译文：
强制密封的必要条件，是在介质感恩戴德和操作力作用下，密封面上仍能保持一定的残侠压紧力。应强调指出的是：强制密封中，介质压力总是趋向于减小预紧密封比压降低密封性能。 　　强制密封的典型结构是平垫密封、缠绕垫密封和齿形垫密封等。通常用于低压、中压和中小口径的阀门。 　　(2)阀门的自紧密封 　　升压前，先旋紧螺栓，使阀盖上升，使阀盖与楔形密封垫之间，以及阀体与楔形密封垫之间形成初始密封条件－－密封面上的预紧比压。当介质压力上升时，阀盖受介质压力作用，向上移动，阀盖与楔形密封垫，以及阀体与楔形密封垫之间的密封比压，随压力的增加而逐渐增大。在自紧密封中，密封面上的工作密封比压由两部分合成：一是预紧密封比压，二是由介质压力形成的比压。应强调指出：自紧密封中，介质压力总是趋于增加预紧密封比压，增加密封性能。介质压力愈高，工作密封比压就愈大，密封性能愈了。根据这一特点，自紧密封作为高压密封技术，常用于高温、高压大口径调节阀。 　　自紧密封中根据介质压力作用在密封垫上的力的方向，又可分为轴向自紧密封和径向自紧密封。 　　轴向自紧密封有楔形垫级合密封(伍德密封)、楔形密封、平垫自紧密封、C形圈密封及O形圈密封。 　　径向自紧密封有双锥密封、B形环密封、三角垫密封、八角环(椭圆环)密封及透镜垫密封。

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原文：
The necessary conditions for a mandatory seal is grateful and operation of power in the medium under the effect of sealing the surface can still maintain a certain residual Xia clamping force. Should be emphasized that: forced sealed, the media always tends to reduce the preload pressure sealed lower than the pressure sealing performance. The typical structure of a mandatory seal is flat pad sealing, Spiral Wound Gasket seals and toothed pad seals. Commonly used in low, medium and small-caliber valve. (2) Self-tight sealing valve Step-up before tighten bolts, valve cover to make up, so that with the wedge-shaped valve cover gasket, and between the body and the wedge-shaped gasket seal formed between the initial conditions - sealed surface of the preload than pressure. When the medium pressure rise, the valve cover by the medium pressure, upward mobility, valve cover gasket and wedge-shaped, and the valve body with the wedge-shaped gasket seal between the specific pressure, with pressure increasing gradually increasing. In self-tight seal, the sealing surface of the work of sealing pressure than the synthesis consists of two parts: First, seal preload than pressure, and second, the pressure created by the media than the pressure. It should be emphasized that: Since the tight seal, the media always tends to increase the preload pressure than the pressure seal to increase the sealing performance. Medium pressure higher than the pressure the greater the work of sealing and sealing performance, the more of. According to this characteristic, since the tightly sealed as a high-pressure seal technology, commonly used in high temperature, high pressure large-diameter valve. Since the tightly sealed, in accordance with medium pressure in a sealed pad direction of the force, can be divided into axial and radial self-sealing self-close tightly sealed. Since the close of axial seal with wedge-shaped cushion-level co-Seal (Wood sealed), wedge-shaped seal, flat pad from the sealed tightly, C-ring seal and O-ring seal. Since there are biconical radial seal tightly sealed, B-ring seal, triangular cushion seal, octagonal ring (oval ring) seal and lens pad seal.