Nozzle Pro

Paulin Research Group

NozzlePRO Program Manual

Paulin Research Group 11211 Richmond Avenue, Suite 109 Houston, Texas 77082

Tel: 281-920-9775 Fax: 281-920-9375 Email:

[email protected] [email protected]

Table of Contents Chapter 1 – About Nozzle Pro Section 1 – Version Features Section 2 – When to use NozzlePRO Section 3 – Sample Problems Section 4 – Sample Problem Details Section 5 – How to Get Help Chapter 2 – Using NozzlePRO Section 1 – Getting Started Section 2 – Stress Types Section 3 – Options Data Form Section 4 – Using the 3D Viewer Section 5 – How NozzlePRO Starts the DirectX Viewer Section 6 - Errors – Aborted Runs – and DirectX Troubleshooting Section 7 – FE/PIPE, NozzlePRO, PVElite, and CodeCalc Chapter 3 – Interpreting and Using the Results Section 1 – Output Review for 3D Shell Models Section 2 – Stresses and Allowables Section 3 – Pressure Design Using 3D Shell Elements Section 4 – Stress Intensification Factors and Flexibilities Section 5 – Allowable Loads Section 6 – Discussion of Results (Recommended Ways to Use the Output) Chapter 4 – Saddle Supports and Pipe Shoes Section 1 – When to Use NozzlePRO Saddle / Pipe Shoes Section 2 – Saddle and Pipe Shoe Input Screens and Saddle Wizard Section 3 – Applications of the Saddle / Shoe Modeler Section 4 – Interpreting the Results Section 5 – Integral vs. Non-Integral Wear Plates Section 6 – Other Topics Chapter 5 – Advanced Models Section 1 – Nozzle\PRO FFS Section 2 – Piping Input Screens Section 3 – Axisymmetric 2D and Brick Models Section 4 – Skewed Structural Supports in NozzlePRO Chapter 6 – Special Topics Section 1 – WRC Comparisons Section 2 – Engineering Considerations Section 3 – Finite Element Philosophies, Element Types, Etc.

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Axisymmetric Horizontal Vessel Modeling with Saddles Axial Load Evaluation for Horizontal Vessels Gravity Multipliers for X, Y, & Z Directions for Modeling Vessel Loads Solution Data Report a. Stiffness matrix information including maximum row size, largest stiffness coefficients, and stiffness coefficient distribution. b. Total number of nodes, elements, and solution cases c. Summation of loads at boundary conditions for each load case. Allows for verification of weight and loads applied to model and helps check for unbalanced loads. Pipe Shoe Modeler Integral & Non-Integral Wear Plates for Saddles and Pipe Shoes Tapered Saddles and Pipe Shoes SYMFIX Boundary Conditions for Midspan Ovalizing in Horizontal Vessels Upgraded DirectX 3D Dynamic Displacement and Static Model Viewer Nozzles through Blind Flanges in Axisymmetric and Brick Models Double Bed Support Axisymmetric and Brick Models Axisymetric 2d and Brick Axisymetric Models Steady State and Transient Heat Transfer for Axisymetric 2d Elements Blind or Matching Flange End Conditions for Axisymetric 2d or Brick Models Radius’d Welds in Axisymetric 2d and Brick Models Overturning Moments on Skirts (Brick Models) DirectX 3d Dynamic Displacements Internal Ring Loads in Axisymetric 2d or Brick Models

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Help Buttons Throughout Discontinuity Stress Reporting Integral and non-Integral Repads for Axisymetric 2d or Brick Models Head Thickness Contours for Bricks and Axisymetric 2d models Support for DirectX 3d Rendering Updates a. Three-Dimensional views of the geometry, stress or displacement state can be rotated, panned, zoomed or clipped in real time and sent to clients for viewing on their own computer. (See Files discussion below.) b. Translucent or hidden-line wireframe views may be manipulated. c. An interactive thermometer may be used to view the exact stress at any point in the model. d. Rubber-band, Viewport, or polyline clipping. e. Cut to Clipboard f. High Stress Call Outs g. Model Cutaway by Value or By Percentage 24- Structural Attachments a. Ten different structural attachment cross sections can be loaded on head, cone or cylindrical geometries. b. Attachments may be with or without a pad. c. Moment loads are applied automatically over the structural end section. 25- Unstructured Meshing Options for Heads & Structural Attachments a. Difficult-to-mesh structured geometries are often easily meshed using unstructured methods. Unstructured meshing is available for head or structural attachment models.

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26- Elemental Smoothing a. Elemental smoothing produces more uniform element grids and perfect geometric shapes not dependant on cubic approximations. 27- Cylinder Boundary Condition Control a. Users may free either the top or bottom of the cylinder and observe the effect on the stress distribution in the geometry. 28- Added Control of Weld Sizes a. The user may specify the weld length along either the branch or header (parent) and may also specify the weld size at the edge of any reinforcing pad. 29- Access to FE/Pipe Input Data Screens a. The user may access the FE/Pipe input data screens to provide any additional model, mesh or loading control that is needed. 30- Control of Element Stress Averaging a. The user may deactivate stress averaging if desired. 31- Saddle Wizard a. A step-by-step interactive modeler that allows the user to easily design horizontal vessel for any loading conditions. The Saddle Wizard now allows for full horizontal vessel models with one saddle fixed and the other saddle sliding. Earthquake or ship motion acceleration loads, pressure, temperature, and more can be applied to the model. 32- New File Handling

33- Dynamic Units Switching a. When switching between English and SI units, the input values are now converted from one system to the next units system. 34- Load Translation Calculator a. Nozzle/PRO users no longer need to have their loads given at the end of the nozzle. Loads can now be specified at the centerline of the header, header/branch intersection, or the end of the branch. 35- Pull Down Menus and User Navigation 36- Improved Brick Meshes of Nozzles in Heads 37- Example Models Using NozzlePRO

3d Viewer Screen

Structural Attachment Options Unstructured Mesh

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Top Head Blind & Pad

Pipe Shoe

Size-on-Size Pad

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Bottom Head Skirt

Brick Flanges & Skirt

Triple-Plate Support

Hillside Nozzle Pad Reinforced Nozzle

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Top Head Load Flanges

Head Structural Support

Reinforced Lateral in Cone

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Saddle Options

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Pipe Shoe Options

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Horizontal Vessel with Saddle Support

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Chapter 1 – Section 2 When to Use NozzlePRO Typical occasions when a finite element analysis of a NozzlePRO geometry is beneficial are listed below: 1) When the d/D ratio for a loaded nozzle is greater than 0.5 and WRC 107/297 is considered for use. 2) When the t/T ratio for a loaded nozzle is less than 1.0 and WRC 107/297 is considered for use. 3) When the nozzle is pad reinforced and WRC 107/297 is considered for use. 4) When the number of full range pressure cycles is greater than 7000 cycles and the nozzle is subject to external loads. 5) When the D/T ratio is greater than 100 and SIFs or flexibilities are needed for a pipe stress program. 6) When the D/T ratio is greater than 100 and a dynamic analysis including the nozzle is to be performed using a piping program. 7) When a large lug is used in a heavily cyclic service. 8) When pad-reinforced lugs, clips, or other supports are placed on the knuckle radius of a dished head. WRC 107 simplifications for pad reinforced rectangular lug attachments are fraught with potentially gross errors. 9) When seismic horizontal loads on vessel clips or box supports are to be evaluated. 10) Pad reinforced hillside nozzles subject to pressure and external loads. 11) Large run moments, but small branch moments in a piping system. 12) Overturning Moments on Skirts 13) Effect of Integral vs. Non-Integral Pad on Nozzle in Head Should be Studied 14) Different thermal expansion coefficients or temperatures between the header and branch. 15) Where loads on nozzles are high because of the assumption that the nozzle connection at the vessel is a rigid anchor. Few connections at vessels are “rigid.” Often only small rotations can significantly reduce the calculated moment and stress. Accurate flexibilities permit the actual moment on the vessel nozzle to be calculated and designed for. 16) Heat Transfer in An Axisymetric Model Geometry 17) When the effect of adding a radius to weld geometries on nozzles in heads should be investigated. 18) To verify FEA calculations. NozzlePRO4 allows nozzles in heads to be analyzed with shell, axisymetric, or brick finite elements. The analyst can run each model type and compare results to determine the stability and accuracy of the solution. 19) For saddle supported horizontal vessels with or without wear plates including tapered saddles with many design options. 20) To evaluate effects of axial or transverse loads due to internal sloshing, wind loads, seismic loads, or general external loads. Zick’s methods do not consider axial or transverse loads. 21) Design of Pipe Shoes for self-weight, liquid weight, and external loads. Criticality of the application is a major consideration when deciding whether or not to run a finite element calculation. Hot hydrocarbon products are clearly more dangerous than ambient temperature water processes and should be approached with increased caution. Systems that do not cycle are less prone to failure than systems that cycle daily. Extreme design conditions can also make using less conservative, more accurate approaches practical. Large d/D, D/T intersections are difficult to analyze properly for a combination of pressure and external loads, and FEA results tend to give more consistent results over a broader range of problem parameters. Allowable loads on vessel nozzles give the piping engineer guidance when evaluating thermal loads on anchors. Higher earthquake load requirements can make conservative design assumptions costly. Caution should be excercised when low pressure-high temperature systems are evaluated as these lines tend to have high loads and large d/t ratios. “It is absurd to use FEA on every system, and it is absurd not to use it at all.” Copyright (c) 2007 by Paulin Research Group

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Chapter 1 – Section 3 Sample Problems Several examples illustrate. (Details for each example are included in a separate chapter at the end.) Example Problem Description Cylindrical Junction (WRC 107) NonLoaded Small Branch Takeoff Nozzle Loads Due To FEA Flexibilities SIF’s for Nozzles in Heads Straight vs. Lateral

Small d/D WRC 107 Comparison Pad Reinforced Attachment

Difference with FEA FEA Stress 270% Higher than WRC 107 FEA Stress 500% Lower than B31.3 FEA Loads 630% Lower than Rigid Analysis FEA Stress 7.7 Times Higher than Piping Program Default Lateral 1.34 Times Stronger Than Straight Nozzle InPlane Lateral 1.7 Times Stronger Than Straight Nozzle Outplane Lateral 2.2 Times Weaker Than Straight Nozzle for Pressure FEA different from WRC 107 by 3.7% FEA Stress 1.8-to-10.0 Times Higher than WRC 107

Process Feed Line: A process feed line to a vessel cycles about every 6 hours. In 20 years this is 29,200 cycles. The number of design cycles is greater than 7000, so the safety factor against failure is as low as it can get, (about 2.0 ref: Nureg/CR-3243 ORNL/Sub/82-22252/1). The engineer decided that a good stress calculation was important since the number of cycles was high. The d/D ratio was only 0.27, but the geometry was pad reinforced. WRC calculations were not intended for pad reinforced geometries, and this is reflected in the results when the FEA calculation is compared against WRC 107. WRC 107 Stress at Junction: WRC 107 Stress at Pad Edge: FEA Maximum Stress (PL+PB+Q out) with 1.75x mesh FEA Maximum Stress (PL+PB+Q out) with 1.75x mesh

21,490.psi. 18,214.psi. 65,887 psi. (307% of WRC 107) 69,688 psi. (324% of WRC 107)

Gas Riser: The 400F 18” riser was only subject to 10 psig of internal pressure. Thermal moments produced less than 10,000 psi of stress in the pipe except at an 8” takeoff that was valved and capped. The stress at this unloaded branch connection showed to be in excess of 55,000 psi. A finite element calculation of loads through the header showed that the actual stress was less than 9,000 psi. The line was not even close to being overstressed, there was no reason for redesign or rerouting of the pipe. B31 Piping Code: Nozzle/PRO:

Se = (io)(Mo)/Z = (6.1)(1.1E6)/(120.3) = 55,777 psi Se = (io)(Mo)/Z = (1.0)(1.1E6)/(120.3) = 9,143 psi

So the actual stress is 1/ 5th B31 Value Nozzle Loads: Using rigid anchor assumptions, the conservatively estimated loads on the vessel nozzle were in excess of 344,844 ft. lb. When flexibilities were inserted at the nozzle, the moments due to the piping loads dropped to 53,981 ft.lb., a

reduction of 153 times.

Allowable Loads and Pressure MAWP: The process engineer wanted to slope the process vent lines into the header to improve flow and reduce the potential backpressure buildup in the header. He didn’t want to create a much weaker junction, however by using a connection at 45 degrees. He wanted to know which of the connections was stronger for bending moments – the straight 90 degree intersection, the 45 lateral, or the hillside connection. The vent header was 24” x 0.375” wall, and the vent outlet was 16” x 0.375” wall. The results from NozzlePRO are shown below and confirm what is generally known about these intersections. The larger footprint of the lateral improves the moment carrying capacity, but cuts a larger hole in the header in the longitudinal direction increasing the hoop stress effect. The hillside in this d/D ratio performs essentially as well as the straight through intersection. Copyright (c) 2007 by Paulin Research Group

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InPlane Max Allowed Moment Outplane Max Allowed Moment Maximum Allowed Pressure

Straight Through

Lateral (45)

Hillside

B31.3

583,179 in.lb. 171,867 in.lb. 348 psi

786,243 in.lb. 304,402 in.lb. 160 psi

451,108 in.lb. 191,997 in.lb. 326 psi

495,658 in.lb.1 385,698 in.lb. n/a

Good Comparisons with WRC 107: The engineers were concerned that some of the results from the FEA calculation were different from WRC 107 programs. When calculations are run that keep the limits of the WRC 107 approach in mind, the comparisons are much better. Leaving out pressure effects, (which are not included in WRC 107), using a small d/D, only a single moment loading, and a t/T ratio greater than 1.0, the comparisons between FEA and WRC 107 are much better: Stress (psi) WRC 107 FEA tn=0.5” FEA tn=0.9” FEA tn=1.5”

126,677 150,765 144,522 131,579

Rectangular Attachments (WRC 107): As might be expected, WRC 107 for a rectangular attachment that has essentially the same dimensions in the longitudinal direction as the 8” pipe above produces essentially the same stress. The FEA model shows higher stresses around the corners of the geometry where the stress is concentrated. The FEA model also shows the beneficial effect of pads and the gross errors that can occur when WRC 107 is used for pad type attachment geometries. WRC 107 Pad Lug (1) (2) Edge Edge 141,818 n/a 43,215 90,929 43,215 34,639 43,215 22,619 43,215 22,619 43,215 22,619

Line Load(3) Lug Pad (1) (2) Edge Edge 111,139 n/a 39,462 67,989 39,462 24,909 39,462 15,619 158,145 15,619 299,006 15,619

6x8 Rectangle No Pad 6x8 Rectangle 1” Wide Pad 6x8 Rectangle 4” Wide Pad 6x8 Rectangle 6” Wide Pad 6x8 Tri Plate Supt. 6” Wide Pad 6x8 Inverted Tee 6” Wide Pad Notes: (1) Simulated by increasing vessel thickness. (2) Simulated by increasing Load Bearing Area. (3) Ref: H. Bednar, Pressure Vessel Design Handbook, Van Nostrand, New York, 1981.

Box (no Pad) (129,813)

Box (1” Pad) (71,197)

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FEA Lug (1) Edge 129,813 71,197 46,775 41,299 42,311 75,275

Pad (2) Edge n/a 70,604 30,960 24,257 24,358 24,631

Box (4” Pad) (46,775)

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Box (6” Pad) (41,299)

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Triple-Plate (42,311)

Inverted Tee(75,275)

Example 6 – Using FE/Pipe and Nozzle/PRO SIFs in Pipe Stress Programs: ASME B31 SIFs published in 1955 were determined experimentally using tees having the same branch diameter and thickness as the header diameter and thickness (d/D = 1 and t/T = 1). The ASME later (1965) introduced a correction factor for branch stresses when d/D < 1. The original SIF equations are still used by the codes: io = (0.9)[(tH)/(RmH)]2/3. > 1.0 ii = (0.675) [(tH)/(RmH)]2/3 + (0.25) > 1.0 FE/Pipe and Nozzle/PRO Stress intensification factors use the WRC 329 definition of “if”, or “ifailure”: These SIFs are based on the actual nozzle section modulus and do not require adjustment for branch connections smaller than the header.

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1.3.3

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Chapter 1 – Section 4 Sample Problem Details Example 1 - Process Feed Line (Pad Reinforced Nozzle) A process line to a vessel cycles about every 6 hours. In 20 years this is 29,200 cycles. The number of design cycles is greater than 7000, so the safety factor against failure is as low as it can get (about 2.0 ref: Nureg/CR3243 ORNL/Sub/82-22252/1). The engineer decided that a good stress calculation was important since the number of cycles was high. The d/D ratio was only 0.27, but the geometry was pad reinforced. WRC calculations were not intended for pad reinforced geometries, and this is reflected in the results when the FEA calculation is compared against WRC 107.

Geometry Vessel: 72” ID x 0.625” wall (73.25” OD) Nozzle: 20”OD x 0.5” with a 5” wide pad 0.625” thick

Loads Local MX = 3E6 in lb, Local MY = 2.79E5 in lb, Local MZ = 6E5 in lb

Model Geometry and coordinates are illustrated below. The blue axes show the Global coordinates (of the overall model), and the black coordinates show the Local Load coordinates (for the nozzle).

Building the Nozzle/PRO Model (Build and analyze in 6 steps) Step 1 of 6 Start Nozzle/PRO by double-clicking the desktop Short/Cut

Double clicking this icon should bring up the program screen below. If this screen does not appear or if the options are different than displayed, send an Email to [email protected] with a description of the problem.

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Step 2 of 6 Select Input Units (English or SI) For this example select “English” units

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Step 3 of 6 Select a “Base Shell Type” and input “Vessel” Dimensions For this example select “Cylinder” and input the vessel OD and wall thickness

Note these inputs are described in the images below

Step 4 of 6 Select a “Nozzle/Attachment Type” and input the dimensions For this example select “Pad” and input the Nozzle and Pad dimensions.

Note these inputs are described in the images below

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Step 5 o f 6 Input Loads Click the “Loads” button and the following screen should appear. Input the loads and use “locally” defined loads (convert to ft lb ) (Using local coordinates without direct shear loads permits the user to ignore nozzle length)

Local coordinates

Step 6 of 6 Run and Review Results This example only compares the calculated stresses of two methods. Since the objective does not include comparing stress to an allowable stress value, the allowable stress input is not used. Click “Run FE”. Once the analysis is complete, Nozzle/PRO will display a message indicating the run has finished. Click “OK”.

The Nozzle/PRO screen should appear as shown below. Output windows are described in detail in Chapter 3 Section 1, with additional instructions on how to use the 3d graphics window in Chapter 2 Section 3. For this example review plot “2) PL+PB+Q < 3Smavg (OPE outside) Case 1”

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Discussion of Results The finite element model and results plots are shown below:

WRC 107 Stress at Junction: WRC 107 Stress at Pad Edge: FEA Maximum Stress (PL+PB+Q out) with 1.75x mesh FEA Maximum Stress (PL+PB+Q out) with 1.75x mesh

21,490.psi. 18,214.psi. 65,887 psi. (307% of WRC 107) 69,688 psi. (324% of WRC 107)

FEA is 3.2 times higher than WRC 107 This is a typical problem when WRC 107 is used for a geometry it was not originally intended to address. Before the repad was added to the geometry, the t/T ratio was 0.5/0.625=0.8 < 1.0, and the high stress was in the vessel and WRC 107 would do a reasonable job of estimating the stress for this d/D ratio. With a 0.625” repad, the t/T ratio becomes: 0.625 / (0.5+0.625) = 0.555, and the high stresses move into the nozzle. Since WRC 107 does not calculate the stress in the nozzle, this high stress was completely missed. Over the years WRC 107 has been used for pad reinforced geometries since no other tools were available. Two analyses are typically made for pad reinforced nozzle geometries. One is for the edge of the repad. The nozzle OD is increased to equal the pad OD and the WRC 107 analysis run with the larger nozzle. For WRC 107 cylinder-to-cylinder intersections the thickness of the nozzle does not enter into the calculation. The second calculation is made with the actual nozzle Copyright (c) 2007 by Paulin Research Group

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OD and the increased local thickness of the vessel and pad. Parameter studies are under way to determine when this approach will produce the worst results, but large errors have been witnessed for certain geometries. This is not the fault of the WRC 107 bulletin. The bulletin has simply been extended beyond its intended range of usefulness by programmers needing to find solutions for problems in all parameter ranges.

Example 2 - Gas Riser The 400F 18” riser only saw 10 psig of internal pressure. Thermal moments produced less than 10,000 psi of stress in the pipe except at an 8” takeoff that was valved and capped. The stress at this unloaded branch connection showed to be in excess of 55,000 psi. A finite element calculation of loads through the header showed that the actual stress was closer to 9,000 psi. The line was not even close to being overstressed. There is no reason for redesign or rerouting of the pipe.

Geometry Riser Pipe: 18” OD x 0.5” wall Branch Pipe: 8.625 x 0.5” wall

Loads Pressure: 10 psig Thermal Expansion (outplane) Moment: Mo = 1.1E6 in lb. (450°F Furnace Gas)

Determine the “Header” SIF for the Overhead Line in 6 Steps Step 1 of 6 Start Nozzle/PRO by double-clicking the desktop Short/Cut Step 2 of 6 Select Input Units (English or SI) For this example select “English” units

Step 3 of 6 Select a “Base Shell Type” and input “Vessel” Dimensions In this example select “Cylinder” and input the vessel OD and wall thickness

Note these inputs are described in the images below

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Step 4 of 6 Select a “Nozzle/Attachment Type” and input the dimensions In this example select “Straight” and input the Nozzle dimensions.

Note these inputs are described in the images below

Step 5 of 6 Change the OPTIONS screen to calculate header or “header” SIFs This will set the basis of the calculation to be loads through the header rather than the branch. Click “OK” when finished to close the Options window.

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Step 6 of 6 Run and Review Results This example only computes stress intensification factors. Since the objective does not include comparing stress to an allowable stress value, the allowable stress input is not used. Click “Run FE”. Once the analysis is complete, Nozzle/PRO will display a message indicating the run has finished. Click “OK”.

The Nozzle/PRO screen should appear as shown below. Output windows are described in detail in Chapter 3 Section 1, with additional instructions on how to use the 3d graphics window in Chapter 2 Section 3. For this example review plot “2) PL+PB+Q < 3Smavg (OPE outside) Case 1”

A portion of the stress intensification factor report is shown below. The values to be used in a pipe stress analysis are the peak stress intensification factors. The primary and secondary SIF’s should be ignored for B31 applications, (there is no place is in the B31 Codes to use them.). Any SIFs calculated that are less than one should be increased to one before they are used. (See the torsional SIF below.) It is not unusual that a component is stronger than a girth weld in the attached pipe. (This is what the SIF is based on.) FEA results echo this result. If the component is big and thick, compared to the attached pipe, then the SIF could easily be less than 1.0. SIF’s less than 1.0 should never be used in a pipe stress analysis however. Always increase the value to 1.0 before using it. Stress Intensification Factors Branch/Nozzle Sif Summary

Axial : Inplane : Outplane: Torsion : Pressure:

Peak 1.991 1.846 0.503 3.146 0.000

Primary 2.004 1.801 0.974 4.539 0.000

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Secondary 2.949 2.735 1.007 4.660 0.000

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Compare with B31 Piping Code Stress Calculation Expansion Stress is calculated using the following equation Se = (io)(Mo)/Z

r2 = (0.5)(18 – 0.5) = 8.75 Z = (π)(r22)(T) = (π)(8.752)(0.5) = 120.3 io = 0.9/(T/r2)(2/3) = (0.9)/(0.5/8.75)(2/3) = 6.066 ~ 6.1

B31 Piping Code: Nozzle/PRO:

Se = (io)(Mo)/Z = (6.1)(1.1E6)/(120.3) = 55,777 psi Se = (io)(Mo)/Z = (1.0)(1.1E6)/(120.3) = 9,143 psi

So the actual stress is 1/ 5th B31 Value Discussion This problem is discussed in E.C. Rodabaugh’s WRC Bulletin 329. The results from the pipe stress analysis are shown below along with the FE/Pipe finite element result (Nozzle/PRO can not apply loads to the header).

The displaced shape of the piping model shows that the intersection is subject to outplane bending moments through the header (in fact the branch only supports the weight of the valve). The B31 piping codes do not make any differentiation between SIF’s for the header or branch at an intersection. Because of the overly-conservative assumptions in the piping code, a SIF of 6.1 is used by default at this intersection. The FEA analysis of the outplane moment shows that this SIF is actually be 1.0. (The nozzle on the side of the header does not sufficiently increase the stress above the maximum value at the outer fiber removed from the nozzle.) This is true for all nozzles with smaller d/D ratios. The stress for this problem as calculated incorrectly by the piping codes (see WRC 329) will be 6.1 times higher than it should be, and expensive rerouting or alternate supporting of the system might result unnecessarily. Appendix D of the B31 piping codes states that “Stress intensification and flexibility factor data ... are for use in the absence of more directly applicable data...” In this case, more directly applicable data (i.e., FEA analysis) and similar recommendations from WRC 329 could be used to avoid rerouting the piping system.

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Example 3 – Allowable Loads and Pressure MAWP The process engineer wanted to slope the process vent lines into the header to improve flow and reduce the potential backpressure buildup in the header. He didn’t want to create a weaker junction however by using a connection at 45 degrees. He wanted to know which of the connections was stronger for bending moments – the straight 90 degree intersection, the 45 lateral, or the hillside connection. The vent header was 24” x 0.375” wall, and the vent outlet was 16” x 0.375” wall. The results from NozzlePRO are shown below and confirm what is generally known about these intersections. The larger footprint of the lateral improves the moment carrying capacity, but cuts a larger hole in the header in the longitudinal direction increasing the hoop stress effect. The hillside in this d/D ratio performs essentially as well as the straight through intersection.

B31.3 Calculations r2 = (0.5)(24 – 0.375) = 11.8125 rB = (0.5)(16 – 0.375) = 7.8125 B

2 Ze = (π)(rB )(T)

= (π)(7.81252)(0.375)

= 71.9

io = 0.9/(T/r2)(2/3) = (0.9)/(0.375/11.8125)(2/3) = 8.98 ii = 0.25 + (0.75)(io) = 6.98 Se = (i)(M)/Ze < Sa Sa = 1.25(Sc+Sh) (SL assumed = 0 for simplicity) Let Sc = Sh = 20 ksi Sa = 1.25(20ksi + 20ksi) = 50ksi Mi < SaZe/ii=(50000)(71.9)/6.98 = 515043 in.lb. Mo < SaZe/io = (50000)(71.9)/8.98 = in.lb.

Straight Through

Lateral (45)

InPlane Max Allowed Moment 583,179 in.lb. 786,243 in.lb. Outplane Max Allowed Moment 171,867 in.lb. 304,402 in.lb. Maximum Allowed Pressure 348 psi 160 psi Note (1): For B31.1 the Inplane and outplane moments are the same.

Hillside

B31.3

451,108 in.lb. 191,997 in.lb. 326 psi

495,658 in.lb.1 385,698 in.lb. n/a

The allowable load report report from NozzlePRO lets the user directly compare fittings and geometries as was done above. An example allowable load report for one of the nozzles above is shown below. Allowable Loads SECONDARY Load Type (Range): Axial Force Inplane Moment Outplane Moment Torsional Moment Pressure

(lb. ) (in. lb.) (in. lb.) (in. lb.) (psi )

Maximum Individual Occuring 43881. 583179. 171867. 598463. 348.73

Conservative Simultaneous Occuring 11228. 105101. 30957. 145044. 100.00

Realistic Simultaneous Occuring 16841. 222953. 65671. 217566. 100.00

(lb. ) (in. lb.) (in. lb.) (in. lb.) (psi )

Maximum Individual Occuring 67023. 514214. 377181. 334385. 240.90

Conservative Simultaneous Occuring 17594. 72906. 51998. 66047. 100.00

Realistic Simultaneous Occuring 26391. 154657. 110303. 99071. 100.00

PRIMARY Load Type: Axial Force Inplane Moment Outplane Moment Torsional Moment Pressure

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The results obtained were expected. There is not enough experience with hillside nozzles yet to draw any conclusions from the above results. Tests and Code data produced to date cover too limited a scope to permit any general conclusions to be drawn.

Example 4 – Rectangular Attachments (WRC 107): As might be expected, WRC 107 for a rectangular attachment that has essentially the same dimensions in the longitudinal direction as the 8” pipe above produces essentially the same stress. The FEA model shows higher stresses around the corners of the geometry where the stress is concentrated. The FEA model also shows the beneficial effect of pads, and the gross errors that can occur when WRC 107 is used for pad type attachment geometries. WRC 107 Pad Lug Edge(2) Edge(1) 141,818 n/a 43,215 90,929 43,215 34,639 43,215 22,619 43,215 22,619 43,215 22,619

Line Load(3) Lug Pad Edge(1) Edge(2) 111,139 n/a 39,462 67,989 39,462 24,909 39,462 15,619 158,145 15,619 299,006 15,619

6x8 Rectangle No Pad 6x8 Rectangle 1” Wide Pad 6x8 Rectangle 4” Wide Pad 6x8 Rectangle 6” Wide Pad 6x8 Tri Plate Supt. 6” Wide Pad 6x8 Inverted Tee 6” Wide Pad Notes: (1) Simulated by increasing vessel thickness. (2) Simulated by increasing Load Bearing Area. (3) Ref: H. Bednar, Pressure Vessel Design Handbook, Van Nostrand, New York, 1981.

Geometry: Vessel

FEA Lug Edge(1) 129,813 71,197 46,775 41,299 42,311 75,275

Pad Edge(2) n/a 70,604 30,960 24,257 24,358 24,631

ID = 72” T=0.625”

Loads: Longitudinal Moment = 45000 ft.lb. (540,000 in.lb.)

Rectangular Attachments in 5 Steps Step 1 of 6 Start Nozzle/PRO by double-clicking the desktop Short/Cut Step 2 of 6 Select Input Units (English or SI) For this example select “English” units

Step 3 of 6 Select a “Base Shell Type” and input “Vessel” Dimensions In this example select “Cylinder” and input the vessel OD and wall thickness

Copyright (c) 2007 by Paulin Research Group

1.4.11

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Step 4 of 6 Select a “Nozzle/Attachment Type” and input the dimensions In this example select “Structure 6” and input the Structure dimensions.

Note these inputs are described in the images below

Step 5 of 6 Select “Loads” and input the loads and/or monments In this example input 45000 in the MZ (ft.lb.) and click O.K.

Step 6 of 6 Run and Review Results Click “Run FE”. Once the analysis is complete, Nozzle/PRO will display a message indicating the run has finished.

The results discussed above clearly demonstrate that care must be taken when using WRC 107 for pad reinforced structural attachments. Depending on how the analyst views the WRC 107 evaluation of the connection significant errors could be made. The value (RT)1/2 should be used as the minimum pad width if at all possible, (where “T” is the sum of the pad and header thicknesses.) (WRC 297 recommends using the value 1.67(RT)1/2) (RT)1/2 is the width of the pad away from the nearest edge of the structural attachment. For rectangular shapes, running the support plates right up to the edge of the pad completely eliminates the repad usefulness. Inverted tee supports Copyright (c) 2007 by Paulin Research Group

1.4.12 12

NozzlePRO

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produce twice the stress of the rectangular plate supports, which more evenly distribute the stress over the pad. NozzlePRO is particularly useful at evaluating the stresses due to different geometric shapes. Only the single structural type parameter needs to be changed to alter the support cross section: are automatically distributed evenly over the outer section of any cross section selected.

Box (no Pad) (129,813)

Box (1” Pad) (71,197)

Box (6” Pad) (41,299)

Triple-Plate (42,311)

. The entered loads

Box (4” Pad) (46,775)

Inverted Tee(75,275)

Example 5 – Using FE/Pipe and Nozzle/PRO SIFs in Pipe Stress Programs: ASME B31 SIFs published in 1955 were determined experimentally using tees having the same branch diameter and thickness as the header diameter and thickness (d/D = 1 and t/T = 1). The ASME later (1965) introduced a correction factor for branch stresses when d/D < 1. The original SIF equations are still used by the codes: io = (0.9)[(tH)/(RmH)]2/3. > 1.0 ii = (0.675) [(tH)/(RmH)]2/3 + (0.25) > 1.0 FE/Pipe and Nozzle/PRO Stress intensification factors use the WRC 329 definition of “if”, or “ifailure”: These SIFs are based on the actual nozzle section modulus and do not require adjustment for branch connections smaller than the header. For example:

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Comparing SIF usage for Expansion Stress, SE Using “Appendix D” SIF ASME B31.1 For (0.75ioB31)(tB)/(tH)1.0 ASME B31.3 For (ii)(tB)/(tH) < 1.0 For (ii)(tB)/(tH) > 1.0

Using “FE” SIF

[Mi2 + Mo2 + Mt2]0.5/( π RmB2 tB)

(ioFE)[Mi2 + Mo2 + Mt2]0.5/( π RmB2 tB)

(ioB31) [Mi2 + Mo2 + Mt2]0.5/( π RmB2 tH)

(ioFE)[Mi2 + Mo2 + Mt2]0.5/( π RmB2 tB)

[Mi2 + Mo2 + Mt2]0.5/( π RmB2 tB) [(ioB31 Mo)2+(iiB31 Mi)2+Mt2]0.5/(πRmB2tH)

[(ioFE Mo)2+(iiFE Mi)2+(Mt)2]0.5/(πRmB2tB) [(ioFE Mo)2+(iiFE Mi)2+(Mt)2]0.5/(πRmB2tB)

B

B

B

B

B

B

B

B

B

B

Under certain conditions pipe stress programs do not distinguish between test SIFs (“if”) and B31 SIFs. If the pipe stress program adjusts the FE/Pipe SIFs, bending stress in the branch will be under predicted by the ratio (tB/tH). The following graph puts this in terms of actual pipe sizes: error is plotted is for standard thickness branch connections on a 20inch std. wall header. B

...Numerical Example: NPS 20 x 4 un-reinforced branch connection (std wt, all) Shell Type: Diameter Wall thickness

cylinder 20 inches 0.375 inches

Nozzle/Attachment Type: Diameter Wall thickness

Straight 4.5 inches 0.237 inches

... For SIF generation, leave all other parameters at defaults

Nozzle/PRO Branch SIFs: Inplane 4.04

Outplane 7.42

Torsion 1.43

Axial 11.63

Note: For strict comparison to the ASME B31.3 Code, the axial, pressure and torsional SIFs are ignored. For this reason pipe stress programs only match complex finite element models when the loads are dominated by inplane moments or outplane moments. When a branch connection has high axial or torsional loads or complex load combinations, the pipe stress model and the finite element calculation will predict different stresses.

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Checking Pipe Stress Model It is important to understand how your pipe stress program is using Nozzle/PRO SIFs. A test model was built in Caesar II to illustrate how FEA SIFs can be incorrectly applied. Later it is shown how to adjust Caesar’s input to get the correct result. To make verification easier, only a single moment is applied to a simple system shown in the figure below. Using the same diameters and thickness, the remaining Caesar II model details are as follows (1) All three elements are 40” long. (2) The intersection is defined as an “un-reinforced tee” with user input SIFs (3) A concentrated in-plane moment of 2685.8 ft-lb is applied to node 40 (no pressure, no weight, etc). (4) The only restraint in the model is the anchor at node 10

Manual calculation of ASME B31.3 expansion stress: Se = (ii)(Mi)/Z = (4.039)(12)(2685.8)/(3.214) = 40503 psi (86% of allowable stress)

Pipe Stress Program Code Compliance Report: NODE

20

Bending Stress lb./sq.in. 24327.0

Torsion Stress lb./sq.in. 0.0

SIF In Plane 4.040

SIF Out Plane

Code Stress lb./sq.in.

7.420

24327.0

Allowable Stress lb./sq.in. 50000.0

Ratio %

48.7

Caesar’s output is correctly reporting the user’s SIF, but the expansion stress is 40% lower than the manual calculation. The ratio of (tB/tH) is 0.63, which is about the same as the ratio of the stresses within rounding errors. So we know the reason for the difference is that the reduced branch intersection rules are being applied. B

The same loads input into the Nozzle/PRO model give an expansion stress (SE = PL+PB+Q+F) of 40,500 psi (plot below)... so the Caesar II result with the FEA SIF is incorrect. There are two avenues to correct this result: (1) increase the FEA SIF to counter the pipes tress program’s “Ze” adjustment, or (2) Somehow deactivate the B31 reduced intersection calculation.

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Finite Element “SE” Stress Distribution Option 1: Increase SIF to Counter-act the “Ze” Correction: This option is simplest, but often conservative for header moments. Nozzle/PRO SIFs are adjusted by multiplying by (tH/tB) as shown: B

Nozzle/PRO Branch SIFs:

FEA “Adjusted”

Inplane 4.04 6.39

Outplane 7.42 11.74

Generating SIFs for loads applied through the header: Step 1 of 2: – Select the “Options” Menu:

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Step 2 of 3: Select “SIF’s and K’s for Cylinder Header”

Step 3 of 3: Run Model and Review Results Nozzle/PRO Header SIFs

FEA “Adjusted”

Inplane 1.58 2.5

Outplane 0.37 (1) 0.58 (1)

SE in header: Nozzle/PRO SIF: Se = (ii)(Mi)/Z = (1.576)(12)(2685.8)/(113.433) = 447.8 psi Adjusted FE SIF: Se = (ii)(Mi)/Z = (2.494)(12)(2685.8)/(113.433) = 708.6 psi Option 2: Turn off the “Ze” correction. In Caesar II, the user can turn off the Ze correction locally by not specifying an intersection type. There are two drawbacks to this approach: (1) When the SIF type is not defined, SIFs must be defined on all three elements (2) The user must now confirm the inplane and outplane directions. Branch and header SIFs input as shown (per intuition), give a correct branch stress, but not a correct header stress.

element 10-20

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element 20-30

element 20-40

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NozzlePRO

ELEMENT

10 – 20 @ 20 20 – 30 @ 20 20 – 40 @ 20

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Bending Stress lb./sq.in. 289.5 0.0 40506.8

Torsion Stress lb./sq.in.

SIF In Plane

SIF Out Plane

0.0

1.600

1.000

0.0 0.0

1.600 4.040

1.000 7.420

Code Stress lb./sq.in.

289.5 0.0 40506.8

Allowable Stress lb./sq.in. 50000.0

Ratio %

50000.0 50000.0

0.0 81.0

Allowable Stress lb./sq.in. 50000.0 50000.0 50000.0

Ratio %

Allowable Stress lb./sq.in. 50000.0 50000.0 50000.0 50000.0

Ratio %

0.6

The same error occurs in the branch if the model is rotated 90 degrees about the x-axis:

ELEMENT 10 – 20 @ 20 20 – 30 @ 20 20 – 40 @ 20

Bending Stress lb./sq.in. 289.5 0.0 74396.0

Torsion Stress lb./sq.in. 0.0 0.0 0.0

SIF In Plane 1.600 1.600 4.040

SIF Out Plane 1.000 1.000 7.420

Code Stress lb./sq.in. 289.5 0.0 74396.0

0.6 0.0 148.8*

The correct result is only obtained by switching the SIFs from inplane to outplane: ELEMENT 10 – 20 @ 10 10 – 20 @ 20 20 – 30 @ 20 20 – 40 @ 20

Bending Stress lb./sq.in. 289.5 463.1 0.0 40506.8

Torsion Stress lb./sq.in. 0.0 0.0 0.0 0.0

SIF In Plane 1.000 1.000 1.600 7.420

Copyright (c) 2007 by Paulin Research Group

SIF Out Plane 1.000 1.600 1.000 4.040

Code Stress lb./sq.in. 289.5 463.1 0.0 40506.8

0.6 0.9 0.0 81.0

1.4.18

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Chapter 1 – Section 5 How to Get Help Help is available via email from [email protected]. Submit the file .nozzlepro and a description of the problem or question along with the Serial Number ie. NP-XXXXX. One of several routes may then be pursued. If the question can be answered directly, a response will be returned immediately. If some further work is required then a different file may be returned. In general, only a small amount of mesh adjustment is ever needed, and the improved mesh is returned with instructions on how to rerun the model. If you have the latest version of FE/Pipe you can similarly operate on the existing input by moving the NOZZLE.ifu file for 3d shell models, or the SETUP.IFU file for axisymetric 2d and brick models from the \OUTPUT folder into a new data directory, and then starting a new job with the name NOZZLE or SETUP. The jobname should be changed from NOZZLE and SETUP to something more meaningful to the user. d will only have to be done once.

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Chapter 2 – Section 1 Getting Started, Printing Reports, and File Handling When NozzlePRO is properly unlocked it will startup as shown below: (When NOT unlocked the word DEMO will appear across the window handle on the top of the screen and input will be limited.) If the words DEMO

show up across the top of the window handle DO NOT USE the results of the PROGRAM for engineering evalutions!

Begin by selecting the base shell and nozzle or structural attachment types, the units to be used and whether or not the shell material should be the same as the nozzle material. Once these inputs are chosen, for a straight nozzle in a cylindrical shell the main NozzlePRO form will appear as shown below:

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Only the text fields described by black labels are required. Blue text labels are optional. Enter a 20 inch outside diameter cylinder with a 1.0 inch wall, and a 10 inch diameter nozzle with a 1.0 inch wall. This input is shown below:

Click on the Loads button, and then enter a pressure of 100 psi. Leave the rest of the fields blank.

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Click OK, then click the Plot Only button on the main form. A separate window with the plotted finite element model should appear on top of the main plot form as shown below.

The model should now be ready to run. Close the plot window by using the in the upper right corner of the plot window, or by using file:close. From the main form click on Run FE. A data check will be performed and the following dialog box should appear:

Click on OK, and depending on the speed of your machine the run will take between 1-to-10 minutes. A status bar will be shown in the middle of the main form, and plotted results will show up intermittently. When the run finishes the two bottom panels on the main form will be replaced by a web browser window with the NozzlePRO output displayed.

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The output appears in three separate browser panes. The form may be maximized to get a better view of the output. Additionally the user may select “Graphical Results” from the leftmost pane (on the bottom in the image above), and a separate browser window will be brought up that contains only the graphical results. (The user can then toggle back and forth between the graphical and tabular results windows.) The vertical bar in the middle of the three panes can be moved using the mouse so that the full tabular results screen can be shown. The image below shows a maximized window with the tabular results bar stretched to the right and font size “4” selected. The tabular results have been scrolled down to the ASME Overstressed Areas Report.

Separate buttons appear with each graphical plot that let the user invoke a 3-dimensional view of the stress state displayed. The “3d Deformed” view of the pressure (Pl) stress state is shown below: Copyright (c) 2007 by Paulin Research Group

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The 3d viewer was designed to let the user “hold the dynamically moving model” in his or her hand. The stress state may be rotated, zoomed, clipped, scaled or a thermometer may be used to selectively view the actual value of the stress state. If the load case selected has an associated displacement case, then the model will be shown dynamically displacing. The style of the dynamic displacement can be adjusted using the cockpit controls on the right side of the window. The 3d viewer uses DirectX technology. Version 7.0a or later of DirectX must be loaded on the host machine. (Windows2000 loads version 8.0 as part of the operating system.) Hold the left mouse button down and move the mouse to rotate the geometry. Dragging the right mouse button “pans” the geometry. The 3d Viewer is discussed in more detail below but is designed to be “played-with.” Users are encouraged to test the different features to get a “feel” for what works best for them. Each output report is discussed in detail in the Output Review section below. Hopefully, a good portion of the key is shown NozzlePRO input and output is self-explanatory. Where help is available on an input form a next to the input text box. An example form with help, and the associated help window is shown below:

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Most of the input for the default 3D shell calculation is self-explanatory. Particular items of engineering interest are discussed below. Input for Axisymetric brick and 2d element models are described later.

Load Definitions: Operating loads should include the weight loads. The operating loads are the total loads that act on the intersection through the branch or attachment in the operating condition – usually the thermal plus pressure plus weight load case. Loads are applied at the end of the nozzle or attachment and are typically the values that would be read directly from a pipe stress or structural steel program. These loads do not include the P*A axial component due to pressure for pipe. The P*A load is included automatically by NozzlePro in addition to any other loads applied to the pipe nozzle. Loads are distributed across the structural attachment cross-section end in a manner consistent with the beam analogy. (Users do not have to be concerned with boring degrees of freedom, torsional moments, or shear loads causing excessive bending in the structural shape. Vertical shear loads are distributed over longitudinal plate members, for example. Moments on structural attachments are provided as a force couple where practical or as a linearly varying force over single members. NozzlePRO calculates the difference between weight and operating loads as the “range” case required as part of the ASME Code secondary stress shakedown evaluation procedure. The difference between the weight and operating loads is also used to find the cyclic stress and is used in the ASME Code fatigue analysis. If there are significant weight and pressure loads but no thermal loads then the operating and weight loads should be the same. In this case the only load quantity causing cyclic stress is pressure – and pressure must cycle at least once. The ASME Section VIII Division 2 Code directs that occasional loads should be combined with weight, pressure and other mechanical loads, and that the resulting stresses should be compared to 1.5(k)(Sm), where k=1.2, and Sm is the hot allowable for the material. The user should leave the Occasional Cycles data cell blank or zero to effect this evaluation. (The Occasional Cycles data cell is found on the Advanced Options Screen.) When the Occasional Cycles data cell is blank or zero the occasional load entered should be the largest signed component of the occasional load. In general this is the magnitude of the wind or earthquake load. NozzlePRO will treat the occasional load as a fatigue-causing load only if the user enters the number of occasional cycles. In this case the user should enter the number of occasional cycles and the full range of the occasional loading. Whenever NozzlePRO sees a nonzero number of occasional cycles it treats the occasional load as a full range cyclic load component. Earthquake loads, for example, are often evaluated as fatigue causing loads with 100 cycles. To evaluate an earthquake load as cyclic, the user should enter the full range of the load, usually twice the value from a static seismic pipe stress analysis.

Geometry:

The user should always check the mesh produced by NozzlePRO before running a job. The element grid should be reasonably uniform without holes, doubled over areas, or obvious geometric anomalies. If the output is reasonable, the mesh typically is too. A wide variety of geometries have been tested with the NozzlePRO mesher, but certain constructions may still cause errant meshes. A large number of mesh control options exist wit7•h version 4.0 of NozzlePro, but users suspecting mesh related problems are encouraged to email the model to [email protected]. (The model file is stored as .nozzlepro.) After only a little experience reviewing finite element results users will have sufficient experience to know when results are errant and due to mesh-related problems. For spherical, elliptical, dished and conic heads, and for cylindrical geometries with structural attachments, the user can optionally use the unstructured mesher. Structured meshes are preferable, but in certain cases unstructured meshes produce better results. A comparison between structured and unstructured meshes is shown below:

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The unstructured mesh option and several other mesh controls are available on the Options form:

The Crude Mesh check box will cause the program to use the coarsest mesh possible. The Opt. Mult box lets the user enter a value that will multiply the default mesh. Any value greater than 0.01 may be entered but users are cautioned against inputing values much greater than 2. (Usually values of 1.5 to 1.8 work best.) As a rule of thumb, the element side length immediately adjacent to a discontinuity should be smaller than (RT)1/2, where R is the mean radius and T is the thickness. (This is the side of the element that is pointing away from the discontinuity. Element sides parallel to the discontinuity can generally be larger. The required size of the element is a function of the variation in the stress/deflection state.) For head geometries the straight flange, transition and shell lengths can be omitted if desired, but it is recommended that at least (3)(RT)1/2 of shell length be added to any head boundary. Conversely – just because there is 20ft. of 48” diameter shell attached to a 48” diameter head – there is no reason to enter 20 ft. of shell. Usually only 3- to 4- times (RT)1/2 needs to be entered down the shell length to accurately trap discontinuity stresses in the vicinity of a nozzle or attachment on the head. When the d/D ratio is large, the nozzle may distort the cross section of the head and this distortion will extend down the shell. An accurate attached shell length must be entered to properly observe this effect. Nozzle tilt angles can only be entered for cylinder or cone geometries, or for head geometries where the nozzle is off the centerline of the vessel by more than the diameter of the nozzle. The NozzlePRO and underlying geometry evaluation software make every attempt to create a viable geometry for analysis. Where assumptions or adjustments to the user’s input are made notes are printed in the Model Data report. This report should be reviewed closely for proper interpretation of the user’s data. Copyright (c) 2007 by Paulin Research Group

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Printing Reports: The Print button is activated whenever a finite element report is displayed in the browser. When the user clicks the Print button the contents of each pane are sent to the printer. (The target printer can be defined when the Windows Print Panel appears.) If the user only wants tabular reports he can right click in the tabular reports frame and then click on the Print menu selection that appears in that frame. Plotted results can only be copied to the clipboard and then “Pasted” into another document. The 3D viewer images can be sent to the clipboard by selecting Edit:Copy Image to Clipboard. The image can then be “pasted” into another document. The lighting in the 3d viewer can be adjusted to produce stunning images of the deformed and stressed model state.

The small numbers under the Print button: are used to size the print. Selecting a larger number results in the use of a large font in the tabular reports so that it can be seen easier on the screen. Selected parts of the text reports can also be highlighted and copied to the clipboard by left clicking and dragging the mouse over the desired text to highlight it. Once the desired text is highlighted, the right mouse button can be used to copy the text to the clipboard.

Files: NozzlePRO has a somewhat unusual file system because of the variety, use, and size of the data files manipulated. The “Files” button in the middle-right of the main data screen is used to access the file system manager.

The input for Nozzle PRO is stored in the current data subdirectory under the filename .nozzlepro. The current subdirectory is always shown in the title bar of the NozzlePRO window. If the user does not enter a current subdirectory or name, then the subdirectory name NOZZLE will be chosen and established under the application root directory. Output is stored in an “\OUTPUT” subdirectory under the data subdirectory when the FEA calculation completes. The data directory is cleared when the job finishes unless the user asks for intermediate data files to be retained. The only files needed to browse output are in the \OUTPUT folder. The file structure is shown schematically below:

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When starting a new job it is best to establish the name for the datafiles where the job will be stored. Enter the new jobname in the “Input Filename:” textbox, and then click on Make “Input Filename” Current., then click on “Finished Here.” The new filename and current folder should appear in the window handle of the main form.

Version 4.0 of NozzlePRO allows the user to Edit the FE/Pipe input file, and it allows support engineers to send FE/Pipe input files back to NozzlePRO users. The FE/Pipe input file for shell models is NOZZLE.ifu and for axisymetric 2d or axisymetric brick models is SETUP.ifu. To circumvent the standard NozzlePRO file handling sequence an already existing IFU file can be placed in the \ subdirectory to be read in place of a new one. The “Use Existing FE/Pipe Input File” checkbox must be checked on the optional data form before the file will be used.

When each job is finished, the used IFU file is written to the \\OUTPUT subdirectory for storage. (Everything in the \ subdirectory is automatically deleted when the job is completed unless the user checks the checkbox to Leave FE/Pipe data files.) For the “smithco2” job above, the FE/Pipe input file would be found in the file \smithco2\OUTPUT\NOZZLE.IFU after the run. If a support engineer emailed a modified NOZZLE.IFU file back to the user it would be placed in the \ subdirectory, (e.g. \smithco2\NOZZLE.IFU) and the “Use Existing FE/Pipe Input File” checkbox would be checked so that the ifu file would be recognized and used for the subsequent run. (The IFU file is written by NozzlePRO whenever a model is plotted or run. If an IFU file already exists in the smithco2 folder and the Use Existing FE/Pipe Input File box is checked the old ifu file will be used. This is what we want if a change is made to the IFU file that should continue to be used. This is NOT what we want 99% of the time when NozzlePRO is being run in a standard mode outside of the FE/Pipe interface.) This is a convenient feature for FE/Pipe users. They can build the base model in NozzlePRO to take advantage of its smart mesh algorithms. They can use the FE/Pipe data editor to enhance the model, and then they can get the standard NozzlePRO output for reporting. A typical file structure is shown below: Data File Example Structure

Input datafile for Job N102: Intermediate Data Files: FE/Pipe Input File: FE/Pipe Input File: Output Browser Files: Output Static Plots Output 3d Models

C:\SmithConsulting\N102.nozzlepro C:\SmithConsulting\N102\*.* C:\SmithConsulting\N102\NOZZLE.IFU...put it here to use in NozzlePRO. C:\SmithConsulting\N102\OUTPUT\NOZZLE.IFU ... found here when job finishes C:\SmithConsulting\N102\OUTPUT\NOZZLE*.HTM C:\SmithConsulting\N102\OUTPUT\*.BMP C:\SmithConsulting\N102\OUTPUT\*.fex

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2.1.9

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Output 3d Results

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C:\SmithConsulting\N102\OUTPUT\*.fea

The output HTM and BMP files are written in standard file formats that can be read by any HTML browser. The standard htm files for a 3d shell model are shown and described below. (Files with the “p” prefix do not include the directX buttons .) For 2d axisymetric models the name NOZZLE is replace by the name SETUP. NOZZLE-toc.htm – Table of contents for graphic pictures. NOZZLE.htm – Body of text output report. NOZZLE-frame.htm – 3 frame htm setup file. (Point your browser to this file to get the nozzlePRO 3 frame output window just like you see it in NozzlePRO with the directX buttons displayed and active.) NOZZLE-pics.htm – Body of graphics output report that contains directX buttons displayed and active. NOZZLE-pframe.htm – 3 frame htm setup file that does NOT include the directX buttons displayed and active. (See the figure below for an example of what the directX buttons look like.) NOZZLE-ppics.htm – Body of graphics output report that DOES NOT contain the directX buttons. (This is the htm report used for printing.) NOZZLE-ptoc.htm – Table of contents for report that includes directX buttons. An example frame with the directX buttons INCLUDED is shown below:

The bmp files can be used in Microsoft WORD or any document processor. The 3d model output files can only be used with the Paulin Research Group 3d viewer. This is a nonprotected program which may be distributed freely by licensed NozzlePRO customers to their own clients for the purpose of viewing 3d results. The only job files that need to be delivered are the fex and fea files. To deliver the viewer, the files VIEWFE.EXE, DXLIB7.DLL, DXLIB8.DLL and PARTICLES.TGA must be included. When VIEWFE starts, the user may navigate between data sets to show any combination of results. VIEWFE requires that DIRECTX 7.0A or later be loaded on the host machine. Windows 2000 and XP includes DIRECTX support automatically. Windows 98 or 95 users can download DirectX from the Microsoft web site. Windows NT users must upgrade to Windows 2000 to use the 3d viewer. The test platforms at PRG are Windows 2000, Windows XP, and Windows 98.

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2.1.10

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Chapter 2 – Section 2 Common Load Types and Categories Primary Loads. Loads The nature of Primary Loads is that the load magnitude does not diminish when the structure deforms.

(Weight loads are also subdivided into “Dead” and “Live” Loads in structural steel codes) Figure 1 – Primary Load Examples

Secondary Loads.

The nature of Secondary Loads is that the load magnitude diminishes as the structure deforms. Almost always these loads are a type of restrained expansion. NOTE: The designer must be aware that this definition is temperature dependant. At temperatures in the creep range of the material, some secondary loads take on the characteristics of PRIMARY loads.

(At temperatures below the creep range)

(Restrained Thermal Expansion)

(Through Wall Temperature Gradient) Figure 2 – Secondary Load Examples

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Occasional Loads.

Occasional loads are similar to Primary Loads in that the magnitude of the load does not diminish with deformation. Occasional loads are distinguished from Primary Loads by being generally “rare” short duration events rather than continuous loads.

Wind

Acceleration (e.g., FPSO or Seismic) Figure 3 – Occasional Load Examples

Fatigue Loads:

The only requirement of a Fatigue Load is that the load has multiple repetitions (has cycles). A fatigue load can otherwise be described under any other Load Category.

Common Stress Types The complex stress state of any component can be broken down into the following sub-components.

Shear Stress.

Shear stress is a tensor component used in the calculation of principal stresses.

Figure 4 – Shear Stress Examples

Membrane Stresses. Membrane stress is a mean stress averaged through the thickness, oriented parallel to the mid surface. Circumferential and longitudinal pressure stresses in a cylinder are shown below. Membrane stresses are tensor components used in the calculation of principal stresses. Note that in the absence of shear stresses, the magnitudes of the membrane stress tensors are often identical to stress intensities. Can also be an “F/A” type of stress.

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Figure 5 – Membrane Stress Examples ...Two Kinds of Bending Stress:

Bending Stresses.

Bending stress is term with different meanings depending on the code used or the

analytical technique used. (a) Beam bending

b = (M)(y)/(I) ... (so long as total stress < yield stress) Figure 6 – Beam Bending Stress

Beam Bending Stresses. This is a longitudinal stress. In piping codes this stress is treated as a uniform stress through the thickness of the pipe (varying with position on the circumference). Note however, that torisonal shear stresses are also included in the piping codes’ bending stresses. This is also the type of bending stress reported by beam element models. (b) Shell bending Shell Bending Stresses. This is a stress that varies through the thickness. In ASME Section VIII Division 2, this is the only bending stress explicitly defined. Examples of shell bending are shown in the longitudinal and circumferential directions below. Note that in some components, such as pipe shoes or saddles, the bending stress may be oriented in directions other than just circumferential or longitudinal. This is the type of bending stress reported by shell element FE models. Axisymmetric and Brick element model results must be post processed to this same definition.

= (6)(MO)/(t2), or (6)(ML)/(t2) ** Note: direct shear is also represented as “Q” in this figure b

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= (6)(M)/(t2) Figure 7 – Shell Bending Stress Examples b

FEA Trivia Question: How are beam bending stresses represented in an FEA model? ANS: (a) For beam elements: as beam stresses. (b) For all other element types: as membrane stresses

Peak Stresses “F”: Peak stresses are related to “notch effects” and are only important for fatigue life. If there are no load cycles, then peak stresses are unimportant (except for some special environmental considerations, like SCC).

Figure 8 – Peak Stress Example (Axisymmetric Nozzle/Shell Junction)

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Stress Categories Individual Stress Intensity Components The stress components described in Section (2) above must be calculated for separate load cases and combined to determine principal stresses for each load category. Stress Intensities are computed from the principal stresses [4120.] 1> 2> 3 S12 = || 1 - 2 || S23 = || 2 - 3 || S31 = || 3 - 1 || Stress intensity = Max( S12, S23, S31) There are code limits on some individual stress intensities such as “PL” (described below). Other code limits (see 3.2) are determined by first computed combining tensor components for membrane, bending, etc, then finding the principal stresses and stress intensities.

Primary Stresses: Pm, PL, PB Primary stress can only be caused by primary loads Primary stresses lead to burst or collapse...deformations in the structure do not reduce the magnitude of primary stresses (eg. primary stresses are not “self-limiting”.) Pm = General Primary Membrane Stress [4-112(f) & (g)] PL = Primary Local Membrane Stress [4-112(i)] Pb = Primary Bending Stress [4-112(g)] Pm is (usually) not an FEA stress: Pm is satisfied by code formulas for pressure design, except for unlisted components. Pb (as a shell bending stress) is not a stress usually found in Nozzle/PRO geometries (See Table 4-120.1, of ASME Section VIII Division 2). Note: under Section III definitions, where Pb is due to beam type bending, it is considered “conservative” to include it as “PL”.

Secondary Stresses: Q Primary or secondary loads can cause secondary stress. The following cylinder cone junction under pressure loads illustrates how primary loads (pressure) cause secondary stresses:

Figure 9 – Secondary Stress Caused by Primary Loads

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Secondary Stresses are not usually subdivided in to “m”, “L” and “b” categories under Division 2, except when the “SPS” stress limit is exceeded. (See article 4-136.7 of Division II) Nozzle/PRO’s use of “Qb” for primary loads is NOT an ASME VIII Division 2 code check, it is an ASME Section III code check.

Combined Stress Intensities and Stress Intensity Ranges The code rules and limits on combined stresses are based on preventing ratcheting. Stress intensities are computed as described in (3.1). First the code rules assume that material behaves as elastic perfectly plastic (Figure 10). The possible combinations of primary and secondary stress are illustrated in the simplified diagrams of Figure 11: the left hand side is a simplified hysteresis diagram, and the right hand side is a simplified Bree diagram. The Bree diagram is a simplified illustration of the combination of primary and secondary stresses. In the code it is possible to enter the “P” range of the Bree diagram, but there is a heavy penalty on Fatigue stresses (Article 4-136.7). The code stress combinations and limits are illustrated by Figure 4-130.1 (reproduced and amplified as Figure 12)

Figure 10 – Actual and Assumed Material Behavior

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(uni-axial hysteresis) (bree diagram) Figure 11 – Simplified Material Behavior Models

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.

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Figure 12 – ASME Figure 4-130.1 Amplified

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Nozzle/PRO Load Cases and Combinations

Nozzle/PRO Stress Reports Shell Division II Stress Type Primary

ASME B31 Stress Type Sustained

Primary + Secondary – no load to operating Primary + Secondary – installation (weight) to operating Fatigue

n/a

PL+PB+Q in PL+PB+Q out

n/a

PL+PB+Q in PL+PB+Q out

SE

PL+PB+Q+F in PL+PB+Q+F out

PL

Nozzle/PRO element type Axisymmetric Brick Smembrane, Sbend1 or Sn1. Sn Sn2 (may require manual combination of multiple models) SI

SI

Notes: (1) For axisymmetric models with pressure only Sbend and Sn, may be primary depending on location in the model. (2) For axisymmetric models with transient heat transfer, the range of stress, “Sn”, must be determined by including a separate pressure case, or by the range of stresses for different temperature cases if there is a stress reversal (check deflected shape plots). (3) Brick element models are best reviewed by using Stress/Plot

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Chapter 2 – Section 3 Options Data Form

Weld Size/SCF – The two data cells to the right are used for the weld size and the associated stress concentration factor (SCF). The SCF is only used to calculate peak stresses in 3D shell models. The weld size is only used for nozzle geometries, (not structural attachments). The Weld Size is also used for the axisymetric 2d and brick nozzle models. button to see a The weld size is the leg length of the fillet weld between the header and nozzle. Click on the drawing defining the weld dimensions. The SCF (Stress Concentration Factor) indicates the increase in peak stress due to the presence of the weld geometry and the effect of welding. Generally the SCF must come from a comparison of fatigue test results and the finite element results. For PVP geometries and the element type and intersection model used in NozzlePRO an SCF of 1.35 has been found to envelop the existing fatigue test data without undue conservatism. Pad Weld/SCF – The two data cells to the right are used for the pad edge weld size and the associated stress concentration factor (SCF). This weld size is only used for nozzle geometries with pads and is also used with axisymetric 2d and brick models.

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Base Weld Leg Size – Typically the fillet weld leg length is the same along the nozzle and the header. If this is not the case then enter the length of the fillet along the header in the Base Weld Leg text box, and the length along the branch in the Weld Size text box. This option is also available for axisymetric 2d and brick models. Free POSITIVE Cylinder End – When the Base Shell Type is Cylinder the “top” of the cylinder may be freed. Any loads through the branch will be carried by the opposite side cylinder end. This is the typical boundary condition for a vertical vessel with a large nozzle. (The top of the vessel is essentially “free,” and the nozzle loads are carried through only the supported end of the vessel. This tends to produce higher stresses.) The freed end is “capped.” See the

button contents are shown below:

Free NEGATIVE Cylinder End – Mutually exclusive counterpart to POSITIVE end free option. Calculate Pressure Stress ONLY – Click on this box to have NozzlePRO ignore all other loads except pressure. Stresses will be calculated at the nozzle/shell penetration line in an attempt to trap the peak pressure stress on the inside longitudinal plane of cylindrical geometries. This option is used typically when pressure is cycling and the user is interested in a pressure only analysis. The user might consider also increasing the SCF at the nozzle welds to 1.6. This value can be adjusted based on brick model analyses of the nozzle intersection. SIF’s for Cylinder Header – For cylindrical geometries this option produces SIF’s for loads through the header. (The default is for the SIF’s to be produced for loads through the branch.) When d/D is 0.5 or less the SIF’s for moments through the header can be considerably smaller than the SIF’s for moments through the branch. The Code default is to use the same SIF for each, severely penalizing the user when the branch is not loaded. This option allows the user to enter more realistic values for header/run SIFs. Do NOT Average Stresses – Check box to turn OFF stress averaging. Stress averaging generally produces more realistic values, especially for structural attachments, but may obscure inaccuracies in the solution. Users looking closely at solutions may want to turn averaging off to get a better view of the numerically unaided stress state. Show FE/Pipe Screens During Run – Click this checkbox to see the progress of the finite element run using the FE/Pipe status screens. These screens provide more information to the user, but also take up more screen space. Often this is used to aid in debugging a run that does not run to completion. Show Intermediate Input Plots – The model plot will be displayed when the run is starting. This is included as a visual check of the job progress.

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Show Intermediate Output Plots – The model results plots will be displayed as they are created. This is included as a visual check of the job progress. Use FE/Pipe Editor During Run – Click on this check box to invoke the FE/Pipe data editor whenever the user plots or runs a NozzlePRO job. When plot or run is selected, FE/Pipe and then pauses at the FE/Pipe input data screen main menu:

NozzlePRO builds the necessary input for

From this menu, the user can modify the input using any of the options available in FE/Pipe that are available to NozzlePRO. This is used generally by the support engineer to tweak a model, or can be used by the FE/Pipe user to make quick changes to the automatically generated NozzlePRO model. AFTER changes have been made at the FE/Pipe level, the user can continue using the FE/Pipe version of the model by checking the box Use Existing FE/Pipe Input File. Leave FE/Pipe Data Files – This check box is used in conjunction with the FE/Pipe data editor box above. To continue using the same FE/Pipe input in subsequent runs the FE/Pipe input file must not be deleted. This box is also used for debugging jobs that do not complete properly. When a job aborts in error, the last data file used may give an indication of the problem. Use Existing FE/Pipe Input File – Once the user has edited an FE/Pipe input file he may want to continue to reuse those changes in subsequent runs. Click in this check box to reruse an existing input file. Note however, that NozzlePRO level changes will not be picked up if the user is running the input at the FE/Pipe data file level. These options should only be used by experts with the program or at the direction of a support engineer. Crude Mesh – Click this checkbox to use the crudest mesh possible for a given geometry. Enter a number in the box to the right as a multiplier to override the checkbox. The number entered will multiply the standard mesh density. Values can be between 0.01 and 10. The user is suggested to use large mesh multipliers with caution. Seldom are values greater than 2.0 required, and more often 1.5 –to- 1.8 is recommended. Use Unstructured Mesh for Heads or Structure – Click on this checkbox to use an unstructured mesh for spherical, elliptical, or dished heads. (Unstructured meshes may also be used for structural attachments on cylinders, but this is only recommended for shorter cylinders, where the L/D ratio does not exceed 2.) The unstructured mesh option can be used for convergence studies and in situations where the structured, parametric cubic mesher is not well suited for the geometry. Copyright (c) 2007 by Paulin Research Group

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Do NOT Use the Unstructured Mesh – There will be occasions where NozzlePRO will elect to use the unstructured mesher instead of the structured mesher. If the user would prefer to try to use the structured mesher, they can deactivate the unstructured mesher use. This is NOT recommended, and users activating these options should check the resulting element mesh and results carefully. Deactivate Element Smoothing– In certain instances the movement of nodes to form better elements results in element area overlap. Deactivate element smoothing if it is suspected that smoothing is causing this problem. This most often occurs when crude models are run. The crude model meshes are very bad to begin with, and often don’t smooth particularly well. Print Stress Outside of Discontinuity Zone – NozzlePRO was designed to find the stress around nozzle or structural discontinuities in cylinders or heads. The general stress state in the cylinder or head removed from the discontinuity is generally not of interest because the Code controls this value. Depending on the model type and d/D ratio stress artifacts may exist at boundary conditions that do not effect the stress at the discontinuity. These values are generally not printed in either the static stress plots that appear in the browser window, or in the dynamic 3D plots. If the user wishes to have the stress calculated in the entire model for the dynamic 3D plots, then the Print Stress Outside of Discontinuity Zone box should be checked. The graphical result is shown below. The tabular results will also be changed. A stress region removed from the discontinuity will be added to the report, and the highest stresses in this area reported. If a stress artifact exists at a boundary, it will be included in the report when the Print Stress Outside of Discontinuity Zone box is checked.

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Merge Nodes ToleranceThe following diagrams illustrate concepts and most common reasons to change the Nozzle/PRO defaults (1.1) Concepts

(1.2) Error “3241” = COLLAPSED ELEMENTS

Solution: input a smaller merge tolerance (see below)

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(1.3) Error “2010” = DISCONNECTED PIECE OF MODEL This error occurs if TOO SMALL a value of MERGE NODES TOLERANCE is input... (don’t over-do it)

(1.4) How to Change Merge Nodes Tolerance in Nozzle/PRO (in Two Steps) Step 1... select “OPTIONS”

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Step 2... input a “merge nodes tolerance” (for “English” units 0.005 usually works. For “SI” units, 0.1 usually works)

Insert Length – For nozzles that have inside penetrations enter the insert length. Insert nozzle end sections are perpendicular to the nozzle centerline. (Not all insert nozzles ends are perpendicular to the nozzle centerline. Some are contoured to the head. In this case the user should vary the input length to determine the sensitivity of the solution to this parameter. If a dependable solution relies on an accurate modeling of this contoured end section then a support engineer should be consulted.) Insert Thickness – The thickness of the inserted nozzle. Do Not Cut Hole in Header for Branch – Click this checkbox if the pipe does not penetrate the shell. Used when pipe is welded to cylinders or heads for support, and are not pressure carrying members. Branch Pressure – Enter a value if the branch pressure is different from the header pressure. Used for hot taps and some field welded pressure test connections when the hole is not removed from the header and the branch side may be pressurized.

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3D Shell Elements – The usual model of choice. Eight-noded reduced integration doubly curved shell elements will be used to model the requested geometry. These element models are considered a sizeable improvement over an equivalent WRC 107 or 297 type model of the same geometry. Shell elements do not consider through-thethickness direction stress gradients and tend to become more conservative when D/T ratios get in the range of 10 or smaller. Axisymetric Heads and Skirts – If this option is selected the user can set the axisymetric head and skirt options and additional loadings required using the Axisymetric Head and Skirt Options button that will become activated. The axisymetric modeler in NozzlePRO allows the user to study various through-thickness phenomena more closely, such as: 1) Contoured weld radii 2) Integral or non-integral repads 3) Skirt-to-head weld stresses 4) Effect of nozzle flanged end connections. 5) Head bed supports. 6) Welded-in Contoured Fittings. Saddle / Shoe Options – To access these options, the user must select either the saddle or pipe shoe attachment option in the main NozzlePRO screen. These options allow the user to modify the saddle or pipe shoe to account for tapered designs, multiple circumferential web plates, distance from head or front-end, and other many options. Self-weight, liquid head, and saddle forces may also be modeled for a complete and accurate mode of horizontal vessels.

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Chapter 2 – Section 4 Using the 3D Viewer DirectX may be thought of as Microsoft’s view of the 3-dimensional world. NozzlePRO models have been ported to this framework and a special viewer written to take advantage of this technology. Meshes, displacements and stresses can be viewed in “3d” much faster, and with a much better understanding of the result than with the prior “2d” slow-time rendering methods. The NozzlePRO viewer was written so that the user feels like he is holding the 3d stress/displacement model in his hand. 3D technologies are improving at an exponential rate. As engineers experience their power they will become ubiquitous on the desktop. Anyone with Windows 2000 already has sufficient DirectX 3d support to run the NozzlePRO viewer. Windows 98 and 95 support multimedia capability and also support DirectX 7.0a. The user must have a minimum of DirectX 7.0a to take advantage of this capability within NozzlePro. Users of Windows NT must upgrade to 2000 before using the 3d viewer. Microsoft never released DirectX version 7 for NT. Using the DirectX module, the user has access to translucent view, hidden-line mesh views, shaded views, scalable stress results, rotation, clipping, lighting options, and a data thermometer to read off the exact value from any point on the geometry. Viewing tools include zoom, pan, polyline, and “plane-view-zoom” options. If a displacement load case is associated with the stress state then the model will be showed in a dynamically displacing view. Controls for the dynamic displacement views are in the right screen cockpit. The DirectX models are available by clicking on the 3d viewer buttons in the stress report output pane. Examples of these buttons are shown in the plot below.

The resulting 3d Deformed model window that appears is shown below:

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Menu Options: File-Used to select different job names. When in the viewer the user can look at any 3d data file that resides on the machine. File also lets the user select various options, the most important of which is the rendering option for non-calculated vertices, usually weld zones. If the user is experiencing difficulties with the viewer, the options also permit deactivating hardware acceleration and shifting between directX7 and directX8 libraries. Data-Used to select between various possible data sets that are associated with a single model. Multiple stress states are represented by different files that can be selected and rendered with any particular geometry. The user can select which stress state to view. Rendering-Different Options for viewing the model. Most options are available from buttons on the task bar. Navigation – Lets the user select ways the mouse is used to position the model, i.e. Rotate, Zoom, Pan, etc. Most movement options define the left mouse button and drag. Most options also support a different right mouse button and drag. For example, when in rotate mode, holding the left mouse button down lets the user rotate the model, but holding the right mouse button down lets the user pan the model. The right mouse button has a duplicate function for each operation. The user should experiment with using both the right and left mouse buttons when positioning the model interactively. Clipping – Lets the user clip the model to the viewport, (the way that FE/Pipe currently does it), or to draw a polyline region to clip into or out of. The “out-of” clip essentially cuts a hole in the view. View – Lets the user set the style of the window and menus. The background color can also be selected. View also lets the user select an advanced toolbar that has an increased functionality. The experienced user is encouraged to activate the advanced toolbar and test some of its features.

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Toolbar:

Zoom and Pan – When zooming by dragging with the left mouse button, dragging the right mouse button pans the model. When panning with the left mouse button, the right mouse button rotates the model. The left mouse button is the major “mover” and the right mouse button is the secondary option “mover.”

Plane-View-Zoom – When this tool is picked the user can select any point on the model and the program will rotate and zoom the model so that the surface pointed to by the tool is normal to the user’s view. This is a useful way to rotate the model to a get a view of the stress that appears initially on the “side” of the geometry.

Rotate – When the rotate tool is picked, dragging with the left button depressed rotates the model about the vertical axis horizontally, and about the azimuth if vertically. When the right button is depressed the model can be panned.

Interactive Rotate – When picked the model will slowly rotate about the vertical axis. Generally gives a better understanding of the model.

Original View – This tool returns the model to its original orientation. Used most often after a clip to return the model to a standard viewing orientation.

Zoom In/Out – Single Hit keys to either zoom in or out one step at a time.

Clipping Tools – The leftmost tool clips the geometry to the present viewport. All elements outside of the current window are removed. The geometry is moved so that any subsequent rotation will keep the model in the lets the user create a polyline. When the tool is selected a second time the view is window. The next tool clipped to the part of the model that is enclosed by the polyline. The polyline is created by clipping on the boundaries that should be included with the view. Users should experiment with this option. The third clip tool lets the user draw an exclusion polyline. Everything outside of the polyline is kept and what is inside the polyline is disgarded. The fourth tool original unclipped model.

is activated when any clipped view is selected. This tool returns the view to the

View Option Tools – These tools change the model rendering. The leftmost tool is the most realistic rendering and shows only the shaded or stress contoured image. The second tool shows a hidden line image. The third tool shows a slightly translucent shaded image, and the fourth tool does not show hidden lines. The triangle is to not show elements that are pointing toward the viewer. This option often creates useful views when the model is complicated. The user should experiment with the view that is most suited for a particular application.

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Data Set Selection Tool – When there are multiple data sets available for a single model the user may select between them by selecting this tool. A Selection window is opened with the available data sets shown. The user must then pick between them. When all data sets have been written for a particular job, this tool lets the user pick between stress states. For example, the user can use this tool to see the Pl case, or the Pl+Pb+Q case, etc. (if write all cases is selected!!)

Data Set Scaling Tool – This is one of the most useful tools in the menu bar. As is often the case with PVP finite element results, the highest stress values are over a very small section of the model and a linear color gradient shows the entire model in blue. In these cases it is difficult to see where the high stress actually is, and to see how it is distributed in the model. The color scalar takes care of this problem. When picked the distribution of stresses is shown in a slidable graph. An example is shown below:

The user can match this plot up with the color legend that is also shown on the plot. The highest value on the color legend corresponds to the rightmost value in the graph, (the triangle on the right), and the bottom value on the color legend corresponds to the leftmost value in the graph, (the triangle on the left.) The user can pick any of the triangles on the data scalar and move it to the right or left to adjust the scaled value on the plot. Generally the rightmost triangle is selected and moved to either the allowable stress value, (watch how the color legend changes as the triangle is moved), or to the start of some convenient value so that high stress regions in the geometry can be seen conveniently. The Auto button is used to shift the center point of the Data Scaling multipliers so that have the nodes in the model are yellow or lower, and half the nodes in the model are yellow or higher.

Data Thermometer – Whenever a data set is shown, (e.g. stresses) the user can move a thermometer over the model and read the exact value of the stress at any location. Select the thermometer tool, then just move it over the model. The exact value of the stress is shown in the window border on the bottom left of the screen.

Background Color Selector – Used to pick the background color. The user can change the background color at any time. White or black is recommended.

Lighting – When the model is originally rendered a lighting is selected and applied. In some cases this casts a darker image over parts of the model and may not be desired. Clicking on the lighting tool turns OFF the preselected lighting. The user can toggle on or off lighting at any time. A slider bar appears that lets the user adjust the lighting intensity, and the light direction can be reversed. Copying and Sending 3d Data Files: It is often desireable to save and send 3d views of model results to clients or colleagues. The NozzlePRO 3d viewer is a self contained executable that is NOT copy protected and may be distributed freely by NozzlePRO licensees to their clients for the purpose of reviewing NozzlePRO results. It is

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not intended to be used by developers of other software programs to copy or otherwise imitate the methods, styles, look and feel or any other aspect of the 3d viewer. To send the 3d geometry to a customer transmit the following files: 1) Viewfe.exe,dxlib7.dll, dxlib8.dll and particle.tga from the \ subdirectory. 2) .fex and .fea files from the data \OUTPUT subdirectory – these are the 3d geometry and stress plot files for the model. Providing the client receiving the files has DirectX 7.0a or later he should be able to start up viewfe and open the .fex file. When the data file is opened, the “Data” option in the menu bar can be selected to pick the load case to review. The .fex file contains one 3d model. If the user wishes to send other 3d models, perhaps distorted or exploded views, then the other fex files should be opened. Each fex file contains the geometric description for one NozzlePRO results load case. Sending Plots to the Clipboard: Any of the views shown in the 3d viewer may be sent to the clipboard by hitting Edit: Copy Image to Clipboard. The image loaded into the clipboard may then be downloaded into Word, Paint, or any package capable of interacting with graphics and the Windows clipboard. The View option from the task bar allows the user to set the toolbar state. The advanced toolbar provides additional capability beyond that listed above for the user to experiment with. Also from the View menu selection the user can set the aspect ratio for the plot. This will allow the user to see cross sections as true circles and not ovals. The arrow keys can also be used to rotate the model. Control plus the arrow keys will pan the geometry. Hitting the key will reset the transform to its original position. The space bar will start the autorotate, and page up/page down, +/-, keys zoom the model.

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Chapter 2 – Section 5 How NozzlePRO Starts the DirectX viewer This section was written for NozzlePRO user’s having problems with the DirectX viewer. The first thing the user experiencing problems should do is to make sure that an acceptable version of DirectX is loaded on the machine. On 2000 and XP machines the directX options are accessible through the control panel:

When double-clicking on the DirectX icon the following should appear.

To run FE/Pipe or NozzlePRO version 7.0A or later should appear here. The software will not run with earlier versions, and this unfortunately excludes Windows NT users. Once it has been verified that a proper directX version is loaded, the user must be sure that the Mime file type is pointing to the proper version of ViewFE.EXE. ViewFE.EXE is the program in FE/Pipe and NozzlePRO that supports DirectX and the 3d model views. The file type assignment can get fouled up if earlier versions were not properly uninstalled, or if operating system or network problems have been encountered on the machine that has produced errant registry entries regarding FE/Pipe and/or NozzlePRO. The file type assignment can be checked by double clicking folder options in the control panel:

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In the folder options dialog box click on “File Types” and a view something like the above should appear. The file type of interest for NozzlePRO is “fea.” In the Registered File Types window scroll down to the FEA file type and then click on “Advanced.” If the FEA file type is not registered, then NozzlePRO was not properly installed, or the user does not have sufficient privledges. In either of these cases the user should open a command prompt and then enter the command “viewfe –r” to register the viewer. Be sure to enter this command from the subdirectory that contains the version of VIEWFE.exe that is the most current and that will be used.

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Once the fea file type is properly registered, the following file type should appear.

Clicking on the advanced button shows:

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Clicking on Edit shows:

The user should be sure that the application used to perform the action is the current version of viewfe.exe. The majority of the time that the viewer will not work, the fea file type is not properly associated. Once the proper application is established, the user can check that the file type is properly assigned. Do this by finding an fea file type on the system from a previous NozzlePRO run. Double clicking on this file should bring up the model in 3d. If this doesn’t work, the user should attempt to run a simple job using NozzlePRO to test if the 3d button s produce the intended result. Make sure the job entered is a simple one that the user knows will run successfully. The only other usual reason the viewer data files will not display is if the run has not completed successfully or if there are problems with Internet Explorer. Users are encouraged to run the latest versions of IE. Interim versions have various bugs on different operating systems that are fixed in the later versions. The nozzlePRO output is written in an htm file format. In the \output folder the user should find the file NOZZLE-PICS.HTM or SETUP1-PICS.HTM. Either of these files can be started by directing the browser to the output folder. As can be seen below the buttons in the nozzlePRO plot frame use the OnClick=”window.navigate( command. This ability should not be disabled in the user’s browser. An example section from a typical nozzlePRO htm file is shown below:

Copyright (c) 2007 by Paulin Research Group

2.5.4

NozzlePRO

www.paulin.com

Chapter 2 – Section 6 Errors – Aborted Runs – and DirectX Troubleshooting Running most finite element models requires the solution of very large sets of simultaneous equations. The sets of equations solved in most pipe stress programs are on the order of 100-to-10,000 equations of relatively small active column sizes. The sets involved in most finite element calculations are easily an order of magnitude larger, resulting in a squared increase in solution time and computer resource requirements. Accordingly, the user should not start a finite element calculation on anything slower than a 300 MHz. Pentium processor with at least 128 Mb of RAM, and at least 300Mb free on the hard disk. Larger and faster machines are preferable. The finite element program runs as a background application. The user will not see it on the task bar when running. The only way to “see” FE/Pipe running in the background is by bringing up the task manager under Windows NT/2000 or by hitting under Windows95 or Windows98. When looking at the displayed processes (programs) the user might see either: modgen fepre premini If any of these programs are running in the process list then the FEA program is running. All program errors should be trapped and reported. On a slower machine, (depending on the problem geometry), the solution might take upwards of 20-to-30 minutes to solve. On 500+ MHz Pentiums solutions should take only a few minutes. During solution a file: __file__.loc is maintained in the job run directory and CPU usage should be at about 80%. If there is no graphics in the output window when the job completes then most likely an error occurred and the user should find it described in the tabulated reports. There are several files that might give the user some guidance during an abnormal termination, and they are: error.log – Written if an abort occurred in the logic part of the preprocessing phase. modgen.err – Written for every job, but may contain a description of any errors that occurred during model geometry construction. input.add – If this file exists then it should contain a description of the model geometry. When a job does not complete successfully the user is encouraged to review this file thoroughly for potentially errant input. If errors in the input are found, the user should correct them and rerun the model. In any event, when a particular job aborts, the input .nozzlepro file should be forwarded to [email protected] for review. __file__.loc – Written during execution of the finite element portion of the run. This file contains the percentage of the current phase that is completed and the name of the current phase of the execution. Troubleshooting the Installation: If the software loads correctly and seems to run but does not produce the output data panes then most likely: a) Internet Explorer 5.0 or later is not correctly loaded on the machine, or b) The user has run out of hard disk space, or c) A geometry error has occurred. If the NOZZLE-FRAME.HTM does not exist in the...\\OUTPUT subdirectory then the job aborted or is still running. Jobs will abort if there are insufficient resources to solve the finite element problem. If you get the message that your executable has been invalidated then you will need to contact the Paulin Research Group for a more recent version of the program. If you get an error attempting to load the help, then either your version of WordPad or Word is out-of-date and needs to be updated. If you have an acrobat reader, the help documentation is also provided in a pdf file format.

Copyright (c) 2007 by Paulin Research Group

2.6.1

NozzlePRO

www.paulin.com

If the program aborts whenever you try to run then you should make sure that you have the rights to create folders and files in the current working directory. If you are unsure of the current working directory use the “Files” button to show you what Nozzle PRO thinks is the current working directory. If NozzlePRO will not install, then make sure that you have read AND WRITE access to the windows subdirectory. (This access is required by the MS program installer.) If the program always starts in DEMO mode after you have authorized it, then make sure your shortcut is pointing to the program STARTNP.EXE. Troubleshooting the 3d model viewer The NozzlePRO 3d models require that Microsoft DirectX 7.0A or later be installed on the machine. Microsoft describes DirectX as follows: “What is DirectX? Windows 2000 supports DirectX 7.0, which enhances the multimedia capabilities of your computer. DirectX includes accelerated video card and sound card drivers that provide better playback for different types of multimedia, such as full-color graphics, video, 3-D animation, immersive music, and theater sound. DirectX enables these advanced functions without requiring you to identify the hardware components in your computer and ensures that most software runs on most hardware systems.” Microsoft also suggests how to Troubleshoot DirectX as follows: Troubleshooting DirectX You can diagnose and resolve DirectX problems using the DirectX Diagnostic Tool and the Multimedia and Games Troubleshooter. The DirectX Diagnostic Tool helps you test the functionality of DirectX, to diagnose problems, and to configure your system to optimize DirectX performance. The DirectX Diagnostic Tool (Dxdiag.exe) is installed with DirectX. For information about using the DirectX Diagnostic Tool, click the Help button in the DirectX Diagnostic Tool. The Dxdiag.exe screen is shown below:

Click on the display tab (there may be several display tabs – check them all), and then execute the DirectDraw and Direct3d tests. If dxdiag.exe cannot be located on the computer, then on the computer does not have directx Copyright (c) 2007 by Paulin Research Group

2.6.2

NozzlePRO

www.paulin.com

installed. DirectX can be downloaded from the Microsoft website for Windows 98 or 95 operating systems. (Microsoft never provided DirectX 7.0 or later versions for NT.) The 3d viewer File:Options dialog box appears below:

When the program is installed it will try to use DirectX8. If DirectX8 is not installed it will shift to DirectX7 automatically and ask you to restart the program. If you don’t have DirectX7 or 8 loaded then you cannot use the 3d viewer. Several other items should be checked if there is 3d viewer abnormal behavior: 1) Make sure that you have the latest drivers for your video card. 2) Make sure that you have any patches for DirectX. 3) If you have DirectX7 – try loading DirectX8. 4) If you have DirectX8 – then try switching to DirectX7 in the dialog box above. (8 supports 7). 5) Try disabling hardware acceleration in the dialog box above. 6) If none of these help, then odds are that trying the same on another, different machine WILL work. DirectX technologies attempt to get the most out of the video performance on the machine. Older versions of BIOSs, drivers or chip sets may produce erratic behavior. Usually moving to another machine will solve the problem. Some machines use hardware that is too new, and has not been adequately tested with DirectX. Some older machines have the same problem. This will be an ongoing nuisance as hardware and software changes continue at such a rapid pace. Two types of 3d geometry files are created by NozzlePRO, and each is stored in the \\OUTPUT subdirectory on job completion. The NOZZLE”n”.FEX file contains shaded images of the model for each load case analyzed. NOZZLE”n”.FEA files contain stress results for the different stress types for the different load cases, e.g. (NOZZLE1.FEX and NOZZLE3.FEA.) These files are registered file types with the operating system and are associated with the program VIEWFE.EXE. When the user clicks on a 3d button, or double clicks on the file directly, the 3d viewer should start and display the corresponding image. These file types are registered with the operating system during each program startup. If there is an error the user will be notified at that time. The file type registration can be checked by double clicking on “My Computer:... Folder Options ... File Types” The user may have to hunt for the “Folder Options” button in the My Computer menu as it appears in different places depending on the operating system. When the “File Types” button is clicked, the user should scroll down the file_types window that appears until the Finite Element Analysis and Finite Element Mesh files are found. This display on a Windows 2000 Operating system is shown below, (it is different on a machine with another operating system.)

Copyright (c) 2007 by Paulin Research Group

2.6.3

NozzlePRO

www.paulin.com

Search for the “Edit File Type” button, (again, could be in a variety of places depending on OS), Click on “Edit” or otherwise check the location of the application used to perform the “open” action. An example of this screen is shown below:

The application path and name should be the current version of the viewer. If not, then it should be changed.

Copyright (c) 2007 by Paulin Research Group

2.6.4

NozzlePRO

www.paulin.com

Chapter 2 – Section 7 FE/PIPE, NozzlePRO, PVElite, and CodeCalc Using the FE/Pipe Input Editor: In the Options form (shown below), click on “Use FE/Pipe Editor During Run.” When this checkbox is marked the FE/Pipe data editor will be displayed prior to any plot or run. The user familiar with FE/Pipe can then make any changes needed to the input and continue on in the normal run sequence with NozzlePRO. This option is used most often under the direction of a support engineer to tweak an otherwise unwieldy model. FE/Pipe users often find generating models in NozzlePRO (especially structural models), convenient, and so use this feature to build their FE/Pipe input file. The FE/Pipe Editor can also be used to view certain geometry errors that are not trapped by NozzlePRO. The user can enter the FE editor and then “plot” the model from the editor data screen. In some cases error messages will be seen here that were not reported otherwise. The user can also check all three of the boxes shown below on the Optional data form. The FE/Pipe editor can then be used to edit and run the model data. The FE/Pipe input file will be saved and the user can continue running the modified data. User’s should only beware that changes made in the NozzlePRO forms will not take effect when running in this mode.

The recommended procedure for running in this mode follows: 1) Check the Use FE/Pipe Editor During Run and Leave FE/Pipe Data Files boxes. (See above.) 2) Make sure all NozzlePRO input is as close as possible to the desired model. 3) Click Run FE. 4) When the FE/Pipe editor appears make the necessary changes to the model. 5) Select the option SUBMIT for Analysis to exit the FE/Pipe data editor. The run should continue through to completion if an editing error was not made. 6) The standard NozzlePRO results will appear. 7) To prepare for a second run check the box “Use Existing FE/Pipe Input File” on the Options data form. 8) Click Run FE. You will now be put back into the FE/Pipe data editor with the old input. This can now be modified for a second run. Using a NozzlePRO ifu file in FE/Pipe: FE/Pipe input from NozzlePRO for 3d shell elements is stored in the file NOZZLE.IFU. This file is found after a run has completed in the \\OUTPUT subdirectory. This file may be read into FE/Pipe and used normally if the latest version of FE/Pipe is installed on the computer. The FE/Pipe input from NozzlePRO for axisymetric 2d and brick models is stored in the file SETUP.IFU also in the \\OUTPUT subdirectory. To use NozzlePRO with PVElite and CodeCalc several things must happen: 1) You must have a licensed and validated copy of the program. (You should receive a site key and be able to run NozzlePRO outside of PV Elite or CodeCalc as described in this manual.) 2) You must tell PVElite or CodeCalc where NozzlePRO is loaded. Enter PVElite input menu, choose component analysis module, that will launch CodeCalc, then under the CodeCalc tools menu, select configuration, then choose miscellaneous app, and there set the path to the folder where nozzlePRO is installed. This will store the path for all future runs and will only have to be done once.

Copyright (c) 2007 by Paulin Research Group

2.7.1

NozzlePRO

www.paulin.com

Chapter 3 – Section 1 Output Review for 3d Shell Models The general browser output screen appears below:

When first reviewing output always scroll through the plots to be sure that the graphical results “look reasonable.” Several examples are given later of results that do not “make sense,” and should be discarded. The buttons: can appear in any combination and indicate that 3d rendered images of the geometry or stress state are available. The 3d rendered images may be interactively rotated, panned and zoomed. Additionally a thermometer (which appears in the toolbar) can be used to read off the exact value of the stress at any point in the geometry. The 3d rendered images provide the best way to inspect the calculated stress state. These plots should be inspected at least once for each run to be sure the results “make sense.” Distorted shapes are highly exaggerated but may be scaled using the scale text box and the set scale button. The available Output Reports are listed and described below: Model Notes – Echoes the model input and gives guidance FE/Pipe Load Case Report – Describes which load cases were setup and run to satisfy Code requirements. ASME Overstressed Areas – Any areas in the model that show to be overstressed are summarized here. Highest Primary Stress Ratios – ASME Section VIII Div.2 primary stresses and allowables. (sustained) Highest Shakedown Stress Ratios – Secondary (non-peak) stresses and allowables. Highest Fatigue Stress Ratios – Expansion/peak stresses and allowables. Copyright (c) 2007 by Paulin Research Group

3.1.11

NozzlePRO

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Computed Stress Intensification Factors – SIF’s for use in pipe stress programs. Allowable Loads – Allowable operating, expansion and sustained loads. Flexibilities – Point stiffnesses that would be put back in a beam-type pipe stress program. FE/Pipe Load Case Report Example: A brief explanation of why the load case was set up is included before each load case. Referenced Code sections are included. FE/PIPE Load Case Report Inner and outer element temperatures are the same throughout the model. No thermal ratcheting calculations will be performed. THE 1

7

LOAD CASES ANALYZED ARE:

Sustained Sustained case run to satisfy Pl 0.67Sy and Pm 72% of the allowable. (In the design case.) Calculated values for Pl or Qb are broad in extent. (See Figure 1 above.) Larger D/T openings and larger d/D openings. (D/T>80, and d/D>0.7) Weak blink flanges are suspected of being an accomplice, but no immediate test data is available.

The above does not imply that there will always be problems in these situations, but these are the general cases where hydrotest problems such as bursting or distortion have been observed. Full versions of FE/Pipe can read in the NozzlePRO input files and perform a simplified plastic analysis if necessary to assure that highly stressed areas are indeed local in nature, i.e. local plasticity redistributes loads to low stress regions.

Copyright (c) 2007 by Paulin Research Group

3.3.2

NozzlePRO

www.paulin.com

Chapter 3 – Section 4 Stress Intensification Factors and Flexibilities A typical Stress Intensification Factor Report is given below: Computed Stress Intensification Factors Branch/Nozzle Sif Summary

Axial : Inplane : Outplane: Torsion : Pressure:

Peak 1.213 1.548 2.605 0.916 6.494

Primary 1.162 1.451 2.451 1.102 6.068

Secondary 1.798 1.812 2.896 1.357 9.250

The above stress intensification factors are to be used in a beam-type analysis of the piping system. Inplane, Outplane and Torsional sif's should be used with the matching branch pipe whose diameter and thickness is given below. The axial sif should be used to intensify the axial stress in the branch pipe calculated by F/A. The pressure sif should be used to intensify the nominal pressure stress in the PARENT or HEADER, calculated from PD/2t. Pipe OD : Pipe Thk: Z approx: Z exact :

24.000 8.000 1608.494 1340.412

B31.3 Peak Stress Sif ....

B31.1 Peak Stress Sif ....

WRC 330 Peak Stress Sif ....

in. in. cu.in. cu.in.

0.000 1.054 1.138 1.000

Axial Inplane Outplane Torsional

0.000 1.000 1.000 1.000

Axial Inplane Outplane Torsional

0.000 1.000 1.500 1.000

Axial Inplane Outplane Torsional

Notes: 1) For input into most pipe stress programs only the Inplane and Outplane Peak stress intensification factor can be used. (Markl testing done in the 50’s concentrated on only these loading directions.) Axial and pressure stress intensification factors are given for reference, and for the case where any of these loads cycle in a critical situation and the actual magnitude of the resulting stress should be estimated. (Most piping program users will have to make that evaluation by hand.) 2) Stress intensification factors (SIF’s) are paired with a section modulus! The piping program user should apply the SIF’s at the cross section whose OD and thickness match those given in the SIF reports above. 3) The values printed under the headings: B31.3, B31.1 and WRC 330 are given for reference. (WRC 330 was released as WRC 329.) 4) In cases where the nozzle thickness is significantly greater than the header or vessel thickness SIF’s can become quite large, often in excess of 20. Many piping engineers are not used to seeing SIF’s of this magnitude. The reason for this is that most piping programs print only the Code calculated “i” factor when generating reports, but then adjust it (according to the effective section modulus rules in the piping code) before making the stress calculation by the ratio of t/T, where “t” is the thickness of the branch and “T” is the thickness of the header. Clearly, where t >> T, the multiplication of “i” by t/T produces a significantly larger value for the actual stress intensification factor. The stress intensification factors given in the finite element reports shown above are already multiplied by t/T where applicable. Copyright (c) 2007 by Paulin Research Group

3.4.1

NozzlePRO

www.paulin.com

5) When the calculated SIF, or “i” factor, is less than 1.0, the value of 1.0 should be used. In general, this means that the component is stronger in fatigue than a girth butt weld – but since the actual locations of girth butt welds are not specified in most fossil-petrochemical type pipe stress programs the Code user is penalized by being required to treat every pipe section as if it were a girth butt weld. 6) The approximate section modulus calculation given above is found from the expression (3.14)(r2)(t), where r is the mean radius of the pipe and t is the thickness. Stress Intensification Factors are generated typically for a vessel or large pipe connection and provided to a pipe stress engineer for use in a piping program. Pipe stress engineers are generally interested in these values since the B31.3 Code has published restrictive guidelines for use of the standard Code Stress Intensification Factors, eg:: “B31.3 Table D300 Note (1) Stress intensification and flexibility factor data .. are for use in the absence of more directly applicable data … their validity has been demonstrated for D/T 0.5 t/T < 1.0 Pad reinforced nozzles Hillsides or laterals Area replacement rules for pressure are barely satisfied and large D/T. Temperatures are approaching the creep regime. Cycles are greater than 5000. Design and operating conditions are approximately the same. The load consists of high-pressure stresses and high loads. The Piping attached to the nozzle is long, flexible, and somewhat unrestrained.

Copyright (c) 2007 by Paulin Research Group

6.1.1

NozzlePRO

www.paulin.com

Chapter 6 – Section 2 Engineering Considerations High Temperature – These are temperatures in the creep range for the material – usually in the 700 –to- 850 deg. F range and higher. ASME Section VIII Division 2 does not directly address creep range applications, and so actual calculations have been left to the interpretation of the user. It is suggested that users in these high temperature regimes enter ASME Section VIII Division 1 allowables. (Division 2 does not give allowables for these temperatures.) Nuclear Code Case N253 can also be used to compute a high temperature fatigue limit for Pl+Pb+Q+F stresses. What the Code Inspector Sees – Since the use of finite elements as a regular design tool is fairly new, Code inspectors vary in what they expect to see with regards to an analysis. In general, a cover letter followed by the listed tabular reports and color prints of the plotted results has been enough to satisfy most Code inspectors. The cover letter usually states that the included reports have been reviewed by a registered professional engineer and were found to satisfy the necessary Code section requirements for stress. In general, an inspector wants to be able to look at the input listing and see the correct allowable stresses, diameters, wall thicknesses and pressures. It is expected that some guidelines will be published in the near future that give the inspector additional guidance, and that give the user more freedom in pursuing less conservative designs. External Pressure – Where external loads and external pressure act simultaneously on a large or thin-walled opening, elastic instability may be of concern. The standardly applied ASME Section VIII Division 2 Code rules do not explicitly address elastic instability. There are nonlinear approaches available within the full version of FE/Pipe to deal with this problem should it arise. FE/Pipe can be started with the NOZZLE.IFU file described above, and an elastic instability (elastic buckling) calculation performed on the geometry to be sure that buckling load factors exceed the Codes intended buckling safety factor of 3. Elastic instability load factors for pressure vessel and piping geometries usually exceed 10. When the calculated load factors are in the 4-to-5 range extra care is warranted because non-simulated events such as wind gusts, frictional sliding transients, etc. can induce momentary overloads that result in the initiation of catastrophic buckling. Orthotropic Materials – The orthotropic material model has not been installed in NozzlePRO but is available in the full version of FE/Pipe. Pressure Stiffened Shells - Basketball, football and soccer players are familiar with the significant stiffening effects of even relatively low pressures on thin, membranes. This effect is also seen in the pressure stiffening of shell membranes used in piping and vessel systems. The effect tends to be more pronounced in plastic systems, but Rodabaugh suggests that “design pressures might reduce the flexibility by about a factor of 3 for out-of-plane moment and thrust loads and by about half that much (1.2 to 1.5) for in-plane moments.) The effect of pressure stiffening is a nonlinear effect included in the full version of FE/Pipe, but not available in NozzlePRO. Factors of Safety – Whereas the ASME Code rules are based on experience and tested results, the intention is to provide a consistent factor of safety for the varieties of different vessel and piping systems designed. In general, the factor of safety against fatigue cracking is two on stress. This means that in a perfect world, if the Pl+Pb+Q+F stress is equal to the allowable the component would fail at the end of its design cycle life at “twice” that stress level. The factor of safety against gross collapse or distortion is about 4 or greater. This means that in a perfect world, if the Pl stress is equal to the allowable the component would suffer a pressure boundary failure (burst), at somewhere between 4 –to- 8 times the load that caused that stress. Flanged Ends – For larger d/D and d/t ratios it is known that the l/d ratio and the rigid end stiffnesses can affect pressure stresses in the junction (l is the length of the branch). The 3D shell cylinder-to-cylinder models used in NozzlePRO attempt to put what is essentially an infinitely long pipe on the end of the cylinder-to-cylinder branch connection by default. Flanges are almost always stiffer than pipe, however, bolt loads and rotations of blinds can result in greater stresses at the shell intersection. Detrimental effects due to this condition may result in noticeable plastic deformation during hydrotest or in a leaking joint. Blind and matching flanged end nozzles are provided in the axisymmetric 2D and brick model options. The user is encouraged to investigate this effect further using these tools.

Copyright (c) 2007 by Paulin Research Group

6.2.1

NozzlePRO

www.paulin.com

Chapter 6 – Section 3 Finite Element Philosophies, Element Types, Etc. Standard Element Type – The basic element used in NozzlePRO is the eight-noded reduced integration curved shell element. While more difficult to formulate and solve using active column techniques, and subject to several inconsistent deformation modes, the element nevertheless has been found to be remarkably insensitive to shape and less sensitive to size than many of the more “formally” derived element types. Stiffness convergence is good even with the crudest mesh and non-averaged stress calculations give a good visual indication of the adequacy of the stress state. The element is basically the same curved shell element used in the Ansys program as STIF93. The formulation can be found in many finite element texts, one being:“Concepts and Applications of Finite Element Analysis,” by Cook, Malkus, and Plesha, 3rd ed., John Wiley & Sons. Special formulations are provided for transferring six degree-of-freedom piping-type forces and moments into shell models to prevent inadvertent local transfer of torsional moments into the shell. Adjustments are also made to the element Jacobian if needed to properly condition poorly shaped elements.

Stress Concentration Factors – Default stress concentration factors are used at as-welded joint locations for peak stress evaluations to bring the calculated shell stresses inline with observed fatigue test results. This approach has been used for over nine years at PRG in Houston. The only stress classification affected by the stress concentration is Pl+Pb+Q+F. The membrane stress Pl, and the secondary stress Pl+Pb+Q+F is the stress intensity calculated directly by the shell finite element procedure evaluated using the ASME Section VIII Division 2 tensor combination directions.

High temperature considerations, pressure stiffening, orthotropic materials, and elastic instability (buckling) are discussed under the topic “Other Engineering Considerations.”

Mesh Density – While every effort has been made to produce dependable meshes and gradients based on the variety of geometries there will be some configurations that will not be adequately meshed. It remains to the user to review the displayed stress patterns and to determine if these errant conditions exist, but in the majority of cases, “if the stress distribution looks reasonable,” the values are correct. New algorithms are being designed that will further improve the mesh quality and that should produce dependable solutions in a wider variety of situations. Extreme geometries will tend to produce the more difficult meshes. For example, a straight nozzle in the center of an elliptical head will be meshed correctly every time, whereas a pad reinforced nozzle on the knuckle of a dished head may have greater difficulties. The program will at times adjust pad and/or nozzle dimensions and locations to improve the quality of a mesh at the expense of model geometric accuracy. In these cases messages are printed in the Input Data report that should be reviewed. If the user is ever concerned that an adjustment made by the modeler produces a significant change in the solution results he is encouraged to vary the parameter himself in subsequent runs to assure himself that any changes or assumptions made by the program are inconsequential to the overall high stress behavior.

Element Sizes at Discontinuities – Element sizes near discontinuities of importance are influenced both by major geometric dimensions, the square root of RT, the anticipated stress decay, and by experience in running multiple similar geometries. Should the user think that mesh refinement or mesh “alteration” is essential for a particular problem the analyst may follow the “How to Get Help” procedure and submit the geometry for developer review. (See the section: “How to Get Help.”)

Shell Models vs 3D Models – Axisymmetric 2d and brick models of head and skirt geometries were added in Version 4.0 of NozzlePRO. The axisymmetric quad element is eight-noded, including four midside nodes along with the four corner nodes. The brick element used is the eight-noded brick element with extra shape functions to permit bending modes. Stress tensor components are extrapolated from the gauss points to the node points for plotting and tabular results. The axisymmetric 2d and brick elements were added primarily to: Copyright (c) 2007 by Paulin Research Group

6.3.1

NozzlePRO

www.paulin.com

1) Allow users to verify shell models of the same geometry. 2) Permit a more accurate analysis of thick-walled intersections 3) Analyze geometries not directly amenable to shell solutions, such as non-integral repads and overturning moments on skirts. 4) More accurately calculated cyclic pressure stresses in thick-walled geometries. 5) Address basic steady state and transient heat transfer and stress problems. The user is strongly encouraged to compare the results from different model types. A center nozzle in a head subject to pressure only loads can be changed from a shell model to an axisymmetric 2d model by a single mouse click. Comparing these results can be quite informative.

Copyright (c) 2007 by Paulin Research Group

6.3.2