WELDER

 

 

Synonym: Fusion welder

 

Job profile

 

Definition and/or description

 

Joins metal parts by various processes in which the surface layers of the metals are in most cases heated to fusion, with or without pressure; the main groups of welding processes are electric-arc (including metal-arc, inert-gas shielded arc, flux cored arc, plasma arc and submerged arc), gas-flame (including oxyacetylene, oxyhydrogen), resistance, electron-beam, induction, laser-beam, thermit, electroslag and solid-state (friction, explosion, diffusion, ultrasonic and cold) welding. Selects and sets up manual or automatic welding equipment and materials according to work specifi- cations or supervisor’s instructions. Examines and prepares surfaces to be joined by cleaning, degreasing, brushing, filing, grinding and other means. Positions workpieces. Adjusts valves or electric switches to control flow of gases, electric current, etc. Ignites or turns off gas-flame, electric arc, thermit mixture or other source of heat. Guides and applies flame, electrode, filler rod, laser-beam, etc. to the workpieces. Examines welded joint for quality or adherence to specifications.

 

Related and specific occupations

 

Thermal cutter (flame cutting, arc cutting, electron-beam cutting); weld surfacer; spark-erosion machine operator.

 

Tasks

 

Adjusting (flow, pressure, etc.); aligning; annealing; applying (fluxes); arc cutting; arc welding; assembling and disassembling; bending; bolting; bonding; brazing; brushing; calculating (current); chipping (excess metal); clamping; cleaning (surfaces); connecting (hoses and cables); controlling; cutting; degreasing; dipping; dressing (electrodes); examining (quality of joint); filing; filling; fixing; flame cutting; fusing; grinding; guiding (rod along the flame); hammering; handling; heat treating; heating and preheating; holding; igniting; installing; inserting; joining; knocking (welds); laying-out; lifting and lowering; loading and unloading; maintaining; marking; melting; mending; mounting; moving; placing; polishing; positioning; preparing; rebrasing; removing (residues); repairing; scarfing (welds); screwing and unscrewing; securing; selecting (tools, materials); separating; servicing; setting up; soldering; sprinkling; straightening; switching (on and off); timing (controls); tinning; torching; touching up; weld-surfacing; welding.

 

Hazards

 

Accident hazards

 

- Falls from height, particularly in construction work;

- Blows from falls of heavy metal parts, gas cylinders, etc.;

- Cuts and stabs from sharp metal edges, etc.;

- Burns from hot metal surfaces, flames, flying sparks, molten metal droplets, thermal radiation, etc.;

- Foreign particles into the eyes. This is a very common risk, and flying particles may enter the eyes even after the welding flame or arc is extinguished;

- Penetration of molten metal droplets or sparks into ears (particularly in overhead welding);

- Fires ignited by flying sparks, flames, red-hot metal etc. A special fire hazard exists when the surrounding atmosphere becomes enriched in oxygen; ignition becomes much easier (e.g., clothes may catch fire and lubricants and solvents are readily ignited);

- Dust explosions during welding in premises in which flour, grain dust, etc., are present;

- Injection of flying metal particles into the skin (face, neck and hands);

- Tyre explosions during welding of vehicle wheels;

- Ignition and explosion of hydrogen (produced by corrosion processes) and various residual combustible gases in mixtures with air in closed vessels;

- Acute poisoning by phosgene formed from chlorinated hydrocarbons which are used to clean the metal, or as paint, glue and other solvents, or by hazardous gases generated during welding, in particular ozone, carbon monoxide and nitrogen oxides;

- Electrocution or electric shocks in all processes using electric current; a particular hazard exists from transient overvoltages, or when using more than one power supply at the same time;

- Ignition of clothes in processes using gas-oxygen mixtures, if the surrounding air is enriched (“sweetened”) accidentally or intentionally with oxygen, in particular if clothes are soiled with oils or grease;

- Fires or explosions within the welding system (pipes, acetylene generator) in gas-oxygen flame-welding processes, in particular because of flame flashbacks or backfire due to faulty equipment or human error;

- Fires and explosions from improper handling of calcium carbide or acetylene in oxyacetylene welding;

- Trapping of clothing, fingers, hair, arms, etc., in automatic (“robotic”) welders.

 

Physical hazards

 

- Exposure to excessive noise levels;

- Exposure to excessive heat or cold, in particular in construction work;

- Exposure to x or gamma rays during weld inspection by radiography;

- Exposure to x rays from electron-beam welding machines;

- Chronic damage to eyes, skin drying and other skin problems (“heat rash”) as a result of exposure to strong actinic light (in particular UV) and heat. Such effects may be aggravated if good exhaust ventilation exists, since the screening effect of dust is eliminated by the ventilation.

 

Chemical hazards

 

- Exposure to welding fumes (see note 3);

- Chronic poisoning as a result of exposure to zinc or cadmium in fumes when welding zinc- or cadmium-plated parts, or to polychlorinated biphenyls from the decomposition of anticorrosion oils, or to constituents of thermal decomposition products from paints during the welding of painted pieces, or to asbestos when flame-cutting asbestos-insulated pieces;

- Siderosis (a type of pneumoconiosis) as a result of inhalation of iron oxide;

- Damage to central nervous system, lungs and liver as a result of inhalation of phosphine (phosphine may be fumed during generation of acetylene from low-purity calcium carbide);

- Respiratory disease due to high concentration of carbon dioxide in the air and the related oxygen deficiency, particularly in closed, poorly ventilated places (this may be aggravated in the case of workers with cardiovascular or pulmonary diseases);

- Irritation of the eyes and the pulmonary system by nitrogen oxides and/or ozone;

- Carbon monoxide poisoning.

 

Ergonomic and social factors

 

- Repetitive strain injury by static-load work;

- Musculoskeletal disturbances because of work in awkward postures;

- Eye strain and fatigue;

- Strenuous physical workload during lifting of heavy parts;

- Muscular stress and strain of hands, from the handling of heavy welding guns, in particular in overhead welding.

 

Addendum

 

Notes

 

1. According to published reports, welders are at increased risk of pneumoconiosis (in particular siderosis), of cancer of several types (e.g., liver, nasal, sinonasal and stomach) and of possible hearing loss because of the combined effect of noise and exposure to carbon monoxide.

2. The shoulders and the neck of a welder may be heavily exposed to sparks and heat.

3. Exposure to welding fumes constitutes the major chemical hazard during welding by processes of most types. Such fumes are formed in the air upon cooling and condensation of substances volatilized by the heat of the welding process, from the base metals being welded, from electrodes, filler rods, fluxes, electrode coatings, etc. used in the process, as well as from “extraneous” materials such as metal or paint coatings on the base metal, residues of cleaning materials, etc. As a rule, the particle size of fumes is in the micron or submicron range, but such particles may coalesce and form larger aggregates. Most fume particles are in the “respirable” category, and may thus penetrate deep into the respiratory system and be deposited there. Welding fumes normally contain oxides of the metals being welded (in particular, in the case of steel, iron, chromium, nickel, manganese, vanadium and other oxides) and of the electrodes, silica, alumina, magnesia, alkali- and alkali-earth oxides (in particular baria) and may contain substantial amounts of fluorides, paint, oil and solvent residues or decomposition products. Fumes produced when using thoriated electrodes contain thorium oxide. In the welding of non-ferrous metals, the fumes may contain oxides of the metals being welded and small amounts of highly poisonous impurities such as arsenic and antimony compounds. The amount of fumes formed depends on the type of welding process, but may be as high as 2-3 g/min or even more (e.g., in manual arc welding or in welding with flux-cored electrodes).