caesar ii-applications guide

Version 5.10 CAESAR II Applications Guide

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Contents

Chapter 1 Introduction 1-1 Overview .................................................................................................................................................. 1-2 Program Support / User Assistance .......................................................................................................... 1-3 COADE Technical Support ...................................................................................................................... 1-4

Chapter 2 Bends 2-1 Bend Definition ........................................................................................................................................ 2-2 Single and Double Flanged Bends or Stiffened Bends ............................................................................. 2-3 180 Degree Return Fitting-To-Fitting 90 Degree Bends .......................................................................... 2-4 Mitered Bends........................................................................................................................................... 2-5 Closely Spaced Mitered Bend................................................................................................................... 2-6 Widely Spaced Mitered Bend ................................................................................................................... 2-8 Elbows - Different Wall Thickness......................................................................................................... 2-11 Bend Flexibility Factor ........................................................................................................................... 2-12

Chapter 3 Restraints 3-1 Anchors..................................................................................................................................................... 3-2 Anchors with Displacements .................................................................................................................... 3-3 Flexible Anchors....................................................................................................................................... 3-4 Flexible Anchors with Predefined Displacements .................................................................................... 3-5 Flexible Nozzle - WRC Bulletin 297........................................................................................................ 3-6 Flexible Nozzle with Predefined Displacements ...................................................................................... 3-8 Flexible Nozzle with Complete Vessel Model.......................................................................................... 3-9 Double-Acting Restraints ....................................................................................................................... 3-13

Double-Acting Restraints - Translational .................................................................................... 3-13 Double-Acting Restraints - Rotational ........................................................................................ 3-13

Single-Directional Restraints .................................................................................................................. 3-15 Guides ..................................................................................................................................................... 3-16 Limit Stops.............................................................................................................................................. 3-18 Windows ................................................................................................................................................. 3-20 Rotational Directional Restraints with Gaps........................................................................................... 3-21 Single-Directional Restraint with Predefined Displacement .................................................................. 3-22 Single-Directional Restraint and Guide with Gap and Predefined Displacement................................... 3-23 Restraint Settlement................................................................................................................................ 3-24 Skewed Double-Acting Restraint with Gap............................................................................................ 3-25 Skewed Single-Directional Restraint ...................................................................................................... 3-27 Restraint Between Two Pipes Using CNodes......................................................................................... 3-28 Restraint Between Vessel and Pipe Models............................................................................................ 3-29 Restraints on a Bend at 45 Degrees ........................................................................................................ 3-30 Restraints on a Bend at 30 and 60 Degrees............................................................................................. 3-31 Vertical Dummy Leg on Bends .............................................................................................................. 3-32

Near/Far Point Method ................................................................................................................ 3-32 On Curvature Method.................................................................................................................. 3-32 Offset Element Method ............................................................................................................... 3-32


2 Contents

Vertical Leg Attachment Angle .............................................................................................................. 3-35 Horizontal Dummy Leg on Bends .......................................................................................................... 3-36 Large Rotation Rods - Basic Model........................................................................................................ 3-37 Large Rotation Rods - Chain Supports ................................................................................................... 3-39 Bi-Linear Restraints ................................................................................................................................ 3-40 Static Snubbers ....................................................................................................................................... 3-42 Plastic Hinges ......................................................................................................................................... 3-43 Sway Brace Assemblies.......................................................................................................................... 3-44

Chapter 4 Hangers 4-1 General Information.................................................................................................................................. 4-2 Simple Hanger Design .............................................................................................................................. 4-3 Single Can Design .................................................................................................................................... 4-4 Constant Effort Support Design................................................................................................................ 4-5 Constant Effort Supports - No Design ...................................................................................................... 4-6 Existing Springs - No Design ................................................................................................................... 4-7 Multiple Can Design................................................................................................................................. 4-8 Old Spring Redesign................................................................................................................................. 4-9 Pipe and Hanger Supported From Vessel ............................................................................................... 4-10 Hanger Design with Support Thermal Movement .................................................................................. 4-11 Hanger Between Two Pipes.................................................................................................................... 4-12 Hanger Design with Anchors in the Vicinity.......................................................................................... 4-13 Hanger Design with User-Specified Operating Load ............................................................................. 4-15 Simple Bottomed Out Spring.................................................................................................................. 4-16 Lift Off Spring Can................................................................................................................................. 4-17 Modeling Spring Cans with Friction....................................................................................................... 4-18

Chapter 5 Expansion Joints 5-1 Simple Bellows with Pressure Thrust ....................................................................................................... 5-2 Tied Bellows - Simple vs. Complex Model .............................................................................................. 5-4 Tied Bellows Expansion Joint - Simple Model......................................................................................... 5-5 Tied Bellows Expansion Joint - Complex Model ..................................................................................... 5-7 Universal Expansion Joints - Simple Models ........................................................................................... 5-9 Universal Joint - Comprehensive Tie Rod.............................................................................................. 5-14 Universal Joint With Lateral Control Stops - Comprehensive Tie Rod Model ...................................... 5-15 Hinged Joint............................................................................................................................................ 5-16 Slotted Hinge Joint - Simple Model........................................................................................................ 5-18 Slotted Hinge Joint - Comprehensive Model .......................................................................................... 5-19 Slip Joint ................................................................................................................................................. 5-20 Gimbal Joints .......................................................................................................................................... 5-22 Dual Gimbal............................................................................................................................................ 5-23 Pressure-Balanced Tees and Elbows....................................................................................................... 5-25

Chapter 6 Miscellaneous Models 6-1 Reducers ................................................................................................................................................... 6-2 Ball Joints ................................................................................................................................................. 6-3 Jacketed Pipe ............................................................................................................................................ 6-4 Cold Spring............................................................................................................................................... 6-6 Connecting Equipment ............................................................................................................................. 6-7

Vertical Vessels ............................................................................................................................. 6-7 Horizontal Vessels....................................................................................................................... 6-12


Contents 3

Chapter 7 Examples 7-1 Example 1 - Harmonic Analysis - TABLE............................................................................................... 7-2

Harmonic Analysis of This System ............................................................................................... 7-4 Example 2 - Relief Valve Loads - RELIEF .............................................................................................. 7-7

CAESAR II Gas Thrust Load Calculations ................................................................................... 7-8 Relief Valve Example Problem Setup ........................................................................................... 7-9

Example 3 - Dynamic Analysis of Water Hammer Loads (HAMMER) ................................................ 7-18 Notes for Analyzing Water Hammer Loads ................................................................................ 7-26 Water Hammer Loading - Output Discussion ............................................................................. 7-28 Problem Solution ......................................................................................................................... 7-30

Example 4 - Dynamic Analysis of Independent Support Earthquake Excitation (CRYISM)................. 7-31 Cryogenic Piping Dynamics Example......................................................................................... 7-32 Discussion of Results................................................................................................................... 7-44

Example 5 - Structural Analysis - FRAME ............................................................................................ 7-46 Example 6 - Dynamic Analysis - NUREG9 ........................................................................................... 7-57

NRC Example NUREG 9 ............................................................................................................ 7-57 Example 7 - Omega Loop Modeling - OMEGA..................................................................................... 7-65 Example 8 - Jacketed Piping - JACKET................................................................................................. 7-71

Step 1 - Create Modeling Plan..................................................................................................... 7-72 Step 2 - Node Layout................................................................................................................... 7-73 Step 3 - Core Piping Input ........................................................................................................... 7-75 Step 4 - Jacket Input - 1st Half .................................................................................................... 7-75 Step 5 - Jacket Input - 2nd Half ................................................................................................... 7-78

Example 9 - WRC 107............................................................................................................................ 7-81 Converting Forces/Moments in the CAESAR II Global Coordinates to WRC 107 Local Axes ............ 7-83 Example 10 - NEMA SM23 ................................................................................................................... 7-92

NEMA Example PT69M............................................................................................................. 7-92 Nozzle Results for PT69M .......................................................................................................... 7-94 Nozzle Load Summation Report ................................................................................................. 7-96

Chapter 8 Tutorial A 8-1 System Overview...................................................................................................................................... 8-2

Preparing the Drawing................................................................................................................... 8-4 Generating CAESAR II Input........................................................................................................ 8-6 Input Review ............................................................................................................................... 8-20 Ending the Input Session ............................................................................................................. 8-24 Performing the Static Analysis .................................................................................................... 8-24

Reviewing the Static Results .................................................................................................................. 8-26 Static Analysis Output Listing..................................................................................................... 8-30

Conclusions............................................................................................................................................. 8-38

Chapter 9 Tutorial B 9-1 Evaluating Pump Discharge Loads........................................................................................................... 9-2 Creating Accurate Models ...................................................................................................................... 9-10 WRC 297 Calculations Completed at End of Error Checking................................................................ 9-13 Checking Nozzle Loads .......................................................................................................................... 9-18 System Redesign..................................................................................................................................... 9-22 Conclusion .............................................................................................................................................. 9-31


Chapter 1 Introduction

This chapter discusses the organization of the manual and important information regarding user assistance.

In This Chapter Overview ................................................................................................. 1-2 Program Support / User Assistance ......................................................... 1-3 COADE Technical Support ..................................................................... 1-4

C H A P T E R 1


1-2 Introduction

Overview The CAESAR II Applications Guide is intended to serve as an example guide, showing the application of CAESAR II. Users should refer to this manual for examples of specific piping components, as well as complete example jobs.

Chapters 2 through 6 of this manual illustrate the techniques and methods used to model individual piping components, restraints, and attached equipment. These chapters should be referenced often when modeling seldom-used components or unusual geometries. Users should recognize that the numeric data used in these examples is not necessarily applicable in all cases. In general, the numeric values used in these examples are fictitious quantities, unless otherwise noted.

Chapter 7 is a chapter of worked examples, illustrating the application of CAESAR II to various piping problems. These examples illustrate modeling, problem solving, and program operation.

Chapters 8 and 9 contain a tutorial that walks users through the modeling and analysis of a complete system.

Users are encouraged to work through these chapters, especially if a particular analysis has not been previously attempted. The component modeling examples in Chapters 2 through 6 are especially useful, for both modeling techniques and general program understanding. The examples in Chapter 7 also provide engineering guidelines and indicate where assumptions must be made in attempting to solve real-world problems.


Chapter 1 Introduction 1-3

Program Support / User Assistance COADEs staff understands that CAESAR II is not only a complex analysis tool but also, at times, an elaborate processone that may not be obvious to the casual user. While our documentation is intended to address questions regarding piping analysis, system modeling, and results interpretation, not all the answers can be quickly found in these volumes.

COADE understands the engineers need to produce efficient, economical, and expeditious designs. To that end, COADE has a staff of helpful professionals ready to address any CAESAR II and piping issues raised by users. CAESAR II support is available by telephone, e-mail, fax, and the Internet; literally hundreds of support calls are answered every week. COADE provides this service at no additional charge to the user. It is expected, however, that questions focus on the current version of the program.

Formal training in CAESAR II and pipe stress analysis is also available from COADE. COADE schedules regular training classes in Houston and provides in-house and open attendance training around the world. These courses focus on the expertise available at COADE modeling, analysis, and design.


1-4 Introduction

COADE Technical Support Phone: 281-890-4566 E-mail: [email protected]

Fax: 281-890-3301 WEB: www.coade.com


Chapter 2 Bends

This chapter illustrates the modeling techniques for various bend techniques in CAESAR II.

In This Chapter Bend Definition ....................................................................................... 2-2 Single and Double Flanged Bends or Stiffened Bends ............................ 2-3 180 Degree Return Fitting-To-Fitting 90 Degree Bends ......................... 2-4 Mitered Bends.......................................................................................... 2-5 Closely Spaced Mitered Bend.................................................................. 2-6 Widely Spaced Mitered Bend .................................................................. 2-8 Elbows - Different Wall Thickness ......................................................... 2-11 Bend Flexibility Factor ............................................................................ 2-12

C H A P T E R 2


2-2 Bends

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 mid-point (M).

For stress and displacement output the 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 ( / 2)

where 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 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-SetupGeometry 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 SetupGeometry section.


Chapter 2 Bends 2-3

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.

Flanged Bends


2-4 Bends

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) bend.

The user is recommended to put nodes at the mid point of each bend comprising the 180 degree return. (See the example below.)

180 Degree Bend

DX = 2R


Chapter 2 Bends 2-5

Mitered Bends Evenly spaced mitered bends, whether closely or widely spaced, are uniquely defined by two parameters:

Number of cuts (changes in direction) Equivalent radius miter spacing.

For closely spaced miters the equivalent radius is equal to the code defined R1 for B31.3 and R for B31.1. The equation relating the equivalent radius to the spacing for evenly spaced miters is:

Req = S / [ 2 tan() ]

Where:

Req - equivalent miter bend radius

S - spacing of the miter cuts along the centerline

- code defined half-angle between adjacent miter cuts:

= / 2N

Where:

- total bend angle

N - number of cuts

An additional parameter B (length of miter segment at crotch) is checked for closely spaced miters when using B31.1. B may be found for evenly spaced miters from:

B = S [ 1 - ro / Req ]

Where:

ro - outside radius of pipe cross-section.


2-6 Bends

Closely Spaced Mitered Bend Miter bends are closely spaced if:

S < r [ 1 + tan () ]

Where:

S - miter spacing

r - average pipe cross section radius: (ri+ro)/2

- one-half the angle between adjacent miter cuts.

B31.1 has the additional requirements that:

B > 6 tn

22.5 deg.

B - length of the miter segment at the crotch.

tn - nominal wall thickness of pipe.

Closely spaced miters regardless of the number of miter cuts may be entered as a single bend. CAESAR II will always calculate the spacing from the bend radius. If the user has the miter spacing and not the bend radius, the radius must be calculated as shown below.

The mitered bend shown below has 4 cuts through 90 degrees and a spacing of 15.913 in.

Req = S / [ 2 tan () ]

= / 2N

= 90 / [2(4)]

= 11.25 deg.

Req = 15.913 / [2 tan (11.25 deg.)]

= 40


Chapter 2 Bends 2-7

Closely Spaced Miter Bend


2-8 Bends

Widely Spaced Mitered Bend Mitered bends are widely spaced if:

S r * [1 + tan ()]

S - spacing between miter points along the miter segment centerline.

r - average cross section radius (ri+ro)/2

- one-half angle between adjacent miter cuts.

B31.1 has the additional requirement that:

22.5 deg.

In CAESAR II, widely spaced miters must be entered as individual, single cut miters, each having a bend radius equal to:

R = r [1 + cot ()] / 2

R - reduced bend radius for widely spaced miters.

During error checking, CAESAR II will produce a warning message for each mitered component, which does not pass the test for a closely spaced miter. These components should be re-entered as a group of single cut joints

Widely Spaced Miter

Pipe O.D. = 10.375 in.

Pipe Thk. = 0.500 in.

Bend Angle = 90

Cuts = 2

Req = 45 in.

Assuming closely spaced:

= /2 =90/(22) =22.5 deg.

S = R [2tan(Q)]eq

= 45[2tan(22.5)]

= 37.279 in.

Now check s r [1+tan(Q)]2r [1+tan(Q)] = 4.9375[1+ tan(22.5)] = 6.9826 in.237.279>6.9826 The miter is widely spaced.


Chapter 2 Bends 2-9

Widely Spaced Miter

Calculate the coordinates to get from the tangent intersection point of the single cut miter bend at node 10 to the single cut miter bend at node 15.

Note: The straight pipe section coming into and going out of the bend must be Reqsin ( ).

( )

2rR = [1+cot(Q)]

2

4.9375= [1+cot(22.5)]2

= 8.4288 in.

DX = Scos(45)

= 37.279cos(45)

= 26.360 in.

DY = Ssin(45)= 37.279sin(45)= 26.360 in.


2-10 Bends

Widely Spaced Miters ... Continued

Input widely spaced miters as individual straight pipe elements, with bends specified, having one miter cut.

Coming up to the first cut. Between the first and second cuts.

Coming out of the second cut.


Chapter 2 Bends 2-11

Elbows - Different Wall Thickness When the fitting thickness in the bend auxiliary field is entered, CAESAR II changes the thickness of the curved portion of the bend element only. The thickness of any preceding or following straight pipe is unaffected.

The specified fitting thickness applies for the current elbow only and is not carried on to any subsequent elbows in the job.

Stresses at the elbow are calculated based on the section modulus of the matching pipe as specified in the B31 codes. However, stress intensification factors and flexibility factors for the bend are based on the elbow wall thickness.

Thick Elbow

Note: The elbow at 10 has a thickness larger than the matching pipe wall. The matching pipe has a thickness of 0.5.


2-12 Bends

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.


Chapter 3 Restraints

This chapter details the modeling of various restraint types in CAESAR II.

In This Chapter Anchors.................................................................................................... 3-2 Anchors with Displacements ................................................................... 3-3 Flexible Anchors...................................................................................... 3-4 Flexible Anchors with Predefined Displacements ................................... 3-5 Flexible Nozzle - WRC Bulletin 297....................................................... 3-6 Flexible Nozzle with Predefined Displacements ..................................... 3-8 Flexible Nozzle with Complete Vessel Model ........................................ 3-9 Double-Acting Restraints ........................................................................ 3-13 Single-Directional Restraints ................................................................... 3-15 Guides...................................................................................................... 3-16 Limit Stops .............................................................................................. 3-18 Windows.................................................................................................. 3-20 Rotational Directional Restraints with Gaps............................................ 3-21 Single-Directional Restraint with Predefined Displacement ................... 3-22 Single-Directional Restraint&GuidewithGap&Predefined Displacement3-23 Restraint Settlement................................................................................. 3-24 Skewed Double-Acting Restraint with Gap............................................. 3-25 Skewed Single-Directional Restraint ....................................................... 3-27 Restraint Between Two Pipes Using CNodes.......................................... 3-28 Restraint Between Vessel and Pipe Models............................................. 3-29 Restraints on a Bend at 45 Degrees ......................................................... 3-30 Restraints on a Bend at 30 and 60 Degrees.............................................. 3-31 Vertical Dummy Leg on Bends ............................................................... 3-32 Vertical Leg Attachment Angle............................................................... 3-35 Horizontal Dummy Leg on Bends ........................................................... 3-36 Large Rotation Rods - Basic Model ........................................................ 3-37 Large Rotation Rods - Chain Supports .................................................... 3-39 Bi-Linear Restraints................................................................................. 3-40 Static Snubbers ........................................................................................ 3-42 Plastic Hinges .......................................................................................... 3-43 Sway Brace Assemblies........................................................................... 3-44

C H A P T E R 3


3-2 Restraints

Anchors The following are general guidelines and information concerning anchors:

The anchor default stiffness for translational and rotational degrees of freedom is defined in the Configuration file. Connecting nodes can be used with anchors to rigidly fix one point in the piping system to any other point in the piping

system. Entries in the Stif field apply to all 6 anchor degrees of freedom. Displacements should not be specified at an anchor. If the displacements of a particular point are known, they should be

input directly without any additional restraints or anchors. Accurate input of the piping boundary conditions (i.e. restraints) is probably the single most important part of system

modeling, requiring experience both with piping fabrication and erection, and with CAESAR II.

The first group of examples illustrates a large number of boundary condition applications and their proper modeling using CAESAR II.

Rigid Anchor at Node 5

Nozzle Connection Modeled As Anchor

Rigid Anchor Input


Chapter 3 Restraints 3-3

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.

Note: Degrees of freedom not defined (left blank) in any displacement vector are assumed to be free in all load cases.

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.

The translations and/or rotations for any nodal degree of freedom having displacements specified in any displacement vector will be zero for load cases not containing that vector as part of the load case identification, and the specified non-zero value for load cases containing the vector as part of the load case identification. For instance, defined displacements are used if the load case is W+P1+T1+D1 (OPE) and those displacements are held to zero if the load case is W+P1 (SUS).

Once a degree of freedom has been fixed in one displacement vector, it cannot be free in another displacement vector at the same node (leaving a displacement field blank will default to zero in this case).

Anchors with Predefined Displacements

Predefined Displacements on an Anchor

Anchor Displacement


3-4 Restraints

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.

Flexible Restraints for Nozzle and Shell



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.

Flexible Anchors with Predefined Displacements

The connecting node here is 1005. Connecting node numbers may be selected at the user's convenience, but must be unique.


3-6 Restraints

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.

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.

Schematic of Nozzle and Vessel to be Modeled Using WRC 297



WRC 297 Input Example

WRC 297 Output Example


3-8 Restraints

Flexible Nozzle with Predefined Displacements Follow these guidelines to model flexible nozzles with predefined displacements (WRC 297):

Define a unique vessel node on the Nozzle spreadsheet. Apply the predefined displacements to the vessel node.

Note: These displacements can be given on any element spreadsheet (the displacement node does not need to be on an element that defines it).

The CAESAR II generated nozzle/vessel flexibilities will be inserted in restraints that act between the nozzle node and the vessel node.

Flexible Nozzle With Predefined Displacements

Displacements Defined on Vessel Node



Flexible Nozzle with Complete Vessel Model Follow these guidelines for modeling a flexible nozzle that includes a complete vessel:

Define a unique vessel node on the Nozzle Spreadsheet. Run a rigid element between the vessel node defined on the Nozzle Spreadsheet and the centerline of the vessel. The

outside diameter of the rigid element should be approximately equal to the outside diameter of the vessel. The weight of the rigid element should be zero.

Model the actual vessel length using pipe elements. The vessel diameter and wall thicknesses should be modeled as accurately as possible

Use an anchor to model the vessel anchorage point.

The CAESAR II generated nozzle/vessel flexibilities will be inserted between the nozzle node and the vessel node.

Full WRC 297 Model Schematic


3-10 Restraints

Full WRC 297 and Vessel Model

Pipe Entering Nozzle WRC 297 Auxiliary Input



Full WRC 297 and Vessel Model Continued ...

Vessel Radius Element

Rigid Weight is Blank ( 0.0)

Vessel Element Vessel Skirt Element At Ambient Temperature


3-12 Restraints

WRC 297 Results Found At End Of Error Checking



Double-Acting Restraints Double-acting restraints are those that act in both directions along the line of action. Most commonly used restraints are double-acting.

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.

If a gap is specified, it is the amount of free movement along the positive or negative line of action of the restraint before resistance to movement occurs. A gap is a length, and so is always positive.

Double-Acting Restraints - Translational Restraint acts along both the positive and negative directions. Friction at double-acting restraints acts orthogonally to the line of action of the restraint.

Double - Acting Restraint at Node 55 in the Z Direction

Schematic

Input

Double-Acting Restraints - Rotational The behavior of these restraints is similar to double-acting translational restraints.


3-14 Restraints

Friction is not defined for rotational restraints.

Hinged-End Rod Free to Rotate About the Z-Axis

Restrain all except Rz

Four restraints on element spreadsheet containing node 105 and remaining restraint on next spreadsheet.



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. The gap is in the opposite direction of the free travel.

Rigid Single - Directional Restraint in Y at Node 20

The sign on the restraint gives the direction of free movement. Since the stiffness is omitted, the restraint will be rigid.


3-16 Restraints

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

Guides are double-acting restraints with or without a specified gap. Connecting Nodes (CNodes) can be used with guides. 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 on Horizontal Pipe with Single Directional Restraint

Node 25 is guided in Z with a gap of 2.5 in. A single directional restraint in the Y direction also exists. Both restraints are rigid.

Note: In this example, replacing the guide restraint with a Z- restraint is equivalent.



Guided Pipe in Both Horizontal and Vertical Directions


3-18 Restraints

Limit Stops The following are important facts pertaining to Limit Stops:

Limit stops are single- or double-acting restraints 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 the

restraining line of action. 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. The gap direction is opposite the direction of free travel. 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. CAESAR II computes direction cosines for orthogonal or skewed limit stops. Limit Stop direction cosines entered by the

user are ignored.

Directional Limit Stop with a Gap



Two Limit Stops Acting in Opposite Directions

The stop at 45 permits unlimited free movement in the plus X direction, and 1.0 in. of free movement in the minus X direction before the Limit Stop becomes active.

The stop at 195 permits unlimited free movement in the minus X direction, and 1.0 in. of free movement in the plus X direction


3-20 Restraints

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.

Window Modeled with Four Single Directional Restraints with Gaps



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

Rotational Directional Restraints

Bi-Directional Rotational Restraint with Gap

Allowable rotation of 5 degree in either direction about the Z-axis before resistance to rotation is encountered.

Hinge Assembly with Directional Rotational Restraint

Hinge Assembly at node 50 can rotate relative to assembly at node 55 only in the positive direction about the Z-axis.


3-22 Restraints

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 with Predefined Displacement

Piping at node 55 rests on top of the restraint that is displaced in the Y-direction, simulated by node 1055.



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 node number should be entered in both CNode fields. Specify the predefined displacements for the CNode.

Guide Plus Single-Directional Restraint with Predefined Displacement

Guided piping at node 70 rests on a structural member node 1070. The structure undergoes a predefined displacement.

Note: In the example above, ignoring other loads that may be acting on the pipe, the .25 inch gap will be closed in the -X direction, and the pipe will have a displacement of 0.50 inches in +X direction.


3-24 Restraints

Restraint Settlement Keep in mind the following facts when modeling restraint settlement:

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 Operating Load Case is used to include the effect of settlement. 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. Settlement is considered as an EXP load with a half-cycle.

Restraint Settlement

The weight of this pipe at node 95 exerts a sufficient load on the foundation node 1095 to cause a calculated .325 in. settlement.



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 (DX, 0, -DZ).

Skewed Double-Acting Restraint with Gap

Double Acting Restraint Y, Guided @ 45 Deg.


3-26 Restraints

Skewed Double-Acting Restraint with Gap Continued ...

Input Using Unit Direction Vectors Input Using Direction Cosines

Input Using Perpendicular Vector Input Using Guide Restraint Type



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.) Direction cosines may be quickly checked in the graphics processor. Connecting nodes (CNode) can be used with any skewed single-directional restraint.

Skewed Single-Directional Restraint


3-28 Restraints

Restraint Between Two Pipes Using CNodes

Note For these two examples, the directive Connect Geometry Through CNodes must be disabled to avoid plotting and geometry errors.

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.

Nonlinear Restraint Between Two Pipes

Rigid Rod Hanger Between Two Pipes



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.

Restraint Between Vessel and Piping


3-30 Restraints

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 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 arm (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.

90 Degree Bend Restrained at Midpoint



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.

Restraints on Intermediate Points Along a Bend


3-32 Restraints

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

Offset Element Method Difficult input Dummy leg acts at the proper place on the bend curvature Dummy leg acts along centerline of vertical run

Note: 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 legs 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.

Vertical Dummy Leg on Bend

The bend shown is entered from the top left corner of the control station nodes 80 to 85, and exits horizontally to the right nodes 85 to 90. The dummy leg is attached near the 45-degree point on the bend, and the centerline of the dummy leg should line up with the centerline of the vertical run of pipe.

Note: Coding the bend is the same for all 3 methods except alpha is not required for the Near/Far Point Method.


3-34 Restraints

Dummy Leg on Bend Continued ...

Near Point Method

Dummy Leg length is equal to the distance from its base to the bend tangent intersection point plus the bend radius.

On Curvature Method

Calculate from the relation shown on the following page. Input on the bend specification instead of the midpoint. Calculate the offset distance y = R(1-sin). Add the distance y to the dummy leg length.

Offset Element Method

Calculate and the offset distance x and y from the figure on the following page. Add x and y to the dummy leg length. Activate the offsets to subtract them from the dummy leg.



Vertical Leg Attachment Angle

Dummy Leg Attachment Angle Calculation

= R (1 - sin )


3-36 Restraints

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.

Horizontal Dummy Leg on Midpoint of Bend

The dummy leg id defined as a zero weight rigid supported on one end by a spring can.



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.


3-38 Restraints

In the example below, the rod pivots about the structural steel support. There is a very short swing arm, and so even a small amount of horizontal movement will produce a relatively large swing. In the output report for this restraint, the user will see X and Y direction loads.

Large Rotation Rods



Large Rotation Rods - Chain Supports In the model below, the user wants the large rotation swing only in the plane of the chain support (the Y-Z 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.

Chain Supports


3-40 Restraints

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.

Characteristics of Bi-Linear Supports



Pipe in a Trench Bi-Linear Restraint Modeling

Estimated Stiffness Models

Estimated Lateral Stiffness: 60,000lb/in. Estimated Vertical Stiffness: 533,333 lb/in.


3-42 Restraints

Static Snubbers Static snubbers are translational restraints designed to provide resistance to dynamic loads such as seismic and wind. Snubbers are activated in the Load Case Editor under the Load Case Options tab by checking the Snubbers Active check box for the appropriate load case, which contains an occasional load. In the figure below snubbers will be active in load case L2 to restrain the pipe against the uniform load.

Load Case Options Tab

Static snubbers (or static analysis snubbers) have SNB following a translational direction in the restraint Type field.

When a snubber is entered, the restraint fields change as follows: Gap and Mu are disabled.

Static snubbers may be directional, i.e. may be preceded by a plus or minus sign. To model static snubbers follow the steps below.

Modeling Static Snubbers 1 Run the OPErating case without defining a snubber.

2 Note the displacements, in all six degrees of freedom at each snubber location.

3 From INPUT/PIPING add each snubber with a distinct CNode.

4 Place displacements, from step 1 above, on all snubber CNodes.

5 Modify the load cases by including D1 everywhere T1 displays.

6 Activate snubbers in the Load Case Editor for all load cases containing occasional loads.



Plastic Hinges The steps in setting up a plastic hinge are illustrated below. The leg from A to B is overheated, causing bending of the B-D support leg. This example models the plastic deformation at cross-section E-E. The plastic hinge is formed between the nodes 10 and 15. The expansion joint is used to provide translational and torsional rigidity at the plastic hinge junction. Two bi-linear supports are used to model rigid resistance to bending until a breakaway force (yield force) is exceeded at which point bending is essentially free.

Plastic Hinge in a Support Leg*

The Yield Force is determined from

Fy = SyZ(SF)

Where,

Sy is the yield stress

Z is the section modulus

SF is the safety factor

* The plastic hinge is modeled as a zero length expansion joint with rotational bi-linear restraints.


3-44 Restraints

Sway Brace Assemblies The sway brace is commonly used to allow unrestrained thermal movements while tuning the system dynamically to eliminate vibration. In this respect sway brace resembles a spring: it may be pre-loaded in the cold (installed) position, so that after pipe thermal growth it reaches the neutral position and the load on the system in the operating condition is zero or negligible.

The sway brace is composed of a single compression spring enclosed between two moveable plates. The spring is pre-compressed a full inch providing an initial force that instantaneously opposes vibration. Any movement from the sway brace neutral position is opposed by a load equal to the pre-load plus travel from neutral position times the sway brace spring constant. Once maximum allowed travel (usually 3-in. in either direction) is reached the sway brace locks preventing additional movement.

Manufacturers typically recommend a specific size sway brace for a given pipe nominal diameter.

A more specific sway brace selection is possible when the exact restraining force required to control the piping vibration is known. The energy necessary to control the piping is proportional to the mass, amplitude of movement, and the force causing the vibration. From this relation the exact restraining force required to control the piping vibration may be calculated and an appropriate sway brace size selected.

Once selected, the sway brace may be modeled in CAESAR II using a combination of a bi-linear restraint and a translational restraint:

In the event that the sway brace is to be installed in the operating condition (or the neutral position is to be adjusted in the operating position), the modeling is CAESAR II is a little more complex. In this case, before modeling the sway brace, you must analyze the piping system without the sway brace to obtain displacements from the cold to neutral operating position:

Run analysis on the system without the sway brace to obtain the displacements from cold to operating condition. For the sake of this example, lets assume the CAESAR II calculated displacement from cold to operating position is 0.5 in.

In the SUS case the displacement D2 (vector 2) represents the pre-load in cold position. Under shutdown conditions, the pipe returns to its cold position and the brace exerts a force as previously described.

Sustained case restraint loads on sway brace = Pre-Load + Hot Deflection * Spring Rate

In OPE the displacement allows thermal expansion and the sway assumes neutral position exerting zero or negligible load on the pipe.

Operating case restraint loads on sway brace =~ 0.0 (does not restrain thermal expansion)



Sway Brace Installed in Operating Condition

Sway brace opposing compression force (movement occurs after pre-load is overcome).

Spring Rate: 150 lb./in.

Initial Loading: 150 lb.

Allowed Movement: 3 in.

Calculated Displacement: .5 in

Note: Be sure to include D2 in the sustained and operating cases.


Chapter 4 Hangers

This chapter demonstrates methods for incorporating spring hanger design into CAESAR II models.

In This Chapter General Information................................................................................. 4-2 Simple Hanger Design............................................................................. 4-3 Single Can Design ................................................................................... 4-4 Constant Effort Support Design............................................................... 4-5 Constant Effort Supports - No Design ..................................................... 4-6 Existing Springs - No Design .................................................................. 4-7 Multiple Can Design................................................................................ 4-8 Old Spring Redesign................................................................................ 4-9 Pipe and Hanger Supported From Vessel ................................................ 4-10 Hanger Design with Support Thermal Movement ................................... 4-11 Hanger Between Two Pipes..................................................................... 4-12 Hanger Design with Anchors in the Vicinity........................................... 4-13 Hanger Design with User-Specified Operating Load .............................. 4-15 Simple Bottomed Out Spring................................................................... 4-16 Lift Off Spring Can.................................................................................. 4-17 Modeling Spring Cans with Friction ....................................................... 4-18

C H A P T E R 4


4-2 Hangers

General Information Select MODELHANGER DESIGN CONTROL DATA from the menu on the Input Spreadsheet to enter parameters affecting hanger design throughout the model. The hanger control spreadsheet items, with default values, are shown below. Complete descriptions of each item can be found in the Technical Reference Manual. These items can greatly affect the hangers designed and should be reviewed carefully at least one time so that the user is aware of the capability available.

Whenever CAESAR II designs a zero load constant effort support, a proposed spring location is found to be holding the pipe down at that point. In this case, that hanger location is removed from the analysis, and the restrained weight case is rerun to redistribute the weight loads.

There are instances where the stiffness of the adjacent piping and the hanger location restraints in the restrained weight case unfavorably interact, producing an undesirable distribution of loads. Often reducing the stiffness used to compute the hanger loads in the restrained weight run can eliminate these load distribution problems. The default for this stiffness is 1.0E12. Values on the order of 50,000 or 75,000 have been used successfully to relax the system somewhat and redistribute these piping loads. This stiffness can be changed through the Computation Control tab of the Configuration/Setup item of the Main Menu.

The operating case for hanger travel (free thermal case) can be analyzed either with no spring stiffness at the hanger locations, or with the stiffness of the selected springs inserted at those locations (in the latter case, the springs are selected through an iterative process). This is controlled via the Include Spring Stiffness in Hanger OPE Travel Cases option of the Configuration/Setup item of the Main Menu. Inserting the actual hanger stiffness into the Operating Case for Hanger Travel may give a technically more accurate result, but may introduce convergence problems as well. Also, please note that in the latter case, it is very important that the hanger load in the cold case (in the physical system) be adjusted to match the reported hanger Cold Load.


Chapter 4 Hangers 4-3

Simple Hanger Design Double-click the Hanger check box on the pipe spreadsheet to enter the spring hanger data for a particular node.

For a simple hanger no additional input is required also, a number of the parameters from the Hanger Control sheet also display on the individual hanger auxiliary data fields. These items may be set globally (in hanger control) for all springs, or overridden locally (on each hanger auxiliary data area).

Simple Hanger Design


4-4 Hangers

Single Can Design Entering a negative number in the Available Space field on the Hanger spreadsheet indicates that the pipe is supported from below. The magnitude of the number in the Available Space field represents the distance between the pipe support and the concrete foundation, or baseplate. See the Technical Reference Manual for each of the manufacturer's definitions of available space. If the available space is not really a criteria in the hanger design, then input a large negative value (i.e. -1000).

CAESAR II input plots will use a different symbol for these base supports.

Design of Single Can at One Node



Constant Effort Support Design Design a constant effort support by specifying a very small allowable travel. A typical value used is (0.001 in.).

Design of Constant Effort Support Design


4-6 Hangers

Constant Effort Supports - No Design

Entering Constant Effort Support Data: 1 Enter the constant effort support load (per hanger) in the Predefined Hanger Data field.

2 Enter the number of constant support hangers at the location. Tip: Do not enter the spring rate or theoretical cold load.

The hanger design algorithm will not design hangers that are completely predefined.

Multiple Predefined Constant Effort Supports

The two constant effort supports at node 377 should carry 10484 lbs. each.

Note: Any other data entered on this Hanger spreadsheet will be ignored.



Existing Springs - No Design

Entering Existing Spring Data: 1 Enter the Spring Rate and the Theoretical Cold Load (installation load, on a per hanger basis) in the Predefined

Hanger Data fields.

2 Enter the number of Variable Support Hangers at the location.

The hanger design algorithm will not design hangers that are completely predefined. Any other data can exist for the spring location but this data is not used. Entered spring rates and theoretical cold loads will be multiplied by the number of hangers at this location. CAESAR II requires the Theoretical Cold (Installation) Load to pre-define the spring. Theoretical Cold Load = Hot Load + Travel * Spring Rate, where upward travel is positive.

Predefined Spring Hanger

Hot Load = 2000 lb.

Cold Load = 2000 lb. + abs(1.375*590)

= 2811 lb.


4-8 Hangers

Multiple Can Design Enter the number of hangers or cans as a positive number in the No. of Hangers at Location field.

Tip: Placing a negative number in that field allows CAESAR II to design up to that number of hangers at the location.

All other hanger design parameters are still active.

Trapeze Hanger Assembly

Power Piping Springs

Allowable Load Variation:15%

Rigid Support Displacement Criteria: 0.05 in.

Note: The program designs up to 3 cans at the support if the load is too high for a single or double can configuration.



Old Spring Redesign This option is used to determine if the old spring can still be used. If the old spring can be used then the new preset (initial cold load) is determined. If the old spring cannot be used then a new spring design is recommended. The old spring is always left in the problem for subsequent load case analysis. The old hanger information needed for the re-design is

The hanger table The number of springs at the location The old spring rate

The old spring rate is entered in the Spring Rate field under Predefined Hanger Data. The Theoretical Cold Load must not be specified.

Old Spring Design

3 springs at node 97 and each have a spring rate of 1105 lb./in.


4-10 Hangers

Pipe and Hanger Supported From Vessel Connecting nodes associated with hangers and cans function just like connecting nodes with restraints. Connecting nod

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