Working conditions of workers in forge shops of mechanical engineering. Physiological and hygienic characteristics of working conditions for workers in the hot shop of a machine-building enterprise Working conditions in a machine-building shop

Machine tool building, computer technology, instrument making, and the electrical and electronic industries will develop at the fastest pace.

The machine-building industry produces the means of production; therefore, it is the basis for the technical reconstruction and re-equipment of the entire industry of the country and the improvement of working conditions in all branches of the national economy.

The main workshops of machine-building enterprises are preparatory or "hot" workshops (foundry, forging, stamping, thermal) and "cold" (mechanical, mechanical assembly). The latter include welding production, metal plating shops.

Depending on the type and purpose of production, certain technological processes can acquire a special share. For example, in shipbuilding - electric welding operations; in aircraft construction - riveting; foundry and forging shops, etc., are rapidly developing at heavy and transport engineering plants, automobile and tractor plants.

FOUNDRY SHOP

Among the technological processes of metal processing, in terms of a variety of operations and working conditions, foundry production remains one of the most complex and labor-intensive.

The technological process of foundry production consists in obtaining products by pouring molten metal into non-permanent (destructible) mainly earth molds or into permanent molds made of metal (chill casting) or other materials. According to the type of metal, iron, steel, non-ferrous castings are distinguished.

The main foundry processes are the preparation of charge materials for melting, loading into furnaces, melting metal, tapping and pouring metal into molds, knocking out hardened products from molds, chipping and cleaning products. In parallel, the preparation of molding and core earth, the preparation of molds and cores are carried out.

Metal is smelted in melting furnaces: pig iron is smelted in cupolas (a type of shaft furnace); steel is usually in electric arc furnaces; non-ferrous metals and their alloys are obtained by melting in electric furnaces.

In the technology of modern foundry production, approximately 2/3 of iron casting is earth casting, and only the rest is produced by more advanced technological methods, such as investment casting, shell mold casting, metal mold casting, pressure casting, centrifugal casting. .

The production of earth forms begins with the preparation of the molding sand. Its constituent materials: burnt earth (from used molds), sand, clay, coal. They are dried, sifted, mixed.

A model of the future casting is inserted into the metal frame (flask), and all the free space around it is tightly clogged with earth on molding machines. After removing the model, a molding cavity is formed, corresponding to the shape of the future workpiece. For casting hollow products, rods are placed in the flask, repeating the shape of the inner surface of the products. The rods are also produced from special earth mixtures with the addition of organic or synthetic binders and are dried in special ovens. The rods should be easily destroyed and removed from the cavities during subsequent cleaning of the casting.

In mechanized foundries, the finished mold is fed from the molding machine along the roller table to the casting conveyor, where it is poured with metal, which is delivered in ladles along the monorail. Further along the conveyor, the filled molds move to the place of knockout. During this period, solidification and partial cooling of the castings occur. Castings are released from molds, as a rule, mechanically, by shaking on knock-out vibrating gratings. At the same time, the earth falls under the grate, from where it is returned for processing.

After cooling, the castings are cleaned of burns, sagging, burrs, etc. For this, in most cases, manual mechanized pneumatic tools are used: chipper hammers, pneumatic grinders or emery wheels. Some parts, mostly small in size, are cleaned in upholstery (tumbling) drums. For cleaning, other methods are also used: shot blasting, electric spark, gas flame, electrohydraulic, etc.

Shell mold casting is more hygienic. At the same time, the consumption of molding materials and, consequently, dust is sharply reduced, high purity of castings is achieved, which makes it possible to practically eliminate vibration-hazardous operations for cutting off and cleaning castings.

The technology for manufacturing shell molds consists in applying a mixture of sand with pulverized bakelite or other binder directly to the model, after which the shells harden at temperatures up to 350 °C.

The use of multi-position semi-automatic machines and automatic machines for the manufacture of shell half-moulds reduces the share of manual labor to a minimum.

For the manufacture of molds and cores, a process is used based on the use of quick-drying molding compositions using liquid glass and blowing with carbon dioxide. With this method, sources of heat generation and air pollution by carbon monoxide and hydrocarbons are eliminated.

A promising method is the production of cores and molds from liquid self-hardening mixtures. The mixtures include ferrochromic slag, chromium oxides, urea-formaldehyde-furan additives, gypsum, nepheline slag in various proportions and combinations. The use of this technological process is accompanied by the release of toxic gases, but at the same time it allows to eliminate heat generation, noise, vibration and reduce dust formation.

Precision investment casting is made by making a stearin-paraffin model, which is first immersed in a special suspension of ethyl silicate and other refractory materials, then sprinkled with fine quartz sand, and dried in ammonia vapor. Next, the stearin-paraffin model is melted, the shell is placed in the flask, filled around with a mixture of chamotte clay and quartz sand and poured with metal. The quartz film after cooling the metal is separated using a solution of caustic soda. With this method, such harmful operations as land preparation, molding, knockout of flasks are excluded. The amount of work on cleaning the casting is drastically reduced.

Chill cast iron casting (in metal molds) also belongs to the progressive method, with it only the manufacture of rods remains unchanged.

Casting under pressure of non-ferrous metals and alloys is carried out on special casting machines-presses.

The radical improvement of working conditions in foundries is ensured by the maximum mechanization of all processes, the creation of efficient ventilation systems. The introduction of new progressive processes, as a rule, entails the emergence of new industrial hazards that require special attention from hygienists. At the same time, traditional methods of casting in earthen molds, which are the most widespread, continue to be the source of all the listed unfavorable factors of the production environment.

During the preparation of foundry earth and core sands, the molding of flasks, knocking out castings from molds and cleaning them, and repairing the refractory lining of smelting furnaces, workers are exposed to intense dust. The content of free silicon dioxide in dust reaches 20 - 30% or more. The highest concentrations of dust up to tens of milligrams per 1 m 3 can be observed during the preparation of the molding sand, knockout and cleaning of the casting.

The air of foundries is often polluted with various toxic substances. They are released during the melting and pouring of metal, the manufacture of rods, the drying of ladles and other processes. As a rule, carbon monoxide is detected, which is mainly formed during the combustion of fuel in a cupola furnace, the burnout of organic components from foundry earth and cores. During the operation of solid and liquid fuel stoves, sulfur dioxide can be released into the air of working rooms.

With the use of new chemical materials and methods for the production of molds and cores, the range of toxic substances in the air of foundry premises has significantly expanded.

The process of pouring metal into shell molds is accompanied by sublimation and pyrolysis of the binder. In this case, vapors of phenol and carbon monoxide are released, as well as degradation products in the form of acrolein, polycyclic aromatic hydrocarbons, including benzo(a)pyrene.

When casting molds are obtained using CO 2 - a process in foundry production - in case of violation of technological and sanitary conditions in the working area, the concentration of CO 2 increases by 3-5 times compared to the normal content of this gas in the air, which can have a very negative effect on the well-being of workers.

The use of chromium-containing additives and chromium oxides in the production of cores and molds from liquid self-hardening mixtures leads to the release of chromium compounds into the environment, which are known to have pronounced allergic properties. When casting on gasified polystyrene foam models, styrene and its degradation products can be released.

When melting and pouring alloyed steels, compounds of manganese, chromium, nickel, selenium, lead and other compounds can enter the air of melting shops, and when melting non-ferrous metals, compounds of copper, zinc, lead, magnesium, beryllium, etc.

meteorological conditions. The air temperature in conveyor foundries in a temperate climate on the hottest days can reach 35–38 °С at the workplaces of cupola workers, steelworkers, pourers, and 30–35 °С at the knockout and molding section. Infrared radiation at the workplaces of cupola workers and steelmakers at the time of metal release can reach 3.3 kW/m 2 .

High levels of radiant heat are recorded in the workplaces of pourers and beaters, regardless of ambient temperature air.

Vibration is one of the most unfavorable factors in foundry production. Moulders, casting trimmers and sanders are exposed to local vibration. Workers employed on knockout gratings and partly on mechanized molding are exposed to general vibration.

The greatest danger is represented by the operations of chipping large-sized castings. These works are performed in a forced working position, require significant physical effort and are performed at low air temperatures during the cold season, all these circumstances are aggravating the adverse effects of vibration. Vibration parameters, as a rule, significantly exceed the permissible levels in a wide spectral range. Cast cutters among patients with vibration disease constitute the main professional group both in absolute and relative terms. When cleaning small-scale castings on abrasive wheels, in order to increase the feed intensification, in some cases they press the product with a lever and support it with the upper part of the thigh. With this technique, vibration is transmitted not only to the hands, but also to the thigh and lower body, which leads to additional functional disorders.

Noise. The main sources of noise in foundries are molding, carried out by shaking the flasks, pneumatic tools used to blow molds and clean castings, emery machines, tumbling drums, knockout gratings. The noise intensity level can reach 100 - 110 dBA. The spectral composition is dominated by high-frequency noise. During electrohydraulic knockout of rods from castings at the moment of discharge, high-frequency impulse noise occurs with a level of 120 - 130 dBA. Reducing it to regulatory levels requires the implementation of a set of noise protection measures.

Wellness activities. Architectural and planning solutions should provide for the maximum separation of production areas (earth preparation, molding, melting and pouring, flask knockout, casting cleaning). This will prevent the spread of adverse factors in the production environment: dust, gases, excess heat, noise to adjacent workplaces. Premises of hot industries - melting and pouring of metal - must be equipped with aeration.

The enlargement and centralization of foundries and the construction of so-called centroliths contribute to a fundamental improvement in working conditions. At such large newly created enterprises, as well as reconstructed foundries, in-line casting methods, complex mechanization and automation of labor-intensive and harmful processes and operations are carried out. These include: automation of land preparation processes (grinding, dosing, mixing); the use of pneumatic transport for moving bulk materials; equipment for dusting units with exhaust ventilation; the use of automatic molding machines and knock-out gratings; introduction of electro-hydraulic knockout of cores, replacement of casting stumps by gas-plasma cutting, electric spark processing and other modern methods.

The introduction of progressive technological methods of casting - into shell molds, according to investment patterns, chill casting, injection molding, etc., contributes to the reduction of labor-intensive and harmful working conditions for cleaning castings.

Rationally organized ventilation contributes to the creation of the necessary parameters of the air environment. In areas with increased dust formation, local suctions are used, they are also effective in areas with gas emissions. An improvement in the composition of the air environment is facilitated by the transfer of melting furnaces to electric heating (instead of flame).

In areas without excessive dust emissions, general exchange supply and exhaust ventilation is organized. Workplaces at melting furnaces, at metal pouring, etc. are equipped with local supply ventilation - air showers.

When using casting methods in which molding materials contain harmful chemicals, or these substances are formed as a result of sublimation or destruction of chemical compounds, it is necessary to implement a system of special measures: the preparation of particularly aggressive mixtures should be carried out in special sealed installations, in isolated rooms, with full mechanization of all operations. Filling places must be equipped with effective local and general ventilation. Roller tables should be covered with special casings, along which the metal cooling in the molds moves, the casings are also equipped with a local exhaust. This achieves a reduction in air pollution and removal of excess heat, in addition, the casings prevent the spread of radiant heat. To protect against infrared radiation, other generally accepted measures are also used: thermal insulation of heating units; screen adaptation; coloring of radiation sources in light colors; mechanization of the processes of loading furnaces and sealing tapholes; the use of special tools with long handles: the use of overalls and eye protection (glasses, shields).

Protection of workers from harmful effects, vibration is carried out through the development and implementation of safer mechanized vibration tools; the use of vibration damping devices; systematic monitoring of technical condition tools, including bench tests of vibration parameters; compliance with the recommended work and rest regimes; carrying out preventive physiotherapeutic and other medical measures (UV irradiation, massage, hydroprocedures, vitaminization, etc.). Due to the fact that cooling contributes to the development of vibration disease, it is important that the rooms where work is done with hand-held power tools are heated, compressed air must be heated in cold weather.

To reduce noise levels and prevent its spread, noise absorption measures, noise insulation of equipment are used, or if it is not possible, fencing and sound insulation of the operator's workplace or control panel. Particularly noisy units that do not require constant monitoring, for example, tumbling drums for cleaning small castings, are installed outside the working premises.

FORGING AND PRESSING SHOPS

In the forging and pressing shops, metal preheated to a given temperature is processed by dynamic (forging, stamping) and static (pressing) pressure.

The metal is heated in flame or electric furnaces, processing - with the help of hammers, dies, presses.

Working conditions are determined by the design of furnaces, the type of fuel and the degree of mechanization of production processes. Forges are characterized by a heating microclimate. The amount of heat release varies considerably. In the warm season, the air temperature at the workplaces of blacksmiths can exceed the standard values ​​by 8–10 °C or more. The intensity of thermal radiation is higher for open furnaces, somewhat less for hammers. With improper placement of heating furnaces and hammers on the workshop area, extremely unfavorable situations can be created in which workers at hammers or presses are exposed to infrared radiation from almost all sides, so-called heat bags are created. In such cases, conditions arise that lead to an overstrain of the body's thermoregulation in workers. It should also be taken into account that the work of a blacksmith is classified as moderate or heavy.

The work is characterized, as a rule, by a high pace, since the metal is plastic only at a certain temperature, and this plasticity is lost as it cools.

Particularly unfavorable microclimatic conditions are created in cabins of overhead cranes that are not equipped with proper thermal insulation and air conditioning. So, with a two-row arrangement of equipment, when the cabins are located directly above the heating furnaces, the air temperature in the cabins reaches 40 ° C and above. With a single-row arrangement of equipment, the temperature in them usually does not exceed 37 ° C. Walls and floors in cabins can be heated up to 40 °C, and in some cases up to 50 °C, being secondary heat sources. Such temperature conditions, combined with limited air mobility, cause difficulties in heat transfer both by convection and radiation, which causes a sharp overstrain of the thermoregulation of the crane operators' organism, up to the occurrence of overheating.

During the operation of solid and liquid fuel stoves, the air in working rooms is often polluted with smoke and soot, carbon monoxide and sulfur dioxide, the concentrations of which, with insufficient or inefficient air exchange, may exceed permissible levels. Smoke and soot may contain benzo(a)pyrene.

Hammers and dies, when struck, generate impulse noise with an intensity of 995 - 125 dBA. The same machines create workplace vibration, which can also exceed acceptable levels. The intensity of noise and vibration is directly dependent on the power of the forging and pressing equipment and the architectural and construction features of the workshops.

Acoustic neuritis is the most common occupational disease among blacksmith workers.

Wellness activities. Architectural and planning solutions for forging and pressing shops should provide single-row placement of equipment, which improves the radiation situation and ensures good air exchange due to the rational organization of air exchange. The transition of furnaces from solid and liquid fuels to gas and electricity, the use of smokeless lubricants and the replacement of hot forging with cold wherever possible should be sought. Along with this, the entire arsenal of thermal protection means should be used to normalize the microclimate. Reducing heat generation is achieved by thermal insulation of the walls of furnaces. The best effect is achieved with water cooling of the casing and dampers of furnaces and the installation of water curtains at the loading openings and openings.

Workplaces of operators should be shielded from sources of heat radiation. The most effective screens are in the form of double-walled boxes with or without a heat carrier (water or air). It is obligatory to equip air showers as effective remedy heat transfer improvement. Air shower installations are used both stationary with preliminary treatment of supply air, and mobile.

Along with ensuring the natural removal of heat above the furnaces, it is necessary to equip local mechanical draft hoods. This achieves the removal of convection heat along with gases.

The prevention of overheating, the reduction and elimination of heavy manual labor is facilitated by the mechanization of labor-intensive processes: the use of manipulators, roller tables for supplying heated metal from the furnace to the forging equipment, trolleys on monorails, etc.

Noise and vibration reduction is achieved by installing forging and stamping presses on special vibration-isolated foundations. The equipment of soundproof casings for presses, lining of stamping areas with sound-absorbing materials reduces noise by 8-12 dB. Along with these measures, it is recommended to install noise-absorbing partitions and screens.

Workers must use antiphons such as VTsNIOT-1, VTsNIOT-2, etc. and earplugs.

It is expedient to equip oases and rest rooms with radiation cooling in forging and pressing shops. Water-spray showers have proven themselves well in workplaces.

To improve the microclimate in the cabins of electric overhead cranes, thermal insulation protection is equipped and local air conditioners are installed.

As personal protective equipment for workers from infrared radiation, it is necessary to use appropriate overalls and to protect the eyes - goggles with light filters coated with a reflective layer.

THERMAL SHOPS

Heat treatment is designed to give the metal certain physical and chemical properties - hardness, viscosity, elasticity, electrical conductivity, etc. - by heating to a given temperature (from 450 to 1300 ºC) and subsequent cooling in certain media. There are thermal hardening, tempering, languor, annealing of metal. In necessary cases, various chemical elements and compounds are additionally introduced into the surface layer of the metal: carbon (cementation), nitrogen (nitriding), cyanide compounds (cyanidation), etc.

Heating of workpieces is carried out in flame furnaces operating on gaseous, liquid or solid fuels and electric furnaces. For uniform heating, products can be placed in special baths with molten lead or salts of barium chloride, saltpeter.

Cementation is carried out by heating in charcoal with an admixture of carbonic soda or in baths with cyanide compounds; nitriding - in a jet of ammonia at a temperature of about 500 °C. The heat treatment of metal with high-frequency currents by using induction heating in a high-frequency electromagnetic field is widespread.

The most common method of heat treatment is immersion of products after heating in hardening baths with mineral oils.

The working conditions in thermal shops in terms of microclimate are in many respects close to those in forge shops. Due to the high concentration of heating equipment, the air temperature in the premises of thermal shops may exceed the established standards. Relative humidity is usually 30 - 60%. Radiant heat also reaches a high level, especially during the loading of the workpieces in the furnace and during unloading.

The air of the working area in thermal shops is polluted with various chemicals, the composition of which is determined by the production technology. When coal with a high sulfur content is used as a fuel, and high-sulfur fuel oil, the air environment is polluted with sulfur dioxide. Carbon monoxide from heating and hardening plants also enters the air, its concentration may periodically exceed the MPC.

Hardening in baths with mineral oils is accompanied by the release of hydrocarbon vapors and their pyrolysis products. With poor ventilation, the concentrations of these substances can be significant.

When carburizing products using sodium or potassium cyanide, as well as cyanidation in baths with molten cyanide salts, cyanides are released, however, with reliable operation of local exhaust ventilation concentrations of hydrogen cyanide and cyanide salts in the air of the working area usually do not exceed the maximum allowable.

Work on pig baths is accompanied by air pollution with lead fumes; lead is found in washes from the hands and on the overalls of firemen. Nitriding pollutes the air with ammonia.

The use of heat treatment of metals by high-frequency currents in the absence of reliable shielding leads to exposure of operators to high-frequency elm fields.

Wellness activities. Normalization of the microclimate is achieved by the rational organization of ventilation. Most in a simple way removal of large volumes of superheated air is the use of aeration lamps. If it is impossible to carry out aeration to remove excess heat, local natural exhaust ventilation is used in the form of umbrellas over heat sources and mines, as well as mechanical general exchange supply and exhaust ventilation.

As in other hot shops, in thermal production it is effective to use thermal insulation of heat sources, shielding workplaces, installing water curtains in the windows of heating furnaces, painting heating equipment in bright colors, etc.

Air showering contributes to the improvement of the heat exchange of workers, its organization at the workplaces of thermal operators is mandatory.

To prevent air pollution with harmful chemicals, it is necessary to cover hardening and other baths with a mandatory local exhaust ventilation device with air intakes such as air intakes. Exhaust air contaminated above the permissible levels with lead vapor, cyanide compounds and other harmful substances must be cleaned before it is released into the atmosphere.

A promising way to prevent air pollution of the working area and the surrounding atmosphere with vapors and products of thermal degradation of hydrocarbons is the replacement of mineral oils with aqueous solutions of non-toxic synthetic substances. Production tests of such substitutes give encouraging results. One of the effective ways of hygienic rationalization of the processes of heat treatment of products is the use of vacuum processes.

Automation and mechanization of processes is of great technical-economic and sanitary-hygienic importance.

At large machine-building enterprises, in conditions of mass production, continuous furnaces with pusher conveyor or other mechanisms operate. All main processes are automated: loading in the furnace, moving to hardening baths, unloading, washing, etc.

To protect the operators of high-frequency metal heating installations from the possible adverse effects of electromagnetic fields, radiation sources are shielded using a metal mesh or sheet metal.

MECHANICAL SHOPS

In machine shops, all types of cold metal processing are performed on machine tools, which, depending on the operations performed, are divided into those working with bladed (cutter, cutter, drill) and abrasive tools (grinding, grinding and polishing wheels). Electrochemical methods of metal processing and various types of plasma technology (cutting, spraying, etc.) are also widely used.

The mechanical shops of the machine-building and metal-working industries are among the main ones in terms of their technological significance and the number of workers employed in them.

The tools and methods of metal processing used determine the nature of labor and its sanitary and hygienic features.

The machine-tool fleet of machine-building enterprises is represented by a variety of equipment - from universal machines with manual control to automatic and semi-automatic machines. Machine tools with numerical control in combination with flexible automatic lines form the basis for the re-equipment and intensification of mechanical engineering.

In the process of metal processing, it is necessary to cool the cutting tool and the workpiece, and therefore they are abundantly wetted with cutting fluid (coolant).

Mineral oils, their emulsions, alkaline solutions, solutions of some synthetic substances are used as such liquids. To impart certain qualities, various additives (additives) are included in the coolant composition: sulfonates, nitrates, nitrites, molybdenum, chromium compounds, sulfur-containing compounds, triethanolamine, surfactants.

Emulsions are most widely used, which are a 3-10% aqueous solution of mineral oil, naphthenic and oleic acids and inorganic alkalis (soda ash), and some additives.

In the process of using cutting fluids, their initial composition may change due to contamination with metal waste, thermal degradation, volatilization of individual substances, and also partially microbiological transformations.

Working conditions in machine shops are directly dependent on the technological level of the equipment used. In workshops with outdated equipment, work is characterized by varying degrees of severity and intensity.

The content of aerosols of lubricating oils and coolants in the air of the working area and the products of their thermal destruction varies depending on the method of supply, thermal stability, processing mode, and the efficiency of sanitary devices. The most constant is the noise from working machines, often exceeding acceptable levels. Even when using the most modern machines equipped with shelters with ventilation suction, contamination of clothing and skin while adjusting and repairing equipment with oils and coolants is not excluded.

Coolants and lubricating oils, when inhaled, can cause an irritant effect on the mucous membranes of the upper respiratory tract.

With prolonged contact with coolant, oily folliculitis and oily acne may appear on the skin of workers, localized in places of the greatest pollution. Alkaline solutions and some additives included in the coolant can cause dermatitis. The risk of dermatitis increases when machining alloyed steels containing such strong allergens as chromium and nickel, which are able to dissolve in alkaline solutions.

The processes of abrasive metal processing (grinding, polishing, sharpening) are accompanied by the release of mineral-metal dust into the air. Its concentration depends on the type of abrasive tool, the nature of the metal being processed, the dry or wet processing method, and the efficiency of dust extraction devices. The ratio of mineral-metal components of the dust depends on the quality of the abrasive and the strength of the metal; usually 1 weight part of abrasive dust accounts for 40 - 45 parts of metal. Abrasive dust consists of corundum Al 2 O 3 or carborundum SiC. Free silicon dioxide SiO 2, which is part of the bundles, does not exceed 2 - 3.5%.

Thanks to dust suppression measures, and especially when correct operation local dust extraction ventilation, dust concentration is within acceptable limits. Dust pathology can manifest itself in the form of catarrh of the upper respiratory tract, dust bronchitis and pneumonia in workers with long experience.

Sources of noise in machine shops are electric motors, gears, impacts of workpieces on guide mechanisms, and the process of metal cutting itself.

To a large extent, the noise depends on the type of metal-cutting machine. The most intense noises are milling machines. In addition, the intensity of the noise depends on the model and condition of the equipment. For example, a semi-automatic milling machine (models 64-41B) and a CNC milling center (OTs-KS-500) create noise below 85 dBA, while PKOR-20 machines are sources of noise with an intensity level of up to 110 dBA with maximum energy in the frequency range 5000 - 8000 Hz.

Significant noise (up to 90 dBA) occurs during the operation of automatic turret lathes. High-frequency noise with an intensity of up to 95 - 98 dBA accompanies the work of grinding and sharpening machines.

Wellness activities. When working on universal machine equipment using coolants and technical lubricants (TS) preventive actions provide for: replacement of toxic fluids and lubricants less harmful to the health of workers; sanitary and technical measures that limit the ingress of aerosols into the air and contamination of the skin and clothing of machine operators, compliance with the rules for the preparation, storage, transportation and use of coolant and TS; systematic laboratory control over their composition and the degree of bacterial contamination.

The sanitary legislation provides for a toxicological assessment and preliminary hygienic testing of all new (or modified) compositions of cutting fluids and TS. Only after that they are allowed into commercial operation.

The reduction of direct contact between those working with coolant and TS should be carried out through the use of modern machines equipped with protective screens connected to exhaust ventilation and a lock that turns off the machine when the protective screen is raised.

Used working solutions are regularly filtered, cleaned and periodically (strictly on schedule) are replaced with fresh ones.

The quality of the coolant is periodically controlled by the factory laboratory; if it deviates from the specifications, the fluid must be replaced.

The basis for the immediate replacement of coolant and TS is the detection of chromium or nickel in working solutions. If it is necessary to protect the skin, workers are provided with overalls made of moleskin fabric and vinyl chloride and other coatings. Personal hygiene issues are important in the prevention of skin diseases: timely change of linen, washing in the shower, treatment of microtraumas. Fans, air ducts, dust-cleaning devices must meet the requirements set out in the chapter "Ventilation of industrial premises".

The use of the wet grinding method significantly reduces dust formation, but as studies have shown, the dust content of the air remains quite high, and this method of abrasive processing also requires a local exhaust ventilation device.

Measures to combat noise in machine shops should be carried out by reducing it at the source; installation of machines on vibration-isolating foundations; balancing of rotating mechanisms; soundproofing the noisiest units. Sound-absorbing screens and lining of fences with sound-absorbing materials significantly reduce noise. Do not neglect personal hearing protection.

To reduce the severity and intensity of labor, especially on universal equipment, it is necessary:

Improving the placement of controls, taking into account the anthropometric data of a person in order to ensure the optimal working posture;

Reducing the efforts applied to the governing bodies;

· maximum mechanization of processing processes;

Providing conditions for a short rest in a sitting position.

WELDING PRODUCTION

Welding production includes large group technological processes of connection, separation (cutting), surfacing, soldering, spraying, sintering, local processing of materials, etc. These processes are carried out using on-site processing of thermal, thermomechanical or electrical energy. The most widely used are thermal processes using the energy of chemical reactions (combustion of combustible gases in oxygen), electrical energy (electric arc, electroslag, plasma, electron beam processes, etc.), as well as the energy of sound and light (processes of ultrasonic, laser welding, cutting , hole punching, heat treatment, etc.). Thermomechanical welding uses heat and work of mechanical compression (gas-pressure, induction, contact, diffusion welding, etc.).

Sanitary and hygienic working conditions during welding are determined mainly by the peculiarity of technological processes performed using various energy sources, so we will briefly consider the most common of them.

Thermal class of welding processes. Arc welding. The most versatile and common source of heat used for fusion welding is the electric arc. Welding is carried out with consumable or non-consumable electrodes. To isolate the arc and molten metal from air, gas, gas-slag or slag protection is used. Inert gases (argon, helium) or carbon dioxide are used as gas protection.

Welding with a coated metal electrode is widely used. The coating contains substances necessary for stable arc burning, creation of gas and slag protection of metal from air, and for physical and metallurgical processing of liquid metal in order to improve its quality (ferroalloys). The composition of the coating includes ferroalloys (ferromanganese, ferrosicilium, ferrotitanium) and some other components.

Submerged arc welding is carried out using automatic and semi-automatic machines. This type of arc welding is characterized by the fact that the arc burns in a gas bubble, reliably protected from air by a layer of molten flux-slag and solid flux. The flux layer also protects the surrounding area from harmful arc radiation.

Electron beam welding. The essence of electron beam welding is to use the kinetic energy of electrons accelerated by an electric field with a high potential difference to heat and melt the metal. A device that produces a narrow focused electron beam with a high energy density is called an electron gun. Electron beam welding is usually carried out in a vacuum of 10 -2 - 10 -3 Pa.

Light beam welding. IN Lately In industry, the energy of a light beam, obtained using optical quantum generators (OQG) or lasers, is increasingly being used. The laser radiation is characterized by a number of unique properties: high monochromaticity, significant degree of coherence, big power and high orientation. In welding production, the most promising are gas lasers, which have sufficiently high power and efficiency. They are successfully used for welding and cutting metals. High thermal power density (above 108 - 109 W/m 2 ) with modern laser technology makes it possible not only to melt, but also to evaporate all known materials.

Plasma processing of materials. During plasma welding, cutting or spraying of materials, the source of heat is a plasma jet, which is a stream of ionized particles that have great energy. To obtain a plasma jet, special devices are used, called plasma torches or plasma torches. In plasma torches, an arc discharge of considerable length is used, burning in a relatively narrow water-cooled channel. Depending on the composition of the medium, the temperature of the gas discharge plasma in an arc stabilized by a water vortex is 20,000–30,000 °C.

2. Thermomechanical class of welding processes. The joining of metals by high-temperature heating and plastic deformation of the metal was the first type of welding that man created. This type was forge or hearth welding. In the future, the development of pressure welding followed the path of improving heating sources, methods of plastic deformation, methods of cleaning and protecting the surfaces to be joined.

Electric contact welding. Its variation is spot welding. In spot welding, the parts to be joined are clamped between the electrodes of the machine and a high current is passed through them, providing heating and melting of the metal. After the metal hardens under pressure, a weld point is formed, firmly connecting both parts.

High frequency welding. The welding method is based on high-frequency heating to welding temperatures of the surfaces to be joined, and compression of these surfaces. For welding with high frequency currents, 2 methods of energy transfer are used: contact and induction. With the contact method, a high-frequency current is supplied to the heated elements (usually radio frequencies above 60 kHz). Induction heating is carried out using a special device called an inductor.

Diffusion welding in vacuum. This method of welding is carried out due to the mutual diffusion of atoms of the contacting parts with a relatively long action of elevated temperature and slight plastic deformation. To protect the metal, as a rule, welding is carried out in a vacuum. Various energy sources are used to heat the parts to be joined, but the most widely used is induction heating with high-frequency currents.

3. Mechanical grade welding processes. Welding processes belonging to this class are performed without preheating the parts to be joined. The most common type of this class is cold welding. It is carried out with significant plastic deformation due to the high pressure of the joined metals, as a result of which an interatomic bond is established between them.

Ultrasonic welding is also carried out without preheating. The connection during ultrasonic welding occurs as a result of the combined effect on the parts of shearing high-frequency mechanical vibrations, accompanied by heating of the metal, and compressive pressure.

Sanitary and hygienic characteristics of working conditions. The considered welding methods differ sharply in their sanitary and hygienic characteristics. The most unfavorable sanitary and hygienic conditions are typical for the thermal class of technological processes performed in air directly in the worker's breathing zone, i.e., primarily for manual arc welding.

The main hazards of the arc welding process are welding aerosol containing dust, vapors and gases, such as fluorine compounds, carbon monoxide, nitrogen oxides, ozone, etc. UV radiation, splashes of molten metal and slag. The composition of the dust and gases generated during welding depends mainly on the composition of the electrode coatings. The basis of dust is iron oxides, and impurities are compounds of manganese, chromium, nickel, vanadium, molybdenum and other metals included in the welding wire, coating or molten metal.

The most harmful effect is exerted by manganese oxides and fluorine compounds. Their content is usually low compared to iron oxides, however, due to their toxicity, they are of decisive importance in choosing the type of electrodes and coatings. It is necessary to use electrodes with the lowest content of manganese and fluoride compounds.

All types of welding produce ozone and nitrogen oxides (mainly nitrogen oxide, and in some cases nitrogen dioxide). Incomplete combustion of the carbon contained in the metal produces carbon monoxide. In the arc zone, carbon monoxide is formed due to the dissociation of carbon dioxide, which is used as a shielding gas. Ozone, nitric oxide and carbon monoxide are highly toxic.

The dust formed during welding is highly dispersed, the number of particles with a diameter of less than 1 micron is 98 - 99%. Prolonged exposure to welding aerosol can cause pneumoconiosis in electric welders.

The electric arc belongs to high-temperature energy sources with a temperature of about 6000 ºC, therefore it is a source of radiant energy in a wide range (infrared, visible, ultraviolet).

The high brightness of the welding arc (up to 15,000 stilbs) can cause blinding and retinal damage; Intense UV radiation leads to acute occupational eye damage - photo- or electrophthalmia, and can also cause ultraviolet burns to unprotected skin.

Prolonged exposure to the radiant energy of welding arcs with insufficient eye protection can lead to the development of a chronic disease of the organ of vision - cataracts.

Significantly improve the working conditions of the welder automatic and semi-automatic submerged arc welding. In this case, the arc burns under a layer of flux and its harmful effect on the organs of vision is eliminated. In addition, the risk of burns from metal splashes is eliminated. However, the air environment is polluted by gases and dust particles, the composition and amount of which depend mainly on the composition of the fluxes used. The gross emission of dust with this method of welding is many times less than with manual welding.

Aerosol concentration in the welder's breathing zone is 5.1 - 12.2 mg/m 3 . The concentration of manganese oxides in the breathing zone of workers servicing the machines ranges from 0.11 to 0.7 mg/m 3 .

When welding with a non-consumable tungsten electrode in an argon environment, the main hazard is ozone, as well as the thermal effect of an open arc. In this case, the emission of electric welding aerosol and manganese oxides is small.

The most unfavorable sanitary and hygienic conditions occur during the spraying and cutting of metals by an electric arc method and using a plasma jet. These processes are accompanied by a strong gas contamination and dusting of the air environment, many times exceeding the maximum permissible values. The toxicity of harmful substances depends on the processed materials. During plasma spraying and metal cutting, noise, dust, gases, thermal and ultraviolet radiation are harmful factors. Noise during plasma processing occurs due to the passage of plasma at supersonic speed through a narrow hole in the torch nozzle and exceeds allowable norms. The total level of sound and ultrasonic pressure in the working area reaches 120 - 130 dB. Increased ultraviolet and infrared radiation, high-frequency noise and ultrasound, air pollution with aerosols require a set of protective measures during plasma processing, including sheltering the installations in fume hoods, the use of noise-attenuating attachments for plasma torches, the use of personal protective equipment for the eyes, hearing and face of the welder.

When working with lasers, the eyes and skin are most at risk. The laser beam has thermal, photochemical and mechanical effects on biological objects. The danger is not only the direct, but also the reflected laser beam. The danger is increased due to the fact that the laser radiation may be in an invisible area. In all cases, the trajectory of the laser beam must be inaccessible to workers. The hygienic advantage of laser welding is that, due to the high concentration of energy and the locality of heating, the amount of harmful substances released during laser welding is small. Even more favorable sanitary and hygienic conditions are typical for electron beam welding. Welding is carried out in vacuum in special chambers. Air is pumped out of the working chamber by vacuum pumps with its release outside the working room, so no pollution enters the room. As with laser welding, the danger to workers is the intense radiation of the molten metal, as well as the resulting X-ray radiation resulting from electron bombardment. The latter circumstance requires the creation of X-ray protection in electron-beam installations.

Thermomechanical and mechanical classes of technological processes in terms of sanitary and hygienic conditions are usually much better than thermal. In resistance welding, the welding current reaches tens of thousands of amperes, which creates powerful electromagnetic fields. High-frequency electric fields of high intensity are an unfavorable factor when welding with high-frequency currents. An effective reduction in the intensity of the high-frequency field is achieved by shielding high-frequency installations.

Vacuum diffusion welding has the most favorable hygienic conditions in this class, leaving no air pollution in the working areas.

Ultrasonic welding is characterized by the effect of ultrasonic vibrations on the human body.

Of the occupational diseases in welders, pneumoconiosis of the type of siderosis is possible. It proceeds in a relatively favorable form of diffuse-sclerotic changes. Inhalation of welding fumes and irritating gases causes chronic occupational bronchitis. Chromium compounds can cause asthmatic bronchitis lesions of the nasal mucosa and respiratory tract.

The phenomena of manganese intoxication among welders are rarely recorded and usually in the form of mild forms.

Plasma operators (which generate extremely loud noise) may develop occupational cochlear neuritis.

Preventive actions. A radical way to optimize the working conditions of welders is the currently intensively implemented automation of welding operations and the use of robotics. The creation and maintenance of normal sanitary and hygienic working conditions in the welding industry is achieved by using a system of preventive measures.

The removal of welding dust and gases from the working room is carried out primarily with the help of local ventilation for stationary and non-stationary welding posts. Due to the fact that the efficiency of local ventilation is less than 100%, assembly and welding shops must also be equipped with general supply and exhaust ventilation. Mechanical exhaust ventilation from the upper area is provided by axial exhaust fans. To compensate for the air removed by exhaust ventilation, its organized inflow must be provided.

Noise control is carried out both during the creation of equipment and when it is placed in industrial premises. Where it is impossible to reduce the level of sound power, for example, in plasma processes, personal protective equipment is used - earmuffs or earplugs. It is necessary to achieve full automation of such processes with the removal of operators from the noise zone.

Personal protective equipment is also used to protect the respiratory system. With a small concentration of gases in the air, you can use respirators. At high concentrations of hazards (when welding in wells, tanks, compartments of vessels, and other closed volumes), it is necessary to use hose gas masks with forced air supply.

In recent years, methods have been developed and received a high hygienic assessment of methods for supplying fresh air to the welder's breathing zone - directly under the shield.

To protect the surroundings from the radiant energy of welding arcs, permanent welding posts are equipped - booths or screens are installed.

To protect the eyes and face of welders, special shields and masks with protective light filters from the blinding visible part of the radiation spectrum, ultraviolet and infrared rays are used.

Personal protective equipment includes overalls and special footwear for welders.

Particular attention is paid to the means of protection against radiation, the harmful effects of which depend on the power, dose, type of radiation, distance from sources, etc., therefore, strict control of radiation is also important.

An important place in ensuring the health of workers in the welding industry is also occupied by medical and preventive measures. These include mandatory preliminary and periodic medical examinations, the terms and scope of which are regulated by Order No. 90 of the Ministry of Health of the Russian Federation. It is advisable for welders to periodically stay in sanatoriums with courses of special physiotherapy procedures.

GALVANIC SHOPS

The surfaces of many products of the engineering industry are coated with other metals (nickel, copper, zinc, chromium, cadmium, tin, silver, gold, etc.) to protect against corrosion, ensure strength and for decorative purposes. One of the most common methods of metal plating is electroplating. The essence of this method is to deposit a thin layer of protective metal on the surface of a metal product from an electrolyte solution by passing a direct electric current.

This process is carried out in special galvanic baths filled with aqueous solutions of acidic salts (nickel sulfate, copper sulfate, zinc sulfate) or alkaline complex salts (cyanide compounds of zinc, copper, cadmium, aluminum, silver).

The coated product is placed in the bath, which serves as a cathode, the second electrode (anode) is a carbon or metal rod. As a result of the dissociation of the electrolyte, metal ions are deposited on the product (cathode). In this case, gas bubbles (hydrogen, oxygen, etc.) are released from the surface of the liquid, which carry away the electrolyte in the form of fog.

The surface of parts before coating is subjected to mechanical, chemical or chemical-mechanical treatment. Machining includes grinding and polishing, ultrasonic cleaning; chemical treatment consists in pickling and degreasing with strong inorganic acids (hydrochloric, nitric, sulfuric) and organic solvents (gasoline, trichlorethylene), etc.

The final stage of galvanic coatings is, as a rule, polishing of products on machines with felt (with abrasive knurling), cloth wheels on machines with an endless abrasive belt using special polishing pastes.

The working conditions of electroplating workers are characterized primarily by constant contact with a variety of chemical compounds.

Contact with concentrated acids and alkalis on the skin and eyes can cause chemical burns.

Vapors and mists of many chemical compounds (ammonia, nitrogen oxides, hydrogen chloride, sulfuric acid, etc.) have an irritating effect on the upper respiratory tract.

Gasoline, chloroethane and other substances used for degreasing parts are also sources of air pollution. Of particular danger is direct contact with the skin and the release of nickel and chromium compounds into the air of the working area. Possessing an extremely pronounced allergenic effect, these substances cause professional skin lesions such as eczema, dermatitis, and chromium ulcers. Once having arisen, these diseases are relapsing in nature, even with the slightest contact with the substances in question.

Those working on chrome baths may experience damage to the nasal mucosa, which, under the action of insignificant concentrations of chromium, manifests itself in the form of irritation of the mucous membrane, runny nose, small nosebleeds; under the action of high concentrations, necrosis of individual sections of the mucosa, its ulceration, up to the perforation of the cartilaginous part of the nasal septum, may occur. Due to the improvement of working conditions and due to periodic medical examinations, cases of perforation of the nasal septum are not currently observed.

Hydrogen cyanide poisoning in electroplating shops is a potential possibility from accidental mixing of cyanide electrolytes and strong acids.

When grinding and polishing parts on stationary machines with manual feeding of products, it is possible for the workers of this professional group to develop a vibrational pathology caused by local vibration.

Wellness activities. Of paramount importance in optimizing the working conditions of electroplaters belongs to the automation, mechanization of production processes and their remote control, which makes it possible to exclude the operator's contact with dangerous and harmful production factors.

In order to localize and remove harmful chemicals released from the surface of the liquids of galvanic baths, they must be equipped with local exhaust ventilation such as side suctions. Depending on the width of the bathtub, single-sided, double-sided suctions and double-sided suctions with blowing are installed. With the correct design and operation of local exhaust ventilation, a good hygienic effect is ensured.

In order to prevent the formation and release of hydrogen cyanide as a result of the contact of cyanide salts with strong acids and alkalis, cyanide baths should be installed in separate rooms or remote areas. Joint descent of cyanide and acidic solutions into the sewer is strictly not allowed.

Cyanide and acid baths should be equipped with separate exhaust ventilation systems to prevent the formation of hydrogen cyanide in exhaust systems. The powerful extraction of galvanic baths must be compensated by an organized inflow.

To reduce electrolyte carryover and the removal of harmful gases and vapors from the surface of electroplating and pickling baths, various additives or protective liquids are used, for example, kerosene “pillows” or plastic balls.

Mechanization and rationalization of technological processes play a decisive role in the prevention of skin diseases of workers in electroplating shops. Currently, many enterprises are successfully replacing manual methods of work with mechanized installations during degreasing, pickling, galvanization and washing. The overalls of galvanizers should consist of boots, rubberized aprons, mittens or gloves. If necessary, use glasses and filtering gas masks.

After work, the skin of the hands must be treated with indifferent ointments and creams.

When grinding and polishing products, it is necessary to carry out health-improving measures aimed at preventing dust pathology, vibration disease and pathology of hands from overvoltage. Grinding wheels are equipped with local exhaust with suction in the form of protective dust-removing casings. Fine balancing of polishing machines is necessary to reduce chipping and vibration. The processing of products on polishing machines with manual feed must be replaced by mechanized polishing methods.

It is necessary to strictly observe sanitary rules to prevent the harmful effects of contact ultrasound in the case of using ultrasonic units for cleaning parts.

An important role in maintaining the health of galvanizers belongs to preliminary and periodic medical examinations.

The main shops of machine-building enterprises are preparatory, or "hot" shops (foundry, forging, stamping, thermal) and "cold" (mechanical, mechanical assembly). The "cold" ones include welding production, metal coating shops.

Depending on the type and purpose of production, certain technological processes may be of particular importance, for example, in shipbuilding - electric welding operations; in aircraft construction - riveting; at factories of heavy and transport engineering, automobile and tractor factories - foundries and forge shops, etc.

Foundry

Among metalworking processes, in terms of a variety of operations and working conditions, foundry production remains one of the most complex and laborious.

The technological process of foundry production consists in obtaining products by pouring metal into non-permanent forms (destroying mainly earth) or into permanent forms from metal (chill casting) or other materials.

According to the type of metal, iron, steel, non-ferrous castings are distinguished.

The main foundry processes are: preparation of charge materials for melting, loading into furnaces, metal melting; release and pouring of metal into molds; knocking out hardened products from molds; trimming and cleaning products. In parallel, the preparation of molding and core soil, the preparation of molds and cores are carried out. Metal smelting is carried out in melting furnaces: cast iron is smelted in cupolas (a type of shaft furnace); steel is usually smelted in electric arc furnaces; non-ferrous metals and their alloys are obtained by melting in electric furnaces. During the preparation of foundry earth and core sands, the formation of flasks, the vibrating of castings from molds and cleaning, the repair of the refractory masonry of smelting furnaces, workers are exposed to intense dust. The content of free silicon dioxide in the dust reaches 20-30% or more. The highest concentrations of dust (up to tens of milligrams per 1 m 3) can be observed during the preparation of the mixture, vibrating and cleaning the casting.

The air of foundries is often polluted with various toxic substances. They are released during the melting and pouring of metal, the manufacture of rods, the drying of ladles and during other processes. As a rule, carbon monoxide may appear, mainly formed during the combustion of fuel in a cupola, burnout of organic components from the molding earth and cores. During the operation of furnaces on solid and liquid fuels, sulfur dioxide, ammonia, benzene can be released into the air of working rooms.

With the use of new chemical materials and means for the production of molds and cores, the range of toxic substances in the air of foundry premises has significantly expanded.

The process of pouring metal into shell molds is accompanied by sublimation and pyrolysis of the fixative. In this case, vapors of phenol and carbon monoxide are released, as well as degradation products in the form of acrolein, polycyclic aromatic hydrocarbons, including benzpyrene.

When casting molds are obtained using CO2 - a process in foundry production - in case of violation of technological and sanitary and hygienic conditions in the working area, the concentration of CO2 increases by 8-5 times compared to the normal content of this gas in the air, which can already adversely affect the well-being of workers .

The use of additives containing chromium and chromium oxides in the production of cores and molds from liquid self-hard mixtures leads to the release of chromium compounds into the environment, which are known to have pronounced allergic properties. When casting on gasified polystyrene foam models, styrene and its degradation products can be released.

Forging and pressing and thermal shops

Technological processes in such workshops are characterized by the presence in the air of the working area of ​​carbon monoxide, nitrogen oxides, dust, oil vapor, hydrogen cyanide, etc. Heat treatment is designed to provide the metal with certain physical and chemical properties - hardness, viscosity, elasticity, electrical conductivity, etc. . - by heating to a predetermined temperature (from 450 to 1300ºС) and subsequent cooling in certain environments. There are thermal hardening, tempering, languor, annealing of metal. In necessary cases, various chemical elements and compounds are additionally introduced into the surface layer of the metal: carbon (cementation), cyanide compounds (cyanidation), nitrogen (nitriding), etc.

Heating of blanks is carried out in flame furnaces operating on gaseous, liquid or solid fuels, and in electric furnaces. For uniform heating, products can be placed in special baths with molten lead, barium chloride salts, saltpeter. Cementation is carried out by heating in charcoal with an admixture of carbonic soda or in baths with cyanide compounds; nitriding - in a stream of ammonia at a temperature of about 500 ° C. Heat treatment of metal with high-frequency currents by applying induction heating in a high-frequency electromagnetic field is quite common.

The most common means of heat treatment is immersion of products after heating in hardening baths with mineral oils.

The air of the working area in thermal shops is polluted with various chemicals, the composition of which is determined by the production technology. When coal with a high sulfur content and high-sulfur fuel oil is used as a fuel, the air environment is saturated with sulfur dioxide. Carbon monoxide from heating and hardening plants also enters the air, its concentration may periodically exceed the MPC.

Hardening in baths with mineral oils is accompanied by the release of hydrocarbon vapors and their pyrolysis products. With poor ventilation, the concentrations of these substances can be significant.

During cementation of products using sodium or potassium cyanide, as well as during cyanidation in baths with molten cyanide salts, cyanides are released, however, with reliable operation of local exhaust ventilation, the concentrations of hydrogen cyanide and cyanide salts in the air of the working area usually do not exceed the maximum allowable.

Work on lead baths is accompanied by air pollution with lead fumes; lead ends up in hand washouts and on overalls The hardener.

Nitriding pollutes the air with ammonia.

The use of heat treatment of metals by high frequency currents in the absence of reliable shielding leads to exposure of operators to high-frequency electromagnetic fields.

Mechanical and mechanical assembly shops. Technological processes in these workshops are sources of mists, emulsions, oils, fine abrasive dust in the areas of grinding and polishing, gasoline and ethanol vapors in the areas of washing and degreasing parts.

In mechanical shops, all types of cold metal processing are performed on machine tools. In the process of metal processing, it is necessary to cool the cutting tool and the workpiece, and therefore they are densely wetted with cutting fluid (coolant). Such liquids are mineral oils, their emulsions, alkaline solutions of some synthetic substances. To provide certain qualities, various additives (additives) are included in the coolant composition: sulfonates, nitrates, nitrites, molybdenum, chromium compounds, sulfur-containing compounds, triethanolamine, surfactants.

The most widely used are emulsions, which are a 3-10% aqueous solution of mineral oil, naphthenic and oleic acids and inorganic alkalis (soda ash), some additives.

During the use of cutting fluids, their original composition may change due to contamination with metal waste, thermal degradation, the disappearance of certain substances, and also partially as a result of microbiological transformations.

Coolants and lubricants, if inhaled, can cause irritation of the mucous membranes of the upper respiratory tract. Alkaline solutions and some additives that are part of the coolant can cause dermatitis. The risk of dermatitis increases with the machining of alloyed steels containing such strong allergens as chromium and nickel, which are able to dissolve in alkaline environments.

The processes of abrasive metal processing (grinding, polishing, sharpening) are accompanied by the release of mineral-metal dust into the air. Its concentration depends on the type of abrasive tool, the nature of the metal being processed, the dry or wet processing method, and the efficiency of dust extraction devices. The ratio of mineral-metal components of the dust depends on the quality of the abrasive and the strength of the metal; usually 40-45 parts of metal are accounted for one weight part of abrasive dust. Abrasive dust consists of Al2O3 corundum or SiC carborundum. Free silicon dioxide SiO2, which is part of the compounds, does not exceed 2-8.5%.

With proper operation of local dust extraction ventilation, dust concentrations can be kept within acceptable limits. Dust diseases are manifested in the form of catarrhs ​​of the upper respiratory tract, dust bronchitis and pneumonia in workers of machine shops with a long experience.

Welding production. The technological processes of such production include a large group of processes of connection, separation (cutting), surfacing, spraying, sintering, soldering, local processing, etc. These processes are carried out using thermal, thermomechanical or electrical energy processing on site. The most widely used are thermal processes using the energy of chemical reactions (combustion of combustible gases in oxygen), electrical energy (electric arc, electroslag, plasma, electron beam processes, etc.), as well as the energy of sound and light (processes of ultrasonic, laser welding, cutting , hole punching, heat treatment, etc.). In thermomechanical welding, hot mechanical compression is used (gas pressure induction, contact, diffuse welding, etc.).

The main harmful factors in the arc welding process are welding aerosol containing dust, vapors and gases (for example, fluorine compounds, carbon monoxide, nitrogen oxides, ozone, etc.); UV radiation; splashes of molten metal and slag. The composition of dust and gases that are formed during welding depends mainly on the composition of the electrode coatings. The basis of dust is iron oxides, and impurities are compounds of manganese, chromium, nickel, vanadium, molybdenum and other metals included in the welding wire, coatings or molten metal.

Manganese oxides and fluorine compounds have the most harmful effect, their content is, of course, small compared to iron oxides, but due to their toxicity, they are of decisive importance when choosing the type of electrodes and coatings. It is necessary to use electrodes with the lowest content of manganese and fluoride compounds.

All types of welding produce ozone and nitrogen oxides (mainly nitrogen oxide, and in some cases nitrogen dioxide). With incomplete combustion of the carbon contained in the metal, carbon monoxide is formed. In the arc zone, carbon monoxide appears due to the dissociation of carbon dioxide used as a protective gas. Ozone, nitric oxide and carbon monoxide are highly toxic.

The dust generated during welding is highly dispersed, the number of particles with a diameter of less than 1 micron is 98-99%. Prolonged exposure to welding aerosol can cause pneumoconiosis in electric welders.

The concentration of aerosol in the breathing zone of a welder is 5.1-12.2 mg/m3. The concentration of manganese oxides in the breathing zone of workers servicing automatic machines ranges from 0.11 to 0.7 mg/m3.

When welding with a tungsten electrode, it melts in an argon environment, the main harmful factors are ozone, as well as the thermal effect of an open arc. In this case, the emission of electric welding aerosol and manganese oxides is insignificant.

The most unfavorable sanitary and hygienic conditions occur during the spraying and cutting of metals by an electric arc method and using a plasma jet. These processes are accompanied by strong gas contamination and pollination of the air environment, many times exceeding the maximum permissible values. The toxicity of harmful substances depends on the processed materials. In plasma spraying and metal cutting, harmful factors are dust, gases, thermal and ultraviolet radiation.

Galvanic shops. Technological processes of electroplating shops are sources of release of toxic substances into the air of the working area.

The surfaces of many products of the engineering industry are coated with other metals (nickel, copper, zinc, chromium, cadmium, tin, silver, gold, etc.) to protect against corrosion, ensure strength and for decorative purposes. One of the most common methods of metal plating is electroplating. The essence of this method lies in the deposition on the surface of a metal product of a thin layer of protective metal from an electrolyte solution by passing direct current. This process is carried out in special galvanic baths filled with aqueous solutions of acidic salts (nickel sulphate, copper sulphate, zinc sulphate) or alkali complex salts (cyanide compounds of zinc, copper, cadmium, aluminum, silver).

The product to be processed (coated) and which serves as a cathode is placed in the bath, the second electrode (anode) is a carbon or metal rod. As a result of the dissociation of the electrolyte, metal ions are deposited on the product (cathode). In this case, gas bubbles (hydrogen, oxygen, etc.) are released from the surface of the liquid, which carry the electrolyte in the form of a mist.

The surface of parts before coating is subjected to mechanical, chemical or chemical-mechanical treatment. TO machining belong grinding and polishing, cleaning with ultrasound; chemical treatment consists in digestion and degreasing with the help of strong inorganic acids (hydrochloric, nitric, sulfuric) and organic solvents (gasoline, trichlorethylene), etc. The final stage of electroplating is, as a rule, polishing products on machines with felt (with abrasive knurling) or fabric wheels, on machines with an endless abrasive belt using special polishing pastes.

The working conditions of electroplating workers are characterized primarily by constant contact with various chemical compounds. Contact with concentrated acids and alkalis on the skin and eyes can cause chemical burns. Vapors and mists of many chemical compounds (ammonia, nitrogen oxides, hydrogen chloride, sulfuric acid, etc.) irritate the upper respiratory tract. Gasoline, dichloroethane and other substances used for degreasing parts are also sources of air pollution in industrial premises.

Hydrogen cyanide poisoning in electroplating shops is potentially possible from accidental mixing of cyanide electrolytes and strong acids.

Preventive and health measures. Architectural and planning measures should provide for the maximum resolution of forage areas. This will prevent the spread of adverse factors in the working environment: dust, toxic gases and substances.

The consolidation and centralization of various industries in engineering (for example, foundries) contributes to a radical improvement in working conditions. At such large newly created enterprises, as well as reconstructed foundries, in-line casting methods, complex mechanization and automation of labor-intensive and harmful processes and operations are being carried out. Preventive and health measures include automation of land preparation processes (grinding, dosing, mixing), the use of pneumatic transport to move bulk materials; equipment of nodes where dust is formed, exhaust ventilation; the use of automatic molding machines and stuffed gratings; introduction of electro-hydraulic knockout of cores, replacement of casting stumps by gas-plasma cutting, electric spark processing and other modern methods.

The reduction of labor-intensive and harmful working conditions for cleaning castings is facilitated by the introduction of advanced technological methods of casting - into shell molds, investment models, chill casting, injection molding, etc.

Rationally organized ventilation contributes to the creation of the necessary parameters of the air environment. Local suctions are used in high sawn areas and are also effective in outgassing areas. The composition of the air environment improves the transfer of melting furnaces to electric heating (instead of flame).

In areas without excessive dust emission, general exchange supply and exhaust ventilation is organized. Workplaces near melting furnaces, metal pouring, etc. equipped with local supply ventilation - air showers.

When using casting methods in which molding materials contain harmful chemicals or substances are formed as a result of sublimation or destruction of chemical compounds, it is necessary to carry out a system of special measures: the preparation of particularly aggressive mixtures should be carried out in special sealed installations, in isolated rooms, with full mechanization all operations; pouring places must be equipped with effective local and general ventilation, also used to remove welding dust, harmful substances and gases from the working room, where various types of welding processes are performed.

Of paramount importance in optimizing the working conditions of electroplaters belongs to the automation, mechanization of production processes and their remote control, which makes it possible to exclude the operator's contact with dangerous and harmful production factors. In order to localize and remove harmful substances released from the surface of liquids in galvanic baths, the latter must be equipped with local exhaust ventilation such as side suctions. Depending on the width of the bathtub, single, double-sided suctions and double-sided suctions with blowing are arranged. With the correct design and operation of local exhaust ventilation, a positive hygienic effect is ensured. To prevent the formation and release of hydrogen cyanide as a result of the contact of cyanide salts with strong acids and alkalis, cyanide baths must be installed in separate rooms or at remote locations. Categorically not allowed joint descent of cyanide and acidic solutions into the sewer. Cyanic and acid baths should be equipped with separate exhaust ventilation systems to prevent the formation of hydrogen cyanide in exhaust installations. The powerful extraction of galvanic baths must be compensated by an organized inflow.

IN blacksmith shops various kinds of products and semi-finished products are obtained from metal ingots. To do this, metal ingots are preheated in flame and electric furnaces and subjected to dynamic (forging, stamping) or static (pressing) pressure treatment.

Working conditions in blacksmith shops. The processes of heating the metal and its subsequent processing are accompanied by the release of more or less significant amounts of heat into the air of the forges and the impact on the workers of radiant heat. There is also indoor air pollution by products of incomplete combustion of fuel and burning of lubricating oils - carbon monoxide, sulfur dioxide, soot and smoke.

Significant emissions of sulphurous anhydride observed when used for heating and thermal furnaces as a fuel of raw gas obtained from polysulphurous oils. Widely used in recent years for the same purposes, heavy fuel oils (grade 100), if they are not completely freed from water and insufficiently heated and sprayed, form a highly smoky flame during combustion. In these cases, as a rule, it is knocked out of the furnaces, sharp pollution of the air and glazing with smoke and soot.
In the scrapings of this soot 3-4-benzpyrene, which is known to have pronounced carcinogenic properties, was found qualitatively and quantitatively from glazing and extraction with dichloroethane.

Value heat dissipation entering the forge premises depends on the nature of the technological process and the organization of production processes. If heat and heated gases are removed from the furnaces by means of special smoke exhaust devices, then more than 75% of the amount of heat generated during fuel combustion can be removed to the outside atmosphere. On the contrary, in those forges where all the heat from the furnaces enters the workshop, the absolute value of heat release can reach tens of millions of calories per hour, and the heat load per 1 m3 of the room, the so-called specific heat load, can be 200-250 kcal / hour.

So big heat release is accompanied a significant increase in air temperature in the working area of ​​forging shops, which often reaches 34-36 °, and in unimproved forges, with a close arrangement of equipment and poorly organized transport from the shop for still hot forgings, 40 ° and even 45 ° at a relative humidity of 25-30% . Along with unfavorable temperature conditions, those working in blacksmith shops (are exposed to radiant heat from heated surfaces of furnaces and especially from steel forgings, which are heated to a temperature of 760-1100 °.

Intensity exposure in the workplace stampers varies within a fairly wide range: when stamping with a large hammer (2.5 tons) - 1.3-4 cal / cm2 * min .; when stamping at a small hammer (0.5 t) - 1-3.5 cal / cm2 * min .; with an open opening of the heating treatment - 7-10 cal / cm2 * min .; when carrying forgings from the furnace to the hammer - 4-6 cal/cm2-min.; at a distance of 0.5 m from the products folded and cooling in the workshop, depending on the duration of cooling, - 0.5-6 cal / cm2 * min.

pollution air blacksmith shops with carbon monoxide and sulfur dioxide, as a rule, is small, especially in modern blacksmith shops equipped with aeration devices and rational smoke exhaust devices from furnaces and furnaces.

Thus, based on a large number of analyzes air in the forging and pressing shops of the Novo-Kramatorsky plant and Uralmashzavod, carried out in 1955-1956. in the cold and warm periods of the year, carbon monoxide at the Novo-Kramatorsk plant in 60-68.1% of all analyzes was not detected at all and in 31.9-40% of all samples its concentration did not reach the maximum allowable. Only in the transitional period of the year at the same plant, carbon monoxide concentrations within the limits not exceeding the norms were observed in 83.3% of all samples and were not detected in 16.7% of the samples. Approximately the same ratio of samples with negative and positive results (62.2% negative and 31.8% positive) was observed in the forging and pressing shop of Uralmashzavod.

Sour gas concentrations at both plants in the warm and cold periods of the year, they averaged only 0.002-0.003 mg/l. They become significant and exceed the maximum allowable when using high-sulfur fuel oils or the gas obtained from them as fuel without cleaning the latter from sulfur compounds.

The work of blacksmiths, punchers and pressers under conditions high temperature air and significant exposure intensity is often accompanied by an increase, an increase in heart rate and respiration, a decrease in maximum blood pressure by 5-15 mm and a negative water-salt balance. To restore the normal activity of the body, sometimes a 15-30-minute rest is required after intense physical labor, in particular when working on forging and upsetting machines.

IN blacksmith shops the level of occupational injuries is quite high, averaging up to 20% of all morbidity with loss of ability to work. It is almost 1.5-2 times higher than at the enterprises of the machine-building industry as a whole. Among the injuries in blacksmith shops, a higher proportion of burns, reaching 11-15% of all types of injuries, draws attention. A particular danger of injury is the flying off of scale (iron oxides), as well as larger particles of metal and various objects, which is the cause of injury in hammerers in 31% of cases, and in blacksmiths in 43%. A relatively large number of injuries in forge shops occur when moving materials and products using various vehicles and manually.

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Subject: 1. AboutGENERAL DESCRIPTION OF WORKING CONDITIONS IN THE INDUSTRY

Working conditions at workplaces in mechanical engineering are determined by harmful and dangerous production factors that depend on the materials used, technological processes, and equipment.

Foundry characterized by increased dust content, excess heat, increased noise level, vibration, electromagnetic radiation, the presence of moving machines and mechanisms. When cleaning castings, dust is released, which contains more than 90% silicon dioxide, and when knocking out castings - about 99%. When melting alloyed steels and non-ferrous metals, condensation aerosols of oxides of manganese, zinc, vanadium, nickel and other materials can be released into the air of the working area. Sources of carbon monoxide release are cupolas and other melting units, drying furnaces.

The intensity of the heat flow at a number of workplaces reaches high values ​​(manual loading of the cupola furnace - 0.5-2.1 kW / m 2; workplaces at electric furnaces, at the loading openings of kilns - 1.65-3.15; work of a beater on a vibrator for knocking out rods - 0.7-1.05 kW / m 2; workplace crane operator - 0.21 kW / m 2).

The main sources of danger electric shock in foundries are: electric furnaces, machines and mechanisms with electric drive (conveyors, handling equipment). Applied electrical equipment - mainly with voltage up to 1000V, when using electrothermal installations - above 1000V.

Foundry shops are equipped with transport and lifting mechanisms, machines for the preparation of molding and core mixtures and compositions, as well as molds and cores, devices for knocking out castings. Performing any of the operations on the specified equipment is associated with the risk of injury to the operating personnel due to the presence of hazardous zones in machines and mechanisms.

One of the main means of protection against heat flow during melting, transportation and pouring of metal is the thermal insulation of melting and heating furnaces, metal tanks. Thermal protection devices are used to protect workers.

To remove heat from the room, as well as reduce the concentration of dust and gases in the working area, it is necessary to use aeration to the maximum in all production rooms of foundries. The amount of air entering for these purposes through openings in the walls and removed through the aeration lights is calculated by the formula (m 3 / h).

Where l- coefficient taking into account the height of the supply openings from the floor.

Distance to the opening axis, m2345

Coefficient, l 1,041,11,21,35

k- coefficient calculated by the formula:

Where t out.- the temperature of the exhaust air.

The values ​​of the coefficient k depending on the ratio f/ F(the area occupied by equipment that generates heat, f, m 2 and workshop area F, m 2 , the following:

Attitude f/ F 0,10,20,30,40,50,6

Coefficient k 0,250,450,620,680,830,87

G - heat release in the room, W;

G 1 - heat loss by external fences within the working area, W;

t r.z. - air temperature in the working area, 0 С;

t n - design temperature outdoor air, 0 C.

The efficiency of mechanical supply and exhaust ventilation depends on the placement of ventilation devices in the volume of the building. To localize harmful production factors (gases, vapors, dust, heat, moisture) at the sources of their formation, it is necessary to provide local exhausts: closed receivers, onboard exhausts, exhaust hoods, panels, dust-removing covers, etc. The air flow through these structures is determined by formula (m 3 / s):

Where F- area of ​​openings through which air is sucked in, m 2;

v 1 - air speed in openings, m/s.

The air speed in the openings for the localization of vapors and gases is taken as follows (m/s): when sucking non-toxic substances (heat, moisture) 0.15 - 1.25.

Forging and pressing production.

Sanitary and hygienic working conditions in the forging and pressing shops are characterized by the presence of harmful toxic substances in the air of the production premises: oil aerosol formed during the lubrication of the stamp, and products of combustion of lubricants; sulfur dioxide, carbon monoxide, hydrogen sulfide.

The concentration of dust-like particles, scale and graphite, blown off by compressed air from the surface of dies, dies, forgings, in the air of the working area is 3.9-4.1 mg/m 3 , behind presses can reach 22-138 mg/m 3 (in the absence local suctions).

The main unfavorable factors in the forging and pressing shops are high temperature (up to 34-36 0 C), intense infrared radiation, harmful toxic emissions, vibration, and noise.

Forging and pressing shops are characterized by significant releases of heat transmitted by radiation and convection.

The intensity of the heat flow at heating furnaces, presses and hammers is 1.4-2.1 kW / m 2, at the places of storage of blanks, control panels 1-1.95 kW / m 2.

Forging and pressing shops are characterized by increased noise (forging hammer - f = 1000 Hz L - 121 dB; crank press L - 105 dB; edger, L 3 = 112 dB) and vibrations. The vibration amplitude of the hammer head reaches 7-8 mm, the hammer foundation 0.56-0.08 mm. Hammer foundations must be isolated from vibration by means of springs and rubber or a set of springs.

Exposure intensity at workplaces:

Heaters on heavy and medium hammers - 0.55-0.65 kW / m 2 on light hammers - 0.035-0.18 kW / m 2; punchers and pressers - 0.037-0.2 kW / m 2. Emissions of toxic gases from heating furnaces in hammer and press spans reach 3-7 g of CO when burning 1 kg of natural gas and 2.2-5.2 g of SO 2 when burning 1 kg of fuel oil. The danger of electric shock arises when using resistance furnaces to heat workpieces that consume electrical power - 15-350 kW at a voltage of 50-80 V at the terminals. With induction heating, the average power transmitted from the generator to the inductor is 15-350 kW, voltage up to 1000 V. When starting gas heating furnaces due to improper ignition, with a sudden stop of the blast, gas seepage in the production room, as well as when air is brought inside gas devices an explosion may occur.

The causes of injuries to those working in the forging and pressing shops are: lack of protection for moving and rotating parts of equipment, lack of protection for the working dangerous zone of presses; lack of provision of the press with two-hand control with such an electrical switching circuit, in which one of the buttons cannot be jammed; lack of blocking of control panels; lack of automatic feeding of blanks into the stamp and removal of parts and waste from the stamping zone.

The operation of electric furnaces must be carried out in accordance with the "Rules for the technical operation of consumer electrical installations". The workplaces of each furnace require an influx of fresh air. Heating furnaces must have thermal insulation of the walls, which ensures heating of external surfaces not higher than 45 0 C. To protect against heat flow, near the side walls of the furnaces, screens are installed at a height of at least 2.5 m, cooled by running water, with holes against the observation and working windows of the furnace. labor foundry welding forging

Occupational safety during heat treatment. Dangerous and harmful factors arising from the heat treatment of products depend on the operations and equipment. The main equipment of thermal shops include furnaces, heating and cooling devices.

Main harmful or dangerous production factors during heat treatment can be the following:

Increased gas contamination or dustiness of the air in the working area. The toxic gases contained in the composition of the atmosphere are: carbon monoxide CO, ammonia NH3, sulfur dioxide S0 2, hydrogen sulfide H 2 S, benzene C 6 H 6, etc. Cyanide salts, the strongest poisons, can be used in heat treatment processes;

Increased temperature of materials or surfaces of equipment, increased level of thermal radiation. Premises of thermal shops are equipped with general exchange supply and exhaust ventilation. Air is supplied to the upper zone of the room, air mobility in the workplace is not more than 0.3 m/s;

Increased intensity of electromagnetic fields. During the operation of high-frequency installations, the human body can be affected by electric and magnetic fields;

Noise level at workplaces: during operation of furnaces, for example, during remagnetization of cores in induction heating furnaces;

Moving machines and mechanisms.

The premises of thermal shops are equipped with public supply and exhaust ventilation. At heating furnaces, either canopies or combined exhaust hoods are installed above the loading windows.

We determine the heat from all surfaces of the furnace; radiation;

Heat dissipation through closed oven doors;

Heat dissipation from umbrellas;

Heat dissipation from the cooling metal;

Heat generated by hot gases escaping into the room through umbrellas and leaks in the oven doors;

Heat transfer of the furnace to the room by convection;

The amount of gases escaping into the room from the furnace through the open feed opening.

Air exchange by heat is determined by the formula:

Where Z- the amount of air in m 3 / s, introduced into the room to absorb excess heat. The same number must be removed.

m- for thermal shops, m = 0,45;

c- specific heat capacity, J / kg k

With\u003d 1.004 J / (kg k)

t yx- temperature of the air removed from the workshop, 0 C

t etc- the temperature of the outside air supplied to the room

t etc + 5 0 = t r.z.

k 2 - MPC, mg / m 3

In thermal shops, equipment that is a source of emission of harmful and explosive substances is equipped with local exhausts.

Product coloring.

The main unfavorable factor characterizing the working conditions of painters at industrial enterprises is air pollution, especially the workplace, harmful substances - solvent vapors and colorful aerosol. As mentioned above, the degree of pollution depends on many factors:

Compositions of paint and varnish coatings, organization of the technological process; coloring method; features used in the painting of ventilation devices. The concentration of harmful emissions in the breathing zone at painting stations (without ventilation), depending on the painting method:

pneumatic, c \u003d 65 - 96 mg / m 3;

airless spray, c = 16-16 mg/m 3 ;

brush, s \u003d 130 mg / m 3;

Hydroelectric, c \u003d 925 mg / m 3 (xylene, MPC \u003d 50 mg / m 3).

The premises of the painting shops are equipped with mechanical supply and exhaust ventilation. Air removal with local suction technological equipment carried out from the lower (working) area of ​​the workshop (paint booths, floor exhaust grilles). In addition to local exhaust ventilation, air is removed from the upper zone of the room. The amount of air removed from the upper zone is determined at the rate of 6 m 3 /h per 1 m 2 of the workshop floor area. When large products are painted with a brush at non-permanent workplaces, only general exchange mechanical supply and exhaust ventilation is allowed.

Cameras must be used for manual dyeing of products. In this case, the product should be located in the chamber, and the painter - outside the chamber or in its open opening, the air sucked from the spray painting posts (from chambers, floor grates, etc.) is cleaned from the resulting paint aerosol. Cleaning is carried out in a wet way (in hydrofilters).

Depending on the nature of the products being painted and the organization of the technological process, the chambers can be dead-end or walk-through with horizontal or vertical air movement in them. If, when painting large products, the painter is forced to move over the entire area of ​​​​the chambers in the process of work, vertical movement of air from top to bottom is carried out in it. Supply air enters through the entire perforated surface of the ceiling, filling the working area and pushing down the colorful aerosol and solvent vapors, which are removed through grates in the floor of the chamber (chambers with lower suction).

To ensure favorable working conditions in chambers with horizontal air movement (with lateral suction), the main thing is the correct position of the worker. The most favorable working conditions are achieved if the painter is outside the chamber and paints through the working opening. Research confirms that the effectiveness of local suction from painting posts is directly dependent on the speed of air suction through the painter's workplace, i.e. on the intensity of removal of harmful secretions from the breathing zone of the worker. It has been established that the minimum speed capable of entraining harmful emissions from workplaces when painting in production chambers is approximately 0.5 m/s (and on floor gratings with large masses of air flowing to them - 0.3 m/s).

The amount of hazards released into the room vapors of each solvent and thinner can be determined by the formula:

g \u003d m G cr C (g / h)

where G kr - the consumption of paints and varnishes in g / h; m - the value of the component of the solvent or thinner in proportions to the weight of paints and varnishes; C - evaporation coefficient, the value of which is accepted: C = 0.3 h 0.8 - when painting with oil enamels; C \u003d 0.5 h 1 - painting with nitro enamels;

Weight composition of the solution in% -80

The paint is injected - 70% acetone, 30% thinner;

brush color - 160-180 g / m 2;

acetone> m 1 \u003d 0.8 0.7 + 0.3 0.3 \u003d 0.74

g = 0.74 160 0.74

The amount of air removed from chambers (cabinets) with side suction is determined by the rate of air suction into open openings according to the formula:

L = FV 3600 m3/h,

Where F- total area of ​​working openings;

V- the average air velocity in the openings, taken depending on the method of painting and the composition of paints and varnishes according to table. 1.

Table 1. Estimated air suction rates in the openings of spray booths with side suction

Pneumatic spraying - the paintwork material, being captured from the container by an air jet, is sprayed, forming a torch of colorful aerosol. The application of paint is carried out by a paint sprayer, to which paint and compressed air are supplied.

Airless spraying - the paint material is fed to the spray nozzle under high pressure(40-250 kg s/cm) and sprayed without compressed air.

The paintwork material at the exit can be heated up to 40-100 0 С (airless spraying with heating of the paintwork material) and applied under a pressure of 40-100 kg s / cm 2 or at an ambient temperature of 18-25 0 С applied under a pressure of 100-250 kg s / cm 2. The method is recommended for painting medium, large and small-sized parts and products of І and ІІ groups of complexity, (with this method, compared with pneumatic spraying), the specific consumption of paints and varnishes is reduced, the consumption of solvents is reduced and the painting time is reduced, labor productivity is increased by 1.5- 2 times.

Electromanual spraying (paints and varnishes are applied by manual electropainting installations various types). The method is convenient for painting small products of any configuration and products such as nets, gratings. The electrocolouring method is based on the transfer of charged particles in electric field high voltage, which is created between two electrodes at different potentials. One of the electrodes is the product to be painted, and the other (negative) is the spray device, to which high voltage and paint material.

The amount of ventilation air (m 3 / h) for chambers with lower suction is determined by the formula

where g is the specific air consumption per 1 m 2 of the floor area of ​​the chamber (m 3 /h), taken depending on the method of application and the composition of paints and varnishes according to the bottom tables.2;

F - chamber area, m 2 .

Table 2. Specific consumption per 1 m 2 floor area of ​​the chamber with lower suction.

Tubeless painting is used in the production of large products of small-scale production, when the use of spray booths is impossible.

Welding production.

The chemical composition of emitted hazards depends mainly on the composition of welding materials: wire, electrode coatings, fluxes.

In a number of cases, the welding method also has a significant effect on the composition of the released aerosols. Thus, in manual welding with stick electrodes and semi-automatic welding in carbon dioxide with a wire identical in composition to the electrode rod, the amount of manganese oxides in the aerosol is different: in semi-automatic welding it is slightly higher than in manual welding. This can be explained by the fact that during welding in carbon dioxide, manganese vapors released from the open surface of the weld pool come into contact with free oxygen atoms, while during welding with coated electrodes, their interaction is inhibited by a layer of slag. In welding, such occupational diseases of electric welders as pneumoconiosis and manganese intoxication predominate.

The mechanization of welding work largely depends on the method of welding, the availability of welding materials and equipment that allow automatic and semi-automatic welding in all spatial positions of the seam. In recent years, welding in carbon dioxide and other shielding gases has become increasingly important.

The essence of the technological process of this type of welding is that shielding gas is supplied from a cylinder or other source through the nozzle of a special burner into the welding arc zone. Shielding gases include argon, helium, nitrogen, carbon dioxide, etc. Two types of shielded gas welding are used: non-consumable and consumable electrodes.

Electric welding in a shielding gas environment has a number of technological, production and economic advantages compared to manual electric arc welding and is gaining the right to be widely implemented.

Its most important advantages are: high thermal power of the arc, which ensures the speed and productivity of welding, high mechanical strength of the weld and its good appearance, the ability to weld various and dissimilar metals and thin-walled products. When welding with a consumable electrode, dust, ozone, and carbon monoxide are released in large quantities.

More than 50% of the volume of welding work at enterprises is carried out at non-stationary places, on large-sized products; about half of them are inside closed volumes. Welding on tables is only 10-15% of the number of employed electric welders. The spread of welding aerosol as it moves away from the welding site in the horizontal and vertical directions is characterized by a sharp drop in concentration. With manual and semi-automatic welding, it is impossible to achieve a decrease in the concentration of aerosol at the welder's workplace to an acceptable level by means of general ventilation. A radical and economical solution is a local exhaust device 1. All local exhaust ventilation devices are divided into two main groups:

1) for stationary and

2) for non-stationary posts.

The most reliable and economical designs of local exhaust devices of stationary welding stations include fume hood type exhausts. Almost complete capture of dust and gases during welding in a shelter is achieved at an air entry speed through the working opening of 0.5-0.7 m/s, depending on the welding mode and the toxicity of emissions, determined by the brand of electrodes used. However, the scope of use of fume hoods is very limited; in many cases, cabinet enclosures interfere with process operations.

When welding on tables, panels of uniform suction - inclined and vertical - are widely used. When welding on welding tables of parts with a length of not more than 1 m, a height of up to 0.5 m, an inclined panel designed by S.A. Chernoberezhsky and a panel designed by T.S. Karacharov is used. The inclined panel is mounted above the welding table on the opposite side of the welder's workplace at an angle of 45° to the vertical and at a height of 300 - 350 mm from the table surface, and the gap between the table and the panel is closed, and a horizontal visor is installed on top.

In the suction opening of the panel, fixed metal plates are installed, which reduce its free area to 25% of the overall one. Due to this, a fairly uniform velocity field is created, which leads to better trapping of dust and gases. Welding should be carried out at a distance of no more than 0.6 m horizontally from the bottom edge of the panel. The air consumption per 1 m of the overall section of the suction hole is 3300 m3 / h at a speed of 0.9 m / s.

In some cases, in practice, vertical panels of uniform suction or lower exhausts through a grate in the plane of the table are more convenient. To effectively capture dust and gases with the same dimensions of the parts to be welded, the volume of air removed must be increased compared to the inclined panel by 25 and 100%, respectively, since the heated stream of polluted air should be deviated from the direction of its natural movement by 90 and 180 ° instead of 45 - 55° with inclined panel. On stationary stands for welding products with a size of not more than 2 m, rotary-lifting air inlets are used various designs. These include LIOT air inlets. The movable part of the receiver is mounted on a swivel bracket, which allows you to move the exhaust device to the side during the rearrangement of the items to be welded. With a fixed bracket, the entire device is attached to a wall or column. The receiver is suspended on a cable to the movable part of the air duct and with the help of this cable and a telescopic device it can move vertically by 300 mm and rotate 360. Required volume of removed air - 2000 m3/h.

When welding the same type of structures on permanent stands, in particular on mechanized production lines, local exhaust devices built into mechanical welding equipment can be an effective and economical means.

In non-stationary welding conditions, in particular, when assembling large-sized products, mounting various units, when working inside closed volumes, it is possible to use dust and gas receivers that are small in size, easily transportable and fixed near the welding site.

When welding in a shielding gas environment with a consumable electrode, the use of exhaust systems for general and local purposes turned out to be ineffective, due to the fact that gas and dust emissions must be removed from environment welder without violating the gas protection of the welding zone. The main elements of such a suction unit should be compact dust and gas receivers. The requirement for compactness and possibly small dimensions of local suctions has led to the need to create high vacuum dust and gas suction units.

For manual welding, a small-sized portable dust and gas receiver with a pneumatic suction cup - holder has been developed, which allows you to quickly transfer and fix the receiver near the welded seam.

The action of the suction cup is based on the use of vacuum for mounting the receiver, created by the exhaust unit. The suction cup is mounted behind the dust and gas receiver in a light and flexible reinforced vacuum hose. The main elements of the suction cup - holder are: a rubber hemisphere, a diffuser clamp and a hollow sleeve. Experimental verification in working conditions it was found that when welding in different spatial positions, a satisfactory effect of dust and gas trapping and reliable fastening of the dust and gas receiver is achieved with a volume of air being removed of 150 m 3 /h. The radius of action of such suction is 150 mm.

The relocation of the receiver during operation should be carried out regularly - with each change of electrodes when welding horizontal seams, less often when welding vertical and ceiling seams. When a welder works inside closed compartments, he spends up to 10% of the working time on moving the receiver, depending on the complexity of performing electric welding work.

In order to substantiate the initial data for the development of local exhausts built into welding torches, dust and gas receivers of various designs were manufactured. It has been experimentally proved that during semi-automatic welding in carbon dioxide with a torch having the shape of a semicircle with a force Y= 200A directional air flow with a speed in the welding zone from 0.2 to 0.5 m/s does not negative influence on the quality of the weld and at the same time helps to reduce the concentration of welding aerosol at the workplace of the welder. The required volume of air to be removed depends on the height of the intake inlet of the receiver. The supply of carbon dioxide to ensure high-quality protection of the weld was 0.6 - 0.7 m / h. Abroad, attention is also paid to the creation of "smokeless" semi-automatic torches for welding in shielding gases.

Assembly and welding shops, in addition to local exhaust systems, are equipped with general ventilation. Local suction usually provides 50-60% of manual welding stations, with the average capture rate of portable local suction being about 75%. Non-stationary posts of semi-automatic welding are not provided with local exhaust. Therefore, welding aerosol enters the workshop air, dilution of which to acceptable concentrations is the task of general ventilation systems. Supply systems of general ventilation carry out partly or completely the function of air heating.

Air exchange is calculated for dilution to the maximum allowable concentrations of welding aerosol and its main toxic components. The calculation is made for each type of welding material used in the workshop according to the total release of aerosol, as well as according to the main toxic components contained in it. The obtained values ​​of air exchange must be summed up for each type of harmful emissions and a large amount is taken as the design capacity of the shop ventilation systems. According to some hygienists, air exchanges calculated from copper and zinc compounds should be summarized as air exchanges for unidirectional agents.

The choice of a rational way of organizing air exchange depends on the nature of the distribution of harmful emissions in the production room. The choice of the scheme for organizing air exchange is also determined by the nature of the distribution of the aerosol concentration in the air of the workshop outside the welding torch. Studies in existing assembly and welding shops of large volume, equipped with various systems mechanical ventilation provided natural ventilation or without organized ventilation showed that the average dust content of the air in the shops at different levels is almost the same.

The nature of the distribution of the concentration of the welding aerosol in the air of the production room is such that the air exchange in the assembly and welding shops should be calculated based on the total amount of the released aerosol (of course, minus the amount captured by local exhausts), assuming the air exchange efficiency coefficient equal to one.

The practical constancy of aerosol concentrations along the height of the workshop makes it possible to recommend concentrated supply of fresh air as one of the most rational, economical and aesthetic methods of air distribution. This method of distribution is also desirable from the point of view of ensuring a uniform temperature in the volume of the room by supply and heating systems. As a result of the research, it was also found that the concentration of dust particles near the workplace of the welder also depends on the degree of dust content in the air in the entire production room. Best conditions for the work of the welder are created when stationary welding posts are at the end of the air flow created by the supply and exhaust ventilation.

With general ventilation, parallel air flows are created to increase its efficiency. General ventilation Based on parallel air flows, there are three ways: ventilation with parallel horizontal air flows, ventilation with parallel upward air flows and ventilation with parallel downward air flows.

In Japan, the newly built welding shops of the Hitachi Josen company used ventilation with parallel flows directed upwards (blowing up). In this case, parallel flows and welding fumes move in the same direction, which favorably affects the removal of fumes. To improve efficiency, it is necessary that the mass of parallel flows be less than or equal to the amount of exhaust gases in the room.

With the help of scavenging fans installed under the workshop floor, fresh air is supplied from outside to the workshop through ventilation grilles on the floor at a speed of 4.5 m/s. The fresh air flowing over the grate creates parallel upward air currents that trap the welding fumes.

In addition to gases and aerosols, the possibility of air pollution and other substances is not excluded. For example, during the repair welding of tanks for the transport of liquid hydrocarbons, flammable and explosive vapors and gases may occur.

Such tanks are thoroughly cleaned before starting welding. If the preliminary preparation of the tank was unsuccessful, it is necessary to fill the tank with either water vapor or protective gas (nitrogen, carbon dioxide). For reliable protection of the welder or gas cutter working inside the tank, it is necessary to ensure the obligatory exhaust of gases and smoke from the place of work, as well as the supply of fresh air. In this case, the length of the air hose should not exceed 15 m. If the concentration of toxic gases exceeds 2 vol%, the welder must immediately leave the tank, even if he is equipped with a protective mask with filters. Very convenient for working in closed tanks is a special mask for a welder, developed by the Institute for Labor Protection of the GDR, equipped with a light hose for supplying clean air under a small pressure directly to the respiratory organs of the worker.

It is absolutely unacceptable to supply pure OXYGEN inside the tank, because it can be adsorbed on the welder's overalls, and if random sparks get in, it can contribute to instantaneous ignition of the clothes. A welder working in a closed tank or in a narrow room must be dressed in clean overalls.

conclusions

Unfavorable indoor air conditions, in addition to disturbing the health of workers and increasing labor productivity, can adversely affect the condition of equipment and building structures;

The fight against air pollution should go first of all along the path of improving technological processes and equipment;

Pest control is carried out with the help of ventilation (local and general exchange);

Local exhaust ventilation is designed to capture and remove polluted air directly from the places of formation or exit of harmful emissions.

If sources of emission cannot be fully localized by the action of local exhaust ventilation, then general exhaust ventilation is carried out.

Plasma cutting and spraying of metals . Plasma treatment of metals is one of the progressive technological processes, however, in our country, unfortunately, it has not yet been widely used.

Plasma is a highly ionized and electrically conductive heated gas. It is formed using a generator, the main part of which is an electric arc burner, which is a chamber with a narrow opening for the plasma outlet. Plasma-forming gas (nitrogen, argon, hydrogen) is fed into the chamber and a potential difference is created. The temperature of the plasma jet ranges from 6000 to 30000 0 C. The sprayed material in the form of powder or wire is introduced into the plasma jet and chamber. The most commonly used metals as the sprayed material are tungsten, zirconium, aluminum oxide, etc.

During plasma spraying and cutting of metals, the following harmful factors act: noise, dust, gases, thermal and ultraviolet radiation. Noise during plasma processing of metals of aerodynamic origin. It arises due to the passage of plasma at supersonic speed through a narrow hole in the burner nozzle. The noise intensity depends on the welding mode and the nature of the plasma gas: with argon it is 117 dB, and with a mixture of argon and hydrogen - 130 dB.

Plasma-arc cutting is accompanied by the release of dust into the air. The amount and composition of dust depends on the grade of steel being cut. The emitted gases are nitrogen oxides, carbon monoxide. The concentration of dust in the breathing zone of the gas cutter in the absence of local suction reaches 40-80 mg/m 3, and with an increase in the thickness of the metal being cut, it increases, the dust contains a large amount of manganese oxides. The electric arc and the plasma jet are sources of infrared and ultraviolet radiation, as well as luminous flux high brightness. The main mass of the dust and gas cloud during plasma cutting goes together with the gas torch under the sheet being cut. The most effective removal of harmful impurities from the worker's breathing zone is achieved by a rational design of local suction. The most effective design is a cutting table with a lower suction of harmful substances.

? Improvement of working conditions of electroplating shops.

1. Occupational hazards released in the electroplating shop.

The protection of ferrous metals from corrosion is becoming increasingly important in the national economy. Large share in common system measures to protect ferrous metals from corrosion are occupied by galvanic coatings with non-ferrous metals and metal oxides.

Technological operations performed in electroplating shops , very varied. They are based on chemical or electrochemical processes, for which high-power direct current is used in electroplating shops.

The whole cycle of operations of the electroplating shop can be basically divided into three parts:

a) preparation of products for coating - degreasing parts, cleaning them from scale, corrosion, irregularities, roughness;

b) electric plating - chromium plating, zinc plating, nickel plating, copper plating, cadmium plating, oxidation, etc.;

c) processing of parts after coating - polishing, impregnation.

The degreasing process is associated with the use of harmful substances. Degreasing often involves parts contaminated with mineral oils, which have to be removed with organic solvents.

Degreasing solutions are heated to 70°C. At the same time, water vapor is intensively released, carrying traces of alkali, which form fog. When working on the degreasing of parts, damage to the operating personnel is possible when in contact with solutions and vapors of harmful degreasing and passivating substances and solvents (caustic alkalis, dichloroethane, trichlorethylene).

Short-term inhalation of trichlorethylene vapors at low concentrations causes dizziness and noise in the head.

Etching of metal products is carried out to remove scale, rust, dirt from their surface in order to prepare them for subsequent rolling, drawing, stamping or for applying decorative and protective coatings. Etching is carried out mainly with aqueous solutions of sulfuric, hydrochloric acid and their mixture.

After etching, the products are washed in hot and cold water and neutralized in an aqueous solution of soda. The temperature of the solutions is 70-90°.

Metal pickling is accompanied by: 1) abundant release of water vapor from the pickling baths and from the washing and neutralization baths, as well as from the surface of the materials taken out of the baths when they are transferred to other baths; 2) the release of hollow droplets-bubbles of hydrogen enclosed in a film from the liquid in the bath (solution of sulfuric acid). Gas bubbles, rising above the bath and bursting, saturate the air with tiny particles of acid. Etching may be accompanied by the release of arsenic hydrogen if poorly purified acid with an admixture of arsenic acid is used. The allocation of these hazards occurs from the mirror of the baths and from the surface of the pickling products. When pickling cast iron, sulfur compounds that are harmful to health are formed. Beryllium dust and compounds are highly toxic. When pickling, the concentrations of harmful emissions according to CH 245-71 are as follows: sulfuric acid (foggy) - 1 mg / m 3, chromic anhydride - 0.1 mg / m 3.

Onboard suctions are effective only for removal of the vrednost which are emitted from a surface of bathtubs. After being removed from the baths in the area of ​​chromium plating, nickel plating, oxidation, the parts are in an elevated position above it for some time to allow the solution to drain back into the bath. In this case, the onboard suctions are not able to capture exudates from the surface of the parts when they are taken out of the bath, as well as when moving from one bath to another. Since the surface of the removed parts is small, harmful emissions can be dissolved by the supply air. The organized inflow is taken at the concentration of harmful emissions according to CH 245-71 as follows: sulfuric acid (foggy) - 1 mg / m 3, chromic anhydride - 0.1 mg / m 3.

To remove harmful secretions from the surface of the baths, side suctions are the best. The ideal way to remove harmful emissions would be to completely cover the places of their release, while leaving holes for sucking contaminated air from the working area. Then there would always be a rarefaction in the shelters, which would prevent the leakage of harmful substances in the room. However, the production technology requires open surfaces. At the same time, the speed in the working opening of the cabinet located above the pickling baths is recommended to be about 0.7 m/s.

The choice of the type of onboard suction depends on the dimensions of the products to be immersed in the bath. If the emitted hazard has a lifting force (bath with heated solutions, baths with solutions at room temperature, but the gases emitted are lighter than air, such as hydrogen), then an upward flow is formed above the bath. This flow transports the harmfulness and distributes it throughout the room. The task of the onboard suction is to direct the resulting flow to the exhaust opening and catch it there. With onboard suction, there is an interaction of the velocities created by the lifting force and suction. Bilateral side suctions are recommended to be arranged with a bathtub width of 0.8 m or more.

Recently, inverted side suctions have been used, in which the suction holes are located parallel to the bath mirror. The scope of the inverted suction at the same flow rates is more extensive compared to conventional ones. Inverted side suctions cause a decrease in the useful width of the bath by about 20% and a decrease in the electrolyte level in the bath. Preliminary calculations and research data from the Moscow Institute of Occupational Safety and Health found that, with the same useful efficiency, the volume of air sucked out through onboard inverted suctions averages 50% of the exhaust volumes through conventional onboard suctions. When operating inverted onboard suctions, as clots of chromic anhydride stick to them, reducing the free area.

Onboard suctions are effective only for removal of the vrednost which are emitted from a surface of bathtubs. After being removed from the baths in the area of ​​chromium plating, nickel plating, oxidation, the parts are in an elevated position above it for some time to allow the solution to drain back into the bath. In this case, the onboard suctions are not able to capture exudates from the surface of the parts when they are taken out of the bath, as well as when moving from one bath to another. Since the surface of the removed parts is small, harmful emissions can be dissolved by the supply air. We accept organized inflow by 10-15% less than the exhaust to prevent the penetration of air from these compartments into adjacent rooms. Supply air is injected into the working area of ​​the premises at a height of 2.5 m from the floor, is distributed evenly throughout the premises and is discharged from the supply openings at low speeds. When supplying air from the openings of the air ducts, one should strive to distribute it to both sides of the room. Guide plates (flat blades) are installed in the holes. The cross-sectional area of ​​the holes should be chosen based on the calculation of velocities in them not more than 2 m/s. When removing the sleeves from pickling baths with a temperature of 60°, intense evaporation from the surface of the products occurs. Since their total surface is large, the calculation of general ventilation is based on heat and moisture.

We provide an extract from the upper zone in the amount of 1-1.5 times the volume of the room per hour, we accept the extract from the upper zone as natural through openable transoms.

To limit the fog that forms over the baths, to protect the mirror of open finishing baths from evaporation, the release of aggressive vapors and heat loss, various means are used. Such means can be glass or plastic hollow balls floating on the surface of the electrolyte, which completely cover the “mirror” of the bath. The emerging bubbles of gaseous hydrogen and oxygen, meeting with the balls, burst and are released from the electrolyte particles carried away by them. The same role can be played by plastic and foam cylinders floating on the surface of the electrolyte. Protective layers should be considered as an aid and cannot replace side suctions, especially in baths such as chromium plating baths, pickling baths. The use of plastic balls to cover the evaporation mirror of the galvanizing shop baths makes it possible to simplify ventilation devices and improve sanitary and hygienic working conditions.

Calculation of air exchange for a galvanizing section

The air consumption for onboard suctions depends on the speed of ascending flows over the bath. The higher the temperature difference between the bath solution t b and the room t n , i.e. t b - t n , the greater the speed of heat flows over the surface of the bath and the greater the air flow to the side suctions. The air consumption also depends on the toxicity of the released vapors and gases.

a) bathtubs are equipped with double-sided inverted suctions, as the most economical and stable in terms of air consumption and blowing off the harmfulness spectra by extraneous air currents and stable when the solution is lowered;

b) air mobility in the room is taken = 0.4 m/sec. The volume of air removed by single-sided, double-sided and inverted suctions is determined by the formula MIOT (Moscow Institute of Labor Protection);

where b - specific air consumption, referred to the cubic root of the temperature difference between the bath liquid and air in the room, is determined from the graphs, in m / h;

t is the difference between the temperatures of the bath liquid and the air in the room, °C;

k n - coefficient taking into account the distance from the liquid mirror to the side of the bath, select from table 1;

k v - coefficient taking into account the mobility of air in the room, determined by the graphs;

l is the length of the bath in m;

k t - coefficient taking into account the toxicity of the emitted hazards.

References

1. V.A. Kostryukov. Heating and ventilation, part 2. Ed. Moscow, 1965

2. V.V. Baturin. Fundamentals of industrial ventilation. Ed. All-Union Central Council of Trade Unions, 1956

3. Sanitary rules for welding, surfacing and cutting metals, Moscow, 1970

4. S.A. Rysin. Ventilation units engineering factories. Directory. MashGiZ. 1961

5. M. I. Grimitlin, O. N. Timofeeva. Ventilation and heating. Ed. "Shipbuilding", Leningrad, 1978

6. O.N. Timofeeva. Local exhaust ventilation during electric welding. Profizdat, 1961

7. Express - information "Welding", VINITI, 1974, No. 9.

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State budget educational institution

Higher professional education

Altai State Medical University

Ministry of Health and social development RF

Department of Hygiene and Human Ecology

Topic: Physiological and hygienic characteristics of working conditions for workers in the hot shop of a machine-building enterprise

Completed by a student 663 gr.

Kalkina A.K.

Head: professor., d.m.s.

Balandovich Boris Anatolievich

Barnaul 2012

Engineering industry

The engineering industry is a branch of the national economy engaged in the manufacture of equipment, vehicles, automotive and tractor facilities and other mechanisms.

The main workshops in the machine-building industry are foundries, forging, thermal, mechanical and mechanical assembly.

In the foundry, the process of obtaining parts is associated with the manufacture of the necessary forms and pouring them with molten metal (earthen, metal, or chill casting, as well as pressure casting). The foundry shops prepare materials for melting and load them into furnaces, melt metal, release and pour into molds, prepare molding and core earth, prepare molds and cores, knock out products from molds, trim and clean products.

All these processes are accompanied by the release of dust, as well as toxic and irritating gases (carbon monoxide, sulfur dioxide, acrolein, nitrogen dioxide, etc.). When knocking out and cleaning the casting, noise and vibration occur. When observing the melting of metal and pouring it into molds, workers are exposed to high temperatures and radiant energy.

All this has an adverse effect on the health of workers, can cause acute and chronic occupational poisoning and diseases (for example, foundry fever).

In blacksmith shops, the main operating harmful factors are high temperature and infrared radiation, high physical activity, high noise level and impact vibration.

In the workshops of thermal and electrolytic processing of metals, the main occupational hazards are high temperatures with infrared radiation, as well as the effect of toxic fumes and gases during the processing of products in cyanide baths.

All of the listed occupational hazards have an adverse effect on the health of workers, can cause acute and chronic poisoning and disease. Therefore, in the hot shops of the machine-building industry, measures are taken to improve the workplace in combination with preventive measures.

Wellness activities. The fight against occupational hazards goes both along the path of improving and improving technological operations and equipment (for example, the use of automation), and along the path of improving the microclimate of the workplace (the use of supply and exhaust ventilation, shielding and water protection of a worker in hot shops, a device for extracting harmful gases and dust at the place of their formation, noise reduction, etc.).

In the foundry, the replacement of earth with liquid quick-drying mixtures is widely used, injection molding and chill casting into metal molds are being introduced. Sandblasting of castings is being replaced by hydraulic, hydro-abrasive and cleaning by means of a spark discharge in a liquid medium.

In the forge shop, heating furnaces are being switched from solid, liquid and gas fuels to electric induction heating, steam hammers are being replaced hydraulic presses, reducing the physical load of the worker due to the introduction of mechanization.

In the shops for heat treatment of metals, cyanide and lead baths are equipped with shelters with local suction of harmful products, special attention is paid to shielding and isolating the worker from installations with high-frequency currents, measures are being taken to increase the electrical safety of all operations in this shop.

In all hot shops of the machine-building industry, great attention must be paid to the personal hygiene of workers, their overalls, eye protection, as well as regular preventive medical examinations and the organization of dispensaries at factories.

Foundry

Foundry production (the most important component of the engineering industry) is the production of products by pouring earthen, metal, shell molds with molten metal, as well as by injection molding. There is still a labor-intensive method of casting iron castings and parts of steel castings into earth molds. The most unfavorable factors in foundries are: dust (released during the preparation of molding and core sands, knockout, chipping and cleaning of castings), toxic and irritating gases (released during pouring of metal), noise and vibration during knockout and cleaning of castings, exposure to high temperature and radiant energy in the melting and pouring of metal. The degree of manifestation of one or another factor depends on the architectural and construction design of the building box and the internal layout of the spans, aeration conditions, the nature of the process equipment and its location, and the type of fuel used. The air in foundries of all types of casting (black and non-ferrous) during three-shift operation is never free from toxic and irritating gases and vapors - carbon monoxide, sulfur dioxide, acrolein, ammonia, formaldehyde, nitrogen dioxide, etc. The concentration of these gases in modern conveyor and modernized shops in most cases do not exceed the maximum allowable. Recently, a sharp reduction in the content of zinc oxide fumes in copper foundries has been achieved, due to which cases of foundry fever among workers have become extremely rare.

The improvement of working conditions in foundries consists in the rational layout of premises, the improvement of equipment, its rational placement in spans, the mechanization of production processes, the rationalization and automation of individual technological processes (for example, casting into shell molds). A significant advantage of the method of casting into shell molds are: a sharp reduction in the cost of molding materials and a decrease in the amount of recycled earth; obtaining a clean and smooth surface of products, which greatly reduces and sometimes eliminates trimming and cleaning operations; significant reduction total number workers, mainly persons exposed to dust containing quartz. However, there are some unfavorable hygienic factors, for example, the release of dust from quartz sand, pulverized bakelite and, in some cases, chromomagnesite and quartzite, as well as bakelite solvent vapors (ethyl alcohol) during the preparation of the molding sand. In addition, during the manufacture of crust forms, air pollution is possible with carbon monoxide, phenol and intermediate products of thermal decomposition - hydrocarbons, including 3,4-benzpyrene. The main sanitary and hygienic requirements for casting into shell molds are: mechanization of the entire process of preparing molding materials, in particular, the exclusion of manual operations when loading and unloading dusty materials, mechanization of the removal of finished half-moulds, especially on multi-position molding machines. It is very expedient to reduce dust content by replacing conventional mixtures with clad sand. In the pouring areas, it is necessary to provide a sufficient area for holding the poured molds under a shelter equipped with local exhaust ventilation. The process of precision (precision) casting is accompanied by the release of unsaturated hydrocarbons, ammonia, acrolein into the room air during the molding and knocking out of dry filler and applying marshalite (containing 80--90% free SiO2) to the mold. Improving measures require devices for general and local exhaust ventilation, special fume hoods for drying molds in an ammonia environment and for cooling metal-filled flasks with lattice shelves and air supply from below, and showering ventilation at the workplaces of casters.

Forging and pressing production

The heating of metal and its processing in forge-and-press shops are accompanied by exposure to radiant heat from both the heated metal and heating furnaces. Indoor air is polluted with carbon monoxide and sulfur dioxide. However, in modern workshops, the content of CO and SO2 in the air is low, since the workshops are equipped with aeration devices and rational smoke exhaust systems.

Improving measures should be aimed at creating favorable meteorological conditions in forging and pressing shops. For these purposes, gas purified from sulfur impurities and induction heating are used. In the case of using fuel oil, it, like the air supplied to the nozzles, must be heated before being fed into the furnace. This provides a more complete atomization and combustion of the fuel and reduces the formation of products of incomplete combustion. Noise reduction in workshops is achieved by replacing steam punching hammers with hydraulic presses. The exclusion of the physical stress of blacksmiths is achieved by complex mechanization of the main labor and intermediate operations, the use of manipulators for tilting products under pressure, the use of cantilever or electric bridge cranes for the same purpose, and a device; roller tables for feeding forgings, mobile mills, etc.

physiological hygiene work health

Heat treatment of metal

Heat treatment of metal (at t° 1000--1300°) is accompanied by chemical processes. Furnaces are heated by gas, liquid and solid fuel, electricity. The heat treatment of metal with high-frequency currents (induction heating in a high-frequency electromagnetic field) has become widespread. Systematic exposure to high and ultra high frequency fields can cause workers functional disorders CNS. During heat treatment of products in cyanide baths, vapors of cyanide compounds are released, the skin is contaminated with dust containing cyanide. Work on lead baths is accompanied by air pollution with lead fumes. Due to the presence a large number furnaces and baths, as well as heated metal in thermal shops, unfavorable meteorological conditions are created.

Improving measures consist in the normalization of the microclimate, the equipment of cyanide and lead baths local ventilation observing personal hygiene measures. When working with generators of high and ultra-high frequencies, the electric field strength should not exceed 10 W. Under conditions of short-term exposure (not more than 15-20 minutes per working day), the exposure intensity is up to 1 mV / cm2 with the obligatory use of goggles. Installations must be shielded and electrical safety measures must be observed. In mass production, the improvement and improvement of working conditions are achieved by the use of continuous furnaces with pusher conveyors and other mechanisms. The processes of heating, hardening, washing, loading, unloading are automated.

Thus, the prevention of the adverse effects of microclimate parameters consists in bringing the microclimate parameters to optimal (permissible) values. The main way to "improve" working conditions in hot shops is to change technological processes in the direction of limiting (shielding) heat sources and reducing the contact time of workers with a heating microclimate. It is possible to achieve a reduction in the contact of workers with sources of thermal radiation and moisture entering the air of the working area, using extensive automation and mechanization of technological processes, sealing production equipment, switching from cyclic production processes to continuous ones, as well as reducing physical effort, attention strain and preventing fatigue. workers. Heat radiation and the flow of radiant and convective heat into the working area are significantly reduced when thermal insulation and shielding are used. Calculations show that the thermal insulation of the walls of thermal furnaces, which reduces the temperature of their surface from 130 to 50°C, reduces the heat release by 5 times. Reflective screens and water curtains are very effective protection against radiant heat. A 10 mm layer of water is sufficient to absorb all the thermal radiation from an open heating furnace. Multilayer screens almost completely reflect thermal radiation from the walls of high-temperature units and equipment. At some workplaces, for example, at posts and control panels for foundry equipment, in the cabins of crane operators, electric and gas welders, it is advisable to use wall cooling along with reflective screens or install cooled (up to + 5 ° C) screens that enhance heat transfer due to radiation. In industrial premises with powerful sources of convection and radiant heat, one of the important measures to normalize meteorological conditions is aeration, which ensures unhindered exit of heated air through shafts and windows in the upper zone of the premises. however, aeration alone cannot provide a favorable microclimate at all workplaces, so ventilation systems and local air showering should be used.

Among the measures of personal prevention of overheating, the correct organization of drinking regime. With significant loss of moisture (more than 3.5 kg per shift) and a significant time of exposure to infrared radiation (50% of working time or more), chilled (up to + 8 ° C) salted (0.3% salt) sparkling water with the addition of vitamins is used . It is effective to replace water with chilled black or green tea. With less loss of moisture, the consumption of salts is replenished with food intake. To prevent adverse shifts due to heat load, it is essential to observe a special work regime with mandatory breaks in work. The introduction of breaks throughout the shift contributes to the restoration of the functional state of cardio-vascular system. A beneficial effect after thermal stress is provided by hydroprocedures in the form of half-showers installed near the place of work. To a large extent, protective clothing protects against overheating, which must be air and moisture permeable, have certain heat-shielding properties and, in some cases, reflect infrared radiation.

Literature

1. Occupational health: textbook / Ed. N.F. Izmerova, V.F. Kirillova.-M.: GEOTAR-Media, 2008-592 p.: ill.

2. http://www.dissercat.com/

3. http://www.otb.by

4. http://dic.academic.ru

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