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An expansion joint absorbs relative movement within a piping system. Depending on its type it can take up axial, lateral or angular movement.
An expansion joint is a deliberately flexible piece of piping. It absorbs movements the pipe itself could not accommodate without high forces: thermal expansion, settlement, vibration from machinery. To do so it is softer and thinner than the line – and therefore the component that needs the most careful design, installation and monitoring.
Every expansion joint is built for particular movements. Axial means the line becomes shorter or longer along its axis. Lateral means the two ends shift sideways relative to each other. Angular means the ends rotate relative to each other about a transverse axis.
Several hinged or lateral joints can be arranged as systems that absorb large movements while transmitting only small forces. Hardly any type, however, tolerates torsion about the pipe axis.
An expansion joint never works alone. An unrestrained axial joint is pushed apart by internal pressure; anchors have to carry that force. Guides have to prevent the line from buckling at the soft spot. If either is missing, the first pressurisation destroys the joint or displaces the line.
Restrained types with tie rods or hinges carry the pressure force themselves and relieve the anchors. In exchange, they cannot absorb axial movement.
Where there is room, a pipe best accommodates its expansion through its routing – with changes of direction and expansion loops. The expansion joint is the answer for cases where that is impossible or insufficient.
Expansion joints are designed for a certain number of cycles at certain movements. Larger movements, higher temperatures or additional vibration shorten their life. Elastomers also age regardless of loading.
An expansion joint therefore belongs in the inspection plan of the plant and should be installed so that it can be inspected and replaced. It is not intended to compensate for installation errors: every millimetre of misalignment it takes up during installation is missing in service.
What Entracon offers here is on the matching page.
See what we offer| Type | Typical use | Limits |
|---|---|---|
| Metal bellows | Steam, hot fluids, higher pressures | Sensitive to torsion and to corrosion of the thin bellows wall |
| Rubber expansion joint | Water, pump connections, vibration isolation | Limited temperature, ageing of the elastomer |
| Fabric expansion joint | Flue gas and air ducts | Very low pressures only |
| PTFE expansion joint | Aggressive fluids in chemical plants | Limited pressure and temperature |
No. It should be inspected regularly for deformation, corrosion, cracks and the condition of tie rods and hinges. Rubber expansion joints are additionally assessed by age.
Yes, but not without a new analysis. An expansion joint changes the forces throughout the line and calls for anchors and guides that were not needed before.
Expansion joint is the general term for all such devices. The bellows expansion joint is the type with a metal bellows – the most common one for hot fluids in process plants.
If the line has no anchors to carry the pressure force, yes. Without a length restraint, internal pressure stretches the joint and loads the pump nozzle it was meant to relieve.
One short conversation usually settles more than three quotations. Call or write — you will reach an engineer directly.
Start typing – for example “balancer”, “SAP” or “pipe stress”.
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