Applies To
Product(s):	AutoPIPE
Version(s):	2004, XM, V8i, CONNECT;
Environment:	N/A
Area:
Original Author:	Bentley Technical Support Group
Date Logged & Current Version	Aug. 2016 10.01.00.09

Problem:

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)

or

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?

Solution:

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

The allowable in Section NC 3655(b)(3) = 70 % (3 * Sh) = 2.1 Sh, OrAllowable = 2.1 Sh Allowable = 2.1 (Design Sh) Note: because the dialog Allowable Case for Sh = Design selected, the design Sh was used in this calculationAllowable = 2.1 (16280 psi)Allowable = 34188 psi Same as shown in output report, AutoPIPE is calculating the allowable correctly. Note: This information is detailed in the following AutoPIPE help section:Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations> Level C Service Limits> NC - Level C - Including Reversing Dynamic Loads

See Also

ASME BPV-III-1-NC, AutoPIPE Nuclear Piping Code FAQ

Bentley AutoPIPE

External Links

Bentley Technical Support KnowledgeBase

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