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Sealing basics

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1.1 Leakage and leakage are one of the common problems of mechanical equipment. The reasons for the leakage are mainly two aspects: First, due to the results of mechanical processing; the appearance of mechanical products must have various defects and shapes and scale errors; The joints of the mechanical parts can not avoid the gaps, and the pressure difference between the two sides of the seal; the working medium will leak through the gap.
Reducing or eliminating voids is the primary way to prevent leakage. The effect of sealing is to seal the gap between the joints. Unloading the idle and forging ǖ 黾 黾 黾 孤 孤 孤 孤 孤 孤 孤 孤The shavings are made by the cockroaches, the cockroaches, the cockroaches, the cockroaches, the cockroaches, the cockroaches, the cockroaches.
Regarding the sealing of the vacuum system; in addition to the above leakage medium directly leaking through the sealing surface; also consider the following two ways of leakage:
Leakage: that is, under the effect of pressure difference; leakage of the sealed medium through the capillary of the seal data is called leakage.
Dispersion: that is, under the effect of concentration difference; the sealed medium passes through the sealed space or the capillary material of the sealed data is transferred to become scattered.
1.2 Sealed seals can be divided into two categories: static seals between the stop joints and dynamic seals between the joint joints. Static seals are primarily sealed; rubber seals and touch seals are based on three types of work. Static seal can be divided into medium and low pressure static seal and high pressure static seal. The medium and low pressure static seal is usually soft; the gasket is wider; the high pressure static seal is harder; the touch width is narrow. Dynamic seals can be divided into two types: rotary seals and reciprocating seals. Parts that move relative to the effect of the seal can be touched; can be divided into touch seals and non-touch seals. Generally speaking; seals for touch seals Good; but subject to conflicting wear; suitable for applications where the sealing surface speed is low. Non-touch seals have poor sealing; suitable for higher speed applications.
1.3. Seal selection The basic requirement for sealing is good sealing; safe and reliable; long service life; and tight layout; simple system; convenient production and repair; low cost. Most of the seals are wearing parts; Ensure interchangeability; complete standardization; serialization.
1.4 Sealing information
1.4.1 The type of sealing data and the sealing material of the application should be satisfactory for the sealing function. The sealed medium is different; and the working conditions of the equipment are different; the sealing information needs different habits. The requirements are usually:
1) The data is fine; it is not easy to leak the medium.
2) have proper mechanical strength and hardness,
3) Good tightening and resilience; eternal deformation.
4) does not soften at high temperature; does not differentiate; does not harden at low temperature; does not crack,
5) Good anti-corrosion function; can work in acid, alkali, oil and other media for a long time; its volume and hardness change.
6) Conflict coefficient. 湍バ院茫
7) has a softness in connection with the sealing surface,
8) Good aging resistance; durable,
9) Convenient processing and processing; cheap price; simple selection.
Rubber is the most commonly used sealing material. In addition to rubber; graphite and other materials suitable for sealing materials; polytetrafluoroethylene and various sealants.
1.4.2 General rubber seal products information General rubber seal products in the national defense; chemical; coal; petroleum; metallurgy; transportation and machinery manufacturing industries are more and more widely used; has become the basis of various occupations Parts and accessories.
Common information on rubber sealing products is as follows.
1.4.2.1 Nitrile rubber nitrile rubber has excellent resistance to fuel oil and aromatic solvents; but it is not resistant to ketones; esters and hydrogen chloride; therefore oil-resistant sealing products and nitrile rubber are the main choice.
1.4.2.2 Neoprene neoprene has outstanding oil and solvent resistance. It has good resistance to gear oil and transformer oil; but it is not resistant to aromatic oil. Neoprene also has excellent resistance. Weathering and ozone aging function. The cross-linking cracking temperature of neoprene is above 200 °C; the door and window seals are usually made of neoprene. The neoprene also has excellent corrosion resistance with respect to inorganic acids. In addition; due to neoprene Also has outstanding flexibility and non-breathability; can be made into diaphragm and vacuum sealing products.
1.4.2.3 Natural rubber natural rubber is comparable to most synthetic rubber; has outstanding inductive mechanical function; cold resistance; high resilience and wear resistance. Natural rubber is not resistant to mineral oil; but in vegetable oils and alcohols It is more stable. It is used as a rubber bowl for seals in the liquid restraint system of brake fluid composed of mixed liquid of n-butanol and refined castor oil; the rubber ring is made of natural rubber; usually the sealant is also made of natural rubber.
1.4.2.4 Fluororubber fluororubber has excellent heat resistance (200 ~ 250 ° C); oil resistance; can be used to make cylinder liner seals; rubber bowl and rotating lip seal; can significantly improve the application time.
1.4.2.5 Silicone rubber has excellent resistance to high and low temperature; ozone and weathering resistance; it can adhere to its unique application flexibility and ozone resistance in the operating temperature range of -70 to 260 °C; The same length; suitable for the production of seals required in thermal tissue; such as strong light source lamp cover gasket; valve pad, etc.. Because silicone rubber is not resistant to oil; low mechanical strength; expensive; therefore it is not suitable for oil-resistant sealing products.
1.4.2.6 The main chain of EPDM rubber is a completely full linear type without double bonds; it has a diene bismuth on its side chain; this can be vulcanized with sulfur. Ethylene propylene rubber has excellent aging resistance; ozone resistance; weather resistance; heat resistance (can be used for a long time in 120 ° C environment); chemical resistance (such as alcohol; acid; strong base; oxidant); Resistant to aliphatic and aromatic solvents. EPDM rubber has the lowest density and high filling properties in rubber; but lacks self-adhesiveness and mutual adhesion. In addition, EPDM rubber has excellent steam resistance; It can produce sealing products such as steam-resistant diaphragms. EPDM rubber has been widely used in washing machines; accessories and door and window sealing products in TV sets; or production of various composite profiles.
1.4.7.7 Polyurethane rubber polyurethane rubber has excellent grindability and outstanding gas impermeability; the operating temperature is usually -20 ~ 80 ° C. In addition; also has medium oil resistance; oxygen and resistance Ozone aging characteristics; but not resistant to acid and alkali, water, steam and ketones, etc. Suitable for making various rubber sealing products; such as oil seals, O-rings and barriers.
1.4.8.2.8 Chloroether rubber chloroether rubber combined with nitrile rubber; neoprene rubber; the strength of acrylate rubber; its oil resistance, heat resistance, ozone resistance, flame resistance, alkali resistance, water resistance and organic solvent resistance Very good; and has outstanding technical functions; its cold resistance is poor. In the case of low temperature application; chloroether rubber is still used to make oil seals; various seals; gaskets; seals such as barriers and dust covers Outstanding information.
1. 4. 2. Acrylate rubber Acrylate rubber has heat-resistant oil (mineral oil; smooth oil and fuel oil); especially oil stability at high temperature; usually up to 175 ° C; gap application or short time Temperature resistance 200 ° C. Its defect is poor cold resistance. Therefore, it is suitable to make oil seals for high temperature resistant oil in non-ice areas; but it is not suitable for sealing products subjected to tensile or compressive stress at high temperature.
2, pad seal sealing is widely used in pipelines; pressure vessels and static sealing of the contact faces of various shells. The gasket is sealed with non-metallic gaskets; non-metal and metal combination gaskets and metal gaskets. Commonly used materials are rubber; leather; asbestos; cork; PTFE; steel; iron; copper and stainless steel.
There are three ways to leak the gasket seal: interface leakage; soaking leakage and destructive leakage. In the past, both were the primary methods.
3.1 Overview The function of the sealing data is to fill the gaps in the configuration and the construction of the helium gas; to seal the effect. There are three types of sealing materials:
1) Vulcanized rubber gasket or seal ring,
2) Non-vulcanized sealing tape,
3) Paste or putty-like liquid sealant without fixed shape.
3.2 Classification of sealant There are many types and types of sealant. In order to satisfy the same application requirements, it is possible to use several different sealants of the base material, and the same base material can produce different functions and different uses. Sealant. Think from both the creator and the user of the sealant; there are many ways to classify the sealant. It can usually be classified according to the following four methods.
3.2.2 Classification by sealant base
3.1.2.1 Rubber type This type of sealant is based on rubber. Commonly used rubber is polysulfide rubber; silicone rubber; polyurethane rubber; neoprene and butyl rubber.
3.2.2. 2 Resin type This type of sealant is based on resin. Commonly used resins are epoxy resin, unsaturated polyester resin, phenolic resin, polyacrylic resin, polyvinyl chloride resin, etc.
3.2.3.3 Oil-based type of such sealant is based on oil. Commonly used oils are various vegetable oils such as linseed oil; castor oil and tung oil; and animal oils (such as fish oil).
3.2.2 According to the sealant vulcanization method, this series of sealants is vulcanized with moisture in the air. It mainly contains one-component polyurethane, silicone rubber and polysulfide rubber. Its polymer base is rich in activity. Gene; can react with the water in the air; constitute cross-linking; vulcanize the sealant into a mesh layout. The moisture in the atmosphere acts as a catalyst in the reaction of vulcanization.
3.2.2.2 Chemical vulcanized sealant Two-component polyurethane, silicone rubber, polysulfide rubber, neoprene and epoxy resin sealant are all classified in this category; usually vulcanized at room temperature. One-component chlorosulfonated polyethylene and neoprene sealant and polyvinyl chloride sol paste sealant (such as automotive spot weld adhesive); must be vulcanized by chemical reaction under additional conditions.
3.2.2.3 Thermally modified sealant Plasticizers Polyvinyl chloride resin and asphalt-filled rubber are used in two different types of thermal conversion systems. Vinyl resin plasticizers It is a liquid suspension at room temperature; it is hardened by heating to solids, while the rubber asphalt is hot-melt with a sealant.
3.2.2.4 Oxidation-hardened sealant The surface of the boring caulking or equipment glass sealant belongs to this type; it is mainly based on dry and semi-dry vegetable oil. The medium-sized oil can be refined and polymerized. , blown or chemically modified. Cobalt naphthenate is used as a drier to accelerate the appearance of boring and internal hardening. Lead naphthenate can harden both the exterior and the interior, while manganese naphthenate makes internal hardening more useful.
3.2.2.5 Solvent transpiration coagulation sealant This is a sealant based on non-viscous polymer after solvent transpiration. This type of sealant mainly has butyl intersection, high molecular weight polyisobutylene, and a certain degree of polymerization. 2. Acrylate, chlorosulfonated polyethylene and sealant such as neoprene.
3.2.2.6 Insufficient use of permanent plastic sealant such sealant usually contains polybutene, medium molecular weight polyisobutylene, high viscosity non-oxidizing adhesive such as styrene based oil, non-drying Vegetable oil, blown semi-dry oil or butyl rubber based sealant.
3.3.2 Classification by sealant shape
3.2.3.1 Paste sealant This type of sealant is a low-grade sealant; three main materials are usually selected: oil and resin, polybutene, asphalt. Fixed glass used to seal small windows; seams The maximum amount of displacement is +5% or -5%; the useful period is usually 2 years.
3.2.3.2 Liquid Elastomer Sealant This type of sealant contains a liquid polymer that is vulcanized to form an elastic condition. They have the ability to accept repeated joint deformation. The liquid elastomer sealant has a service life of usually 15-20. This type of sealant has high adhesion and shear strength; it has excellent softness at room temperature. Its defects are high in price; usually it requires primer; two-component sealant is not convenient for on-site mixing; Sensitive to temperature and humidity.
3.2.3. 3 hot melt sealant hot melt sealant is also known as hot construction sealant; it refers to the sealant with elastomer and thermoplastic resin blend as the base material.
Hot melt sealant can be formulated successfully close to liquid elastomeric sealant; however, it is superior to liquid elastomer sealant in that it does not require participation in the vulcanizing agent.
3.3.2.3 Liquid sealant This type of sealant is primarily used for the sealing of mechanical contact surfaces; it replaces solid seal information (paper, asbestos, cork and vulcanized rubber); to avoid mechanical internal fluid leakage from the interface; Liquid sealant is also known as liquid gasket.
3.2.4 According to the classification of utility after construction of sealant
3.2.4.1. Curing sealant This kind of sealant can be divided into two types: rigid and flexible. The rigid sealant is solidified after vulcanization or condensation; it has little elasticity, and the flexible sealant has elasticity after vulcanization. Softness.
The characteristics of rigid sealant are not tortuous; usually the seam does not move.
The flexible sealant adheres to the softness after vulcanization.
3.2.4.2 Non-curing sealant This kind of sealant is a soft-condensing sealant; it still adheres to the dryness after the construction (the tackifier continuously migrates to the outside). This glue is usually a paste. Shape; can be applied to the seam with a scraper or brush; can be used with different seals and different functions.
3. 3 kinds of commonly used sealant in the classification of the front sealant listed in a variety of ways; the most widely used is the sealant is divided into two types of vulcanized and non-vulcanized type. The most used in vulcanized sealant Widely used room temperature vulcanization type; less temperature vulcanization type. Non-vulcanized sealant has liquid sealant and putty. In addition; in addition to the commonly used anaerobic adhesive.
3.4 Selection of liquid sealant and construction process Sealant selection; should be based on the application conditions, the information of the seal and the condition of the sealing surface, the variety and characteristics of the sealing medium and the coating process, etc. The force is large; and when subjected to impact force and alternating force; the sealant with higher strength should be selected, when the temperature difference is large; the sealant with good tolerance should be selected.
3.4.1 Construction method of liquid sealant The construction method of liquid sealant can be selected according to the condition of the glue. The paste seal can be applied by scraper or injection gun, and the brush seal or spray coating of liquid sealant is used. The sealant is applied by the paving method.
3. 5 domestic sealant
3.5.1 Room temperature vulcanized polysulfide rubber sealant is multi-component data; room temperature vulcanized into elastomer; dry adhesive sealant; commonly used XM series sealant.
3.5.2 Room temperature vulcanized silicone rubber sealant Silicone rubber sealant has a variety of special functions; such as high temperature resistance, low temperature resistance; outstanding electrical insulation function.
3.5.3 anaerobic adhesive
3.5.4 Other vulcanized sealants
3. 5 non-vulcanized sealant Non-vulcanized sealant is mostly non-dry and semi-dry; in the case of putty, also known as non-vulcanized putty. This kind of glue is sensitive to temperature. Indeed, 诿芊饨 诿芊饨 槐湫 槐湫 槐湫 徊豢 徊 徊 徊 て诖 て诖 て诖 て诖 て诖 て诖 嫘 嫘 嫘 嫘 嫘 嫘 嫘 嫘 嫘 嫘 嫘 ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ ρ 艿 艿 艿 艿 艿芊饧疤疃 蟮 蟮 蟮 峁 峁 峁 峁 叮 叮 叮 叮 谝 谝 谝 谝 迕芊獾嬷 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳 糜诳
4, packing seal packing seal is one of the oldest sealing methods; has been in China for thousands of years ago. It was first filled with cotton and hemp fibers in the leakage channel to hinder the flow leakage; the first is used as a water lifting machine Seal.
The packing seal is mainly used as a dynamic seal. It is widely used as a shaft seal for centrifugal pumps, compactors, vacuum pumps, mixers and ship propellers; reciprocating compactors, reciprocating shaft seals for refrigerators; and swirling of various valve stems Sealing, etc. In order to get used to the working conditions of the above equipment; packing seals must have the following conditions:
1) It has a certain plasticity; under the effect of pressing force, it can attack a certain radial force and be tightly touched with the shaft.
2) Satisfactory chemical stability; no pollution of the medium; the filler is not swollen by the medium; the injecting agent in the guessing is not dissolved by the medium; the packing itself does not corrode the sealing surface.
3) Outstanding from smooth function; wear resistance; small conflict factor.
4) When there is a small amount of pain in the shaft; the filler should have satisfactory buoyancy.
5) Simple production; easy to fill.
There are many kinds of fillers; they can be classified from their functions, layout and materials; the most commonly used are the following four types: stranded fillers, braided fillers, plastic fillers, metal fillers.
4.1 Stranded packing and braided packing stranded packing is to twist several strands of asbestos wire together; it can be sealed in the packing cavity to seal the effect.
2. The braided packing is made of cotton, hemp and asbestos fibers after being spun and infiltrated with a smoothing agent or Teflon.
4. 2 Plastic filler Plastic filler is a filler that has been formed by several films.
4.3 Metal fillers Metal fillers are available in semi-metal fillers and all-metal fillers. The so-called semi-metal fillers are a combination of metal and non-metal; all metal fillers contain no non-metal.
4. 4 carbon fiber filler Carbon fiber filler is a new type of filler. Its excellent self-smoothing function, high temperature resistance, low temperature function and chemical resistance have attracted great attention; and the elasticity and softness of the compact packing are also outstanding. The defect is only that there is soaking and leaking; but it can be avoided after invading Teflon or other adhesives. The current cost is higher; but with the development of carbon fiber; its cost will be reduced; thus; carbon fiber filler is a kind The most ambitious and most desirable filler.`
4. 5 Selection of fillers When selecting fillers; should consider: the type of machine, the physical and chemical properties of the medium, the operating temperature and operating pressure; and the speed of movement; etc.; especially the corrosiveness of the medium (indicated by pH); pH Value and operating temperature are the most important.
4.6 Reasonable filling of fillers The rational filling of fillers shall be carried out as follows:
1) Finish the packing cavity; check whether the shaft surface has scratches, burrs and other appearances.
2) Use the dial indicator to check the radial runout of the shaft at the sealing part; its public service should be within the agreed scale.
3) The packing chamber and the shaft surface should be coated with a sealant or a sealant that the medium is accustomed to.
4) For the packing of the roll package; firstly take a rod with the same diameter as the shaft diameter; wrap the packing around it; then cut it with a knife; cut the best 450 slope; cut each block after the block Should not let it loose; should not straighten it; instead, take a tape with the same width as the filler to wrap each piece of packing in a circle; put it in a clean place.
5) Filling should be done once in a circle when filling; do not fill a few rings together.
6) Take a wooden two-sleeve sleeve of the same size as the packing; fit on the shaft; push the packing into the deep part of the cavity; and apply a certain pressure to the wooden bushing with the gland;
7) Fill the second and third rings in the same way.
8) After the final filling of the filling, the gland is pressed; but the pressing force should not be too large.
5. Forming packing Sealing packing packing refers to the annular sealing ring formed by molding or turning with rubber, plastic, leather and metal materials.
According to the working characteristics, the molding packing is divided into two types: kneading type sealing ring and lip sealing ring. According to the data, it can be divided into rubber, plastic, leather and metal. Kneading of rubber kneading in various sealing materials. Type seals are the most widely used; the O-rings are the longest in history; most typical. There are many types of lip seals; there are V-shaped, U-shaped, L-shaped, J-shaped and Y-shaped.
5.1 O-ring seal
The O-ring is referred to as the O-ring; the beginning appears in the middle of the 19th century; it is used as the sealing element of the steam engine cylinder.
O-ring rubber seals have the following advantages:
1) The layout of the sealing part is simple; the equipment part is compact; the weight is lighter.
2) Self-sealing effect; often only one seal can be used to complete the seal.
3) The sealing function is better; when used as a static seal, it can be done without leakage.
4) The resistance to sports conflict is very good.
5) Standards and grooves have been standardized; low cost; easy to use and outsourced.
5.2 V-ring seal
V-ring is a kind of lip seal; it is one of the earliest used molding fillers. It is mainly used for reciprocating motion; it is used as a piston or piston rod seal. It is rarely used for transformation or static sealing.
V-rings have the following features:
1) Excellent sealing function,
2) Promising for the painful load and the painful movement,
3) It can be stacked in multiple turns; and the pressing force is adjusted to achieve the maximum sealing effect.
4) Impact pressure and oscillating pressure,
5) When the packing can not be loaded from the axial direction; it can be opened and cut off; only the equipment will be cut off from each other; the sealing effect is not affected. The defect is that the conflict resistance is larger than other forming fillers.
5.3 Y-ring seal U-shaped and Y-shaped seals for piston seals are slightly different in shape; lip length of U-ring; bottom or lip thickness or slightly larger than lip thickness. Y-ring Pure short; thick at the bottom; this is designed to defeat the U-ring and often cannot be placed safely; together it can increase the strength of the lip; avoid tearing the root of the lip.
5.4 layout of drum and mountain seals
5.4. The layout of the drum seal is also known as the piston seal; it is depicted for the unidirectional and bidirectional piston. The cross section of the seal, the layout of the bushing or retaining ring and the piston The depiction has a lot to do. Because of the various functional needs; so the layout of the drum seals can not be common.
5. 5 J-shaped and L-shaped seals
J-shaped and L-shaped sealing rings; all used for the sealing of pneumatic or hydraulic mechanical equipment with a working pressure of not more than 1 MPa.
The J-ring seal is used for piston rod sealing.
6.1 Oil seal oil seal; that is, smooth oil seal. It is often used in various mechanical bearings; especially for rolling bearing parts. Its function is to block the oil chamber from the outside; seal the oil inside; seal the outside.
Oil seals have the following advantages over other seals:
1) The oil seal is light in weight; less consumables.
2) The equipment orientation of the oil seal. 嵯虺叽缧.菀准庸.
3) The sealing function is good; the service life is long; it has certain habits for the oscillation of the machine and the partial pain of the main shaft.
4) Disassembly and abbreviation; easy maintenance.
5) The price is cheap.
6.2 Dust seal oil seal can be used as a dust seal. However, when the dust is severe or to protect other seals, a special dust seal is often used.
Dust-proof and sealed materials; oil-pressure mechanical multi-purpose rubber; pneumatic machinery multi-purpose felt; aircraft and cold-carrying cylinders use metal to resist the external ice on the piston rod; some chemicals use metal to avoid sticking on the piston rod.
Dust seals are important for securing critical hydraulic equipment. Entering dust; not only wearing seals; but also greatly abrading the guide sleeves and piston rods. In addition; impurities entering the hydraulic medium; also affecting the operation of valves and pumps In the worst case; can also damage these equipment. Dust ring can remove the dust and debris on the outer surface of the piston rod; but damage the oil film on the piston rod; this also has a certain effect on the smoothness of the seal.
7.1 magnetic fluid
7.1.1 Composition of magnetic fluid
Magnetic fluid created by Papell in the United States in 1995; it is a kind of fine powder (about 100 Å) such as magnetite that is stable in water, oil, esters, ethers, etc. Colloidal liquid. This liquid has the characteristics of normal centrifugal force and magnetic field; it does not settle and agglomerate and can accept itself magnetic; it can be attracted by magnets.
The magnetic fluid consists of three primary components:
1) solid ferromagnetic particles (Fe3O4),
2) an external active agent (stabilizer) which coats the particles and hinders them from agglutinating each other,
3) Carrier liquid (solvent).
7.1.2 Characteristics of magnetic fluid Magnetic fluid is a kind of colloidal solution. It is used as a magnetic fluid for sealing. Its functional requirements are: good stability; no agglomeration, no deposition, no differentiation, high saturation magnetization, starting magnetic The conductivity is large, the viscosity and the full vapor are low; other factors such as condensation point, boiling point, thermal conductivity, specific heat and surface tension are also inevitable.
The primary factors affecting the stability of magnetic fluids are: particle size, surface active agent and carrier liquid, and their reasonable ratio. Stability is the condition for the existence of various properties of magnetic fluid.
7.2 The working principle of magnetic fluid seal is a circular ring permanent magnet; the magnetic circuit formed by the pole piece and the rotating shaft; under the effect of the magnetic field of the magnet; the magnetic fluid placed between the shaft and the tip of the pole piece is gathered; It is made into a so-called "O" ring; the intention of blocking the gap channel to reach the seal. This sealing method can be used in the case where the rotating shaft is a magnetic body and a rotating shaft is in the wrong magnetic body. The former is collected in the gap. And the magnetic circuit is formed through the rotating shaft; the latter magnetic flux ratio does not pass through the rotating shaft; only the magnetic fluid in the sealed gap constitutes a magnetic circuit.
7.2.3 Limit conditions Magnetic fluid seals are subject to the following conditions during operation:
1) transpiration. The magnetic fluid is composed of magnetic particles, external active agent and carrier liquid 3; transpiration of carrier liquid is the primary factor in determining the ultimate rotational frequency and service life of the seal. Since the seal is operated by a limited magnetic fluid. The carrier liquid with a low vapor pressure should be selected; the transpiration loss is the minimum.
2) Temperature rise. Temperature rise will cause magnet demagnetization and magnetic fluid transpiration. Due to temperature increase; viscosity reduction; power consumption will also decrease; this is a favorable side. However, temperature rises; magnetic saturation strength decreases; It is also possible to reduce the withstand voltage of the seal; therefore; the temperature of the magnetic fluid should generally not be higher than 105 ° C; otherwise, the cooling method should be selected.
3) Ultimate vacuum degree. The ultimate vacuum degree of magnetic fluid seal depends on the transpiration of the carrier liquid; the carrier liquid prepared with the diester smoothing agent can satisfy the demand of 1.333×10-7Pa ultra-high vacuum technology.
4) Weekly speed. Usually magnetic fluid seal is suitable for operation with high peripheral speed above 30m/s; no limit mark. But think about temperature and heat dissipation; the peripheral speed should be constrained to 60~80m/s; at this moment, the ultimate withstand voltage should be considered. Talent.
8. There are many types of high-pressure sealed high-pressure seals; according to their operating principles, they are divided into two types: forced seal and self-tight seal. Forced seal is based on the pre-tightening force of the coupling (bolt) to ensure the top cover, sealing element and circle of the pressure vessel. There is a certain touch pressure between the ends of the barrel; in order to reach the seal. The self-seal is added with the operating pressure in the pressure vessel; the contact pressure between the sealing element and the top cover and the end of the cylinder is also followed. Adding; thus completing the sealing effect. The characteristic of self-seal is the higher the pressure; the pressing force of the sealing element on the touch surface is greater; the sealing function is better; when the operating conditions are shaken; the seal is still firm. However, the layout is relatively simple. Miscellaneous; production is difficult. Self-tight sealing according to the deformation of the sealing element can also be divided into axial self-tight sealing and radial self-tight sealing.
According to the function of sealing data; the high-pressure seal can be divided into plastic seals that cause plastic deformation of the sealing elements; elastic seals that make the sealing elements elastically deform.
Currently; the commonly used sealing types for pressure vessels are as follows:
1) The forced seal has a flat gasket seal; the kazari seal and the octagonal gasket seal,
2) Semi-self-tight sealing with double cone seal,
3) Self-tight sealing with wedge seal; Wude seal; hollow metal O-ring seal; C-ring seal; B-ring seal; triangular gasket seal; octagonal gasket seal; flat gasket self-tightening and rubber O-ring seal, etc. .

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