Expansion Joints in Piping Systems
© Intergraph 2014
Quick Agenda







Introduction
Review of Expansion Joint Assemblies
Selecting and Locating the Appropriate Joint Assembly
Calculating XJ Demand
Modeling Details
Evaluating the Joint
Closing Points
© Intergraph 2014
Purpose/Advantages



Expansion joints provide flexibility in a very small package
They can also provide isolation from mechanical vibration
What size Mechanical Hard Pipe Loop would provide the same
flexibility as an expansion joint (indicated below, ignoring the guides and
anchor loads)?
 39’ of Pipe
 4 Elbows
 6+ Welds
© Intergraph 2014
Purpose/Advantages



Expansion joints provide flexibility in a very small package
They can also provide isolation from mechanical vibration
What size Mechanical Hard Pipe Loop would provide the same
flexibility as an expansion joint (indicated below, ignoring the guides and anchor loads)?
Pump with Loop
Pump with XJ




© Intergraph 2014
Disadvantages

Yielding occurs with every cycle!



Requires additional hardware





Low Cycle Life Fatigue – expansion joints are rated for 2000 cycles
Failure due to “unanticipated” through-the-wall crack
Control Pressure Thrust, Control Pressure Thrust
Guides to direct thermal growth
Corrosion, the most common failure, is addressed by material selection
Cost (TH10_Pipe Loop or Expansion Joints.pdf by SENIOR FLEXONICS PATHWAY)
Horror stories such as the Flixborough Disaster


1974 UK piping failure & explosion that killed 28 workers & resulted in
widespread damage.
Temporary 20 inch bypass line with expansion joints failed due to its
unsatisfactory design.


Dog leg layout
No pressure thrust control
© Intergraph 2014
Disadvantages
© Intergraph 2014
A review of Expansion Joint
Assemblies (in CAESAR II)

Assemblies with no integral pressure control



Assemblies with pressure control





Single Expansion Joint
Untied Universal Expansion Joint
Single, Tied Expansion Joint
Hinged Expansion Joint
Gimbaled Expansion Joint
Tied Universal Expansion Joint
Other configurations


Swing Expansion Joint
Pressure-balanced Expansion Joint
© Intergraph 2014
Single Untied Expansion Joint

A single joint represents the simplest assembly, no restrictions on its
motion in any of the six degrees of freedom are present (body is free to move
forward/backward, up/down, left/right (translation in three perpendicular axes) combined with
rotation about three perpendicular axes, often termed pitch, yaw, and roll.)


There is No means to contain Pressure Thrust
In exchange for providing the most freedom, this joint requires special
care attention.



piping around the joint must be well guided to prevent any squirm in the
joint that would be further aggravated by Pressure Thrust.
axial stops or anchors are required upstream and downstream to absorb
the pressure thrust load.
So with all the freedom in this joint, the pressure containment
requirements reduce its flexibility (in most applications) to only the axial
direction or very low pressure systems.
© Intergraph 2014
Single Untied Expansion Joint

A Double Expansion Joint is a related configuration.



This is an assembly of two single joints separated by a short
run of pipe.
The pipe separating the two joints is usually restrained from
motion by an anchor.
The use of a double joint is the same as a single joint but it can
share the total axial deflection between the two joints.
© Intergraph 2014
Single Tied Expansion Joint




Looking at an expansion joint, one might assume it is designed to
absorb piping growth along its centerline.
Certainly there is a significant difference between the axial stiffness
of the pipe and that of the joint.
Axial deflection of the joint works well when the attached piping can
be safely guided into the joint and thrust blocks incorporated into the
design.
However, many cases exist where this sort of protection from
pressure thrust failures cannot be used - one example is tight
piping around equipment.
Tie Rods
Limit Rods
© Intergraph 2014
Single Tied Expansion Joint


Axial pressure thrust may be contained by tie rods without
adding anchors & guides to the adjacent piping.
Tie rods drastically alter the nature of the joint.



Untied joints provide flexibility in the axial direction.
Tied joints are essentially rigid in the axial direction, but lateral
flexibility is available to the designer.
A simple, tied expansion joint, is installed perpendicular to
the plane of required flexibility.
© Intergraph 2014
Hinged Expansion Joint




Tie bars on either side of a single expansion joint may
also be hinged. This allows angulation about the hinge
axis but prevents axial or transverse deflection.
Hinged joints are quite compact and can easily contain
Pressure Thrust loads.
In most cases, two or even three hinged joints work
together to provide needed flexibility.
Hinged joints often require guides to force the piping into
the flexible direction.
© Intergraph 2014
Gimbal Expansion Joint




Gimbal joints combine two, perpendicular, hinges across
an expansion joint assembly joining a ring at the center
of the joint.
This articulated joint allows bending about both axes
perpendicular to the axis of the joint.
Gimbal joints are usually used with other gimbal joints or
hinged joints along with pipe guides.
Guides are used to force motion in a perpendicular line
to the hinge axes of the joints.
© Intergraph 2014
Universal Expansion Joint




A universal expansion joint is a double joint without an anchor on
the center spool piece.
The lack of restraint on the center piece turns it into a linkage
between the two joints. This linkage assembly converts the joint’s
bending flexibility into large transverse displacements.
A longer center piece produces greater transverse offsets with the
same bending on each joint.
However, the lack of restraints or other pressure containing
elements limits the application of this joint to low pressure lines.
© Intergraph 2014
Tied Universal Expansion Joint




These assemblies have a universal expansion joint configuration
with a set of tie rods running over both joints to contain the pressure
thrust
The tie rods are attached to the center spool piece to stabilize the
entire unit.
The tie rods eliminate any axial flexibility but permit a greater range
of transverse movement through the bending of the two joints.
The greater the length of the center pipe, the greater the transverse
deflection with the same amount of joint bending
© Intergraph 2014
Other Configurations…
(Swing Expansion Joint)




Some piping configurations require transverse flexibility in one
direction but not the other.
A swing joint is similar to a tied universal joint in that it has a pair
of bellows and a center spool piece. The swing joint has hinged bars
restraining the pressure thrust in place of tie rods
Parallel hinges at either end of the assembly allow bending about
one axis rather than two.
These joints therefore direct the transverse deflection of the joint
along a defined vector perpendicular to the axis of the expansion
joint assembly.
© Intergraph 2014
Other Configurations…
(Pressure Balanced Expansion Joint)

Utilization of axial flexibility in an expansion joint usually requires the
joint to be untied and heavily guided.


Tie rods, while containing the pressure thrust forces, eliminate axial
flexibility of an expansion joint.
Another way of keeping axial flexibility without adding extra guides
and thrust-resisting anchors is by using pressure-balanced expansion
joints.
© Intergraph 2014
Other Configurations…
(Pressure Balanced Expansion Joint)

A way of understanding this axial flexibility is to examine the
tee piece of the expansion joint.


This tee is relatively free to move axially as the pressure thrust
load is carried across the entire joint through the tie rods.
The tee is resisted only by the axial stiffness of the attached
expansion joints.
Lateral deflection is
affected by XJ stiffness
but not pressure thrust
© Intergraph 2014
Additional Hardware…
(Guides)

Guides are required to force the piping in a specific direction so that
the joint deflects in a controlled and safe manner.
© Intergraph 2014
Additional Hardware …
(Anchors)



Pressurized joints without tie rods or hinges require anchors to
accommodate the pressure thrust load.
In most instances without an expansion joint, the pressure thrust
load is contained by the pipe wall.
The flexibility of the joint cannot limit the axial deflection of the pipe
due to pressure and so this thrust must be restrained elsewhere
upstream and downstream from the untied joint.
© Intergraph 2014
Additional Hardware
(Pressure Thrust Considerations)



Any supports on the line must be examined to confirm their ability to
accommodate the Pressure Thrust load.
CAESAR II (as most any other pipe stress analysis program) does not
automatically incorporate structural analysis of the pressure loading.
It is up to the analyst to confirm that the load is of correct magnitude
and applied at an acceptable location on the piping system.
© Intergraph 2014
B31.3 Statements on Pressure
Thrust at Expansion Joints

321.2.1 Anchors and Guides
(c) Piping layout, anchors, restraints, guides,
and supports for all types of expansion joints
shall be designed in accordance with para.
X301.2 of Appendix X.

301.2 Piping Designer Responsibilities,
Appendix X
The piping designer shall specify the design
conditions and requirements necessary for
the detailed design and manufacture of the
expansion joint in accordance with para.
X301.1 and the piping layout, anchors,
restraints, guides, and supports required by
para. X301.2.
© Intergraph 2014
Ultimately EJ is vendor Designed &
You are just evaluating their product
performance in your system.
Additional Hardware
(Applying Pressure Thrust)



CAESAR II will apply the Pressure Thrust load on either end of an
untied joint (but this is only a good approximation).
A properly located thrust load may be determined by imagining a
position inside the joint; the pipe wall seen upstream and
downstream from the joint is the proper point to apply the pressure
thrust load.
This point may be beyond a support that was assumed to contain
the pressure thrust.
Actual Pressure Loads (P*A)
T4
T4
CAESAR II applies the Pressure Thrust loads here
actually applied to the first adjacent wall in system
© Intergraph 2014
𝑻𝑻 = 0
𝑻𝑻𝟏𝟏 = 𝑃𝑃 ∗ 𝜋𝜋�4 𝐷𝐷𝑒𝑒𝑒𝑒𝑒𝑒 2 − 𝐷𝐷𝑖𝑖 2
𝑻𝑻𝟐𝟐 = 𝑃𝑃 ∗ 𝜋𝜋�4 (𝐷𝐷𝑖𝑖 2 )
𝑻𝑻𝟒𝟒 = 𝑃𝑃 ∗ 𝜋𝜋�4 (𝐷𝐷𝑒𝑒𝑒𝑒𝑒𝑒 2 )
Expansion Joints Flexibility
Summary




Expansion joint assemblies add flexibility to a piping system.
However, these assemblies cannot supply flexibility in all directions.
The requirement to restrain the pressure thrust load must still be
satisfied and this requirement may/will eliminate one or more flexible
degrees or freedom from the configuration.
Various assemblies can be categorized based on available
flexibilities…
© Intergraph 2014
Expansion Joints Flexibility
Summary
Type
Freedom
Notes
requires guides and thrust supports; lateral & bending allowed at
low pressures
Untied
axial
Tied
lateral
Hinge
bending
one axis; used in combinations for lateral flexibility, guides
recommended
Gimbal
bending
both axes; see hinged
Untied
Universal
axial &
lateral
stable only for low pressure applications,
total offset determined by length of center piece
Tied
Universal
lateral
piece total allowable offset is a function of center piece length
Pressure
Balanced
"axial &
lateral"
compact and stable
used with a bend or tee on center piece so it may be considered
lateral, provides axial flexibility without additional pipe supports
© Intergraph 2014
Expansion Joint Assembly
Proper Selection

Expansion joint assemblies, selection is based
upon…




Ability To Provide Flexibility In Specific Directions
Space Requirements
Support Requirements
One good source of information is found in A
Practical Guide to Expansion Joints by the
Expansion Joint Manufacturers Association, Inc.
(25 North Broadway, Tarrytown , NY 10591).

This Guide Describes:
 Expansion Joint Parts
 How To Design A System Containing Expansion Joints,
 Recommendations On Proper Installation And Handling.
© Intergraph 2014
Expansion Joint Assembly
Proper Selection




Actual expansion joint selection
is not the function of CAESAR II.
CAESAR II can be used to
facilitate expansion joint
selection.
This task is the
responsibility of the
individual engineer & the
joint manufacturer.
There is much more to expansion joint
selection than what is covered in this
presentation
© Intergraph 2014
Expansion Joint Assembly
Proper Selection


Pipe is quite rugged. High loads and stresses in the piping usually
do not justify the installation of an expansion joint.
The equipment to which the piping is attached is another story.



In many cases the piping attached to rotating equipment may be loaded
to only 5% of its allowable expansion stress limit so that the pump,
compressor, or turbine loads do not exceed their allowable limits.
This low load limit must be handled in both the cold and hot piping
positions.
Adding or adjusting supports should reduce the cold loads on the
equipment, but the change between the hot and cold loads is a
function of the thermal loads and the piping flexibility – incorporating
an expansion joint is one way to increase flexibility and reduce load.
© Intergraph 2014
Expansion Joint Assembly
Proper Selection…

How much room is available for the joint
and what sort of load must be decreased
determines what expansion joint
configuration should be used.

Identifying any excessive force or
moment is the first step in specifying an
expansion joint assembly.
© Intergraph 2014
Example
Expansion Joint Assembly
Proper Selection…

Example
Nozzle Check For Top Discharge Nozzle At Node 10:
Global MY
© Intergraph 2014
Global MX
Expansion Joint Assembly
Proper Selection…
Excessive Bending & Twisting
Moments on Pump Nozzle
© Intergraph 2014
Example
Expansion Joint Assembly
Proper Selection…
Excessive Bending & Twisting
Moments on Pump Nozzle,
Caused by Expansion (Z Dir.)
© Intergraph 2014
Example
Expansion Joint Assembly
Proper Selection…

A.
What expansion joint assembly can provide
flexibility in Z?
Untied joint on leg A



B.
requires pressure and offset control
additional guides required (leg A) to prevent
lateral motion of the expansion joint
Increase in the nozzle bending moment MZ
would also result
Tied joint on either leg B or leg C

C.
Example
A tied joint in leg C would provide flexibility for
both horizontal legs
One or more hinge joints may also serve the
purpose (e.g. a swing joint on leg B with
vertical pins)
© Intergraph 2014
B
A
C

Calculating Demand


The CAESAR II model can be adjusted to determine how many
convolutions are required
Use “relative” restraints (i.e., proper restraint directions with
Node/CNode pairs) to hold the inflexible directions and allow free
motion in the flexible directions
Restraints added in
Y, RX & RZ
between 20 & 21*
(*20-21 are same point in
space {ball & socket})
© Intergraph 2014
Calculating Demand

The expansion stress case indicates the free deflection required of the
expansion joint, the differential between joints 20 to 21 indicates…:



𝛿𝛿𝑥𝑥 = 0.8808 − 0 = 0.8808
𝛿𝛿𝑧𝑧 = −0.9997 − 0.0460 = −1.0457
𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺𝐺 = 𝛿𝛿𝛿𝛿 2 + 𝛿𝛿𝛿𝛿 2 =
0.88082 + (−1.0457)2 = 1.367 𝑖𝑖𝑖𝑖
© Intergraph 2014
Joint Selection


Lateral Growth Demand is 1.367 inches
Selecting the number of convolutions for the joint (of proper
diameter and pressure class) that can accept this Non-Concurrent
Lateral movement from the manufacturer’s catalog…
© Intergraph 2014
Joint Selection



Lateral Growth Demand is 1.367 inches
20 Convolutions Joint is sufficient (although quite
long)
A better choice may be a tied universal joint
© Intergraph 2014
Range of Expansion Joint Models
Capable CAESAR II




Zero Length Expansion Joint
Simple Expansion Joint
Assembly using the Expansion Joint Modeler
Complex Assembly built by hand (very time consuming)
An example of a complex model
© Intergraph 2014
Modeling Details

Many Required Expansion Joint Parameters Have Already Been
Established and Specified…



Pipe Size, Pressure Rating, End Type, and Number of Convolutions
Have Been Already Been Calculated.
With This Data and The Manufacturer's Catalog, Information
Required to Properly Model The Assembly in Your CAESAR II
Analysis, Can Be Identified.
Collect & Enter The Following Joint Parameters from the Vendor





Flexible Length
Effective Inside Diameter (needed for Pressure Thrust Calculation)
Axial And Lateral Stiffness
Bending Stiffness
Torsional Stiffness
© Intergraph 2014
Modeling Details

Select the
Expansion Joint
Box and enter the
following:





1.
3.
Flexible Length
Effective Inside
Diameter
Axial and Lateral
Stiffness
Bending Stiffness
(Optional; Blank Here)
Torsional Stiffness
4.
5.
2.
© Intergraph 2014
Joint Flexible Length
(Actual vs. Overall Length)



Catalogs list the Overall Length (OAL) length
of the joint. This length includes the nonflexible end pieces to which the rest of the
piping system is connected; for example,
weld ends or flanges. (We do not want this length)
A proper stiffness model of an expansion
joint requires that the true flexible length
of the bellows be specified, not the
longer, "shipped" length.
This is because this length establishes the
relationship between lateral and bending
stiffness for a proper model of the finite
length expansion joint.
© Intergraph 2014
Joint Flexible Length
(Actual vs. Overall Length)




Example – 10 inch 50psi SENIOR FLEXONICS PATHWAY joint:
Each additional 4 convolutions adds 3.5 inches to the overall length
A 12 convolutions joint would have an actual flexible length of 3*3.5 or
10.5 inches
This length is valid for all end types
+4
+3.5”
© Intergraph 2014
Effective Joint (Inside) Diameter





This is not the minimum or maximum inside diameter of the bellows,
nor is this value equal to the I.D. of the attached pipe.
Effective Joint (Inside) Diameter of the bellows is the mean
diameter of the bellows.
Effective Bellows Diameter Sets The Effective Inside Area Which
Is Very Important In Calculating The Total Pressure Thrust.
Pressure thrust is significant because it may cause gross
deformation and failure of improperly restrained joints.
This diameter (along with the length) can be used to establish the
relationship between joint axial stiffness and the lateral and bending
stiffnesses.
© Intergraph 2014
Effective Joint (Inside) Diameter



In a simple expansion joint model, this value must be specified if the
joint is untied. CAESAR II will calculate the pressure thrust load and
apply these forces on either end of the expansion joint element.
A simple model of a tied joint (where tie rods are not explicitly
modeled) would leave the Effective Joint (Inside) Diameter as
zero, so this pressure thrust is not included. In a tied joint, the
pressure thrust force loads up the tie rods and cannot extend the
flexible bellows.
CAESAR II expansion joint modeler will always include the
effective diameter since the program will also generate a model
for the tie rods which resist this pressure thrust.
© Intergraph 2014
Effective Joint (Inside) Diameter




Example – 10 inch 50psi SENIOR FLEXONICS PATHWAY joint:
Sample joint mentioned earlier shows the Effective Area* for that
(*Effective Area ≠ Effective Diameter)
expansion joint as 109 sq. in.
CAESAR II requires this in terms of Diameter:
𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫𝑫 = 𝟐𝟐 ∗ 𝑨𝑨𝑨𝑨𝑨𝑨𝑨𝑨⁄𝝅𝝅
Therefore Effective Diameter = 11.781 inches
© Intergraph 2014
Joint… Axial and Lateral Stiffness


While axial stiffness is set by the bellows geometry and manufacture,
lateral stiffness for the joint can be derived from the length, effective
I.D. and axial stiffness through the following equation:
𝑲𝑲𝒍𝒍𝒍𝒍𝒍𝒍 =






3⁄
2
∗ 𝐷𝐷𝑒𝑒𝑒𝑒𝑒𝑒 2 ∗ 𝐾𝐾𝑎𝑎𝑎𝑎 ⁄𝑙𝑙 2
Klat - lateral stiffness
Deff - effective ID
Kax - axial stiffness
L - flexible length
For the example, axial stiffness and lateral stiffness may be read
directly from the catalog: Kax=689 lb./in and Klat=1301 lb./in.
Lateral stiffness can also be derived from the equation above to be:
𝑲𝑲𝒍𝒍𝒍𝒍𝒍𝒍 = 3⁄2 ∗ 11.781 2 ∗ 689⁄ 10.5 2 = 1301 lb/in
© Intergraph 2014
Joint… Bending Stiffness

For a finite length (non-zero) expansion joint, the bending stiffness is
defined by the axial stiffness in the following equation:
𝑲𝑲𝒃𝒃 = 𝜋𝜋�360 ∗ 𝐾𝐾𝑎𝑎𝑎𝑎 ∗ 𝐷𝐷𝑒𝑒𝑒𝑒𝑒𝑒 2
Kb - bending stiffness of the joint (in-lb./degree)

Removing the reference to the effective inside diameter (which is
not required input for CAESAR II), the lateral and bending terms are
related to each other through the formula:

𝑲𝑲𝒃𝒃 = 𝜋𝜋�540 ∗ 𝐾𝐾𝑙𝑙𝑙𝑙𝑙𝑙 ∗ 𝑙𝑙 2
CAESAR II will determine the Kbending based on the Klateral Stiffness; It is therefore not
necessary or recommended to enter both values.
© Intergraph 2014
Joint… Bending Stiffness



𝑲𝑲𝒃𝒃 = 𝜋𝜋�540 ∗ 𝐾𝐾𝑙𝑙𝑙𝑙𝑙𝑙 ∗ 𝑙𝑙 2
With this association between lateral and bending stiffness,
CAESAR II input, for a finite length joint, will permit the entry of
either bending or lateral stiffness; a warning will be displayed if both
are specified.
The program's expansion joint modeler uses the lateral stiffness and
leaves the bending stiffness blank.
Continuing the example, the bending stiffness is calculated to be:
𝐾𝐾𝑏𝑏 = 𝜋𝜋�540 ∗ 1301 ∗ 10.5 2 = 834 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑
© Intergraph 2014
Joint… Bending Stiffness


𝐾𝐾𝑏𝑏 = 𝜋𝜋�540 ∗ 1301 ∗ 10.5 2 = 834 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑
But the catalog lists a different value!:
Both the expansion joint catalog (and the expansion joint database
in CAESAR II) indicate 209 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑, Why?
Many catalogues show “bending flexibility” rather than
“bending stiffness”. (They are not equal!)
© Intergraph 2014
Bending… Stiffness vs. Flexibility



The angular stiffness listed in the catalog is calculated independent
of any lateral deflection. That is, it would take 209 in-lb. to impose a
one degree net rotation on the joint without controlling any lateral
offset. The beam stiffness formulation used by CAESAR II uses a
bending stiffness based on no corresponding lateral offset.
It takes 834 in-lb. to impose a one degree net rotation on the same
joint if lateral offset is held to 0.
The bending moment required to produce the same net rotation
without translation is four times greater than a bending moment
where translation is not controlled.
© Intergraph 2014
Bending… Stiffness vs. Flexibility
Example

CAESAR II bending stiffness is four times the stiffness listed in
many expansion joint catalogs.
© Intergraph 2014
Bending… Stiffness vs. Flexibility
Example
Flexibility
Stiffness

Free Deflection
Controlled Deflection
Recall that bending flexibility is 209 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑 & bending stiffness is 834 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑
4*209 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑 = 834 𝑖𝑖𝑖𝑖 � 𝑙𝑙𝑙𝑙𝑙𝑙/𝑑𝑑𝑑𝑑𝑑𝑑
© Intergraph 2014
Zero-length Expansion Joint


For "zero-length" expansion joints, CAESAR II requires stiffness
specified in both bending and lateral direction.
Therefore the catalog value should be used
10-20 remains 10.5”
“Bending flexibility”
entered
Zero-length XJ defined
between 15-16
© Intergraph 2014
Zero-length Expansion Joint Results
Moment
Moment
Same results as the
finite length joint
defined earlier:
© Intergraph 2014
Free Deflection
Controlled Deflection
Joint… Torsional Stiffness


Expansion joints are extremely sensitive to
axial rotation (torsion); therefore accurate
calculation of the net axial rotation is
important.
The stiffness is listed in the manufacturer’s
catalog. The circled value on the right is
the magnitude for the torsional stiffness of
the sample 10 inch 50 psi 12 convolution
joint.
Torsional Spring Rate units are mislabeled in this table.
Units should be 106*in-lbf/degree. The CAESAR II expansion
joint modeler shows the correct values.
© Intergraph 2014
X
Expansion Joint Modeling



Example
Add an 8 inch, 50 psi, 20 convolutions joint into the model using
the CAESAR II Expansion Joint Modeler
As a convenience, the expansion joint will be placed on the straight
run after the weld neck flange. (The current element shown below.)
Select the modeler from the tool bar or the menu:
© Intergraph 2014
Expansion Joint Modeling

Select your joint from the Modeler Menu:
© Intergraph 2014
Example
Expansion Joint Modeling
Example

CAESAR II displays the information for the selected expansion joint
assembly:

The existing element 20-30 is
now:
 20-21: slip on flange
 21-22: the expansion joint
 22-23: slip on flange
 23-30: remaining pipe
 20-24: the tie rod model

The modeler displays the XJ
stiffnesses and the allowed,
non-concurrent movement
Press Build to
update the model
with this information.
© Intergraph 2014
Automated Expansion Joint Model
© Intergraph 2014
Automated Expansion Joint Model
Tie Rod Element is set to ambient temperature;
need to recheck downstream temperatures.
© Intergraph 2014
Reanalyze with the Expansion Joint
Without XJ
© Intergraph 2014
Reanalyze with the Expansion Joint

Nozzle check still exceeds API 610 limits but by less than 2 times.
(API 610 Annex F checks may still qualify this pump.)

Tie rods are the source of this large moment about Z
A tied universal joint may fare better.
Global MZ
(Consult the manufacturer.)

© Intergraph 2014
Greater than 1
but less than 2
Joint Evaluation

Catalogs list non-concurrent axial movement, non-concurrent lateral
movement, and non-concurrent bending *
(*Non-concurrent means only one is allowed)


However, these joints suffer movement in more than one direction
How are these multiple motions evaluated?



Unity Check
EJMA – Calculated Equivalent Axial Growth
Torsional rotation is handled independently of other motion
© Intergraph 2014
Joint Evaluation

Unity Check

Here’s what the Pathway catalog indicates:

Ratio required movement to rated movement in each direction and sum
the ratios, if less than 1.0, the joint passes this criteria
CAESAR II provides this check in an outboard analysis module

© Intergraph 2014
Joint Evaluation

Equivalent Axial Growth



The Expansion Joint Manufacturers Association (EJMA)
provides a method to convert bending and lateral motion into
equivalent axial growth
The sum of these values and the actual axial growth can be
compared to the permitted non-concurrent axial growth listed in
the catalog
CAESAR II also provides this check in an outboard analysis
module
© Intergraph 2014
Joint Evaluation

CAESAR II Expansion Joint Modeler indicates expansion joint rated
movements…
Catalog:
CAESAR II Modeler:
© Intergraph 2014
Joint Evaluation



Expansion joints are rated for a set number of cycles – 2000.
The catalog or the manufacturer should offer a means of reducing
the non-concurrent movement based on the number of cycles in
excess of 2000.
Pathway adjustment (shown as an example):
(A joint that is rated at 1.0 inch non-concurrent axial movement at 2000
cycles would be rated at 0.905 inches for a 3000 cycle life.)
Do you know how many cycles your system will
experience? Need to De-Rate for higher life
© Intergraph 2014
Anchors & Guides

Anchors are located to contain pressure thrust loads


Not required for assemblies with proper pressure thrust control
(e.g., tie rods or hinge plates)
Guides are used to force proper growth into the
expansion joint assembly
© Intergraph 2014
B31.3 Concerns

Hardware strength


All hardware associated with pressure thrust control must be
designed for these loads
Leak Testing



Temporary hardware is not permitted in the leak test
Expansion joints are often shop tested
Shop tested joints need not be included in the piping system’s
leak test
© Intergraph 2014
Stiffness Model vs. Geometric Constraints


CAESAR II provides a stiffness method solution and is not
geometrically constrained
Example:


Hinge with bending stiffness on a cantilever, force applied at free end
For given end force, what is end rotation and displacement?
© Intergraph 2014
Stiffness Model vs. Geometric Constraints

Applied force = 10 lbf (a small load)




Applied Force = 100 lbf; 10 times small load increase



𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 ∗ 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝐴𝐴𝐴𝐴𝐴𝐴⁄𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆
𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = −10 ∗ 120⁄1000 = −1.2 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 = 𝐴𝐴𝐴𝐴𝐴𝐴 ∗ 𝑇𝑇𝑇𝑇𝑇𝑇 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = 120 ∗ 𝑇𝑇𝑇𝑇𝑇𝑇 −1.2 = −2.514 𝑖𝑖𝑖𝑖
Rotation increases by a factor of ten = -12 degrees
Deflection increases by a factor of ten = -25.14 inches
Applied Force = 1000 lbf; 100 times the small load increase


Rotation increases by a factor of 100 = -120 degrees
Deflection increases by a factor of 100 = -251.4 inches
Stiffness = Load / Deflection =3.977 lbs./in for all scenarios
© Intergraph 2014
Stiffness Model vs. Geometric Constraints
But this makes no sense!
Geometrically.



© Intergraph 2014



Stiffness Model vs. Geometric Constraints

Axial strain in tie rods or spool is not considered and may be
significant with larger rotations
CAESAR II will show the rotating end as moving
straight up rather than arcing around the pivot point
© Intergraph 2014
Expansion Joints in Piping Systems
(What We Covered & Acknowledgements)







Introduction
Review of Expansion Joint Assemblies
Selecting and Locating the Appropriate Joint Assembly
Calculating XJ Demand
Modeling Details
Evaluating the Joint
Closing Points
Many of the illustrations in this presentation have been reproduced from
the Senior Flexonics Pathway catalog


Used with permission
No rights are granted for additional use or distribution
© Intergraph 2014
Expansion Joints in Piping Systems
(Treasure Chest)








Flixborough Disaster 1974
Senior Flexonics Pathway catalog
ICAS Discussion Forums
ICAS Webinars
GT STRUDL® Structural Modeling, Analysis & Design
INSIDER Blog / Newsletter CADWorx & Analysis Solutions
CAESAR II Group (LinkedIn)
Intergraph CADWorx & Analysis Group (LinkedIn)
How Many CAESAR II Quick Tips were provided in this presentation?
© Intergraph 2014
Expansion Joints in Piping Systems
Questions?
Comments?
Ideas?
Thank You
© Intergraph 2014