Using Yield/Tensile results from MTR's in piping/vessel stress design 1

[alsy]

Hello All,

I vaguely recall reading a document awhile back that stated in piping design one could use actual MTR yield results uo to 20% above the given specification for the material in question. I have since tried to locate this in the BVPC/B31.8/B31.3 to no avail. Assuming applicable specifications are met for given material, does anyone know of any code reference that lets the designer use a higher yield (supported by the MTR) than specification in design for any of the ASME codes?

Thanks!

 

[LittleInch]

I think you haven't found it because it doesn't exist.

31.3 has a set of allowable stresses (Table A1). There was a question (interpretation 23-19)

Question (1): Does ASME B31.3-2010 require the use of allowable stresses shown in Table A-1?
Reply (1): Yes.

Seems pretty clear to me. I can't see any reference to any clause or note saying if you test it you can use the higher figures.

Similarly B 31.4, which calculates allowable stress levels by using a factor on quote "Sy = specified minimum yield strength of pipe material, psi (MPa)" has a clause in 403.1 saying "In no case where the Code refers to the specified minimum value of a physical property shall a higher value of the property be used in establishing the allowable stress value."

Again seems pretty clear to me.

The only thing I've seen is whether the material can be officially re-classified by the vendor as a higher SMYS based on his set of tests, but that is up to the vendor to show that the material passes ALL the criteria for the higher rated material, not just yield stress.

The fact that most materials will have higher actual yields than the SMYS is effectively allowed for in the design codes and design factors and to start messing about with it can be very dangerous. If you've already bought the material and then some other calculation or analysis shows you are marginally over the allowable stresses (e.g. 102% of allowable), then you might be able to justify this in a report to be approved by the client showing that in actual fact the lowest value of yield stress is actually more than this, but that's about it as far as I know.

Your vague recollection maybe?? that B 31.3 allows up to 20% above the design pressure for certain lengths of time, both as a single occurrence (50 hours) and a total of so many hours over the year (500). See 302.2.4

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[alsy]

Thanks for the quick response LI...have a great weekend!

 

[BigInch]

LI is right. Nothing above the pipe's specified min yield strength, as stated in the purchase requisition.

you must get smarter than the software you're using.

 

[alsy]

Thanks BI...have a nice weekend.

"Success is not final, failure is not fatal: It is the courage to continue that counts."
Winston S. Churchill