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原文
Butterfly valve for low temperature sealing performance requirements Cryogenic valves leak, there are two main reasons for the situation, one leakage; second leak. 1) within the drain valve generated The main reason is sealing at low temperature due to deformation. When the medium temperature dropped to the material phase change caused by volume changes, so that the original sealing surface with high precision grinding resulting warpage caused by low-temperature sealing bad. We had DN250 valve for low temperature experiments, the medium is liquid nitrogen (-196 ℃) disc material 1Cr18Ni9Ti (not through the low-temperature treatment) found that warpage of the sealing surface amounted to about 0.12mm, which is the main cause of leakage . The newly developed valve cone from the flat seal to seal. Oblique elliptical cone seat is a sealing surface, and embedded board is mounted on the butterfly circle composed of elastic sealing ring sealing. Seal ring groove in the disc radial float. When the valve is closed, the first elastic sealing ring and sealing surface of the short axis of elliptical contact with the valve stem seal ring gradually turning inward push force and the elastic ring and then the long axis of the oblique cone surface contact, eventually leading to elastic sealing oval ring and all contact with the sealing surface. It is to rely on elastic sealing ring deformation and to achieve. So when the body or disc deformation at low temperatures, the elastic sealing ring will be to absorb the compensation, will not leak and stuck. When the elastic deformation of the valve is opened immediately disappeared in the process of opening and closing relatively little friction, so long life. 2) the valve leakage. One is the use of valves and pipe flange connections, because connections litter, bolts, and connections between the material at low temperatures have not synchronized contraction and relaxation lead to leaks. So we put the valve body and pipeline connection to the flange welded structure, to avoid cold leak. The second is at the stem and packing leak. Most of the filler valve is generally used F4, because it is self-slip performance, low friction coefficient (the coefficient of friction of steel f = 0.05 ~ 0.1), but also has a unique chemical stability, so widely used. But there are shortcomings F4, one cold flow tendency large; second linear expansion coefficient, shrinkage at low temperatures have led to leakage, resulting in a large number of ice at the stem to open the valve failure. To this end a self-developed cold shrink sealing butterfly valve structure that use features F4 expansion coefficient, to the left through the gap to reach room temperature, low temperature can be the purpose of sealing.
原文来自：http://www.diefa.org

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译文：

译文：
低温阀门产生泄漏的原因主要有两种情况，一是内漏；二是外漏。 1)阀门产生内漏主要原因是密封副在低温状态下产生变形所致。当介质温度下降到使材料产生相变时造成体积变化，使原本研磨精度很高的密封面产生翘曲变形而造成低温密封不良。我们曾对DN250阀门进行低温试验，介质为液氮(-196℃)蝶板材料为1Cr18Ni9Ti(没经过低温处理)发现密封面翘曲变形量达0.12mm左右，这是造成内漏的主要原因。新研制的蝶阀由平面密封改为锥面密封。阀座是一个斜圆锥椭圆密封面，与嵌装在蝶板上的正圆形弹性密封环组成密封副。密封环可在蝶板槽内径向浮动。当阀门关闭时，弹性密封环首先和椭圆密封面的短轴接触，随着阀杆的转动逐渐将密封环向内推，迫使弹性环再和斜圆锥面的长轴接触，最终导致弹性密封环与椭圆密封面全部接触。它的密封是依靠弹性环产生变形而达到的。因此当阀体或蝶板在低温下产生变形时，都会被弹性密封环来吸收补偿，不会产生泄漏和卡死现象。当阀门打开时这一弹性变形立即消失，在启闭过程中基本没有相对磨擦，故使用寿命长。 2)阀门的外漏。其一是阀门与管路采用法兰连接方式时，由于连接垫料、连接螺栓、以及连接件在低温下材料之间收缩不同步产生松弛而导至泄漏。因此我们把阀体与管路的连接方式由法兰连接改为焊接结构，避免了低温泄漏。其二是阀杆与填料处的泄漏。一般多数阀门的填料采用F4，因为它的自滑性能好、摩擦系数小(对钢的摩擦系数f=0.05～0.1)，又具有独特的化学稳定性，因此得到广泛应用。但F4也有不足之处，一是冷流倾向大；二是线膨胀系数大，在低温下产生冷缩导致渗漏，造成阀杆处大量结冰，至使阀门开启失灵。为此研制的低温蝶阀采用自缩密封结构即利用F4膨胀系数大的特点，通过予留的间隙达到常温、低温都可以密封的目的。

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