蝶閥，從結構上分類，有中線式、偏心式（單偏心式、雙偏心式和三偏心式）。

　　Butterfly valves can be classified structurally into midline type, eccentric type (single eccentric, double eccentric, and triple eccentric).

　　從其端部連接來說，有法蘭端、對焊端、對夾式（Wafer或Lug）等。這里主要談一下其結構分類及特點。

　　In terms of end connections, there are flange ends, butt welded ends, wafer or Lug type connections, etc. Here we will mainly discuss its structural classification and characteristics.

　　下圖。分別列出了中線型蝶閥、單偏式蝶閥、雙偏心蝶閥、三偏心蝶閥。

　　The following picture. Listed are medium line butterfly valves, single eccentric butterfly valves, double eccentric butterfly valves, and triple eccentric butterfly valves.

　　中線式。蝶板中心軸線與閥體垂直中心線一致，橡膠等非金屬壓力閥體或閥座，蝶板外圈與軟密封閥座擠壓產生彈性變形，使閥門密封。優點是結構簡單，操作方便，重量輕。缺點是密封性最差，溫度、壓力和介質的適應性受軟密封面材料限制。

　　Mid line style. The center axis of the butterfly plate is consistent with the vertical center line of the valve body. The non-metallic pressure valve body or valve seat made of rubber, the outer ring of the butterfly plate and the soft seal valve seat are compressed to produce elastic deformation, which seals the valve. The advantages are simple structure, easy operation, and light weight. The disadvantage is that the sealing performance is the worst, and the adaptability of temperature, pressure, and medium is limited by the soft sealing surface material.

　　單偏心式。蝶板中心軸線（介質流通的軸向）與閥體垂直中心線一致，但將蝶板沿介質流動的軸向偏離OFFSET1，即蝶板密封面與閥座密封面偏離蝶板中心軸線（閥體垂直中心線）。單偏心距OFFSET1的設置使蝶板與閥座密封面是一個完整的圓，啟閉時密封面間機械磨損和擠壓降低，密封性能、適用工作壓力和使用壽命比中線式有所提高。

　　Single eccentric type. The center axis of the butterfly plate (the axis of medium flow) is aligned with the vertical center line of the valve body, but the butterfly plate is offset from OFFSET1 along the axis of medium flow, that is, the sealing surface of the butterfly plate and the sealing surface of the valve seat are offset from the center axis of the butterfly plate (the vertical center line of the valve body). The setting of single eccentricity OFFSET1 makes the sealing surface between the butterfly plate and the valve seat a complete circle. During opening and closing, mechanical wear and compression between the sealing surfaces are reduced, and the sealing performance, applicable working pressure, and service life are improved compared to the midline type.

　　缺點是（a）蝶板與閥座密封面發生機械摩擦，有擦傷，

　　The disadvantage is that (a) there is mechanical friction between the butterfly plate and the valve seat sealing surface, resulting in scratches,

　　（b）蝶板擠壓閥座，彈性層會產生變形、冷流等失效，

　　(b) When the butterfly plate squeezes the valve seat, the elastic layer will deform and fail due to cold flow,

　　(c)結構較中線式復雜，成本高，

　　(c) The structure is more complex and costly than the linear type,

　　（d）介質會汽蝕、沖蝕密封面。

　　(d) The medium will cause cavitation and erosion of the sealing surface.

　　雙偏心式。在單偏心的基礎上，將蝶板轉軸沿徑向偏置OFFSET2，從而使蝶閥開啟時機械磨損擠壓降低，關閉時蝶板外圓密封面擠壓閥座，具有較大、較好的密封比壓；這種結構的密封性能較單偏心式好，使用壓力也較高，使用壽命較長。

　　Double eccentric type. On the basis of single eccentricity, the rotating shaft of the butterfly plate is radially offset by OFFSET2, so that the mechanical wear and compression of the butterfly valve are reduced when it is opened, and the outer sealing surface of the butterfly plate presses against the valve seat when it is closed, resulting in a larger and better sealing pressure ratio; This structure has better sealing performance than the single eccentric type, higher operating pressure, and longer service life.

　　缺點是

　　disadvantage

　　（a）蝶板與閥座密封面有機械磨損，也有擦傷，

　　(a) The sealing surface between the butterfly plate and the valve seat has mechanical wear and scratches,

　　（b）蝶板擠壓閥座，軟密封閥座的彈性變形會產生冷流失效等，

　　(b) The butterfly plate compresses the valve seat, and the elastic deformation of the soft seal valve seat can cause cold flow failure, etc,

　　（c）結構較單偏心復雜，成本稍高，

　　(c) The structure is more complex than single eccentricity, and the cost is slightly higher,

　　（d）介質會汽蝕、沖蝕密封面。

　　(d) The medium will cause cavitation and erosion of the sealing surface.

　　三偏心式。在雙偏心的基礎上，將閥座中心線與閥體水平中心線形成OFFSET3的角度。開啟時蝶板立即離開閥座密封面，關閉時僅在關閉瞬間蝶板密封面才會接觸并壓緊閥座密封面，兩密封面之間的密封比壓由偏心距和閥桿的轉矩大小來決定。優點是密封性能和使用壽命大大提高，消除了蝶閥其他結構軟密封閥座冷流彈性失效等因素。缺點是結構復雜、成本高，密封面受介質汽蝕。

　　Triple eccentric type. On the basis of double eccentricity, form an angle of OFFSET3 between the centerline of the valve seat and the horizontal centerline of the valve body. When opened, the butterfly plate immediately leaves the valve seat sealing surface. When closed, the butterfly plate sealing surface only contacts and presses against the valve seat sealing surface at the moment of closure. The sealing pressure between the two sealing surfaces is determined by the eccentricity and the torque of the valve stem. The advantage is that the sealing performance and service life are greatly improved, eliminating factors such as cold flow elastic failure of other soft seal valve seats in butterfly valves. The disadvantages are complex structure, high cost, and the sealing surface is susceptible to cavitation of the medium.

　　本文由 上海良工閥門代理  友情奉獻.更多有關的知識請點擊  http://www.wxdhmb.com.cn/   真誠的態度.為您提供為全面的服務.更多有關的知識我們將會陸續向大家奉獻.敬請期待.

　　This article is a friendly contribution from Shanghai Lianggong Valve Agency For more related knowledge, please click http://www.wxdhmb.com.cn/ Sincere attitude To provide you with comprehensive services We will gradually contribute more relevant knowledge to everyone Coming soon.