Pipe Expansion 101
(the condensed version)
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Accommodating thermal expansion and/or movement in
piping systems is handled by using one or more of the
following:
 The inherent natural flexibility of the piping system
 Engineered pipe loops
 Through the use of expansion joints.
Engineered pipe loops simply serve to increase the natural
flexibility of the system.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
“The best and only way to ensure against
expansion joint failure, is to NOT have an
expansion joint in the first place."
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Natural Flexibility:
Typically the least expensive way to accommodate thermal expansion in
piping systems is by using natural flexibility.
Natural flexibility requires offsets in the system piping.
Offsets can exist due to the routing of the lines, or can be created in the
form of Z-bends or U-loops.
Z-Bend
U-Bend
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Natural Flexibility cont.:
When designing with natural flexibility you need to know the locations of
structural members that will act as anchor and support points for the system.
An ASME Code Stress Analysis should be performed to determine the
location(s) in the system where the least amount of thermal displacement
occurs.
WHY?
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Natural Flexibility cont.:
Locating anchors at the points in the system where the least amount of
thermal displacement occurs naturally, will result in the lowest anchor
point loads.
Anchor
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
But what happens when:
You have long straight runs of pipe with no room to add expansion loops?
or
You have long straight runs of pipe with plenty of room for expansion
loops; but adding them would result in excessive pressure drop?
or
Where the existing offsets are too short or too few to provide sufficient
natural flexibility?
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Application of Expansion Joints in Piping Systems:
There are two different types of expansion joints, and it is essential that
the Designer understand the differences between the two.
The two have completely different applications, act upon the pipe
differently, and must be installed in a different way.
Unrestrained Type – Typically used to accommodate axial movement in
piping systems. Simple bellows joints and packed slip type expansion
joints fall into this category.
Restrained Type – Used to take up offset and angular displacements.
Tied bellows, hinge joints, gimbal joints and packed flexible ball joints
are examples.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
Bellows Type
Universal Bellows
Single Bellows
Externally Pressurized Bellows
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Bellows Expansion Joints
Simple bellows type expansion
joints can be used to absorb axial
compression or extension
As well as small amounts of
angular displacement
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Bellows Expansion Joints
Bellows expansion joints should never be subjected to torsional
movements.
Torsion destabilizes a bellows expansion joint reducing its ability to
contain pressure and absorb movement.
If torsion is present in a piping system, “Restrained” expansion joints are
recommended.
Torsional movement is the rotation
about the axis through the center of
a bellows (twisting).
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
Packed Slip Type
Single Slip Expansion Joint
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
Slip type expansion joints are designed to accommodate axial
expansion only.
They will also accommodate pure torsional movements.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
Axial expansion joints are not pressure restrained. When pressurized
they tend to open up lengthwise.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
Pressure Thrust Load:
The thrust load which tends to force the expansion joint open is referred
to as “Pressure Thrust” and is equal to the cross sectional area multiplied
by the system design pressure.
 With bellows joints the cross sectional area is the effective area of the
convolutions.
 With slip type expansion joints it is the cross sectional area of the pipe.
The Pressure Thrust load acts on the system anchors.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
Unrestrained expansion joints are not provided with attachments such as
tie rods or hinges to restrain pressure thrust. Therefore, they can be used
only in piping systems that incorporate correctly designed anchors and
pipe alignment guides.
These components prevent over extension and damage due to distortion
under operating conditions.
PRIMARY
GUIDE
ANCHOR
INTERMEDIATE
GUIDE
ANCHOR
EXPANSION JOINT
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Unrestrained Expansion Joints
When using unrestrained expansion joints it is critical that the line be
properly guided.
Failure to provide adequate guiding can result in premature failure of the
expansion joint.
EJ Type
First Guide
Second Guide
Balance
Bellows
4 Pipe Diameters
14 Pipe
Diameters
Industry
Standard
Slip Joint
1 Foot for each inch of
nominal pipe diameter
Industry
Standard
Industry
Standard
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Restrained Expansion Joints
Restrained expansion joints operate on a completely different principle
from the unrestrained type.
Restrained expansion joints typically require offsets in the system piping
and absorb movement by lateral bending and/or rotation.
Restrained expansion joints have the advantage of eliminating pressure
thrust forces and providing flexibility with minimal forces.
Guiding requirements with restrained expansion joints are far less
stringent.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Restrained Expansion Joints
Tied Bellows
Universal
Tied Bellows
Hinged Joint
Gimbal Joint
Double
Hinged Joint
Double
Gimbal Joint
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Restrained Expansion Joints
Single Ball Joint
Double Ball Joint
Rotation Only Ball Joint
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Restrained Expansion Joints
Restrained expansion joints provide piping systems with increased flexibility by
allowing relatively free lateral and bending movements.
Pressure thrust loads are contained
within the joint, resulting in lower
anchor point loads.
Because restrained joints are
designed to accommodate lateral
and bending movements, the
guiding requirements are far less
stringent.
Typical 3 Ball Joint Linkage
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Expansion Joint Allowable Displacements
EJ
Type
Movement Type
Axial
Lateral
Bending
Rotational
Pressure
Thrust
Single
Bellows
Yes
small
small
No
Yes
Packed Slip
Joint
Yes
No
No
Yes
Yes
Universal
Tied Bellows
No
Yes
Yes
No
No
Hinged
No
No
Yes
(1 Plane)
No
No
Gimbal
No
No
Yes
(2 Planes)
No
No
Packed Ball
Joint
No
No
Yes
(Any Plane)
Yes
No
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Bellows Joint Advantages:
 Bellows Joints do not require access; i.e. they can be direct buried.
(A telltale device is recommended if buried)
 No maintenance is required.
Bellows Joint Disadvantages:
 No in place maintenance or repair can be performed – it must be
replaced if damaged.
 When failure occurs the system must be shut down.
 Chance of personal and/or property damage when failure occurs.
 Installer can easily misuse joints when correcting for pipe
misalignment.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Packed Expansion Joint Advantages:
 Fabricated from materials similar to the pipe line.
 Rugged construction – The wall thickness of every part of the joint is at
least as heavy as the pipe line in which it is installed.
 Allows for safe packing injection under full line pressure.
 In the event that a leak occurs there is no need to shut the system down
for repair.
Packed Expansion Joint Disadvantages:
 Must be located to allow access.
 May require occasional addition of injectable packing.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Expansion Joint Failure Modes
Bellows Joints
Packed Joints
In-Plane Squirm
Column Squirm
Fatigue
Creep Fatigue
NONE
(If properly installed & maintained)
Burst, Collapse, Over Stretching
Corrosion
To avoid imposing any of these failure modes on a system, it is
imperative that the system be reviewed completely prior to
finalizing the design.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Expansion Joint Selection:
When selecting what type of expansion joint to use, the designer must
first review the system design parameters:
 Piping layout, including the locations of any equipment connections.
 Service (Steam, Condensate, etc.); including pressure & temperature.
 The availability of supporting structures for anchors, supports and
guides.
 The magnitude and direction of thermal displacements that will occur
during system operation.
 Seismic provisions (if require).
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Governing Bodies:
Just as there are different types of expansion joints; there are different
Standards and Codes which govern their design.
Bellows Joints: Expansion Joint Manufacturer’s Association (EJMA)
Slip Type Expansion Joints: ASTM F 1007 (2007)
Ball Type Expansion Joints: ASTM F 1298 (2006)
In addition; expansion joints should be designed to the requirements of
the appropriate ASME Piping Code (B31.1, B31.3, etc.)
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Anchors:
One of the most important parts of a piping system; and often the most
overlooked; are the anchors.
Typical Bolt Down Anchor
Typical Anchor with Pipe Spool
Properly designed, located and installed anchors are critical to the safe
uninterrupted operation of a piping system.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Typical Anchor Loads:
Deflection Loads : Bellows Spring Rate x Maximum Deflection or Slip Joint Packing Friction
(1,000 lbs./inch of Nominal Pipe Diameter).
 Pressure thrust load.
 Additional thrust load due to test pressure.
 Support/Guide friction loads.
 Branch connection loads.
 Dead weight loads on vertical and sloping pipe.
 Shock loads, due to quick opening valves or bursting safety discs.
 Centrifugal thrust loads.
 Wind loads.
 Seismic loads.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Anchor Designs:
Main Anchors: Designed to accommodate any and all load types,
including full pressure thrust loads.
Intermediate Anchors: Only need to be designed for light construction
since pressure thrust loads are absorbed by main anchors.
Directional Anchors:
Prevent movement in one or more
directions while allowing movement
in another. They may act as either
main or intermediate anchors; or
function as a guide.
16” Main Anchor with 6” Service Connection
300 PSIG Design
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Nypro Chemical Plant, Flixborough, England
On March 27, 1974 a vertical crack in Reactor No. 5 was discovered leaking cyclohexane and the plant was
shutdown for investigation.
A serious problem was found with the reactor and a decision was made to remove it and install a
temporary 20” bypass assembly to replace it.
The design of the bypass included a bellows joint that was intended to absorb the thermal expansion of
the line as well as accommodate an existing offset.
On June 1st the bellows ruptured; resulting in the escape of a large quantity of cyclohexane. Within
minutes 40 tons of cyclohexane leaked from the pipe forming a vapor cloud estimated to be as large as
650 foot in diameter.
The cyclohexane vapor cloud found a source of ignition, resulting in an explosion that completely
destroyed the plant.
The explosion was estimated as being equivalent to 15 tons of TNT.
28 fatalities were reported including 18 employees in a near by control room, 9 site workers and 1 delivery
driver that died of a heart attack. The failure occurred on a weekend and only a small number of
employees were at the plant.
1,800 buildings within a 1 mile radius were essentially destroyed and buildings as far as 8 miles away
experienced structural damage.
The blast was heard and felt as far as 25 miles away.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Nypro Chemical Plant, Flixborough, England - June 1, 1974
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Nypro Chemical Plant, Flixborough, England - June 1, 1974
What went wrong?
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Nypro Chemical Plant, Flixborough, England - June 1, 1974
The design of the bypass pass line failed to account for the pressure thrust load
associated with the bellows expansion joint.
This combined with the imposed offset, resulted in uneven loading on the bellows
causing the corrugations to “Squirm” which ultimately lead to the failure.
Squirm is caused by excessive unconstrained
pressure and is made worse as angular
movement of the bellows is introduced.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Some place in the United States:
In May of 2009 ATS received a request to supply 2 each 8” & 6” single slip expansion
joints with anchor bases.
The joints were required for an emergency outage, to replace expansion joints that
had failed.
The 8” joints were for steam service and the 6” for condesate.
The order was received on May 7th and the four joints shipped on May 11th.
Now Flash Forward to January 2011
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
In January of 2011 we received a call informing us that the expansion joints that we
had supplied in 2009 had failed.
The Customer again needed replacements on an emergency basis.
STOP Right There ! ! !
2 Sets of expansion joints
in less than 2 years?????
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
When 2 essentially identical expansion joint failures occur
in the same section of pipe?
It’s most likely not the fault of the expansion joints.
 Piping drawings and details were requested as well as any information that
could be provided relative to each of the failures.
 An ASME Code stress analysis was performed on the system based on the
information receive.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
System Piping Arrangement
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
Vault Piping Arrangement
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
Vault Piping Arrangement
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
The results of the stress
analysis found that the
piping inside the vault had
sufficient natural flexibility
and most likely was not the
cause of the failure.
The maximum calculated
stress ratio SE/SA = 0.16
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
So what went wrong?
• As of today the cause of the failure is still unknown.
• The Customer has contracted an independent engineering firm to perform
a forensic analysis of the failure.
• Based on the little information that we have, it was recommended that the
piping system outside of the vault be included in the review.
• An alternate arrangement was proposed for the piping within the vault that
would accommodate the thermal expansion of the system and at the same
time eliminate the potential for additional expansion joint failures.
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Same place in the United States:
Using a 3 ball joint linkage as shown provides the following advantages:
 Eliminates the need for anchors
in this vault.
 Eliminates the pressure thrust
forces acting on the system.
 Accounts for any settling or
alignment issues with piping
external to the vault.
8” HPS Line w/3 Ball Joints
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Conclusions:
 When choosing an expansion joint you must know the magnitudes,
directions and types of movements that it needs to accommodate.
 Selecting the proper type of expansion joint is key to having a trouble
free (Leak Free) system.
 If you have an expansion joint that is chronically developing leaks,
don’t automatically assume that it is the fault of the joint. Many times,
the failure is due to deficiencies in the piping system itself.
 If you need help with an expansion problem.
Ask an Expert
ACCOMMODATING EXPANSION IN PIPING SYSTEMS
Questions?
Edward W. Patnode, P.E.
President/CEO
ADVANCED THERMAL SYSTEMS, INC.
15 ENTERPRISE DRIVE, LANCASTER, NY 14086
Toll Free: 800-443-9194
Phone: 716-681-1800
Fax: 716-681-0228
Email: [email protected]
www.advancedthermal.net