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What Are Expansion Joints?

Expansion joints are designed to safely absorb the movement in pipework systems due to heat-induced expansion and contraction of pipework.

Expansion joint accessories

Expansion joint accessories
1. Bellows 2. Angle Flange 3. Weld End 4. Liner (Baffle) 5. Cover
6. Particulate Barrier/Insulation 7. Liner Seal 8. Purge
Draw
Customer sketches

Liners
Internal liners can be used to either protect the metallic bellows from erosion or reduce turbulence across the bellows. They must be used when purge connectors are included in the design. In order to provide enough clearance in the liner design, appropriate lateral and angular movements must be specified by the designer. When designing an expansion joint with combination ends, flow direction must be specified as well.

Covers
External covers should be used to protect the internal bellows from being damaged. They also serve a purpose as insulation of the bellows. Covers can either be designed as removable or permanent accessories.

Particulate barriers/purge connectors
In systems that have a media with significant particulate content (i.e. flash or catalyst), a barrier of ceramic fiber can be utilized to prevent corrosion and restricted bellows flexibility resulting from the accumulation of the particulate. Purge connectors may also be utilized to perform this same function. Internal liners must also be included in the design if the expansion joint includes purge connectors or particulate barriers.

Limit rods
Limit rods may be used in an expansion joint design to limit the axial compression or expansion. They allow the expansion joint to move over a range according to where the nut stops are placed along the rods. Limit rods are used to prevent bellows over-extension while restraining the full pressure thrust of the system.

TYPE
USES AND ADVANTAGES

INTERNAL SLEEVES

1. Minimize the pressure drop through expansion joint.

2. Prevent vibration of bellows induced by high velocity, turbulent flow.

3. Prevent erosion of bellows in abrasive services.

4. Internally insulate bellows in high temperature services.

ANCHOR BASE

Divide piping into two separate segments insuring proper movement of each bellows in double type expansion joint.

EXTERNAL COVER

1. Protect bellows against mechanical damage during installation and in service.

2. Protect personnel in hazardous services.

3. Serve as support for external insulation.

PURGE AERATION CONNECTIONS

Used in conjunction with internal sleeve to:

1. Prevent packing, "coking", of flue-solids between internal sleeve and bellows.

2. Introduce coolant between bellows and internal sleeve in very high temperature service.

TIE RODS

1. Prevent application of pressure thrust to piping, or equipment when expansion joint is used for lateral deflection and/or angular rotation only.

2. Used as limit rods on expansion joints for axial movement. Limit over-extension of joint and damage to piping or equipment if anchor fails.

3. Used as control rods to limit and control movement of universal type expansion joints.

OVERSIZED BELLOWS

1. Permit use of internal sleeve for joint moving laterally or angularly without reducing inside diameter.

2. Used in conjunction with internal sleeve to reduce bellows temperature in very high temperature service.




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