蝶阀，从结构上分类，有中线式、偏心式（单偏心式、双偏心式和三偏心式）。

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

　　从其端部连接来说，有法兰端、对焊端、对夹式（Wafer或Lug）等。这里主要谈一下其结构分类及特点。

　　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.

　　下图。分别列出了中线型蝶阀、单偏式蝶阀、双偏心蝶阀、三偏心蝶阀。

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

　　中线式。蝶板中心轴线与阀体垂直中心线一致，橡胶等非金属压力阀体或阀座，蝶板外圈与软密封阀座挤压产生弹性变形，使阀门密封。优点是结构简单，操作方便，重量轻。缺点是密封性最差，温度、压力和介质的适应性受软密封面材料限制。

　　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.

　　单偏心式。蝶板中心轴线（介质流通的轴向）与阀体垂直中心线一致，但将蝶板沿介质流动的轴向偏离OFFSET1，即蝶板密封面与阀座密封面偏离蝶板中心轴线（阀体垂直中心线）。单偏心距OFFSET1的设置使蝶板与阀座密封面是一个完整的圆，启闭时密封面间机械磨损和挤压降低，密封性能、适用工作压力和使用寿命比中线式有所提高。

　　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.

　　缺点是（a）蝶板与阀座密封面发生机械摩擦，有擦伤，

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

　　（b）蝶板挤压阀座，弹性层会产生变形、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)结构较中线式复杂，成本高，

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

　　（d）介质会汽蚀、冲蚀密封面。

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

　　双偏心式。在单偏心的基础上，将蝶板转轴沿径向偏置OFFSET2，从而使蝶阀开启时机械磨损挤压降低，关闭时蝶板外圆密封面挤压阀座，具有较大、较好的密封比压；这种结构的密封性能较单偏心式好，使用压力也较高，使用寿命较长。

　　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.

　　缺点是

　　disadvantage

　　（a）蝶板与阀座密封面有机械磨损，也有擦伤，

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

　　（b）蝶板挤压阀座，软密封阀座的弹性变形会产生冷流失效等，

　　(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）结构较单偏心复杂，成本稍高，

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

　　（d）介质会汽蚀、冲蚀密封面。

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

　　三偏心式。在双偏心的基础上，将阀座中心线与阀体水平中心线形成OFFSET3的角度。开启时蝶板立即离开阀座密封面，关闭时仅在关闭瞬间蝶板密封面才会接触并压紧阀座密封面，两密封面之间的密封比压由偏心距和阀杆的转矩大小来决定。优点是密封性能和使用寿命大大提高，消除了蝶阀其他结构软密封阀座冷流弹性失效等因素。缺点是结构复杂、成本高，密封面受介质汽蚀。

　　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 上海良工阀门代理  友情奉献.更多有关的知识请点击  http://www.jnlgvf.com/   真诚的态度.为您提供为全面的服务.更多有关的知识我们将会陆续向大家奉献.敬请期待.

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