在工业管道与流体输送系统中，阀门如同控制水流、气流的 “守门人”，而密封结构则是其实现严密阻隔的核心 “武器”。从日常生活中的水管阀门到工业领域的高压阀门，不同类型的密封结构通过精妙设计，将流体牢牢 “锁” 在管道内，其背后的原理充满智慧与巧思。

　　In industrial pipelines and fluid transportation systems, valves are like "gatekeepers" that control water and air flow, and sealing structures are the core "weapons" that achieve tight barriers. From water pipe valves in daily life to high-pressure valves in the industrial field, different types of sealing structures are ingeniously designed to firmly "lock" fluids inside pipelines, and the principles behind them are full of wisdom and ingenuity.

　　一、强制密封：以力制胜的 “物理防御”

　　1、 Forced sealing: a "physical defense" that wins with force

　　强制密封是最常见的密封方式，它依靠外力挤压密封面，消除间隙实现阻隔。常见于闸阀、截止阀中，当阀门关闭时，阀瓣在阀杆的驱动下，朝着阀座方向移动并施加压力。例如，闸阀的楔形闸板与阀座紧密贴合，通过螺纹传动或电动装置加大挤压力度，使密封面间的接触应力超过流体压力，从而阻止介质泄漏。这种密封的关键在于密封面的加工精度，表面越光滑、平整度越高，所需的密封力越小，密封效果也越好。此外，密封材料的选择也至关重要，橡胶、聚四氟乙烯等软质材料具有良好的弹性变形能力，能填充微小缝隙；而金属密封面则依靠硬度与韧性，在高压环境下保持结构稳定。

　　Forced sealing is the most common sealing method, which relies on external force to squeeze the sealing surface and eliminate gaps to achieve obstruction. Commonly found in gate valves and globe valves, when the valve is closed, the valve disc is driven by the valve stem to move towards the valve seat and apply pressure. For example, the wedge-shaped gate of a gate valve is tightly fitted to the valve seat, and the squeezing force is increased through threaded transmission or electric device, so that the contact stress between the sealing surfaces exceeds the fluid pressure, thereby preventing medium leakage. The key to this type of sealing lies in the machining accuracy of the sealing surface. The smoother and flatter the surface, the lower the required sealing force, and the better the sealing effect. In addition, the selection of sealing materials is also crucial. Soft materials such as rubber and polytetrafluoroethylene have good elastic deformation ability and can fill small gaps; The metal sealing surface relies on hardness and toughness to maintain structural stability in high-pressure environments.

　　二、自密封：借势发力的 “智能屏障”

　　2、 Self sealing: an "intelligent barrier" that leverages power

　　自密封结构巧妙利用介质自身压力增强密封效果，压力越大，密封越紧。典型代表是一些高压阀门中的 “锥形密封” 与 “O 型圈自密封”。以锥形密封为例，当阀门关闭时，介质压力作用在阀瓣上，将其进一步压紧在锥形阀座内，压力越高，接触面上的比压越大，密封性能越强。O 型圈自密封则通过将橡胶 O 型圈安装在凹槽中，介质压力会使 O 型圈向压力侧变形，紧贴密封面，形成严密的密封。这种结构无需额外施加过大外力，尤其适用于高温、高压工况，减少了密封部件的磨损，延长了阀门使用寿命。

　　The self sealing structure cleverly utilizes the pressure of the medium itself to enhance the sealing effect. The higher the pressure, the tighter the seal. Typical representatives are the "conical seal" and "O-ring self sealing" in some high-pressure valves. Taking conical sealing as an example, when the valve is closed, the medium pressure acts on the valve disc, further compressing it inside the conical valve seat. The higher the pressure, the greater the specific pressure on the contact surface, and the stronger the sealing performance. O-ring self sealing is achieved by installing a rubber O-ring in a groove. The medium pressure will cause the O-ring to deform towards the pressure side, tightly adhering to the sealing surface, forming a tight seal. This structure does not require excessive external force, especially suitable for high temperature and high pressure conditions, reducing the wear of sealing components and extending the service life of the valve.

　　三、填料密封：多重防护的 “柔性防线”

　　3、 Packing sealing: a "flexible defense line" with multiple protections

　　在阀门的阀杆处，为防止介质沿阀杆与阀体的间隙泄漏，常采用填料密封。它由填料函、填料、压盖等部件组成。填料一般为浸油石棉绳、柔性石墨等具有弹性和耐腐蚀性的材料，被填充在填料函内。当拧紧压盖上的螺栓时，压盖向下挤压填料，使其产生径向膨胀，填满阀杆与填料函之间的空隙，形成密封。随着使用时间增长，填料会因磨损而泄漏，此时可通过再次拧紧压盖螺栓补充密封力。一些高级填料密封还会设计多层填料结构，每层填料各司其职，如内层防泄漏、外层防杂质侵入，进一步提升密封性能。

　　At the valve stem, packing sealing is often used to prevent medium leakage along the gap between the valve stem and the valve body. It consists of components such as stuffing box, packing, and gland. The filling material is generally made of elastic and corrosion-resistant materials such as oil impregnated asbestos rope and flexible graphite, which are filled in the filling box. When tightening the bolts on the gland, the gland compresses the packing downwards, causing it to expand radially and fill the gap between the valve stem and the packing box, forming a seal. As the usage time increases, the packing will leak due to wear and tear. At this time, the sealing force can be supplemented by tightening the gland bolts again. Some advanced packing seals are also designed with multi-layer packing structures, where each layer of packing plays its own role, such as preventing leakage in the inner layer and preventing impurities from entering the outer layer, further enhancing the sealing performance.

　　四、动力密封：主动出击的 “动态防御”

　　4、 Power seal: a proactive "dynamic defense"

　　在部分特殊工况下，如高温、高粘度介质输送，会采用动力密封。这种结构通过机械运动产生与泄漏方向相反的压力，抵消介质的泄漏趋势。例如，螺旋密封在阀杆上加工出螺旋槽，当阀杆旋转时，螺旋槽推动介质向阀门内部流动，与介质的泄漏方向相反，从而达到密封效果。另一种常见的动力密封是流体动压密封，利用密封面间的微小间隙，通过高速旋转产生流体动压力，形成一层稳定的液膜或气膜，既起到密封作用，又能润滑密封面，减少摩擦与磨损。

　　In some special working conditions, such as high temperature and high viscosity medium transportation, power seals will be used. This structure generates pressure opposite to the direction of leakage through mechanical motion, offsetting the leakage tendency of the medium. For example, a spiral seal is machined with a spiral groove on the valve stem. When the valve stem rotates, the spiral groove pushes the medium to flow towards the inside of the valve, opposite to the direction of medium leakage, thus achieving a sealing effect. Another common type of dynamic seal is the fluid dynamic pressure seal, which utilizes the small gaps between the sealing surfaces to generate fluid dynamic pressure through high-speed rotation, forming a stable liquid or gas film that not only seals but also lubricates the sealing surface, reducing friction and wear.

　　五、组合密封：取长补短的 “终极方案”

　　5、 Combination sealing: the ultimate solution to complement each other's strengths and weaknesses

　　为应对复杂严苛的工况，现代阀门常采用组合密封结构，将多种密封方式结合使用。例如，在高压燃气阀门中，阀瓣与阀座采用金属硬密封保证耐压性，同时辅以软质密封材料增强密封效果；阀杆处则采用填料密封与机械密封相结合的方式，填料密封负责初步阻挡介质，机械密封进一步提升密封精度，防止微量泄漏。这种组合模式充分发挥不同密封结构的优势，有效应对高温、高压、腐蚀等多种挑战，确保阀门在极端环境下仍能保持可靠的密封性能。

　　To cope with complex and harsh working conditions, modern valves often adopt a combination sealing structure, combining multiple sealing methods. For example, in high-pressure gas valves, the valve disc and seat are sealed with metal hard seals to ensure pressure resistance, while soft sealing materials are used to enhance the sealing effect; The valve stem adopts a combination of packing seal and mechanical seal. The packing seal is responsible for initially blocking the medium, while the mechanical seal further improves the sealing accuracy and prevents trace leakage. This combination mode fully leverages the advantages of different sealing structures, effectively addressing various challenges such as high temperature, high pressure, and corrosion, ensuring that the valve can maintain reliable sealing performance even in extreme environments.

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