In Cascading system we can use the flash steam from one group to the another group by maintaining ΔP (pressure difference). ∆P=P1 -P2 (P1 = First live steam pressure, P2 = Second group steam pressure). ΔP of this system must be 0.5 to 0.8 depends on the rotary joint design. If we cant get the sufficient heat transfer in second group. We can add more steam with the use of control valve by maintaining the ΔP. In Cascading system the high pressure steam isn’t necessary for vacuum the flash steam. In this system, We have to make more groups to get the maximum benefit of the flash steam.