Applies To Product(s): AutoPIPE, Version(s): 2004, XM, & V8i Environment: N/A Area: Subarea: Original Author: Bentley Technical Support Group Comments, Questions, and Answers about ASME B31.1 Piping Code Calculation Issues Item #1: After changing the piping code edition from 2010 to 2012, the results are different, why? Answer: 1. B31.1 2010 library has different modulus values as compared to B31.1 2012 library, for example compare the pipe material library data from both library files ( B311-10 & B311-12) for CS. This will account for some of the differences observed by the user. 2. Review the Temp / Press/ PipeID tab to be sure that the expansion and modulus values in the model are correct. 3. The ASME B31.1 -2012 code has different material values than listed in the 2010 edition. These changes would effect multiple pipe properties, ex. long, hoop and shear modulus, in the program. 4. In some rare cases (where no consistent steps have been documented in order to repeat), the model data was found to be different when compared to the program's library files. This would cause a significant change in the code compliance calculations. One way to be sure the model has the correct library values is to essentially reset the Library data by using the following procedure: Under Tool> model Options> General> change the ambient temp from the original setting to a different one, press OK button a few times, and then go back to the same location to change it back to the original value. This action will cause the program to reload all the material library data used in the model or refresh the data. Warning: after resetting the library data as described above be sure to validate the Tools> Model Options> Edit and Results settings are correct. Item #2: Which equation the program uses for thermal stress. There are two equations that address the thermal stress in the power piping code and the process piping code. Both equations are listed in ASME B31.1 Power piping code and B31.3. Process piping code. One is very conservative eq. 1A. The second eq. 1.B. Is much more liberal. The reason i am asking this question is that if your system fails eq. 1A does not mean that the system actually fails until it fails eq 1b. Answer: To the CAE development team, ASME Eq 1b is know as Sustain Load Margin. AutoPIPE has a feature under Tools> Model Options> Results> Sustain Margin that always includes, only includes when needed, or to never be considered in a model analysis. See online help for more details on this feature. If you do not know about these settings, suggest that you take some time and review each one as they are very important to your analysis results. Item #3: Logged: November 2014, AutoPIPE V8i 09.06.01.10. In ASME B31.1 1986, Section 104.8.2 Stress due to Occasional Load, and Section 104.8.3 Thermal Stress Range. has an options to take credit for SAM load case(s) moments in equation 12 or equation 13 (see definitions for Mb and Mc. What is the correct method to apply the option of analyzing SAM load case moments in Eq 13 instead of Eq. 12 in the code using AutoPIPE. Answer: At this time AutoPIPE does not have an automatic option to switch SAM load case from Code equation 12 to 13. This has to be performed manually with the following Steps. Step 1 - Create a model with Piping code = ASME B31.1 1986, SAM load case(s), and Analyze the model. Step 2 - Select Tools> Combinations> Code Comb tab and delete all default combinations = (SUS)+S1 to (SUS)+S10. Step 3 - Create new user code combination(s), as SAM is unsigned and thermal moments are signed, ABS SUM may be selected as the combination method. Create additional combinations similar to above as needed. Step 4 - Review Results. Conclusion: By deleting the combinations (SUS)+S1..S10, the SAM load case were removed from Eq 12 and was added to Eq 13 with the new User combinations created in Step 3 above. In addition, this version of the program shows Ma as a term in the online help code equation section for " Stress Due to Occasional loads ", this is a typo and should be replaced in future versions with correct term Mb . See Also Bentley AutoPIPE External Links Bentley Technical Support KnowledgeBase Bentley LEARN Server Comments or Corrections? Bentley's Technical Support Group requests that you please submit any comments you have on this Wiki article to the "Comments" area below. THANK YOU!
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