welding, occupational health

From Big Medical Encyclopedia

WELDING — process of compound of metal and non-metallic materials by their alloyage or compression, or a combination of that and other way.

The page is widely used in various industries. By the nature of S.'s energy can be electric (arc, contact, plasma), mechanical (ultrasonic), chemical (gas, or autogenous) and beam (laser, electronic).

One of the elementary and most widespread types of S. is electric arc S. with use of metal and baked carbons. For the purpose of protection of molten metal against oxidation and increase in durability of welded connection enter special substances into material of an electrode or its covering or carry out S. under protection of inert gases (argon, helium), carbon dioxides or use welding gumboils, to-rymi cover S. Kontaktnaya S. place, or S. with resistance, differs in high extent of mechanization and automation, is widely used in mechanical engineering, for joining of pipes of large diameters, etc.

Ultrasonic S. is applied to processing of metals and plastic, and also in surgical practice (see. Ultrasonic therapy ).

Plasma S. is a perspective way at production of products from refractory metals.

Chemical (gas, or autogenous) S. owing to smoother and slow heating of metal is usually applied to compound of metals up to 10 mm thick. The gas flame is formed at combustion of various combustible gases in oxygen (vodorodokislorodny, oxygasolene, oxyacetylene S., etc.). It is widely applied at repair work.

Electron beam (electronic) S. is made by the focused cathode rays in special cameras, in to-rykh vacuum is supported, and applied to S. practically of all metals. In the industry for welding also the radiation of optical quantum generators is used — lasers (see).

The major harmful production factors during the welding works are: intensive light and caloradiance (see); dust (see), containing toxicants (compounds of manganese, chrome, fluorine, etc.); harmful gases — carbon monoxide (see), oxides nitrogen (see), hydrocarbons (see); forced inconvenient working pose of the welder; danger of defeat by electric current (see. Electric trauma ). The range of a radiant energy at electric welding consists of light, ultraviolet and infrared rays. Visible light radiation has the blinding effect on eyes, ultraviolet radiation at short-term impact on eyes causes an electroophthalmia (see. Ophthalmia ), and affecting open sites of skin — burns (see), similar to solar. At long impact on eyes of infrared radiation development is possible cataracts (see).

Dust at S. is formed owing to oxidation of weld metal. Its dispersion is extremely high — apprx. 99% of particles have the sizes to 1 micron. The composition of dust at S. depends on composition of weld materials and character of a covering. At S. (containing titanium) a covering and at S. under protection of carbon dioxide gas as a part of dust, except iron oxides, oxides of manganese, chrome, zinc, titanium and other metals, and also fluorides and silicon dioxide can be electrodes with acid (manganese), the main (fluoric and calcium) and rutile. Concentration of the specified substances is especially high during the welding in the closed and half-closed spaces — compartments of vessels, tanks, blocks, etc. In such workplaces bad working conditions are aggravated with adverse microclimatic parameters, insufficient ventilation and illumination, existence of noise, a considerable exercise stress. At automatic and semi-automatic S. under gumboil of operation are less labor-consuming, release of toxic dust is many times less, than at manual Page. Harmful substances at these types of S. are fluorides, allocation to-rykh increases with increase in content of calcium fluoride in welding gumboils. From numerous ways C. in the atmosphere of shielding gases about a gigabyte. positions S. under protection of argon is optimum without melting - shchimsya an electrode, at a cut concentration of dust of oxides of metals, as a rule, does not exceed maximum allowable concentrations.

The basic occupational diseases at welders are pneumoconiosis (see), sometimes intoxication manganese (see. Manganese ), atrophic and subatrophic changes of a mucous membrane of upper respiratory tracts.

Preventive actions shall be directed to manual arc S.'s replacement automatic and semi-automatic under gumboil, to reduction of content of manganese, chrome, fluorine, silicon dioxide and other toxic and fibrogenny components as a part of electrode coverings and gumboils. Instead of electrodes with a manganese covering it is recommended to use electrodes with a rutile (titanic) covering, combustion to-rykh is followed by smaller formation of toxicants. The correct use of individual protection equipment is important (see. Clothes special , Footwear , Points ). For protection working from influence of a radiant energy of an electric arch use of guards helmets with light filters of different degree of transparency is obligatory. Ancillary workers during S. shall use safety spectacles. For protection of the workers who are carrying out other manufacturing operations in welding assembly shops, jobs of welders at production of products of the large sizes shall be protected with boards or screens; The Page of small products should be made in cabins.

Persons, busy electro-and gas welding, pass preliminary (at revenues to work) and periodic medical examinations (see. Medical examination ).

Bibliography: Braude M. 3., etc. Labor protection during the welding in mechanical engineering, M., 1978; Vorontsova E. I. and Pryadilova N. V. Hygienic assessment of welding of copper, Vestn. USSR Academy of Medical Sciences, No. 2, page 34, 1977; Vorontsova E. I., Gofner A. M. and Mosolov N. I. Hygienic assessment and improvement of working conditions at semi-automatic welding by the powder wire of EPS-15 opened by an arch, the Gigabyte. work and the prof. having got sick., No. 5, page 46, 1968; Blink K. V. Gigiyena and safety of work during the electrowelding works in shipbuilding, L., 1975; Improvement of working conditions during the welding works, under the editorship of E. I. Vorontsova and E. K. Alekseev, page 5, M., 1968.

E. I. Vorontsova.