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Kagira Drawing Solution®

The Pioneer in Quality Piping Education

ISO 9001:2008 Certified Training Institute

Pipeline Stress Analysing

Name
Student ID

Course

Batch

Date of Join

 Hard Work Never Fails 

Pipeline Stress Analysing-Caesar II

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 Syllabus

 Volume-I Introduction

 Volume-II Tools

 Volume-III Modeling

 Volume-IV Pipe Components

 Volume-V Supports

 Volume-VI Spring Hangers

 Volume-VII Nozzle & Loads

 Volume-VIII Stress Analysing

 Volume-IX Equipment Analysing

 Volume-X Underground Pipe (Buried)

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Volume-I Introduction

1. Introduction about Pipe Line Stress Analysing 1

Volume-II Tools
2. Menu Command 5
3. Input Menu 6
4. Analysing Menu 7
5. Output Menu 8
6. Tools Menu 8
7. Menu Commands 9
8. Edit Menu 10
9. Standard Operation 11
10. Model Menu 18

Volume-III Modeling
11. Piping Input 20
12. Node 21
13. Pipe Proprieties 22
14. Auxiliary Data 25

Volume-IV Component
15. Bend 27
16. Reducer 31
17. Tee 32
18. Valve & Flange 34
19. Expansion Joint 35

Volume-V Supports
20. Restrains 37
21. Anchor 38
22. Shoe Support 43
23. Guide 45
24. Stopper 48
25. Limit stop 49
26. Rotational Restrain With Gap 52
27. Skewed Double Acting Restrains 54
28. Restrain between two pipes 56
29. Dummy support 58
30. Allowable support spans 63
31. Support Thick Calculation 63

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Volume-VI Spring Hangers
32. Hangers 64
33. Variable Spring Hangers 65
34. Constant Spring Hangers 66
35. Hangers Selection 67

Volume-VII Nozzle & Loads

36. Flexible Nozzles 73
37. WRC 297 73
38. API 650 77
39. PD 5500 79
40. Force & Movement 81
41. Uniform Load 81
42. Wind Load 82
43. Wave Load 83

Volume-VIII Stress Analysing Report

44. Stress Category 85
45. Load Combinations 88
46. Load cases 91
47. Critical Line Analysing 96
48. Expansion Loop 106
49. Report Generation 109
50. Stress ISO Generation 111

Volume-IX Equipment & Components

51. Stress Intensification Factor 114
52. Bend Intensification Factor 117
53. WRC 107 119
54. Flange leakage Stress 129
55. Strength of Corroded Pipeline 136
56. Expansion Joint 140
57. NEMA SM23 145
58. API 610 150
59. API 617 154
60. API 661 156
61. Heat Exchange 159
62. API 560 161

Volume-X Buried
63. Buried Pipe Analysing 162
64. Exercise 166

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 About Kagira
Kagira drawing solution (KDS) basically a project division pioneer in power & process piping
planting, due to lack of man power in our piping engineering projects, we started hunting for
fresh graduates and provided an intensive in-house piping training and were able to maintain
the client requirements. As a reward to our hard work, excellence and innovation we received
offers from companies to train their employees in piping engineering course. As per clients
wish we lately incorporated a training division provided a massive training to the piping
aspirants and now mastering in it.

Once upon a time piping course is just a dream which is hard to attain due to lack of
training institutes and unaffordable price, now Kagira Drawing Solution imparts quality
training at affordable prices to make your dream come true. Our alumni were mastering in
piping engineer, piping designer and piping stress analysing across the globe. We at KDS will
be providing individual system and study materials, the trainers will concentrate on every
individual to test their level of knowledge and understanding on every chapter and retrain
them accordingly. Depending on your knowledge and skill you would get an opportunity to
work with our live piping projects.

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Volume I Introduction

Volume- I Introduction
What is CAESAR?

CAESAR (Computer Aided Engineering Stress Analysing Reporter) is a PC-based pipe stress analysis
software program developed, marketed and sold by COADE Engineering Software. This software
package is an engineering tool used in the mechanical design and analysis of piping systems. The
CAESAR user creates a model of the piping system using simple beam elements and defines the loading
conditions imposed on the system. With this input, CAESAR produces results in the form of
displacements, loads, and stresses throughout the system. Additionally, CAESAR compares these
results to limits specified by recognized codes and standards. The popularity of CAESAR is a reflection
of COADE’s expertise in programming and engineering, as well as COADE’s dedication to service and
quality.

What are the Applications of CAESAR?

CAESAR is most often used for the mechanical design of new piping systems. Hot piping
systems present a unique problem to the mechanical engineer—these irregular structures experience
great thermal strain that must be absorbed by the piping, supports, and attached equipment. These
“structures” must be stiff enough to support their own weight and also flexible enough to accept
thermal growth. These loads, displacements, and stresses can be estimated through analysis of the
piping model in CAESAR. To aid in this design by analysis, CAESAR incorporates many of the
limitations placed on these systems and their attached equipment. These limits are typically specified
by engineering bodies (such as the ASME B31 committees, ASME Section VIII, and the Welding
Research Council) or by manufacturers of piping-related equipment (API, NEMA, or EJMA). CAESAR is
not limited to thermal analysis of piping systems. CAESAR also has the capability of modeling and
analyzing the full range of static and dynamic loads, which may be imposed on the system. Therefore,
CAESAR is not only a tool for new design but it is also valuable in troubleshooting or redesigning
existing systems. Here, one can determine the cause of failure or evaluate the severity of unanticipated
operating conditions such as fluid/piping interaction or mechanical vibration caused by rotating
equipment.

Basic Operation
Once you have started the program and opened the file, you will choose the required
operation.

Piping Input Generation

Once the desired job name has been specified, users can launch the interactive model builder
by selecting the Input-Piping entry of the Main Menu. The input generation of the model consists of
describing the piping elements, as well as any external influences (boundary conditions or loads)
acting on those elements. Each pipe element is identified by two node numbers, and requires the
specification of geometric, cross sectional, and material data. The preferred method of data entry is the
piping spreadsheet.

WHAT IS STRESS ANALYSIS?

Piping Stress analysis is a term applied to calculations, which address the static and dynamic
loading resulting from the effects of gravity, temperature changes, internal and external pressures,
changes in fluid flow rate and seismic activity. Codes and standards establish the minimum
requirements of stress analysis.
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Volume I Introduction

PURPOSE OF PIPING STRESS ANALYSIS

 Safety of piping and piping components

 Safety of connected equipment
ipment and supporting structure
 Piping deflections are within the limits

Temperature Effects and Stress

ess Due to Temperature Change
As we know, for any material changes in temperature result in volume change. An increase or
decrease in temperature results in the expansion or contraction of a structure. To better understand
this phenomenon, consider a steel wire with a length, , fixed at one end and free on the other end, is
subjected to a temperature rise of . The wire will elongate by , as shown below:

Change in the Wire Length Due to Increase in Temperature

The increase in the length, , is related to the changes in temperature by the following equation:
(1)

In this equation, represents changes in temperature in degrees Fahrenheit ( ), l is the

original length, and is the coefficient of thermal expansion (or thermal coefficient) with the units of

depends on the material type. The following shows the values of for a few commonly used
building materials:
Material
Aluminum 0.00128
Stainless Steel 0.00099
Copper 0.00093
Mild Steel 0.00065
Concrete 0.00055
Masonry 0.00035
Wood 0.00030

As can be seen from the above table, aluminum has larger value than steel. This means that,
subjected to the same temperature variations, aluminum structures undergo larger changes in volume
than similar steel structures. If the structure is prevented from movements (restrained) while
subjected to a temperature change, stresses will develop.

Consider the same piece of wire used before with both ends restrained undergoing a
temperature rise of . Since both ends of the wire are prevented from movement, stresses develop
in the wire, forcing it to buckle. Page | 2
Volume I Introduction

Buckling of Restrained Wire Due to IIncrease in Temperature

To find how much these stresses are and what parameters they depend on, we first consider
the wire without one of the end supports subjected to a temperature increase of . The wire
extends by , and the wire’s length becomes .

Change in the Wire Length Due to Increase in Temperature

Now, we push the right end of the wire to go back to its original length. This is the force that
would have developed in the wire if both ends were restrained when the temperature was raised.

Force
rce in the Wire Due to Change in Temperature

As we know, the stress, , in the wire due to the force, , is:

(2)

where is the cross-sectional

sectional area of the wire.
We also remember that the
he modulus of elasticity, , is defined as:

(3)

Where is the strain, defined as:

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Volume I Introduction

(4)

Substituting equation (4) into

to (3):

(5)

Substituting equation (1) into (5):

(6)
or

(7)

The above equation shows the relationship between the changes in temperature and the stress
developed in the restrained structure. For aluminum and steel spatial structures undergoing
extremely large temperature variations this may become an important issue to consider. However, in
most typical cases of spatial structures the tempe
temperature
rature effect may be neglected since the developed
stresses are negligible.

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Volume II Tools

Volume II Tools
Menu Commands

The CAESAR II piping input processor provides many commands, which can be run from the
menu, toolbars or accelerator keys. The menu options are:

The CAESAR II Main Menu

CAESAR II Main Menu CAESAR II may be started by double clicking the CAESAR II icon, or by running
C2.EXE from the CAESAR II installation directory. After starting CAESAR II, the Main Menu appears. It
is recommended that this screen be kept at its minimal size (as shown above). This allows access to
the toolbar while freeing most of the screen for other applications. The Main Menu is used to direct the
actions of CAESAR II. As elsewhere in CAESAR II commands may be accessed from menus, as well as
toolbars and/or keystroke combinations.

File Menu

The File menu may be used to do the following:

Set Default Data Directory— View or change the default

locations for database files.

New—starts a new piping or structural job. When New is

selected the user must designate whether this job is for a
piping or structural model. The data directory where the
file is to be placed must be selected, either by entering it directly or by browsing. Page | 5
Volume II Tools

Open—Opens an existing piping or

structural job. When Open is chosen the
user is prompted to select an existing job
file. Files of type “Piping,” “Pre-version 3.24
piping,” or “Structural” may be displayed
for selection (see below).

Clean Up (delete) Files— Enables users to

delete unwanted scratch files, listing files,
input, and output files to retain more hard
disk space.

Recent Piping & Structure—displays the

four most recently used piping or
structural files in the File menu.

Exit—Closes CAESAR II.

Input Menu

Once a file is selected, the Input Menu indicates the available modules for the file type chosen.

 Piping —Inputs
a CAESAR II piping model
 Underground —Converts existing piping model to buried pipe
 Structural Steel —Inputs a CAESAR II structural model
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Volume II Tools

Analysis Menu

The Analysis Menu allows the user to select from the different calculations available.

 Statics—Performs Static analysis of pipe and/or structure. This is available after error
checking the input file
 Dynamics—Performs Dynamic analysis of pipe and/or structure. This is also available after
error checking the input file.
 SIFs—Displays scratch pads used to calculate stress intensification factors at intersections
and bends.
 WRC 107/297—Calculates stresses in vessels due to attached piping.
 Flanges—Performs flange stress and leakage calculations.
 B31.G—Estimates pipeline remaining life.
 Expansion Joint rating—Evaluates expansion joints using EJMA equations.
 AISC—Performs AISC code check on structural steel elements.
 NEMA SM23—Evaluates piping loads on steam turbine nozzles.
 API 610—Evaluates piping loads on centrifugal pumps.
 API 617—Evaluates piping loads on compressors.
 API 661—Evaluates piping loads on air-cooled heat exchangers
 HEI Standard—Evaluates piping loads on feed water heaters.
 API 560—Evaluates piping loads on fired heaters

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Volume II Tools

Output Menu

The user is presented with all available output of piping and/or structural calculations, which may be
selected for review.

 Static—Displays Static results.

 Harmonic—Displays Harmonic Loading results.
 Spectrum Modal—Displays Natural Frequency/Mode Shape calculations or Uniform/Force
Spectrum Loading results.
 Time History—Displays Time History Load Simulation results.
 Animation— Displays Animated Graphic simulations of any of the above results.

Tools Menu

The Tools Menu includes various CAESAR II supporting utilities that are used for

 Configure/Setup—Customizes the behavior of CAESAR II, on a directory by directory basis.

Enables the user to consider items such as treatment of corrosion, pressure stiffening, etc.
differently for each directory, due to project or client considerations.
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 Calculator—Launches an on-screen calculator.
Volume II Tools

 Make Units files—Creates custom sets of units.

 Material Data Base—Edits or adds to the CAESAR II material database.
 Accounting—activates or customizes job accounting or generates accounting reports.
 Multi-Job Analysis—enables the user to run a stream of jobs without operator intervention.
 External Interfaces—Displays the interfaces to and from third party software (both CAD and
analytical).

Menu Commands

The CAESAR II Piping input processor provides many commands, which can be run from the menu,
toolbars or accelerator keys. The menu options are:

File Menu

The File menu is used to perform actions associated with opening, closing and running the job file.

File Menu for the Piping Input Screen

New Creates a new CAESAR II job. CAESAR II prompts for the name of the
new model.
Open Opens an existing CAESAR II job. CAESAR II prompts for the name
Save Saves the current CAESAR II job under its current name.
Save As Saves the current CAESAR II job under a new name.
Save As Graphic Saves the current CAESAR II job as an HTML page, .TIFF, .BMP, or .JPG
Image file.
Archive Allows the user to assign a password to prevent inadvertent alteration
of the model or to enter the password to unlock the file.
Start Run Sends the model through interactive error checking. This is the first
step of analysis, followed by the building of the static load cases
Batch Run Error checks the model in a non-interactive way and halts only for Page
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Volume II Tools

errors; uses the existing or default static load cases, and performs the
static analysis). The next step is the output processor.
Print Allows the user to print out an input listing. CAESAR II prompts the user
for the data items to include.
Print Preview Provides print preview of input listing.
Print Setup Sets up the printer for the input listing.
Recent File List Open a file from the list of most recently used
Jobs.

Edit Menu

The Edit menu provides commands for cutting and pasting, navigating through the
spreadsheets, and performing a few small utilities. These commands are

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Volume II Tools

Standard operation

There are several methods of accomplishing nearly every command in the Input
Plot Utility. Commands may be accessed by clicking buttons, selecting drop-
down menu items, or through the use of hot keys. Users may wish to verify
model data in single line mode; this often makes the view clearer, click the
Center Line View button. Note that in this mode, restraints and other element
information items still display. A Volume or double line plot can be obtained by
clicking the corresponding button. Also, pressing the V key on the keyboard will
switch the views in the following order: Gouraud Shading (rendered mode) /
Two Line Mode /Center Line View. Various orthogonal views can be obtained
by clicking the appropriate button, Front/Back/Top/Bottom/Left/Right.

Alternatively, using the X, Y, or Z keys on the keyboard will set the model in
right, top, or front views respectively. Additionally, holding down the SHIFT key
while pressing X, Y, or Z keys will show left, bottom, or back views respectively.
This option is useful to see the model just like it would be seen on a CAD
drawing. The transition from one orthogonal view to another is a smooth
transition. It is possible to make a sudden change/jump by pressing a
combination of the CTRL + ALT + F5 keys
before changing the view with one of the described options. The sudden jump
option is useful for relatively large models as it speeds up the viewing process.

Display Node numbers by clicking the Node Numbers button, by pressing the N
key on or by clicking Options/Node Numbers from then menu. Users can also
opt to display node numbers for a specific element i.e., only restraints or only
anchors. Users can display element lengths by clicking the Show Lengths button
or by pressing the L key on the keyboard. Alternatively, the same functionality
may be achieved from the menu by clicking Options/Lengths. This will display
the elements lengths to verify the input. Also Select By Single Click and using
the mouse to hover over the model produces a bubble displaying relevant
information for the desired element. For more information refer to the 3D
Graphics Highlights: Displacements, Forces, Uniform Loads, Wind/Wave Loads
section later in this chapter. All the highlighting and zoom/rotate effects on the
model as well as other effects may be reset at once by clicking the Reset Plot
button. The model returns to its default state as defined by the configuration;
any elements hidden by the Range command are restored, for more information
refer to the Range section for details

All the highlighting and zoom/rotate effects on the model as well as other
effects may be reset at once by clicking the Reset Plot button. The model returns
to its default state as defined by the configuration; any elements hidden by the
Range command are restored, for more information refer to the Range section
for details.

The model can be zoomed by clicking the Zoom button, and moving the mouse
up or down while depressing the left mouse button. Releasing the mouse button
halts the zoom. Note that while in the zoom mode, the keyboard + and - keys
may be used to zoom the model in and out. Alternatively, the model may also be
zoomed from under any other command or mode by rotating the mouse wheel
when applicable. The best way to zoom to a particular area of the model is to
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use the mouse to draw a rubber band box around the desired area. Simply click
Volume II Tools

the Zoom to Window button, then left-click one corner of the desired area, and stretch a box diagonally
to the opposite corner of the area while still holding the left mouse button down. When the left button
is released, the model zooms to the selected area. To see the entire model on the screen, click the Zoom
to Extents button.Interactive rotation of the model can be accomplished by clicking the Orbit button.
Oncethis mode is activated, rotate the model by using the mouse or the arrow keys on the keyboard.To
use a mouse for rotating the model, click the left mouse button on the model (the bounding box will be
drawn to outline the model boundaries; while holding down the left mouse button, move the mouse
around to the desired position. When the mouse button isreleased, the view is updated and the
bounding box disappears. If the bounding box is notvisible, check the corresponding box on the User
Options tab of the Plot Configurationdialog for more information refer to the 3D Graphics
Configuration section for details.

3D Graphics Configuration

The CAESAR II 3D Graphics engine remembers the state of the model between sessions.Exiting the
input completely and then returning to the input graphics results in the model being displayed in the
same state in which it was last viewed. The state of each model is maintained individually (job
related), as an XML data file (jobname.XML) in the current data directory. After launching another
input session, CAESAR II reads this XML file and restores the 3D graphics to its previous state. This
includes the rotation and zoom level of the model; color settings, data display, and the current graphics
operator.

3D Graphics Highlights: Displacements, Forces, Uniform Loads, Wind/Wave

Loads

The 3D/HOOPS Graphics engine can display applied/predefined

displacements, forces, uniform loads, or wind/wave loads in a tabular format. The
display windows can be scrolled vertically and or horizontally to view all node points
where data has been defined. To flip through the defined displacement or force
vectors 1 through 9, use the Next and Previous buttons at the bottom of the tabular
legend window. The color key at the far left of the window assists in locating the node
points on the model (when the model geometry is complex).Note that the
displacements window shows the user specified values as well as free or fixed
Degrees of Freedom (DOF). In this case, a DOF is free if a displacement value is not
specified in any of the displacement load vectors. Note also that if a certain DOF has a
specified displacement in at least one of the load vectors, then it is fixed in all other Page | 12
Volume II Tools

load vectors.Forces behave similar to the Displacements option, the model elements are highlighted
for a particular force vector, and the color key legend grid window displays on the left. The node
number in combination with a color key specifies the location where the force and moment values are
defined. Uniform Loads has three vectors defined. The Node column represents the start node number
where the uniform loads vector was first defined. Since the data propagates throughout the model
until changed or disabled, the model is colored accordingly. Wind/Wave displays the loading
coefficients. The color key is defined as follows: all the elements with wind defined are colored in red
color; all the elements with wave data defined are colored in green color. The legend grid shows the
relevant data items defined by the user.

Select by Single Click allows users to obtain element data. When enabled, hovering over a pipe element
with the mouse shows a bubble with the element's nodes, delta dimensions, and pipe size data.
Clicking on an element highlights the element and updates the information on the spreadsheet.
Clicking a different element highlights the relevant element and changes the data in the spreadsheet
accordingly

Limiting the Amount of Displayed Info.; Find Node, Range & Cutting Plane

Sometimes it is necessary to limit the amount of displayed information

on the screen. This may be useful when the model is large, or if it has many
similar looking branches. There are several ways to achieve this result by
clicking either the Find Node, Range, or Cutting Plane button. The description of
these operations, their advantages and disadvantages are illustrated below.
Find Node is useful when a specific node or an element needs to be located.
Clicking Find Node displays a dialog prompting for the FROM and TO nodes to
search for. The node numbers can be entered in either of the two fields, or in
both. Entering only the FROM node number causes the feature to search for the
first available element that starts with the specified node number. Entering
only the TO node number causes the feature to search for an element ending
with the specified node number. When the element is located, it is highlighted,
and the view zooms to the element. Users may zoom out to better identify the location of the
highlighted element within the model. In many cases, the elements/node numbers are not defined
consecutively. Thus, it may be easier to cut a portion of the model at a certain location to see more
details.
For this operation, use the Create Cutting Plane button. When the cutting plane appears, use the
handles to move and or rotate the plane as desired. If cutting the plane's handles are not visible, or the
display goes blank, the view may be focused too close for the plane to operate correctly. Use the Zoom
button to zoom out; then click the Cutting Plane button again for the handles to appear. To disable the
cutting plane and return to normal view click on the display with the right mouse button. Note, the
Create Cutting Plane option can be used along any of the three axis.

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Volume II Tools

Range

Range plots only those elements that contain nodes within the
range specified by the user. This is particularly helpful when
attempting to locate specific nodes or a group of related elements
in a rather large, often symmetrical model. Click the Range button
or press the U key to display the Range dialog.

A sorted list of all defined node numbers with corresponding check marks appears. Clicking
a check box next to a particular node number will enable or disable it.

Annotations

Used to highlight a problem area, or write a brief description of the

model. The annotation may be especially useful in the output processor
for more information refer to the discussion at the end of this section. The
CAESAR II 3D/HOOPS Graphics processor provides several types of
annotation as discussed below.

When the Annotate Model button is clicked, the annotation text box with
a leader line to an element is added to the graphics view. To add the annotation, click with the left
mouse button on a particular element to start the leader line, while holding the mouse button
down drag the leader line to the annotation point, then type in the annotation text, and then press the
Enter key.

Other annotation options are listed below:

Freehand Markup Operator - Allows redlining based on the user moving

the mouse.

Rectangle Markup - Allows redlining using a rectangular shape. This option is

useful when trying to emphasize a specific element Circle Markup - Allows
redlining using a circular shape. This option is useful when trying to emphasize
a specific element
Annotate Operator - Allows the user to enter text and place it anywhere in the
plot area. It may be used to add a short description of the model to the graphics
image for printing or saving as a bitmap.

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Volume II Tools

Error Checking

Static analysis cannot be performed until the error checking portion of the
piping preprocessor has been successfully completed. Only after error
checking is completed are the required analysis data files created.
Similarly, any subsequent changes made to the model input are not
reflected in the analysis unless error checking is rerun after those changes
have been made. CAESAR II does not allow an analysis to take place if the
input has been changed and not successfully error checked.

Error Checking can only be done from the input spreadsheet, and is initiated by executing the Error
Check or Batch Run commands from the toolbar or menu. Error Check saves the input and starts the
error checking procedure.

Batch Run causes the program to check the input data, analyze the system, and present the results
without any user interaction. The assumptions are that the loading cases to be analyzed do not need to
change and that the default account number (if accounting active) is correct. These criteria are usually
met after the first pass through the analysis. Batch processing focuses the user’s attention on the
creation of input and the review of output by expediting the steps in between. Once launched, the
error checker reviews the CAESAR II model and alerts users to any possible errors, inconsistencies, or
noteworthy items. These items display to users as Errors, Warnings, or Notes in a grid. The total
number of errors, warnings, or notes displays in corresponding text fields above the Message Grid.
Users may sort messages in the Message Grid by type, message number or element/node number by
double-clicking the corresponding column header. Users can also print messages displayed in the
Message Grid by clicking File/Print.

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Volume II Tools

Fatal Error Message

Errors are flagged when there is a problem with the model due to which analysis cannot continue. An
example of this would be if no length were defined for a piping element. These errors are also called
fatal errors, since they are fatal to the analysis, and must be
corrected before continuing. Clicking on the error message will move the spreadsheet display to the
offending element. Users can change the view between the spreadsheet and error warning views using
the tabs located at the bottom of the window.

Warning Message

Warnings are flagged whenever there is a problem with a model, which can be overcome using some
assumptions. An example of this would be if an element’s wall thickness were insufficient to meet the
minimum wall thickness for the given pressure (hoop stress). Warnings need not be corrected in order
to get a successful analysis, but users should review all warnings carefully as they are displayed.

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Volume II Tools

Continue Moves the spreadsheet to the next element in the model, adding a new
element if there is no next element.
Insert Inserts an element either before or after the current element
Delete Deletes the current element.
Find Allows the user to find an element containing one or more named nodes
(if two nodes are entered, the element must contain both nodes).
Enabling the Zoom To check box will display the element if found.
Duplicate Copies the selected element either before or after the current element.
Global Prompts the user to enter global (absolute) coordinates for the first
node of any disconnected segments
Close Loop Closes a loop by filling in the delta coordinates between two nodes on
the spreadsheet.
Increment Gives the user the opportunity to change the automatic node increment.
Distance Calculates the distance between the origin and a node, or between two
nodes.
List Presents the input data in an alternative, list format that displays a drop
down menu where users can select any list. This provides the benefit of
showing all of the element data in a context setting. The list format also
permits block operations such as Duplicate, Delete, Copy, Renumber on
the element data. For more information on the list input format, see the
Technical Reference Manual.
Go to First Element, [Pg Dn], [Pg Up], Ctrl +[Home], Ctrl +[End]—Allows users to move
Previous Element, Skip throughout the elements of a model. Note [Pg Dn] does not create a new
to Next Element, element once the end of the model is reached.
Skip to Last Element
Edit Static Load Case Opens the Static Load Case Editor window. This button is enabled when
the job is error checked.
Edit Dynamic Load Case Opens the Dynamic Load Case Editor window. This button is enabled
when the job is error checked.
View Output Allows users to review the output report, provided
the analysis was successfully completed
Review Current Units Located on the Edit Menu it allows users to review units used to create
the report file. Changing units in the configuration file will not affect the
input. To change Input units from the Main Menu use Tools-Convert
Input to New Units.
Undo/Redo Any modeling steps done in the CAESAR II input module may be
"undone", one at a time, using the Undo command, activated by clicking
the Undo button on the toolbar, the Edit-Undo menu option, or the Ctrl-Z
hot key. Likewise, any "undone" steps may be "redone" sequentially,
using the Redo command, activated by the Redo button on the toolbar,
the Edit-Redo menu option, or the Ctrl-Y hot key. An unlimited number
of steps (limited only by amount of available memory) may be undone.
Note that making any input change while in the middle of the "undo
stack" of course resets the "redo" stack.

Page | 17
Volume II Tools

Model Menu

The Model menu contains modeling aids, as well as means for entering associated, system wide
information.

Break Allows the user to break the element into two unequal length elements
or into many equal length elements. A single node may be placed as a
break point anywhere along the element, or multiple nodes may be
placed at equal intervals (the node step interval between the From
and To nodes determines the number of nodes placed). Break Element
Valve Allows the user to model a valve or flange from one of the CAESAR II
databases. Choosing a combination of Rigid Type, End Type, and Class
constructs a rigid element with the length and weight extracted from
the database.
Expansion Joints Activates the Expansion Joint Modeler. The modeler automatically
builds a complete assembly of the selected expansion joint style, using
the bellows stiffnesses and rigid element weights extracted from one
of the vendors’ expansion joint catalogs.
Title Allows the user to enter a job title up to sixty lines long.
By pressing <Ctrl>T at any time during pipe spreadsheet input, the
current job's title page will be displayed (also may access through the
MODEL - TITLE menu item). This is up to 60 lines of text that is stored
with the problem, and may be used for detailing run histories,
discussing assumptions, etc. These lines may be printed with the
output report through the input
echo.
Hanger Design Control Prompts the user for system - wide hanger design criteria
Data

Page | 18
Volume II Tools

Environment Menu

The Environment menu provides some miscellaneous items.

Environment Menu

Review SIFs at Intersection Nodes Allows the user to run “what if” tests on the
Stress Intensification Factors of intersections.
Review SIFs at Bend Nodes Allows the user to run “what if” tests on the
Stress Intensification Factors of selected bends.
Special Execution Parameters Allows the user to set options affecting the
analysis of the current job. Items covered
include ambient temperature, pressure
stiffening, displacements due to pressure
(Bourdon effect), Z-axis orientation, etc.

Page | 19
Volume III Modelling

Volume III Modeling

Classic piping input for modeling

Node Number

Each element is identified by its end “node” number. Since each input screen represents a piping
element, the element end points - the From node and To node must be entered. These points are used
as locations at which information may be entered or extracted. The From node and To node are both
required data fields. CAESAR II can generate both values if the AUTO_NODE_INCREMENT directive is
set to other than zero using the Tools-Configure/Setup option of the Main Menu.

Page | 20
Volume III Modelling

Node Names

Activating this checkbox allows the user

to enter text names for the From and/or To
nodes (up to ten characters). These names
display instead of the node numbers on the
graphic plots and in the reports (note some of the
names may be truncated when space is not
available).

Note CAESAR II can generate both values

if the AUTO NODE INCREMENT directive is set to
other than zero using the Tools-Configure/Setup
option of the Main Menu.

Element Lengths

Lengths of the elements are entered as delta dimensions

according to the X, Y, and Z rectangular coordinate system
established for the piping system (note that the Y-axis represents
the vertical axis). The delta dimensions DX, DY, and DZ, are the
measurements along the X, Y, and Z-axes between the From node
and To node. In most cases only one of the three cells will be used
as the piping usually runs along the global axes. Where the piping
element is skewed two or three entries must be made. One or
more entries must be made for all elements except “zero length” expansion joints. Note When using
feet and inches for compound length and length units, valid entries in this (and most other length
fields) include formats such as: 3-6, 3 ft. -6 in, and 3-6- 3/16.

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Volume III Modelling

Pipe Section Properties

The elements outside diameter, wall thickness, mill

tolerance (plus mill tolerance is used for IGE/TD/12 piping
code only), and seam weld (IGE/TD/12 piping code only);
corrosion allowance, and insulation thickness are entered in
this block. These data fields carry forward from one screen to
the next during the input session and need only be entered for
those elements at which a change occurs. Nominal pipe sizes
and schedules may be specified; CAESAR II converts these
values to actual outside diameter and wall thickness. Outside
diameter and wall thickness are required data inputs.

Pipe Section Data

Diameter
The Diameter field is used to specify the pipe diameter. Normally, the nominal diameter is
entered, and CAESAR II converts it to the actual outer diameter necessary for the analysis. There are
two ways to prevent this conversion: use a modified UNITS file with the Nominal Pipe Schedules
turned off, or enter diameters whose values are off slightly from a nominal size (in English units the
tolerance on diameter is 0.063 in.). Use <F1> to obtain additional information and the current units for
this input field. Available nominal diameters are determined by the active pipe size specification, set
via the configuration program. The following are the available nominal diameters.

ANSI Nominal Pipe ODs, in inches (file ap.bin)

½ ¾ 1 1 ½ 2 2 ½ 3 3 ½ 4 5 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 42

JIS Nominal Pipe ODs, in millimeters (file jp.bin)

15 20 25 32 40 50 65 80 90 100 125 150 200 250300 350 400 450 500 550 600 650

DIN Nominal Pipe ODs, in millimeters (file dp.bin)

15 20 25 32 40 50 65 80 100 125 150 200 250 300 350 400 500 600 700 800 900 1000 1200 1400
1600 1800 2000 2200

Wt/Sch
The Wall Thickness/Schedule field is used to specify the thickness of the pipe. Normal input
consists of a schedule indicator (such as S, XS, or 40), which will be converted to the proper wall
thickness by CAESAR II. If actual thickness is entered, CAESAR II will accept it as entered. Available
schedule indicators are determined by the active piping specification, set via the configuration
program. The available schedules are listed below.

ANSI B36.10 Steel Nominal Wall Thickness Designation

 S - Standard
 XS - Extra Strong
 XXS - Double Extra Strong

ANSI B36.10 Steel Pipe Numbers

10 20 30 40 60 80 100 120 140 160

ANSI B36.19 Stainless Steel Schedules Page | 22
Volume III Modelling

5S 10S 40S 80S

Corrosion

Enter the corrosion allowance to be used order to calculate a reduced section modulus. A “setup file”
directive is available to consider all stress cases as corroded.

Insulation Thick

Enter the thickness of the insulation to be applied to the piping. Insulation applied to the
outside of the pipe will be included in the dead weight of the system, and in the projected pipe area
used for wind load computations. If a negative value is entered for the insulation thickness, the
program will model refractory lined pipe. The thickness will be assumed to be the thickness of the
refractory, inside the pipe.

Operating Conditions: Temperatures and Pressures

Up to nine temperatures and ten pressures (one

extra for the hydrostatic test pressure) can be specified
for each piping element. (The button with the ellipses
dots is used to activate a window showing extended
operating conditions input). The temperatures are actual
temperatures (not changes from ambient). CAESAR II
uses these temperatures to obtain the thermal strain and
allowable stresses for the element from the Material
Database. As an alternative, the thermal strains may be
specified directly (see the discussion of ALPHA
TOLERANCE in the Technical Reference Manual).
Thermal strains have absolute values on the order of
0.002, and are unit less. Pressures are entered as gauge
values and may not be negative. Each temperature and
each pressure entered creates a loading for use when
building load cases. Both thermal and pressure data
carries forward from one element to the next until
changed. Entering a value in the Hydro Pressure field
causes CAESAR II to build a Hydro case in the set of
recommended load cases.

Note CAESAR II uses an ambient temperature of

70°F, unless changed using the Special Execution Parameters Option.
T1 – Max temp, T2 – Min temp, T3 – Min summer temp,T4 – Max winter temp
T5 – Max temp (flow induced) (optional), T6 – Min temp (flow induced) (optional)

P1 – MIP, P2 – MOP, P3 – Compressor operation, P4 – Demand pressure

HP – Hydrotest pressure

Page | 23
Volume III Modelling

Piping Material

CAESAR II requires the specification of

the pipe material’s elastic modulus, Poisson’s
ratio, density, and (in most cases) expansion
coefficient. The program provides a database
containing the parameters for many common
piping materials. This information is retrieved by picking a material from the drop list, by entering the
material number, or by typing any the entire material name and then picking it from the match list.
(The coefficient of expansion does not appear on the input screen, but it can be reviewed during error
checking.) Note that materials 18 and 19 represent cold spring properties, cut short and cut long
respectively; material 20 activates CAESAR II’s orthotropic model for use with materials such as
fiberglass reinforced plastic pipe. Material 21 permits a totally user defined material. Using a material
with a number greater than 100 permits the use of allowable stresses from the database.

Material Elastic Properties

This block is used to enter or override

the elastic modulus and Poisson’s ratio of the
material, if the value in the database is not
correct. These values must be entered for
Material type 21 (user specified).

Note Material properties in the

database may be changed permanently using
the CAESAR II Material Database editor.

Densities

The densities of the piping material,

insulation, and fluid contents are specified in
this block. The piping material density is a
required entry and is usually extracted from
the Material Database. Fluid density can
optionally be entered in terms of specific
gravity, if CAESAR II - User Guide Auxiliary
Data Area Piping Input 5-9 convenient, by
following the input immediately with the
letters: SG, e.g. 0.85SG (there can be no
spaces between the number and the SG).

Note If an insulation thickness is specified (in the pipe section properties block) but no
insulation density is entered, CAESAR II defaults to the density of calcium silicate.

Rockwool / Mineral wool Range

Rock Fiber is an Insulation material that is light in weight, made up of intermingled vitreous
fibers composed of complex silicates. It is available in various forms like Loose Wool, Preformed
Mattresses, Resin Bonded Slabs and Pipe Sections conforming to IS, ASTM, BS, JIS, DIN standards
MINROCK’ Lightly Resin Bonded Rock wool Mattresses of densities 85, 100, 120, 128 and 150
Kg/M3 and Thicknesses of 25mm, 40mm, 50mm, 65mm, 75mm, & 100mm are duly machine laid and
Page | 24
Volume III Modelling

machine stitched with one side/both sides wire netting conforming to IS: 8183/93 and are packed in
Poly-Bonded HDPE Woven bags.
AUXILAIRY DATA

Codes

The piping codes are listed in the following table. Their current publication dates can be found in the
CAESAR II Quick Reference Guide.

B31.1 Swedish Power Piping Code (Method 1)

B31.3 Swedish Process Piping Code (Method 2)
B31.4 B31.1 - 1967
B31.4, Chapter IX Stoomwezen
B31.5 RCC-M C
B31.8 RCC-M D
B31.8, Chapter VIII CODETI
B31.11 Norwegian TBK-6
ASME Sect III NC (Class 2) FDBR
ASME Sect III ND (Class 3) BS 7159
Navy 505 UKOOA
CAN/CSA Z662 IGE/TD/12
CAN/CSA Z662, Chapter 11 DNV
BS 806 GPTC/192
EN-13480

Each of the input data cells is discussed in general in the following section. For more information about
code compliance considerations see Chapter 6 of the Technical Reference Manual.
SC (UNITS: KPa )
Typically the cold allowable stress for the specific material taken directly from the governing piping
code. The value of SC will usually be divided by the longitudinal weld efficiency (Eff) before being
used. See the notes that follow for the specific piping code.
SH(UNITS: KPa )
Typically the hot allowable stress for the specific material taken directly from the governing piping
code. A value must be entered for each defined temperature case. The value of SH will usually be
divided by the longitudinal weld efficiency (Eff) before being used. See the recommendations

Special Element Information

Special components such as bends, rigid

elements, expansion joints and tees require
additional information, which can be
defined by enabling the component and
entering data in the auxiliary screen. If the
element described by the spreadsheet ends
in a bend, elbow or mitered joint, the Bend
checkbox should be set by double-clicking. This entry opens up the auxiliary data field on the right
hand side of the input screen to accept additional data regarding the bend. CAESAR II usually assigns
three nodes to a bend (giving ‘near’, ‘mid’, and ‘far’ node on the bend). Double-clicking thePage | 25
Rigid
Volume III Modelling

checkbox (indicating an element that is much stiffer than the connecting pipe such as a flange or valve)
opens an auxiliary data field to collect the component weight. For rigid elements, CAESAR II follows
these rules:

When the rigid element weight is entered, i.e. not zero, CAESAR II computes any extra weight due to
insulation and contained fluid, and adds it to the user-entered weight value.

The weight of fluid added to a non-zero weight rigid element is equal to the same weight that would be
computed for an equivalent straight pipe. The weight of insulation added is equal to the same weight
that would be computed for an equivalent straight pipe times 1.75.
If the weight of a rigid element is zero or blank, CAESAR II assumes the element is an artificial
“construction element” rather than an actual piping element, so no insulation or fluid weight is
computed for that element.
The stiffness of the rigid element is relative to the diameter (and wall & thickness) entered. Make sure
that the diameter entered on a rigid element spreadsheet is indicative of the rigid stiffness that should
be generated.

If an element is an expansion joint, double-clicking that checkbox brings up an auxiliary screen, which
prompts for stiffness parameters and effective diameter. Expansion joints may be modeled as zero-
length (with all stiffnesses acting at a single point) or as finite CAESAR II - User Guide Data Fields
Piping Input 5-7 length (with the stiffnesses acting over a continuous element). In the former case, all
stiffnesses must be entered, in the latter; either the lateral or angular stiffness must be omitted.
Checking the SIF & Tees checkbox allows the user to specify any component having special stress
intensification factors (SIF). CAESAR II automatically calculates these factors for each component.

Note Bends, rigids, and expansion joints are mutually exclusive. Refer to the valve/ flange and
expansion joint database discussions later in this chapter for quick
entry of rigid element and expansion joint data.

Boundary Conditions

The checkboxes in this block open the

auxiliary data field to allow the input of
items, which restrain (or impose movement
on) the pipe— restraints, hangers, flexible
nozzles or displacements. Though not
required, it is recommended that such information be supplied on the input screen which has that
point as the From node or To node. (This will be of benefit if the data must be located for
modification). The auxiliary data fields allow specification of up to 4 restraints (devices which in some
way modify the free motion of the system), one hanger, one nozzle, or two sets of nodal displacements
per element. If needed, additional items for any node can be input on other element screens.

Loading Conditions

The checkboxes in this block allow the user to

define loadings acting on the pipe. These loads
may be individual forces or moments acting at
discrete points, distributed uniform loads
(which may be specified on force per unit
length, or gravitational body forces), or wind
loadings (wind loadings are entered by specifying a wind shape factor—the loads themselves are
specified when building the load cases. The uniform load and the wind shape factor check boxes will
Page | 26
Volume III Modelling

be unchecked on subsequent input screens. This does not mean that the loads were removed from
these elements; instead, this implies that the loads do not change on subsequent screens.

Note Uniform loads may be specified in g-values by setting a parameter in the Special Execution
Options.

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Volume V Supports

Volume IV Component
Bend

 Bend Definition
 Single and Double Flanged
 180 Degree Return Fitting-To-Fitting 90 Degree Bends
 Mitered Bends
 Closely Spaced Mitered Bend
 Widely Spaced Mitered Bend
 Elbows - Different Wall Thickness
 Bend Flexibility Factor

Bend Definition

Bends are defined by the element entering

the bend and the element leaving the bend. The
actual bend curvature is always physically at the
TO end of the element entering the bend. The
input for the element leaving the bend must
follow the element entering the bend. The bend
angle is defined by these two elements. Bend
radius defaults to 1 1/2 times the pipe nominal
diameter (long radius), but may be changed to
any other value. Specifying a bend automatically
generates two additional intermediate nodes, at
the 0-degree location and at the bend midpoint
(M). For stress and displacement output them TO
node of the element entering the bend is located
geometrically at the far-point on the bend. The
far-point is at the weldline of the bend, and
adjacent to the straight element leaving the bend.
The 0-degree point on the bend is at the weldline
of the bend, and adjacent to the straight element
entering the bend.

The FROM point on the element is located

at the 0-degree point of the bend (and no 0-
degree node point will be generated) if the total
length of the element as specified in the DX, DY,
and DZ fields is equal to: R tan (β / 2) Where β is
the bend angle, and R is the bend radius of
curvature to the bend centerline. Nodes defined
in the Angle and Node fields are placed at the given angle on the bend curvature. The angle starts with
zero degrees at the near-point on the bend and goes to β degrees at the far-point of the bend. Angles
are always entered in degrees. Entering the letter M as the angle designates the bend midpoints. Nodes
on the bend curvature cannot be placed closer together than specified by the Minimum Angle to
Adjacent Bend parameter in the Configure-Setup—Geometry section. This includes the spacing
between the nodes on the bend curvature and the near and far-points of the bend.

The minimum and maximum total bend angle is specified by the Minimum Bend Angle and maximum
Bend Angle parameters in the Configure Setup—Geometry section. Double-click the Bend checkbox.
Page | 28
Volume V Supports

The Bends tab displays. This adds a long radius bend at the end of the element, and adds intermediate
nodes 18 and 19 at the near weld and mid points of the bend respectively (node 20 physically
represents the far weld point of the bend).

Single and Double Flanged Bends or Stiffened Bends

Single and double flanged bend specifications only effect the stress intensification and
flexibility of the bend. There is no automatic rigid element (or change in weight) generated for the end
of the bend.

Single and double-flanged bends are indicated by entering 1 or 2 (respectively) for the Type in
the bend auxiliary input. Rigid elements defined before or after the bend will not alter the bend's
stiffness or stress intensification factors.
When specifying single flanged bends it does not matter which end of the bend the flange is on.
If the user wishes to include the weight of the rigid flange(s) at the bend ends, then he/she
should put rigid elements (whose total length is the length of a flange pair) at the bend ends where the
flange pairs exist.
As a guideline, British Standard 806 recommends stiffening the bends whenever a component
that significantly stiffens the pipe cross section is found within two diameters of either bend end.
The flanges in the figures below are modeled only to the extent that they affect the stiffness
and the stress intensification for the bends.

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Volume V Supports

Flanged Bends
Singl Flange

Double Flange

180 Degree Return Fitting-To-Fitting 90 Degree Bends

Two 90-degree bends should be separated by twice the bend radius.

The far-point of the first bend is the same as the near-point of the second (following) the bend.
The user is recommended to put nodes at the midpoint of each bend comprising the 180 degree
return. (See the example below.)

180 Degree Return Fitting (180 Degree bend)

Step :1

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Volume V Supports

Step: 2

Step: 3

Step :4

Step: 5

Thick Elbow

Page | 31
Volume V Supports

Bend Flexibility Factor

Normally bend flexibility factors are calculated according to code requirements. However, the
user may override the code calculation by entering a value in the K-factor field. For example, if the user
enters 1.5 in this field, the bend will be 1.5 times as flexible as a straight pipe of the same length.

Reducers

Page | 32
Volume V Supports

Reducer
To model reducers use the procedure listed below Modeling Reducers Using CAESAR

Concentric Reducer

Eccentric reducer

Define the length of the reducer just like any other pipe element. For eccentric reducers be
sure to skew the element such that the TO node matches the position of the centerline of the following
pipe elements. Double click the Reducer check box on the input spreadsheet. If the element preceding
and following the reducer are already defined (such as inserting this element) then CAESAR will
automatically calculate all the reducer input data and the user can leave this field blank. Enter the
diameter and wall thickness of the pipe that will follow the reducer. Nominal diameter and wall
thickness can be entered here and CAESAR will convert these to actual diameter and wall thickness if
this portion is activated in the units file (in the Diameter and Wt/Sch fields on the spreadsheet convert
nominal to actual then so will the Reducer dialog). Alpha is the slope of the reducer transition in
degrees. If left blank, the value will be set from an estimated slope equal to the arc tangent times 1/2
the change in diameters times sixty percent of the entered reducer length.

Tee

Pipe Tee is a type of pipe fitting which is T-shaped having two outlets, at 90° to the connection
to the main line. It is a short piece of pipe with a lateral outlet. Pipe Tee is used to connect pipelines
with a pipe at a right angle with the line. Pipe Tees are widely used as pipe fittings. They are made of
various materials and available in various sizes and finishes. Pipe tees are extensively used in pipeline
networks to transport two-phase fluid mixtures. There are two types as below

Tee – Equal

Three-port fitting in the shape of a "T". Standard configuration ("Equal") indicates that the
straight-through path (typically called the "run") and the perpendicular section ("branch") all have the
same size ports.

Tee – Reducing

Page | 33
Volume V Supports

Typically, this describes a tee fitting in which the branch port is smaller than the ports of the
run; it may also include size reduction from one of the run ports to the other. Node no 70 to 200
change the pipe diameter and wall thick.

Node 70 is the intersection of the 8

8-in. and 6-in.
in. lines. This intersection is constructed using an
8x6 welding tee. Piping codes recognize the reduced strength of this piping component by increasing
the calculated stress at this point in the system. For CAESAR II to include this stress intensification
factor in the stress calculation, the node must be identified as a welding tee. First double click the SIFs
and Tees check box to activate the SIFs and Tees Auxiliary data area. Specify node 70 as our
intersection
ction node and select Welding Tee from the Type drop list. CAESAR II will calculate the SIFs at
this intersection according to the piping code selected (B31.3 in this case) so no more input is needed
here.

Input Items Optionally Effecting SIF Calculations

1 REINFORCED FABRICATED TEE

2 UNREINFORCED FABRICATED TEE
3 WELDING TEE
4 SWEEPOLET
5 WELDOLET
6 EXTRUDED WELDING TEE
7 GIRTH BUTT WELD
8 SOCKET WELD (NO UNDERCUT)
9 SOCKET WELD (AS WELDED)
10 TAPERED TRANSITION
11 THREADED JOINT
12 DOUBLE WELDED SLIP-ONON
13 LAP JOINT FLANGE (B16.9)
14 BONNEY FORGE SWEEPOLET Page | 34
Volume V Supports

15 BONNEY FORGE LATROLET

16 BONNEY FORGE INSERT WELDOLET
17 FULL ENCIRCLEMENT TEE

This auxiliary screen is used to enter stress

intensification factors, or fitting types for up to two
nodes per spreadsheet. If components are selected
from the drop list, CAESAR II automatically
calculates the SIF values as per the applicable code
(unless overridden by the user). Certain fittings and
certain codes require additional data as shown.
Fields are enabled as appropriate for the selected
fitting.

Rigid (Weight of Rigid elements) Valve & flange

The next element (80-90) is the flanged check valve. This CAESAR II element would include the
flanged valve and the mating flanges as these piping components are much stiffer than the attached
pipe. If the length and weight of this “rigid” element were known, this data could be entered directly by
entering the length in the DY field, enabling the Rigid box and then entering the Rigid Weight in the
Auxiliary Data area. Here, for lack of better data and for convenience, the CAESAR II Valve/Flange
database will be accessed to generate this input automatically. This data is made available through the
Model-Valve menu option or by clicking the Valve/Flange Database button on the toolbar. This
command will bring up the window shown below.

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Volume V Supports

Butt-weld Gate valve

Flanged Gate Valve

Expansion Joints

Activate by double-clicking the Expansion Joint check box on the Pipe Element Spreadsheet. Deactivate
by double-clicking a second time
Bellows Stiffness Properties (UNITS: Translational N./cm. Rotational N.m./deg )
If the element length is zero then the user should define all stiffnesses. If the element length is not zero
then either the bending or the transverse stiffness should be left blank. CAESAR II will automatically
calculate the stiffness not entered. (For rubber expansion joints, all stiffnesses may be entered.)
If the torsional stiffness value is not specified, CAESAR II will use a default value of 0.11298E+05.
Page | 36
Volume V Supports

Bending "STIFFNESSES" from EJMA (and from most

expansion joint manufacturers) that are to be used in a finite
length expansion joint model should be multiplied by (4)
before being used in any piping program. Bending
"STIFFNESSES" from EJMA (and from most expansion joint
manufacturers) that are to be used in a ZERO length
expansion joint model should be used without modification.
Use (1.0) for bellows stiffnesses that are completely flexible.
Use (1.0E12) for rigid bellows stiffnesses.
Zero Length expansion joints can be used in many modeling
applications to define struts, hinged ends, etc. The
orientation of zero length expansion joints is taken from the
element that precedes the expansion joint providing the
"TO" node of the preceding element is equal to the "FROM"
node on the expansion joint element. If the preceding
element does not go "INTO" the expansion joint, then the
orientation will be taken from the element that follows the
expansion joint providing it properly "LEAVES" the joint.

Effective ID (UNITS: mm.)

The effective inside diameter for pressure thrust (from the

manufacturer's catalog). For all load cases including
pressure CAESAR II will calculate the pressure "thrust force"
tending to blow the bellows apart (provided the pressure is positive). If left blank, or zero, then no
axial thrust force due to pressure will be calculated. Many manufacturers give the effective area of the
expansion joint: Aeff. The Effective ID is calculated from the effective area by:

Vo
lu
m
e
V

Page | 37
Volume V Supports

Supports
Restrains

Supports are provided to the piping to resist various loads. The loads can be classified into
three categories. They are: primary loads, secondary loads and occasional loads. The response of the
piping to various loads is different. The primary load is also known as sustained load. The primary
loads are due to the self-weight of the piping, its contents, insulation, refractory, inner casing, outer
casing, internal pressure and external pressure. The secondary loads are due to temperature change
and relative settlement of foundations. The occasional loads are due to wind, earthquake, water
hammer, steam hammer, safety valves blowing jet reactions, surge load, blast load and accidental
loads.
If the piping is not provided with adequate supports, it will be over-stressed and excessively
deform. Over-stressing will cause premature failure. Excessive deformation will impair the
performance of the piping.

Restraint Type Abbreviation

Anchor ANC
Translational Double Acting X, Y, or Z
Rotational Double Acting RX, RY, or RZ
Guide, Double Acting GUIDE
Double Acting Limit Stop LIM
Translational Double Acting Snubber XSNB, YSNB, ZSNB
Translational Directional +X, -X, +Y, -Y, +Z, -Z
Rotational Directional +RX, -RX, +RY, etc.
Directional Limit Stop +LIM, -LIM
Large Rotation Rod XROD, YROD, ZROD
Translational Double Acting Bilinear X2, Y2, Z2
Rotational Double Acting Bilinear RX2, RY2, RZ2
Translational Directional Bilinear -X2, +X2, -Y2, etc.
Rotational Directional Bilinear +RX2, -RX2, +RY2, etc.
Bottom Out Spring XSPR, YSPR, ZSPR
Directional Snubber +XSNB, -XSNB, +YSNB, etc.

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Volume V Supports

 Anchor
 +Y Restrains (shoe Support)
o Vertical Pipe Line
o Horizontal Pipe Line
 Guide
o Vertical Pipe Line
o Horizontal Pipe Line
 Line Stopper ( Axial Stopper)
 Line Stopper with +Y Restrain
 Limit stop
 Limit Stop With + Y Restrain
 Rod Hanger
 Spring hanger
o Constant Spring Hanger (CSH)
o Variable Spring Hanger (VSH)

CNode

The CNode, or connecting node number, is used only when the other end of the hanger is to be
connected to another point in the system, such as another pipe node.

ANCHOR

An anchor is rigid restraints providing full fixation, i.e., permitting neither translator
movement (in X-, Y- and Z- direction) not rotation (around X-, Y- and Z-axis). An anchor provides a
fixed reference point of constant position and rotation. Through which effects from the pipe on
opposite sides cannot be transmitted. This makes the anchor a convenient terminal point for defining
stress analysis problem. A pipe anchor is a rigid support that restricts movement in all three
orthogonal directions and all three rotational directions. This usually is a welded stanchion that is
welded or bolted to steel or concrete

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Volume V Supports

Anchor Support

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Volume V Supports

Anchors with Displacements

Follow these general guidelines to model anchors with displacements:

 Enter only displacements for the node.
 Do not specify restraints or anchors at the node to be displaced.
 For anchors with displacements, make sure all 6 degrees of freedom at the node are
defined.

Up to 9 different displacement vectors (i.e., D1...D9) may be defined.

Non-zero displacements are usually part of the thermal expansion effects and, if so, should normally be
added into any analysis case containing the corresponding thermal, i.e
W+P1+T1+D1. The CAESAR II recommended load cases do this automatically.

Flexible Anchors

Follow these guidelines to model flexible anchors:

 Use six flexible restraints.
 Put four restraints on one spreadsheet and the last two restraints on the next element
spreadsheet.
 See the following flexible nozzle examples to improve modeling methods for intersections of
this type.

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Volume V Supports

Flexible Anchors with Predefined Displacements

To model flexible anchors with predefined displacements, implement the following requirements:
Use six flexible restraints.
Put four restraints on one spreadsheet and the last two restraints on the next element spreadsheet.
Define a unique connecting node (CNode), at each of the six restraints. All six restraints should have
the same connecting node.
Specify the displacements at the connecting node.

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Volume V Supports

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Volume V Supports

+Y Restrain (Shoe Support)

Restraints are provided in the piping primarily to transfer the Sustain loads to the supporting
structure. Restraints are usually oriented in any one of the coordinate axes of the plant. Inclined
restraints are also used. Usually the restraints are double acting. Struts and ties, which are single
acting, are also used. A single acting restraint is a device, which carries only tension or compression.

+Y Restrain ( Shoe Support) +Y Restrain (Shoe Support)For

For Horizontal Pipe Line Vertical Pipe Line

Single-Directional Restraints

The following are some important facts pertaining to single-directional restraints:

 The sign on the single-directional restraint gives the direction of “free” movement;
that is, a +Y restraint may move freely in the positive Y direction and will be
restrained against movement in the negative Y direction.
 Single-directional restraints may define restraint along positive, negative, or skewed
axes.
 Any number of single-directional restraints may act along the same line of action. (If
more than one single directional restraint acts along the same line of action, then
there are usually two in opposite directions and they are used to model unequal leg
gaps.)
 A CNode is the connecting node. If left blank then the restrained node is connected
via the restraint stiffness to a rigid point in space. If the CNode is entered then the
restrained node is connected via the restraint stiffness to the connecting node.
 Friction and gaps may be specified with single-directional restraints.

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Volume V Supports

Guide Support

The following are some important facts pertaining to Guides in CAESAR II.

 Guides are double-acting restraints with or without a specified gap.

 Guides may be defined using the global system coordinates or with the restraint type GUI.
 A guided pipe in the horizontal or skewed direction will have a single restraint, acting in the
horizontal plane, orthogonal to the axis of the pipe.
 A guided vertical pipe will have both X and Z direction supports.
 CAESAR II computes direction cosines for guides. Guide direction cosines entered by the user
are ignored.

Guide Support for Horizontal Pipe Line

Guide with +Y Restrain Support

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Volume V Supports

Guide Support for Vertical Pipe Line

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Volume V Supports

Axial Stopper (Line Stopper)

Translational restraints may be preceded by a (+) or (-). If a sign is entered, it defines the
direction of allowed free displacement along the specified degree of freedom. (i.e. a +Y restraint is
restraint against movement in the minus –Y direction and is free to move in the plus Y direction).

Axial Stopper (Line Stopper) For Horizontal Pipe line Page | 48

Volume V Supports

Axial Stopper (Line Stopper) For Horizontal Pipe line

Limit Stops

Limit stops are used to limit the stresses in the piping and to reduce the anchor reaction. The
behavior of the limit stops is non-linear. The limit stop has zero rigidity up to certain movement. After
this predetermined movement, the limit stop comes into action. The active rigidity of the limit stop
can be finite or infinite. This depends on the construction of the limit stop.

Limit Stop for Horizontal Pipe Line

Limit stop for a similar situation in a power plant. There should not be any problem if the pipe
stresses are within limits and if the load on the stop is also reasonable. U may be providing this stop to
limit the load on some component.

The following are important facts pertaining to Limit Stops:

 Limit stops are single- or double-acting restraint whose line of action is along the axis of the
pipe.
 The sign on the single-directional restraint gives the direction of unlimited free movement.
 Limit Stops/Single Directional Restraints can have gaps. The gap is the distance of permitted
free movement along therestraining line of action.
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Volume V Supports

 A gap is a length, and is always positive. Orientation of the gap along the line of action of the
restraint is accomplished via the sign on the restraint.
 Connecting Nodes (CNode) may be used with any Limit Stop model.
 Limit Stops may be defined using the restraint type LIM.
 Limit Stops provide double or single-acting support parallel to the pipe axis. Limit Stops may
have gaps and friction.
 The positive line of action of the Limit Stop is defined by the FROM and TO node on the
element.

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Volume V Supports

Windows

Keep in mind the following facts when

modeling Windows in Caesar II.
Equal leg windows are modeled using
two double-acting restraints with gaps
orthogonal to the pipe axis.
Unequal leg windows are modeled using
four single-acting restraints with gaps
orthogonal to the pipe axis. (See the
following example.) The gap is always
positive. The sign on the restraint
determines the direction of movement
before the gap closes. If there is no sign,
then the restraint is double-acting and
the gap exists on both sides of the line of
action of the restraint. If there is a sign on
the restraint then the gap exists on the
“restrained” line of action of the restraint,
i.e. a +Y restraint is restrained against
movement in the -Y direction, and any
gap associated with a +Y restraint is the
free movement in the -Y direction before
the restraint begins acting.
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Volume V Supports

Rotational Directional Restraints with Gaps

These restraints can be considered specialty items and are typically only used in sophisticated
expansion joint or hinge models.

Single-Directional Restraint with Predefined Displacement

Define the one-directional restraint as usual, and enter a unique node number in the CNode field.
Specify the predefined displacements for the CNode.

Single-Directional Restraint and Guide with Gap and Predefined Displacement

Define the single-directional restraint and guide as usual. Put a unique node number in the CNode field
for the single directional restraint and the guide. The same unique

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Volume V Supports

Restraint Settlement

Keep in mind the following

facts when modeling restraint
settlements:
Model using a single-
directional restraint with
predefined displacements. The
magnitude of the predefined
displacement is the amount of
anticipated settlement in the
minus Y direction.
The Displacement Load Case is
used to include the effect of the
settlement (non thermal).
The settlement displacements
are prescribed for the
connecting node at the single
directional restraint. For more
information, refer to Single-
Directional Restraint with
Predefined Displacement.

Skewed Double-Acting
Restraint with Gap

The following are some

important considerations for modeling skewed restraints:

 Direction vectors or direction cosines can be used to define the line of action of the restraint. If
direction vectors are used, CAESAR II will immediately convert them to direction cosines.
 Direction cosines may be quickly checked in the graphics processor.
 Any translational axis can be used in the restraint description. The “redefinition” of the axis
does not affect any other restraint description for the element.
 Particular attention should be paid to skewed direction input data. A common mistake is to
specify an axial instead of transverse restraint when modeling a skewed guide. Plotted section
views of the restrained nodes can be an extremely useful check of the skewed direction
specification.
 The sense of the direction or cosine unit vector is unimportant. In the definition of double-
acting restraints, the direction vector and cosines are only used to define the restraint line of
action and are not concerned with a direction along that line.
 A simple rule can be used for finding perpendicular, skewed, direction vectors. The restraint is
to be perpendicular to the pipe. If the pipe has skewed delta dimensions DX and DZ, the
perpendicular restraint directions vector will be (-DZ,
 0, DX).

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Volume V Supports

Skewed Double-Acting Restraint with Gap

Skewed Single-Directional Restraint

The following are some important

considerations regarding skewed single-
directional restraints:
 Skewed restraints may be
nonlinear.
 Direction vectors or direction
cosines may be used to define the
line of action of the restraint. If
direction vectors are used
CAESAR II will immediately
convert them to direction
cosines.
 The direction of the cosines or
the direction vector is along the
positive line of action of the (+)
restraint. (See the figure for
clarification.) Page | 55
Volume V Supports

 Direction cosines may be quickly checked in the graphics processor.

 Connecting nodes (CNode) can be used with any skewed single-directional restraint.
Restraint between Two Pipes Using CNode

Nonlinear or linear restraints can act between two different pipe nodes. The Cnode effectively
represents what the "other end of the restraint" is attached to.

Restraint between Vessel and Pipe Models

The following are some important facts that pertain

to restraints’ acting between vessel and pipe:

 Use a restraint with connecting node to link

the pipe to the rigid element extending
from the vessel shell.
 Any number of restraints may be specified
between the restrained node and the
connecting node.
 Restraints may be linear or nonlinear with
gaps and/or friction.

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Volume V Supports

Restraints on a Bend at 45 Degrees

Linear and/or non-linear restraints can act at
any point on the bend curvature. Points on
the bend curvature are like any other point in
the piping system.

The following figure shows a bend supported

vertically by a rigid rod. The rod will be
allowed to take tensile loads only and so will
be modeled as a single directional restraint
that can move freely in the +Y direction. (See
the Chapter on "Bends" if the actual positions
of the nodes 19 and 20 are not clear.)

The line of action of the rod is really shifted

away from the node 19. Note that a
downward force at node 15 will produce a
positive Z moment about 20 in the system as
modeled, and a negative Z moment about the
point 20 in real life.
The magnitude of this moment is a function of
the load and the moment area (the amount of
the shift). If this is considered significant,
then a rigid element with zero weight could
be placed between node 19 and the actual
point of rod attachment. The restraint would
then be placed at the actual point of rod attachment.

Restraints on a Bend at 30 and 60 Degrees

Up to three (3) nodes can be defined at

any angle on the bend curvature so long as
the points are more than five degrees
apart. Restraints may be modeled on any
of these nodes; if necessary one of these
points can be at the zero degree point on
the bend. The zero degree point on a bend
is the bend “near” point.

The To node of the bend is placed at the

tangent intersection point for geometric
construction but is placed at the bend
"far" point for analysis purposes.
Therefore, specifying a node at the bend
far-weld point will generate an error.

Nodes and angles on the bend curvature can be specified in any order.

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Volume V Supports

Vertical Dummy Leg on Bends

Dummy legs on bends can be modeled several ways. The three most common methods used to model
dummy legs are outlined below:

Near/Far Point Method

 Easy input
 Dummy leg acts along centerline of vertical run
 Dummy leg does not act at the proper place on the bend curvature
On Curvature Method
 Easy input
 Dummy leg acts at the proper place on the bend curvature
 Dummy leg does not act along the centerline of the vertical run
 Difficult input
 Dummy leg acts at the proper place on the bend curvature
 Dummy leg acts along centerline of vertical run

The element immediately after the bend must define the downstream side of the bend. Do not define
dummy legs on the element spreadsheet immediately following the bend specification spreadsheet.

Dummy legs and/or any other elements attached to the bend curvature should be coded to the bend
tangent intersection point. The length of the dummy leg will be taken directly from the DX, DY, and DZ
fields on the dummy leg’s pipe spreadsheet. There will be no automatic alteration of the dummy leg
length due to the difference between the bend tangent intersection point and the actual point on the
bend curvature where the dummy leg acts. The true length of the dummy leg should be input in the DX,
DY, and DZ fields on the dummy leg element spreadsheet.

Input and output plots of the dummy leg always show it going to the bend tangent intersection point.

For each dummy leg/bend model a warning message is generated during error checking. The user
should verify that the warning message description of the bend is accurate.

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Volume V Supports

Horizontal Dummy Leg on Bends

The element leaving the bend must define the downstream side of the bend. Do not define dummy legs
on the element spreadsheet immediately following the bend specification spreadsheet.

The true length of the dummy leg should be input in the DX, DY, and DZ fields on the dummy leg pipe
spreadsheet.

Input and output plots of the dummy leg always show the dummy leg going to the bend tangent
intersection point.

For each dummy leg/bend model a warning message is generated during error checking. The user
should make sure that the warning message description of the dummy leg is accurate.

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Volume V Supports

Large Rotation Rods - Basic Model

Large rotation rods are used to model

relatively short rods, where large
orthogonal movement of the pipe causes
shortening of the restraint along the
original line of action.

Large rotation rods can be entered in any

direction. The user picks the XROD, YROD,
or ZROD from the type list. When CAESAR
II detects that a rod is being input, the
restraint field is changed: Gap is changed
to Len and Mu is changed to Fi. Len is the
length of large rotation swing. Fi is the
initial load on the restraint if used to model a variable support spring hanger. (See some of the later
rod examples.) The user can imagine the large rotation rod as providing a “bowl” in which the pipe
node is free to move.

Large rotation rods should only be entered where needed. Repeated use where not necessary may
cause the system to become unstable during the nonlinear iteration. The system should first be
analyzed without the large rotation rods and then large rotation rods added where horizontal
movement at support points is greatest. Usually
only one rod should be added in an area at a
time.

The rod angle tolerance is currently set at 1.0

degree.

Large rotation is generally considered to

become significant when the angle of swing
becomes greater than 5 degrees.

Connecting nodes may be used for large rotation

rods just like for any other support. Graphically,
the connecting nodes and the restraint node do
not have to be at the same point in space. There
is no plot connectivity forced between large
rotation rod nodes and connecting nodes.

The signs on the large rotation rod are

significant and determine the orientation of the
swing axis. A +YROD is equivalent
to an YROD and indicates that the concave side
of the curvature is in the positive Y direction.

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Volume V Supports

Large Rotation Rods - Chain Supports

In the model below, the user wants the large

rotation swing only in the plane of the chin
support (the X-Y plane). The two
pipes should move freely relative to each other
in the axial direction (the X-Y plane). Three
restraints with connecting
nodes are used. The first is the large rotation rod
with its connecting nodes, which in turn is
connected to the second and
third linear restraints that allow only Y-Z
interaction between the large rotation rod
connecting node and the top pipe node.

Bi-Linear Restraints

Bi-linear restraints have the digit 2 following the direction in the restraint TYPE field.

When a bi-linear spring is entered the restraint fields change as follows: Stif changes to K1, which is
the Initial Stiffness, Gap changes to K2, which is the Yield Stiffness, and Mu changes to Fy, which is the
Yield Load.

Bi-linear restraints are used most often to model soil support where some soil ultimate load bearing
capacity can be calculated.

Both the yield stiffness (K2) and the yield load (Fy) are required entries. The initial stiffness (K1) may
be left blank, and a rigid initial stiffness assumed. The yield stiffness may be negative if necessary.
Some subsea pipeline resistance tests have shown that load carrying capacity drops after the
“ultimate” load is reached, and displacement continues.

More detailed use of the spring

types used to model underground
piping systems is illustrated in
the CAESAR II User Guide -
Underground Pipe Modeler

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Allowable Support Spans

The allowable support span is defined as the maximum permitted unsupported span between
any two adjacent supports on a horizontal straight piping. The loads on the piping induce direct stress
(axial tension or compression), bending stress, torsion-stress, shear stress and linear and angular
deformation. The torsion-stress, shear stress and angular deformation are not usually limited.
Popular piping codes limit the bending stress of steel pipes to 15,850 KPa (2,300 psi) and the linear
deformation to 2.54 mm (0.1 inch). The suggested pipe support span for commonly used steel piping
is given in the following Table.

Table – Suggested Pipe Support Span

NPS – inch Water Service Steam, gas or air service m

(DN – mm) m (ft) (ft)
1 (25) 2.13 (7) 2.74 (9)
2 (50) 3.05 (10) 3.96 (13)
3 (75) 3.66 (12) 4.57 (15)
4 (100) 4.27 (14) 5.18 (17)
6 (150) 5.18 (17) 6.40 (21)
8 (200) 5.79 (19) 7.32 (24)
12 (300) 7.01 (23) 9.14 (30)
16 (400) 8.23 (27) 10.70 (35)
20 (500) 9.14 (30) 11.90 (39)
24 (600) 9.75 (32) 12.80 (42)

For the vertical runs of the pipes, a support span of four times that allowed for horizontal runs
can be permitted. It is preferable to avoid providing supports on the pipes inclined in the vertical
plane. It is preferable to provide a support at each location of direction change of the pipe.

Support Thick Calculation

The thickness required to take care of the axial tension due to heavy vertical load is given in Equation-
1

Do 1  p Do2 + 4 W
T = ------ 1 
2  Do2 (p + f)

Where
T = minimum required thickness, mm
Do = outside diameter of the pipe, mm
p = maximum allowable working pressure, MPa(g)
W = axial load, N
f = maximum allowable stress in tension, MPa

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Volume VII Spring Hanger

Volume VI Spring Hangers

Hangers

Hangers are special types of ties. They are always vertical and carry tensile loads.

Rigid Support and Flexible Support

The supports may be rigid or flexible in construction. Flexible supports are used where loads are to be
carried, at the same time, accommodate movement. The movements may be due to the thermal
expansion of the piping or connected equipment movements. The load variation in the variable load
hanger from cold to hot is usually limited to 25%.

Variable Load Hanger (VLH)

Variable load hanger is a special type of hanger, which accommodate the vertical thermal movements,
while carrying the vertical load. Usually variable load hangers are made of helical springs. The load
varies from cold condition to hot condition.

Constant Load Hanger (CLH)

Constant load hanger is a special type of hanger, similar to the variable load hanger. There are several
types of constant load hangers. The load variation in the constant load hanger from cold to hot is
usually limited to 0%.

Variable Spring Hanger

 Top supported Spring Hanger
 Bottom Supported Spring Hanger

Constant Spring Hanger

 Top supported Spring Hanger
 Bottom Supported Spring Hanger

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Volume VII Spring Hanger

Variable Spring Hanger

A variable spring hanger supports a hung pipe from

above, Figure . A variable spring support is placed below
the pipe and supports the pipe from underneath. Variable
spring hangers, Figure 6-3, are standard supports, used to
support the pipe's deadweight while allowing vertical
movement due to expansion or contraction. The reaction
force on a spring hanger varies as the pipe moves
vertically, which makes it best suited where vertical
expansion and contraction movements are not too large,
causing the force in the spring not to vary by more than
25% from cold to hot position.

As the pipe moves horizontally, the spring will swing. A

limit of the swing angle is typically specified in the
vendor catalog. The spring is selected based on its weight
carrying capability and its cold-to-hot travel range. For
piping systems operating at temperature, it is advisable
to verify, once the line is placed in service, that the
calculated movements at the springs do correspond to
the observed movements, and that the support contracts
and expands within its travel range.
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Volume VII Spring Hanger

Piping systems solely supported by spring hangers or rod hangers are flexible and are therefore
vulnerable to large displacements under vibration or fluid transients.

To illustrate the sizing process for a spring hanger, consider Figure, with a load during hot operation
FH = 1000 Ib and an ambient to hot movement DH = 0.5" upward. Using the vendor catalog, we select a
spring with a hot load of 1000 Ib at about midpoint of the spring operating range. For example, in our
case, the vendor catalog indicates that there is a spring, Type "ABC", with 1000 Ib capacity close to mid
travel range. The catalog also indicates a total spring travel range of 2.5” and a spring stiffness of 300
Ib/in.
Next, as a matter of good practice, we check that the "spring variability" is less than 25%, where the
variability is defined as

V=100(DH K/F H )
V = variability, %
DH = pipe movement from ambient to hot condition, in
K = spring stiffness, Ib/in
FH = load in the hot operating condition, Ib

In our example V = 100 (0.5 x 300 / 1000) = 15%, which is less than 25%. When the pipe cools down
from hot operating to ambient condition, the pipe will move downward by an amount -DH,
compressing the spring, and the cold load will be FH + K DH or, in our case, 1000 + (300 x 0.5) = 1150
Ib. At 1150 Ib, the vendor catalog indicates that spring type "ABC" will be 1" below its zero, no load,
top position, well within its total travel allowance of 2.5".

Constant Load Hanger

A constant load hanger supports a hung pipe from

above, Figure. A constant load support is placed below
the pipe and supports the pipe from underneath. Like
a variable spring, the constant load hanger, Figure, is
used to support the pipe's deadweight while allowing
vertical movement due to expansion or contraction.
Unlike a variable spring, the constant load hanger
maintains a nearly constant upward load on the pipe
as the pipe moves up or down, over a certain range.
Constant load hangers are used where the pipe will
undergo large vertical movements from thermal
expansion, where a variable spring may have seen
load variations in excess of 25%. Limits on swing
angle and travel range are similar to variable springs.

The constant spring assembly is usually larger and

heavier than a variable spring, and is used primarily
where the pipe cold-to-hot vertical travel is too large
to be accommodated by a variable spring. For piping
systems operating at temperature, it is advisable to
verify, once the line is placed in service, that the
calculated movements at the hangers do correspond
to the observed movements, and that the support
operates in its design range.
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Volume VII Spring Hanger

Ten Dos the following leads to a good engineering practice

1. Use minimum number of supports

2. Limit the use of flexible supports
3. Provide supports near the already provided columns and beams
4. Provide necessary clearance for thermal movement
5. Consider all the primary, secondary and occasional loads in the design
6. Provide access for valves and fittings
7. Provide additional loops to satisfy flexibility requirements
8. Provide guides to resist occasional loads like wind and earthquake
9. Provide an ergonomically acceptable design
10. Provide supports for vents, drains, start-up vents and silencers

Ten Don’ts avoid the following in design

1. Avoid too many anchors

2. Avoid too long a span
3. Avoid too thin a pipe
4. Avoid large local stresses
5. Avoid too many fittings
6. Avoid too many flexible supports
7. Avoid supports on horizontal bends
8. Avoid supports on pipes inclined to the vertical
9. Avoid bunching of too many pipes
10. Avoid large vertical or horizontal loops

VARIABLE LOAD HANGERS – SELECTION & SETTING PROCEDURE FOR BOILER AND PIPING
APPLICATIONS

Scope

This procedure deals with the selection and setting of the variable load hangers (VLH) for
boiler (pressure parts and non-pressure parts) and piping applications from the presently available
list of VLH being manufactured his may be used for pressure vessels and heat exchangers also.

General

The description, range and type of VLH are described in the write-up on "VARIABLE SPRING
HANGERS". The details like selection procedure, shop and site setting information’s are described
herein.

Selection:

Before selecting a particular VLH, the designer is advised to acquaint himself/herself with the
various aspects of the VLH by perusing the write-up on "VARIABLE SPRING HANGERS".

The terminology used in the selection of VLH is indicated in Figure

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Volume VII Spring Hanger

SPRING SPRING LOAD – COMPRESSION

WITH NO LOAD WITH LOAD DIAGARAM
(Fully Compressed)

Figure

A - Pre-compression (initial compression) F - Total possible compression

B - Additional compression in cold G - Additional compression in hot condition
condition H - Free height
C - Vertical thermal movement of J - Fully compressed height
connected equipment (cold to hot – either P - Maximum load carrying capacity of
downward or upward) = Y spring-corresponding to a compression of
D - Working range of the VLH 'F'.
E - Unused range of compression

Note Figure-1 describes the terminology used in VLH for an application where the vertical
thermal movement of the connected equipment is downward (cold to hot). When the vertical
movement from COLD to HOT is upwards, the marks 'COLD POSITION' and 'HOT POSITION' indicated
in Figure-1 should be mutually interchanged and following changes in terminology should be effected.

B – Additional compression in hot condition.

G – Additional compression in cold condition.

Some of the dimensions are constants for all the load groups. They are indicated in Table-1.

TABLE – 1

Sl.No. Dimension Unit TRAVEL RANGE=80 TRAVEL RANGE=160

mm mm
01. A mm 56 112
02. D mm 80 160
03. E mm 24 48
04. F mm 160 320

All other dimensions (B, C & G) are application – specific and are to be calculated for each VLH.
EXAMPLE:

Design load (Hot load) W = 5400 Kg Page | 68

Volume VII Spring Hanger

Vertical thermal movement (Cold to Hot) y = 40 mm (downward)

(y = c)
(When y is less than 1.6 mm, a rigid rod without springs may be used)
Try load group '12' and travel range 80 mm.
Spring rate (spring stiffness) K = 62.50 Kg/mm
Load variation from hot to cold W = K x y
= 62.5 x 40 = 2500 Kg

W 2500
% load variation = -------- x 100 = --------- x 100 = 46%
W 5400
% allowable load variation is 25%, as the actual load variation (46%) is more than the allowable load
variation (25%), this selection is not acceptable. (Please note that the allowable load variation is taken
as 25% based on ASME-B 31.1, 1992 recommendations. Some customers / consultants specify a lower
value of % W, in which case the latter is governing. The tender specifies an allowable load variation
of 6% of the cold load).

Try load group '12' and Travel Range '160 mm'.

Spring rate K = 31.25 Kg/mm
Ky v 31.25 x 40 x 100
% load variation = -------- x 100 = ------------------------ = 23% <25%
W 5400 OKAY

Please note that a VLH with a travel range of 160 mm is more expensive than a VLH with a
travel range of 80 mm, for the same load group.
If the % load variation for a VLH is more than 25%, use VLH with lower spring rate. If such a
VLH is not available, use a constant load hanger (CLH) – spring loaded or dead weight loaded.

SETTING

The following information’s are required by the shop / site, over and above the size and type of
the VLH, for setting and monitoring the VLH during operation.

1, Vertical thermal movement of the equipment (cold to hot) = y (upward or downward) = c.

2. Additional compression in cold condition (B or G).

The setting details for the VLH, selected in the aforesaid example are given below:
c = y = 40 mm (downward).

W 5400
Total compression in hot condition = ----- = ----------
K 31.25

1 = 172.8 mm

Total compression in cold condition = 1 - y

= 172.8 – 40
2 = 132.8 mm

Additional compression in cold condition = 2 – A Page | 69

Volume VII Spring Hanger

= 132.8 – 112
= 20.8 mm = B

Additional compression in hot condition =G=B+C

= 20.8 + 40 = 60.8 mm
Please note that the values of B&G should not be outside the range of 0 – 80 mm and 0 – 160
mm for VLH with travel ranges: 80 mm and 160 mm respectively. This aspect should be checked for
every VLH.

When y = 40 mm (upward)

W 5400
1 = ----- = ------------ = 172.8 mm
K 31.25

2 = 1 - y = 172.8 + 40 = 212.8 mm

G = 2 – A = 212.8 – 112 = 100.8 mm

B = G – y = 100.8 – 40 = 60.8 mm

The values of additional compression in cold condition (B or G) and vertical thermal movement
from cold to hot (y = c) are to be communicated to shop / site.

If the Available Space is not an

important design criterion, then the
field should be left blank or zero.
If the Available Space is positive, then
the vertical clearance will be assumed to
be above the pipe and a hanger will be
designed. If the Available Space is
negative, then the vertical clearance will
be assumed to be below the pipe and a
can will be designed.
When the Available Space is the
governing factor in a hanger design,
several smaller springs are typically
chosen in place of one large spring.

Allowable Load Variation (%)

This is the user specified limit on the

allowed variation between the hot and
cold hanger loads. If not specified, the
only limit on load variation is that
inherent in the spring table. This is
approximately 100% when the hot load
is smaller than the cold load, and 50%
when the hot load is larger than the cold
load. Hot loads are smaller than cold loads whenever the operating Page | 70
displacement in the Y direction is positive. The default value for the load variation is 25%. The user is
Volume VII Spring Hanger

advised to enter this value in the Hanger Run Control Spreadsheet before any hangers are defined.
Bergen-Paterson is the only manufacturer that specifically gives 25% as a design limit.

The Allowable Load Variation is the percentage variation from the hot load:

For example

Hot load = 2392 kg

Travel = 15mm
Referring to short from selection chart. 2393kgs = size15
Assume VS-1 = 15 X 38.6 X 100
= 2392
= 24.2%

The Allowable Variation is entered as a percentage, i.e. twenty five percent would be entered 25.0. The
Allowable Load Variation can have different values for different hanger locations if necessary by
entering the chosen value on the individual hanger spreadsheets or it can be entered on the Hanger
Design Control Spreadsheet to apply to all hangers in the model.

Rigid Support Displacement Criteria (UNITS: mm.)

This is a parameter used to determine if there is sufficient travel to design a spring. The Rigid Support
Displacement Criteria is a cost saving feature that replaces springs that are not needed with rigid rods.

The hanger design algorithm operates by first running a restrained weight case. From this case the
load to be supported by the hanger in the operating condition is determined. Once the hanger design
load is known, an operating case is run with the hot hanger load installed to determine the travel at the
hanger location. If this determined hanger travel is less than the Rigid Support Displacement Criteria
then a rigid Y support is selected for the location instead of a spring.

If the Rigid Support Displacement is left blank or zero, the criteria will not be applied.
The Rigid Support Displacement Criteria may be specified on the Hanger Run Control Spreadsheet, or
on each individual hanger spreadsheet. The value specified on the Hanger Run Control Spreadsheet is
used as the default for all hangers not having it defined explicitly.
A typical value to be used is 0.1 in.

Maximum Allowed Travel Limit (UNITS: mm.)

To specify a limit on the amount of travel a variable support hanger may undergo, specify the limit in
this field. The specification of a maximum travel limit will cause CAESAR II to select a constant effort
support if the design operating travel exceeds this limit, even though a variable support from the
manufacturer table would have been satisfactory in every other respect.
Constant effort hangers can be designed by inputting a very small number for the Maximum Allowed
Travel Limit. A value of 0.001 is typical to force CAESAR II to select a for a particular location.

No. Hangers at Location

If left blank, CAESAR II will attempt to find a single hanger that suits all design requirements at the
location. If a single hanger cannot be found, then CAESAR II will try to find a double hanger that
satisfies all design requirements. If a double hanger cannot be found, then CAESAR II will recommend
a constant effort support hanger for the location.
If the user wants to use a different upper limit on the number of springs that CAESAR II will consider
Page | 71
for a location, then the negative of that number should be entered in this field. For example, if the user
Volume VII Spring Hanger

wants to use as few springs as possible, yet is willing to use as many as 5 springs if necessary, -5
should be entered in the No. of Hangers field.
To directly specify the number of springs to be designed at a location, enter that number in the No. of
Hangers field.

Allow Short Range Springs

CAESAR II gives the user the option of excluding short range springs from consideration from the
selection algorithms. In some instances short range springs are considered specialty items and are not
used unless their shorter length is required for clearance reasons. In this case, this check box should be
cleared by the user.
If this option is not activated, CAESAR II will select a mid-range spring over a short-range spring,
assuming they are more standard, readily available, and in general cheaper than their short-range
counterparts.
If the default should be that short range springs are used wherever possible, then check the box on the
Hanger Design Control Spreadsheet.

Operating Load (UNITS: N.)

To override the operating load that CAESAR II is calculating, enter the desired value in the Operating
Load field. This value is normally entered when the user thinks that loads on a piece of equipment will
be reduced if a hanger in the vicinity of the equipment is artificially caused to carry a proportionately
larger part of the total load. This operating load is the hot load the hanger is designed to support after
it undergoes any travel due to the thermal expansion of the piping. CAESAR II's calculated hanger
operating loads may be read from the hanger table printed in the output processor. The column title is
"HOT LOAD." The user's entered value will similarly show up in this table if defined. The total desired
operating load at the location should be entered. If there are two hangers specified at the location and
each should carry 500 lb., then the operating load specified should be 1,000 lb.

Multiple Load Case Design

The spring selection algorithm can be based on one or more operating conditions. A two-pump
installation, where only one pump operates at a time, is a good application for multiple load case
hanger design.
There are currently thirteen different multiple load case design algorithms available:
Design spring per operating case #1.
Design spring per operating case #2.
Design spring per operating case #3, #4, #5, #6, #7, #8, and #9.
Design spring for maximum operating load.
Design spring for maximum travel.
Design spring for average load and average travel.
Design spring for maximum load and maximum travel.
The Multiple Load Case Design option can be specified at the global level in the Hanger Design Control
Data Spreadsheet. The globally specified option will apply for all hanger design locations unless
overridden in a specific hanger design spreadsheet.
Enter the number of operating thermal cases to be considered when sizing springs for this system in
the Hanger Design Control Spreadsheet. This value defaults to 1.0. Also enter the Multiple Load Case
Design option to be the default value (unless the design option is to be specified individually for each
hanger to be designed in the system).

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Volume VII Nozzle Analysing

Volume VII Nozzle Analysing

Flexible Nozzles

This auxiliary screen is used to describe

flexible nozzle connections. When entered in
this way, CAESAR II automatically calculates
the flexibilities and inserts them at this
location. CAESAR II calculates nozzle loads
according to WRC 297, API 650 or BS 5500
criteria. When a nozzle node number is input, CAESAR II scans the current input data for the node and
loads its diameter and wall thickness and enters it in the Nozzle Auxiliary Data field. Current nozzle
flexibility calculations are in accordance with the Welding Research Council Bulletin No. 297, issued
August 1984 for cylinder to cylinder intersections.

A valid nozzle node has the following properties:

 Only a single element connects to the nozzle node.

 The nozzle node is not restrained and does not have displacements specified for any of its
degrees of freedom.

Computed nozzle flexibilities are automatically included in the piping system analysis via
program generated restraints. This generation is completely transparent to the user. Six restraints are
established for each flexible nozzle input. If a vessel node number is defined, then the vessel node acts
like a connecting node for each of the six restraints. Vessel nodes are subject to the same restrictions
shown above for nozzle nodes.

Note: The user should not put a restrainer on an element between the nozzle node and any
specified vessel node. CAESAR II creates the required connectivity from the nozzle flexibility data and
any user generated stiffnesses between these two points will add erroneously to the nozzle stiffnesses.

Welding Research Council (WRC-297)

WRC-297 can be applied to a larger d/D ratio (up to 0.5) since the analysis is based on a
different, thin shell theory (derived and developed by Prof. C. R. Steele).

Flexible Nozzle - WRC Bulletin 297

 Adhere to these requirements when modeling flexible nozzles

 Frame only one pipe element into the nozzle node.
 Do not place restraints at the nozzle node.
 Do not place anchors at the nozzle node.
 Do not specify displacements for the nozzle node. (See the following example for
displacements at flexible nozzles.)

CAESAR II automatically performs the following functions

 Calculates nozzle flexibilities for the nozzle/vessel data entered by the user
 Calculates and inserts restraints to simulate nozzle flexibilities
 Calculates flexibilities for the axial translations, circumferential, and longitudinal bending
 Users must perform the error check process to view these calculated values. Page | 73
Volume VII Nozzle Analysing

CAESAR II uses the following criteria for its calculations

 Shear and torsional stiffnesses are assumed rigid.

 Nozzle configurations outside of the WRC 297 curve limits are considered rigid. It is not
unusual for one stiffness value to be rigid because of curve limits, and the others to be suitably
flexible.
 The Vessel Temperature and Material fields on the WRC 297 auxiliary data area may be used to
optionally compute a reduced modulus of elasticity for the local stiffness calculations.

Nozzle Node Number

Node that is located at the nozzle's intersection with the vessel shell. There should only be a single
piping element connected to this node, and there should be no restraints acting on the node. The
nozzle element should be perpendicular to the vessel shell. Hillside nozzles and latrolets can still be
modeled; however, the first (possibly very short) nozzle element that comes from the vessel should be
Page | 74
Volume VII Nozzle Analysing

perpendicular to the vessel to keep the local stiffness properly oriented. The second, longer nozzle
element can then go off on the true centerline of the nozzle.

Vessel Node Number (Optional)

Node on the vessel/tank surface at the
point where the nozzle intersects the vessel
shell. The vessel/tank node is optional, and if not
given the nozzle node is connected via the
stiffnesses to a point fixed rigidly in space. If the
vessel node is given, the nozzle node will be
connected via the stiffnesses to the vessel node.
Vessel nodes are specified when the user wishes
to model through the vessel from the nozzle
connection to the skirt or foundation. 3-54
Piping Screen Reference

Nozzle Diameter
Outside diameter of the nozzle. (Does not
have to be equal to the diameter of the pipe used
to model the nozzle.)

Nozzle Wall Thickness

Wall thickness of the nozzle. (Does not
have to be equal to the wall thickness of the pipe
element used to model the nozzle.)

Vessel Diameter
Outside diameter of the vessel.

Vessel Wall Thickness

Wall thickness of the vessel at the point
where the nozzle connects to the vessel. Do not include the thickness of any reinforcing pad.

Vessel Reinforcing Pad Thickness

Thickness of any reinforcing pad at the nozzle. This thickness is added to the vessel wall
thickness before nozzle stiffness calculations are performed.

Distance to Stiffener or Head

Distance along the vessel center-line, from the center of the nozzle opening in the vessel shell
to the closest stiffener or head in the vessel that significantly stiffens the cross-section of the vessel
against local deformation normal to the shell surface.

Distance to Opposite-Side Stiffener or Head

Distance from the center of the nozzle opening in the vessel shell to the closest stiffener or
head in the vessel on the other side of the nozzle. This entry is ignored for spherical vessels.

Vessel centerline direction vector X, Y, Z

Direction vector or direction cosines which define the center-line of the vessel. For a vertical
vessel this entry would read:

Vessel centerline direction vector X:<blank>

Page | 75
Vessel centerline direction vector Y: 1.0
Volume VII Nozzle Analysing

Vessel centerline direction vector Z:<blank>

Note: The centerlines of the nozzle and vessel cannot be collinear or CAESAR II will flag this as an
error.
Horizontal Vessels

Horizontal Vessel models are built using combinations of straight pipe and nozzle flexibility
simulations (WRC 297). The following figure illustrates the most accurate way to define horizontal
vessel flexibility.

Page | 76
Volume VII Nozzle Analysing

API 650 NOZZLES

Activate by double-clicking the Nozzles

check box on the Pipe Element Spreadsheet and
selecting the API 650 radio button from the
Nozzle Auxiliary Data field. Deactivate by
double-clicking the check box a second time.

CAESAR II can also calculate nozzle flexibilities according to appendix P of API 650, "Design of Carbon
Steel Atmospheric Oil Storage Tanks."

Nozzle Node Number

Node that is located at the nozzle's
intersection with the vessel shell. There
should only be a single piping element
connected to this node, and there should be
no restraints acting on the node. The nozzle
element should be perpendicular to the
vessel shell. Hillside nozzles and latrolets can
still be modeled; however, the first (possibly
very short) nozzle element that comes from
the vessel should be perpendicular to the
vessel to keep the local stiffness properly
oriented. The second, longer nozzle element
can then go off on the true centerline of the
nozzle.

Tank Node Number

Node on the tank surface at the point
where the nozzle intersects the vessel/tank
shell. The tank node is optional, and if not
given the nozzle node is connected via the
API stiffnesses to a point fixed rigidly in
space. If the tank node is given, the nozzle
node will be connected via the API stiffnesses
to the tank node. Tank nodes are specified
when the user wishes to model through the
tank from the nozzle connection to the
foundation.
Nozzle Diameter
Outside diameter of the nozzle. (Does not have to be equal to the diameter of the pipe used to
model the nozzle.)

Nozzle Wall Thickness

Wall Thickness of the nozzle. May be different than the attached pipe wall thickness

API-650 Tank Diameter

Outside Diameter of the Vessel or API 650 storage tank. Note that API 650 Addendum 1 does
not recommend these computations for diameters less than 120 feet.

Page | 77
Volume VII Nozzle Analysing

API-650 Tank Wall Thickness

Wall Thickness of the Vessel at the point where the Nozzle connects to the vessel. DO NOT
include the thickness of any
reinforcing pad.

API 650 Reinforcing 1 or 2

For API tanks, if the reinforcing is on the shell, then enter 1. If it is on the nozzle, enter a 2.

API 650 Nozzle Height

For API 650 applications, enter the height from the centerline of the nozzle to the base of the
tank.

API 650 Fluid Height

Enter the liquid level of the fluid in the storage tank. This fluid level must be greater than the
nozzle height.

API 650 Specific Gravity

Enter the specific gravity of the stored liquid. This value is unit less. API-650 Tank Coefficient
of Thermal Expansion Enter the coefficient of thermal expansion of the plate material of the tank is
constructed. Values are listed in engineering handbooks or the appropriate section of the API 650, App
P. If this value is left blank, zero will be assumed.

API 650 Delta T

Enter the change in temperature from ambient to its maximum that the tank normally
experiences. For example: If the maximum summertime temperature is 107°F. The delta T would be
107 - 70 = 37°F. If this value is left blank, zero will be
assumed.
API-650 Tank Modulus of Elasticity
For API 650 nozzles, the hot modulus of elasticity of the tank must be entered directly. If this
value is left blank, 29.5E6 will be assumed.

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Volume VII Nozzle Analysing

PD 5500 Nozzles

Activate by double-clicking the Nozzles check box

on the Pipe Element Spreadsheet and selecting the PD
5500 radio button from the Nozzle Auxiliary Data field.
Deactivate by double-clicking the check box a second time.
CAESAR II can also calculate nozzle flexibilities according to Appendix G of the PD 5500
Specification for Unfired Fusion Welded Pressure Vessels. The input requirements for these nozzles
are:

Nozzle Node Number

Node that is located at the nozzle's
intersection with the vessel shell. There should
only be a single piping element connected to
this node, and there should be no restraints
acting on the node. The nozzle element should
be perpendicular to the vessel shell. Hillside
nozzles and latrolets can still be modeled;
however, the first (possibly very short) nozzle
element that comes from the vessel should be
perpendicular to the vessel to keep the local
stiffness properly oriented. The second, longer
nozzle element can then go off on the true
centerline of the nozzle.

Vessel Node Number (Optional)

Node on the vessel/tank surface at the
point where the nozzle intersects the vessel
shell. The vessel/tank node is optional, and if
not given the nozzle node is connected via the
stiffnesses to a point fixed rigidly in space. If
the vessel node is given, the nozzle node will
be connected via the stiffnesses to the vessel
node. Vessel nodes are specified when the user
wishes to model through the vessel from the
nozzle connection to the skirt or foundation.

Vessel Type - Cylinder (0) or Sphere (1)

If the vessel is cylindrical, enter a 0.
For cylinders, the distances to stiffeners/heads and the vessel direction cosines are required. If the
vessel is spherical, enter a 1. For spheres, the fields for the distances to stiffeners/heads and vessel
direction cosines are both ignored.

Nozzle Diameter
Outside diameter of the nozzle. (Does not have to be equal to the diameter of the pipe used to
model the nozzle.)

Vessel Diameter
Outside diameter of the vessel.

Vessel Wall Thickness

Wall thickness of the vessel at the point where the nozzle connects to the vessel. Do not include
Page | 79
the thickness of any reinforcing pad.
Volume VII Nozzle Analysing

Vessel Reinforcing Pad Thickness

Thickness of any reinforcing pad at the nozzle this thickness is added to the vessel wall
thickness before nozzle stiffness calculations are performed.

Distance to Stiffener or Head

Distance along the vessel center-line, from the center of the nozzle opening in the vessel shell
to the closest stiffener or head in the vessel that significantly stiffens the cross-section of the vessel
against local deformation normal to the shell surface.

Distance to Opposite-Side Stiffener or Head

Distance from the center of the nozzle opening in the vessel shell to the closest stiffener or head in the
vessel on the other side of the nozzle. This entry is ignored for spherical vessels.

Vessel Centerline Direction Cosines

These are direction vectors or direction cosines that define the center-line of the vessel. For a
horizontal vessel aligned with the “X” axis, this entry would read:

Vessel centerline direction vector X ..... 1.0

Vessel centerline direction vector Y ..... <Blank>
Vessel centerline direction vector Z ..... <Blank>

Note: The centerlines of the nozzle and vessel cannot be co-linear or CAESAR II will flag this as an
error. This entry is ignored for spherical vessels.

Displacements
Activate by double-clicking the Displacements check box on the Pipe Element Spreadsheet.
Deactivate by double clicking the Displacements check box a second time.

This auxiliary screen is used to enter

imposed displacements for up to two nodes
per spreadsheet. Up to nine displacement
vectors may be entered (load components D1
through D9). If a displacement value is
entered for any vector, this direction is
considered to be fixed for any other non-
specified vectors.
Note Leaving a direction blank for all
nine vectors models the system as being
free to move in that direction. Specifying
“0.0” implies that the system is fully
restrained in that direction.

 Enter the node number where the

displacement is to be specified.
There must not be a restraint at this
node.
 Enter the displacements at the node. Any displacement direction not specified for any
displacement vector will be free.
 To specify an anchor at Node 50 with a displacement of 0.25 in. in the +X , 0.10 in. in the +Y ,
and 0.08 in. in the –Z , for displacement vector #1, enter data as shown in the Figure above.
Page | 80
Volume VII Nozzle Analysing

 The displacements at a node can be specified for up to 9 different vectors, intended to

correspond to the 9 temperature cases.

Note: If an imposed displacement is specified for a specific degree-of-freedom, that degree-of-freedom

will be considered restrained for all load cases whether or not they contain that displacement set.

Forces & Movements

Activate by double-clicking the Forces/Moments check box on the Pipe Element Spreadsheet.
Deactivate by double clicking the check box a second time.

This auxiliary screen is used to enter imposed forces and/or moments for up to two nodes per
spreadsheet. Up to nine force vectors may be entered (load components F1 through F9).

Uniform Loads

Activate by double-clicking the Uniform Loads check box on the Pipe Element Spreadsheet.
Deactivate by double clicking the check box a second time.

This auxiliary screen is used to enter up

to three uniform load vectors (load components
U1, U2 and U3). These uniform loads are
applied to the entire current element, as well as
all subsequent elements in the model, until
explicitly changed or zeroed out with a later
entry.

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Volume VII Nozzle Analysing

Wind/Wave

This auxiliary screen is used to specify

whether this portion of the pipe is exposed to
wind or wave loading. (Note that the pipe may
not be exposed to both.) Selecting Wind
exposes the pipe to wind loading; selecting
Wave exposes the pipe to wave, current, and
buoyancy loadings; selecting Off turns off both
types of loading. This screen is also used to
enter the Wind Shape Factor (when Wind is
specified) and various wave coefficients (if left
blank they will be program-computed) when
Wave Loading is specified. Entries on this
auxiliary screen apply to all subsequent piping,
until changed on a later spreadsheet.

Note Specific wind and wave load cases are built using the Static Load Case Editor.

There are three different methods that can be used to generate wind loads on piping systems:

 ASCE #7 Standard Edition, 1995

 User entry of a pressure vs. elevation table
 User entry of a velocity vs. elevation table

The appropriate method is selected by placing a value of 1.0 in one of the first three
boxes.When defining a pressure or velocity vs. elevation table the user needs to specify only the
method and the wind direction on the preceding screen. Upon pressing the User Wind Profile button,
the user is prompted for the corresponding pressure or velocity table. If a uniform pressure or velocity
is to act over the entire piping system, then only a single entry needs to be made in the table, otherwise
the user should enter the pressure or velocity profile for the applicable wind loading.

Note To use the ASCE #7 wind loads, all of the fields should be filled in.

For example, as per ASCE #7, the following are typical basic wind-speed values:
California and West Coast Areas- 124.6 ft. /sec. ( 85 m.p.h.)
Rocky Mountains- 132.0 ft. /sec ( 90 m.p.h.)
Great Plains- 132.0 ft ./sec ( 90 m.p.h.)
Non-Coastal Eastern United States- 132.0 ft./sec ( 90 m.p.h.)
Gulf Coast- 190.6 ft. /sec (130 m.p.h.)
Florida-Carolinas- 190.6 ft./sec (130 m.p.h.)
Miami- 212.6 ft. /sec (145 m.p.h.)
New England Coastal Areas- 176.0 ft. /sec (120 m.p.h.)

Page | 82
Volume VII Nozzle Analysing

Wave Load

Drag Coefficient, Cd
Coefficient as recommended by API RP2A.
Typical values range from 0.6 to 1.20. Entering a 0.0
instructs CAESAR II to calculate the drag coefficient
based on particle velocities.

Added Mass Coefficient, Ca

This coefficient accounts for the added mass of
fluid entrained into the pipe. Typical values range from
0.5 to 1.0. Entering a 0.0 instructs CAESAR II to
calculate the added mass coefficient based on particle
velocities.

Lift Coefficient, Cl
This coefficient accounts for wave lift, which is
the force perpendicular to both the element axis and
the particle velocity vector. Entering a 0.0 instructs
CAESAR II to calculate the added lift coefficient based
on particle velocities.

Marine Growth
The thickness of any marine growth adhering
to the external pipe wall. This will increase the pipe diameter experiencing wave loading by twice this
value.

Marine Growth Density

An entry in this field designates the density to be used if including the weight of the marine
growth in the pipe weight. If left blank, the weight of the marine growth will be ignored.

Off
This selection turns off both wind and / or wave loads from this point forward in the model.

Up to four different hydrodynamic load cases may be specified for any one job. Several
hydrodynamic coefficients are defined on the element spreadsheet. The inclusion of hydrodynamic
coefficients causes the loads WAV1, WAV2, WAV3, and WAV4 to be available in the load case editor.

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Volume VII Nozzle Analysing

A CAESAR II Hydrodynamic Loading dialog is shown in the following figure. In the load case
editor, four different wave load profiles can be specified. Current data and wave data may be specified
and included together or either of them may be omitted so as to exclude the data from the analysis.
CAESAR II supports three current models and six wave models. See the CAESAR II Technical Reference
Manual for a detailed discussion of hydrodynamic analysis.

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Volume VIII Analysing

Volume VIII Analysing

STRESS CATEGORIES

The major stress categories are

 Primary
 Secondary
 Peak

PRIMARY STRESSES
These are developed by the imposed loading and are necessary to satisfy the equilibrium between
external and internal forces and moments of the piping system. Primary stresses are not self-limiting.

SECONDARY STRESSES
These are developed by the constraint of displacements of a structure. These displacements can be
caused either by thermal expansion or by outwardly imposed restraint and anchor point movements.
Secondary stresses are self-limiting.

PEAK STRESSES
Unlike loading condition of secondary stress which causes distortion, peak stresses cause no
significant distortion. Peak stresses are the highest stresses in the region under consideration and are
responsible for causing fatigue failure.

CLASSCIFICATION OF LOADS

Primary loads
These can be divided into two categories based on the duration of loading.
Sustained loads
These loads are expected to be present throughout the plant operation. e,g. pressure and weight.
Expansion loads
These are loads due to displacements of piping. e,g .thermal expansion, seismic anchor movements,
and building settlement.
Occasional loads
These loads are present at infrequent intervals during plant operation. e,g. earthquake, wind, etc.

What is flexibility?

Flexibility is also a crucial factor in piping system. Train rails illustrate the principle of piping
flexibility. Think that the rail ends are squarely fitting, without any gap. When the ambient
temperature rises, the rails expand. The expansion creates a high force, which can push the joints out
of alignment. That is dangerous for the train.
That is why we have a small gap between two rails. The rails expand into the gap. No force, no
misalignment and all safe. Similarly, pipes are installed during relatively cooler conditions. When a hot
fluid passes in the pipe, or when the ambient temperature rises, the pipe expands. The expansion
generates enormous force. If only one end of the pipe were connected, the other, loose, end can
expand. But generally, in piping both ends are connected. The expansion force acts on equipment or a
structure or whatever the pipe is connected to. If it is flexible, the piping system absorbs the expansion
and there is no force on to the connected equipment.

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Volume VIII Analysing

How to give flexibility?

Flexibility can be provided in many ways. The turns and bends that are required for running a
pipe from one point to another, by themselves, provide some flexibility. This automatic flexibility may
or may not be sufficient. Expansion loops or flexible joints give additional flexibility. Remember, a
short pipe requires less capital cost and reduces operating cost, but a short and direct layout is not
flexible and cannot absorb thermal expansion.

What is an expansion loop?

An expansion loop is when some pipe length is perpendicular to the direction of the main pipe
run. That way, when it expands, the pipe pushes the loop leg rather than transmitting force to the
equipment or structure. The longer the loop leg, the smaller the force

Do not overdo

Flexibility also carries a danger. Engineers tend to provide more flexibility than required,
thinking that the more the flexibility, the safer the pipes. This is a misconception. Think of the train
rails again. If, instead of a small gap, we give a large gap at the joint, the extra flexibility is achieved.
The excessive flexibility provides enough room for the rails to expand, but, when a train passes, it
jumps and, if severe, derails.
Also remember that excessive flexibility adds to the cost due to additional pipes. Pipes take up costly
space. Also an over-flexible system is weaker in resisting wind, arthquake and other occasional loads
and such a system is prone to vibrations.

Use computer
The job of checking the piping flexibility is a specialized job. Software helps the analysis. A
simple system can take some days by using hand calculations. The same system can be analysed in a
few minutes on computer, using software. Also, software can handle almost any complexity of the
system. Formulas are good to help develop an engineer's feelings but hand calculations are behind the
time. Most flexibility software packages are capable of doing more than the flexibility analysis. They
are 'pipe stress analysis programs'. They can handle thermal, weight, earthquake, wind, pressure and
many other loadings. They check not only the piping, but also the connecting equipment viz. pumps,
compressors, vessels etc. The programs also select spring hangers, calculate support loads and so
forth.

Apply your judgment

Software helps the analysis, but, at the same time, engineer should apply judgment. For
example, American piping codes give a formula to know quickly whether flexibility is adequate. The
piping codes also says that analysis need not be performed, if the piping system duplicates a
successfully operating installation or can be adjudged adequate by comparison with previously
analysed system. Modern engineers should appreciate this foresight. Duplication of a good thing is not
a weakness.

Loads
The piping is subjected to the following loads.

Page | 86
Volume VIII Analysing

Self-weight of piping

 Weight of contents
 Weight of insulation
 Weight of refractory
 Weight of inner casing
 Weight of outer casing
 Weight of fittings
 Weight of valves
 Weight of gages
 Weight of instruments
 Weight of attachments
 Weight of equipment
 Weight of devices
 Weight of steam tracers
 Weight of steam traps
 Weight of pumps
 Weight of lugs
 Weight of humans (during maintenance)
 Weight of tools (during maintenance)
 Wind load

Seismic load (earth-quack load)

 Loads due to fire

 Loads due to floods
 Loads due to rain
 Loads due to snow
 Loads due to ice
 Loads due to waves
 Loads due to tsunami
 Loads due to pressure surges
 Loads due to water hammer
 Loads due to steam hammer
 Loads due to opening of valves
 Loads due to closure of valves
 Impact loads from near-by machines
 Vibration loads
 Shock loads
 Transient loads
 Dynamic loads
 Thermal expansion
 Thermal contraction loads
 Loads due to differential settlement of foundations
 Loads due to equipments displacements
 Loads on buried piping from soil, river, sea, ponds and sediments
 Loads on buried piping from vehicles, trains, air-crafts and space-crafts
 Loads due Bourdons effect
 Loads due to flow of fluids
 Internal pressure from fluids
 External pressure from fluids
 Loads due to change in fluid flow direction
Page | 87
 Loads due to manual & artificial manipulation of valves & devices
Volume VIII Analysing

Load Combinations

Sustained Loads

Self-weight of piping, Weight of contents, Weight of insulation, Weight of refractory, Weight

of inner casing, Weight of outer casing, Weight of fittings, Weight of valves, Weight of gages, Weight of
instruments, Weight of attachments, Weight of equipment, Weight of devices, Weight of steam
tracers, Weight of steam traps, Weight of pumps, Weight of lugs, Loads due to soil, river, sea and ponds
for buried piping, Loads due to Bourdons effect, Loads due to flow to fluids laminar and turbulent fluid
flows, Loads due to change in fluid flow direction, Internal pressure and External pressure.

Operating Loads

All the loads (sustained loads) plus Thermal expansion loads, Thermal contraction loads, Loads
due to differential settlement of foundations and Loads due to equipment movements.

Hydraulic Test Loads

All the loads under sustained loads plus hydraulic test water weight and Hydraulic test
pressure

Expansion Loads

All the loads under operating loads minus loads under sustained loads

Occasional Loads

Weight of humans during shut-down, Weight of tools during shut-down, Wind load, Seismic
load (Earth- quake load), Loads due to fire, Loads due to flood, Loads due to rain, Loads due to snow,
Loads due to ice, Loads due to waves, Loads due to Tsunami, Loads due to pressure surges, Loads
due to water hammer, Loads due to steam hammer, Loads due to closure of valves, Impact loads,
Vibration loads Shock loads, Transient loads, Dynamic loads, Loads vehicles, trains, air-crafts and
space-crafts for buried piping, Loads due to opening of valves and Loads due to manual & artificial
manipulations of valves and devices.

Allowable Stress

The allowable stress for piping at working temperature (As per the Power Piping code ASME
B31.1) is given below. For safety, the following shall be satisfied: Induced Stress < Allowable Stress.
The following six conditions shall be satisfied for safety of the piping.

Ssust < Sh
Shyro < 0.9 x Scy
Socct < 1.2 Sh
Sexpn < f (1.25 Sh + 1.25 Sc)
Shear stress < 0.8 x Sh
Bearing stress < 1.6 x Sh

Where,
Ssust = Induced stress due to sustained loads, MPa Page | 88
Shyro = Induced stress due to hydraulic test at shop or field, MPa
Volume VIII Analysing

Socct = Induced stress due to occasional loads like Wind, Seismic, Wave, etc., MPa
Sexpn = Induced stress due to the expansion loads, MPa
Sh = Allowable stress at working temperature, MPa
Sc = Allowable stress in cold condition (at 21˚C), MPa
Scy = Yield stress for the piping material at ambient temperature (21˚C), MPa
f = A factor to take care of fatigue load cycles
= 1.0 for 7,000 fatigue load cycles (maximum)
= 0.9 for 7,000 to 14,000 fatigue load cycles
= 0.8 for 14,000 to 22,000 fatigue load cycles
= 0.9 for 22,000 to 45,000 fatigue load cycles
= 0.9 for 45,000 to 100,000 fatigue load cycles
= 0.5 for the number of fatigue load cycles = 100,00 or more

Sh is the least of the following:

Scy/1.5, (b) Shy/1.5, (c) Scu/3.5, (d) Shu x 1.1/3.5, (e) 0.67 x Sravg, (f) Srmin/1.25 & (g) Scrp

Where,
Scy = Yield stress for the piping material at ambient temperature (21˚C), MPa
Shy = Yield stress for the piping material at working temperature, MPa
Scu = Ultimate tensile stress for the piping material at ambient temperature (21˚C), MPa
Shu = Ultimate tensile stress for the piping material at working temperature, MPa
SRavg = Average stress at working temperature for creep rupture in 100,000 hours, MPa
SRmin= Minimum stress at working temperature foe creep rupture in 100,000 hours, MPa
Scrp = Stress at working temperature to produce a creep strain of 0.01% in 1,000 hours, MPa

Sc is corresponding to Sh, where the working temperature is taken as 21˚C. The values of Sh
and Sc are tabulated in ASME B 31.1, for various materials and various working temperatures. There
are no limits on stresses induced during the normal operation of the piping. There are no explicit
limits on the deformation of piping. The induced stress can be computed using any reliable method.
The hydraulic test shall be conducted at shop or field, at a temperature not less than 21˚C. Piping at
cryogenic temperatures is not covered by ASME B31.1. Vibration requirements are non-mandatory.

Deformation

The piping deforms due to loads. The deformation at any point has two values. One
deformation is the linear deformation. The other deformation is the angular deformation. The linear
deformation can be resolved into three linear deformations in any three mutually perpendicular
directions. Similarly, the angular deformation can be resolved into three angular deformations in any
three mutually perpendicular directions. The deformation of the pipe and the piping components can
be computed by manual or computer-based methods. The induced deformation is to be limited to the
allowable. The allowable deformation as per various codes, standards and regulations are different.
The suggested limit on piping deformation, in the vertically downward direction (linear deformation)
is 2.54 mm (0.1 inch), as per the Power Piping code ASME: B31.1. The allowable deformation, in the
vertically downward direction for tubes, used in some of the boiler industry is not more than 6.35 mm
(0.25 inch). The allowable deformation in the vertically downward direction for structures (as per IS:
800) is Span / 325. There are no limits on the angular deformations for pipes. Some of the piping
supports makers limit the angular deformation of the piping hanger rods to half a Degree to the
vertical direction (half cone angle). The Exercise given below gives the application of these concepts
to a commonly used piping.
Linear Deformation of Piping
Page | 89
Pipe size NPS4 Schedule 80
Volume VIII Analysing

Pipe outside diameter 114.3 mm

Pipe nominal thickness 12.7 mm
Pipe material ASTM A 106 Grade B
Pipe working pressure 120 kg / sq cm (g)
Pipe working metal temperature 350 Degree C
Pipe allowable deformation (ASME: B31.1) 2.54 mm (0.1 inch) suggested
Pipe allowable deformation (Boiler) 6.35 mm (0.25 inch) suggested
Pipe support span 3,250 mm (assumed)
Pipe allowable deformation (IS: 800) Span / 325 = 3,250 / 325 = 10.0 mm suggested

Conclusion:

The allowable deformations as per different codes are different.

Vibration

Piping is subjected to vibration due to loads varying with time. In the stress analysis of piping
the following six assumptions are generally made:

1. Linear behavior
2. Elastic material
3. Homogeneous solids
4. Isotropic material property
5. Steady state loading
6. Static piping

Even-though none of the above indicated six assumptions correct, these assumptions lead to
simplified design and stress analysis. Out-of the six simplifying assumptions, the assumption that the
piping is Static can be improved with Dynamic stress analysis. In the Dynamic stress analysis, the
loading varies with time. In comparison to the Dynamic stress analysis, the piping can be analyzed
considering Transient behavior. Even-though the words Dynamic and Transient are used inter-
changeably in the normal usage of the English language, these words are worlds-apart, in the Technical
terminology. Dynamic behavior indicates the consideration of Mechanical Vibration. The Transient
behavior indicates Thermal Transients. The popularly used piping stress analysis computer programs
like CAESAR and CAEPIPE can perform Dynamic stress analysis. The Transient behavior can be
analyzed using computer programs applicable for checking the fluid flow, fluid distribution and
pumping power. The following loads are Dynamic in nature:

a) Wind load
b) Seismic load (Earth-quack load)
c) Pressure surge
d) Water hammer
e) Steam hammer
f) Sudden opening and / or closing of valves

The methods used for vibration analysis are numerous. The exact method to be used for a particular
application is to be decided by the Stress Analyst. The code on Power Piping - ASME B31.1 doesn’t
mandate the use of Dynamic stress analysis.

RELATIVE DENSITY (SPECIFIC GRAVITY) OF VARIOUS SUBSTANCES

Water (fresh) 100 Mica 29 Page | 90

Volume VIII Analysing

Water (sea average) 103 Nickel 86

Aluminum 256 Oil (linseed) 094
Antimony 670 Oil (olive) 092
Bismuth 980 Oil (petroleum) 076-086
Brass 840 Oil (turpentine) 087
Brick 21 Paraffin 086
Carbon (diamond) 34 Sand (dry) 142
Carbon (graphite) 23 Silicon 26
Carbon (charcoal) 18 Silver 1057
Chromium 65 Slate 21-28
Clay 19 Sodium 097
Coal 136-14 Steel (mild) 787
Cobalt 86 Sulphur 207
Copper 877 Tin 73
Cork 024 Tungsten 191
Glass (crown) 25 Wood (ash) 075
Glass (flint) 35 Wood (beech) 07-08
Gold 193 Wood (ebony) 11-12
Iron (cast) 721 Wood (elm) 066
Iron (wrought) 778 Wood(lignum-vitae) 13
Lead 114 Wood (oak) 07-10
Magnesium 174 Wood (pine) 056
Manganese 80 Wood (teak) 08
Mercury 136 Zinc 70

Notes on CAESAR Load Cases

Definition of a Load Case

In CAESAR terms, a load case is a group of piping system loads that are analyzed together, i.e.,
that are assumed to be occurring at the same time. An example of a load case is an operating analysis
composed of the thermal, deadweight, and pressure loads together. Another is an as-installed analysis
of deadweight loads alone. A load case may also be composed of the combinations of the results of
other load cases; for example, the difference in displacements between the operating and installed
cases. No matter what the contents of the load case, it always produces a set of reports in the output,
which list restraint loads, displacements and rotations, internal forces, moments, and stresses.
Because of piping code definitions of calculation methods and/or allowable stresses, the load cases are
also tagged with a stress category. For example, the combination mentioned above might be tagged as
an Expansion stress case.

The piping system loads which compose the basic (non-combination) load sets relate to
various input items found on the piping input screen. The table below lists the individual load set
designations, their names and the input items, which make them available for analysis.

Designation Name Input items which activate this load case

Pipe Weight, Insulation Weight, Fluid Weight,
W Deadweight
Rigid Weight
Contents Pipe Weight, Insulation Weight, Rigid
WNC Weight No fluid
Weight
WW Water Weight Pipe Weight, Insulation Weight, Water-filledPage | 91
Volume VIII Analysing

Weight, Rigid Weight (usually used for Hydro

Test)
T1 Thermal Set 1 Temperature #1
T2 Thermal Set 2 Temperature #2
T3 Thermal Set 3 Temperature #3
T9 Thermal Set 9 Temperature #9
P1 Pressure Set 1 Pressure #1
P2 Pressure Set 2 Pressure #2
P3 Pressure Set 3 Pressure #3
P9 Pressure Set 9 Pressure #9
HP Hydrostatic Test Pressure Hydro Pressure
D1 Displacements Set 1 Displacements (1st Vector)
D2 Displacements Set 2 Displacements (2nd Vector)
D3 Displacements Set 3 Displacements (3rd Vector)
D9 Displacement Set 9 Displacements (9th Vector)
F1 Force Set 1 Forces/Moments (1st Vector)
F2 Force Set 2 Forces/Moments (2nd Vector)
F3 Force Set 3 Forces/Moments (3rd Vector)
F9 Force Set 9 Forces/Moments (9th Vector)
WIN1 Wind Load 1 Wind Shape Factor
WIN2 Wind Load 2 Wind Shape Factor
WIN3 Wind Load 3 Wind Shape Factor
WIN4 Wind Load 4 Wind Shape Factor
WAV1 Wave Load 1 Wave Load On
WAV2 Wave Load 2 Wave Load On
WAV3 Wave Load 3 Wave Load On
WAV4 Wave Load 4 Wave Load On
U1 Uniform Loads Uniform Loads (1st Vector)
U2 Uniform Loads Uniform Loads (2nd Vector)
U3 Uniform Loads Uniform Loads (3rd Vector)
CS Cold Spring Material # 18 or 19
H Hanger Initial Loads Hanger Design or Pre-specified Hangers

Note Available piping system loads display on the left side of the Static Load Case screen.

The following family of load cases provides a valid example of algebraic combination

Load Case Designation Comments

Hot operating; note the 0.67 scale factor which takes
1 W+T1+P1+H+0.67CS (OPE)
credit only for 2/3 of the cold spring
2 W1+P1+H+0.67CS(OPE) Cold operating: with cold spring included
3 W1+P1+H(SUS) Traditional sustained case
Wind case; note this will be manipulated later to
4 WIN1(OCC) represent average wind (1X), maximum wind (2X),
as well as positive and negative directions.
Traditional expansion case, cold to hot (note
5 L1-L2(EXP)
reference to "L" for "Load", rather than "DS".
Same case but now evaluated for fatigue at 10,000
6 L1-L2(FAT)
cycles.
7 L1+L4(OPE) Hot operating with average wind (in positive Page | 92
Volume VIII Analysing

direction).
Hot operating with average wind (in negative
8 L1-L4(OPE)
direction).
Hot operating with maximum wind (in positive
9 L1+2L4(OPE)
direction).
Hot operating with maximum wind (in negative
10 L1-2L4(OPE)
direction).
Cold operating with average wind (in positive
11 L2+L4(OPE)
direction).
Cold operating with average wind (in negative
12 L2-L4(OPE)
direction).
Cold operating with maximum wind (in positive
13 L2+2L4(OPE)
direction).
Cold operating with maximum wind (in negative
14 L2-2L4(OPE)
direction).
15 L3+L4(OCC) Occasional stress case, sustained plus average wind.
Occasional stress case, sustained plus maximum
16 L3+2L4(OCC)
wind.
Maximum restraint load case (the combination
17 L9+L10+L11+L12(OPE)
option should be MAX).

Recommended Load Cases

When the user first enters the static load case editor CAESAR recommends, based on the loads
defined in the model, three types of load cases: Operating, Sustained, and Expansion (but not
occasional).

Operating load cases represent the loads acting on the pipe during hot operation, including
both primary (weight pressure, and force) loadings and secondary (displacement and thermal)
loadings. Operating cases are used to find hot displacements for interference checking, and hot
restraint and equipment loads. Generally when recommending operating load cases, CAESAR
combines weight, pressure case #1, and hanger loads with each of the thermal load cases
(displacement set #1 with thermal set #1, displacement set #2 with thermal set #2, etc....), and then
with any cold spring loads.
Sustained load cases represent the primary force-driven loadings acting on the pipe, i.e.,
weight and pressure alone. This usually coincides with the cold (as-installed) load case. Sustained load
cases are used to satisfy the code sustained stress requirements, as well as to calculate as-installed
restraint and equipment loads. Sustained load cases are generally built by combining weight with each
of the pressure and force sets, and then with any hanger loads.

Expansion load cases represent the range between the displacement extremes (usually
between the operating and sustained cases). Expansion load cases are used to meet expansion stress
requirements.

Most users will specify only one temperature and one pressure. Such input would simplify the
recommended cases to something like:

Case # 1 W+D1+T1+P1+H (OPE) OPERATING

Case # 2 W+P1+H (SUS) SUSTAINED LOAD CASE
Case # 3 L1-L2 (EXP) EXPANSION LOAD CASE

The user should review any load recommendations made by CAESAR. Page | 93
Volume VIII Analysing

Note CAESAR does not recommend any occasional load cases. Definition of these is the
responsibility of the user.

If these recommended load cases do not satisfy the analysis requirements, they may always be deleted
or modified. Conversely, the load cases may always be reset to the program recommended set at any
time.

If the user has an operating temperature below ambient in addition to one above ambient the user
should add another expansion load case as follows:

Case # 1 W+D1+T1+P1+H (OPE)

Case # 2 W+D2+T2 +P1+H (OPE)
Case # 3 W+P1+H (SUS) SUSTAINED LOAD CASE
Case # 4 L1-L3 (EXP) EXPANSION LOAD CASE
Case # 5 L2-L3 (EXP) EXPANSION LOAD CASE
Case # 6L2-L1 (EXP) the user should add this since it is not
recommended by CAESAR

Recommended Load Cases for Hanger Selection

If spring hangers are to be designed by the program, two additional load cases must first be
analyzed in order to obtain the data required to select a variable support. The two basic requirements
for sizing hangers are the deadweight carried by the hanger (hot load) and the range of vertical travel
to be accommodated. The first load case (traditionally called “Restrained Weight”) consists of only
deadweight (W). For this analysis CAESAR includes a rigid restraint in the vertical direction at every
location where a hanger is to be sized. The load on the restraint from this analysis is the deadweight
that must be carried by the support in the hot condition. For the second load case, the hanger is
replaced with an upward force equal to the calculated hot load, and an operating load case is run. This
load case (traditionally called “Free Thermal”) includes the deadweight and thermal effects, the first
pressure set (if defined), and any displacements, (W+D1+T1+P1). The vertical displacements of the
hanger locations, along with the previously calculated deadweights are then passed on to the hanger
selection routine. Once the hangers are sized, the added forces are removed and replaced with the
selected supports along with their pre-loads (cold loads), designated by load component H. (Note that
load component H may appear in the load cases for hanger design if the user has predefined any
springs- in this case it would represent the pre-defined operating loads.) CAESAR then continues with
the load case recommendations as defined above. A typical set of recommended load cases for a single
operating load case spring hanger design appears as follows:

Case # 1W WEIGHT FOR HANGER LOADS

Case # 2 W+D1+T1+P1 OPERATING FOR HANGER TRAVEL
Case # 3 W+D1+T1+P1+H (OPE) OPERATING (HGRS. INCLUDED
Case # 4 W+P1+H (SUS) SUSTAINED LOAD CASE
Case # 5 L3-L4 (EXP) EXPANSION LOAD CASE

These hanger sizing load cases (#1 & #2) generally supply no information to the output
reports other than the data found in the hanger tables. Note how cases 3, 4, & 5 match the
recommended load cases for a standard analysis with one thermal and one pressure defined. Also
notice how the displacement combination numbers in case 5 have changed to reflect the new order. If
multiple temperatures and pressures existed in the input, they too would appear in this set after the
second spring hanger design load case. Two other hanger design criteria also affect the recommended
Page
load cases. If the “actual cold loads” for selected springs are to be calculated, one additional load | 94
case
Volume VIII Analysing

(WNC+H) would appear before case #3 above. If the piping system’s hanger design criteria are set so
that the proposed springs must accommodate more than one operating condition, other load cases
must additionally appear before the case #3 above. An extra hanger design operating load case must
be performed for each additional operating load case used to design springs. Refer to the discussion of
the hanger design algorithm for more information on these options.

Load Case Report Purpose

SUSTAINED STRESS Code compliance
EXPANSION STRESS Code compliance
OPERATING DISPLACEMENTS Interference checks
OPERATING RESTRAINTS Hot restraint, equipment loads
SUSTAINED RESTRAINTS As-installed restraint, equipment loads

Note Load cases used for hanger sizing produce no reports. Also, the hanger table and Hanger
table with text reports are printed only once even though more than one active

SYMBOLS USED IN THE FORMULAE

t = minimum required thickness (millimeters, mm).

P = maximum allowable working pressure (megapascals, MPa). (Note - this refers to gauge
pressure)

D = outside diameter of cylinder (millimeters, mm)

R = inside radius of cylinder (millimeters, mm)

E = efficiency of longitudinal welded joints or of ligaments between openings, whichever is

lower. The values allowed for ‘E’ are listed in This is a factor that has no units, (for example, the value
of ‘E’ for seamless cylinders is 1.00)

S = maximum allowable stress value, at the operating temperature of the metal, as listed in the
Section II, Part D, Table 1A, (megapascals, MPa).. The tables are located in an Section II, Part D at the
back of the 2004 ASME Academic Code Extract. Each table spans four pages. Reference the line number
on the first page to follow along each page until you find the correct temperature value required.

C = minimum allowance for threading and structural stability, (millimeters, mm).

E = thickness factor for expanded tube ends (millimeters, mm).

y = a temperature coefficient: This factor has no units and has a value between 0.4 and 0.7. The
values allowed for y are listed in (for example, for ferritic steel at 550°C, the value of ‘y’ is 0.7)

Page | 95
Volume VIII Analysing

CRITICAL LINE ANALYZING

Following data’s are provided

Pipe Size : 6” Sch 120

Insulation Thick : 150 mm
Temp : 510°
Pressure : 120 bar
Material : SA 335 P12
Fluid Density : 0.5 sg
Insulation Density : 100 kg/m3

Header OD 14” Sch 120

Pad Thick 22 mm
Distance to head 2.5 m
Distance to Stiffener 4.5 m
Fx 2KN
Fy 3KN
Fz 2KN

Turbine
Fx 5KN
Fy 2KN
Fz 3KN

DX +10 mm
DY +5 mm
DZ -6mm

Enter all data in the classic piping input spread sheet and model the line (see fig 1) if there any nozzle
in the line, provide the data
There are two types of equipments nozzle
 Static Equipments (like Tank, vessels, headers) Page | 96
 Rotary Equipments (like pump, turbine, and compressor)
Volume VIII Analysing

Flexible Nozzles

This auxiliary screen is used to describe flexible nozzle connections. When entered in this way,
CAESAR II automatically calculates the flexibilities and inserts them at this location.

At node number 10 header nozzles connected with piping system.

Header OD 14” Sch 120

Pad Thick 22 mm
Distance to head 2.5 m
Distance to Stiffener 4.5 m
Provide the nozzle data at node number 10 (see fig 2)

Page | 97
Volume VIII Analysing

If there any force acting on the nozzle, provide force & moment value at node number 10
Forces & Movements

Activate by double-clicking the Forces/Moments

check box on the Pipe Element Spreadsheet.
Deactivate by double clicking the check box a
second time. Force and moment acting at node
Number 10

You can enter the force and moment as

Fx 2KN
Fy 3KN
Fz 2KN (See fig 3)

Fig 3

Displacements
Activate by double-clicking the Displacements check
box on the Pipe Element Spreadsheet. Deactivate by
double clicking the Displacements check box a second
time.

This auxiliary screen is used to enter imposed displacements for up to two nodes per spreadsheet.
Displacement reaction At node number 100. You can enter the displacement as

DX +10 mm
DY +5 mm
DZ -6mm (see fig 4)

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Volume VIII Analysing

Fig 4

Forces & Movements

Activate by double-clicking the

Forces/Moments check box on the Pipe
Element Spreadsheet. Deactivate by double
clicking the check box a second time. Force
and moment acting At node Number 100.

You can enter the force and moment as

Fx 5KN
Fy 2KN
Fz 3KN (see fig 5)

Page | 99
Volume VIII Analysing

Fig 5

SUSTAINED LOADS

Self-weight of piping, Weight of contents, Weight of insulation, Weight of refractory, Weight of inner
casing, Weight of outer casing, Weight of fittings, Weight of valves, Weight of gages, Weight of
instruments, Weight of attachments, Weight of equipment, Weight of devices, Weight of steam
tracers, Weight of steam traps, Weight of pumps, Weight of lugs, Loads due to soil, river, sea and ponds
for buried piping, Loads due to Bourdons effect, Loads due to flow to fluids laminar and turbulent fluid
flows, Loads due to change in fluid flow direction, Internal pressure and External pressure.

Simply denotes as SUS = W+ P1

Click the Static analysis button on caesar main window as mention in the (fig 6)

Now you can see the Static output processor display like (fig 7)

3D plot tool

Here you can see the load case list, Standard report, and General computer result & output viewer
wizard. For sustained cases check the code compliance for each nodes.
Provide the +y restraints based on, maximum Stress acting on the nodes And Minimize the code stress
ratio. (Within allowable limit)
We can see the changes while gravity load acting on the piping system by using 3D tool. (See fig 8)

Page | 100
Volume VIII Analysing

Fig 8
Check also displacement for the sustained load cases. This gravity force will create the maximum
stresses. By providing +Y restraints (shoe supports) will reduce the stress value.fig 9 shows shoe
support

Page | 101
Volume VIII Analysing

Restraints are provided in the piping primarily to transfer the Sustain loads to the supporting
structure. Restraints are usually oriented in any one of the coordinate axes of the plant. Inclined
restraints are also used. Usually the restraints are double acting. Struts and ties, which are single
acting, are also used. A single acting restraint is a device, which carries only tension or compression.

+Y Restrain ( Shoe Support) +Y Restrain (Shoe Support)For

For Horizontal Pipe Line Vertical Pipe Line

Fig 10

Fig11
Provide +y restraints nearer to components fittings.
Should maintain the span length between two restraints.

Go for static output processor, Check evaluation passed or not (Sustained + Code compliance). If it is
not passed, back to input Manu again provide the +Y restraints based on where the maximum stress
Refer fig 12 after provided all +y restraints. once the evaluation is based font color also changed from
red to black on the report.

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Volume VIII Analysing

Fig 12
After proving all + y restraints check back the result.
Refer fig 13 report for sustained stress ratio, here the code stresses is within our allowable stress limit.
Now piping system sustained vise safe.

Fig 13

All the +y restraints taking gravity load, this Gravity load will transfer in to the structural, now we can
check this structural are capable to withstand this load or not, through civil load case data. Change the
span length, if restraints taking Maximum load (can check sustained + restraints) (see fig 14)

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Volume VIII Analysing

Gravity load taking each supports

Fig14

Node number 85 taking maximum load, in this cases change span length distribute the load uniformly
to other supports. Otherwise provide new supports or hangers

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Hangers

You can enter the all hanger data by Double pick hanger tool hanger spread sheet will appear
on the auxiliary screen. (Fig 15). Caesar II will decide which type of hanger required at location. Only
provide data, what you are receiving from client. Check the (sustained + restraint) again hanger taking
load as mention in (fig 16).

Fig 15

Fig 16

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Volume VIII Analysing

Expansion Loop

The expansion fitting is one method of accommodating expansion. These fittings are placed within a
line, and are designed to accommodate the expansion, without the total length of the line changing.
They are commonly called expansion bellows, due to the bellows construction of the expansion sleeve.

Other expansion fittings can be made from the pipe work itself. This can be a cheaper way to
solve the problem, but more space is needed to accommodate the pipe. Full loop this is simply one
complete turn of the pipe and, on steam pipe work, should preferably be fitted in a horizontal rather
than a vertical position to prevent condensate accumulating on the upstream side.

The downstream side passes below the upstream side and great care must be taken that it is
not fitted the wrong way round, as condensate can accumulate in the bottom. When full loops are to be
fitted in a confined space, care must be taken to specify that wrong-handed loops are not supplied.

The full loop does not produce a force in opposition to the expanding pipe work as in some
other types, but with steam pressure inside the loop, there is a slight tendency to unwind, which puts
an additional stress on the flanges.

This design is used rarely today due to the space taken up by the pipe work, and proprietary
expansion bellows are now more readily available. However large steam users such as power stations
or establishments with large outside distribution systems still tend to use full loop type expansion
devices, as space is usually available and the cost is relatively low.

Horseshoe or lyre loop When space is available this type is sometimes used. It is best fitted
horizontally so that the loop and the main are on the same plane. Pressure does not tend to blow the
ends of the loop apart, but there is a very slight straightening out effect. This is due to the design but
causes no misalignment of the flanges.
If any of these arrangements are fitted with the loop vertically above the pipe then a drain
point must be provided on the upstream side as depicted in Fig

Horseshoe or lyre loop

Expansion loops

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Expansion loop

The expansion loop can be fabricated from lengths of straight pipes and elbows welded at the
joints. An indication of the expansion of pipe that can be accommodated by these assemblies is shown
in Figure

It can be seen from Figure that the depth of the loop should be twice the width, and the width
is determined from Figure, knowing the total amount of expansion expected from the pipes either side
of the loop.

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Expansion Loop calculation

For a Basic Expansion Loop

L =2xW
W = 6.225 x √Δ D
5
Where

L = Length of Expansion Loop

W = Width of Expansion Loop
Δ = Thermal expansion of run
D = Pipe Outside Diameter
E = Modulus of Elasticity

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Report Generation

1. Input echo
2. Miscellaneous Data
3. Load Case Report

4. Sustain =>code compliance

5. Expansion =>code compliance

6. Operating =>Displacement
7. Sustain =>Displacement
8. Expansion =>Displacement

9. Operating =>Restrains
10. Sustain =>Restrains
11. Expansion =>Restrains
12. Operating + Sustain + Expansion =>Restraint Summary

13. Operating =>Global Element Forces

14. Sustain => Global Element Forces
15. Expansion => Global Element Forces

16. Operating =>Global Element Forces Extended

17. Sustain => Global Element Forces Extended
18. Expansion => Global Element Forces Extended

19. Operating => Local Element Forces

20. Sustain => Local Element Forces
21. Expansion => Local Element Forces

22. Operating => Stress

23. Sustain => Stress
24. Expansion => Stress

25. Operating => Stress Extended

26. Sustain => Stress Extended
27. Expansion => Stress Extended
28. Operating + Sustain + Expansion =>Stress Summary

29. Hanger table

30. Warning Report

What are all the input, we are provided already in classic input file we can see. Here customize option
also available. In the static output processor we can see all type of report

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Select input echo and pick view report, now you can see the list of inputs on the screen, here you can
select which report option you want then select ok. The report sheet will appeared. In this marked
report option only we can get.

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STRESS ISOMETRIC GENERATION

A Stress isometric is used by engineers as a visual record of pipe stress analysis model and summary of
the design information used to model a safe piping system.
The Customizable stress isometric plot is created using the open plant isometric manager and shows
a)Fully dimensioned isometric b)Table of important summary design data including model
information, pipe properties, valves and flange data, maximum stresses, design support data, design
spring and constant spring hanger data, design load data for vessels, structures and equipments.
For generating stress isometric drawing go for Caesar main window and select the generate stress
isometric

Step: 1

New window will opened in this you can create isometric, edit isometric and you can save also the
template as follows.

Click create isometric drawing tool one window will appeared as select the drawing style. Here am
using default style then pick ok. agine one new window will open as you can select the drawing and
pick view. Your project drawing will open as isometric drawing in an Auto cad file. Here the drawing
will divided into two drawing sheets. Refer the drawing as below.

Step: 2

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Step: 3

Step 4

Step 5

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Volume IX Equipment& Component Analysing

Volume-IX Equipment & Component Analysing

The CAESAR II equipment and component compliance analytical modules are executed from
the CAESAR II Main Menu using the Analysis Menu. Vessels, flanges, turbines, compressors, pumps and
heat exchangers can be checked for excessive piping loads in accordance with appropriate standards.
Input is via tabbed spreadsheets, and help screens are available for each data cell (launched with [F1]
or the? key). Output reports can be sent to the printer, terminal or files.

Often suction (inlet), discharge (exhaust), and extraction lines are analyzed for forces and
moments in separate runs of a pipe stress program. Once all of the loadings for a particular piece of
equipment are computed, the equipment program is executed to determine if these loads are
acceptable in accordance with the governing code. The user enters the equipment’s basic geometry
and the loads on its nozzles computed from the piping program. The equipment analysis determines if
these loads are excessive.

One convenient feature of the CAESAR II equipment programs is that nozzles on equipment
can be analyzed separately. Often times a user will only have suction side loads, and often the
particular dimensions of the pump are unknown, or are difficult to obtain. In these cases, CAESAR II
accepts zeros or “no-entries” for the unknown data and will still generate a “single-nozzle” equipment
check report. Therefore, while overall compliance may not be evaluated, the user can still check the
individual nozzle limits. This is a valuable tool to have, as in this case the user is looking more for load
guidance, rather than for some fixed or precise limit on allowable.

All of these program modules share the same interface for easy transition. The individual modules are
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Stress Intensification Factors

With this module, intersection stress intensification factors (SIFs) can be computed for any of
the three-pipe type intersections available in CAESAR II

Intersection Types
A sample input spreadsheet is shown below

Intersection Stress Intensification Factors

Stress intensification factors are reported for a range of different configuration values.
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Bend Stress Intensification Factors

This module provides a scratch pad for determining stress intensification factors (SIFs) for various
bend configurations under different codes.

Bend stress intensification factors can be computed for

 Pipe bends without any additional attachments. These calculations are done exactly according
to the piping code being used.
 Mitered pipe bends. These calculations are done exactly according to the piping code being
used.
 Pipe bends with a trunnion attachment. These calculations are taken from the paper “Stress
Indices for Piping Elbows with Trunnion Attachments for Moment and Axial Loads,” by
Hankinson, Budlong and Albano, in the PVP Vol. 129, 1987. The bend stress intensification
factor input spreadsheet is shown below:

Bend Stress Intensification Spreadsheet

Input here is fairly straight forward; if there is a question about a particular data entry, the help
screens should be queried. In most cases data that does not apply is left blank.

For example, to review the SIFs for a bend that does not have a trunnion, the three trunnion related
input fields should be left blank.

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Bend Stress Intensification Factors – Trunnion

WRC 107 (Vessel Stresses)

The Welding Research Council Bulletin 107 (WRC 107) has been used extensively since 1965 by
design engineers to estimate local stresses in vessel/attachment junctions.

Note There are three editions of WRC 107 available from the program; the default is set by the
user in the Configure-Setup option.

WRC 107 Bulletin provides an analytical tool to evaluate the vessel stresses in the immediate vicinity
of a nozzle. This method can be used to compute the stresses at both the inner and outer surfaces of
the vessel wall, and report the stresses in the longitudinal and circumferential axes of the
vessel/nozzle intersection. The convention adopted by WRC

107 to define the applicable orientations of the applied loads and stresses for both spherical and
cylindrical vessels are shown in the figure below.

SPHERICAL SHELLS CYLINDRICAL SHELLS

To Define WRC Axes: To Define WRC Axes:

1) P-axis: Along the Nozzle centerline and 1) P-axis: Along the Nozzle centerline and
positive entering the vessel. positive entering the vessel.

2) M1-axis: Perpendicular to the nozzle center 2) MC-axis: Along the vessel centerlinePage
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line along convenient global axis. positive to correspond with any parallel global
axis.
3) M2-axis: Cross the P-axis into the M1 axis and 3) ML-axis: Cross the P-axis with the MC axis and
the result is the M2-axis. the result is the ML-axis.
To Define WRC Stress Points: To Define WRC Stress Points:

u-upper, means stress on outside of vessel wall at u-upper, means stress on outside of vessel wall at
junction. junction.
l-lower, means stress on inside of vessel at l-lower, means stress on inside of vessel at
junction. junction.
A-Position on vessel at junction, along negative A-Position on vessel at junction, along negative
M1 axis. MC axis.
B-Position on vessel at junction, along positive B-Position on vessel at junction, along positive
M1 axis. MC axis.
C-Position on vessel at junction, along positive C-Position on vessel at junction, along positive
M2 axis. ML axis.
D-Position on vessel at junction, along negative D-Position on vessel at junction, along negative
M2 axis. ML axis.
Note: Shear axis “VC” is parallel, and in the
same direction as the bending axis “ML”. Shear
axis “VL” is parallel, and in the Opposite direction
as the bending axis
“MC”.

WRC Axes Orientation

It has also been a common practice to use WRC 107 to conservatively estimate vessel shell
stress state at the edge of a reinforcing pad, if any. The stress state in the vessel wall when the nozzle
has a reinforcing pad can be estimated by considering a solid plug, with an outside diameter equal to
the O.D. of the reinforcing pad, subjected to the same nozzle loading.

Note Before attempting to use WRC 107 to evaluate the stress state of any nozzle/vessel
junction, the user should always make sure that the geometric restrictions limiting the application of
WRC 107 are not exceeded. These vary according to the attachment and vessel types. The user is
referred to the WRC 107 bulletin directory for this information.

The WRC 107 method should probably not be used when the nozzle is very light or when the
parameters in the WRC 107 data curves are unreasonably exceeded. Output from the WRC 107
program includes the figure numbers for the curves accessed, the curve abscissa, and the values
retrieved. The user is urged to check these outputs against the actual curve in WRC 107 to get a “feel”
for the accuracy of the stresses calculated. For example, if parameters for a particular problem are
always near or past the end of the figures curve data, then the calculated stresses may not be reliable.

The WRC 107 program can be activated by selecting Analysis - WRC 107/297 from the Main Menu.
The user may be prompted to enter a job name, and then the following data entry screen appears:

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The input data is accumulated by the processor in four spreadsheets. The first sheet displays the title
block, the second and third sheets collect the vessel and the nozzle (attachment) geometry data,
respectively. From the Vessel Data spreadsheet click the WRC 107 radio button. The WRC 107 Version
Year and Use Interactive Control checkboxes can also be enabled from this spreadsheet.

The Hot and Cold Allowable Stress Intensities of the vessel as defined per ASME VII, Division 2 can be
entered manually or updated from the Material Database by providing the Material Name and
Operating Temperature in the corresponding fields. Any allowable values entered manually or
modified by the user, display in red.

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The nozzle loading is specified on the last spreadsheet, according to specific load cases, which
include sustained, expansion and occasional cases. These loads are found in the CAESAR II output
restraint load summary under the corresponding load cases or may be extracted from the static output
files automatically by clicking the Get from Output... button. The WRC 107 specific local input
coordinate system has been incorporated into the program; so the loads may be input in either the
Global CAESAR II convention, or in the Local WRC 107 coordinate system. To enter loads in WRC 107
convention, click the WRC 107 radio button. If the Global CAESAR II convention is used, the vessel and
nozzle centerline direction cosines must be present. Note, the positive direction is the Nozzle
centerline vector pointing from the nozzle connection towards the vessel centerline. The loads
convention may be freely converted from global to local and back provided the direction cosines are
present.

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Nozzle curves in WRC Bulletin 107 cover essentially all applications of nozzles in vessels or
piping; however, should any of the interpolation parameters, i.e. Beta, etc. fall outside the limits of the
available curves, some extrapolation of the WRC method must be used. The current default is to use
the last value in the particular WRC table. If one wishes to control the extrapolation methodology
interactively, you may do so by changing the WRC 107 default from “USE LAST CURVE VALUE” to
“INTERACTIVE CONTROL” on the Computation Control tab located inside the Configure-Setup module
of the Main Menu or directly in the WRC 107 input file, on the Vessel Data tab. After entering all data,
the WRC 107 analysis may be initiated through the Analyze-WRC 107/297 menu option or by clicking
the Local Stress Analysis button on the toolbar. CAESAR II will automatically perform the ASME
Section VIII, Div. 2 summation. Output reports may be viewed at the terminal or printed. Clicking the
button, performs the initial WRC 107 calculation and summation and sends the result to Microsoft_
Word.

WRC 107 Stress Summations

Because the stresses computed by WRC 107 are highly localized, they do not fall immediately under
the B31 code rules as defined by B31.1 or B31.3. The Appendix 4-1 of ASME Section VIII, Division 2
(“Mandatory Design Based on Stress Analysis”) does however provide a detailed approach for dealing
with these local stresses. The analysis procedure outlined in the aforementioned code is used in
CAESAR II to perform the stress evaluation. In order to evaluate the stresses through an elastic
analysis, three stress combinations (summations) must be made:

WRC Bulletin 297

Published in August of 1984, Welding Research Council (WRC) 297 attempts to extend the
Page
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Volume IX Equipment& Component Analysing

differs from the widely used WRC 107 primarily in that WRC 297 is designed for larger d/D ratios (up
to 0.5), and that WRC 297 also computes stresses in the nozzle and the vessel. (WRC 107 only
computes stresses in the vessel.)

The CAESAR II WRC 297 module shares the same interface with WRC 107. To enable the WRC
297 analysis, from the Vessel tab, click the WRC 297 radio button. The module provides spreadsheets
for vessel data, nozzle data, and imposed loads. Vessel and Nozzle data fields function the same way as
those in WRC 107. Currently WRC 297 supports one set of loads. The loads may be entered in either
Global CAESAR II convention, or in the Local WRC 107 coordinate system. If Global CAESAR II
convention is selected vessel and nozzle direction cosines must be present in order to convert the
loads into the Local WRC 297 convention as discussed in the WRC 297 bulletin.

Analysis - WRC 297

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Nozzle Screen

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WRC 297 – Loads

The CAESAR II version of WRC 297 also adds the pressure component of the stress using Lame’s
equations, multiplied by the stress intensification factors found in ASME Section VIII, Div. 2, Table AD-
560.7. The pressure stress calculation is not a part of the WRC 297 bulletin, but is added here as a
convenience for the user.

Note CAESAR II also utilizes, through the piping input processor, the nozzle flexibility calculations
described in WRC 297 refer to Chapter 3 of the Technical Reference manual.

When provided with the necessary input, CAESAR II calculates the stress components at the four
locations on the vessel around the nozzle and also the corresponding locations on the nozzle. Stresses
are calculated on both the outer and inner surfaces (upper and lower). These stress components are
resolved into stress intensities at these 16 points around the connection. Refer to the WRC 107
discussion for more information on the allowable limits for these stresses and output processing.

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Flange Leakage/Stress Calculations

The Flange Leakage/Stress Calculations are started by selecting Main Menu option Analysis Flanges.

There have been primarily two different ways to calculate stress and one way to estimate leakage for
flanges that have received general application over the past 20 years. The stress calculation methods
are from the following sources:

• ASME Section VIII

• ANSI B16.5 Rating Tables

The leakage calculations were also based on the B16.5 rating table approach. Leakage is a function of
the relative stiffnesses of the flange, gasket and bolting. Using the B16.5 estimated stress calculations
to predict leakage does not consider the gasket type, stiffness of the flange, or the stiffness of the
bolting. Using B16.5 to estimate leakage makes the tendency to leak proportional to the allowable
stress in the flange, i.e. a flange with a higher allowable will be able to resist higher moments without
leakage. Leakage is very weakly tied to allowable stress, if at all.

The CAESAR II flange leakage calculation is COADE’s first attempt to improve upon the solution of this
difficult analysis problem. Equations were written to model the flexibility of the annular plate that is
the flange, and its ability to rotate under moment, axial force, and pressure. The results compare
favorably with three dimensional finite element analysis of the flange junction. These correlations
assume that the distance between the inside diameter of the flange and the center of the effective
gasket loading diameter is smaller than the distance between the effective gasket loading diameter and
the bolt circle diameter, i.e. that (G-ID) < (BC-G), where, G is the effective gasket loading diameter, ID is
the inside diameter of the flange, and BC is the diameter of the bolt circle.

Several trends have been noticed as flange calculations have been made:

 The thinner the flange, the greater the tendency to leak.

 Larger diameter flanges have a greater tendency to leak.
 Stiffer gaskets have a greater tendency to leak.
 Leakage is a function of bolt tightening stress.

Input for the Flange Module is broken into four sections. The first section describes flange geometry.

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Flange Analysis

The second section contains data on the bolts and gasket.

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Bolts and Gasket

The third section is used to enter material and stress-related data.

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Material and Stress Data

The fourth section contains the imposed loads.

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Imposed Loads

Note on bolt tightening stress

This is a critical item for leakage determination and for computing stresses in the flange. The
ASME code bases its stress calculations on a pre-specified, fixed equation for the bolt stress. The
resulting value is however often not related to the actual tightening stress that appears in the flange
when the bolts are tightened. For this reason, the initial bolt stress input field that appears in the first
section of data input, Bolt Initial Tightening Stress, is used only for the flexibility/leakage
determination. The value for the bolt tightening stress used in the ASME flange stress calculations is as
defined by the ASME code:

Bolt Load = Hydrostatic End Force + Force for Leak tight Joint
If the Bolt Initial Tightening Stress field is left blank, CAESAR II uses the value
45000 /√ d
Where 45,000 psi is a constant and d is the nominal diameter of the bolt (correction is made for metric
units).

This is a rule of thumb tightening stress, that will typically be applied by field personnel
tightening the bolts. This computed value is printed in the output from the flange program. It is
interesting to compare this value to the bolt stress printed in the ASME stress report (also in the
output). It is not unusual for the “rule-of-thumb” tightening stress to be larger than the ASME required
stress. When the ASME required stress is entered into the Bolt Initial Tightening Stress data field, a
comparison of the leakage safety factors can be made and the sensitivity of the joint to the tightening
torque can be ascertained. Users are strongly encouraged to “play” with these numbers to get a feel for
the relationship between all of the factors involved.
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Using the CAESAR II Flange Modeler

Only the following input parameters are required to get a leakage report. These parameters Include

 Flange Inside Diameter

 Flange Thickness
 Bolt Circle Diameter
 Number Of Bolts
 Bolt Diameter
 Effective Gasket Diameter
 Uncompressed Gasket Thickness
 Effective Gasket Width
 Leak Pressure Ratio
 Effective Gasket Modulus
 Externally Applied Moment
 Externally Applied Force
 Pressure

The help screens (press [F1] or ? at the data cell) are very useful for all of the input items and should
be used liberally here when there are questions. Unique input cells are discussed as follows:

Leak Pressure Ratio

This value is taken directly from Table 2-5.1 in the ASME Section VIII code. This table is reproduced in
the help screens. This value is more commonly recognized as “m”, and is termed the “Gasket Factor” in
the ASME code. This is a very important number for leakage determination, as it represents the ratio of
the pressure required to prevent leakage over the line pressure.

Effective Gasket Modulus

Typical values are between 300,000 and 400,000 psi for spiral wound gaskets. The higher the modulus
the greater the tendency for the program to predict leakage. Errors on the high side when estimating
this value will lead to a more conservative design.

Flange Rating

This is an optional input, but results in some very interesting output. As mentioned above, it has been
a widely used practice in the industry to use the ANSI B16.5 and API 605 temperature/ pressure rating
tables as a gauge for leakage. Because these rating tables are based on allowable stresses, and were not
intended for leakage prediction, the leakage predictions that resulted were a function of the allowable
stress for the flange material, and not the flexibility, i.e. modulus of elasticity of the flange. To give the
user a “feel” for this old practice, the minimum and maximum rating table values from ANSI and API
were stored and are used to print minimum and maximum leakage safety factors that would be
predicted from this method. Example output that the user will get upon entering the flange rating is
shown as follows:

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Remaining Strength of Corroded Pipelines, B31G

The B31G criteria provide a methodology whereby corroded pipelines can be evaluated to
determine when specific pipe segments must be replaced. The original B31G document incorporates a
healthy dose of conservatism and as a result, additional work has been performed to modify the
original criteria. This additional work can be found in project report PR-3805, by Battelle, Inc. The
details of the original B31G criteria as well as the modified methods are discussed in detail in this
report.

CAESAR II implements these B31G computations from the Main Menu select Analysis-B31G. The user
is then presented with two spreadsheets on which the problem specific data can be entered. CAESAR II
determines the following values according to the original B31G criteria and four modified methods.

These values are

 The hoop stress to cause failure

 The maximum allowed operating pressure
 The maximum allowed flaw length

The four modified methods vary in the manner in which the corroded area is estimated. These
methods are

.85dL
The corroded area is approximated as 0.85 times the maximum pit depth times the flaw length.
Exact
The corroded area is determined numerically using the trapezoid method.
Equivalent
The corroded area is determined by multiplying the average pit depth by the flaw length.
Additionally, an equivalent flaw length (flaw length * average pit depth / maximum pit depth) is used
in the computation of the Folias factor.
Effective
This method also uses a numerical trapezoid summation, however, various sub lengths of the
total flaw length are used to arrive at a worst case condition. Note that if the sub length which
produces the worst case coincides with the total length, the Exact and Effective methods yield the
same result.

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The input screens from the B31G processor are shown below. All input cells have associated
help text for user convenience. Note that most of the data required by this processor is acquired
through actual field measurements.

Data Spreadsheet

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A maximum of twenty pit measurements may be entered on the Measurements spreadsheet.

Measurements Spreadsheet

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Once the data has been entered, the Analyze menu option initiates the computations. A typical output
report is shown as follows.

The data in the input and the resulting output are consistent with the example from the PR-3-
805 report on page B-19. For additional information or backup on these computations, an
intermediate computation file is generated. For additional information on this processor, please refer
to either the B31G document or the Battelle project report PR-3-805.

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Expansion Joint Rating

CAESAR II provides a computation module which computes a limit for the total displacement per
corrugation of an expansion joint. According to EJMA (Expansion Joint Manufacturers Association), the
maximum permitted amount of axial movement per corrugation is defined as erated where

ex + ey + eq < erated

The terms in the above equation are defined as:

ex = The axial displacement per corrugation resulting from imposed axial movements.
ey = The axial displacement per corrugation resulting from imposed lateral deflections.
eq = The axial displacement per corrugation resulting from imposed angular rotation, i.e. bending.
erated = The maximum permitted amount of axial movement per corrugation. This value should be
obtained from the Expansion Joint Manufacturer’s catalog.

In addition, EJMA states,

“Also, [as an expansion joint is rotated or deflected laterally] it should be noted that one side of the
bellows attains a larger projected area than the opposite side. Under the action of the applied pressure,
unbalanced forces are set up which tend to distort the expansion joint further. In order to control the
effects of these two factors a second limit is established by the manufacturer upon the amount of
angular rotation and/or lateral deflection which may be imposed upon the expansion joint. This limit
may be less than the rated movement. Therefore, in the selection of an expansion joint, care must be
exercised to avoid exceeding either of these manufacturer’s limits.”
This CAESAR II computation module is provided to assist the expansion joint user in satisfying these
limitations. This module computes the terms defined in the above equation and the movement of the
joint ends relative to each other. These relative movements are reported in both the local joint
coordinate system and the global coordinate system.
The expansion joint rating module can be entered by selecting Main Menu Analysis - Expansion Joint
Rating option. The user is then presented with two input spreadsheets on which the joint geometry
and end displacements are specified.

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Geometry Spreadsheet

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Displacements and Rotation

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A report displaying both the input echo and the output a calculation is shown as follows. The units
used for the coordinate and displacement values are the length units defined in the active units file.
Rotations are in units of degrees.

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In the previous output, the axial displacement total in the report is the total axial displacement per
corrugation due to axial, lateral, and rotational displacement of the expansion joint ends. This is the
value that would be compared to the rated axial displacement per corrugation. If e(total) is greater
than the rated axial displacement per corrugation, then there is the possibility of premature bellows
failure. Be sure that the displacement rating from the manufacturer is on a per corrugation basis. If not
then multiply the axial displacement total by the number of corrugations and compare this value to the
manufacturer’s allowable axial displacement. Note that most manufacturers allowed rating is for some
set number of cycles (often 10,000). If the actual number of cycles is less, then the allowed movement
can often be greater. Similarly, if the actual number of cycles is greater than 10,000, then the allowed
movement can be smaller. In special situations manufacturers should almost always be consulted
because many factors can affect allowed bellows movement.

The “y” in the report is the total relative lateral displacement of one end of the bellows with respect to
the other, and “theta” is the total relative angular rotation of one end of the bellows with respect to the
other.
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Note that CAESAR II does not include “x” into the denominator for the lateral displacement
calculations as outlined in EJMA.
NEMA SM23 (Steam Turbines)

There are two types of force/moment allowable computed during a NEMA run:

 Individual nozzle allowable.

 Cumulative equipment allowable.

Each individual suction, discharge, and extraction nozzle must satisfy the equation:
3F + M < 500De

Where:
F = resultant force on the particular nozzle.
M = resultant moment on the particular nozzle.
De = effective nominal pipe size of the connection.
A typical discharge nozzle calculation is shown as follows:

For cumulative equipment allowables NEMA SM23 states "the combined resultants of the
forces and moments of the inlet, extraction, and exhaust connections resolved at the centerline of the
exhaust connection", be within a certain multiple of Dc; where Dc is the diameter of an opening whose
area is equal to the sum of the areas of all of the individual equipment connections.

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NEMA Turbine Example

Consider a turbine where node 35 represents the inlet nozzle and node 50 represents the outlet
nozzle.

The output from a CAESAR II analysis of this piping system includes the forces and moments acting on
the pipe elements that attach to the turbine:

NODE FX FY FZ MX MY MZ
30 -108 -49 -93 73 188 603
35 108 67 93 162 -47 -481
50 -192 7 -11 369 -522 39
55 192 -63 11 78 117 -56

To find the forces acting on the turbine at points 35 and 50 simply reverse the sign of the forces that
act on the piping:

LOADS ON TURBINE @ 35 -108 -67 -93 -162 47 481

LOADS ON TURBINE @ 50 192 -7 11 -369 522 -39

Aside from the description, there is only one input spreadsheet for the NEMA turbine. Applied loads
should be entered in global coordinates or extracted directly from the CAESAR II output file (using the
on-screen button). This interface enables iterative addition of arbitrary number nozzles to the model.
To add a nozzle, click the Add Nozzle button.

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NEMA Input Inlet

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NEMA Input Exhaust

The first page of the output is the input echo, the second and some of the remaining pages display the
individual nozzle calculations while, the last page displays the summation calculations.

Note The actual number of output pages will vary and depends on the number of nozzles
defined in the input.

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NEMA Input Echo Report

The NEMA output report for the above turbine example shows that the turbine passed. The highest
summation load is only 56% of the allowable. If the turbine had failed, the symbol **FAILED** would
have displayed, in red, under the “STATUS” column opposite to the load combination that was
excessive.

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API 610 (Centrifugal Pumps)

In August of 1995, API released the 8th edition of API 610 for centrifugal pumps for general refinery
service.
The API 610 load satisfaction criteria are outlined below:
If clause F.1.1 is satisfied, then the pump is O.K. Clause F.1.1 states that the individual component
nozzle loads must fall below the allowable listed in the Nozzle Loadings table (Table 2) shown below

If clause F.1.1 is NOT satisfied, but clauses ARE satisfied then the pump is still O.K.

Clause F.1.2.1 states that the individual component forces and moments acting on each pump nozzle
flange shall not exceed the range specified in Table 2 by a factor of more than 2. Referring to the API
610 report, the user can see if F.1.2.1 is satisfied by comparing the Force/Moment Ratio to 2. If the
ratio exceeds 2, the nozzle status is reported as “FAILING”.

The F.1.2.2 and the F.1.2.3 requirements give equations relating the resultant forces and moments on
each nozzle, as well as on the pump base point respectively. The requirements of these equations, and
whether or not they have satisfied API 610, are shown on the bottom of the report.

The following example is taken from the API 610 code and shows the review of an overhung end-
suction process pump in English units. The three CAESAR II input screens are shown, followed by the
program output.

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API 610 Input Data

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API 610 Suction Nozzle

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API 610 Discharge Nozzle

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API 617 (Centrifugal Compressors)

The requirements of this standard are identical to those of NEMA SM-23 (1991), except that all of the
NEMA allowables are increased by 85%.
API 617 Allowables = 1.85 * NEMA SM-23 Allowables
The input screens for this evaluation are shown below:

API 617 Input

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API 617 Suction/Discharge Input

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API 661 (Air Cooled Heat Exchangers)

This calculation covers the allowed loads on the vertical, co-linear nozzles (item 9 in the figure) found
on most single, or multi-bundled air cooled heat exchangers. The several figures from API 661
illustrate the type of open exchanger body analyzed by this standard

API 661 Input Data

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API 661 Inlet Nozzle Data

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API 661 Outlet Nozzle Data

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Heat Exchange Institute Standard for Closed Feed water Heaters

This module of the CAESAR II Rotating Equipment program provides a method for evaluating
the allowable loads on shell type heat exchanger nozzles. Section 3.14 of the HEI bulletin discusses the
computational methods utilized to compute these allowable loads.
The method employed by HEI is a simplification of the WRC 107 method, in which the
allowable loads have been linear zed to show the relationship between the maximum permitted radial
force and the maximum permitted moment vector. If this relationship is plotted (using the moments as
the abscissa and the forces as the ordinate), a straight line can be drawn between the maximum
permitted force and the maximum permitted moment vector, forming a triangle with the axes. Then
for any set of applied forces and moments, the nozzle passes if the location of these loads falls inside
the triangle. Conversely, the nozzle fails if the location of the loads falls outside the triangle.

The CAESAR II HEI output has been modified to include both the plot of the allowable and the location
of the current load set on this plot.

The HEI bulletin states that the effect of internal pressure has been included in the combined stresses;
however, the effect of the pressure on the nozzle thrust has not. This requires combination with the
other radial loads. CAESAR II automatically computes the pressure thrust and adds it to the radial
force if the Add Pressure Thrust checkbox is
checked.

A sample input for the HEI module is shown below. Note that since the pressure is greater than zero, a
pressure thrust force will be computed and combined with the radial force.

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HEI Nozzle/Vessel Input

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API 560 (Fired Heaters for General Refinery Services)

This module of the CAESAR II Rotating Equipment program provides a method for evaluating the
allowable loads on Fired Heaters. Input consists of the tube nominal diameter and the forces and
moments acting on the tube, as shown in the figure below:

API 560 Input Data

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Volume X Underground (Buried) Piping

Volume-X Underground (Buried) Piping

Underground / buried pipe analysing

Inputs Required for Analysis:

 Buried piping using Caesar II collect the following information from related department
Isometric drawings or GA drawings of the pipeline from Piping layout Department.
 Line parameters (Temperature, Pressure, Material, Fluid Density, etc) from process
Department.
 Soil Properties from Civil Departm
Department.

Modeling of the system:

Model the piping system from isometrics/GA drawings using the pipe parameters.
Normally some part of the system will be above ground and some part will be buried. Let’s take an
example of a typical system for easy understandi
understanding.
ng. Refer Fig 1. The stress system consists of 24 inch
CS pipe connected to tank. The parts inside the rectangle are above ground and remaining parts are
underground.
Create a distinct node at all the junction points of underground and above ground piping.
After you complete your model, save it, close and then enter the buried model by clicking the
Underground Pipe modeler button as shown in Fig.2.

Above ground pipe

Underground pipe

Fig 1

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Fig 2
Once you click on the underground pipe modeler the following screen (Fig. 3) will open. You will find
all your input node numbers listed there

Fig 3

Now your task is to create the soil model and input data received from civil. On clicking Soil
Models button (Highlighted in Fig.3) you will get the window where you have to enter the data. You
have two options to select as soil model type, Americal Lifelines alliance and caesar II Basic Model. We
will use Caesar II basic model for this article. So select Caesar II Basic model. The modeler uses the
values that you define to compute axial, lateral, upward, and downward stiffnesses, along with
ultimate loads. Each set of soil properties is identified by a unique soil model number, starting with the
number 2. The soil model number is used in the buried element descriptions to tell CAESAR II in what
type of soil the pipe is buried. You can enter up to 15 different soil model numbers in any one buried
pipe job. Input the parameters as shown in Fig. 4. If you require to add more soil models simply click
on add new soil model. Overburden compaction factor, Yield displacement factor and thermal
expansion co-efficient will automatically be filled by default. You need to input all other fields.
However, defining a value for TEMPERATURE CHANGE is optional. If entered the thermal strain is
used to compute the theoretical “virtual anchor length”. Leave undrained sheer strength field blank.
After all data has been entered click on ok button.

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Fig 4

Now inform Caesar II about the underground and above ground parts by selecting the nodes and
defining proper soil model number. If you enter 0 as soil model number, the element is not buried. If
you enter 1, then specify the buried soil stiffness’s per length basis in column 6 through 13. (preferable
do not use 1). If you enter a number greater than 1, the software points to a CAESAR II soil restraint
model generated using the equations outlined in Soil Models of Caesar II. Refer Fig. 5 for example.
After all aboveground and underground parts along with proper soil model number are defined click
on convert button and Caesar II will create the underground model.
cLick convert into buried model

Above ground

Buried pipe start

Underground

Buried pipe end

Fig 5
When underground model conversion is over you will get the buried model. By default, Caesar II
appends the name of the job with the letter B. For example, if the original job is named System1, the
software saves the second input file with the name System1B. If the default name is not appropriate,
you can rename the buried job.
In the buried part Caesar II models bi-linear restraints with stiffness values which the software
calculates while conversion into buried model. Refer Fig.6 to check the buried model of the system
shown in Fig.1. These stiffness values depend on the distance between the nodes.
Now open the file (original file appended by B) and perform static analysis in the same conventional
way and qualify the system from code requirements.
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Fig 6

Few Important points to keep in mind:

Typical values of friction angle are as follows:

Clay – 0 o Silt – 26-25 o Sand – 27

27-45

Typical friction coefficient values are:

Silt – 0.4 o Sand – 0.5 o Gravel – 0.6 o Clay – 0.6

The default value of overburden compaction mu multiplier

ltiplier is 8. However this number can be reduced
depending on the degree of compaction of the backfill. Backfill efficiency can be approximated using
the proctor number, defined in most soils text books. Standard practice is to multiple the proctor
number by 8 and use the result as the compaction multiplier.
After entering data in soil model when you click ok, the Caesar II software saves the soil data in a file
with the extension SOI.
During the process of creating the buried model, the modeler removes an any
y restraints in the buried
section. Any additional restraints in the buried section can be entered in the resulting buried model.
The buried job, if it exists, is overwritten by the successful generation of a buried pipe model. It is the
buried job that is eventually run to compute displacements and stresses.
Caesar II removes the density from the buried part model while converting into buried model.

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Ex: 01

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Ex: 02

Data
Pipe Size 4” Sch 40
Insulation Thick 100 mm
Temp 250° Pressure 10 bar
Material SA 106 GrB
Fluid Density 1 sg
Insulation Density 100 kg/m3

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Ex: 03

Data
Pipe Size 4” Sch 40
Insulation Thick 100 mm
Temp 300° Pressure 25 bar
Material SA 106 GrB
Fluid Density 1 sg
Insulation Density 100 kg/m3

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Ex: 04

Data
Pipe Size 6” Sch 40
Insulation Thick 100
mm
Temp 350° Pressure 40
bar
Material SA 106 GrB
Fluid Density 1 sg
Insulation Density 100
kg/m3

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Ex: 05

Data
Pipe Size 6”& 4” Sch 40
Insulation Thick 100 mm
Temp 375° Pressure 60 bar
Material SA 106 GrB
Fluid Density 1 sg
Insulation Density 100 kg/m3

7 to 15 =6”
17 to 22 = 4”

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Ex: 06
Data
Pipe Size 4” Sch 80
Insulation Thick 100 mm
Temp 425° Pressure 90 bar
Material SA 335 P11
Fluid Density 1 sg
Insulation Density 100 kg/m3

Turbine
Fx 5KN
Fy 2KN
Fz 3KN

DX +10 mm
DY +5 mm
DZ -6mm

Header OD 9” Sch 80
Pad Thick 15 mm
Distance to head 2.5 m
Distance to Stiffener 4.5 m
Fx 2KN
Fy 3KN
Fz 2KN

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Ex: 07

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Data
Pipe Size 5” Sch 80
Insulation Thick 100 mm
Temp 425° Pressure 90 bar
Material SA 335 P11
Fluid Density 1 sg
Insulation Density 100 kg/m3

Tank Dia 5 m
Thick 15 mm
Nozzle height 4m
Fluid height 7m
Fx 5KN
Fy 2KN
Fz 3KN

Vessel Dia 3m
Thick 9mm
Pad thick 9mm
Distance to head 2.5 m
Distance to Stiffener 4.5
Fx 2KN
Fy 3KN
Fz 2KN

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Ex: 08

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Data
Pipe Size 6” Sch 120
Insulation Thick 150 mm
Temp 510° Pressure 120 bar
Material SA 335 P12
Fluid Density .5 sg
Insulation Density 100 kg/m3

Turbine
Fx 5KN
Fy 2KN
Fz 3KN

DX +10 mm
DY +5 mm
DZ -6mm

Header OD 12” Sch 120

Pad Thick 22 mm
Distance to head 2.5 m
Distance to Stiffener 4.5 m
Fx 2KN
Fy 3KN
Fz 2KN

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Ex: 09

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Data
Pipe Size 4” Sch 120
Insulation Thick 150 mm
Temp 510° Pressure 120 bar
Material SA 335 P12
Fluid Density .5 sg
Insulation Density 100 kg/m3

Turbine
Fx 5KN
Fy 3KN
Fz 3KN

DX +10 mm
DY -15 mm
DZ -6mm

Pump
Fx 3KN
Fy 3KN
Fz 3KN

DX +10 mm
DY -15 mm
DZ +15mm

The END

Hard Work Never Fails

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