Gaskets and sealing materials. Sealing materials Types of gasket materials used in pumping units
Electrical materials. For powering electrical equipment used in plumbing work ah, use different power cables.
Flexible power cables for voltage up to 220 V according to GOST 6731-77E are manufactured in the following grades: RGD - with rubber-insulated copper conductors; RGDO - with copper conductors with a rubber sheath; RGDV - with a main residential and insulated auxiliary conductors with a common rubber insulation having protective properties. Cables are used to connect electrode holders of automatic or semi-automatic devices with a source of rated AC voltage up to 220 V, frequency 50 Hz or DC voltage. The cables are designed to operate at temperatures environment from -50 to +50 °С. The construction length of the cables is at least 100 m.
Flexible power cables for a voltage of 660 V according to GOST 13497-77E are produced in the following grades: KRPT - with copper conductors with rubber insulation in a rubber sheath; KRPTN - with copper conductors with rubber insulation in a rubber sheath, in a rubber oil-resistant sheath that does not propagate combustion; CRPG - with copper conductors of increased flexibility with rubber insulation in a rubber sheath; KRPGN - with copper conductors increased flexibility with rubber insulation in a rubber oil-resistant sheath that does not spread combustion; KRPS - with copper conductors of increased flexibility with rubber insulation with a profiled core in a rubber sheath.
Cables are supplied in coils weighing no more than 50 kg or wound on wooden drums.
Rubber products. Flat rubberized fabric drive belts used in electric generators and electric pumps are made of three types depending on the purpose and design:
- type A - threaded, used for small pulleys at rotation speeds of more than 20 m / s; are made in width 20; 25; thirty; 40; 45; fifty; 60; 70; 75; 80; 85; 90; 100; 125; 150 mm;
- type B - wrapped in layers, used when working with a discontinuous load at rotation speeds up to 20 m / s; are made 20 wide; 25; thirty; 40; 150; 200; 250 mm;
- type B - spiral wrapped, used when working with small loads at rotation speeds up to 15 m / s; from-are prepared with a width of 20; 25; thirty; 40; fifty; 60; 75; 80; 85; 90; 100; 125; 150 mm.
Belts up to 90 mm wide are produced at least 8 m long; 100 mm wide or more - at least 20 m long.
The surface of the belts must be smooth, without exposing fabric pads, without knots, protruding threads and delaminations, without cracks, dents and blisters, pits, scars and mechanical damage.
V-belts in accordance with GOST 1284.1-80 consist of cord fabric or cord, wrapping fabric and rubber, connected into one whole by vulcanization.
The inner length of the belt corresponds to the length of its inner circumference, and the calculated length corresponds to the circumference at the level of the calculated belt width, measured under tension. Preferred calculated belt lengths are: 400; 450; 500; 560; 630; 710; 800; 900; 1000;1120;1250; 1400;1600; 1800; 2000; 2240; 2500; 2800; 3150; 3550; 4000; 4500; 5000; 5600; 6300; 7100; 8000; 9000; 10,000; 11 200; 12,500; 14,000; 16,000 and 18,000 mm.
In operation, the belts must remain operational in the temperature range from -30 to +60 °C.
Rubber pressure hoses with a textile frame (according to GOST 18698-79) are used as flexible pipelines for supplying liquids, gases and bulk materials under pressure. Depending on the purpose and working conditions, these hoses are manufactured in the following types: B - for supplying gasoline, kerosene, oil and mineral oils; B - for supplying water and weak solutions inorganic acids and alkalis with a concentration of up to 20%; VG - for filing hot water temperature up to 100 °С; G - for supplying air, oxygen, acetylene, carbon dioxide, nitrogen and other inert gases; P - for the supply of food substances; Ш - for supplying solutions at plastering works; Steam-1 and Steam-2 - for the supply of saturated steam.
Rubber-fabric pressure hoses with inner (nominal) diameter 10; 12.5; sixteen; 20; 25; 31.5; 40; 50 and 63 mm are manufactured for working pressure up to 2.0 MPa (20 kgf / cm 2); diameter 80; 100; 125; 160 and 200 mm - for working pressure up to 0.5 MPa (5 kgf / cm 2).
Hose of all types must be airtight when tested with hydraulic pressure equal to twice the working pressure, and type D hoses - when tested with air pressure equal to the working pressure. Sleeves of types B, V, P and Sh must have at least a threefold margin of safety, and sleeves of types VG, G, Par-1 and Par-2 - at least five times.
Sleeves of all types must remain operational in the temperature range from -35 to +50 °C.
Rubber sleeves for gas welding and cutting of metals (according to GOST 9356-75) are used for supplying acetylene under pressure, liquid fuel and oxygen to equipment for welding and cutting metals at ambient temperatures from -35 to +70 °С and from -55 to +70 °С in regions with a cold climate (table below).
Depending on the purpose, the sleeves are made in three types with a distinctive color of the outer rubber layer:
- type I - for supplying acetylene, domestic gas, propane and butane under pressure not more than 0.63 MPa - red;
- type II - for supplying liquid fuels (gasoline, kerosene, white spirit) under a pressure of not more than 0.63 MPa - yellow;
- type III - for supplying oxygen under a pressure of not more than 2.0 MPa - blue.
Sleeves must have at least three times the tensile strength hydraulic pressure. On the outer surface of the sleeves there should be no bubbles, delaminations, dents and other defects; inner surface must be even, without folds, bubbles, etc.
Basic parameters of rubber sleeves
Pressure fire hoses (according to GOST 472-75) made of dry-spun linen yarn, depending on defects, are divided into the first and second grades.
Sleeves roll up into circles. At the outer end of each batch of circles put a brand, which indicates: 1) the name and address of the manufacturer; 2) inner diameter, mm; 3) name of the hose group; 4) sleeve length in a circle, m; 5) the mass of the circle and its number; 6) date of manufacture of ru-kava (year, month); 7) designation of each standard.
Stuffing, sealing and lining materials. For the production of plumbing work, the industry produces a number of auxiliary materials needed to seal the joints.
Stuffing box packings (according to GOST 5152-77) are used for sealing glands in fittings, pumps, machines and equipment and are designed for a wide range of pressures and temperatures. Packings impregnated with an anti-friction compound promise lubrication of rotating shafts and rods passing through the stuffing box.
Asbestos cords (according to GOST 1779-72) impregnated with an anti-friction compound or graphite mixed with natural drying oil are used for stuffing fittings, compensators, sealing sections of cast-iron boilers, threaded connections, and also as an insulating material.
Asbestos cardboard (according to GOST 2850-75) grades KAON-1 and KAON-2 is used as a heat-insulating and fire-retardant material at an insulated surface temperature of not more than 500 ° C, as well as a gasket material for equipment, instruments and communications. Cardboard brand KAP serves as a cushioning material. Cardboard sheets should not have cracks, dents, foreign mechanical inclusions.
Gasketboard (according to GOST 9347-74) is produced in sheets and rolls with a density of 0.7-0.75 g / cm 3 of two grades - A (impregnated) with a thickness of 0.3; 0.5; 0.8; one; 1.5 mm; B (unimpregnated) - 0.3 thick; 0.5; 0.8,; one; 1.25; 1.5; 1.75; 2; 2.25; 2.5 mm. Gaskets are made from cushioning cardboard for sealing flange joints of pipelines transporting water with a temperature of up to 100 ° C. Before installing the laying, it is necessary to moisten it in water and boil it in natural drying oil. The surface of the cardboard must be even, without warping, wrinkles, wrinkles, bubbles, non-fibrous inclusions and pressure spots.
Rubber and rubber-fabric plates (according to GOST 7338-77), used for the manufacture of gaskets, valve seals, shock absorbers and other parts, are produced acid-alkali-resistant, heat-resistant, frost-resistant and oil-and-petrol-resistant. The length of sheets or strips of plates is 0.5-10 m, width 200-1750 mm, thickness 0.5-50 mm. Heat-resistant rubber plates remain operable when operating in an air environment with a temperature of up to 90 ° C and in a water vapor environment with a temperature of up to 140 ° C. Frost-resistant rubber plates remain operable under operating conditions at temperatures up to -45 ° C. Rubber plates of all types remain heat-resistant when operated within temperatures from -30 to +50 ° C. A sheet rubber plate is used for the manufacture of flange gaskets for pipelines cold water. The rubber-fabric plate is used at water temperatures up to 100 °C.
Paronite (according to GOST 481-71) is made from a mixture of asbestos fibers, solvent, rubber and fillers and is produced in the form of sheets with a thickness of 0.4; 0.6; 0.8; 1.5; 2; 3; 4; 5 and 6 mm, sizes 300x400, 400x500, 500x500, 750x1000, 100x x1500, 1500x1500 and 3000x1500 mm. Gaskets are made from general-purpose paronite for flanged connections of hot water and steam pipelines with temperatures above 100 ° C. Before installation, the gaskets are moistened in hot water and lubricated with graphite mixed with natural drying oil. Paronite cannot be stored together (in the same room) with organic solvents, lubricating oils, acids and other substances that destroy it.
Sheet fiber (according to GOST 14613-69) is produced in eight grades. For example, fiber grade FP K (oxygen-resistant gasket) is made with a thickness of 0.6 to 5 mm, used as gaskets for neutral gaseous media (oxygen, carbon dioxide, etc.) at high pressures and normal temperatures; fiber must be thoroughly degreased before use. Fiber brand FT (technical) is used as a sealant in valves and taps of hot water supply systems.
Flax torn (according to GOST 10330-76) in the form of a strand impregnated with minium or white lead diluted on natural drying oil is used as a sealant in threaded joints of pipelines transporting water with a temperature of up to 105 ° C.
FUM - fluoroplastic sealing materials in the form of a tape 10-25 mm wide and 0.08-0.12 mm thick and a cord (for flange gaskets). The tape is used to seal threaded connections pipelines D y< 65 мм, шнур — для Уплотнения контргаек, а также в качестве сальниковой набив-ки вентилей и кранов. Уплотнение из ФУМ водостойко и вы-держивает температуру от -60 до +200 °С.
A resin strand (kabolka) is a bast fiber treated with wood resin - a waste from the production of hemp and flax fibers. A strand of two grades is produced: the first grade is made from hemp fiber, the second grade is made from a mixture of hemp and flax fibers. The strand is used to seal the sockets of cast-iron and ceramic pipes.
Hemp rope (according to GOST 483-75), impregnated with resin (to protect against decay) or without impregnation, is used to seal the sockets of cast-iron and ceramic pipes.
Auxiliary materials. Drying oil natural linen and hemp (according to GOST 7931-76) is used for the preparation of minium putty, dilution of primers and thickly ground paints, as well as for impregnation of cardboard gaskets. Drying oil should be stored in a tightly closed container.
Drying oil oksol (according to GOST 190-78) in some cases can serve as a substitute for natural drying oil. Produced by sealing linseed oil and blowing it with air in the presence of a desiccant, followed by the addition of a solvent (white spirit).
Minium lead (according to GOST 19151-73) is a heavy powder of bright red-orange color, five grades are produced: M-1, M-2, M-3, M-4 and M-5. Minium, diluted on natural drying oil (2 parts by weight of red lead and 1 part by weight of drying oil), is impregnated with a flax strand used as a sealant in threaded joints of heating pipelines with a coolant temperature of up to 105 ° C, pipelines hot water supply and gas supply.
White lead white (according to GOST 12287-77) in the form of a paste from a mixture of lead white, heavy spar and drying oil or raw linen or sunflower oil They produce three grades: MA-011, MA-011-N-1 and MA-OI-N-2. They serve the same purposes as red lead.
Zinc white thickly ground (according to GOST 482-77) is a paste of dry zinc white (or a mixture of them with a filler), rubbed on natural linseed drying oil or on vegetable oils with the addition of a desiccant, and seven grades are produced: MM-00 special, M-00, M-0, V-2-00, V-2-0, V-4-00, V-4-0. These whites, after diluting them with natural glyptal or pentaphthalic drying oil to a painting consistency, are used for painting surfaces. For internal works dilution of white drying oil with oxol is allowed.
Zinc white, diluted natural drying oil, serve to impregnate a linen strand used as a sealant in threaded joints of cold water pipelines.
Crucible graphite (according to GOST 4596-75) is used as an integral part of gland packings and mastics when connecting pipes, assembling cast-iron sectional boilers, impregnating paronite gaskets, etc.
Application of rubber products.
Types of rubber.
General information about rubber.
Topic 24. Rubber and gasket materials
Questions:
1. Rubber call the products of chemical processing of rubber and vulcanizing substances (sulfur, sodium), carried out with the help of heat treatment(hot vulcanization) or without it (cold vulcanization).
The main properties of rubber: elasticity, vibration resistance, increased chemical resistance, gas and water resistance, electrical insulation.
Rubber compounds are based on rubber, the mass content of which in various products ranges from 5 to 95% of the mixture also contain softeners, fillers, vulcanizing agents, antioxidants, dyes.
Raw materials for rubber products. Rubber is natural and synthetic. natural rubber obtained from the milky sap of rubber plants. Synthetic rubber - substance with properties close to natural. It is obtained by synthesis organic matter. industrial views synthetic rubber, of which there are several dozen, are distinguished from each other both in terms of feedstock and production methods, and in composition and physical and mechanical properties. The production of synthetic rubber consists of two main processes: the production of rubber compounds (butadiene, styrene, chloroprene, acrylonitrile, isobutylene, etc.) and their polymerization into a rubber-like product. The raw materials for the production of rubbers are petroleum products, natural gas, acetylene, wood, etc. During polymerization, rubber cogens from low molecular weight substances are converted into high molecular weight compounds with physical, mechanical and technological properties typical of natural rubber. The production of synthetic rubber was developed for the first time in the world by the Russian chemist S. V. Lebedev.
Synthetic rubbers (SR) are divided into two main groups: SR general purpose used in the manufacture of products with the most characteristic property of rubber - elasticity (mass production of tires, conveyor belts, shock absorbers, seals, shoes, toys, etc.) and SC special purpose, which, along with elasticity, must have specific properties. Butadiene and butadiene-styrene rubbers are mainly used as general-purpose rubbers, butadiene-nitrile rubbers are used as petrol and oil resistant rubbers, organosilicon rubbers are heat and frost resistant, and urethane rubbers are wear resistant.
Softeners(stearin, oleic acid) increase the plasticity of raw rubber and the softness of rubber products.
Fillers increase the hardness and strength of rubber products. These include carbon black, zinc oxide, chalk, kaolin, etc., as well as sleeve and cord fabrics and fibers (cotton, viscose, nylon, nylon), steel wire cord is also used.
During vulcanization, linear macromolecules of rubber interact with the vulcanizer, as a result, a three-dimensional (cross-linked) network is formed and the rubber turns into rubber.
Sulfur is the main vulcanizing agent for general purpose SC, nitrile butadiene and other rubbers. For vulcanization, molded raw rubber blanks are heated to a temperature of 140 ... 180 ° C; molding can be combined with heating.
Accelerators vulcanization (captax, thiuram, etc.) together with zinc oxide not only reduce the vulcanization time, but also provide the possibility of vulcanization at room temperature.
For the manufacture of soft rubber (car tubes, balls) and rubber, 1 ... 3% sulfur is introduced; with a mass content of sulfur of 4 ... 7%, solid rubber is obtained. For vulcanization of organosilicon SCs, benzoyl peroxides are used; for urethane SCs, isocyanides are used.
Antioxidants(paraffin, petroleum jelly, etc.) slow down the process of rubber oxidation, increase the stability and service life of rubber products.
Manufacturing of rubber products. The process consists of the preparation of rubber compounds, vulcanization and finishing of products.
Mixing components ensures uniform distribution of all components in the rubber, it is produced on rollers or in closed mixers. The resulting raw rubber is a homogeneous plastic mass, which is easily given the desired shape.
To receive sheet rubber raw rubber mixture is processed on calenders, the working body of which is hollow heated mill rolls made of chilled cast iron. On calenders, fabrics are also lined with raw rubber, squeezing rubber sheets and fabrics smeared with rubber, and processing impregnated cord. From a sheet blank, if necessary, cutting is carried out on cutting machines or punching presses.
Rubber profiles(tubes, cords) are obtained by injection - extrusion of raw rubber on a worm press through the matrix of the Product complex shape receive by methods pressing and injection molding
The resulting semi-finished products are subjected to vulcanization and finishing. Density different varieties rubber from 0.9 to 2 g/cm3, tensile strength from 3 to 60 MPa, relative elongation 200…800%. It should be emphasized that rubber and rubber (as well as some types of plastics and other materials) are characterized by relaxation (weakening) of stresses, which increases with an increase in the force and strain rate and with an increase in temperature.
2. Types of rubber.
Rubbers are divided into the following main groups:
1) general purpose rubber(operating temperatures from -50 to +150 °С) - can work in water, air, weak solutions of acids and alkalis (tires, belts, sleeves, conveyor belts, electrical cable insulation);
2)special tires:
a) heat-resistant rubber - withstand temperatures up to 400 ° C;
b) frost-resistant rubber - withstand temperatures down to -150 ° C;
c) oil- and petrol-resistant rubbers - they work in the medium of mass, fuel, gasoline;
d) electrical rubber - there are dielectric and electrically conductive (consist up to 70% of soot and graphite);
e) magnetic;
e) friction, etc.
3. In mechanical engineering, rubber products are used for moving devices (tires, drive belts, conveyor belts), in pipelines for transporting liquids, gases (pressure and suction hoses, connecting hoses, tubes), as supports, buffers, insulation, seals (glands, cuffs, gasket plates, rings), etc.
4. Gasket materials are designed to create tightness of mating parts in order to protect against dust ingress, as well as leakage of lubricants, gases, etc. Gasket materials include leather, fiber, felt, cardboard, paronite, klingerite, cork, asbestos-metal gaskets and rings, fluoroplast-4 .
Technical leather used for the manufacture of cuffs and seals for pumps, compressors, presses. It is well preserved in the environment of gasoline, oil, but has a weak chemical resistance and an increased ability to absorb water. Leatherette (fabric covered with a special film) and fiber are used as leather substitutes.
Cushioning fiber(FT grades) are obtained from special paper (filter type) treated with a concentrated solution of zinc chloride. The fiber is used to make gaskets and washers, and a special electrical fiber is used as an insulating material.
Felt made by sealing wool. He has high thermal insulation properties. Technical felt is used for the manufacture of oil seals, gaskets between metal surfaces, as well as for oil filters.
Paper and cardboard made from cheap woods. They are used as electrical insulating materials and gaskets.
Paronite – sheet material, made from asbestos, rubber and fillers. They are used in the form of sealing gaskets for connections in motors, steam pipelines, hydraulic installations and other mechanisms operating at temperatures up to 450 ° C.
Klingerite- sheet material made from asbestos mixed with graphite, minium, iron oxide and rubber. Klingerite gaskets are used in the joints of machines operating at temperatures up to 200 °C.
Cork It is made from the bark of a cork or velvet tree and is used as insulating gaskets and seals in motors in electrical installations.
Asbestos-metal gaskets and rings used to seal joints of metal surfaces operating at temperatures up to 350 ° C and high pressure (head gaskets in internal combustion engines).
Fluoroplast-4 used for the manufacture of sealing gaskets, cuffs, bellows.
In gas supply systems at the installation sites of devices and instrumentation, threaded and flanged connections are used. Such connections are characterized by insufficient tightness. To seal the joints, gaskets and sealing materials should be used, to which the following requirements are imposed:
- the gasket material must retain its physical properties and not corrode;
- there must be no deformation of the sealing surface;
- the material must meet the requirements of mechanical properties;
- as far as possible, it should be inexpensive and accessible.
For the manufacture of gaskets, a large number of
various materials.
Paronite (GOST 481-80). It is made from asbestos and rubber by vulcanization and rolling under high pressure; designed for sealing flat connectors with various media. Paronite is a universal gasket material and is used for cold and hot gases, air, oils, petroleum products, etc. (Table 10.1). Depending on the purpose, it is produced in seven grades. Of these, PMB grades (for liquefied and gaseous hydrocarbons) can be recommended for limiting pressures up to 1.6 MPa and a temperature range from -40 to +60 ° C. Paronite MPB is produced with a thickness of 0.4; 0.5; 0.6; 0.8; one; 1.5; 2; 2.5; Zmm, sheets 500,1000,1500 mm long and 500,750,1000 mm wide. Paronite gaskets are impregnated with cylinder oil and coated with graphite powder. They must comply with the requirements of GOST 15180-70.
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Gasket material |
Sheet thickness, mm |
Purpose |
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Paronite according to GOST 481-80 (PMB grades), plastics (VD and ND polyethylene), fluoroplast-4 and fluoroplast-4 gasket tape |
For sealing joints on gas pipelines with pressure up to 1.2 MPa and in installations liquefied gases up to 1.6 MPa |
|
|
Technical sheet rubber and oil and petrol resistant without fabric gaskets according to GOST 17133-83 and 7338-90 |
For sealing joints on gas pipelines with pressure up to 0.6 MPa |
|
|
Annealed aluminum sheet or aluminum strip or aluminum alloys annealed according to GOST 21631-76, 13722-78, 13726-78 |
For sealing joints on gas pipelines of all pressures, including those transporting sour gas |
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Copper sheet soft in accordance with GOST 495-92 (grades M1, M2) |
For sealing joints on gas pipelines of all pressures, except for gas pipelines transporting sour gas |
Plastics. Plastics are used for flanged connections of gas pipelines various kinds, similar in elasticity to rubber: plastic compound and polyethylene high density. PVC compound is used, and high-density polyethylene (VD) according to GOST 16338-77 and low density (ND) according to GOST 16337-77E with a thickness of 1-4 mm, fluoroplast-4 (PTFE) with a thickness of 1-4 mm according to GOST 10007-80E and gasket tape made of fluoroplast-4 (PTFE) according to GOST 18999-73 is used for the manufacture of gaskets for flat and round section, as well as for complex gaskets, in which the core is made of asbestos, rubber or corrugated steel, and the lining is made of fluoroplast.
Technical sheet rubber(GOST 7338-90) is supplied in sheets and rolls. This material has a high elasticity, which makes it possible to achieve tightness between the metal surface and the gasket with low clamping forces. Rubber is a chemically resistant material, impervious to gases and liquids. For gaskets, it is usually recommended to use sheet technical rubber according to GOST 7338-90 without fabric gaskets, since in the presence of interlayers, seepage can sometimes occur. By hardness, it is divided into soft (m), medium hard (s) and high hardness (n). By resistance to heat-resistant (T) and frost-resistant (M). It is recommended to use oil and petrol resistant rubber (MB) grades A and B, depending on the degree of resistance.
Annealed aluminum sheets(GOST 2 1 631-76), copper sheet soft(GOST 495-92). Metal gaskets are made from these materials, which provide sufficient density at high pressures and medium temperatures. The disadvantages include the need to create large efforts to ensure the tightness of the connection, insufficiently elastic properties and relatively high manufacturing costs. For gaskets, it is recommended to use annealed aluminum sheets in accordance with GOST 13722-78 and GOST 21631-76 or annealed aluminum and aluminum alloy tapes in accordance with GOST 13726-78, sheet copper soft marks Ml and M2 according to GOST495-92.
To give the gaskets fire-resistant properties, you can use:
- asbestos cardboard (GOST 2850-80) grades KAON-1, KAON-2. Cardboard sheets 900 x 900, 1000 x 800, 1000 x 900 and 1000 x 1000 mm are available in thickness 2; 2.5; 3; 3, 5; 4; 5 mm;
- asbestos reinforced fabric (GOST 2198-76). It is a rubberized and graphitized fabric of plain or twill weave based on brass wire, and on the weft - from asbestos yarn reinforced with brass wire. Sheets of cardboard with a width of 1000 and 750 mm and a length of at least 1500 mm are produced with a thickness of 0.6; 0.7 and 1.1 mm. Corrugated metal gaskets are also used with
soft packing used for nominal pressure from 1.6 to 4.0 M Pa and temperatures up to 450 °C. For the manufacture of shells of corrugated gaskets with packing, soft annealed aluminum sheet (GOST 21631-76 and 13726-97) 0.3 mm thick or a sheet of soft annealed low carbon steel 0.3 mm thick. The stuffing of metal corrugated gaskets is made from whole sheet asbestos according to GOST 2850-80.
To seal threaded joints, a linen strand should be used in accordance with GOST 10330-76, which, during the connection, is coated with red lead in accordance with GOST 19151-73 or white lead in accordance with GOST 12287-77, mixed with drying oil in accordance with GOST 7931-76, fluoroplastic material (FUM) in the form tape according to TU 6-05-1388-70 grade 1 and cord according to MRTU 6-05-870-66 grades B and K, as well as other sealing material that ensures the tightness of the connection.
Gasket materials are used to connect hollow parts and pipes to prevent leakage of liquids and gases.
In mechanical engineering, the following gasket sealing and stuffing materials are used.
Fiber - made by impregnating rag paper pulp strong mortar zinc chloride and subsequent pressing. It is widely used as a cushioning and electrical insulating material; on sale it is found in the form of sheets, rods and tubes of black or brown-red color. A significant disadvantage of fiber is hygroscopicity: under the influence of water and gasoline, it swells, and when dried, warps and shrinks. Therefore, fiber pads are often replaced with paranite pads.
Paranit is a sheet gasket material consisting of asbestos and rubber. Gaskets made of paranit are resistant to gasoline and oil and are therefore used to seal joints in gasoline and oil pipelines.
Copper-asbestos gaskets - consist of asbestos cardboard, overlaid on both sides with red copper foil. These gaskets are resistant to high temperatures and are widely used in internal combustion engines.
Leather pads are used as temporary and in places that are not exposed to high heat; they are considered very good material for gaskets in petrol and oil taps.
Cork pads are made from small pressed cork; they are designed to seal various joints.
To avoid chipping, the gaskets are glued on both sides with cardboard.
Rubber gaskets in the form of sheets, rings, tips are placed mainly to prevent the flow of water.
Cannot be applied rubber gaskets in those places where the temperature exceeds 100 °, as well as in the joints of petrol and oil pipelines.
Paper and cardboard gaskets are used under engine cylinders and other large surfaces that are not exposed to high temperatures.
Gaskets are made of ordinary, non-smooth and thick enough paper or cardboard. In order for the paper to more easily fill all the irregularities and better stick to the surfaces to be sealed, it should be well lubricated with oil on both sides.
Klingerite is made from asbestos mixed with graphite, red lead, iron oxide and rubber. It is sold in the form of sheets. Klingerite gaskets are used for high temperatures(up to 185°) and high pressures (up to 12 atm). Klingerite gaskets must be lightly oiled on both sides before installation; under the influence of high temperature, they become extremely dense and elastic, that is, they easily bend and adhere more closely to the surfaces to be joined.
Lead white, red lead, liquid glass, and soap for gasoline and kerosene pipelines serve as an addition to solid gaskets.
Felt is used to seal shafts and axle shafts coming out of oil reservoirs of bearings, crankcases, gearboxes, etc. Only the best, completely white and dense rabbit wool felt (felt) should be used as a sealing material.
Tow and hemp serve as a cushioning material when connecting pipes. With the right cut, the hemp is wound on the thread clockwise, and with the left, vice versa. Hemp and tow, impregnated with lard, also serve as material for stuffing glands.
rental block
Gasket materials are used to seal flanged joints of pipelines, fittings, devices and other equipment.
The gasket material must be elastic. When tightening the flanges, the gasket is deformed and, filling the smallest irregularities of the flange surfaces, ensures the tightness of the connection.
The gasket must be strong enough to withstand the pressure of the medium, seeking to pull it out of the space between the flanges, and elastic enough to maintain the tightness of the connection during temperature deformations.
In addition, the gasket material is required to be resistant to aggressive media and the ability to maintain strength in certain temperature conditions.
The most commonly used gasket materials are:
Gasketboard is produced in two grades: A - impregnated, B - unimpregnated. Sheet cardboard soaked in hot drying oil is used in flange connections for pumping oil products, water and many other neutral media. The maximum allowable pressure of the transported medium is 1 MPa, the maximum temperature is 40°C.
Asbestos cardboard is used in hot (up to 300°C) gas, and after appropriate impregnation in liquid and steam media at pressures up to 2.0 MPa. sheet asbestos, coated liquid glass, drying oil or rubbed with graphite, is used for the manufacture of gaskets installed on pipelines for sulfuric, hydrochloric, nitric acids and other aggressive environments. Asbestos cords are used to seal stationary parts of machines and apparatuses: SHAM (magnesian asbestos cord) can withstand temperatures up to 425 ° C, SHAPT (asbestos cord of increased heat resistance) - temperatures up to 300 ° C.
Sheet paronite is widely used as a gasket material for pipelines of hot water, condensate, steam at temperatures up to 300 ° C, as well as alcohol, sulfuric acid, compressed air at temperatures up to 100°C and in many other cases. Some varieties of paronite are resistant to the action of petroleum products.
General-purpose sheet paronite (PON brand) is used to seal flat connectors of fixed joints of compressors with a working medium pressure of not more than 4.0 MPa.
Compound vinyl chloride sheet is used in acidic and alkaline environments at a temperature not exceeding 80 ° C and low pressures.
PSG sheet polyisobutylene is characterized by very high resistance to most chemically active media, including acids - nitric (up to 32% concentration), sulfuric, hydrochloric, formic, acetic (up to 50%), caustic soda solutions (up to 50%) and etc. However, polyisobutylene is unstable to oils, gasoline and some other organic liquids.
Technical rubber (sheet) is used for sealing flange joints when operating on steam, water, weak alkalis, acids, neutral liquids and gases at temperatures up to 100°C.
Polyethylene is resistant to 40% nitric acid, hot concentrated of hydrochloric acid, 60% sulfuric acid. Particularly resistant to hydrofluoric acid, insoluble in ethyl alcohol, acetone, benzene, carbon tetrachloride. Therefore, polyethylene is used as gaskets for flange connections during the transportation of these products. In addition, polyethylene is used to coat rubber and asbestos gaskets to improve their chemical resistance.
Currently, fluoroplast-4 is widely used for gasket material in many industries. Fluoroplast has high heat resistance, retaining its properties at temperatures from -100 to +300 ° C, it is not affected by boiling alkalis, oxidizing agents, acids, chlorine, bromine and iodine. It is practically insoluble and does not swell in any known solvent.
Gasket tape made of PTFE-4 is designed for the manufacture of gasket and insulating material resistant to strong aggressive environments, operating at temperatures from -60 to +250 ° C.
Fluoroplastic sealing material (FUM) is used as a chemically resistant self-lubricating packing and gasket material operating at temperatures from -60 to +150°C and pressure up to 6.5 MPa.
Fluoroplast-4 is often used as a coating for gaskets made of other materials (usually asbestos) in cases where highly active media are transported through a pipeline at temperatures up to 250°C.
Red annealed copper (sheets and wire) and mild steel are used for sealing flange joints of pipelines, devices and machines operating at high pressures and temperatures up to 350°C.
Aluminum is used for the manufacture of gaskets in gaseous media at high pressure (hydrogen, nitric mixture, water gas, etc.).
Steel lens gaskets are used on high and ultra-high pressure pipelines (up to 200 MPa) at temperatures up to 1000°C.
For the manufacture of asbestos-metal gaskets, sheet copper, aluminum and asbestos are used. Gaskets are durable and heat-resistant, they are used on pipelines when transporting water, steam, acids and alkalis at high pressures and temperatures.
Stuffing materials ensure the tightness of stuffing box seals in various equipment and fittings.
Cotton dry stuffing is used for sealing stuffing boxes and fittings in water pumps and water pipes.
Salted hemp packing and cords are used for fittings and water pumps at pressures up to 15.0 MPa and temperatures not exceeding 50°C.
Dry asbestos cord is used in gaseous environments at high temperatures, asbestos greasy and graphic cord is used for water, gas and steam pipelines at temperatures up to 300 ° C and a pressure of 2.5 MPa. Asbestos cord impregnated with special substances (paraffin, graphite, technical vaseline, etc.). used for sealing glands of acid pumps. Graphite pressed rings are used in gas blowers and steam turbines.
Lead, babbitt, bronze, copper, steel and other metals and alloys are used for gland packings in high pressure pumps and compressors.
Rubberized cords are used in various machines operating at medium pressures and temperatures of 100°C. Cords made of asbometallic fabric can be used at temperatures up to 400C.
Recently, there has been widespread O-rings plastics and fiberglass.
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This topic belongs to:
Hydraulics. Thermodynamics
Hydraulics is one of the areas of the unified science of fluid mechanics, called technical hydromechanics, which studies the issues of equilibrium and movement of various fluids. The laws of hydraulics are widely used in many areas of technology.