the design of the specific components in question, instead of lower allowable stress of normal grade. This leads to conservativeness instead of optimisation. But no choice.
Is my understanding OK.

RE: Dual Certified materials

I think you are mixing up G5 and the different specs.
Your client seems to be allowing you to purchase dual certified material, but is limiting your stress values to the 'L' specification.
Within the 'L' specification there are two listings. One has note G5, which are even lower stress values. These values are used for App. 2 flanges, UG-34 Flat heads with gaskets or other situations where small deformation may cause leakage.
If you do not have flanges or possibility of deformation use the higher stress values of the 'L' spec...ignoring the listing with note G5.

Edit: Upon reading your OP again, yes you are correct for the "specific parts in question".

RE: Dual Certified materials

Dear david339933.
Yes. There are two issues in case of Austenitic stainless Steels. Appear to have mixed up since they are discussed in parallel.
One is to select governing specification (either L grade or Normal Grade) and then applying note G5 for design of specific parts.
Thank you once again for your remarks.

RE: Dual Certified materials

Sometimes I specify steel to be purchased as A516-60 with modified yield and ultimate strengths equal to that of A516-70. That way, I get the toughness of A516-60 and the strength of A516-70. If I bought it as A516-70 the assembly would need thermal stress relief and future modifications are more involved.

RE: Dual Certified materials

We have some customers that order 4304/304L tubing and require the use of the G5 reduced stresses.
It moves the SF from 3.5 to 4 and they want the extra margin.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Dual Certified materials

I've seen pressure vessel (edit) and or shell & tube specs that mandate all SS / non-ferrous use lower allowable (G5) stresses.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Dual Certified materials

I thought it might help you mentioning the following:

Quote (ASME II-D Ed.2015 Table 1A. notes:)

G12 At temperatures above 550°C, these stress values apply only when the carbon is 0.04% or higher on heat analysis.
In the note above which applies to SA-240 304 (among other materials), using mechanical allowable stress values for dual grade 304/304L is permitted up to 550°C.
Since the spec. of SA-240 does not specify a lower limit for carbon content of grade 304, it is possible that a 304L and 304 overlap and hence dual grade is possible. however, if you are supposed to use it at higher temperatures than 550°C, in order to use 304 allowable stresses, the material shall have a carbon content of at least 0.04 which makes it impossible to use dual grade since the maximum carbon content for them is 0.03 and there will be no overlap between 304 and 304L in these temperatures.
So if for more resistance to corrosion and sensitization a lower carbon content is required (less than 0.03 per cent which is necessary for 304L), it will be necessary to check that the temperature does not exceed the above limit if a dual grade with allowable stresses of 304 is used otherwise use the stress values of 304L.

RE: Dual Certified materials

See following interpretation:

Interpretation: VIII-1-89-269
Subject: Section VIII, Division 1 (1989 Edition, 1989 Addenda), Table UHA-23, Dual Marking
Date Issued: January 9, 1991
File: BC90-256
Question(1): May dual stenciled 304/304L plate products with appropriate mill test reports be used as either 304 or 304L material at design temperatures of 1000°F and lower?
Reply (1): Yes.
Question (2): May dual stenciled 304/304L plate product with appropriate mill test reports be used as 304 material at design temperatures greater than 1000°F [Note (8) of Table UHA-23 applies]?
Reply (2): No.

See also mandatory appendix 7 on ASME-II-D.

Hope this helps.

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