自動差壓冷凝水控制閥疏水閥簡稱 (DC) 係設計應用於冷凝水排放點低必須上揚或快速排放的機器，由於排放點低須將冷凝水提昇上揚通常稱為虹吸。 當冷凝水上揚時造成了壓力降低時會引起部份的蒸汽及二次蒸汽被入虹吸管中。因疏水閥它不會分辨蒸汽、空汽式，只要是氣體它就關閉造成空汽閉鎖 AIR BIND ING ) ，阻礙了後面來的冷凝水排放。水的抗阻為鋼板 60 倍，空氣的抗阻是鋼板的 160 倍。 DC 將有助於快速時二次蒸汽及空汽引至冷凝水控制室經旁通 (BYFASS) 排放出的蒸汽可導至冷凝水回收管或收集筒作為其他低壓低溫使用。 ( 圖 c-l) DC 特別適用於滾筒烘乾機 ( 圖 C-2) 可將 2 、 3 、 4 、 5 、 6 滾筒內經旁通 (BY PASS) 所排放出的二次蒸汽餵 1 滾筒，可達到節省能源的目地。

FLYGIN Automatic Differential Condensate Control Valve Trap, also known as DC, is especially designed for the applications in which either the low discharging location level of condensate has to be highered or the water has to be discharged rapidly. Usually the discharging location level is low, therefore, it is necessary to elevate the condensate, and such elevation is usually known as "siphon". When condensate ascends the pressure is lowered, under such circumstances some portion of steam is in taken into the siphon tube. Howeer, a typical trap shuts automatically whenever it senses any air or steam because a trap is unable to differ steam from air, such unwanted shutting causes Air Binding which stops any further condensate following from being discharged. As we are aware, Water REsistance is about 60 times of that of steel, while Air Resistance is about 160 times of that of steel. A DC fa cilitates the system with rapidly guiding the Secondary Steam and Air into the Condensate Control Chamber. The steam being discharged through the by-Pass is guided to the Condensate Recollection Tube or Strainer for applications under low pressure and low temperature circumstances. (As shown in Fig. C-1) A FLYGIN DC is especially excellent for the energy saving design for Cylindrical Dryers (as shown in Fig. C-2). The Secondary Steam being discharged from Roller 2,3,4,5, and 6 through the respective( By-Pass) can be led into Roller 1 so as to save energy substantially.