在工業管道與流體輸送系統中，閥門如同控制水流、氣流的 “守門人”，而密封結構則是其實現嚴密阻隔的核心 “武器”。從日常生活中的水管閥門到工業領域的高壓閥門，不同類型的密封結構通過精妙設計，將流體牢牢 “鎖” 在管道內，其背后的原理充滿智慧與巧思。

　　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、強制密封：以力制勝的 “物理防御”

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

　　強制密封是最常見的密封方式，它依靠外力擠壓密封面，消除間隙實現阻隔。常見于閘閥、截止閥中，當閥門關閉時，閥瓣在閥桿的驅動下，朝著閥座方向移動并施加壓力。例如，閘閥的楔形閘板與閥座緊密貼合，通過螺紋傳動或電動裝置加大擠壓力度，使密封面間的接觸應力超過流體壓力，從而阻止介質泄漏。這種密封的關鍵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，密封材料的選擇也至關重要，橡膠、聚四氟乙烯等軟質材料具有良好的彈性變形能力，能填充微小縫隙；而金屬密封面則依靠硬度與韌性，在高壓環境下保持結構穩定。

　　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：借勢發力的 “智能屏障”

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

　　自密封結構巧妙利用介質自身壓力增強密封效果，壓力越大，密封越緊。典型代表是一些高壓閥門中的 “錐形密封” 與 “O 型圈自密封”。以錐形密封為例，當閥門關閉時，介質壓力作用在閥瓣上，將其進一步壓緊在錐形閥座內，壓力越高，接觸面上的比壓越大，密封性能越強。O 型圈自密封則通過將橡膠 O 型圈安裝在凹槽中，介質壓力會使 O 型圈向壓力側變形，緊貼密封面，形成嚴密的密封。這種結構無需額外施加過大外力，尤其適用于高溫、高壓工況，減少了密封部件的磨損，延長了閥門使用壽命。

　　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：多重防護的 “柔性防線”

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

　　在閥門的閥桿處，為防止介質沿閥桿與閥體的間隙泄漏，常采用填料密封。它由填料函、填料、壓蓋等部件組成。填料一般為浸油石棉繩、柔性石墨等具有彈性和耐腐蝕性的材料，被填充在填料函內。當擰緊壓蓋上的螺栓時，壓蓋向下擠壓填料，使其產生徑向膨脹，填滿閥桿與填料函之間的空隙，形成密封。隨著使用時間增長，填料會因磨損而泄漏，此時可通過再次擰緊壓蓋螺栓補充密封力。一些高級填料密封還會設計多層填料結構，每層填料各司其職，如內層防泄漏、外層防雜質侵入，進一步提升密封性能。

　　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、動力密封：主動出擊的 “動態防御”

　　4、 Power seal: a proactive "dynamic defense"

　　在部分特殊工況下，如高溫、高粘度介質輸送，會采用動力密封。這種結構通過機械運動產生與泄漏方向相反的壓力，抵消介質的泄漏趨勢。例如，螺旋密封在閥桿上加工出螺旋槽，當閥桿旋轉時，螺旋槽推動介質向閥門內部流動，與介質的泄漏方向相反，從而達到密封效果。另一種常見的動力密封是流體動壓密封，利用密封面間的微小間隙，通過高速旋轉產生流體動壓力，形成一層穩定的液膜或氣膜，既起到密封作用，又能潤滑密封面，減少摩擦與磨損。

　　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、組合密封：取長補短的 “終極方案”

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

　　為應對復雜嚴苛的工況，現代閥門常采用組合密封結構，將多種密封方式結合使用。例如，在高壓燃氣閥門中，閥瓣與閥座采用金屬硬密封保證耐壓性，同時輔以軟質密封材料增強密封效果；閥桿處則采用填料密封與機械密封相結合的方式，填料密封負責初步阻擋介質，機械密封進一步提升密封精度，防止微量泄漏。這種組合模式充分發揮不同密封結構的優勢，有效應對高溫、高壓、腐蝕等多種挑戰，確保閥門在極端環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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