All systems can be subject to movement. These movements can vary from very slow (thermal expansion or contraction movements) to very fast (vibration). Thermal expansion can cause significant negative stress in pipes. The installation of an expansion joint can prevent these unwanted stress.
Basic concepts of an expansion joint.
The thermal expansion of a pipe is absorbed by the bellows of the expansion joint that is able to move according to different directions.
Axial movement: the expansion is absorbed along the longitudinal axis of the pipe.
L = free length of the bellows
-L = movement in compression
+ L = motion in elongation
Lateral movement: the expansion is absorbed along the transverse axis of the pipe.
L = free length of the bellows
Li = lateral movement
Angular movement: the dilation is absorbed along the pipe axis.
L = free length of the bellows
e = angular stroke