Axial movement
Axial movement is considered as an elongation or compression of the pipe system in its longitudinal axis, meaning that in the process of absorbing the movements, the overall length of the expansion joint will either extend or compress.
Axial expansion joints which are designed to absorb large movements, can contain one, two or several bellows in one unit, and larger movements can also be achieved by pre-tensioning or by installing several expansion joints on the pipe section. Depending on the nominal diameter and length, axial expansion joints have the ability to absorb minor lateral and angular deflections and installation tolerances. However, we recommend the utilisation should be limited to axial expansion joints main function, otherwise its service life may be negatively impaired.
Where there is a need for absorption other than that of axial movements, we strongly recommend alternative options and Belman will be pleased to provide its professional advice.
Definitions
Axial movement is shown as AX and stated in mm. Compression and elongation are indicated as negative (-) and positive (+).
Example
Elongation +10 and compression -20 will be shown as: AX +10/-20 mm. Equal longitudinal movements are shown as: AX +/-20 mm (2δN).
Having the ability to compensate for axial movements and with its simple and compact overall dimensions, axial expansion joints are very widely used within a range of applications. Axial expansion joints are especially common in long pipe runs, examples of which would include exhaust systems, ventilation and flue gas systems, district heating, steam, oil and gas pipe systems.