Electric Welding

ELECTRIC WELDING. In contact E., an electric current is passed through the metals to be welded, which heats them to their melting point. It is performed using special electric welding machines. In arc E., current is conducted to the welding site by means of a thin electrode rod, which melts under the action of the electric arc formed at the point of contact between this rod and the parts being welded. The most common type is manual arc welding, when the welder is at a distance of 0.5-0.75 m from the arc. In automatic E., the work is performed by an automatic head. Having replaced a number of processes (drilling, marking, riveting, etc.), electric welding also eliminates those professional hazards associated with them, particularly riveting (see Metalworking Industry). The E. process (arc) in turn is associated with a number of professional hazards, but the huge difference between the professional hazards accompanying riveting and welding lies in the fact that the work of riveters, despite measures taken, did not lend itself to significant improvement, whereas the work of electric welders is accompanied by less pronounced professional hazards and can be significantly improved. The main harmful moments in arc E., present in the work of an electric welder, are intense radiation, significant air dustiness, forced uncomfortable positions, the possibility of electric shock, etc. In electric welding with an electric arc, the voltage of radiant energy (see) reaches at a distance of 0.25 m-0.6-8 small calories, and at a distance of 0.5 m-0.3-5 small calories. The intensity of action of ultraviolet rays is very high. Several hours after intense exposure under the influence of ultraviolet rays (see), electro-ophthalmias may appear, characterized by eyelid edema, severe eyelid spasms, pain and inability to open the eyes, photophobia, and tearing. These phenomena are quite quickly eliminated and the patient on the second day is able to return to work. Most electro-ophthalmias (90% or more) occur without loss of working capacity. In acute electro-ophthalmia, along with inflammatory changes in the mucous membrane, changes are observed in the epithelium of the cornea in the form of small point-like dusty opacities (infiltrates), which usually disappear after 2-3 days. A study of vision in 150 electric welders (Ioffe) showed that E. does not affect visual acuity and field of vision and does not cause persistent changes. Knapom (Kpar) noted individual cases of damage to the yellow spot by visible rays. Electro-ophthalmia affects not only welders themselves, but also persons performing auxiliary work during E. (helpers, assemblers) or those located near welding sites. The number of electro-ophthalmias is most significant when working on large projects, such as boiler construction, platform construction, in assembly shops, where welding occurs simultaneously at several adjacent locations on unshielded arcs. Welding of small items is done in booths where each welder works in isolation, and ophthalmias are rarely observed (the welder is more often affected by ultraviolet rays from a neighboring arc, from which he is not always protected, than from his own arc). The main cause of electro-ophthalmias is the complete absence or malfunction of protective measures. The fight against electro-ophthalmias in electric welding work, in addition to rationalizing electric welding installations and rational arrangement of the workplace, should be directed along two lines: a) measures to isolate the welder's workplace and b) measures for the individual protection of the welder. It is necessary to install radiation shields (ultraviolet rays) at all welding posts in the form of stationary booths at fixed stationary welding posts and in the form of portable shields surrounding the arc on all sides at non-permanent welding sites. As a material for booths, wood is recommended, coated for fire resistance either with fire-resistant paint or with other fire-resistant material (water glass, etc.). The painting of booths and room walls should be done in light colors with the addition to the paint of substances with a low coefficient of reflection of ultraviolet rays. Among the measures of personal protection in E., the main ones are shields or helmets with special protective glasses ("Tis" of the Izium plant, proposed by the Institute of Labor Protection) and glasses with front and side glasses. For auxiliary workers, glasses with NIS glass in a driver-type frame are used. The shield used to protect the eyes during electric welding work is an ordinary wooden shield with side extensions, into which glass is inserted. It is recommended to insert two glasses: one dark, blocking infrared and ultraviolet rays and reducing the brightness of the electric arc, and another ordinary colorless, protecting the first from metal splashes. As it becomes contaminated with metal fragments, the latter is replaced, while the protective one remains undamaged. There are shield designs with automatic switching on and off of protective glasses (Miller). zvz zv4 Dust in E. is formed due to the oxidation of iron vapors in the air (near the electric arc zone). In terms of dispersion, dust particles in the main mass do not reach a size of 1 μ. E. causes intense ionization of the air with a sharp predominance of negative ions. Since the main source of air pollution is dust in an amount of 10 to 100 mg per 1 m³ of air (formed during the burning of electrodes and consisting, depending on the products and electrodes used, of oxides of iron, copper, zinc, etc.), the fight against it should be the basis for designing ventilation. Ventilation in welding shops should be both local exhaust and general supply-exhaust. The receiver of local exhaust ventilation should be located as close as possible to the welding site, as this to a large extent determines the effectiveness of its operation. The more efficient the local exhaust ventilation, the smaller volumes should be removed by general exhaust ventilation. When welding inside enclosed tanks, air suction is carried out through one of the tank's openings while air enters through an opening located on the opposite side. It is rational when working inside enclosed tanks (boilers, cylinders, etc.) to supply clean air to the breathing zone by means of a shield with double walls. When using such a shield (developed by the Institute of Labor Protection), the dust content in the air inhaled by the welder is sharply reduced. With a dust content of 50 mg/m³ outside the shield, no more than 1 mg/m³ was found behind it (Krantzfeld and Mirsky).--During the electric welding process, various gases have been detected: ozone, nitrogen oxides, carbon monoxide. The concentration of these gases (except when working in tanks) does not exceed the permissible NKT concentrations. Rationalization of the work process of an electric welder. The work of an electric welder is often characterized by an incorrect, forced position of his body, depending on the position of the parts being welded. Significant muscular effort is required to hold the welded parts in the required planes. To support or move the product, auxiliary workers are often involved, who are exposed to professional hazards associated with the work of an electric welder. A number of special devices-mechanisms have been proposed, designed to hold products and their parts during welding (Zaichik, Miller), which eliminate the need for direct participation of an auxiliary worker in supporting and moving the welded product during welding. They reduce muscular work, make it possible to maintain the welding arc on a limited section, thereby providing the possibility of arranging rational local ventilation and lighting, often eliminate the forced position of the body during welding, creating conditions for work in a convenient sitting position. The use of devices should find particular application in mass and series welding. The use of rational designs of electrode holders significantly facilitates the work. Morbidity and traumatism. Materials from insurance funds and special studies (Lipkovich) have established that the morbidity rates of electric welders are lower than the average morbidity rates of workers in machine-building plants. The relatively low morbidity is explained not only by the younger age and length of service of the worker-electric welders, but possibly also by the presence of favorable factors in the external environment: the presence of ozone in the inhaled air, exposure to ultraviolet rays and especially the increased ionization of the air with a predominant increase in the number of negative ions (Leites). The widespread opinion among electric welders about a decrease in sexual excitability associated with work has not been confirmed in the studies conducted (Lipkovich). The traumatism of electric welders is most often expressed in electro-ophthalmias; individual cases of electric shock have also been noted. Legislation on the protection of labor of electric welders. Rules on the installation and maintenance of electric welders are provided by the decree of the NKT of 9/V 1933. For electric welders, mandatory examinations have been introduced by decree of the VTsPSSPS (Bull. VTsPS, 1935, No. 17-18).

By decree of the NKT, a six-hour, shortened workday has been established for electric welders (for work inside tanks) and additional vacations are provided. At many enterprises, in addition to NKT decrees, neutralizing substances are issued (0.6 liters of milk per day).

From Taiz.