What Is “More Applicable Data?” - Xsystem Ltda “More Applicable Data” The revised (ASME 07-...
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© Intergraph 2014 What Is “More Applicable Data?” Taking Advantage of FEATools
Transcript of What Is “More Applicable Data?” - Xsystem Ltda “More Applicable Data” The revised (ASME 07-...
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What Is “More Applicable Data?”
Taking Advantage of FEATools
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Why “More Applicable Data”?
Tee flexibility is set to 1.0 – no flexibility!
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Why “More Applicable Data”?
This note (below) from B31.3 Appendix D alerts the user to possible non-conservative results when using Code rules!
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Why “More Applicable Data”?
The Codes permit “more applicable data” to be used so that Engineers can address:
Inaccuracies in the Codes and Standards
Assumptions made by the Codes and Standards
More recent works and studies
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A Brief History of SIFs and “k” Factors
Late 40’s: A.R.C. Markl of Tube Turns leads the effort to develop geometry-based multipliers for component flexibility and stress.
1981: R.W. Schneider (formerly of Bonney Forge) notifies ASME of the un-conservative SIF for reduced outlet tees.
1987: In response to Schneider’s conclusions, E.C. Rodabaugh authors WRC Bulletin 329 (Dec. 1987) – “Accuracy of Stress Intensification Factors for Branch Connections”. (Rodabaugh worked with Markl on the original tests in the late 1940’s.)
2007: A.W. Paulin starts an ASME project to realign stress intensification factors between the Code Books (ASME ST-LLC 07-02).
60 Years
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ASME 07-02 Project Conclusions
Flexibilities for header and branch are necessary:(current Piping Codes assume rigid branch connections).
Separate SIFs are provided for header and branch:(current Piping Codes use the same SIF for both header & branch).
SIFs are given for in-plane, out-plane and torsion:(Power Codes don’t differentiate between in-plane and out-plane, and Process Codes don’t intensify torsion).
The revised SIF & “k-factor” equations include the branch diameter and thickness, as well as the pad thickness (if specified). So the ratio of branch size to header size is accounted for.
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Why Use “More Applicable Data”?
The “Primary Goal” is:
… more accurate results!
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Sample 07-02 Equations: Welding Tee
Term EquationRun In-plane Flexibility Factor, kir 0.18 (R/T)0.91 (d/D)5
Run Out-of-plane Flexibility Factor, kor 1
Run Torsional Flexibility Factor, ktr 0.08 (R/T)0.91 (d/D)5.7
Branch In-plane Flexibility Factor, kib (1.91(d/D) – 4.32(d/D)2 + 2.7(d/D)3) (R/T)0.77 (d/D)0.47(t/T)
Branch Out-of-plane Flexibility Factor, kob (0.34(d/D) – 0.49(d/D)2 + 0.18(d/D)3) (R/T)1.46(t/T)
Branch Torsional Flexibility Factor, ktb (1.08(d/D) – 2.44(d/D)2 + 1.52(d/D)3) (R/T)0.77 (d/D)1.61(t/T)
Run SIF In-plane, iir 0.98 (R/T)0.35 (d/D)0.72(t/T)-0.52
Run SIF Out-of-plane, ior 0.61 (R/T)0.29 (d/D)1.95(t/T)-0.53
Run SIF Torsional, itr 0.34 (R/T)2/3 (d/D)(t/T)-0.5
Branch SIF In-plane, iib 0.33 (R/T)2/3 (d/D)0.18(t/T)-0.7
Branch SIF Out-of-plane, iob 0.42 (R/T)2/3 (d/D)0.37(t/T)0.37
Branch SIF Torsional, itb 0.42 (R/T)2/3 (d/D)1.1(t/T)1.1
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Modeling Tees per ASME 07-02
The current modeling technique:
10
40
20
30
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Modeling Tees per ASME 07-02
The new suggested modeling technique:
10
41
20
31
23
24
22
21*
**
*
*
SIFs & k-factors Provided
Node/CNodepair
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Implementing “More Applicable Data”
The revised (ASME 07-02) model an be automatically setup in CAESAR II, based on: An initial CAESAR II model, built normally. A model transformation, performed by FEATools, yielding a more
refined CAESAR II model.
The revised (transformed) model can be analyzed normally. This revised model has more applicable k-factors. This revised model has more applicable SIFs. This revised model yields more accurate displacements, forces, and
stresses than the analysis of the original model.
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Why Has Design per the Current Codes Worked?
The Codes are a “minimum” set of requirements
The Codes have safety factors.
Many systems don’t cycle, or have low cycle requirements.
Many systems are not highly loaded.
This doesn’t mean you won’t have a problem tomorrow.
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Why Has Design per the Current Codes Worked?
This Code (B31.3) is not intended to apply to the operation, examination, inspection, testing, maintenance, or repair of piping that has been placed in service. The provisions of this Code may optionally be applied for those purposes, although other considerations may also be necessary.
The Codes may produce safe systems, but not necessarily economic or highly reliable systems.
The “sharper pencil” of FEATools will improve the model, allowing more accurate predictions of strain and load distribution.
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When Should FEATools Translation be Considered?
The system includes rotating equipment
When D/t > 100
When Operating Cycles > 5000
When there are pressure cycles
When 0.5 < d/D < 1.0 (per B31.3 Appendix D Note 11)
When thin walled welding tees are utilized
When the system stresses are high compared to the corresponding allowable stresses
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When Should FEATools Translation be Considered?
Determine the “Criticality Index”: Available in FEATools Available as an iPad/Mobile application
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When Should FEATools Translation be Considered?
For the (B31.3) S303 example, the Criticality Index is reported as 31.5.
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When Should FEATools Translation be Considered?
Additional information and justification is provided by this tool.
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What is the anticipated outcome?
More accurate results: True flexibilities Accurate displacements Proper load distribution to nozzles Correct Code Stresses
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Anticipated Work-Flow
1. Build the CAESAR II model as usual
2. Analyze the basic CAESAR II model
3. Determine the “criticality index”
4. Translate the CAESAR II model according to ASME 0702 or FEA
5. Analyze the refined (translated) model
6. Compare the results, use Engineering judgment for further actions
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Anticipated Work-Flow
1. Build the CAESAR II model as usual.
2. Analyze the basic CAESAR II model.
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Anticipated Work-Flow
3. Determine the “Criticality Index”:
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Anticipated Work-Flow
4. Translate the basic CAESAR II model:
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Anticipated Work-Flow
5. Analyze the refined CAESAR II model:
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Anticipated Work-Flow
6. Compare the Results of the Basic and Refined Models:
Here the 07-02 refinement dropped the Code Stress from 124% to 52%.
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Anticipated Work-Flow
6. Alternatively refine the Basic CAESAR II model with FEA instead of 07-02. The Code Stress ratio drops further to 48%.
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Comparing the Results
Manually compare important values between the Basic and Refined models.
Alternatively, use the new Comparison Tool built into FEATools:
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Comparing the Results
Compare Displacement Changes:
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Comparing the Results
Compare Restraint Load (Nozzle Load) Changes:
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Comparing the Results
Compare Restraint Moment (Nozzle Moment) Changes:
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Comparing the Results
Compare Code Stress Changes:
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More Comparisons
The Basic CAESAR II model analysis reveals overstresses in several Expansion cases.
4 load cases are over-stressed, with a maximumcode stress ratio of 166%.
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More Comparisons
One solution is to add expansion loops in the horizontal “z” runs.
All load cases meet theirrespective allowable limits.
For the previously overstressed4 load cases, the maximumcode stress ratio drops to 84%.
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More Comparisons
An alternate solution is translate the model using the 07-02 methodology.
If “tee flexibility” can lower the Code Stresses to acceptable limits:1. The piping system avoids 3 loops (4 bends, 24 ft of pipe – each).2. The system saves the cost of the foundations to support the expansion
loops ($50,000).
Remember, the purpose of model refinement is to obtain more accurate results.
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More Comparisons
The Basic CAESAR II analysis shows 4 overstressed Expansion Cases. The Refined 07-02 CAESAR II analysis drops the maximum Code Stress from 166% to 15%.
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More Comparisons
The Basic CAESAR II analysis shows 4 overstressed Expansion Cases. The Refined FEA CAESAR II analysis drops the maximum Code Stress from 166% to 23%.
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More Comparisons
The FEATools Comparison Utility can compare all three variations of this model. The screen below shows the “correlated” Code Stresses. Note the 07-02 and FEA results align fairly close.
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More Comparisons
The FEATools Comparison Utility can compare all three variations of this model. The screen below shows the “un-correlated” Code Stresses. Note the 07-02 and FEA results align fairly close.
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More Comparisons
The FEATools Comparison Utility can be used to compare displacements, restraint loads, element forces, and Code Stresses. This enables a quick overview of the effects of the refined analysis.
DisplacementsElement Loads
Restraint Loads
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Comparisons can Reveal Potential Problems
This system requires Variable Spring design at 3 locations.
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Comparisons can Reveal Potential Problems
The Hanger Report for the Basic CAESAR II model indicates the following springs, loads, and travels.
The “travel values” are of particular importance here.
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Comparisons can Reveal Potential Problems
Consider the first hanger, Fig 82, Size 18, Hot Load = 11325 lb, Travel = 0.345 in, Cold Load = 13161 lb.
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Comparisons can Reveal Potential Problems
Is this the true behavior of the system?
Translate the model using both the 07-02 and FEA methods.
Analyze each system and compare the Spring Hanger design results.
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Comparisons can Reveal Potential Problems
Hanger Design Results from the 3 runs:
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Comparisons can Reveal Potential Problems
What happens if this (first, original) hanger is installed, but the actual travel is 0.943 in?
The hanger is now outside the recommended working range. Perhaps bottoming out !
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Comparisons can Reveal Potential Problems
Why could the CAESAR II designed spring(s) bottom-out?
1. The Basic CAESAR II model does not consider “tee flexibility”.
2. The original hanger design is correct, based on defined system parameters.
3. If these original hangers are installed, the true system behavior is as determined using 07-02 or FEA refinements.
4. The true system behavior has tee flexibility, and therefore experiences more deflection than the Basic CAESAR II model considers.
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Revisiting – “When is a Refined Analysis Required?”
What is the “criticality index” for the last two models?
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Revisiting – “When is a Refined Analysis Required?”
What is the “criticality index” for the last two models?
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Other tools to Determine When “Refinement” may be Necessary…
Use the FEATools “i/K” Calculator.
This tool determines the SIFs and Flexibilities based on various references.
Areas in “red” indicate the geometry is “outside” the scope of the reference: here D/t = 128.
This indicates refinement via FEA is preferred.
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Other tools to Determine When “Refinement” may be Necessary…
These results are for the “spring design job”.
Most results are within the scope of the references.
Notice the magnitudes of the flexibilities from 07-02: Kob = 31 Kib = 14 Ktr = 16
14 to 31 extra diameters of pipe length may affect the system flexibility ???
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Conclusions
1. Piping System evaluation is more than insuring system stresses are below allowable values.
2. Many (historical) assumptions and approximations are in play.
3. Many systems appear to have adequate performance because they are not significantly loaded.
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Conclusions
4. All Piping Codes permit a more refined analysis and more applicable data.
5. FEATools & CAESAR II provide more applicable data and a methodology to perform a more refined analysis.
6. The more refined analysis will avoid problems and save money.
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Thank You
Questions?
Acknowledgement:ICAS would like to thank Paulin Research Group for their help and assistance in the development of FEATools and their guidance with this presentation.
