An expansion joint or expansion compensators is a device for compensating displacements produced by the expansion or contraction of the pipes and by the movement of the fluid that circulates through them. It is usually a flexible element, formed by one or more waves/arcs, designed to resist the internal pressure of a certain fluid at the working temperature, but flexible enough to absorb the movements that occur. It should not be confused with expansion joint"), a term used in construction to designate the spaces left between blocks, structures or prefabricated pieces, to avoid fragmentation of materials due to changes in temperature.

The fundamental element of an expansion joint is the bellows. The bellows must be strong enough to withstand the pressure of the fluid, and flexible enough to deform due to the difference in displacements or rotations at its ends.

Often the bellows is contained within a countertube that acts as a director to prevent lateral deformations and collaborates with the bellows to support internal pressure.

The main function of expansion joints, which are also known as construction joints, is to fill the gaps that are caused by the constant flow of vehicles on roads such as roads and highways. These are located on the separation lines of the structures or accesses with the main function of ensuring continuity in the roads and causing the sensation that structures such as bridges, roads or parking lots were made in a single section.

Expansion joints absorb movements in a piping system while it contains pressure and a fluid or medium passes through it.

Depending on the type of application, the bellows can be single-layer or multi-layer. Among the materials used for the composition of the layers we can find glass or ceramic fiber fabrics, silicone fabrics and laminates with fluoroplastic materials, among others.

There are three basic movements that can be absorbed by a Compensator:

Axial movement: the variation of the length of the bellows from its free or rest length in a direction parallel to its longitudinal axis.

Angular movement: the longitudinal axis of the expansion joint moves from its initial position in a straight line towards a circular arc.

Lateral movement: the two ends of a perpendicular expansion joint move to its longitudinal axis.

Expansion joints are used in a wide variety of sectors, the most common are:.