Axial Metal Bellows Expansion Joint / Welding Neck
A weld neck axial expansion joint is a metal bellows element welded directly into the pipeline by the weld necks at its ends, without flanges.
It is used on lines needing permanent, leak-tight joints, such as steam, high-temperature water, heating and district heating networks. DN25 to DN300 models are available in the -30 and -60 series, with or without an inner liner.
Main Applications
- Steam and condensate lines
- District heating networks
- High-temperature water lines
- Buried and duct lines
- Process heat lines
- Lines where tightness is critical
Technical Data
| Type | Axial metal bellows expansion joint, weld neck |
|---|---|
| Sizes | DN25 – DN300 (product range) |
| Series | -30 and -60; lined (L) and unlined (product name) |
| Bellows | Stainless steel 1.4541 (AISI 321) |
| Weld end | St 37.2 / P265GH-P355GH / AISI 304 (by temperature) |
| Pressure class | PN16 standard; PN2.5–PN63 manufactured |
| Axial movement | 30 mm (−20 / +10 mm) standard series |
| Operating temperature | −10 … +550 °C (by material) |
| Design basis | EN 14917 and EJMA |
| Certification | EN 10204 3.1; PED 2014/68/EU (depending on model) |
Material Options
| Part | −10 … 300 °C | 310 … 500 °C | 510 … 600 °C |
|---|---|---|---|
| Bellows | Stainless steel 1.4541 (AISI 321) | Stainless steel 1.4541 (AISI 321) | Stainless steel 1.4541 (AISI 321) |
| Weld end | Carbon steel St 37.2 | Boiler steel P265GH / P355GH | Stainless steel 1.4301 (AISI 304) |
| Inner liner (option) | Stainless steel AISI 321 | Stainless steel AISI 321 | Stainless steel AISI 321 |
| Connection | Welding | Welding | Welding |
Which material? The weld end material should be chosen according to the line pipe material and operating temperature. Values come from the metal bellows expansion joint manufacturer sheet; certification is provided on request.
Advantages
Permanent Seal
- No flange gasket
Compact
- Short flangeless length
High Temperature
- Up to 550 °C by material
Suited Underground
- Duct and buried lines
Construction and Design Features
- Stainless metal bellows
- Weld neck at both ends
- Inner flow liner (L series)
- Installation rods (depending on model)
Send the size, wall thickness, pressure, temperature and expansion; we will confirm a suitable weld neck expansion joint.
How to Choose?
- Size and weld endDetermine DN and pipe wall thickness.
- PressureCheck allowable pressure at temperature.
- Temperature and movementCalculate expansion and choose the series.
- MaterialChoose the weld end material by temperature.
Complementary Products
Why ORFA?
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