During the initial operation stage, the disk will be lifted by medium pressure and cold condensed water and air will be drained immediately.  Once hot condensed water come into the trap, part of the condensed water will be evaporated again. Fast flowing condensed water or evaporated steam flow will drop the pressure of lower part of disk and the disk will be draw down to sheet side.  At the same time, the evaporated steam will inflow into the upper part of disk chamber, create a pressure, and close the valve instantly against the condensed water pressure. Then, the pressure in the chamber will be decreased by the evaporated steam condensing and will lift the sheet again.  These cycles will be repeated and the trap keeps working.