Checkvalves止回閥止回閥在管路系統中的主要作用是防止介質倒流而造成泵及其驅動電機機反轉，防止容器內介質的泄放。止回閥還可用于壓力可能超過主系統壓力的輔助系統管路上Themainroleofcheckvalvesinthepipingsystemistopreventthebackflowofmediaandcausethepumpanditsdrivemotormachinereversal,topreventthereleaseofmediainthecontainer.Checkvalvecanalsobeusedintheauxiliarysystempipelinewherethepressuremayexceedthemainsystempressure.止回閥又稱為逆流閥、逆止閥、背壓閥、單向閥。這類閥門靠管路中介質本身的流動產生的力而自動開啟和關閉，屬于自動閥門的一種。Checkvalveisalsocalledbackflowvalve,checkvalve,backpressurevalve,checkvalve.Thesevalvesrelyontheforcegeneratedbytheflowofthemediumitselfinthepipelineandautomaticallyopenandclose,belongingtoakindofautomaticvalve.止回閥的工作原理Principleofoperationofcheckvalves止回閥的分類Classificationofcheckvalves止回閥根據其結構和安裝方式可分為旋啟式、升降式、碟式和管道式四種形式。Checkvalvescanbedividedintofourforms:swingtype,lifttype,disctypeandpipelinetypeaccordingtotheirstructureandinstallationmethod.圖為升降式Liftingtype圖為旋啟式Swing-opentype圖為碟式Disc圖為管道式Pipelinetype1.旋啟式止回閥Swing-opencheckvalve止回閥的分類Classificationofcheckvalves旋啟式止回閥的閥瓣呈圓盤狀，繞閥座通道的轉軸作旋轉運動，因閥內通道成流線型，流動阻力比升降式止回閥小，適用于低流速和流動不常變化的大口徑場合，但不宜用于脈動流，其密封性能不及升降式。Swingcheckvalveflapisdisc-shaped,rotatingmovementaroundtheaxisofthevalveseatchannel,becausethevalvechannelintostreamline,flowresistancethanliftcheckvalveissmall,suitableforlowflowrateandflowdoesnotoftenchangethelargediameteroccasions,butnotforpulsatingflow,itssealingperformanceisnotasgoodaslifttype.旋啟式止回閥分單瓣式、雙瓣式和多瓣式三種。單瓣旋啟式止回閥一般適用于中等口徑的場合，大口徑管路選用單瓣旋啟式止回閥時，為減少水錘壓力，最好采用能減小水錘壓力的緩閉止回閥；雙瓣旋啟式止回閥適用于大中口徑管路；多瓣旋啟式止回閥適用于大口徑管路。Swingcheckvalveisdividedintosingle,doubleandmulti-flaptypethree.Single-valveswingcheckvalveisgenerallysuitableformediumcaliberoccasions,largediameterpipelineselectionofsingle-valveswingcheckvalve,inordertoreducewaterhammerpressure,itisbesttousetheslow-closingcheckvalvetoreducewaterhammerpressure;double-valveswingcheckvalveforlargeandmediumdiameterpipeline;multi-valveswingcheckvalveforlargediameterpipeline.旋啟式止回閥及其結構示意圖如圖所示。

Swing-opencheckvalveanditsstructureschematicdiagramisshowninthefigure.止回閥的分類Classificationofcheckvalves止回閥的分類Classificationofcheckvalves2.升降式止回閥Liftcheckvalve為閥瓣沿著閥體垂直中心線滑動的止回閥。升降式止回閥的閥體形狀與截止閥一樣（可與截止閥通用），其結構與截止閥相似，閥體和閥瓣與截止閥相同。Acheckvalveforwhichthevalveflapslidesalongtheverticalcenterlineofthevalvebody.Thebodyshapeoftheliftcheckvalveisthesameastheglobevalve(canbecommonwiththeglobevalve),itsstructureissimilartotheglobevalve,andthevalvebodyandvalveflaparethesameastheglobevalve.止回閥的分類Classificationofcheckvalves升降式止回閥閥瓣上部和閥蓋下部有導向套筒，閥瓣導向筒可在閥蓋導向筒內自由升降。當介質順流時，閥瓣靠介質推力開啟；Theupperpartofthevalveflapandthelowerpartofthevalvecoverhaveguidesleeves,andthevalveguidecylindercanbefreelyliftedinthevalvecoverguidecylinder.Whenthemediumflow,thevalveflapopensbythemediumthrust.當介質停流時，介質作用在閥瓣的壓力加上自身重力大于閥前的壓力時，閥瓣降落在閥座上，起阻止介質逆流作用。Whenthemediumstopsflowing,thepressureofthemediumactingonthevalveflapplusitsowngravityisgreaterthanthepressureinfrontofthevalve,thevalveflaplandsonthevalveseatandplaysaroleinstoppingthebackflowofthemedium.止回閥的分類Classificationofcheckvalves直通式升降止回閥介質進出口通道方向與閥座通道方向垂直；Straightliftcheckvalvemediaimportandexportchanneldirectionandseatchanneldirectionperpendicular對于立式升降式止回閥，其介質進出口通道方向與閥座通道方向相同，其流動阻力較直通式小，升降式止回閥及其結構示意圖如圖所示。升降式止回閥只能安裝在水平管道上。Forverticalliftcheckvalve,itsmediaimportandexportchanneldirectionandseatchanneldirectionisthesame,itsflowresistanceissmallerthanthestraight-throughtype,liftcheckvalveanditsstructureschematicdiagramasshowninthefigure.Liftcheckvalvecanonlybeinstalledonthehorizontalpipeline.為閥瓣圍繞閥座內的銷軸旋轉的止回閥。碟式止回閥結構簡單，流阻較小，水錘壓力亦較小。但只能安裝在水平管道上，密封性較差。Itisacheckvalvewherethevalveflaprotatesaroundapininthevalveseat.Thedisccheckvalvehasasimplestructure,lowflowresistance,andlowwaterhammerpressure.However,itcanonlybeinstalledonhorizontalpipingandhaspoorsealing.碟式止回閥如圖所示。Thedisctypecheckvalveisshowninthefigure.止回閥的分類Classificationofcheckvalves4.管道式止回閥Pipe-typecheckvalve止回閥的分類Classificationofcheckvalves3.碟式止回閥Disctypecheckvalve管道式止回閥為閥瓣沿閥體中心線滑動的閥門。管道式止回閥是一種新型閥門，具有體積小，重量較輕，加工工藝性好的特點，是止回閥的發展方向之一。Pipe-typecheckvalveisavalvewhosevalveflapslidesalongthecenterlineofthevalvebody.Pipe-typecheckvalveisanewtypeofvalvewithsmallvolume,lightweightandgoodprocessability,whichisoneofthedevelopmentdirectionofcheckvalve.但其流體阻力系數比旋啟式止回閥略大，管道式止回閥如圖所示。However,itsfluidresistancecoefficientisslightlylargerthanthatofswingcheckvalve,pipe-typecheckvalveasshowninthefigure.止回閥安裝與維護Checkvalveinstallationandmaintenance止回閥的安裝應注意以下事頂：Theinstallationofthecheckvalveshouldpayattentiontothefollowingthingstop.（1）在管線中不要使止回閥承受重量，大型的止回閥應獨立支撐，使之不受管系統產生的壓力的影響；Donotsubjectcheckvalvestoweightinthepipeline,andlargecheckvalvesshouldbeindependentlysupportedsothattheyarenotaffectedbythepressuregeneratedbythepipesystem.（2）安裝時，注意介質流動的方向應與閥體所標箭頭方向一致；Wheninstalling,notethatthedirectionofmediaflowshouldbeconsistentwiththedirectionofthearrowmarkedonthevalvebody.圖為止回閥的安裝示意圖Installationdiagramofcheckvalve止回閥安裝與維護Checkvalveinstallationandmaintenance（3）升降式垂直瓣止回閥應安裝在垂直管道上；Liftingverticalflapcheckval