Foundry Production

Foundry Production is characterized by a number of professional harmfulnesses and dangers requiring special preventive measures. The basis of casting processes lies in the property of metals to change their physical state under the influence of one or another high temperature. Work in foundries comes down to the following main production processes. 1) Preparation and treatment of molding materials (earth, sand, coal, animal manure) used for making foundry molds. 2) Molding, i.e., formation from molding material of corresponding configuration molds, serving as containers for cast objects and filled with molten metal. 3) Manufacturing of cores or inserts placed in foundry molds to obtain various recesses and openings in the finished castings. 4) Drying molds and cores in special drying chambers. 5) Melting metal in cupolas and melting and crucible furnaces. 6) Pouring molten metal into foundry molds. 7) Knocking out cast articles from molds enclosed in iron frames (flasks), cutting off and cleaning them from adhering molding earth and removing excess metal formed during casting. Work in the molding material preparation department proceeds in conditions of formation of quite a large amount of dust entering the room air. All production processes proceeding in the molding material preparation department (crushing materials in ball mills, grinding and mixing on runners and disintegrators, various methods of sifting them) serve as sources of dust formation. Its content according to data from research conducted in Moscow and Kharkov factories averages from 20 to 50 mg per 1 m³ of air. The working processes of molding material preparation workers during manual handling of materials are characterized by significant muscular strain. In molding operations, the dust concentration in the air of working premises in Moscow factories proved to be lower than in the molding material preparation departments (10.8 mg per 1 m³), and when working with wet earth this figure was even further reduced (to 4 mg). In Kharkov factories, the amount of dust in molding proved to be significantly greater - 33-120 mg per 1 m³ (E. M. Kagan). The overwhelming majority of work in manual molding is done on the earth floor of the foundry, so that molders are forced to keep their bodies in a bent, often quite unnatural position during work. Besides faster fatigue, this forced body position during work with considerable seniority and systematic and constant performance of molding operations can also cause anatomical changes (curvature of the spine). Since materials are usually moistened before molding, the foundry floor is almost always very damp, and in winter it is often necessary to work on cold and frozen earth. This circumstance contributes to the development of cooling-related diseases among molders, especially rheumatism, which is quite a common disease among this group of workers. At the same time, the very low temperature of the premises plays no small role, in winter often dropping below 0°, which is connected with the irrational and quite insufficient heating of foundries. Only in those workshops where central heating is installed are relatively favorable temperature conditions observed (16-22° with 40-70% relative humidity). Recently, machine molding (on machines) has increasingly been carried out in foundries, obviously spreading in factories producing mass and uniform casting. The introduction of these devices made it possible to perform molding work standing, with the body in a normal position, in conditions significantly weakening the harmful influence of dampness on workers. Work on manufacturing cores and proceeds in conditions similar to those just described, however there are separate processes causing significantly greater dustiness than in molding (such as ramming materials in the core box, scraping out recesses and forming openings with the help of wire, cores, etc.). The participation of workers in iron melting processes comes down mainly to work on loading materials into the cupola and discharging the finished molten metal from it. Service of crucible furnaces during copper melting consists mainly in lowering the crucible with materials into the furnace, observing its firebox and unloading the crucible after melting is completed. The working conditions of both professions - cupola loader at the cupola and furnace tender at copper foundry furnaces - are very similar to each other and are mainly characterized by extremely high air temperature and consequently, the intensity of heat radiation at the workplace. At the charging window or other top hole of the cupola, the air temperature reaches 100-110° regardless of the time of year, rarely dropping to 85-90°, and at the same moment at the opposite edge of the working platform from the cupola in winter the temperature is 10 times less than at the charging opening - in summer only 2-2¹/₂ times. Temperature fluctuations in the furnace tender's work zone in a copper foundry are even more significant and range from 12° to 138° in winter and from 25° to 150° in summer. Although the time the furnace tender spends in the zone of highest temperature is very short, he still spends about 25-30% of the entire working time in the sphere of very unfavorable temperature (30-45°). If we add to this the considerable muscular work performed by these workers, especially cupola loaders at the cupola, then we get an idea of those production factors that cause these professions significant, at times exhausting sweating and disturbance of heat balance in the body. Another harmful professional factor in the described work is the presence of harmful gases and vapors in the room air. Of these, the most important are carbon monoxide, sulfur dioxide, and zinc oxide. The first two gases are released in connection with metal melting in both iron and copper foundries, the third - only in copper casting. Carbon monoxide is formed due to incomplete combustion of coke in cupolas and furnaces. It penetrates to the top platform through the charging opening. The CO content in top gases is expressed as 14-16%, while in the air at the loader's workplace its concentration can reach 0.047-0.076 mg per 1 liter of air (Prof. Kagan), which exceeds the established limit by the Institute of Labor Protection (Moscow) of 0.02 mg per 1 liter of air. At copper melting furnaces, this concentration is usually below the specified limit. Sulfur dioxide (SO₂) is formed during combustion of coke containing sulfur impurities; its concentration in foundry air is usually insignificant and generally with low sulfur content in coke does not exceed the established legal norm (0.04 mg per 1 liter of air). Formation of zinc oxide occurs only in copper casting and is due to the addition of zinc to copper necessary for obtaining certain alloys (brass, etc.). The ZnO content in the air undergoes significant fluctuations at different moments of the production process and reaches especially large sizes when discharging metal from furnaces and pouring it from crucibles. Inhalation of zinc oxide causes foundry fever (see). Ready foundry molds, enclosed in special iron linings or frames (so-called 'flasks'), as well as cores before pouring them with metal are subjected to drying in special chambers. Work on loading and unloading flasks and cores from dryers is associated with workers being in conditions of high temperature and in an atmosphere containing poisonous gases (CO and SO₂), especially in cases when drying is carried out directly with hot gases (coming from the furnace) or when fuel is burned in the dryer itself. Drying chambers often also serve as a source of harmful gases entering adjacent working premises. Work of foundry workers performing manual pouring of metal into flasks is associated with heavy muscular load, danger of burns, being in an atmosphere of changing temperatures (mostly elevated) and significant intensity of radiant energy, as well as inhalation of poisonous gases. Temperature in foundry halls during casting (according to data from the State Institute of Labor Protection) ranges from 17.2-28.4°; with relative humidity 44-54%. Concentrations of carbon monoxide in iron foundries (according to the same data) average 0.03-0.05 mg per 1 m³, and only directly above flasks is it significantly greater - 0.21-0.32 mg per 1 liter in iron casting, and 0.14 mg per 1 liter in copper foundries. However, in a number of factories, thanks to proper ventilation of premises and normal production loading of the foundry, the CO content in the air with the currently existing casting technological processes does not exceed the permissible norm (0.02 mg per 1 liter). Sulfur dioxide in iron foundries among flasks was found in amounts of 0.045-0.15 mg per 1 liter, in copper foundries - up to 0.1 mg per 1 liter, in dryers - 0.1-0.15 mg per 1 liter.

According to numerous studies by the Institute for Labor Protection, under the action of ventilation, the CO_a content in foundries during metal pouring does not exceed the NKT norm (0.04 mg per 1 liter), fluctuating within the range of 0.013-0.035 mg per 1 liter. As for zinc oxide, its concentration during casting in brass foundries fluctuates sharply, averaging from 0.003 to 0.07 mg per 1 liter (Yakovenko, Yakobson). Each of these concentrations may have different toxic value depending on the duration of its effect on workers, and therefore the amount of zinc oxide vapor alone by no means determines the danger of professional poisonings. Hydrogen sulfide, cyanide compounds, and arsine may also be present in the air of foundries, but due to their relatively negligible concentration, they usually do not cause professional poisonings. The final stages of the production process in foundries (shakeout, chipping, and cleaning of castings) require muscular exertion and are associated with significant atmospheric dustiness. During these processes, the dust content in the air reaches significant amounts (up to 180 mg per 1 m³), and these concentrations vary depending on the nature of the cleaning and the equipment and tools used (sandblasting machines, crowbars, chisels, grindstones, etc.). From the point of view of the physical and chemical properties of the dust found in foundries, it is characterized primarily by the fact that most dust particles (from 83% to 90%) are very small (less than 10 μ) and therefore can penetrate into the pulmonary alveoli. The solubility of this dust in salt solutions is very small and ranges from 0.015% to 1.1%, which is explained by the silicate content in it, reaching 83.46% in some types of dust. The humidity of the dust varies in different departments: the highest is given by dust in molding departments and the lowest in chipping departments. In general, the dust obtained from chipping and cleaning castings is most harmful from a professional hygiene point of view. To prevent and eliminate professional hazards and dangers in foundry work, it is necessary to strive for a radical change in the technical equipment of foundries and the implementation of maximum mechanization of production processes. In order to ensure normal and uniform temperature in foundries, they must be equipped with adjustable air heating. To combat dust and harmful gases, proper ventilation must be installed, in the first case according to the principle of local exhausts, and in the second case, general supply and exhaust. The development of a rational ventilation system for foundries, due to the unique aerodynamic conditions in them (constant vortex air movements), is still a rather difficult technical task that has not yet been fully resolved. Besides mechanical ventilation, the proper organization of natural room ventilation, utilizing the hot gas currents formed during casting and directed from flasks to the ceiling, apparently plays a significant role. In relation to combating injuries in foundries, proper room dimensions, good lighting, rational work clothing, and personal protective equipment (goggles, respirators, gloves) are of great importance. The social and legal protection of labor in foundry production is regulated by a series of mandatory resolutions of the NKT. These primarily include the 'Rules for Safety in Iron and Brass Foundry Production', published in 1921 and supplemented and amended in 1926; resolutions of 10/30/1925 and 2/24/1926 (News of NKT) on the restriction of the employment of women and adolescents in the most harmful and dangerous work in foundries; resolutions on a reduced working day for brass foundry workers and sandblasters and additional leave for certain categories of foundry workers, as well as on new standards of work clothing for workers. 24

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