Welding connection of metal parts through localized heating, where the metal in the ground connection is brought to plastic or molten state.
In the Soviet economy is particularly widely used gas and electric welding.
The heat sources in gas welding is the flame burning gas: acetylene, gasoline and other dissolved oxygen. Often used acetylene. In arc - electric arc. One of the electrodes is the workpiece, others supplied from outside the metal rod called electrode. "Electrodes" can be without coating and with coating (coating) of different chemical composition, including those with special coating, comprising up to 2% of the radioactive thorium.
The main harmful factors in acetylene welding: danger of explosion of the gas mixture with air, poisoning with acetylene, phosphorous hydrogen and nitrogen oxides.
The main hazards in arc welding: intense light radiation (brightness voltaic arc of about 10,000 times physiologically acceptable), most ultraviolet radiation, welding aerosols, which can be the oxides of iron, manganese, chromium, zinc, titanium, thorium, silicon dioxide, copper, aluminum, lead, calcium, magnesium, fluoride compounds, okis carbon, argon and other Dust has a high dispersion. Maximum permissible concentration of dust in the application of electrodes: manganese 4 mg/m3, fluorine-containing 3 mg/m3, metal without coating or with limestone floors - 6 mg/m3.
When working on welding possible following occupational diseases: pneumoconiosis (see), manganese intoxication (see), fluorine (see), chromium (see), lead (see), diseases of the upper respiratory tract electronically (see Oftalmia), dermatitis (see).
Prevention of occupational diseases and poisoning. Strict implementation of requirements stipulated in San: the rules for welding and cutting of metals, approved by the Ministry of health of the USSR on 17 December 1967, № 725-67. The main of them are: the use of protective shields or helmets with light filters, the density of which must meet the requirements of GOST 9497-60; fencing places welding shields or curtains; the device of local ventilation exhausts and General ventilation.
When additional electrode coating Th02 it is necessary to carry out the "Rules of radiation safety in welding tinted electrodes" (1961); the rules about the maintenance and installation of acetylene devices and storage of calcium carbide; the use of individual safety equipment (goggles, respirators, protective clothing and other).
Persons working on the welding work must undergo preliminary and periodic medical examinations. Electric welders have pneumoconiosis first, second, third stage, are not allowed for electric welding works in closed facilities, and with intoxication manganese, fluoride, lead, chromium, etc. should be transferred to other work not related to the impact of toxic vapours, gases and dust. Women to work inside closed objects are not allowed.