Yes, applied and max nozzle loads.Looking into possible design changes.Must Know max loads and allowable applied loads for nozzles, Basically, looking for easy way to calculate all possible design applications quickly.
1. You have piping loads already; or
2. You need to determine how much the nozzle can take.
If (1), arto has a real good reference and go that way.
If (2).....
The piping design engineer should tell you what they are applying.
You can back calculate a series of load combinations from Bednar. However, you will have at least a thrust and vertical shear and longitudinal moment at the shell and possibly a circumferential shear and moment. This all depends on the piping arrangement. Therefore, backsolving you have to assume a set of loads and determine if they are okay.
Then you have to tell the piping engineer you can't exceed these. This usually works out to be a sereis of iterations (changing repads, nozzle neck thickness, etc) as you both work to something you can live with.
If it is (2), you have to keep the piping engineer in the loop.
LC Peng has authored, co-authored and presented many technical papers on these subjects. Electronic versions of his most popular papers are available below.
Local Stresses in Vessels - Notes on the Application of WRC-107 and WRC-297
In contrast to traditional finite element modeling, where the analyst must build the model from scratch, FE/PIPE uses pre-fabricated templates for piping and vessel components. A library of component templates is available for Piping Intersections, Nozzles (in Flat Plates, Cones, Tanks, Heads, including Hillside Nozzles), Reinforcing Pads, Stanchions on bends, Piping Supports, Lugs, etc. The Shell String Modeler allows one to model connected Piping and Vessel segments. This includes mitered elbows, bends, reducing elbows, cylindrical and conical segments, annular plates, and spherical or elliptical heads. The latest version includes templates for a shell containing multiple nozzles, a pad reinforced fabricated cross, structural elements, and API storage tanks, nozzles and base settlement. The Plate Processor allows user defined plate attachments (lugs, saddles, shoes etc) for shell and nozzle elements. Large complex geometries may be built up by combining several smaller "child" models to a "parent" model. This is done by defining common nodes between models. The recent addition of 8-node Brick Templates allows one to perform thick wall (D/t < 10) analysis. 32-bit processing and graphics have speeded up the program by 2-3 times. There is also automated animation, Quick Calc feature for WRC107/297 and N318/392, a thermal profiler for unreinforced fabricated tees, and reinforcing pad options for hillside nozzles and bends with stanchions.
What are specific areas where a FEPipe calculation is needed? In summary, the following examples illustrate areas where FEPipe can significantly improve on existing more simplified design methods.
- Validation of pressure designs in large d/D intersections
- Allowable load determination on nozzles.
- Replacement Method for WRC 107 or WRC 297
- Cyclic applications (>5000 cycles)
- Large hillside or lateral nozzles.
- Nozzles subject to high temperatures and the potential for elastic follow-up. (>800 deg.F)
- Transverse or Axial loads on saddles.
- Bends with staunchions or structural weldments
- Transient Thermal (and thermal+pressure) loading conditions.
- Stiff systems interacting
- SIF's for non-code geometries, or for geometries outside of Code limits, and geometries not addressed by the code.
- Jacketed Piping systems
- Fixed tubesheet designs
- Collapse of thin walled piping geometries
- Stress distributions around multiple openings
FEPipe is a template driven finite element program designed exclusively for the piping and petrochemical markets. FEPipe handles saddles for axial or lateral loads, a result that Zick could never do, and find stresses in lugs and attachments in the automodeller. FE/Pipe will also produce allowable loads on nozzles which can then be handed to the piping engineer for evaluation. The new version FEPipe 4.100 does a spectacular job with multiple, close proximity nozzles in heads or cylinders using unstructured meshing.
It's known that B31 Appendix D is only justified for D/T<100. For thin walled pipe, FE/Pipe is the only tool available that will make a direct calculation of the sif and flexibility. FE/Pipe handles the thermal gradient requirements of 301.7.2, and the cyclic load requirements of 301.10. This is where the real failures occur and if the structure cycles then an accurate calculation of the loads and stresses is important. If your work involves API 579 the required membrane and bending stress determinations are found directly in FE/Pipe using Pl and Qb as described by Bergreen. You can even incorporate patches of localized corrosion/erosion and dents.
Hi lsthil
Thank you for the in put. I checked out fepipe and found it very good. My primary goal was to be able to calculate
nozzle loads min & max .Our customers were asking for it.
my company is checking fepipe out for possible usage. Thanks again!
CAESAR II user must have FE-PIPE/ALL Pro/Nozzle Pro. and BOS Fluids to do Piping Stress Anslysis API 579 LEVEL III requirement.
Pressure Vessel user must have FE-PIPE/ALL Pro/Nozzle Pro. and BOS Fluids to do PRESSURE VESSSEL DESSIGN ASME Requirement...and After THE NBIC/API 579 LEVEL III requirement.
Nozzle/Pro was designed specifically for the instances where excessive conservatism or dangerous designs might result from dated and often inadequate simplified techniques. Nozzle/Pro is "sharpening the pencil", and eliminating uncertainty in a calculation. If a WRC 107 method, for example, in cases where WRC 107 estimates a result within plus or minus 150%, Nozzle/Pro can and will produce a result within 15%, and will produce it much faster.
High resolution graphic plots allow the user to easily verify the data input. The user never sees node or element numbers, since these remain internal to the program. Data input is in the form of geometric details relevant to the section being modeled. Help screens are available to guide the user with data input entries. The finite element mesh is automatically generated with mesh concentration in areas of interest, like weld penetration lines. Input graphics may be displayed with hidden line removal, element shrinkage, and light shaded plots. Output is produced for deformation, code calculated stresses, code allowables, stress intensification factors and nozzle flexibility values. Deformations and stresses can be viewed on screen as multi-color shaded plots, which can be sent to high resolution laser printers or to color inkjet printers like the HP Paintjet XL300. Contoured stress plots and distorted shapes may be viewed with optional hidden line removal, and element separation. Graphic plots may be interactively viewed, with zoom, pan and rotation features allowing viewing at any angle and distance.
For piping stress analysis, ASME B31 expansion stress results are presented. However, since the piping code has several shortcomings and inaccuracies where intersections/nozzles are concerned, code interpretations are derived using input from the ASME Nuclear section III and section VIII division II (nuclear) ASME code cases, and on published fatigue and burst test studies. These relationships between code stresses and code allowables have been verified by comparison to actual failure data. The resultant code stress reports give the maximum code stress, its B31 allowable, and the corresponding ASME section III Class 1, and Section VIII, Div.2 allowables. Detailed stress reports are given for primary, secondary and peak stresses, and the allowed number of cycles for a given stress is also printed. Fatigue evaluation for vessels and nozzles is fully covered by FE/PIPE, using stored fatigue curves from Appendix I of ASME III and Appendix 5 of ASME VIII. Strain concentration factors are included where required. Load cases are automatically set up to satisfy code requirements, based on specified loading conditions. Occasional loads can be evaluated to primary collapse or fatigue criteria.
Stress Intensification factors and flexibilities (axial, in-plane, out-of-plane and torsional) are calculated from the finite element model, and may be applied to B31 analysis of an intersection (e.g. in CAESAR II). These SIF's are independent of the standard B31 SIF tables. FE/PIPE also produces an SIF report which provides comparison with B31.1,B31.3 and WRC 330 values, using the same geometry throughout. By using the SIF's and flexibilities generated by Nozzle/Pro, accuracy of "beam-type" pipe flexibility calculations can be greatly improved. An estimation of load reduction due to the use of the finite element calculated flexibilities, is also provided.
Stress calculation can be made in Nozzle/Pro according to WRC107 and WRC297, and a comparison made with the finite element calculated stresses. This allows the user to be able to see when WRC values are actually valid. This is useful since the WRC guidelines were originally based on a limited range of test data.
Other features of Nozzle/Pro include:
1) Stresses at intersections due to pressure/pressure thrust
2) Thermal Stress due to linear temperature gradients across the wall.
3) Intersection reinforcements models to conform to B31.1 Appendix D
NOZZLE PRO applies automated finite element techniques to analyze pressure vessel nozzles. Built-in intelligent meshing technology is used to evaluate the header/branch intersection and to automatically create a finite element model. Shell header types permitted are hemi, elliptical, conical dished and flat heads, and cylindrical shells. Nozzles may be straight, pad reinforced, or self reinforced. A materials database contains allowable stresses, expansion coefficients, yield stresses etc. Hillside nozzles are permitted, as are nozzles with tilted central axis.
Nozzle loads (forces and moments) are specified by the user, together with number of cycles for operation and occasional load definitions. The program calculates stresses in the header and branch, stress intensification factors (for use in pipe stress analysis programs like CAESAR II), and stiffness values for the intersection. Stress values are compared to values calculated according to ASME B31.1, B31.3, WRC330, ASME III, and ASME VIII Division 2. Nozzle Fatigue analysis is calculated in accordance with Div.2 rules. Tabular reports and stress contour graphics are generated in HTML format.
