In an example model with SA312 Gr TP304 piping material with specific design and operating temperature as 640 degrees F. The properties are properly shown as:
Sh = 16280 psi
Syhot = 18080 psi at 640 degrees
Sc = 20000 psi
Sycold = 30000 psi.
When looking at the output results for Stress summary Level C the allowable stress is calculated to 34188 psi (2.1 * Sh). Why?
According to ASME NC 2007, NC-3654.2(a), should be the min of:
2.25Sh (2.25 * 16280 = 36630 psi)
1.8 Sy (hot) (1.8 * 18080 = 32544 psi).
Therefore, the allowable should be 1.8Sy (at temperature) = 32544 psi.
why is the Allowable 34188?
AutoPIPE is working correctly.
First note the Stress Summary dialog settings:
a. Reversing Dynamic loads is checked ON.
b. Allowable case is set to Design
Let us review the code:
Note: above images are excerpts from ASME NC-2007
ASME BPV-III-1-NC, AutoPIPE Nuclear Piping Code FAQ
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