Hi all,

a question about the material database in PVElite.
I'm modelling equipment made out of A312 TP316H for the tubes and A182 F316H for the flanges.
According to both ASME II part D and ASME16.5 these materials can be used up to 1500 F. My design temperature is 780 degrees C (1436 F).
When selecting one of the two materials listed above PVElite gives the following warning:
"The temperature was beyond the limit for this material's maximum yield stress value."
When I click the ...-button behind the material name in the element data and then click Yield stress I only get a T vs. stress overview to 537 degr. C.
What am I doing wrong here? I expect the material to be usable up to 1500 F, not 1000 F. Am I selecting the wrong material or is there something else I missed?
Also strange imo is that it gives a warning about calculating with 1.5 x the operational stress, but that same warning is nowhere to be found in the output.

Corne,

You are not doing anything wrong. If you refer to Section II Part D table Y-1, you will note the maximum temperature in the table for which yield stresses are listed is 1000F. There are also some materials that do not even have listings of Yield vs. Temperature. So when a material comes back with a value of zero for the yield stress at temperature, it is assigned a conservative value of 1.5 times the operating allowable stress.

For flange design in ASME, the allowable stresses are used as well as the Elastic Modulus for the material. Luckily, the yield stress is not used. For SA-182 F316H and similar materials, please note Note "G5".

Scott,
thanks for your answer so far.
Still a question:
You say that flange design in ASME doesn't use yield stress, but only allowable stresses. Still you look for the yield stress range in table Y-1 although you don't use these values.
Checking ASME VIII appendix II chapter 2.3 Sf is according to UG-23. UG-23 derives the allowables from table 1A. Table 1A has a maximum T of 1500F.
Why exactly do you check the yield stress table but calculate using the allowable stress table? And why the factor 1.5? Is this regulated in ASME somewhere?
If I check the PVElite output it has an Sfo of 12.89 N/mm2 which is according to Table 1A. I can't find the factor 1.5 in the output. Can you point me to it?

Corne,

You are correct that PV Elite always trys to look up the yield stress whenever a material is selected. If the yield stress is available from the table, then of course we use that value, if it is not we go the conservative route. To understand the use of the 1.5 factor, you should review Table 1-100 on page 877 of Section II Part D (2007 ed). Please note that 1.5 is the reciprocal of 2/3rds.

You are also correct that the yield stress is not used in all calculations, but it is used in some. When the program is retrieving information from the database, this value is obtained with all of the others. Once the yield stress is obtained, the 1.5 is no longer needed and therfore you will not find a yield stress calculation in the output.

Scott, thanks again, but still some questionmarks here.

I've opened the material database and clicked the edit coade material button. The values I saw looked like the allowables table A1 to me. Where exactly does PVElite search for the yield-stresses?

I'm not at work atm and don't have AMSE within reach, so can't check the table 1-100 atm.
Does PVElite have 2 tables, one with Yield (Y1) and one with allowables (A1)? And if no yield (table Y1) is found, it takes the allowable (table A1) multiplies it by 1.5 to get the approximate yield and than corrects it to maximum allowable again (which gives me the value of A1 again)?

Corne,

Yes, there is a separate database of yield stresses that includes the data from Table Y-1, up to 1000F as you noted. If the material is not present in Y-1 or the temperature is exceeded, then you will get the note during the time of material selection and the yield at operating will be approximated as 1.5 times S. Please note there are two distinct bits of information being stored, the yield at temperature and the operating allowable stress. For design of most components, the allowables are used, but in some cases the yield stress values are used.

OK, starting to understand it now.
And the table I can edit and or add is just the allowables table?
Thanks for the explanation.

Corne,

The stress tables that are provided with the software are not editable. You can only view the information. However, using the database editor you can add materials. Currently there is no tool for adding records of Yield Stress vs. Temperature to the yield stress database.