Intergraph 2014

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! Low Cycle Life Fatigue expansion joints are rated for 2000 cycles Failure due to unanticipated through-the-wall crack

Requires additional hardware 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 Single Expansion Joint Untied Universal Expansion Joint

Assemblies with pressure control Single, Tied Expansion Joint Hinged Expansion Joint Gimbaled Expansion Joint Tied Universal Expansion Joint

Other configurations Swing Expansion Joint Pressure-balanced Expansion Joint

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=DuIolRdPCRs5IM&tbnid=KPGQPH9kDhLIuM:&ved=0CAUQjRw&url=http://en.wikipedia.org/wiki/Metal_expansion_joint&ei=G4A8U7apJsLkiAe44YHYCQ&bvm=bv.63934634,d.aGc&psig=AFQjCNGLt1dhp3StUxaRrrT0wcbvSoVxCw&ust=1396560254796100http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=DuIolRdPCRs5IM&tbnid=KPGQPH9kDhLIuM:&ved=0CAUQjRw&url=http://en.wikipedia.org/wiki/Metal_expansion_joint&ei=G4A8U7apJsLkiAe44YHYCQ&bvm=bv.63934634,d.aGc&psig=AFQjCNGLt1dhp3StUxaRrrT0wcbvSoVxCw&ust=1396560254796100

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 joints 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