SA-688-316L Composition Conundrum

[SnTMan]

Hello All. I am looking at some "legacy" drawings, whch we will use to build some more or less duplicate units to a new specification.

The tubing, per SA-688-316L, and the tubesheet (SA-182 F316L)are called out on existing drawings as 0.05% max carbon. The new spec has no such requirement, so my thinking was to change this callout to relect what is permitted by the material specs.

While I have not researched SA-182 yet, I find for the tubing that per SA-688, product tolerance is per A-480, unless C is 0.04% or less, in which case it does not apply. Per A-480, Table A1.1 does not apply to heat analysis.

I do not know whether the supplier will perform heat or product analysis, although I will check to get their take on this situation.

So, per the applicable specs, is there any upper tolerance on carbon content? If so, what would it be?

Thanks in advance,

Mike

 

[metengr]

The SA 182 standard specification lists the maximum carbon content for F316L as 0.030% max.

 

[SnTMan]

metengr, what's your opinion on the tubing?

Thanks,

Mike

 

[metengr]

Mike;
The ASME SA 688 standard specification states that a test report shall be provided to the Purchaser. The test report shall contain the heat analysis, hardness and tensile properties.

A product analysis can be performed, but it must be specified on the PO by the Purchaser. The tolerance for product analysis does not apply for carbon contents at or below 0.04%.

Since the 316L tubing is stated to have 0.035% max carbon, this is the maximum value.

 

[SnTMan]

OK, taking another look at the original docs, the materials were straight grade, with limited carbon. They are now L grade with carbon, per the materials specs, lower than the callout for the straight grades. I feel safe in just dropping the max carbon callout of 0.05%.

Agree/disagree?

metengr, after looking at SA-182 I agree that no upper tolerance exists for carbon. Thanks for your help with this.

MIke

 

[NozzleTwister]

In my opinion, if your original materials were straight grade with limited carbon content, your allowable stress values were for straight grade materials.

If you simple switch to "L" grade materials, you'll have lower allowables and will need for verify the orignal design is still OK.

I would not just blindly duplicate with out qualification of the design at the lower allowables.

NozzleTwister
Houston, Texas

 

[metengr]

Agree with the above, including reviewing the design using the lower allowable stress value from ASME Section II, Part D. for low carbon grade.

 

[SnTMan]

NozzleTwister, metengr, you both are right, the lower allowables will be accounted for. The change in grades is a customer requirement. The old job had a god-awful set of notes for tubing requirements, while the new one has a new and different god-awful set of notes for the tubing requirements.

The old job had some extended verbiage for UT of a cup forging, while the new job has some new and different extended verbiage for the UT.

I am hoping to get this cleaned up so that when we go to buy materials we don't have requirements that don't make sense or can't be met.

Thanks again

Mike