{"id":792,"date":"2026-04-30T08:59:52","date_gmt":"2026-04-30T08:59:52","guid":{"rendered":"https:\/\/spartaseal.com\/?p=792"},"modified":"2026-04-30T09:24:30","modified_gmt":"2026-04-30T09:24:30","slug":"comprehensive-sealing-knowledge-complete-classification-working-principle","status":"publish","type":"post","link":"https:\/\/spartaseal.com\/zh\/comprehensive-sealing-knowledge-complete-classification-working-principle\/","title":{"rendered":"Comprehensive Sealing Knowledge \u2013 Complete Classification & Working Principle"},"content":{"rendered":"

Seals are divided into two main categories: static seals<\/strong> for relatively stationary joint surfaces, and dynamic seals<\/strong> for relatively moving joint surfaces.<\/p>\n\n\n\n

1. Static Seal<\/h2>\n\n\n\n

A static seal refers to sealing between two stationary surfaces.<\/p>\n\n\n\n

It is mainly classified into three types:<\/p>\n\n\n\n

    \n
  • Gasket seal<\/li>\n\n\n\n
  • Sealant seal<\/li>\n\n\n\n
  • Direct contact seal<\/li>\n<\/ul>\n\n\n\n

    2. Dynamic Seal<\/h2>\n\n\n\n

    A dynamic seal is used for sealing between relatively moving parts of machinery and equipment.<\/p>\n\n\n\n

    2.1 Packing Seal<\/h3>\n\n\n\n

    Packing seals are widely used for dynamic sealing of moving parts in mechanical process equipment, such as centrifugal pumps, compressors, vacuum pumps, mixers and reaction vessels.<\/p>\n\n\n\n

    They are also applied to plunger and rod sealing of reciprocating pumps and reciprocating compressors, as well as stem sealing of valves with linear or spiral motion.<\/p>\n\n\n\n

    Main Types of Packing<\/h4>\n\n\n\n

    1) Asbestos Packing<\/strong><\/p>\n\n\n\n

    It features excellent high temperature resistance and corrosion resistance. However, the sealing effect is poor when used alone, so it is usually impregnated or compounded with other materials.<\/p>\n\n\n\n

    Oil-impregnated asbestos packing has two structures: twisted type and braided type, available in round and square shapes.<\/p>\n\n\n\n

    2) PTFE Braided Packing<\/strong><\/p>\n\n\n\n

    Woven with PTFE thin tapes, it offers outstanding corrosion resistance and can be used for cryogenic media.<\/p>\n\n\n\n

    3) Rubber O-Ring<\/strong><\/p>\n\n\n\n

    It performs well under low pressure, but its working temperature is limited. For example, natural rubber O-rings are only suitable for temperatures below 60\u2103.<\/p>\n\n\n\n

    4) Molded Plastic Packing<\/strong><\/p>\n\n\n\n

    Mostly designed as three-piece structure or custom shapes. The main material is PTFE; Nylon 66 and Nylon 1010 are also commonly used.<\/p>\n\n\n\n

    5) Soft Packing Seal<\/strong><\/p>\n\n\n\n

    Also known as mud packing, soft packing is made of high-performance synthetic fibers with special barrier agents and lubricants.<\/p>\n\n\n\n

    It fits any size and shape and can be installed easily by direct injection with a special high-pressure gun, without pre-cutting like traditional packing. It is suitable for stuffing boxes of all sizes.<\/p>\n\n\n\n

    Application<\/strong>: High-pressure reciprocating pumps, low-speed pumps, high-temperature valve stems and general stuffing box sealing.<\/p>\n\n\n\n

    Advantages<\/strong>: Simple structure, stable operation and low cost, widely used in general working conditions.<\/p>\n\n\n\n

    2.2 Expander Ring Seal<\/h3>\n\n\n\n

    The expander ring is a split metal elastic ring, also known as a piston ring.<\/p>\n\n\n\n

    In free state, the ring opening is spread; after installed into the cylinder, the opening closes tightly. The outer circle closely fits the cylinder inner wall by elastic force.<\/p>\n\n\n\n

    During operation, medium pressure pushes the ring against one side of the groove. Sealing is achieved by the outer cylindrical surface and the end face of the ring.<\/p>\n\n\n\n

    Common materials: cast iron and tin bronze.<\/p>\n\n\n\n

    Typical applications: piston sealing of high-temperature reciprocating compressors and internal combustion engines, as well as shaft sealing of steam turbines.<\/p>\n\n\n\n

    2.3 Contact Type Dynamic Seal<\/h3>\n\n\n\n

    Gasket Seal<\/h4>\n\n\n\n

    Sealing gaskets are essential spare parts for machinery, equipment and pipelines with fluid media.<\/p>\n\n\n\n

    Made of metal or non-metal sheet materials by cutting, stamping and trimming, they are used for sealed connection between pipelines and mechanical components.<\/p>\n\n\n\n

      \n
    • Metal gaskets<\/strong>: Copper, stainless steel, iron, aluminum, etc.<\/li>\n\n\n\n
    • Non-metal gaskets<\/strong>: Asbestos, non-asbestos, paper, rubber, graphite and other new-type gaskets.<\/li>\n<\/ul>\n\n\n\n

      Thread Seal<\/h4>\n\n\n\n

      Two common forms:<\/p>\n\n\n\n

        \n
      1. Threaded joint with gasket seal<\/li>\n\n\n\n
      2. Threaded connection with filler seal<\/li>\n<\/ol>\n\n\n\n

        Both are used for small-diameter threaded connections.<\/p>\n\n\n\n

        In threaded gasket sealing, the gasket undertakes the sealing function, while the thread only provides compression force.<\/p>\n\n\n\n

        Sealing performance depends on gasket material, sealing surface roughness and geometric precision of threaded holes.<\/p>\n\n\n\n

        Non-metallic gaskets bear both pressure and torque during tightening, easy to deform, and are only suitable for low pressure.<\/p>\n\n\n\n

        Metal gaskets can withstand pressure above 30MPa.<\/p>\n\n\n\n

        Felt Ring Seal<\/h4>\n\n\n\n

        The wool felt ring is installed in the trapezoidal groove of the bearing cover. It is pressed tightly against the shaft by the groove side to achieve sealing.<\/p>\n\n\n\n

        It has good flexibility, heat preservation, moisture retention and elasticity.<\/p>\n\n\n\n

        Welt oil seals are commonly used in gear reducers. A trapezoidal groove is designed at the bearing end cover of input and output shafts to install the felt ring, preventing dust ingress and lubricant leakage.<\/p>\n\n\n\n

        Oil Seal<\/h4>\n\n\n\n

        Oil seals are used for lubricant sealing, isolating lubricated transmission parts from external parts to prevent oil leakage.<\/p>\n\n\n\n

        All rotating equipment with internal lubricant and external connection positions need oil seals.<\/p>\n\n\n\n

        Most are steel-reinforced rubber oil seals, plus pure rubber and metal types.<\/p>\n\n\n\n

        Typical applications: crankshaft oil seal, gearbox oil seal, half shaft oil seal, final drive oil seal, air compressor crankshaft oil seal, etc.<\/p>\n\n\n\n

        Fully Enclosed Seal<\/h4>\n\n\n\n

        It completely isolates internal and external leakage channels, or integrates the prime mover and working equipment into one sealed system to eliminate medium leakage.<\/p>\n\n\n\n

        It is indispensable for production involving highly toxic, radioactive and rare valuable media, as well as precision laboratories.<\/p>\n\n\n\n

        Diaphragm seal is a typical form.<\/p>\n\n\n\n

        2.4 Non-Contact Type Dynamic Seal<\/h3>\n\n\n\n

        Floating Ring Seal<\/h4>\n\n\n\n

        Also called oil film seal, it is a high-speed sealing structure for gas and liquid.<\/p>\n\n\n\n

        For gas sealing, the chamber is filled with lubricating oil for sealing and lubrication.<\/p>\n\n\n\n

        Sealing is realized by the tiny gap between the floating metal ring and the shaft or housing.<\/p>\n\n\n\n

        The floating ring can move freely in the housing, less affected by high-speed rotation and vibration, with low friction and wear.<\/p>\n\n\n\n

        Screw Seal<\/h4>\n\n\n\n

        A type of dynamic seal with spiral grooves processed on the rotating shaft or sleeve. Sealing medium is filled between shaft and sleeve.<\/p>\n\n\n\n

        The rotating shaft drives the spiral groove to produce a pumping effect to block liquid leakage.<\/p>\n\n\n\n

        Sealing capacity is affected by spiral angle, pitch, tooth width, tooth height, sealing length and clearance between shaft and sleeve.<\/p>\n\n\n\n

        No direct friction ensures long service life. Limited by structural space, spiral length is short, so sealing capacity is restricted. The sealing effect will drop obviously under low speed operation.<\/p>\n\n\n\n

        Centrifugal Seal<\/h4>\n\n\n\n

        It uses centrifugal force generated by rotating components to prevent medium leakage.<\/p>\n\n\n\n

        Main types: back vane seal<\/strong> and auxiliary impeller seal<\/strong>, widely used in centrifugal pumps.<\/p>\n\n\n\n

        They allow larger sealing clearance, low wear, long service life and nearly zero leakage.<\/p>\n\n\n\n

        Suitable for slurry pumps and impurity pumps conveying solid-containing media.<\/p>\n\n\n\n

        Disadvantages: high power consumption and additional shutdown seal required.<\/p>\n\n\n\n

        Dry Gas Seal<\/h4>\n\n\n\n

        A new type of shaft end seal using grooved technology for gas sealing.<\/p>\n\n\n\n

        When the grooved rotating ring runs, hydrodynamic grooves pump high-pressure isolation gas into the seal end face gap.<\/p>\n\n\n\n

        Gas film pressure changes gradually from outer diameter to inner diameter, forming a thin stable gas film to keep the seal in non-contact state.<\/p>\n\n\n\n

        The gas film blocks the leakage channel and realizes zero emission<\/strong>.<\/p>\n\n\n\n

        Advantages<\/strong>:<\/p>\n\n\n\n

          \n
        • Low leakage, environmentally friendly<\/li>\n\n\n\n
        • Low wear and long service life<\/li>\n\n\n\n
        • Low power consumption, only about 5% of traditional mechanical seals<\/li>\n\n\n\n
        • No oil contamination to sealed medium<\/li>\n\n\n\n
        • Simple auxiliary system and maintenance-free<\/li>\n<\/ul>\n\n\n\n

          Labyrinth Seal<\/h4>\n\n\n\n

          Multiple annular sealing teeth are arranged around the rotating shaft, forming a series of throttling gaps and expansion cavities.<\/p>\n\n\n\n

          Medium is throttled when passing through the tortuous labyrinth channel to reduce leakage.<\/p>\n\n\n\n

          Advantages<\/strong>: Good high-speed performance, no lubrication needed, no friction, easy maintenance, long service life.<\/p>\n\n\n\n

          Disadvantages<\/strong>: High machining precision required and difficult assembly.<\/p>\n\n\n\n

          Magnetic Fluid Seal<\/h4>\n\n\n\n

          Magnetic fluid is filled into the magnetic field gap to form a liquid O-ring.<\/p>\n\n\n\n

          It can transmit rotational motion into sealed containers and is widely used for vacuum sealing.<\/p>\n\n\n\n

          2.5 End Face Seal (Mechanical Seal)<\/h3>\n\n\n\n

          End face seal relies on compression fit between perpendicular end faces.<\/p>\n\n\n\n

          A mechanical seal consists of at least one pair of end faces perpendicular to the rotating shaft.<\/p>\n\n\n\n

          Under fluid pressure, elastic compensation force and auxiliary seal cooperation, the end faces keep close contact and relative sliding to prevent leakage.<\/p>\n\n\n\n

            \n
          • Metal bellows mechanical seal: uses metal bellows for elastic loading and auxiliary sealing.<\/li>\n\n\n\n
          • Rubber bellows mechanical seal: used for light-duty working conditions, usually matched with springs for enough compression force.Mechanical seal is generally abbreviated as Mechanical Seal<\/strong>.<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"

            Seals are divided into two main categories: static seals for relatively stationary joint surfaces, and dynamic seals for relatively moving joint surfaces. 1. Static Seal A static seal refers to sealing between two stationary surfaces. It is mainly classified into three types: 2. Dynamic Seal A dynamic seal is used for sealing between relatively moving […]<\/p>\n","protected":false},"author":1,"featured_media":796,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"none","_seopress_titles_title":"Comprehensive Sealing Knowledge: Static Seal & Dynamic Seal Complete Guide","_seopress_titles_desc":"Complete sealing classification and working principle introduction, including static seal, packing seal, mechanical seal, dry gas seal, labyrinth seal and all common sealing types for mechanical equipment.","_seopress_robots_index":"","footnotes":""},"categories":[27],"tags":[],"class_list":["post-792","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-seals-knowledge"],"_links":{"self":[{"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/posts\/792","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/comments?post=792"}],"version-history":[{"count":1,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/posts\/792\/revisions"}],"predecessor-version":[{"id":795,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/posts\/792\/revisions\/795"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/media\/796"}],"wp:attachment":[{"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/media?parent=792"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/categories?post=792"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spartaseal.com\/zh\/wp-json\/wp\/v2\/tags?post=792"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}