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Packers, also known as sealing fillers, are usually made by weaving together softer fibrous materials; they are inserted into the sealing chamber in the form of strips with a square cross-section to achieve sealing. Packing seals were initially developed by using fibers such as cotton and linen to block leakage pathways and prevent fluid leakage, mainly serving as shaft seals for water lifting machinery. It has been in use to this day due to its wide availability of fillers, ease of processing, low cost, reliable sealing, and simple operation. Today, packing is widely used for shaft sealing in centrifugal pumps, compressors, vacuum pumps, mixers, and ship propellers; for reciprocating shaft sealing in piston pumps, reciprocating compressors, and refrigerators; as well as for rotary sealing of valve stems in various valves. Structure and principle of packing seal: The common packing seal structure is shown in Figure 1-1(a). In a packing seal, the packing 2 is placed inside the packing box 1, and the packing is compressed against the surface of the shaft by the packing gland 3. Since the surface of the shaft is always somewhat rough, it can only make partial contact with the packing, leaving parts that are not in contact; this creates countless labyrinthine structures. When the pressurized medium passes through the surface of the shaft, it is throttled multiple times, achieving sealing through this \"labyrinth effect\". The fit and friction between the filler and the shaft surface are similar to those in sliding bearings; therefore, sufficient liquid is needed for lubrication in order to ensure that the seal has a certain service life, which is what is referred to as the \"bearing effect\". It can be seen that a good packing seal is a combination of the labyrinth effect and the bearing effect. The compressive force of the filler on the shaft is generated by tightening the gland bolts. Since the packing is an elastoplastic material, when subjected to axial compression, friction is generated, causing the compressive force to decrease gradually along the axis. At the same time, the resulting radial compressive force presses the packing tightly against the shaft surface, preventing the medium from leaking out. The distribution of the radial compressive force is shown in Figure 1-1(b); it decreases rapidly from the outer end (the gland) toward the inner end, before becoming more gradual. The distribution of the medium pressure is shown in Figure 1-1(c), with it decreasing gradually from the inner end toward the outer end. When the medium pressure at the outer end is zero, leakage is minimal; whereas when it is greater than zero, leakage is significant. http://www.aigindustries.com.cn/cptp/image002.jpg http://www.aigindustries.com.cn/cptp/image004.jpg http://www.aigindustries.com.cn/cptp/image006.jpg Common packing sealing materials: With the continuous emergence of new materials, there have been significant changes in the design of packing structures, which will undoubtedly lead to a wider use of packing seals. Materials used as packings should possess the following properties: ● A certain degree of elastoplasticity. When the packing is compressed axially, a greater radial compressive force is generated to achieve sealing ； It has a certain compensating ability (following capability) when the machine and the shaft experience vibration, or when the shaft has runout or eccentricity ； ●Chemical stability. It is neither corroded nor swelled by the medium, nor does it contaminate the medium ； ●Impermeability. The medium penetrates to some extent into most fibers; therefore, a dense structure of the filler is required. For this reason, various lubricants and fillers are often used in the process of manufacturing the filler ； ●Good self-lubricating properties, low friction coefficient, and wear resistance ； ●Temperature resistance. It can withstand a certain temperature when heat is generated due to friction ； ●Easy to disassemble ； ●Easy to manufacture and inexpensive. Common packing materials are classified into the following categories: ● Asbestos types such as graphite-coated asbestos packing, tetrafluoroethylene-impregnated asbestos packing, and asbestos-rubber packing; due to their poor environmental performance, they have been gradually phased out. ●Fiber-based types: PTFE-impregnated ramie packing, high-water-content packing, oil-impregnated cotton yarn packing, PTFE-impregnated fiber packing, graphite-impregnated fiber packing, GFO fiber packing, etc. ● PTFE-based types: Graphite-lubricated PTFE packing, white PTFE packing, oil-containing white PTFE packing, expanded PTFE packing, silicone-core packing, etc. ● Aramid-based types: Aramid fiber packing, aramid fiber PTFE packing, oil-impregnated aramid fiber packing, etc. ● Carbon fiber-based types: Pre-oxygenated carbon fiber packing, carbon fiber packing, nickel wire-reinforced carbon fiber packing, graphite-lubricated carbon fiber packing, etc. ● Graphite-based types: Flexible graphite packing, PTFE-reinforced graphite packing, metal-reinforced graphite packing, carbon fiber-reinforced graphite packing, etc. ● Ceramic fiber-based types: Ceramic fiber packing. Common additives used: http://www.aigindustries.com.cn/cptp/image008.jpg http://www.aigindustries.com.cn/cptp/image010.jpg http://www.aigindustries.com.cn/cptp/image012.jpg http://www.aigindustries.com.cn/cptp/image014.jpg http://www.aigindustries.com.cn/cptp/image016.jpg http://www.aigindustries.com.cn/cptp/image018.jpg http://www.aigindustries.com.cn/cptp/image020.jpg