Behavior

Problem Description

When evaluating ASME NB equation 11 for tee points, AutoPIPE calculates both the linear temperature distribution and
non-linear temperature distribution terms using Modulus of Elasticity, Thermal Expansion, and Poisson’s ratio from the
second header leg always. These terms are calculated in AutoPIPE under the assumption that the material properties for all
tee legs are the same. However, AutoPIPE is also capable of supporting different materials for each tee leg, independent of
the other tee legs. Using the pipe material properties from the second header leg only when determining wall gradient
stresses can result in a lower stress value, which can lead to unconservative results.

Steps to Repeat

To illustrate this defect, the following scenario can be considered:

Step 1: Create a new ASME NB Nuclear 2017 model with default units and libraries

Step 2: Insert a new segment “A” with a new pipe ID named “HEADER1”. Set the Nominal Diameter to 10”, the pipe material
to NS and set the Long. Modulus to 29.0. Accept the default of the Operating Pressure & Temperature dialog. Set the Design
Sm and Design Sy to 30000psi, with Design Pressure & Temperature set to default

Step 3: Insert an anchor at A00 and a welding tee 5’ in the DX direction. Uncheck “Use same segment name along header”

Step 4: Insert a run 5’ in the DX direction from the tee point and create a new pipe ID “HEADER2”. Set the Long. Modulus of
HEADER2 to 28.0 and leave the rest to default on both pipe properties and Operating Pressure & Temperature dialogs

Step 5: Insert a branch run 5’ in the DZ direction from the tee point and create a new pipe ID “BRANCH”. Set the Long.
Modulus of “BRANCH” to 30.0 and leave the rest to default on both pipe properties and Operating Pressure & Temperature
dialogs

Step 6: For all points, set the Delta T1 value to 100F. Run the static analysis for the model.

Step 7: Open the Stress Summary dialog and create a new stress summary. Set equation 10 transient to ‘Zero Moment’ and
‘Thermal 1’, leaving the rest of the fields at their defaults. Press Ok to save settings and close the stress summary dialog

Step 8: Generate the Stress Summary report

The stress value reported at the tee point will only be for the linear temperature distribution term. The Stress Summary
equation 11 stress results are reported as 13000 psi for A01, which is obtained by using v = 0.30, K3 = 1.0, E = 28.0 (HEADER2),
Alpha = 6.5E-06, and Delta T1 = 100. The reported stress value is using the material properties from HEADER2; however, a
higher stress value of 13929 psi is possible using BRANCH material properties. Similar effects can be seen by modifying the
cold thermal expansion and Poisson’s ratio.

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 in program version 9.1.0 or later?

2. Is the model using ASME NB editions 1972 + 1972 W Addenda or later?

3. Does the model contain at least one tee point?

4. Does any tee point contain different pipe identifiers that could result in varying material properties across the tee
legs?

A 'No' to one or more of the above criteria means that this defect does not affect the model’s results. No further
consideration is necessary.

Otherwise evaluate following mitigating conditions on the impact of this defect

1. The material used on tees is typically the same across all three legs

Workaround

There is no known workaround.

Solution

AutoPIPE shall calculate the linear and non-linear temperature distribution terms for all three legs of a tee and use the
maximum 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 + “_D1035676.TXT”), listing the tees with varying material properties across the legs of a tee.

The contents of the critical error report shall be like the following sample critical error report:

The program shall display the following confirmation message:

“ASME NB Equation 11 temperature distribution terms may not always
report maximum stress for tee points due to previous program defect
#1035676. Would you like to review evaluation report?”

The contents of the critical error report shall be like the following sample critical error report:

Defect #1035676 Evaluation Report
---------------------------------

Model Name: TEST1
Model Version: 12.01.00.10
Program Version: 12.02.00.04
Report Filename: TEST_1035676.TXT

---------------------------------

ASME NB Equation 11 linear and non-linear temperature distribution
stress terms always use material properties of the second header leg
of tees due to a previous program defect #1035676. 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 the following tee stresses may be using
non-conservative pipe material properties 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.
Tee point(s) potentially impacted by this defect:

-------------------------------------------------

A01

Also See:

Critical and High issues released in v.12.02.00

Known Issues in AutoPIPE (Enhancements, defects, etc..)

Bentley AutoPIPE