What are some typical modeling approaches for different types of piping?
#1: Coated / Fin PIPE (ex. concrete encased steel pipe): click here
Similar approach may be used here to come up with an equivalent modulus for the modeling pipe with Fins:
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#2. Corroded PIpe or Spot corrosion: click here
Question: Does AutoPIPE offer a function or upgrade that will analyze corroded pipe with the following user information:
a. Corrosion network sizes
b. Longitudinal and rotational positions
c. Minimum wall thickness at pit depths
#3. Corrugated Straight pipe: click here
#4 Jacketed Piping: click here
#5 Large Bore Piping:
Question: Are there any problems analyzing big diameter pipe systems? It was indicated that some issues with regards to Caesar's analysis of big diameter pipe analysis?
Answer:
This is a long standing issue with the Piping codes and this question comes up often.Yes, AutoPIPE can be trusted to model large diameter piping systems as long as it does not exceed the code requirements (typically D/t <= 100), hence large diameter pipes fall outside this limit. AutoPIPE calculates the Stress Intensity Factors (SIF) based on the code equations. Therefore, if you exceed the code equations, AutoPIPE cannot correctly calculate the true stresses in the pipe (i.e. local buckling, stressed weld points…). Care should be taken with such systems as they are susceptible to ovaling and denting and that should be considered while lifting or supporting the pipes. Some codes have rules related to ovaling and denting.
Both AutoPIPE and caesar prints a warning when D/t ration exceeds 100. We recommend for users to perform a local stress analysis (i.e. FEA) at these connections to determine a more accurate SIF and flexibility factors to enter back into the Pipestress model.
Note: Some WRC standards are also available to calculate SIF's for joints not covered in ASME codes, e.g. Trunnion elbows
#6. Can AutoPIPE handle 12 to 30 foot diameter welded steel pipes with internal veins? Mostly for steam flow…
Yes, AutoPIPE can be trusted to model large diameter piping systems as long as it does not exceed the code requirements. However, when D/T > 100, AutoPIPE can be used to provide the correct forces, moments, and displacements in the piping system by applying these user-defined SIF and flexibility factors. Care should be taken with such systems as they are susceptible to ovaling and denting and that should be considered while lifting or supporting the pipes.
Modeling, an equivalent pipe section with same section modulus for this large pipe with stiffeners could be calculated. Then adjust the density of pipe to get the equivalent weight of stiffened pipe when selecting a non-standard material (NS)
#7. Rigid Pipe Element with "ZERO" Mass (Pipe & Water S.G.=0)
Select a range of pipe, press Insert> Rigid options over Range> uncheck "Include Weight" and user choice to consider "Include Thermal Expansion".
#8. Pipe Lining:
The cladding mentioned in the pipe properties grid is referring to application on the outer most diameter of insulation.
On the pipe properties dialog, enter as lining thickness. Please note that lining is an added weight only and would not contribute the pipe stiffness. If this lining increases the stiffness, then a modified pipe modulus may be entered by computing an equivalent modulus that would give that same EI
Ee*Is=Es*Is+Ec*Ic
This will give correct bending stiffness by using Ee instead of Es in AutoPIPE. Axial stiffness will be approximate. s=steel, c=CRA. Is=steel moment of inertia.
#9. NFPA pipe, any Fire Protection Requirement capabilities?
NFPA (National Fire Protection Association) codes provide specific details about design, construction, operation, and maintenance of piping systems for fire protection.
To answer these questions, at this point AutoPIPE does not have a specific NFPA piping code. However, NFPA codes typically refers to the appropriate ASME design code which AutoPIPE may already have. Please review your NFPA code for stress analysis requirements. If AutoPIPE was found to contain the correct Piping Code specified by NFPA, then model the piping system in AutoPIPE as required.
#10. Tubing, i.e. small dia [ex. 1/2" (13mm)]
Yes, AutoPIPE has been used in development of tubing systems by our many users.
From the AutoPIPE online help:
Standard Pipe Cross Sections - ANSI/ASME Library. This library of pipe cross sections pertains to the ANSI/ASME codes B36.10M and B36.19M (1985). They are contained in the file AUTOPIPE.LIB. Pipe sizes from 1/8 (.405") OD with 0.049" wall thk, up to 36" sch 40 wall thk.
Copper Tubing Type L (ASTM B88 Refrigeration piping), pipe sizes from 1/4 (.375") OD with 0.030" wall thk up to 3" (3.125") OD with 0.090" wall thk
If a specific Tubbing is not available, while inserting a new Pipe Property, specify the various tubing dimensions as NS (non standard) and manually enter the correct size.
#11. Material was not available in libraries. what options are there?
A. Pipe size options:
AutoPIPE can model almost any size pipe used in most typical piping system built today. for a complete list of pipe sizes available in AutoPIPE, please see the following AutoPIPE help section:
Help > Contents> Contents Tab> Reference Information> Libraries> Standard Pipe Cross Sections
1. If you need to specify a pipe that is not currently in the library, perform the following: open the pipe properties dialog screen in a model, place cursor in the "Nominal Diameter" field and press F1 keyboard key. This will display the help for this field, there are instructions on how to enter in your Non-Standard (NS) pipe size.
2. If you like the pipe size added to a customize library file, please log a service ticket requesting information about creating a Component Library file.
B. Pipe Material options:
Select this link for options to add a new material into a Library file
Notes:
a. For casting materials, as mentioned in AutoPIPE help: "AutoPIPE does not provide any field for entering Basic Casting Quality Factor (Ec) provided in ASME B31.12 Table IX-2."
Please see the following AutoPIPE help section:
Help > Contents> Search Tab> enter "For casting materials" (include the quotes), press List Topics button, double click on the selected "Weld Factors" topic from the list provided to see more information on how to apply this factor in the program.
#12. Continuously supported over all its length atop the ground, along a steel beam, in an open trench or gutter
#13: Multiple pipe connections to a single header: click here
#14: Insulated piping: click here
#15: Square Duct piping
Rectangular duct work does not have the same moment of inertia in every direction (non-axisymmetric). Since most industrial piping is round, AutoPIPE's analysis takes advantage of this homogeneous (axisymmetric) shape and properties
Another words, the stiffness of a duct cannot be accurately represented as a pipe and the analysis codes currently available in AutoPIPE does not address rectangles shapes..
Suggested modeling approach; model the square duct as a AutoPIPE Beam with the correct properties, analyze the model, generate an Beam output sub report, transfer beam forces and moments results to another application for stress analysis.
Bentley recently acquired an application called ADINA, this application may be able to perform a stress analysis using the forces and moment results generated from AutoPIPE. There will be an model export option from AutoPIPE to ADINA in the future. Please file a service ticket referencing this WIKI page and inquire about the status of this new feature: ADINA integration (915864).
#16: Longitudinal welded steel pipe
On the Pipe properties dialog, to model a ERW or Weld pipe based on a seamless Pipe Material selection, set "Long weld E fact" < 1 and factor the Sc & Sh as needed per code requirements
Note:
1. The longitudinal weld E factor should be less than 1.0 for Long Weld WL fac field to be enabled. Also, the Longitudinal Weld E factor would be applied to Hoop allowable in addition to Longitudinal Weld WL factor (see AutoPIPE help for details on this dialog).
2. This factor E is accounted in allowable stress values given in material library. This factor E in Table A-1 and Table A-2 are applicable to both straight seam and spiral seam welded pipe.
3. ASME B31.1 2020, Modeling longitudinal welded pipe only affects hoop allowable and no other allowable, why?
i. The code does not mandate inclusion or exclusion of Joint Efficiency Factor for Sc and Sh. It uses the word may, so either way should be correct. However, if the user wants to have a more liberal expansion allowable, user may divide the Allowable Stresses from Mandatory Appendix A by the Joint Efficiency Factor to get higher Sc and Sh values.
ii. The values provided in AutoPIPE's Library are for Seamless Pipes. The user may define their own materials in a library for welded type pipes with the correct allowables for welded pipe.
#17: Clay Pipe
:
Most clay piping is used for carrying water / sewage underground. AutoPIPE does not have clay piping material in any of its libraries. Use one of the options here to add a non standard material for use in AutoPIPE. Example, on the pipe properties dialog, set Materiel = NS (Non Standard) and manually input the pipe properties of the clay pipe. The user than must decide what piping code to analyze the model (as a suggestion: General Stress, ASME B31.1, etc..) or contact a reputable source like the Local DOT Standard (example DOT New Hampshire Standards and Specifications, section 603) or American Concrete Pipe Association for assistance.. Just be sure to understand the code an non-code calculations that are to be applied in the model when using AutoPIPE. One may also need to manually assign user-defined allowables for code combinations on the Combinations dialog.
#18: Pipe with 12% mill tolerance
On the Pipe properties dialog, to model a pipe with 12% mill tolerance perform the following Steps (assuming a new pipe ID)
Step #1. Open Pipe Properties Dialog or Model Input Grids
Step #2: Enter a Nominal Dia (ex. 10.00 inches), press Tab key
Step #3: Enter a Schedule or select NS (ex. STD), press Tab key
Step #4: enter a Corrosion Allow (ex. 0.125 inch), press Tab key
Step #5: Notice Mill tolerance has an automatic default value after entering the schedule in Step #3 above (see help to understand this default value). Update as needed, , press Tab key
Step #6: Finish filling in the rest of the dialog as needed and press OK button
#19: Model Non-metallic Plastic Piping (i.e. Plastic, PVC, PP, PPR, HDPE, PE, FRP, GRP, etc.)
See Also