The design makes use of the working principle of difference in density of steam and condensate. The compound lever is connected to the inverted bucket inside the valve,working on steam pressure switch.The inverted bucket is a level sensor in the steam trap with opening downward.When the device starts up ,air and low-temperature condensate enter into the tube.At this time ,the trap is completely open,allowing quick discharge of air and low-temperature condensate and temperature rising. Steam entering into the inverted bucket causes it to float.and the lever arm drives the valve corce to close. A small vent in the bucket may automatically discharge the air.Some part of the steam will be discharged from the vent ,and other part of the steam will become condensate.The inverted bucket will sink without buoyant force, and then the lever arm will help the valve core to open the valve. When the valve is open , steam will get into the bucket again,causing the valve to close again. The device will work circularly and discharge water discontinuously.