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止回閥是能自動(dòng)阻止流體倒流的閥門(mén)。止回閥的閥瓣在流體壓力作用下開(kāi)啟，流體從進(jìn)口側(cè)流向出口側(cè)。當(dāng)進(jìn)口側(cè)壓力低于出口側(cè)時(shí)，閥瓣在流體壓差、本身重力等因素作用下自動(dòng)關(guān)閉以防止流體倒流。
止回閥一般分為升降式、旋啟式等幾種類型。
升降式止回閥的結(jié)構(gòu)一般與截止閥相似，其閥瓣沿著通道中心線作升降運(yùn)動(dòng)，動(dòng)作可靠，但流體阻力較大，適用于較小口徑的場(chǎng)合。升降式止回閥可分為直通式和立式兩種。直通式升降式止回閥一般只能安裝在水平管路，而立式升降止回閥一般應(yīng)安裝在垂直管路。
旋啟式止回閥的閥瓣繞轉(zhuǎn)軸作旋轉(zhuǎn)運(yùn)動(dòng)。其流體阻力一般小于升降式止回閥，它適用于較大口徑的場(chǎng)合。旋啟式止回閥根據(jù)閥瓣的數(shù)目可分為單瓣旋啟式、雙瓣旋啟式及多瓣旋啟式三種。單瓣旋啟式止回閥一般適用于中等口徑的場(chǎng)合。大口徑管路選用單瓣旋啟式止回閥時(shí)，為減少水錘壓力，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。對(duì)夾雙瓣旋啟式止回閥結(jié)構(gòu)小、重量輕，是一種發(fā)展較快的止回閥；多瓣旋啟式止回閥適用于大口徑管道路。

主要零件材料及性能規(guī)范

主要零部件	閥體、閥蓋、搖桿	WCB	CF8	CF8M	WC6、WC9
	閥瓣	WCB堆Cr13或硬質(zhì)合金	CF8堆硬質(zhì)合金	CF8M堆硬質(zhì)合金	WC6、WC9堆硬質(zhì)合金
	閥座	25堆Cr13或硬質(zhì)合金	304堆硬質(zhì)合金	316堆硬質(zhì)合金	20Cr1MoV堆硬質(zhì)合金
	墊片	軟鐵、XB450	聚四氟乙烯	聚四氟乙烯	不銹鋼+耐酸石棉纏繞墊
	螺栓	35CrMoA	35CrMoA	35CrMoA	25Cr1Mo1V
	螺母	45	45	45	35CrMoA
主要參數(shù)	適用介質(zhì)	油品、水、蒸汽	硝酸類	醋酸類	油品、水、蒸汽
主要參數(shù)	適用溫度 ℃	≤425	≤200	≤200	≤550

型號(hào)	公稱通徑 NPS(in)	壓力級(jí) Class	主要結(jié)構(gòu)尺寸(mm)					閥體材料	性能規(guī)范
型號(hào)	公稱通徑 NPS(in)	壓力級(jí) Class	D	D₁	L	L₁	H	閥體材料	適用溫度(℃)	適用介質(zhì)
SFH-64C150C	2"	150			203		170	WCB	≤425	水、油品、蒸氣等
"	3"	"			241		185	"	"	"
"	4"	"			292		215	"	"	"
"	6"	"			356		260	"	"	"
"	8"	"			495		300	"	"	"
"	10"	"			622		350	"	"	"
"	12"	"			699		400	"	"	"
"	14"	"			787		450	"	"	"
"	16"	"			864		480	"	"	"
"	18"	"			978		540	"	"	"
"	20"	"			978		600	"	"	"
"	24"	"			1295		680	"	"	"
SFH-64C300C	2"	300			267		170	WCB	≤425	水、油品、蒸氣等
"	3"	"			318		215	"	"	"
"	4"	"			356		235	"	"	"
"	6"	"			445		300	"	"	"
"	8"	"			533		340	"	"	"
"	10"	"			622		350	"	"	"
"	12"	"			711		420	"	"	"
"	14"	"			838		480	"	"	"
"	16"	"			864		520	"	"	"
"	18"	"			978		600	"	"	"
"	20"	"			1016		670	"	"	"
"	24"	"			1346		750	"	"	"
SFH-64C600C	2"	600			292		175	WCB	≤425	水、油品、蒸氣
"	3"	"			356		230	"	"	"
"	4"	"			432		295	"	"	"
"	6"	"			559		360	"	"	"
"	8"	"			660		400	"	"	"
"	10"	"			787		460	"	"	"
"	12"	"			838		520	"	"	"
"	14"	"			889		560	"	"	"
"	16"	"			991		650	"	"	"
"	18"	"			1092		730	"	"	"
"	20"	"			1194		800	"	"	"
"	24"	"			1397		900	"	"	"