刀(dao)型(xing)閘(zha)閥(fa)(fa)的(de)啟閉件是(shi)閘(zha)板(ban)(ban)(ban)，閘(zha)板(ban)(ban)(ban)的(de)運(yun)動方(fang)向與流體方(fang)向相垂直，刀(dao)型(xing)閘(zha)閥(fa)(fa)只能作全(quan)開和全(quan)關(guan)，不(bu)能作調節(jie)和節(jie)流。閘(zha)板(ban)(ban)(ban)有(you)兩(liang)(liang)個密(mi)封(feng)(feng)面(mian)(mian)，zui常用的(de)模(mo)式(shi)閘(zha)板(ban)(ban)(ban)閥(fa)(fa)的(de)兩(liang)(liang)個密(mi)封(feng)(feng)面(mian)(mian)形(xing)成(cheng)楔形(xing)、楔形(xing)角(jiao)隨(sui)閥(fa)(fa)門(men)參數而異，通(tong)常為 50，楔式(shi)刀(dao)型(xing)閘(zha)閥(fa)(fa)的(de)閘(zha)板(ban)(ban)(ban)可以做成(cheng)一個整(zheng)體，叫做剛性(xing)閘(zha)板(ban)(ban)(ban);也可以做成(cheng)能產生(sheng)微量(liang)變形(xing)的(de)閘(zha)板(ban)(ban)(ban)，以改善其(qi)工(gong)藝性(xing)，彌補密(mi)封(feng)(feng)面(mian)(mian)角(jiao)度在加工(gong)過程中產生(sheng)的(de)偏差，這種(zhong)閘(zha)板(ban)(ban)(ban)叫做彈性(xing)閘(zha)板(ban)(ban)(ban)刀(dao)型(xing)閘(zha)閥(fa)(fa)關(guan)閉時，密(mi)封(feng)(feng)面(mian)(mian)可以只依靠(kao)介質壓(ya)力(li)來(lai)密(mi)封(feng)(feng)，即(ji)依靠(kao)介質壓(ya)力(li)將(jiang)閘(zha)板(ban)(ban)(ban)的(de)密(mi)封(feng)(feng)面(mian)(mian)壓(ya)向另一側的(de)閥(fa)(fa)座來(lai)保證密(mi)封(feng)(feng)面(mian)(mian)的(de)密(mi)封(feng)(feng)，這就是(shi)自(zi)密(mi)封(feng)(feng)。大部(bu)分(fen)刀(dao)型(xing)閘(zha)閥(fa)(fa)是(shi)采用強(qiang)制密(mi)封(feng)(feng)的(de)，即(ji)閥(fa)(fa)門(men)關(guan)閉時，要依靠(kao)外力(li)強(qiang)行將(jiang)閘(zha)板(ban)(ban)(ban)壓(ya)向閥(fa)(fa)座，以保證密(mi)封(feng)(feng)面(mian)(mian)的(de)密(mi)封(feng)(feng)性(xing)。