SA 516 grade 70 4

[lganga]

Hi

WE have to do a but weld patch on a vessel
The vendor ddid not send the analysis of the specifcic part, only the fabricator analysis.
Can we trust in a chemical analysisi of this part and a hardness test as a way to compare the data with the ASME II data
What is the tolerance we have for every grade, for the Carbon percentage?
regards

 

[metengr]

As long as you have traceability with the vessel material, you do not need to perform a specific chemical analysis. Hardness testing is fine and will provide information as to the approximate strength level of the vessel material. There is no hardness requirement for SA 516 Grade 70.

 

[lganga]

That is right, we do not have traceability.
We did the chemical analysis of C,Mn,Si-
Carbon analysis is 0.24% but fo 16 mm thickness, ASME II figure for Grade 70 a 0.28%.
So the question was if we have some tolerance in the Carbon %.
We used hardness test as a way to have an approximate value of its a resistnace by conversion of Hv in Tensile strength.
The other two elements are in the tolerance

 

[metengr]

Ok, I was confused by your OP. If you have the actual chemical analysis of the pressure vessel steel, and compared with the min and max % by mass in the specification, there will be a tolerance. Your carbon content falls below the maximum for SA 516 Grade 70, and this is acceptable.

 

[SNORGY]

metengr,

For my own edification, does the ASME Code or do local regulatory authorities accept the extrapolation from hardness values to tensile properties, or to notch toughness properties? I would think that an engineering assessment would need to be made and probably professionally endorsed, but I don't know the ins and outs of the Codes well enough.

I would also initially have thought that you need to formally re-certify the unknown material to whatever you are actually trying to requalify it to (i.e., prepare a material certificate for it).

 

[metengr]

SNORGY;
Yes, in general. For in-service vessels you have two Code options - NBIC and API 510. From these two in-service inspection, repair and alteration codes there is what I call technical leeway regarding characterization of materials and associated properties. As an example, API/ASME Fitness For Service (API 579) which is referenced by both codes provides assessment levels in evaluating remaining useful life and in-service damage. Re-certification of material is typically unnecessary once a vessel has been placed into service, while during construction certification is required. However, once an object is placed into service characterization of material could become necessary for establishing weldability and/or notch toughness, especially for outdated material. The Code recognizes that original material may not be available so one must attempt to select a material grade similar to the vessel material if weldability and notch toughness testing are required.

From my involvement with several Jurisdictions both from a code consulting view and owner’s viewpoint, an engineering assessment is typically submitted to the Jurisdiction and in most cases requires endorsement by a licensed professional engineer. On the State board of which I am a member representing high pressure boilers, we as a board require submittals with engineering assessments and endorsements for State Specials (vessels not built to ASME Code or were exempt from ASME Code and are now requiring Operating Certificates).

 

[SNORGY]

Thanks metengr, that makes sense to me now.
I was involved once, two and a half decades ago, with trying to get an unrecognized forging qualified as a set-on nozzle for an aerial cooler header box. The cooler had not been fabricated yet, so that is probably why the certification of the nozzle material had been enforced. I was too inexperienced at the time to understand the details of the Code, and have not faced a similar situation since.
I'd give your post two stars if I could. Thanks for the explanation.

 

[lganga]

Thanks for your answers

I will write my interpretation about ASMEII specification for A 516.

For me, every grade has its % of C,
For example a 16 mm thickness plate (my case) has, for grade 70, a 0.28% in weight of Carbon.
As I know, there is a direct relationship between Carbon content and mechanical resistance (if the others variables are fixed).
Then for me a 0.24% C (my chemical analysis) is closer to a grade 65 instead of grade 70.

How can I we sure if my plate is grade 70?.

According to mechanical properties the Standard says that they can be between 485/620 Mpa. Then if I see the table for mechanical porperties, the minimum tensile strength for grade 70 (485)is covered by the 3 grades in their ranges.
Then other variable to check should be the chemical analysis.

Can you explain me the criteria to have for getting the grade of a steel using chemical and mechanical properties?.
Oru

ur vessel is a grade 70 and the patch I asked for was bought as grade 70, and the thickness is in accordance to this grade.
That is the reason why I want to be sure that my plate has a grade 70 .

Sorry for this long post.
I hope you can answer me
Luis

 

[metengr]

lganga;
According to the SA 516 material specification, Grade 65 for 16mm thickness has a maximum limit of 0.26% carbon by mass. For Grade 70, 16mm thickness the maximum carbon content by mass is 0.28%.

You have 0.24% reported so this could go either Grade 65 or 70. What were the hardness results of the material? This may help to determine if you are on the high end of the ultimate tensile strength as approximated.

Otherwise, in order for you to conclusively determine a particular Grade you need to have tensile testing performed and evaluate the yield strength, this is the determining factor, and not specifically carbon content because these values are maximum reported, not minimum.

 

[lganga]

metengr
Thanks for your answer
Here are the hardness data for the vessel and pad plate.

As medium values

Vessel hardness 142 Hv (20 values)
- Tensile equivalent 470 Mpa

Patch plate (to be welded) 139 Hv (10 values)
-Tensile equivalent is 465 Mpa

Tensile test is required
But this information gives a plate closer to Grade 65.

Luis

 

[metengr]

lganga;
Let me back up a moment to ask the following. If you intend to repair this pressure vessel using a flush patch repair method, the patch plate material needs to be supplied with material test reports in accordance with SA 516.

Do you have the material test report for this patch plate or some means of traceability to the material test report? If you do not have the test report, how do we know this is even SA 516?

If the test report is unavailable, I would reject it for use because you do not have the necessary traceability to ensure compliance with ASME SA 516.

Having the chemical analysis of the vessel and hardness are fine for information purposes. When is comes to ordering material for repair, this must be in accordance with the requirements of the material specification.

 

[lganga]

metengr
here attached is the certicate we got from the vendor,but we do not the traceability of the part they cut.
Regards

 

[metengr]

lganga;
So in other words, they did not transfer the mill markings or provide a marking for the plate section that was cut for traceability back to the mill test report? If this is the case, other than re-testing what you have in your possession, I would reject the plate material and have them send another patch plate with markings that traces back to the above mill test report. The other option is to have the supplier provide you with a Certificate of Conformance indicating they have removed the plate from a plate that has mill markings for traceability back to the above test report.

 

[lganga]

metengr

I apprecciate a lot your comments.
I have the supplier certificate of Conformance.

Regards
Luis

 

[JStephen]

I would like to point out also that the various grades overlap in the allowable strength and chemistry ranges, so you can't necessarily define for certain which grade a material was actually produced to based on testing.

 

[stanweld]

SA-516 requires plate testing for tensile properties. Apparently there is no way to confirm which plate tensile tests correspond to the plate furnished. Agree with metengr. The certificate of conformance must define the plate from which your purchased plate was removed. We had a similar problem on a Joint Review for ASME Code Certificate Renewal. It was resolved by NCR on the material and essentially resolving as above.

 

[lganga]

JStephen.

WE are testing the plates that we have received, Syield and Sstrength will be defined.
We have already done the chemical analysis.
We have the test hardness of all the píeces, including the vessel to be welded.

- With chemical analysis: We have the certainty about the Cequivalent, then the weldability.

- With mechanical test: We know the Syield so at least I can be sure about the Sallowable. (two tests for every plate)

- With hardness test.we can verify the correlation between Hv and the table conversion to Strength.


I think that this are part of the steps to get the actual information of the plates to be welded to the vessel.
As we have recieved the certificate from the vendor, about the ASME II compliance an the parts where the plates were cut off. We think the local inspector can satisfied his doubts about the traceability and will accept the plates .

Thanks for answers
Luis