限流孔(kong)板(ban)（Restriction Orifice）是在板(ban)面上開一(yi)個小錐孔(kong)（該小錐孔(kong)的(de)尺寸由工藝專業提出），如圖(tu)4-19所示。它也應(ying)有兩個和匹配法(fa)蘭同樣(yang)的(de)密封面。限流孔(kong)板(ban)可以作為流量(liang)測量(liang)(liang)元(yuan)(yuan)件(jian)用來測量(liang)(liang)流(liu)(liu)(liu)量(liang)(liang)，也可(ke)以作為(wei)節流(liu)(liu)(liu)元(yuan)(yuan)件(jian)用來限定(ding)(ding)流(liu)(liu)(liu)量(liang)(liang)和(he)降(jiang)低壓(ya)(ya)力(li)(li)。當孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)前后存在一(yi)定(ding)(ding)壓(ya)(ya)差(cha)(cha)(cha)，流(liu)(liu)(liu)體流(liu)(liu)(liu)經孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)，對于一(yi)定(ding)(ding)的孔(kong)(kong)徑(jing)，流(liu)(liu)(liu)經孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)的流(liu)(liu)(liu)量(liang)(liang)隨著壓(ya)(ya)差(cha)(cha)(cha)增(zeng)(zeng)大而增(zeng)(zeng)大。但當壓(ya)(ya)差(cha)(cha)(cha)超過某一(yi)數值（稱為(wei)臨界壓(ya)(ya)差(cha)(cha)(cha)）時(shi)，流(liu)(liu)(liu)體通(tong)過孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)縮孔(kong)(kong)處的流(liu)(liu)(liu)速達到音速，這(zhe)時(shi)，無論壓(ya)(ya)差(cha)(cha)(cha)如何增(zeng)(zeng)加，流(liu)(liu)(liu)經孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)的流(liu)(liu)(liu)量(liang)(liang)將維持在一(yi)定(ding)(ding)數值而不再(zai)增(zeng)(zeng)加。限流(liu)(liu)(liu)孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)就是根(gen)據這(zhe)一(yi)原理來限定(ding)(ding)流(liu)(liu)(liu)體的流(liu)(liu)(liu)量(liang)(liang)和(he)降(jiang)低壓(ya)(ya)力(li)(li)的。限流(liu)(liu)(liu)孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)按孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)上開(kai)孔(kong)(kong)數量(liang)(liang)分為(wei)單孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)和(he)多孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)；按孔(kong)(kong)板(ban)(ban)(ban)(ban)(ban)數量(liang)(liang)可(ke)分為(wei)單級(ji)和(he)多級(ji)。


圖 19.jpg


 限流(liu)孔板主要使用在下列(lie)場合：


   ①. 工藝物料需(xu)要降壓的(de)場合。


   ②. 在管道中閥(fa)門(men)(men)上、下游(you)需要有較大壓降時，為(wei)減少流體對閥(fa)門(men)(men)的沖蝕，當經孔板(ban)節流不(bu)會產生(sheng)氣相時，可在閥(fa)門(men)(men)上游(you)串(chuan)聯孔板(ban)。


   ③. 流體需(xu)要小流量且連(lian)續流通的地方，如泵的沖洗管(guan)(guan)道、熱備用(yong)泵的旁路管(guan)(guan)道（低(di)流量保護管(guan)(guan)道）、分析(xi)取樣管(guan)(guan)等場所(suo)。


   ④. 需要降壓以減少噪聲或磨(mo)損的地方，如放空系(xi)統。


  限流孔板有關的(de)標準有：HG/T 20570.15、ISO 5167和GB/T 2624。



 混合(he)(he)孔板（Mixing Orifice）是在(zai)(zai)板面(mian)上開設一個或若(ruo)干個小(xiao)孔，以(yi)便于兩(liang)種介質在(zai)(zai)經過混合(he)(he)孔板時(shi)能充分混合(he)(he)而達到工藝操作的(de)(de)(de)目的(de)(de)(de)。它也應有(you)兩(liang)個和匹配法蘭(lan)同樣的(de)(de)(de)密封(feng)面(mian)。