Safety issues
Welding, without the proper precautions, can be a dangerous and unhealthy practice. However, with the use of new technology and proper protection, the risks of injury and death associated with welding can be greatly reduced. Because many common welding procedures involve an open electric arc or flame, the risk of burns is significant. To prevent them, welders wear protective clothing in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat and flames. Additionally, the brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes the inflammation of the cornea and can burn the retinas of the eyes. Goggles and helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced that feature a face plate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, transparent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets.
Welders are also often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce various gases, most commonly carbon dioxide and ozone, and fumes that can prove dangerous if ventilation is inadequate. Furthermore, because the use of compressed gases and flames in many welding processes pose an explosion and fire risk, some common precautions include limiting the amount of oxygen in the air and keeping combustible materials away from the workplace.
After reading activity
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Match the terms and their meaning
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current in an electrical conductor. |
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3. Flux |
C Electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. |
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4. Welding |
D (from the Greek avo5o<; = 'going up') is the electrode in a device that electrons flow out of to return to the circuit. Literally, the path through which the electrons ascend out of an electrolyte solution. The other charged electrode in the same cell or device is the cathode. |
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5. Alternating current (AC) |
E In metallurgy, a substance which facilitates soldering, brazing, and welding by chemically cleaning the metals to be joined. Common..s are: ammonium chloride or rosin for soldering tin; hydrochloric acid and zinc chloride for soldering galvanized iron (and other zinc surfaces); and borax for brazing, and welding ferrous metals. |
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6. Carbon dioxide |
F Atmospheric gas comprised of one carbon and two oxygen atoms. A very widely known chemical compound, it is often referred to by its formula CO2. It is present in the Earth's atmosphere at a low concentration and acts as a greenhouse gas. In its solid state, it is called dry ice. It is a major component of the carbon cycle. |
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7. Oxidation |
G Loss of an electron by a molecule, atom or ion |
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8. Goggles and safety glasses |
H (Formerly wolfram) is a chemical element that has the symbol W (L. wolframium) and atomic number 74. A very hard, heavy, steel-gray to white transition metal, it is found in several ores including wolframite and scheelite and is remarkable for its robust physical properties, especially the fact that it has a higher melting point than any other nonalloy in existence. The pure form is used mainly in electrical applications but its many compounds and alloys are widely used in many applications (most notably in light bulb filaments, and as both the filament and target in most X-ray tubes and in space-age superalloys). |
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9. Ozone |
I In metallurgy a ferrous alloy with a minimum of 10% chromium content. The name originates from the fact that it does not stain, corrode or rust as easily as ordinary steel. This material is also called corrosion resistant steel when it is not detailed exactly to its alloy type and grade, particularly in the aviation industry. |
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10. Toxicity |
J also known as arc flash, welder's flash, corneal flash |
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burns, or flash burns, is a painful ocular condition sometimes experienced by welders who have failed to use adequate eye protection. It can also occur due to light from sunbeds, light reflected from snow (known as snow blindness), water or sand. The intense ultraviolet light emitted by the arc causes a superficial and painful keratitis. |
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11. Stainless steel |
K Triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic species O2. It is a pale blue gas at standard temperature and pressure. It forms a dark blue liquid below -112 °C and a dark blue solid below -193 °C. A powerful oxidizing agent. It is also unstable, decaying to ordinary diatomic oxygen: 2 O3 ^ 3 O2. |
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12. Arc eye |
L From Greek то^гкот^та - poisonousness). It can refer to the effect on a whole organism, such as a human or a bacterium or a plant, or to a substructure, such as the liver. By extension, the word may be metaphorically used to describe toxic effects on larger and more complex groups, such as the family unit or "society at large". The skull and crossbones is a common symbol for it. |
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13. Tungsten |
M Forms of protective eyewear that usually enclose or protect the eye area in order to prevent particulates or chemicals from striking the eyes. They are used in chemistry laboratories and in woodworking. They are often used in snow sports as well, and in swimming. Goggles are often worn when using power tools such as drills or chainsaws to prevent flying particles from damaging the eyes. |
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14. Voltage |
N Electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. |
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Speaking |
True or false?
1. Filler material is always necessary for arc welding.
2. The amount of heat input at the welding point depends on the voltage.
3. Shielded metal arc welding is a consumable electrode process.
4. Consumable welding processes use any type of current.
5. Consumable electrode methods are faster than none-consumable ones.
6. TIG welding requires little operator training.
Answer the following questions and summarize the text:
1. What is arc welding?
2. What kind of current and electrodes are used in arc welding?
3. What is the welded region protected by?
4. Why is constant current power supply most often used for manual welding processes?
5. How does the type of the electrode charge (positive/negative) influence the speed of welding and weld penetration?
6. What problem is related to the use of alternating current in gas tungsten welding?
7. What is the function of flux in shielded metal arc welding?
8. What are the main advantages and disadvantages of manual metal arc welding?
9. Which type of metal arc welding uses a separate filler material?
10. What do the welding protection clothes include?
Translate the following sentences from Russian into English:
1. Зона сварки при электродуговых процессах защищается защитным газом.
2. При сварке с использованием плавящихся электродов используется как постоянный, так и переменный ток.
3. При РДС электрод является присадочным материалом.
4. Благодаря разнообразию способов электродуговой сварки она находит широкое применение в различных отраслях производства.
5. Для защиты сварщиков от ультрафиолетового излучения электрической дуги используются светофильтры.
6. При недостаточной вентиляции газы могут представлять опасность для здоровья.
7. Благодаря отсутствию дыма при дуговой сварке под флюсом условия труда гораздо лучше, чем при других способах электродуговой сварки.
8. В целях предосторожности не следует держать воспламеняющиеся предметы вблизи проведения сварочных работ.
Reading
Below find information about some less frequently used arc welding processes. After reading the text, think and say why these processes are less common in industry. Consider their advantages and disadvantages.
Atomic Hydrogen Welding (AHW) is an arc welding process that uses an arc between two metal tungsten electrodes in a shielding atmosphere of hydrogen and without the application of pressure. Shielding is obtained from the hydrogen. Filler metal may or may not be used. In this process, the arc is maintained entirely independent of the work or parts being welded. The work is a part of the electrical circuit only to the extent that a portion of the arc comes in contact with the work, at which time a voltage exists between the work and each electrode.
Carbon Arc Welding (CAW) is a process which produces coalescence of metals by heating them with an arc between a nonconsumable carbon (graphite) electrode and the work-piece. It was the first arc-welding process ever developed but is not used for many applications today, having been replaced by twin carbon arc welding and other variations.
Twin carbon arc welding (TCAW) in which the arc is established between two carbon electrodes
Gas carbon arc welding (CAW-G) no longer has commercial significance Electroslag welding is a highly productive welding process developed in the United States during the 1930s. It involves the melting of the surfaces of the metal workpieces and the filler metal with a molten slag to cause coalescence. An electric arc is passed through the slag to heat it, but the arc itself is extinguished by the slag. Electroslag welding is commonly used to weld in a vertical orientation, and is particularly popular with steels. In the 1970s, it was used extensively in bridges, ships, and other large metal structures. However, in 1977 the Federal Highway Administration banned its use in welds for some structural members of bridges, due to concerns of weld imperfections and poor properties. Benefits of the process include its high metal deposition rates. Many welding processes require more than one pass for welding thick workpieces, but often a single pass is sufficient for electroslag welding. The process is also very efficient, since joint preparation and materials handling are minimized while filler metal utilization is high. The process is also safe and clean, with no arc flash and low weld splatter or distortion.
Electrogas welding (EGW) is a continuous vertical position arc welding process developed in 1961, in which an arc is struck between a consumable electrode and the workpiece. A shielding gas is sometimes used, but pressure
is not applied. A major difference between EGW and its cousin electroslag welding is that the arc in EGW is not extinguished, instead remaining struck throughout the welding process. It is used to make square-groove welds for butt and welding, especially in the shipbuilding industry and in the construction of storage tanks. In EGW, the heat of the welding arc causes the electrode and workpieces to melt and flow into the cavity between the parts being welded. This molten metal solidifies from the bottom up, joining the parts being welded together. The weld area is protected from atmospheric contamination by a separate shielding gas, or by the gas produced by the disintegration of a flux-cored electrode wire. The electrode is guided into the weld area by either a consumable electrode guide tube, like the one used in electroslag welding, or a moving head. When the consumable guide tube is used, the weld pool is composed of molten metal coming from the parts being welded, the electrode, and the guide tube. The moving head variation uses an assembly of an electrode guide tube which travels upwards as the weld is laid, keeping it from melting. Electrogas welding can be applied to most steels, including low and medium carbon steels, low alloy high strength steels, and some stainless steels. Quenched and tempered steels may also be welded by the process, provided that the proper amount of heat is applied. Welds must be vertical, varying to either side by a maximum of 15 degrees. Like other arc welding processes, EGW requires that the operator wear a welding helmet and proper attire to prevent exposure to molten metal and the bright welding arc. Compared to other processes, a large amount of molten metal is present during welding, and this poses an additional safety and fire hazard. Since the process is often performed at great heights, the work and equipment must be properly secured, and the operator should wear a safety harness to prevent injury in the event of a fall. EGW uses a constant voltage, direct current welding power supply, and the electrode has positive polarity. A wire feeder is used to supply the electrode, which is selected based on the material being welded. The electrode can be flux-cored to provide the weld with protection from atmospheric contamination, or a shielding gas can be used with a solid wire electrode. The welding head is attached to an apparatus that elevates during the welding process. Also attached to the apparatus are backing shoes which restrain the weld to the width of the workpieces. To prevent them from melting, they are made of copper and are water-cooled. They must be fit tightly against the joint to prevent leaks.
Stud welding is a form of spot welding where a bolt or specially formed nut is welded on to another metal part. The bolts may be automatically fed into the spot welder. Weld nuts generally have a flange with small nubs that melt to form the weld. Studs have a necked down, unthreaded area for the same purpose.
Speaking
True or false
1. Electrogas welding is less hazardous than electroslag welding.
2. Electroslag welding is more frequently used to weld in a horizontal orientation.
3. Carbon Arc Welding is broadly used in industry in the present time.
4. Filler metal is always necessary in Atomic Hydrogen Welding.
5. Quenched and tempered steels are not welded using Electrogas welding.
6. Carbon Arc Welding is the newest arc welding process.
Answer the following questions:
1. What kind of electrodes are used in Electrogas and Atomic Hydrogen Welding processes?
2. What structures can be welded by Electrogas welding?
3. Can thick workpieces be easily welded by Electroslag welding?
4. Why is Electrogas welding relatively unsafe and hazardous?
5. What is the difference between Electrogas and Electroslag welding?
6. Why does the operator have to wear protective clothes?
Complete the following sentences:
1. To ensure safety while using arc welding processed operators have to wear. .
2. Electroslag welding is no more used to weld. .
3. In Electrogas welding the weld area is protected from atmospheric contamination. .
4. In Atomic Hydrogen Welding the work itself becomes. .
5. Since Electrogas welding is performed at great heigh. .
Writing
Write a short report arc welding mentioning:
Types (SMAW, MMA, GMAW, MIG, FCAW, SAW, GTAW, TIG, electroslag welding, stud arc welding, EGW, TCAW);
Types of filler material used (consumable/none-consumable, covered/bare electrode/wire);
Type of current used (direct/alternating);
Type of shielding gas used (helium, argon, CO2);
Try to answer the following questions:
What is the difference in methods of gas gutting and gas welding?
Is there any difference in equipment used for gas welding and gas cutting? What might be the advantages and disadvantages of gas cutting compared to other methods of cutting metals?
Do you remember what appeared before: arc or gas welding?
What type of cutting (arc or gas) is :
a) more expensive
b) more operator skills demanding
c) safer
e) faster
f) more precise?
Present your arguments.
Do you know what metals (steels) are better cut using gas welding?
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Vocabulary |
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rig |
какое-л. приспособление, устройство, механизм Syn: apparatus, device |
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hose |
шланг |
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spark |
искра |
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igniter |
воспламенитель |
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wrench |
гаечный ключ |
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outfit |
агрегат; оборудование, принадлежности, набор (приборов, инструментов) |
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pressure gauge |
манометр |
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leak |
течь, протечка; утечка |
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orifice |
отверстие |
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single-stage (regulator) |
однокамерный |
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flashback |
обратный удар пламени (проникающий в шланг сварочной горелки) |
Reading
