Nozzle Pro

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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:

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

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Chapter 1 – Section 1

1- Axisymmetric Horizontal Vessel Modeling with Saddles 2- Axial Load Evaluation for Horizontal Vessels

3- Gravity Multipliers for X, Y, & Z Directions for Modeling Vessel Loads 4- 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.

5- Pipe Shoe Modeler

6- Integral & Non-Integral Wear Plates for Saddles and Pipe Shoes 7- Tapered Saddles and Pipe Shoes

8- SYMFIX Boundary Conditions for Midspan Ovalizing in Horizontal Vessels 9- Upgraded DirectX 3D Dynamic Displacement and Static Model Viewer 10- Nozzles through Blind Flanges in Axisymmetric and Brick Models 11- Double Bed Support Axisymmetric and Brick Models

12- Axisymetric 2d and Brick Axisymetric Models

13- Steady State and Transient Heat Transfer for Axisymetric 2d Elements 14- Blind or Matching Flange End Conditions for Axisymetric 2d or Brick Models 15- Radius’d Welds in Axisymetric 2d and Brick Models

16- Overturning Moments on Skirts (Brick Models) 17- DirectX 3d Dynamic Displacements

18- Internal Ring Loads in Axisymetric 2d or Brick Models 19- Help Buttons Throughout

20- Discontinuity Stress Reporting

21- Integral and non-Integral Repads for Axisymetric 2d or Brick Models 22- Head Thickness Contours for Bricks and Axisymetric 2d models 23- 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

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Top Head Blind & Pad Bottom Head Skirt Brick Flanges & Skirt Top Head Load Flanges

Pipe Shoe Triple-Plate Support Head Structural 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.

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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 Difference with FEA

Cylindrical Junction (WRC 107) FEA Stress 270% Higher than WRC 107 NonLoaded Small Branch Takeoff FEA Stress 500% Lower than B31.3 Nozzle Loads Due To FEA Flexibilities FEA Loads 630% Lower than Rigid Analysis

SIF’s for Nozzles in Heads FEA Stress 7.7 Times Higher than Piping Program Default

Straight vs. Lateral 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 Small d/D WRC 107 Comparison FEA different from WRC 107 by 3.7%

Pad Reinforced Attachment 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: 21,490.psi. WRC 107 Stress at Pad Edge: 18,214.psi.

FEA Maximum Stress (PL+PB+Q out) with 1.75x mesh 65,887 psi.

(307% of WRC 107)

(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: Se = (io)(Mo)/Z = (6.1)(1.1E6)/(120.3) = 55,777 psi Nozzle/PRO: 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.

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Straight Through

Lateral (45) Hillside B31.3 InPlane Max Allowed Moment _{583,179 in.lb.} _{786,243 in.lb.} _{451,108 in.lb.} _{495,658 in.lb.}1 Outplane Max Allowed Moment 171,867 in.lb. 304,402 in.lb. 191,997 in.lb. 385,698 in.lb.

Maximum Allowed Pressure _{348 psi} _{160 psi} _{326 psi} _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 107 126,677

FEA tn=0.5” 150,765

FEA tn=0.9” 144,522

FEA tn=1.5” 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 Line Load(3) FEA

Lug Edge(1) Pad Edge(2) Lug Edge(1) Pad Edge(2) Lug Edge(1) Pad Edge(2)

6x8 Rectangle No Pad 141,818 n/a 111,139 n/a 129,813 n/a

6x8 Rectangle 1” Wide Pad 43,215 90,929 39,462 67,989 71,197 70,604

6x8 Tri Plate Supt. 6” Wide Pad 43,215 22,619 158,145 15,619 42,311 24,358

6x8 Inverted Tee 6” Wide Pad 43,215 22,619 299,006 15,619 75,275 24,631 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.

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Box (6” Pad) (41,299) 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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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/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.

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)

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Step 3 of 6

Select a “Base Shell Type” and input “Vessel” Dimensions

Step 3 of 6

For this example select “Cylinder” and input the vessel OD and wall thickness 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.

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Step 5 o f 6

Input Loads

Step 5 o f 6

Input Loads

Click the “Loads” button and the following screen should appear. Click the “Loads” button and the following screen should appear. Input the loads and use “locally” defined loads (convert to ft lb )

Input the loads and use “locally” defined loads (convert to ft lb )

(Using local coordinates without direct shear loads permits the user to (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: 21,490.psi. WRC 107 Stress at Pad Edge: 18,214.psi.

(307% of WRC 107)

(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

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

Loads

Pressure: 10 psig Pressure: 10 psig

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

Step 2 of 6

For this example select “English” units For this example select “English” units

Step 3 of 6

In this example select “Cylinder” and input the vessel OD and wall thickness In this example select “Cylinder” and input the vessel OD and wall thickness

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Step 4 of 6

In this example select “Straight” and input the Nozzle dimensions. In this example select “Straight” and input the Nozzle dimensions.

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. 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

Peak Primary Secondary Axial : 1.991 2.004 2.949 Inplane : 1.846 1.801 2.735 Outplane: 0.503 0.974 1.007 Torsion : 3.146 4.539 4.660 Pressure: 0.000 0.000 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: Se = (io)(Mo)/Z = (6.1)(1.1E6)/(120.3) = 55,777 psi Nozzle/PRO: 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 Ze = (π)(rB2)(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) Hillside B31.3 InPlane Max Allowed Moment 583,179 in.lb. 786,243 in.lb. 451,108 in.lb. 495,658 in.lb.1

Outplane Max Allowed Moment 171,867 in.lb. 304,402 in.lb. 191,997 in.lb. 385,698 in.lb.

Maximum Allowed Pressure _{348 psi} _{160 psi} _{326 psi} _n/a

Note (1): For B31.1 the Inplane and outplane moments are the same.

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 Maximum Conservative Realistic Load Type (Range): Individual Simultaneous Simultaneous Occuring Occuring Occuring

Axial Force (lb. ) 43881. 11228. 16841.

Inplane Moment (in. lb.) 583179. 105101. 222953.

Outplane Moment (in. lb.) 171867. 30957. 65671.

Torsional Moment (in. lb.) 598463. 145044. 217566.

Pressure (psi ) 348.73 100.00 100.00 PRIMARY Maximum Conservative Realistic Load Type: Individual Simultaneous Simultaneous Occuring Occuring Occuring Axial Force (lb. ) 67023. 17594. 26391.

Inplane Moment (in. lb.) 514214. 72906. 154657.

Outplane Moment (in. lb.) 377181. 51998. 110303.

Torsional Moment (in. lb.) 334385. 66047. 99071. Pressure (psi ) 240.90 100.00 100.00

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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 Line Load(3) FEA

Lug Edge(1) Pad Edge(2) Lug Edge(1) Pad Edge(2) Lug Edge(1) Pad Edge(2)

6x8 Rectangle No Pad 141,818 n/a 111,139 n/a 129,813 n/a

6x8 Tri Plate Supt. 6” Wide Pad 43,215 22,619 158,145 15,619 42,311 24,358

6x8 Inverted Tee 6” Wide Pad 43,215 22,619 299,006 15,619 75,275 24,631 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 ID = 72”

T=0.625”

Loads:

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

Rectangular Attachments in 5 Steps

Step 1 of 6

Step 2 of 6

For this example select “English” units

Step 3 of 6

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Step 4 of 6

In this example select “Structure 6” and input the Structure dimensions. In this example select “Structure 6” and input the Structure dimensions.

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

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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: . The entered loads are automatically distributed evenly over the outer section of any cross section selected.

Box (no Pad) (129,813) Box (1” Pad) (71,197) Box (4” Pad) (46,775)

Box (6” Pad) (41,299) Triple-Plate (42,311) 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 Using “FE” SIF

ASME B31.1 For

(0.75ioB31)(tB)/(tB H)<1.0

[Mi2 + Mo2 + Mt2]0.5/( π RmB2 tBB) (ioFE)[Mi 2

+ Mo2 + Mt2]0.5/( π RmB2 tB) B

For

(0.75ioB31)(tB)/(tB H)>1.0

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

ASME B31.3

For (ii)(tB)/(tB _H) < 1.0 [Mi 2

+ Mo2 + Mt2]0.5/( π RmB2 tBB) [(ioFE Mo) 2

+(iiFE Mi)2+(Mt)2]0.5/(πRmB2tB) B

For (ii)(tB)/(tB H) > 1.0 [(io_B31 Mo) 2 +(iiB31 Mi) 2 +Mt2]0.5/(πRmB 2 tH) [(ioFE Mo) 2 +(iiFE Mi) 2 +(Mt)2]0.5/(πRmB 2 tB) 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/tB H).

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.

...Numerical Example: NPS 20 x 4 un-reinforced branch connection (std wt, all)

Shell Type: cylinder Nozzle/Attachment Type: Straight

Diameter 20 inches Diameter 4.5 inches

Wall thickness 0.375 inches Wall thickness 0.237 inches

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

Nozzle/PRO Branch SIFs:

Inplane Outplane Torsion Axial 4.04 7.42 1.43 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 Bending Stress lb./sq.in. Torsion Stress lb./sq.in. SIF In Plane SIF Out Plane Code Stress lb./sq.in. Allowable Stress lb./sq.in. Ratio % 20 24327.0 0.0 4.040 7.420 24327.0 50000.0 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/tB H) 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.

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:

Inplane Outplane FEA 4.04 7.42 “Adjusted” 6.39 11.74 Generating SIFs for loads applied through the header:

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Step 2 of 3:

Select “SIF’s and K’s for Cylinder Header”

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

Inplane Outplane FEA 1.58 0.37 (1) “Adjusted” 2.5 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.

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ELEMENT Bending Stress lb./sq.in.

Torsion Stress lb./sq.in.

SIF In Plane SIF Out Plane Code Stress lb./sq.in. Allowable Stress lb./sq.in. Ratio % 10 – 20 @ 20 289.5 0.0 1.600 1.000

_289.5

50000.0 0.6 20 – 30 @ 20 0.0 0.0 1.600 1.000 0.0 50000.0 0.0 20 – 40 @ 20 40506.8 0.0 4.040 7.420 40506.8 50000.0 81.0

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

ELEMENT Bending Stress lb./sq.in.

SIF In Plane SIF Out Plane Code Stress lb./sq.in. Allowable Stress lb./sq.in. Ratio % 10 – 20 @ 20 289.5 0.0 1.600 1.000 289.5 50000.0 0.6 20 – 30 @ 20 0.0 0.0 1.600 1.000 0.0 50000.0 0.0 20 – 40 @ 20 74396.0 0.0 4.040 7.420 74396.0 50000.0 148.8*

The correct result is only obtained by switching the SIFs from inplane to outplane: ELEMENT Bending Stress

lb./sq.in.

SIF In Plane SIF Out Plane Code Stress lb./sq.in. Allowable Stress lb./sq.in. Ratio % 10 – 20 @ 10 289.5 0.0 1.000 1.000 289.5 50000.0 0.6 10 – 20 @ 20 463.1 0.0 1.000 1.600 463.1 50000.0 0.9 20 – 30 @ 20 0.0 0.0 1.600 1.000 0.0 50000.0 0.0 20 – 40 @ 20 40506.8 0.0 7.420 4.040 40506.8 50000.0 81.0

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Chapter 1 – Section 5

How to Get Help

Help is available via email from [email protected]. Submit the file <name>.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.

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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:

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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:

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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 NozzlePRO input and output is self-explanatory. Where help is available on an input form a key is shown 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

<jobname>.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.

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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 <name>.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 \<name> 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 \<name>\OUTPUT subdirectory for storage.

(Everything in the \<name> 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 \<name> 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: C:\SmithConsulting\N102.nozzlepro Intermediate Data Files: C:\SmithConsulting\N102\*.*

FE/Pipe Input File: C:\SmithConsulting\N102\NOZZLE.IFU...put it here to use in NozzlePRO. FE/Pipe Input File: C:\SmithConsulting\N102\OUTPUT\NOZZLE.IFU ... found here when

job finishes Output Browser Files: C:\SmithConsulting\N102\OUTPUT\NOZZLE*.HTM

Output Static Plots C:\SmithConsulting\N102\OUTPUT\*.BMP Output 3d Models C:\SmithConsulting\N102\OUTPUT\*.fex

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Output 3d Results 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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Chapter 2 – Section 2

Common Load Types and Categories

Primary Loads

Primary 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.

b = (6)(MO)/(t2), or (6)(ML)/(t2)

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b = (6)(M)/(t2)

Figure 7 – Shell Bending Stress Examples 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)