Direct-burial expansion joint, primarily used for axial compensation of buried pipelines, has bending resistance, thus the influence of pipeline settlement is not considered.

When in use, it's important to note that the buried bellows compensator requires only one bellows compensator to be installed between the two fixed supports. The calculation of the force exerted by the compensator on the supports is the same as that of a single bellows compensator. This is due to the buried bellows compensator's characteristics of achieving compensation on the pipeline and being easy to install.

The bellows is made of 1Cr18Ni9Ti stainless steel, suitable for installation on pipelines operating at temperatures below 350°C, pressures between 0.25~25MPa, and nominal diameters of DN100~600mm. However, the most commonly used are the pipe projects with PN0.2, 0.5, and 1.0MPa ratings, and pipe diameters of DN50~500mm.

To reduce the flow resistance of the medium, minimize erosion under high-speed flow conditions, or to avoid resonance caused by undulations, a compensator with an inner sleeve should be used when the nominal diameter DN is 150mm or more, and the gas (or air) velocity v is 8m/s or the liquid velocity v is 3m/s or more.

Direct-burial expansion joints can be custom-made to meet customer requirements.