04. Results From Loads and Load Sets Not Answered By Piping Code Calculations

The following section will cover general questions about AutoPIPE's results based on Loads and Load Sets that are NOT answered by Piping Code calculations

  1. Question: noticed that results for all thermal analysis are the same, no mater what temperature setting is entered:


    Thermal expansion coefficient at ambient temperature is entered in the pipe properties screen or grid ONLY. Units for that coefficient "alpha" is 1.0E-6 in/in/degF or 1.0E-6mm/mm/degC

    The expansion rate for each operating case is entered on the Operating Pressure & Temperature data screen or Press/Temp/PipID tab of the input grid as shown below:

    The expansion rate is defined as:

            Expansion = MeanAlpha*DeltaT = MeanAlpha*(OperatingTemperature - AmbientTemperature)

    In this equation MeanAlpha is the average alpha between Ambient and Operating temperature

    The units for this is in/100ft or mm/m  (no temperature units since temperature is already multiplied).

    If you enter a standard material like CS or a SPEC material like A106-A on the pipe properties dialog, the expansion data will be filled up automatically based on temperature (note: check box in from of data is enabled, checked ON). Only when you enter NS (Non-Standard) as the material, expansion data will not be computed and needs to be manually entered (note: check box in front of data is disabled, checked OFF). AutoPIPE expansion data is based on code expansion data table (in/100 ft) and not on alpha table. The alpha table might give slightly different results.

    You can override calculated expansion and enter your own values if you wish by disabling (check OFF) the check box in front of the data, then enter your own value (note the value units when entering data).

    In addition, various material libraries are now provided with AutoPIPE where the material library can be edited and  compiled to add or modify expansion data.

    In this case above, the model had T2, T3, and T4 where the expansion values are all the same. Therefore the thermal displacement would be all the same regardless of temperature settings because Auto check box was found disabled (checked OFF). Solution, manually update the data with the correct values, OR enable (check ON) Auto box in front of the expansion values, OR change the pipe properties material to a listed values other than NS.

  2.  Question: AutoPIPE: different Results w/same input. 2 separate models with identical input or single model with identical loadcases / analysis sets In both cases the results are different

    TR Number:
    Product: AutoPIPE
    Area: General
    Problem ID#: 71085


    Check the model output reports to verify input is identical.

    Steps to repeat:
    Comparing 2 AutoPIPE models
    1. Start AutoPIPE with a valid license.

    2. Open model DAT

    3. Analyze the system, Analyze> Analyze all.

    4. After the analysis is completed, create a complete output report; Results> Output report> Check all sub reports ON.

    5. Perform steps 2-4 for both models.

    6. Use a program like "Beyond compare" or "Ultra Compare" to compare
    the files. This will quickly highlight and differences between the models.

    Note: take extra care to be sure that all Analysis summary settings are exactly the same (Tools> Model Option> General, Edit, Results, Burried Pipe Options, etc..). In addition for comparison purpose only, set Tools> Model Options> Results> Sustain Margin (Y/N/E) = N. This setting will affect the allowable calculation.

    7. Expect to find different time stamps and maybe some info that may be out of sync. However, everything else should be identical.

    8. Fix any differences between models until they are identical
    and then run an anlysis to compare results.

    9. If the models still produce different results, add both model DAT & supporting files to run the analysis in a ZIP file, and send to Tech support for review. Also, include the OUT files used to compare these models.

    AutoPIPE Model with similar analysis sets.

    1. Start AutoPIPE with a valid license.

    2. Open model DAT file

    3. Analyze the system, Analyze> Analyze all.

    4. After the analysis is completed, create a complete output report; Results> Output report> Check all sub reports ON.

    5. Open the model's input grid, select the Press/Temp/PipeID tab
    copy the entire grid to excell, Use Excell to compare each Temp/Press loadcase to confirm identical settings (could have different Press, Temp, Expansion, Hot Mod,Hot Allow, or Yield values).

    6. Review model listing to confirm no addtional Xtra Data is assigned to a loadcase (i.e. Force, distributed load, concentrated force, cut short, etc..)

    7. If the model still produce different results, create a service ticket using this information  and send for review.

  3.  Question: AutoPIPE: Diff GR load in analysis set

    Model has 2 different analysis sets, but the support loads dues to GR(1) and Gr(2) are different, why?

    TR Number: none
    Product: AutoPIPE
    Version: 09.04 and higher
    Area: General
    Problem ID#: 91549


    The different results from Gravity(1) load case in Analysis set 1 and Gravity(2) in analysis set 2 can be related to Pressure stiffness and Hot Modulus settings in the respective analysis set. Review both analysis sets to be sure same settings exist.

    Pressure Stiffening:
    Select the pressure stiffening case used for the analysis set. Pressure stiffening will change bend flexibility and stress intensification factors for all load cases in the analysis set including the gravity case.
    Hot Modulus:
    Select the hot modulus case used for the analysis set. The hot modulus will affect the element stiffness and calculated displacements and would apply to all load cases including the gravity case.


See Also

Bentley AutoPIPE