What is a Simple Expansion Joint

Simple expansion joint is one of different types of bellows used in piping system mentioned in my previous post .

BELLOW TYPES:

• Simple Expansion Joint
• Universal Expansion Joint
• Pressure Balanced Expansion Joint
• Hinged Expansion Joint
• Gimbal Expansion Joint

Below are the illustrations of the typical situations for employing Simple Expansion Joint type of Bellows depending upon the application and configuration of the piping profile.

SIMPLE EXPANSION JOINT:

The main use of single expansion joint in a piping system is to absorb axial & small amount of lateral & angular movements in which it is installed.

 

 

A. Expansion Joint for absorbing axial displacement:

1. Single Element Bellow installed in a straight line

A typical arrangement of the above application is shown in the accompanying sketch(Figure-2) below. The Bellow is locked between the end anchors (Main Anchors) and isnormally located close to one of the above Main Anchors. The other end of the Bellow isaccompanied by First Alignment Guide G1 (as close as possible to the below) followed bySecond Alignment Guide G2 at a distance of 14 D (as per EJMA recommendation). TheSecond Alignment Guide G2 is, followed by the Intermediate Guides (located as per thenormal support span) if required as per the length of the line.

 

2 Single Element Bellow installed in a straight line with an offset

A typical arrangement of the above application is shown in the accompanying sketch(Figure-3) below. The application of this type is normally not recommended and will performsatisfactory only within certain limits. The axial pressure thrust of the Bellow is transmitted tothe Main Anchor through the offset, resulting into bending moment in the piping.

The remaining arrangement of the Main Anchors, First and Second Alignment Guides andrest of the Intermediate Guides remains same as that of the Bellow installed in a straight line.

 

3 Double Element Bellow employing an intermediate anchor in the middle when installed in a straight line

A typical arrangement of the above application is shown in the accompanying sketch(Figure-4) below. The arrangement is generally employed in the situations where the linearexpansion of the line is of a very large magnitude. The Bellow assembly consists of 2elements separated by an Intermediate Anchor. Thereby absorbing the linear expansion ofthe 2 sections of the pipeline individually. It may be noted that the above Intermediate Anchorneed not be designed for the bellow axial force, which cancels out between the 2 BellowElements. The remaining arrangement of the Main Anchors, First and Second AlignmentGuides and rest of the Intermediate Guides remains same as that of the Bellow installed in astraight line.

 

4 Double Element Bellow employing a main anchor in the middle, installed in a straight line at the interface of changed line size (i.e. reducer)

A typical arrangement of the above application is shown in the accompanying sketch(Figure-5) below. The arrangement is similar to that of Double Element Bellow on a straightpipeline except that the middle anchor between the 2 Bellow Elements is required to bedesigned as Main Anchor for the differential axial thrust of the 2 Bellows employed on eachside of the Reducer.

 

5 Three Element Bellow employing a main anchor in the middle, installed at thejunction of the branch connection

A typical arrangement of the above application is shown in the accompanying sketch(Figure-6) below. The middle anchor between the 3 Bellow Elements in this case is requiredto be designed as Main Anchor for the axial thrust imposed by the Bellow of the branch pipe.

 

B. Expansion Joint for absorbing lateral movement, angular rotation and combined movement:

1. Single Element Bellow employing a directional anchor, installed in the longer leg of L shaped piping profile

A typical arrangement of the above application is shown in the accompanying sketch(Figure-7) below. The Bellow is located at 1 end of the longer leg and thereby absorbing thelinear expansion of the longer leg as axial displacement. The Main Anchor near the Bellow isa Directional Main Anchor (DMA), which prevents the pipe end from moving axially, at thesame time allowing the expansion of the shorter leg, which is absorbed by the Bellow as alateral deflection. The Anchor on the shorter leg is required to be designed, only asIntermediate Anchor. The remaining arrangement of the First and Second Alignment Guidesand rest of the Intermediate Guides remains similar to that of the Bellow installed in a straightline to prevent the straight pipe of the longer leg from rotating/ buckling.

 

2. Single Element Bellow employing a directional anchor, installed in the shorter leg of L shaped piping profile

A typical arrangement of the above application is shown in the accompanying sketch(Figure-8) below. The Bellow is located in the shorter leg and thereby absorbing the linearexpansion of the longer leg as lateral displacement. The Main Anchor near the Bellow is aDirectional Main Anchor (DMA), which prevents the pipe end from moving axially, at the sametime allowing the expansion of the long leg, which is absorbed by the Bellow as a lateraldeflection. The Anchor on the longer leg is required to be designed, only as IntermediateAnchor. Only 1 Guide is required on the longer leg for alignment purpose.

 

3. Single Element Bellow employing a tie rod in place of a directional anchor, installedon the shorter leg of L shaped profile

A typical arrangement of the above application is shown in the accompanying sketch(Figure-9) below. This is a modified arrangement wherein, by employing a tied Bellow (in theshorter leg) the need of the Directional Main Anchor (DMA) is eliminated. Owing to tie rods thebellow can only absorb lateral deflection (other than its own axial growth) and hence the axialgrowth of shorter leg must be accommodated by the flexibility in the longer leg.