一個排氣閥是一種裝置，調節，指導或控制流量的流體 （ 氣體 ， 液體 ， 流化床 固體或泥漿開幕）的，關閉或部分阻礙各個通道。 Valves are technically pipe fittings , but are usually discussed as a separate category.排氣閥在技術上管 件 ，但通常是作為一個單獨的討論范疇。 In an open valve, fluid flows in a direction from higher pressure to lower pressure.在打開的排氣閥，流體流動的方向，從更高的壓力，降低壓力。

      Valves are used in a variety of contexts, including industrial , military , commercial, residential, and transport .排氣閥是用在各種情況下的，包括工業 ， 軍事 ，商業，住宅和運輸 。 The industries in which the majority of valves are used are oil and gas , power generation , mining , water reticulation , sewerage and chemical manufacturing . ^{[ citation needed ]}該行業 ，其中大部分用于排氣閥是石油和天然氣 ， 發電 ， 采礦 ， 水網 ， 污水處理及化學制品制造業 ^{。[ 來源請求 ]}

      In daily life, most noticeable are plumbing valves, such as taps for tap water .在日常生活中，最引人注目的是管道排氣閥，這種水龍頭的自來水 。 Other familiar examples include gas control valves on cookers, small valves fitted to washing machines and dishwashers , safety devices fitted to hot water systems , and valves in car engines.其他熟悉的例子包括對灶具燃氣控制，小閥門安裝在洗衣機和洗碗機 ，安全裝置安裝在熱水系統 ，在汽車和發動機排氣閥。 In nature, veins acting as valves are controlling the blood circulation ; heart valves control the flow of blood in the chambers of the heart and maintain the correct pumping action.在自然界中， 靜脈作為排氣閥控制血液循環 ， 心臟瓣膜控制血液的流量在心室的 ，保持正確的抽水行動。

        Like in case of human body, in industry too, the valves play a very vital role, be it transportation of drinking water, or control of ignition in a rocket engine.就像人體的情況下，行業也是這樣，閥門起到非常重要的角色，無論是運輸飲用水，或在火箭發動機點火控制。

      Valves may be operated manually, either by a handle , lever or pedal.閥門可手動操作，或者通過一個手柄 ， 手柄或踏板。 Valves may also be automatic, driven by changes in pressure , temperature , or flow.閥門也可能是自動的，在推動的變化由壓力 ， 溫度或流量。 These changes may act upon a diaphragm or a piston which in turn activates the valve, examples of this type of valve found commonly are safety valves fitted to hot water systems or boilers .這些變化可能采取行動的一個膜片或活塞這反過來又激活閥門，閥門這種類型的例子，發現常見的有安全閥門安裝在系統或熱水鍋爐 。

More complex control systems using valves requiring automatic control based on an external input (ie, regulating flow through a pipe to a changing set point) require an actuator .更復雜的控制系統采用全自動控制閥，需要基于一個外部輸入（即，調節管道流經一個不斷變化的設定點）需要一個執行機構 。 An actuator will stroke the valve depending on its input and set-up, allowing the valve to be positioned accurately, and allowing control over a variety of requirements.行程執行器，閥門將其輸入并根據設置，使閥門被精確定位，并允許在一個控制的各種要求。

排氣閥