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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
RESTR NODE = 2036 CNODE = 2015 TYPE = -X,Y,Z
RESTR NODE = 3036 CNODE = 3015 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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- 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