Single expansion joints are equipped with bellows elements and end connections such as pipe ends, flanges, weld necks and other optional features such as collars, liners and covers. The bellows will deflect in any direction or in any plane, depending on the motion of the pipe. This is a cost-effective design option, but requires the pipe to be controlled in the direction of movement of the bellows unit. Pipe expansion joints should not be expected to control the motion of the pipe. If the pipe analysis indicates that the pipe expansion joint must accept axial compression, the pipe must be guided and restrained so that only this movement occurs.
A single expansion joint is the cheapest element and will not resist any deformation other than the resistance of the bellows, which is a function of the spring stiffness times the amount of deflection. A single expansion joint does not resist a pressure thrust along its axis, which is the product of the pressure times the effective or cross-sectional area of the bellows.