| Applies To | |||
| Product: | AutoPIPE | ||
| First Affected Version: | 09.01.00.xx | ||
| Found in Version: | 11.00.00 | ||
| Fixed and Released in Version: | 11.03.00.00 | ||
| Area: | All | ||
| Severity: | Critical | ||
| Backlog Issue Number: | 798781 |
Behavior
• Severity: 1 - Critical
• First Affected Build: 9.1.0
• Affected Product: AutoPIPE
• Affected Versions: Nuclear
• Affected Piping Codes: ASME NC and ASME ND
• Program Affected: Yes
• Program Help Affected: No
• Documentation Affected: No
Reported Description:
The following equation is provided by ASME NC and ASME ND for allowable stress calculations of Equation 11 (NC-3653.2):
Sh + SA
Explicit definition for Sh is not provided under section NC-3653.2 Thermal Expansion. However, section NC-3611.2 Sress Limit clause 4 (e) provides the following definition for Sh:
Sh = basic material allowable stress at maximum (hot) temperature
For determining Sh value, AutoPIPE incorrectly uses the allowable value at the temperature corresponding to the selection made for “Allowable case for Sh, Sy in Eqn. 9” on the stress summary dialog. Program should instead use allowable value at the maximum temperature from across all equation 11 combinations. In cases where allowable value for the selection made for “Allowable case for Sh, Sy in Eqn. 9” is higher than the minimum allowable value from all equation 11 combinations for the stress summary, the reported equation 11 allowable value can be higher than the correct allowable value leading to unconservative results.
This error impacts all the editions of ASME NC and ASME ND piping codes.
Steps to repeat:
To illustrate this defect, the following scenario can be considered:
Step 1: Create a new ASME NC 2007 model with English units having two thermal/pressure cases
Step 2: Define a new pipe identifier STD12 with the following properties:
Nominal Diameter 12.000
Schedule STD
Pipe Material SA106-B
Cold Allowable 17,100 psi
Step 3: On the “Operating Pressure & Temperature” dialog that appears, enter temperature value for case 1 as 680 deg F (Hot allow = 16,200 psi) and case 2 as 700 deg F (Hot allow = 15,600 psi)
Step 4: On the “Design Pres & Temp” dialog that appears, enter a Design Temperature value of 700 deg F
Step 5: Insert an anchor at point A00 and attach a run pipe to the anchor using pipe identifier STD12 defined above
Step 6: Analyze the model and invoke the stress summary dialog
Step 7: Create a new stress summary with the following selections:
Service Level A
Allowable case for Sh, Sy in Eqn. 9 Ambient
Equation 8 Combination 1 Gravity {1}
Equation 9 Combination 1 Gravity{1}
Equation 10a Combination 1 Thermal 1{1}
Equation 10a Combination 2 Thermal 2{1}
Step 8: Take out the stress summary report output
Equation 10a allowable should be calculated as below:
SA = 1.25*Sc + 0.25*Sh = 1.25*17,100 + 0.25*15,600 = 25,275
Where the value of Sh (15,600) is taken as the allowable at the maximum temperature from all the load combinations listed for Eq. 10a. Notice that the allowable value of 25,275 is correctly reported under Eq. 10a.
Equation 11 allowable should be calculated as below:
Eq. 11 allowable = SA + Sh = 25,275 + 15,600 = 40,875
However, the program incorrectly reports the allowable value as 42,375.
Evaluation Criteria:
The following considerations are provided to assist in your evaluation of the potential impact of this defect on the results:
Evaluate whether this defect has affected any existing models by considering the criteria below:
1. Was the model created or updated in program version 9.1.0 or later?
2. Was the selected piping code ASME NC or ASME ND (any edition)?
3. Was there a stress summary defined in the model?
4. Was the allowable value for the case selected under “Allowable case for Sh, Sy in Eqn. 9” different than the minimum allowable value from all combinations defined for equation 10a?
A 'No' to one or more of the above criteria means that this defect does not affect the model’s results. No further
consideration for this model is necessary.
Workaround:
Enter the correct allowable value for equation 11 under the User Allowable tab of code combinations dialog.
Corrective Action Plan:
Use the minimum hot allowable value from all the combinations selected for equation 10a for calculating Sh value.
Additionally, to assist in the screening of the models created in previous program versions for any potential impact by this defect, the program shall automatically examine the model database after opening the model and generate a report (model name + "_798781.TXT"), listing the stress summaries with equation 11 allowable results potentially impacted by this defect. The program shall display the following confirmation message:
“Equation 11 allowable stress may be reported incorrectly due to a previous program defect #798781. Would you like to review the evaluation report?”
The contents of the critical error report shall be like the following sample critical error report:
Defect #798781 Evaluation Report
--------------------------------
Model Name: TEST1
Model Version: 09.06.02.06
Program Version: 11.03.00.20 01
Report Filename: TEST1_D798781.TXT
--------------------------------
For ASME NC and ND Equation 11 allowable calculations, program may incorrectly use allowable value for the case selected for equation 9 allowable calculations due to a previous program defect #798781. Please refer to the published defect report for more details, mitigation conditions, and instructions. To assist in the screening of this model for any potential impact by this defect, program has examined the model database and has found that equation 11 allowable stress values for the stress summaries listed below may be incorrect, and should be re-computed using this program version. After saving this model or running any analysis in this version or later commercial release versions, this screening will no longer be performed.
Stress Summaries potentially impacted by this defect:
-----------------------------------------------------
Stress Summary 1
Stress Summary 4
Also See:
Critical and High issues released in v.11.03.00
Known Issues in AutoPIPE (Enhancements, defects, etc..)