Externally Pressurized Expansion Joints
Externally pressurized expansion joints is an excellent answer for large axial displacement needs. When large displacements are present in a system, more convolutions are needed to handle these large axial movements. Then, designing the bellows becomes a challenge for the expansion joint engineer due to “column squirm” (instability due to internal pressure / buckling of bellows) concerns. Solution to this challenge is to pressurize the “bellows” externally.
These units are very robust and safe. They have an in-built (part of the design) inner sleeve and outer cover. Outer cover protects the bellows from external damages during shipping, installation and operation. It also makes this unit suitable for underground usage. Inner sleeve provides smooth flow and prevents pressure losses.
These units are not suitable for lateral movements.
They can be provided with pipe ends, or welded / rotating flange connections supplied in accordance with many industrial norms or special drillings.
Advantages of Externally Pressurized Expansion Joints
- Externally pressurized expansion joints are used if there would be large axial movements.
- This type of expansion joint pressurizes the bellows externally, eliminating column instability concerns for the bellows.
- This configuration provides an outside cover protecting bellows from external elements and inside pipe acts as a liner protecting bellows from flow medium and and streamlines the flow.
- Minimizing pressure losses
Applications of Externally Pressurized Expansion Joints
- City district heating
- Steam and condensate lines
- Superheated water
- HVAC applications
- Chemical and process industries
- Pulp and paper industry
- Geothermal applications
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Design Values
DN
25 – 1000
Bellows Material
304, 316, 321
Flanged Material
Carbon Steel, Stainless Steel
Design Pressure
40 barg
Design Temperature
400°C
Please consult with our technical department for different working conditions and design parameters.
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CONSULT & MORE INFO
Expansion joint is any device containing one or more flexible element. Expansion joints are used to absorb dimensional changes in piping systems or vessels where flexibility is needed. Expansion joints are most commonly used to absorb thermal expansion/contraction, vibration, mechanical movements and ground settlements.
Expansion joints consist of bellows, accessories, and end connections. Bellows are the flexible elements. Convolutions are parts making up a bellows. Layers/plies are sheets making up a bellows
There are many advantages of using an expansion joint:
- They can absorb large movements in a small space.
- They are very flexible, lower forces on the piping system or vessel walls (except pressure force) are applied.
- They are maintenance free.
- If correctly designed, they can last a long time.
- They can absorb movements in all directions (except torsion).
Expansion joint covers are used to provide limited protection to the bellows exterior surface. Using covers is a relatively inexpensive way for protecting bellows from mechanical damage that can happen during shipping, handling and installation and is strongly recommended for critical expansion joints. Standard practice is to ask for removable shrouds. Removable shrouds let customers inspect the bellows before installation.
Expansion joint absorb movements by bellows convolution walls bending. Each convolution is flexible and absorbs the movement it is designed for. Expansion Joints are used to absorb axial, lateral and angular movements. Torsion should not be applied on expansion joints. Advantages of a multi ply expansion joint are lower spring rates (better for pipe stresses) and higher cycle life.
