Externally Pressurized Expansion Joints
An externally pressurised expansion joint is an axial expansion element in which fluid passes between the outer shell and the bellows rather than inside it, so the bellows is pressurised from outside and is more stable against buckling under long axial movement.
It is used on district heating, long straight steam and high-temperature water lines where large thermal expansion must be absorbed. The product range includes DN25–DN300 weld neck (-60 and -90 series) and flanged (-30 series) models.
Main Applications
- District heating networks
- Long straight steam lines
- High-temperature water lines
- Buried pre-insulated lines
- Process lines with large expansion
- Pipe routes in ducts
Technical Data
| Type | Externally pressurised axial expansion joint |
|---|---|
| Sizes | DN25 – DN300 (product range) |
| Series | Weld neck -60 and -90; flanged -30 (product name) |
| Bellows | Stainless steel (AISI 321, parent group sheet) |
| Outer shell | Carbon steel (depending on model) |
| Pressure class | Depending on model (PN16 standard, parent group sheet) |
| Axial movement | By series (depending on model) |
| Operating temperature | By material (parent group sheet) |
Material Options
| Part | Internally pressurised axial | Externally pressurised axial |
|---|---|---|
| Pressure direction | Inside the bellows | Outside the bellows |
| Stability on long movement | Limited | High |
| Outer protection | Depending on model | Protected by outer shell |
| Typical use | Short-movement lines | Long lines, district heating |
Which material? The externally pressurised type reduces bellows buckling risk on lines needing long axial movement. Movement and pressure values are confirmed with manufacturer data for each series.
Advantages
Long Axial Movement
- Absorbs large expansion
Buckling Resistance
- External pressure principle
Protected Bellows
- Outer shell
Suited to District Heating
- Buried lines
Construction and Design Features
- Stainless metal bellows
- External pressure shell
- Weld neck or flange
- Inner guide pipe
Send the size, pressure, temperature and axial movement needed; we will confirm a suitable externally pressurised expansion joint.
How to Choose?
- Size and connectionSet the DN and the end type, weld neck or flange.
- PressureAssess working pressure with temperature.
- MovementCalculate axial expansion and choose the series.
- MaterialDetermine shell material by fluid and temperature.
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Why ORFA?
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Our sales team will prepare the best solution for your needs.