閥(fa)(fa)門(men)是管路(lu)流(liu)(liu)(liu)體(ti)(ti)(ti)輸(shu)送系統中控(kong)制部(bu)件(jian)，用(yong)(yong)(yong)來改變通(tong)路(lu)斷面和(he)介質流(liu)(liu)(liu)動方向，具有導流(liu)(liu)(liu)、截止、節流(liu)(liu)(liu)、止回、分流(liu)(liu)(liu)或溢流(liu)(liu)(liu)卸壓等(deng)功能。用(yong)(yong)(yong)于流(liu)(liu)(liu)體(ti)(ti)(ti)控(kong)制的(de)(de)閥(fa)(fa)門(men)，從最簡單的(de)(de)截止閥(fa)(fa)到(dao)極為(wei)復雜的(de)(de)自控(kong)系統中所用(yong)(yong)(yong)的(de)(de)各(ge)(ge)種(zhong)(zhong)閥(fa)(fa)門(men)，其品種(zhong)(zhong)和(he)規格繁多， 閥(fa)(fa)門(men)的(de)(de)公(gong)稱通(tong)徑(jing)從極微小(xiao)的(de)(de)儀表(biao)閥(fa)(fa)大至通(tong)徑(jing)達10m的(de)(de)工(gong)業管路(lu)用(yong)(yong)(yong)閥(fa)(fa)。可(ke)用(yong)(yong)(yong)于控(kong)制水(shui)、蒸(zheng)汽、油品、氣(qi)體(ti)(ti)(ti)、泥漿、各(ge)(ge)種(zhong)(zhong)腐蝕性(xing)介質、 液態(tai)金(jin)屬和(he)放射(she)性(xing)流(liu)(liu)(liu)體(ti)(ti)(ti)等(deng)各(ge)(ge)種(zhong)(zhong)類型(xing)流(liu)(liu)(liu)體(ti)(ti)(ti)地流(liu)(liu)(liu)動 ，閥(fa)(fa)門(men)的(de)(de)工(gong)作壓力可(ke)以從0.0013MPa到(dao)1000MPa 的(de)(de)超高(gao)壓，工(gong)作溫度可(ke)以c-270℃的(de)(de)超低溫到(dao)1430℃的(de)(de)高(gao)溫。

　　閥門的控制可采用多種(zhong)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)(dong)方式， 如(ru)手動(dong)(dong)(dong)(dong)(dong)、電(dian)動(dong)(dong)(dong)(dong)(dong)、液動(dong)(dong)(dong)(dong)(dong)、氣(qi)動(dong)(dong)(dong)(dong)(dong)、渦輪、電(dian)磁(ci)動(dong)(dong)(dong)(dong)(dong)、電(dian)磁(ci)液動(dong)(dong)(dong)(dong)(dong)、電(dian)液動(dong)(dong)(dong)(dong)(dong)、氣(qi)液動(dong)(dong)(dong)(dong)(dong)、正齒輪、傘齒輪驅動(dong)(dong)(dong)(dong)(dong)等；可以在(zai)壓力(li)、溫(wen)度或(huo)其(qi)它形式傳(chuan)(chuan)感(gan)信號的作(zuo)用下(xia)， 按預定的要求動(dong)(dong)(dong)(dong)(dong)作(zuo)，或(huo)者不(bu)依(yi)賴傳(chuan)(chuan)感(gan)信號而進行簡(jian)單的開(kai)啟(qi)或(huo)關(guan)閉(bi)，閥門依(yi)靠驅動(dong)(dong)(dong)(dong)(dong)或(huo)自動(dong)(dong)(dong)(dong)(dong)機構使啟(qi)閉(bi)件作(zuo)升降、滑移、旋擺或(huo)回(hui)轉運動(dong)(dong)(dong)(dong)(dong)， 從而改(gai)變其(qi)流道面積的大小(xiao)以實現其(qi)控制功能。