Bab 09 Expansion Joints

7/27/2019 Bab 09 Expansion Joints

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Chapter IX Expansion Joints

Training on Caesar II1

BAB IX

EXPANSION JOINT


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9.1 Simple Bellows with Pressure Thrust

- Finite Length Expansion JointKTR=(2/3)(KAX)(D/L)

2

KBEND=(1/2)(KAX)(D2)(p/180)

- Zero Length Expansion Joint

KBEND=(1/8)(KAX)(D2)(p/180)

where :

L : joints flexible length

D : joints effective diameterKAX: joints axial stiffness

*Torsional Stiffness Is Given byThe Vendor


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9.2 Tied Bellows (Simple Model vs. Complex Model)

Simple Model :

- should only be used when the

tie bars are guaranteed to becarrying tension

- used when have nuts on either

side of the flange, and so will

carry compression if needed

- built by entering large axial

stiffness

Complex Model :

- used when the failure is beinginvestigated

- used when the piping diameterand the number of theconvolution became large

- used when nuts are only on the

outside the flange, allowing thetie bars to only carry tension

- Complex model give more goodvalue for the load distribution inthe tie bars.


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9.3Tied Bellows Expansion Joint (Simple Model)

Step 1 :

Need to calculate the lateral

stiffness of the bellows.

For example :

Deff= (4Aeff/p)1/2 = 12 .0 in

KTR= 3/2(KAX)(Deff/L)2

= 3/2(850)(12/12)1/2)

= 1275 lb/in

L = flexible convolution length

= 12 in


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Step 2 :

- Built the CAESAR II modelof the flexible portion of the

expansion joints.

- Note how the rotational

restrain between node 29and 30 keep the flange

parallel.

- The flange and tie bars form

a parallelogram upon lateraldeflection


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Expansion joint

Rigid elements

Tie rod

Joints property

Restrain


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9.5 Universal Expansion Joint (Simple Model)

Nuts on one side of flange only creates atension-only tie bar.


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Equivalent single bellow

lateral stiffness is given

by the manufacturer for

the whole assembly

Rigid element with zero

weight used to keep flange

at 10 and 15 parallel. Node14 restrain to node 15 in

the two bending directions.


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Manufacturers angular spring

rates can be inserted here

Rigid element with zero

weight used to keep flange

at 10 and 15 parallel. Node

14 restrain to node 15 in

the two bending directions.


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9.6 Universal Joint (Comprehensive Tie Rod)

The comprehensive universal joint model involves

defining, as accurate as possible, all tie rod and

connection between tie rods and end plates


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The following groups illustrate the method used in constructing the

universal expansion joint model showed above.

- Rigid Elements (flanges)

15-17/31-33

- Rigid Elements normal to the pipe axis, and between the pipeand the tie bars center line.

At the end where there are nuts on either side of the flange,fixing the tie bar to the flange.

33-1033/33-2033/33-3033

- Rigid Elements Normal to the pipe axis, and between the pipe

and the tie bar center line.At the end where there are nuts only on the back side of theflange

15-1015/15-2015/15-3015


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- Intermediate lateral tee support (rigid)

23-1023/23-2023/23-3023

25-1025/25-2025/25-3025

- Tie Bars

1033-1034-1035-1036

2033-2034-2035-2036

3033-3034-3035-3036

- Restrain with connecting nodes at the tension only flange end

RESTR NODE = 1036 CNODE = 1015 TYPE = -X,Y,Z




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- Restrain with connecting node at the intermediate support points

RESTR NODE = 1035 CNODE = 1023 TYPE = Y, ZRESTR NODE = 2035 CNODE = 2023 TYPE = Y, Z

RESTR NODE = 3035 CNODE = 3023 TYPE = Y, Z

RESTR NODE = 1034 CNODE = 1025 TYPE = Y, ZRESTR NODE = 2034 CNODE = 2025 TYPE = Y, Z

RESTR NODE = 3034 CNODE = 3025 TYPE = Y, Z


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9.7 Universal Joint with Lateral Control

Stops (Comprehensive Tie Rod Model)

- Double-acting restrain with connecting nodes and

gaps are used to model stops gaps along the tie bars.

- Stops along the tie bars are installed to restrict lateral

motion at each end of the universal joint


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Method used in constructing the universaljoint with the lateral stops :

- Standard pipe element : 34-36/36-38- Rigid flange element : 30-32/40-42

- Bellow element : 32-34/38-40

- Rigid element from the pipe to the tie-

bar centerline : 30-1030/36-1036/42-1042

- Tie-bar element : 1003-1002/1002-1001

- Restrain with connecting nodes :

1. RESTR NODE = 1001, CNODE = 1042TYPE = X,Y,Z

2. RESTR NODE = 1002, CNODE = 1036TYPE = Y w/gap = 1.5,X, Z


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9.8 Hinged Joint- The relationship between the rotational bellows stiffness and axialbellows stiffness are approximately :

Kbend = 1/8(KAX)(D2)(p/180)

- This equation should only be used with zero length expansion joint

- The hinged joint is define using a zero length expansion joint withaxial, transverse, and torsional stiffness rigid

- Hinged directions are define using restrain and connecting node

- The restrain line of the action is always normal to the hinge axis

- Hinged joint s are design to take the pressure thrust

- The hinged friction can provide considerable additional resistance tobanding


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Zero length hingedjoint

Pipe elements

Expansion joints

property

Expansion

joint restrain


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9.9 Slotted Hinge Joint (Simple)

Zero lengthhinged joint

Expansion

joint restrain

Expansion joints

property

Weightless

element


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Slotted Hinged

Joint Restrain :

need to provide for

the non hinged axis

rotation due to the

slotted on either

side of the joint

9.10 Slotted Hinged Joint (Comprehensive)


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9.11 Slip Joint

Zero length slip joint

Slip join property

Slip join element


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9.12 Gimbal Join- Gimbal joints are design to resist pressure thrust.-There are two basic type of gimballed expansion join :

1. Those design to make angular deformation only.

2. Those design to make angular deformation and transverse

offset.

- The angular only gimbal can be input as a zero length expansion

joint with rigid axial, transverse, and torsional stiffness. The

bending stiffness is set equal to the rotational stiffness specified in

the manufacturer catalogue.

- Angular and offset gimballed joins are usually installed a large

diameter line where lumped property assumption for the bellows

may not be within reasonable engineering accuracy.


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Gimbal Join

Zero length angular only

gimbaled expansionjoint element

Expansion join property


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Offset

AngularAngular andoffset gimbaljoin restrain


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9.13Dual Gimbal

-Dual gimbal joint are, usuallyangular-only gimbaled joint in seriesin the pipeline to absorb lateral and

possibility axial deformation.

-Each angular-only should be modeled

as zero length expansion joint withrigid axial, transverse, and rotationalstiffness.

-The minimum required distance Lbetween adjacent gimbaled join, is

principally a function of angular androtational deformation to be absorb,diameter, and the number of thenumber of corrugation per joint.


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9.14 Pressure-Balanced Tees and Elbows

- Pressure balanced tees and elbow are used toabsorb axial displacement at a change indirection, without any associated pressure

thrust.- Pressure balanced tees can also be used in

universal type configuration to absorb axialand lateral movement.


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Training on Caesar II

- The example above shows briefly the coding a

pressure-balanced tee in turbine exhaust line.

- The bottom side of the tee in blanked off.- The tee in a standard unreinforced fabricated tee.

- The tie bars will only act in tension

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Bab 09 Expansion Joints