止回閥是能自動阻止流體倒流的閥門。止回閥的閥瓣在流體壓力作用下開啟，流體從進口側流向出口側。當進口側壓力低於出口側時，閥瓣在流體壓差、本身重力等因素作用下自動關閉以防止流體倒流。
止回閥一般分為升降式、旋啟式等幾種類型。
升降式止回閥的結構一般與截止閥相似，其閥瓣沿著通道中心線作升降運動，動作可靠，但流體阻力較大，適用於較小口徑的場合。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安裝在垂直管路。
旋啟式止回閥的閥瓣繞轉軸作旋轉運動。其流體阻力一般小於升降式止回閥，它適用於較大口徑的場合。旋啟式止回閥根據閥瓣的數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於中等口徑的場合。大口徑管路選用單瓣旋啟式止回閥時，為減少水錘壓力，最好採用能減小水錘壓力的緩閉止回閥。雙瓣旋啟式止回閥適用於大中口徑管路。對夾雙瓣旋啟式止回閥結構小、重量輕，是一種發展較快的止回閥；多瓣旋啟式止回閥適用於大口徑管道路。
主要零件材料及性能規範
主 要 零 部 件 | 閥體、閥蓋、搖桿 | WCB | CF8 | CF8M | WC6、WC9 |
閥瓣 | WCB堆Cr13或硬質合金 | CF8堆硬質合金 | CF8M堆硬質合金 | WC6、WC9堆硬質合金 | |
閥座 | 25堆Cr13或硬質合金 | 304堆硬質合金 | 316堆硬質合金 | 20Cr1MoV堆硬質合金 | |
墊片 | 軟鐵、XB450 | 聚四氟乙烯 | 聚四氟乙烯 | 不鏽鋼+耐酸石棉纏繞墊 | |
螺栓 | 35CrMoA | 35CrMoA | 35CrMoA | 25Cr1Mo1V | |
螺母 | 45 | 45 | 45 | 35CrMoA | |
主要參數 | 適用介質 | 油品、水、蒸汽 | 硝酸類 | 醋酸類 | 油品、水、蒸汽 |
適用溫度 ℃ | ≤425 | ≤200 | ≤200 | ≤550 |
型號 | 公稱 通徑 NPS(in) | 壓力級 Class | 主要結構尺寸(mm) | 閥體 材料 | 性能規範 | |||||
D | D1 | L | L1 | H | 適用溫度(℃) | 適用介質 | ||||
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 | " | " | " |
