How Do Our Products Work?
An expansion joint, regardless of the type, is able to absorb movements in a piping or ducting system due to how the extra material is gathered up within the expansion joint itself. A metal bellows, for example, is constructed from a long thin metal tube that is transformed into convolutions in manufacture. These convolutions act as gathered material, allowing the expansion joint to absorb various movements. Fabric expansion joints have a similar gathering of extra material that allows for various movements in multiple directions.
Movements can be derived from machinery vibration, installation misalignment, seismic events, or, most common, thermal causes. Of all these causes, thermal movement is the simplest to predict. Many times, however, there is a combination of causes that create the total movement being experienced by the expansion joint. For this reason, we find it invaluable to observe the actual application in person and apply our experience and expertise in the design process.
With respect to the axis of the expansion joint, movements will either be axial (compression and/or extension), lateral (perpendicular to the axis of the expansion joint), or angular (rotating in a way to bend the expansion joint). While torsion (rotation about the axis of the expansion joint) is sometimes possible, expansion joints are not typically designed to absorb torsion movements. In most cases, the expansion joint must absorb a combination of movement directions.