These provide a constant supporting force for piping throughout its full range of vertical movement due to expansion and contraction. This is accomplished through the use of a coil spring working in conjunction with a bell crank lever in such a way that the spring force times its distance to the lever pivot.
Because of its constancy in supporting effort the constant support is used where it is desirable to prevent pipe weight load transfer to connected equipment or adjacent support. Consequently it is used generally for the support of critical piping systems.