District heating expansion joints are designed to take up mainly axial movements caused by temperature expansions of the pipeline. The expansion joints are suitable for both trenched/trenchless pipelines, are reliable in operation and do not require any maintenance.
A highly flexible bellow is a main component of district heating expansion joints, ensuring compensation of large axial movements. A solid casing and guides/rings mounted on the expansion joints serves multiple functions for example; the protection of the bellows from mechanical damages, higher bellow stability and the absorption of eventual misalignments in the pipeline. An inner sleeve protects the bellows against internal abrasives such as sand and dirt particles which are often carried by district heating water, settling between the convolutions which can prevent the bellows from their intended function. Furthermore, the expansion joints have a safeguard preventing torsion on the bellows and other unintended loads, and thus ensuring a longer service life.
The basic design can be additionally reinforced, so the expansion joints would be able to absorb additional loads coming from the pipeline. Consequently, this will result in the saving of the first guide supporting the pipeline, normally placed at 4 x DN from the expansion joint to a distance of 10 x DN. The reinforcement is obtained through a more solid construction, more specifically the casing and inner sleeve.