Packing is also called sealing packing, the conventional packing is made of softer threads, and the cross-sectional area is usually a triangle, square or rectangular, circular strip filled in the sealing cavity. Packing seal was first used to plug cotton and linen fibers in the leakage channel to prevent the leakage of liquid flow, mainly used as the shaft seal of water lifting machinery. Due to the wide range of filler sources, easy processing, low price, reliable sealing, simple operation, so used so far. Today, the disc is widely used in centrifugal pump, compressor, vacuum pump, mixer and ship propeller shaft seal, piston pump, reciprocating compressor, refrigerator reciprocating shaft seal, as well as a variety of valve stem rotary seal.
Working principle
The surface of the shaft is very uneven in the microscopic case, and it can only partially fit with the disc. So there’s a tiny gap between the disc and the shaft, like a maze. The medium is intercepted several times in the maze, thus achieving a sealing effect.
The packing seal consists of packing in the packing box and pressing the packing on the surface of the shaft through the packing gland. Because the surface of the shaft is always somewhat rough, it can only partially fit with the filler, and the part is not in contact, which forms countless labyrinths. When the pressurized medium passes through the shaft surface, the medium is throttled several times, and the seal is achieved by this “maze effect”. The bonding and friction of the packing and the shaft surface are also similar to plain bearings, which should be lubricated with enough liquid to ensure that the seal has a certain life, that is, the so-called “bearing effect”. It can be seen that a good packing seal is a synthesis of the maze effect and the bearing effect.
The compression force of the packing on the shaft is generated by tightening the gland bolt. Because the packing is an elastic-plastic body, when the axial compression, resulting in friction, the compression force along the axial gradually reduced, while the generated radial compression force makes the packing close to the surface of the shaft to prevent the leakage of the medium. The distribution of radial compression force is from the outer end (gland) to the inner end, which decreases sharply at first and then flattens gradually. The distribution of medium pressure gradually decreases from the inner end to the outer end. When the outer medium pressure is zero, the leakage is very little, and when the leakage is greater than zero.
With the continuous emergence of new materials, the structure of the filler has also changed greatly, which will undoubtedly promote the application of the filler seal more widely, the material used as the filler should have the following characteristics: there is a certain elastic-plastic. When the packing is axially pressed, it can produce a large radial pressing force to obtain a seal. When the machine and the shaft have vibration or the shaft has runout and eccentricity, it can have a certain compensation ability (followability); Chemical stability. Neither be corroded by the medium, dissolve, nor pollute the medium; Impermeability. The medium has some penetration of most fibers, so the packing tissue is required to be dense, so it is often necessary to impregnate and fill various lubricants and fillers when making the packing. Good self-lubrication, small friction coefficient and wear resistance; Temperature resistance. When friction heating can withstand a certain temperature; Easy to disassemble; Simple manufacturing, low price.
Application
As a static seal, widely used in containers, heaters, manholes, caps, etc., can also be used for heat insulation and fire prevention in pipelines, suitable for neutral media, can be used for water, steam, air, oil and other services.
High resilience, soft and wear-resistant high-performance novel synthetic fiber packing, better than the commonly used yellow aramid and white aramid, generally golden yellow, commonly known as “gold aramid “. It can also be customized in orange or blue as required. The disc also makes up for many deficiencies of the PTFE disc. Thermal stability, low thermal expansion, dimensional stability under alternating temperature and pressure; High strength, but not grinding shaft, easy to cut; Excellent resistance to chemical media, especially acids, organic solvents, oils and fuels. Application: High performance multi-purpose pump, valve universal packing, widely used in various industrial fields, especially for those with graphite composition is not suitable for food, paper industry medium need to clean and easy to wear media.
sort
1, aramid series
Gold aramid fiber packing, yellow aramid fiber packing, aramid fiber interwoven white tetrafluoroethylene packing, aramid fiber interwoven black tetrafluoroethylene packing This series of packing is made of aramid fiber as the main material, many times impregnated lubricant, tetrafluoroethylene emulsion and so on. It has good high rebound, chemical resistance, low cold flow, high wire speed, compared with other types of packing, it can resist particle crystallization medium and higher temperature. It can be used alone or combined with other packing. It is mainly used in the condition of many medium particles and easy wear.
2, self-pressing die strip series
This type of packing is a non-woven type and is usually used as a replacement for conventional packing after wear or placed between conventional packing and shaft to reduce wear. Its shape is usually triangular or square, according to the specific working conditions can be pinched into a variety of shapes, the type of disc can be installed whole or cut into several sections. This type of packing has an operating temperature range of 0° to >400°F (>204°C) and a rated operating pressure of 10,000 psi. This type of disc is not affected by acid, oil, corrosives and conventional solvents, and can be used on shaft surfaces with shaft rotation speeds up to 1000 fpm. The representative products of this type of packing are 636G and 686 patented formulations of LIQUILON, OCRI Company.
3, semi-liquid series
Semi-fluid packing is a solid particle film packing product that can be plated onto metal surfaces and provides the lowest coefficient of friction of all materials. The semi-fluid type packing provides excellent sealing and lubrication properties and can repair scratched, dented or damaged shafts for recovery. The semi-fluid type is specifically designed for use with tight tolerances up to 0.02 “clearance requirements and is resistant to temperatures up to 400°F (204°C) and pressures up to 10,000 psi. The semi-fluid type packing is compatible with stuffing boxes of any size and lubricates conventional packing, eliminating overwear and requiring no shaft replacement. The representative products of this type of packing are OCRI LIQUILON patented formula 506 and 507.
4, tetrafluoroseries
White tetrafluoroethylene packing, black tetrafluoroethylene packing, white tetrafluoroethylene interwoven aramid fiber packing, black tetrafluoroethylene interwoven aramid fiber packing, tetrafluoroethylene preoxidized wire packing, white tetrafluoroethylene packing. It has excellent chemical stability, corrosion resistance, sealing, high lubrication non-stickiness and good aging resistance. It can work at the temperature of +250℃ to -180℃ for a long time, in addition to molten metal sodium and liquid fluorine, it can withstand all other chemicals, and it does not change when boiling in aqua aureus. It is mainly used in the working environment that does not allow pollution, such as sanitary grade, strong corrosion and other requirements, high line speed, easy wear and other working conditions.
5, graphite series
Flexible graphite packing, metal reinforced graphite packing, carbon fiber reinforced graphite packing, carbon fiber metal reinforced graphite packing This series of packing features are made of graphite as the main material. It has the advantages of good self-lubrication and thermal conductivity, small friction coefficient, strong versatility, good softness, high strength, and protective effect on the shaft. According to different requirements, carbon fiber, copper wire, 304, 316L, incaustic nickel alloy wire and other materials can be used to strengthen. Mainly used in high temperature and high pressure conditions.
6, carbon fiber series
Carbon fiber reinforced graphite coil, carbon fiber metal reinforced graphite coil This series of coil is mainly carbon fiber as the theme material, carbon fiber is a new material with excellent mechanical properties, carbon fiber no creep, good fatigue resistance, small thermal expansion coefficient, good corrosion resistance, good thermal conductivity. Mainly used in high temperature and high pressure wear conditions.
7, with rubber core series
It is made of super elastic silicone core coated with high quality synthetic fiber and braided by multiple impregnation of PTFE emulsion, lubricant and barrier agent. It can effectively absorb mechanical vibration and control the leakage of cracks caused by vibration. It has excellent resilience, self-lubrication, flexibility, wear resistance, high tensile strength, good chemical resistance and so on.
8, high temperature ultra-high temperature packing
The packing is made of high quality synthetic fiber (1250), with fine structure, excellent high temperature and high pressure resistance, low thermal conductivity, non-combustion and other advantages. Widely used in ultra-high temperature, high pressure and harsh environment of water, steam, acid, alkali and other media. It is used for heat insulation and fire prevention of pipelines, static sealing of containers, heaters, manholes, heaters at the door of the furnace, high temperature flanges, etc. Steel mill high temperature promotion use, blast furnace combustion valve special.
In addition to the above materials, there are acrylic packing, high water base packing, hemp packing, etc., to meet the needs of different working conditions. (2023-10-25)
