Stuffing, sealing and lining materials. Refractory and heat-insulating, gasket and stuffing materials Gasket materials in mechanical engineering

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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 cushioning material on pipelines 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.

Sheet paronite general purpose(PON brand) is used for sealing flat connectors of fixed joints of compressors with a working medium pressure of not more than 4.0 MPa.

Compound PVC sheet is used in acidic and alkaline environments at temperatures 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 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 gaskets and insulating material, resistant to strong aggressive environments, operating at temperatures from -60 to +250 ° С.

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 pipelines of high and over high pressure(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 for 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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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.

This material includes sections:

Properties of liquids

Information from hydrostatics and hydrodynamics

Practical use of the laws of hydrostatics and hydrodynamics

Fluid flow through holes and nozzles

Gas condition parameters

Ideal and real gases

Heat capacity of gases

First law of thermodynamics

Thermodynamic processes

Second law of thermodynamics

Water vapor properties

Moist air properties

Expiration and throttling

Fundamentals of heat transfer

The main assembly units of pipelines

The principle of operation and the device of pipeline fittings

Repair and testing of pipelines and fittings

Rules for the safe operation of pipelines and fittings

Drawing and reading piping diagrams

Volumetric pumps. General information

Reciprocating pumps

The main assembly units of the pump

Suction and discharge processes

gas caps

Piston pump indicator chart

Dosing and synchrodosing electric pump units

Steam direct acting pumps

Examples of drawing up and reading diagrams of pumping units

dynamic pumps. General information

Scheme of installation of centrifugal pumps

Main Parameters of Centrifugal Pump

Euler equation for determining the theoretical and actual heads of a centrifugal pump

Characteristics of centrifugal pump and pipeline

Collaboration of centrifugal pumps

Axial force and ways to unload it

The main assembly units of centrifugal pumps

Horizontal single wheel and multistage centrifugal pumps

Centrifugal cantilever and submersible chemical pumps

Centrifugal sealed electric pumps. Pumps made of non-metallic materials

Typical schemes of pumping units

General provisions for the operation of pumps

Regulation and lubrication of pumps

Automatic control of pumping units

Operation of piston pumps

Operation of centrifugal pumps

Volumetric compressors. General information

Main parameters of reciprocating compressors

Ways to control the performance of reciprocating compressors

When connecting pipeline parts to pipeline fittings, it is necessary to ensure the tightness of these connections in order to avoid leakage of the medium.

Leakage is especially dangerous when transporting aggressive and explosive media, as well as those under pressure and at high temperatures.

main type detachable connections pipelines are flanged connections, and its integral element is a gasket.

The gasket material must be the following properties:

ü elasticity, so that when pressure is created, the smallest irregularities of the flange surface are filled, ensuring the tightness of the connection;

ü strength, in order to withstand the force of the pressure of the environment;

ü Resistant to aggressive environments.

Depending on the purpose and operating conditions of pipeline fittings, cardboard, paronite, sheet asbestos, rubber, fluoroplastic, polyethylene, aluminum, lead, copper, mild annealed steel are used as gasket materials.

The choice of gasket materials for sealing flanged joints depends on the transported medium and its operating parameters.

Some gasket materials depending on the medium parameters and types of sealing surfaces are presented in table 9.

Table 9 - Gasket materials depending on the parameters of the medium and types of sealing surfaces

Table 9 continued

Table 9 continued

For sealing glands of pipeline fittings and gland compensators, packings are used in the form of cords woven from asbestos or hemp threads impregnated various formulations giving them resistance to aggressive environments.

The material for stuffing glands is selected depending on the operating conditions. Fatty asbestos packing can be used at temperatures not exceeding 200 0 C, since at higher temperatures fatty substances flow out and the stuffing box density decreases.

At temperatures above 200 0 C, asbestos pro-graphic packing or special asbestos-metal packings are used, impregnated with a special composition that is resistant to destruction under the influence of transported media and high temperature.

Fluoroplastic packing is used in the form of rings or a cord, which provides high resistance to acidic and alkaline media at temperatures up to 250 0 C.

Gland packing must be made of braided cord square section in width equal to the width of the stuffing box. Separate rings are cut from such a cord with ends beveled at an angle of 45 0. The rings should be placed in the stuffing box opposite the cut lines, with the sealing of each ring separately. During assembly, the bottom box should enter the chamber by at least 5 mm, but not more than 1/7 of its height.

Tightening of glands should be carried out evenly, without distortions of the bottom box.

QUESTIONS FOR SELF-CHECKING

1. By what main features can pipe fittings be classified?

2. What is a nominal diameter? What conditional pressure?

3. What is a gate valve? What are the valves, where and how are they installed?

4. List the main advantages and disadvantages of valves in comparison with other types of pipeline fittings.

5. What is a valve? What are its main elements?

6. List the main advantages and disadvantages of the valve in comparison with other types of pipeline fittings.

7. What are the types of valve sealing surfaces?

8. What is a faucet? What types of cranes do you know?

9. List the main advantages and disadvantages of valves compared to other types of pipeline fittings.

11. What applies to safety and protective pipeline fittings?

12. How are pipeline fittings marked?

13. Decipher the marking of the following types of pipeline fittings: 15kp3p; 11h3bk; 30s64br.

14. For what reasons is the normal operation of pipeline fittings disturbed?

15. What is the revision of pipeline fittings, what does it consist of?

16. How is the repair of pipeline fittings (valve, gate valve, cock) carried out? What devices are used for this?

17. How is pipe fittings tested? What are the types of testing?

18. Formulate the basic principles for choosing pipeline fittings.

19. What properties should a gasket have?

20. List the main materials of gasket materials and their areas of application.

21. How long maximum temperature Can PTFE be used as a gasket material?

23. How to properly stuff the stuffing box?

For the manufacture of gaskets are used as non-metallic materials, as well as metals. Metal gaskets are used for critical objects in severe valve operating conditions (high temperature, high pressure, etc.), but they require significantly greater tightening forces than soft gaskets.

non-metallic materials. Rubber is the most suitable material for sealing detachable connections. It is elastic, requires little effort to tighten the seals, and is practically impervious to liquids and gases. Rubber is used up to a temperature of 50 ° C, and heat-resistant rubber - up to 140 ° C.

For gaskets, sheet technical rubber is usually used according to GOST 7338-65 without fabric interlayers, since the presence of interlayers sometimes creates a leakage of the medium through the fibers of the interlayer. By hardness, rubber is subdivided into soft, medium hard and hard. There are five types of rubber: oil and petrol resistant (grades A, B and C depending on the degree of resistance), acid and alkali resistant, heat resistant, frost resistant and food grade.

Pulp liner pads are widely used in steam fittings low pressure and water at operating temperature tp< 120° С и рабочем давлении Pp до 0,6 МПа, для масла при tp < 80° С и Pр < 4 МПа и в других случаях. Применяется картон водонепроницаемый и прокладочный (пропитанный), последний используется и для нефтепродуктов при tр <= 85° С и рр < 0,6 МПа. Для картона допускается контактное давление не более 55 МПа. Для высоких температур целлюлозный картон не пригоден, так как обугливается.

Sheet fiber (FLAC) is paper or cellulose treated with zinc chloride and then calendered. It is used for gaskets in fittings at temperatures up to 100 ° C. It is used when working on kerosene, gasoline, lubricating oil, oxygen and carbon dioxide. Friction coefficient between fiber and dry steel μ = 0.33.

Asbestos as a gasket material is used in fittings at elevated and high temperatures. Material of mineral origin in technology is used after processing in the form of sheet cardboard or cord. At 500°C, the strength of asbestos is reduced by 33%, and at 600°C, by 77%. Asbestos is resistant to alkalis, anthophylite-asbestos is resistant to acids.

Asbestos non-impregnated cardboard has a loose structure, low strength, and high heat resistance; it is used for fittings operating at temperatures up to 600 ° C; gate valves for hot blast, generator and flue gases and for other fittings that do not operate on liquid. Asbestos cardboard impregnated with natural drying oil can be used for oil products at pressure up to 0.6 MPa and temperature tp< 180° С, однако замена его при смене прокладок или ремонте арматуры затруднена, так как он прилипает к металлическим поверхностям. Для уплотнения средних фланцев газовых больших задвижек используется также асбестовый шнур, который укладывается спиралью на поверхности фланца, предварительно смазанной техническим вазелином. Кроме того, для прокладок используются специальные ткани с пряжей из мягкой латунной или никелевой проволоки. Изготовляют также комбинированные прокладки из колец различной формы и сечений, сердцевина которых выполняется из асбеста, а облицовка из тонкого металлического или пластмассового листа. Такие прокладки имеют хорошие эксплуатационные свойства, но сложны в изготовлении.

Sheet paronite (GOST 481-71) is made from a mixture of asbestos fibers (60-70%), solvent, rubber (12-15%), mineral fillers (15-18%) and sulfur (1.5-2.0%) by vulcanization and rolling under high pressure. The heat resistance of paronite depends on the amount of rubber in it.

Paronite is a universal gasket material and is used in fittings for saturated and superheated steam, hot gases and air, alkali solutions and weak solutions of acids, ammonia, oils and petroleum products at temperatures up to 450°C. The coefficient of friction of paronite on metal μ = 0.5. The elasticity of paronite is low. At a contact pressure over 32 MPa, all leaks in the material are eliminated. The relaxation of stresses in the period immediately after tightening is significant. After compression at a contact pressure of 70 MPa, the tightness of the connection is maintained even at a contact pressure on the gasket equal to the working one. The highest allowable contact pressure on the paronite is 130 MPa. In order to improve the tightness of the joint and increase the resistance to expansion of the gasket by the medium, two or three narrow triangular grooves are usually created on the sealing surfaces of the joint, into which the paronite is pressed under the action of the tightening force. Such grooves are also made when using other non-metallic gaskets. Paronite sheets are produced up to 6 mm thick. It is advisable to use the gasket as thin as possible, but its thickness should be sufficient to seal the joint for a given roughness of the machined surfaces and the sealing area. Sheet paronite is produced in the following grades: PON, PMB, PA, PE (see Table 4.29), PS and PSG (the last two are special).

4.29. Conditions for the use of paronite (according to GOST 481-71)

Continuation of the table. 4.29

Paronite grades PON and PA is tested for sealing ability in a steam environment at a temperature of 450 ° C and a pressure of 10 MPa. A gasket with an outer diameter of 120 mm and an inner diameter of 80 mm, lubricated with oil graphite paste, must maintain tightness for 30 minutes at a contact pressure of 22.5 MPa. In addition, paronite of these grades, as well as grade PMB, is tested for sealing ability in kerosene at a temperature of 20 ° C and a pressure of 15 MPa. The gasket with an outer diameter of 120 mm and an inner diameter of 80 mm, lubricated with oil graphite paste, at a contact pressure of 32.4 MPa, must maintain tightness for 30 minutes.

Paronite of a special grade PS is intended for ethyl alcohol, liquid oxygen, L-1 oil and air. It is used for pressures up to 7.5 MPa at operating temperatures from -182 to +400°C, depending on the type of connection and working medium. Paronite brand PSG (special graphitized paronite) is intended for ethyl alcohol, water vapor and steam gas. It is used for pressures up to 7.5 MPa at operating temperatures up to 450° C (for alcohol - up to 50° C). Paronite sheets have dimensions from 0.3 X 0.4 to 1.5 X 3.0 m, the thickness of paronite grade PON sheets is from 0.4 to 6.0 mm. Each brand of paronite has its own range of sizes and thicknesses.

Plastics for reinforcement gaskets are used at low ambient temperatures. Polyvinyl chloride plastic compound in terms of elasticity is closest to rubber, it is used for fittings in chemical industries at a relatively narrow temperature range (from -15 to 4-40 ° C). Polyethylene can be used as gaskets at ambient temperatures from -60 to +50°C. Fluoroplast-4 and fluoroplastic sealing material (FUM), produced in the form of cords of various profiles and sections, are used for temperatures from -195 to +200°C. Viniplast as a gasket material is used to a limited extent.

metal materials. Metal gaskets are made in the form of flat rings of rectangular section from sheet material or in the form of rings of shaped section from pipes or forgings. The latter include lens gaskets of lentil section, gaskets with a section in the form of an oval located parallel to the axis of the gasket, and comb gaskets having a rectangular cross section with triangular protrusions in the form of a comb. In addition, combined gaskets are produced, consisting of a soft core (asbestos or paronite), lined with sheet material made of aluminum, mild steel or corrosion-resistant steel 08X18H10T or 12X18H10T. Advantages of metal gaskets: sufficient density at high pressures and temperatures of the medium, the thermal expansion coefficient is close to the thermal expansion coefficient of the flange material and studs or bolts, the possibility of reuse after appropriate repair. The disadvantages include: the need to create large efforts to ensure the tightness of the connection, relatively low elastic properties, significant stress relaxation and relatively high manufacturing costs. In table. 4.30 provides some information about the metals used for the manufacture of reinforcement gaskets.

4.30. Metals used to make gaskets

Stuffing materials

Materials for gland packing (Table 4.31) must have high elasticity, physical resistance at operating temperature, chemical resistance against the action of the working environment and possibly a low coefficient of friction. As stuffing materials, the following are mainly used: cotton materials, hemp, asbestos cord, asbestos, graphite, talc, fiberglass and fluoroplastic. Asbestos is most often used in the form of a braided cord of square or round section, but rolled cords without weaving or combing the fiber (hemp, etc.) can also be used. The most expedient is the use of packing from pre-prepared and molded rings.

4.31. Mainmaterialsforomentalstuffings(withtaking into accountGOST 5152 — 66)

Continuation of the table. 4.31

Continuation of the table. 4.31

Cast iron.

It is a non-ductile alloy of iron and carbon (2.5-3.6%). It has good casting qualities, low cost, but it is a brittle material (it breaks down immediately, in ductile materials there is a period of plastic deformation, when you can set the moment of failure). In this regard, cast iron has a limited scope.

Cast iron is used to make fittings, brackets, racks.

Gray cast iron СЧ15-32(numbers indicate tensile and compressive strength, respectively) is used for the manufacture of fittings on a low pressure network.

Malleable cast iron KCh30-6(cannot be forged, but has increased plastic properties) is used for fittings in medium and high pressure networks.

Heat-resistant cast iron ZhCh-1 used for fittings operating at temperatures up to 600 0 С.

Gasket materials.

Their purpose is to ensure the density of fixed joints. Therefore they:

1. should be cheap and available (because they need to be replaced quite often),
2. must be elastic (to achieve a high density of joints),
3. must have sufficient strength (so as not to collapse, crush or extrude when tightened),
4. must retain their physical properties at the temperature of the working environment,
5. must not be subject to corrosion.

Paronite used for cold and hot gases with temperatures up to 450 0 С in gas pipelines with pressure up to 1.2 MPa, in LPG installations with pressure up to 1.6 MPa, for oil products.

Plastic, fluoroplast for sealing flange connections in gas pipelines with pressure up to 1.2 MPa, in LPG installations with pressure up to 1.6 MPa.

metal rings. Their "-" is the creation of the necessary efforts to achieve the density of the joints. Aluminum– for sealing equipment, LPG installations at all pressures, as well as for sour gases. Copper- for sealing equipment, LPG installations.

Rubber having high frost and oil and petrol resistance, it is used for sealing joints in gas pipelines with pressure up to 0.6 MPa.

Asbestos is used to impart fire-resistant properties to gaskets (asbestos cardboard, asbestos reinforced fabric).

Linen strand oiled with red lead used for sealing threaded connections.

Most designs of gas equipment have a stuffing box for sealing moving joints.

Stuffing box materials must have:

1. high elastic properties
2. physical resistance against the action of the working environment
3. low coefficient of friction

For these purposes, apply: asbestos in the form of a braided cord,

hemp cord,

graphite,

talc,

fluoroplast and etc.

(The cord is lowered into the melted beef lard, boiled for 5 minutes, cooled and rolled in graphite powder.)

Materials Science - Non-Metallic and Composite Materials

NON-METALLIC MATERIALS

Traditional non-metallic materials include fibrous materials (wood), polymeric organic and inorganic materials (plastics), rubbers and rubbers, adhesives and sealants, paint coatings, glass, ceramics, as well as new generation materials - composite materials based on non-metal.

PLASTIC MATERIALS (plastics, plastics) are called multicomponent artificial materials based on natural or synthetic high-molecular organic substances, which include: high-molecular base-binder (synthetic resins, ethers, cellulose); fillers (powdery, fibrous, reticular substances of organic or inorganic origin), plasticizers (oleic acid, stearin, dibutyl fluorate), stabilizers, dyes, hardeners and other special additives.

Plastic classification

a) by binder type (polymer): phenolics (base - phenolic and phenolic resins); epoxy resins (epoxy resin); amidoplasts (polyamide resin).

b) by type of filler:

– pressing powders - with powdered organic (wood flour, cellulose, graphite) or mineral filler (talc, quartz flour, microasbestos, etc.);

– press materials:

– fibers - with a fibrous filler of cotton and linen tows;

– fiberglass - in the form of glass threads;

– asbestos fibers - in the form of asbestos threads;

– layered plastics- with woven and sheet filler, including paper sheets (getinax), cotton fabrics (textolite), fiberglass (glass fiber), asbestos fabrics (asbestos textolite);

– gas-filled plastics- with air filler (foam plastics, foam plastics).

c) depending on the behavior of the resin when heated:

– thermoplastics

– thermoplastics

Plastic recycling methods: extrusion, pressing, injection molding, casting, vacuum and pneumatic forming, rolling, foaming, welding, hot spraying, planing into sheets, chipping

Rubbers called high-molecular materials that are obtained by vulcanization (heating up to 100–150С) of a mixture of natural or synthetic rubber with various fillers (ingredients). In the process of vulcanization, spatial "cross-linked" (network) structures are formed, replacing the linear or weakly branched structure of rubbers. Here plays an active role vulcanizing agent - sulfur (or selenium), the amount of which determines the size of the cell structure, elasticity and hardness of rubber: a) soft rubber (2–4% S); b) hard - semi-ebonites (12–13% S); c) ebonites (30–50% S). In addition to sulfur, rubber contains: fillers, softeners,antioxidants,flame retardants, fungicides, deodorants,dyes and pigments, regenerate.

Rubber products are obtained by vulcanization (heat treatment) pressed raw rubber parts. Rubber products are often reinforced with fabric or metal mesh.

Adhesives and Sealants

belong to film-forming materials, since they are capable of forming strong films upon hardening that adhere well to various materials.

Adhesives are used for gluing dissimilar materials (metal, ceramics, plastic, wood), and sealants provide sealing and sealing of riveted, welded and bolted joints, fuel compartments and tanks, various metal structures, devices, assemblies, seams, joints, etc. Adhesives and sealants can be in the form of liquids, pastes, putties, films.

Paint and varnish materials (lcm)

Paints and varnishes are multicomponent compositions applied in a liquid state to the surface of products and drying with the formation of films held by adhesion forces. Appointment of paint and varnish coatings: a) protection metals from corrosion, wood and fabrics - from rotting and swelling; b) for decorative purposes– giving products the desired appearance; in) to achieve special properties- electrical insulating, heat-shielding, light-resistant, etc.

There are paints and varnishes: transparent (lacquer); covering (enamel) and preparatory (primer). Coatings are applied manually by brushing, spraying, dipping and other methods. Reliability of product surface protection is usually achieved by using multilayer coatings.

glass

Glasses (or glass) are called supercooled substances obtained from liquid melts of inorganic compounds and their mixtures.

Glasses are based on glass-forming oxides, according to which glasses are divided into silicate (SiO 2), aluminosilicate (A1 2 O 3 and SiO 2), borosilicate (B 2 O 3 and SiO 2), aluminoborosilicate A1 2 O 3, B 2 O 3 and SiO 2) , boron-fluoroaluminosilicate (B 2 O 3, A1 2 O 3, F and SiO 2), aluminophosphate (A1 2 O 3 and P 2 O 5), aluminosilicate (A1 2 O 3, SiO 2 and P 2 O a), silica-titanium (SiO 2 and TiO 2), silicozirconium (SiO 2 and ZrO 2), etc.

By glass purpose classify for chemically resistant, heat-resistant, electrovacuum, electrical, optical, etc.

The advantage of glasses is their ability to be remelted multiple times without changing their properties.

Liquid homogeneous glass mass is processed into products by various methods : pulling (sheet glass, tubes and rods) , rolling (sheet glass, tubes and rods), pressing (thick-walled products), by blowing (thin-walled products of complex configuration, for example, cylinders of lamps, cathode-ray tubes and other devices), glass powder sintering method (details of complex configuration, operated under conditions of high thermal loads). Direct casting methods (for low-viscosity masses and the manufacture of simple products), injection molding and centrifugal casting are also used. Technique and technological methods are identical with the processing of metals. After manufacturing, glass products and semi-finished products are annealed at 400–600 °C to relieve residual stresses. The duration of annealing depends on the thickness of the product.

Sitallami called artificial materials of microcrystalline structure obtained by directional initiated crystallization of glass products.

Glass-ceramics differ from glasses in higher physical and mechanical properties (hardness, chemical resistance, low dielectric losses at high frequencies and temperatures, high dielectric constant at high temperatures).

Glassware products are molded methods drawing and rolling, pressing, injection molding.

Ceramics - an inorganic material obtained from molded mineral masses in the process of high-temperature firing (sintering), as a result of which a material structure is formed at 1200–2500 ° C, and the product acquires the necessary physical and mechanical properties. Ceramics were the first class of materials to compete with metals for use at high temperatures.

The main components of technical ceramics are: a) oxides(A1 2 O 3 - corundum, ZrO 2, MgO, CaO, BeO, ThO 2, UO 2), b) oxygen-free metal compounds(carbides, borides, nitrides, silicides, sulfides).

Phases may be present in ceramics: a) crystalline(base in the form of chemical compounds or solid solutions), b) vitreous(in the form of interlayers of glass in an amount of 1–10%, binding the crystalline phase), c) gas(located in the pores of ceramics).

Most types of special technical ceramics have a dense sintered structure of a polycrystalline structure; specific technological methods are used to obtain it. The fundamental disadvantages of ceramics are their fragility and complexity of processing.

The main areas of application of ceramic materials include cutting tools, parts of internal combustion engines and gas turbine engines, etc.

Gaskets and sealing materials

Gasket materials are used for sealing joints of body or other parts (especially at high pressures and temperatures inside the sealed cavity), for thermal insulation and electrical insulation of detachable parts, to eliminate possible leakage of liquid and gas breakthrough.

Natural, synthetic or composite materials are used as gasket materials.

Natural materials - cork tree bark, asbestos, felt and annealed copper. Cork tree bark is used at low pressures and temperatures. Its main advantage is oil resistance. Due to scarcity, the use of cork tree bark is limited. Often use cork chips in a synthetic adhesive. Asbestos has strength, elasticity, dielectric properties, it is stable at temperatures up to 1500 °C. Felt is a dense woolen material. Felt pads prevent foreign contaminants from entering the joints, retain lubricating oils, soften shocks and vibrations, and are a good sound insulator. Red annealed copper is used at high temperatures and pressures.

Synthetic materials - oil and petrol resistant rubber, various plastics. These materials are usually good dielectrics, but have low frost resistance, heat resistance and a short service life. Synthetic materials are used in non-critical compounds or as a matrix of composite materials.

Composite materials are cellulose-containing materials or a composition of synthetic material-strengthener. Cellulose-containing materials (paper, thick cardboard) are used as thin gaskets in knots that are not exposed to moisture. From paper treated with zinc chloride, castor oil and glycerin, fiber is obtained - a strong and durable dielectric that is resistant to oil and water. From composite materials, compositions based on oil and petrol resistant rubber are most often used. As a filler, fluffed asbestos, graphite powder, steel foil, steel wire, or a combination of both are used. Composite gasket materials are the most versatile, relatively cheap, and have a long service life.

Technical liquids and gases

1) Lubricants - substances with a lubricating effect, i.e. the ability to reduce friction, reduce wear rate and eliminate jamming of rubbing surfaces. Most lubricants, with the exception of solid lubricants (graphite, molybdenum sulfide, etc.), are liquid.

2) K process fluids are: a) release agents, designed to reduce adhesion in contact of molds and injection molds with rubber and plastic products, b) detergents liquids (for washing parts and components of machines during their production and repair), c) hardening media (prepared on the basis of oils, aqueous solutions of salts, water-soluble polymers).

3)Lubricating fluids (coolants) combine the properties of lubricating oils and process fluids. They simultaneously lubricate the surface of the tool and the workpiece, facilitating deformation and improving the quality of the resulting surface, remove heat, wash off chips, dust and other contaminants, and also protect the surface of the tool and parts from corrosion. Due to the multifunctional purpose of coolants, a wide range of oils, synthetic fluids, aqueous solutions, additives and additives are used for their preparation.

4)liquid fuels - gasolines, diesel fuels, kerosene and fuel oil, which are products of oil distillation. In mechanical engineering, these liquids are used as components of washing liquids, coolants, solvents, etc.

5) In the chemical-thermal treatment of steels, special gas environments . Gases ( nitrogen, ammonia, argon, acetylene, hydrogen, freon, oxygen, krypton and xenon – in electrovacuum technology for filling various devices, methane and propane, carbonic) and their mixtures are also widely used as fuels for flame cutting and hardening, plasma-forming media in ion-plasma processing, welding gases, coolants in refrigeration plants, etc.

6) Various oils and synthetic fluids used as working bodies in presses, hydraulic transmissions and drives, vacuum pumps, shock absorbers, brakes and other devices. These include shock-absorbing fluids, hydraulic oils, vacuum oils, damping fluids, prepared mainly on the basis of mineral oils and organosilicon fluids.

Abrasives

(from Latin abrasio- scraping) - granular or powdery substances intended to equip the working part of cutting tools.

Natural abrasives are: corundum, emery, fan, flint, feldspar, pumice, etc. In industry, the most common artificial abrasives: electrocorundum, carborundum and boron carbide.

Powders are used to produce grinding wheels of various shapes, bars, abrasive heads, segments intended for the production of special abrasive tools.

COMPOSITE MATERIALS

- these are materials consisting of mutually insoluble components that differ greatly in properties from each other (from a relatively plastic matrix material that binds the composition and gives it the desired shape and more solid and durable substances that are reinforcing fillers). Composite materials are used for the production of aircraft, in mechanical engineering, instrument making, energy, in the electronic, radio engineering and electrical industries, as well as in transport, construction and other sectors of the national economy.

Depending on the matrix material There are composite materials with a metal matrix or metal composite materials (MCM), with a polymer - polymer composite materials (PCM) and with a ceramic - ceramic composite materials (CMC).

By type of reinforcing fillers composite materials are divided into: