How does argon affect a person when welding and how to provide first aid to victims of argon?

General information

Argon is an inert monatomic gas without color, taste or smell.
The third most abundant element in the earth's atmosphere (after nitrogen and oxygen) is 0.93% by volume and 1.29% by mass. Argon is the most common inert gas in the earth's atmosphere; 1 m3 of air contains 9.34 liters of argon (for comparison: the same volume of air contains 18.2 cm3 of neon, 5.2 cm3 of helium, 1.1 cm3 of krypton, 0. 09 cm3 xenon). There is argon in water, up to 0.3 cm3 per liter of sea water and up to 0.55 cm3 per liter of fresh water. Its average content in the earth's crust (clark) is 0.04 g per ton, which is 14 times more than helium and 57 times more than neon. It turns out that there is much more argon on Earth than all the other elements of its group combined. The argon content of the world's matter is estimated at approximately 0.02% by mass. Argon (along with neon) is observed on some stars and in planetary nebulae. In general, there is more of it in space than calcium, phosphorus, and chlorine, while on Earth the opposite relationships exist.

Symptoms and signs

First of all, aluminum is very harmful to the central nervous system, and the symptoms of aluminum poisoning are most often manifested by its neurotoxic effects.

With prolonged exposure to these salts, the following symptoms appear:

• convulsions occur;
• decreased memory and concentration;
• a depressive state occurs;
• Loss of motor coordination develops.

and this condition is called toxic encephalopathy. The role of aluminum intoxication in the occurrence of a serious personality-destroying disease—Alzheimer’s disease—is still being debated.

Chronic aluminum intoxication causes disruption of the extrapyramidal nervous system, which controls unconscious motor activity and muscle tone. Long-term exposure of nervous tissue to aluminum impairs its trophism and leads to the development of neurodegenerative changes.

In case of acute poisoning with aluminum and its compounds, the patient develops symptoms:

• lethargy;
• possible loss of consciousness;
• development of a coma.

In case of chronic intoxication with this metal in a patient:

• speech disorders occur in the form of stuttering;
• impairment of voluntary motor skills.

These signs appear quite early. Late symptoms of aluminum intoxication will include the presence of signs:

• chronic speech disorder;
• convulsive syndrome;
• personality changes with the development of dementia and memory loss;
• complete breakdown of motor skills.

In childhood, excess aluminum, which most often occurs with frequent consumption of juice bags, contributes to the development of increased motor activity, excitability, and headaches. In schoolchildren, excess aluminum leads to aggressiveness, memory disorders and learning difficulties.

In addition to the central nervous system, aluminum also affects the human skeleton. The harm of aluminum to bones is that it competes with calcium and displaces it from normal bone tissue into the blood. As a result, a person’s number of active cells – osteoblasts, which synthesize and renew bone tissue – decreases. With prolonged exposure to aluminum, bones soften, which leads to pathological fractures and dental problems - fluorosis.

Dental fluorosis is also a consequence of long-term aluminum intoxication

In the clinic, this is manifested by bone pain and muscle weakness in the legs, and fractures appear in the later stages. When taking tests, an increase in calcium in the blood serum becomes noticeable, since aluminum simply “drives” it out of the bones, as well as an increase in aluminum itself. Bone mineralization decreases, this is clearly visible when conducting a study such as densitometry.

The photo shows the results of a blood test, which shows that the calcium level in the blood is increased

Doctors especially note the harm of aluminum to the health of pregnant women. Nursing mothers who worked in aluminum production and suffered from chronic occupational intoxication passed this metal to their children through breast milk. According to research results, they were lagged behind in growth and development, their nervous system was less developed than their peers. Therefore, modern European recommendations advise limiting or eliminating medications for heartburn and peptic ulcers that contain compounds of this metal, and not using them in pregnant and nursing mothers.

The harm of aluminum to the human body is that it suppresses the immune system. Under its influence, lymphocytes reduce activity and begin to multiply poorly. Due to suppressed immunity, an allergy to aluminum occurs, and not only to it. This metal causes suppression of the immune response and contributes to the activation of various autoimmune diseases in the elderly. These include pathologies such as rheumatoid arthritis, severe psoriasis and systemic scleroderma.

Signs of aluminum phosphide poisoning include the toxic effect of phosphine. This is a very poisonous gas, its smell of rotten fish is felt at a concentration of 2 mg per cubic meter, and if phosphine is inhaled for a long time at a concentration of 10 mg per cubic meter, it can be fatal. In acute phosphine poisoning, there are no specific symptoms; they can even be confused with the flu and food poisoning.

Aluminum phosphide tablets

Typically, breathing becomes difficult, dizziness, nausea and vomiting occur, headaches and convulsions occur. Abdominal pain occurs and a cough appears. In case of serious phosphine poisoning, the condition can be so severe that the person loses consciousness and death occurs from respiratory and cardiac arrest. It is very important to remember that symptoms of phosphine poisoning can occur up to two days after you stop using it as a pesticide or grain dressing.

Chemical properties

The name “argon” (from the Greek - lazy, slow, inactive) - emphasizes the most important property of the element - its chemical inactivity.

So far, only 2 chemical compounds of argon are known - argon hydrofluoride and CU(Ar)O, which exist at very low temperatures. In addition, argon forms excimer molecules, that is, molecules in which the excited electronic states are stable and the ground state is unstable. Also, with many substances, between the molecules of which there are hydrogen bonds (water, phenol, hydroquinone and others), it forms inclusion compounds (clathrates), where the argon atom, as a kind of “guest”, is located in the cavity formed in the crystal lattice by the molecules of the substance - owner.

Environmental issues of MIG/MAG welding

Details Details Published 10/24/2015 14:: 3003
The figure clearly shows that, despite the abundance of information about the dangers and harmfulness of welding processes, problems still exist. The operator, with his hands not protected from short-term ultraviolet radiation, demonstrates the operation of the welding head. I'd like to think that behind the scenes there is a welding shield, a local exhaust with air purification, or personal protective equipment against ozone for the operator's respiratory system.

MIG/MAG welding is performed both in carbon dioxide and in protective gas mixtures. The composition of the most commonly used mixtures and process characteristics are presented in Table 1.

Multicomponent gas mixtures containing argon have technical advantages over pure carbon dioxide and are confidently filling the welding technology market. And if the problems of working conditions and safety when welding in argon were previously focused only on defense enterprises, now they face welders in all industries.

The problem of photochemical reactions in the air surrounding the welding arc

More than forty years ago, it was established that the main source of dangerous and harmful factors in gas shielded welding is light radiation from argon ionized in the arc. The short ultraviolet emission peaks of ionized argon occur at 185.0, 194.1, 197.1 and 200.0 nm. This radiation is characteristic of the Sun in outer space. Only rays with a length of 290 nm reach the Earth's surface from the Sun; shorter ones are slowed down by the atmosphere. Absorption of a photon with a wavelength of ~ 100-1500 nm, which corresponds to an energy of 0.8-12.4 eV (80 - 1200 kJ/mol), causes a quantum transition of air molecules and substances contained in it from the ground electronic state to one of excited states, or photoionization - the removal of an electron and the formation of a radical cation, followed by so-called photochemical reactions. (Yu. S. Drugov, V. G. Berezkin. Gas chromatographic analysis of polluted air. - M.: Khimiya, 1981, 256 pp.).

The most active part of the radiation, up to 157 nm in length, is decelerated by air within a radius of 0.5 m from the center of the arc. Radiation with a length of up to 184 nm reaches a distance of up to 1 m and 212 nm reaches a distance of up to 10 m. When short-wave ultraviolet radiation is inhibited, photochemical reactions occur both with the main air gases and with a multicomponent mixture of workplace air pollutants containing many toxic substances belonging to chemical compounds of various classes. Currently, the most studied reactions are with molecular oxygen and nitrogen, with the formation of ozone and nitric oxide.

Ozone - O3, an allotropic form of oxygen, is a powerful oxidizing agent. Unlike the oxygen molecule, the ozone molecule consists of three atoms and has longer bonds between the oxygen atoms. In terms of its reactivity, ozone ranks second, second only to fluorine. Due to its chemical activity, ozone has a very low maximum permissible concentration in the air (comparable to the maximum permissible concentration of chemical warfare agents) of 5·10-8% or 0.1 mg/m3, which is 10 times the olfactory threshold for humans. In other words, if you smell ozone, there is ten times more ozone in the room than is allowed by sanitary standards. Ozone is a gas that is toxic if inhaled. It irritates the mucous membrane of the eyes and respiratory tract, and damages lung tissue. High toxic concentrations of ozone cause respiratory irritation, coughing and dizziness.

Nitric oxide – NO. In air it quickly oxidizes into nitrogen dioxide - NO2, which plays a major role in oxide poisoning. The maximum permissible concentration is 2 mg/m3 (average daily 0.04 mg/m3). Nitrogen oxides cause damage to the deep parts of the airways, and in severe cases, pulmonary edema. Changes in the upper respiratory tract are weakly expressed.

Poisoning with ozone and nitrogen oxides at high concentrations can also lead to death, and death occurs as a result of respiratory paralysis.

The air in industrial premises almost always contains carbon-containing impurities, which enter the premises where welding is carried out, either with atmospheric air, or from a number of degreasing, painting, plastic processing, thermal processes and foundry operations.

Molecules of organic substances excited by light can enter into various chemical reactions. In this case, the activity of the resulting compounds may be higher than in their ground state. As a result, unusual chemical transformations occur that are not characteristic of substances in an unexcited state. The toxicology of the resulting compounds has not yet been studied. But, for example, it is known that the combined photochemical oxidation of hydrocarbons and nitrogen oxides leads to the formation of toxic substances of the PAN group (peroxyacetyl nitrate, etc.). Already at a concentration of 0.2 mg/m3, these substances have a strong tear effect, damage plants and destroy rubber. In higher concentrations, they, like ozone and nitrogen oxides, are dangerous to the lungs.

The distribution of toxic substances formed as a result of photochemical reactions at welding workplaces has been practically not studied. Individual information about cases of acute poisoning with damage to the lungs due to poor ventilation has not been systematized. According to our observations, when welding titanium alloys with a consumable electrode in argon, the ozone concentration at workplaces varied from 8 to 30 MAC. All workers wore respiratory protection. As a result, after 6 hours of work, only moderate fluctuations in the functions of the cardiovascular and autonomic nervous systems were noted without pronounced changes in the lungs.

It is worth recalling that short ultraviolet radiation itself is dangerous for a living organism. It causes malignant changes in skin cells, kills not only bacteria and fungi, but also plant cells. There is no short ultraviolet radiation in the space around us. It is retained by the atmosphere, which protects all life on Earth from the harmful radiation of the Sun. The aggressiveness of UV radiation is evidenced by the fact that during mass welding of titanium products due to reflected ultraviolet radiation, welders, despite the presence of appropriate protective equipment and protective clothing, in 16% had persistent irritation of the skin of the chest and forearms (erythema) and at least 1 - 2 Once a year, each of them went to the health center to instill painkillers and disinfectant drops into their eyes.

The problem of the formation of biologically active substances in the welding arc zone

During jet protection with a mixture of argon and carbon dioxide, about 3 - 6% of atmospheric air enters the arc zone. Gases dissolved in the metal are released into it.

Research carried out at Mogilev State Technical University has determined that in the arc zone in the temperature range of 1000 – 6000 K, the synthesis of biologically active substances (BAS) is possible - CN, HCN, NO2, N2O, CO, which enter the air of the working area. The lowest concentration of biologically active substances is formed when welding in pure argon and when welding in a mixture of Ar + 5% O2. The greatest - when welding in a mixture of Ar + CO2 (E. A. Lupacheva. Formation of biologically active substances in the arc combustion zone during welding in shielding gases. Proceedings of the 1st International Scientific and Practical Conference. Environmental protection, health. Safety in welding production. September 11-14, 2002. – Odessa, pp. 456-466).

The problem of pure, non-oxidized metal vapors

Argon is known to be chemically inert. In the weld pool, the metal is heated to a temperature above the melting point. In peripheral areas it is close to the melting temperature of the metal, and in areas under the influence of an electric arc it is much higher. When welding low-carbon steel, the lowest weld pool temperature is 1530°C, the highest is about 2300°C, and the average is about 1800°C. Boiling point 2750°C. A constant flow of argon reduces the temperature above the surface of the bath, as a result of which the evaporated part of the base metal and components, having passed through the inert layer of argon without oxidizing, enters the external environment with the heat flow. The diameter of metal aerosol particles varies in the range of 0.1-0.5 microns, the diameter of agglomerates is 5-10 microns, and the specific geometric surface is 2.1-2.5 m2/g.

The problem of the formation of aerosols of non-oxidized metals in a stream of protective gas is important both for ensuring the safety of work and for solving the environmental safety of welding through the disposal of the resulting highly dispersed aerosols of metals. All unoxidized metals are flammable (Table 2).

For example, when welding galvanized steel in a mixture of argon and carbon dioxide, zinc vapor, without oxidizing, concentrated on the surface of the polyester filter. At the same time, the concentration of zinc in the aerosol was 18%. We have determined that compacted welding dust, when exposed to open fire, smolders (red hot temperature) until complete oxidation with the formation of white smoke of zinc oxide. The figure shows the consequences of melting of the filter cassette as a result of smoldering welding dust.

When welding copper-nickel tubes for steam generators at Sevmashpredpriyatiya in an argon environment, the formation of shiny particles of unoxidized aerosol, visible in the transmitted light of the arc, was observed. To determine the chemical composition of the aerosol, it was necessary to refine the determination method by collecting dust with additional oxidation of metallic nickel in a Rychter liquid absorber filled with nitric acid.

Noise problem

During jet transfer of metal in an arc, sound vibrations are excited in a gas bubble. The noise of the welding arc in a production environment is practically inaudible due to the noise of hand tools, ventilation noise and other equipment. However, as can be seen from the figure, it approaches the line of permissible levels in the most dangerous high-frequency region for hearing. (The straight line in the figure is the limit of the noise limit at these frequencies according to SN .2.4/2.1.8.562-96).

conclusions

1. When the short ultraviolet radiation emitted by argon is inhibited, photochemical reactions occur both with the main air gases and with a multicomponent mixture of air pollutants in workplaces containing many toxic substances belonging to chemical compounds of various classes. Currently, the most studied reactions are with molecular oxygen and nitrogen, with the formation of ozone and nitric oxide.

2. Short ultraviolet radiation is dangerous for living organisms and affects the eyes and unprotected skin.

3. In a jet of protective gas in the arc zone, it is possible to synthesize biologically active substances (BAS) - CN, HCN, NO2, N2O, CO, which enter the air of the working area. The lowest concentration of biologically active substances is formed when welding in pure argon and when welding in a mixture of Ar + 5% O2. The greatest is when welding in a mixture of Ar + CO2.

4. Aerosols of non-oxidized metals pose a fire hazard if they accumulate in filter materials.

5. MIG/MAG welding produces high frequency noise, often masked by the noise of the production equipment.

Recommendations

1. No MIG/MAG welding should be performed without effective local exhaust ventilation and dust collection.

2. As filtration installations, installations with filters for purifying air from gases are preferred.

3. Filter installations must be protected from ignition sources of non-oxidized dust.

4. When welding, it is necessary to shield the welding arc as much as possible, using portable screens that are transparent to visible light.

5. Welding workplaces must be screened from other rooms, with the installation of screens that are opaque to ultraviolet radiation.

6. It is advisable to take measures to reduce the level of reflected ultraviolet radiation by using zinc oxide based paints that absorb UV radiation.

7. No MIG/MAG welding should be performed without personal protective equipment - welding shields with variable optical density, hand protection, tightly closed protective clothing and noise-muffs.

8. In case of increased sensitivity to the air of the working area, even with positive results of the air analysis, it is advisable to use additional respiratory protection - special respirators for welders that protect against ozone.

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Receipt

Argon is produced as a by-product when air is separated into oxygen and nitrogen. Typically, double rectification air separation devices are used, consisting of a lower high-pressure column (pre-separation), an upper low-pressure column and an intermediate condenser-evaporator. Ultimately, nitrogen is removed from above, and oxygen from the space above the condenser. The volatility of argon is greater than that of oxygen, but less than that of nitrogen. Therefore, the argon fraction is selected at a point located approximately at a third of the height of the upper column and taken to a special column. Next comes the purification of “raw” argon from oxygen (chemically or by adsorption) and from nitrogen (by rectification).

Aluminum compounds and their harm

Some aluminum compounds can cause acute intoxication. These are highly soluble salts such as sulfate, chloride and nitrate. At the same time, aluminum sulfate is used in small quantities in the food industry. Aluminum hydroxide can be both beneficial and harmful; it is a base and exhibits harmful effects by stimulating hemolytic action and destroying red blood cells.

Aluminum dust (or aluminum powder)

Metallic aluminum itself has moderate toxicity, and the harm from chronic inhalation of aluminum dust is especially great. This method of intoxication is industrial. If you inhale aluminum dust, beryllium dust and bronze dust containing element No. 13, then after a month signs of inflammation appear in the lungs, emphysema and diffuse pneumosclerosis occur. Inhalation of aluminum nitride also leads to inflammation of the bronchi, pneumosclerosis, and degeneration of liver cells.

Welding an aluminum boat hull

Also, inhalation of aluminum vapor causes harm to the central nervous system, and with prolonged exposure to this toxic factor, characteristic clinical symptoms arise, described below, so aluminum welding specialists are at risk. The resulting vapors of aluminum and its compounds cause significant harm to health. If you inhale the aerosol released during welding for 3 hours every day, then, in the end, the connective tissue in the lungs also grows and pulmonary ventilation decreases, and in high concentrations the aerosol causes severe pneumonia.

Aluminum chlorohydrate is also harmful, but this compound will be discussed below, since it is part of cosmetic preparations. Many cosmetics also contain a compound such as aluminum chloride: it is widely used as a catalyst in organic synthesis, and it is also an industrial poison when it enters the body, causing serious harm to health.

Aluminum chloride (aluminum chloride)

Even clay dust can damage the epithelium of the respiratory tract; it causes degeneration of the cartilaginous skeleton of the bronchi with the development of necrosis and focal sclerosis. Inhalation of dust that accumulates near the smelting furnaces in which metal is produced, after a few months, leads to the growth of connective tissue in the lungs with the development of fibrosis, and after a year, scars and adhesions develop in the lung tissue.

Aluminum phosphide is used as a pesticide, but this compound is unstable, and when it reacts with water, it breaks down, releasing poisonous phosphine - a gas consisting of phosphorus and hydrogen, with the smell of rotten fish.

Aluminum oxide, which coats a fresh metal surface, is also harmful to health. All utensils made of this metal are covered with an oxide film, since the metal oxidizes very quickly in the air and the oxygen it contains. There is also a completely non-toxic aluminum oxide found in nature. This is corundum, and especially rubies and sapphires. They are extremely persistent and do not affect our health in any way. But dishes made from this “heavenly” metal are quite toxic under certain conditions, and this is discussed below.

Classification of argon by grade

Argon provides good protection for the weld pool. Depending on the purpose and content, this gas is divided into three grades. The highest grade of argon (99.99% Ar) is used for welding chemically active metals, zirconium, titanium alloys, molybdenum, alloys based on them, and critical structures made of stainless steels. The first grade of argon (99.98% Ar) is used for welding with non-consumable electrodes, magnesium, aluminum, magnesium and aluminum alloys, which are less sensitive to oxygen and nitrogen impurities. The second grade of argon (99.95% Ar) is used for welding stainless steels, heat-resistant alloys and pure aluminum. Mixtures of argon with other gases (oxygen, carbon dioxide) can also be used for welding.

Rules for working with electric welding

The welding process is the most powerful in producing infrared radiation. You don’t even have to go to the solarium, just put the mask and overalls aside and cook without them. Moreover, novice welders pay little attention to this, and think that if they have protected their eyes, then they don’t even need to cover the rest, open parts of the body.

Therefore, the first and main rule when working with electric welding is to reliably protect the eyes and open parts of the body from the harmful effects of ultraviolet radiation. Fortunately, today you can buy very high-quality workwear and automatic masks for welding, which will help protect your eyes from electroophthalmia and visual impairment from welding.

The chemical factor, which was already mentioned above in this article on the site about manual arc welding mmasvarka.ru, also causes no less harm to the welder. Welding in a closed room, and even without good ventilation, can lead to poisoning by combustion products of metals and electrode coating.

That is why welding work should be carried out outdoors or in rooms with good ventilation. At the same time, it is important not to forget about fire safety rules when welding, which in no case should be neglected.

History of discovery

The history of the discovery of argon begins in 1785, when the English physicist and chemist Henry Cavendish, studying the composition of air, decided to determine whether all the nitrogen in the air was oxidized.

The further history of the discovery of argon is associated with the name of Rayleigh, who devoted several years to studying the density of gases, especially nitrogen.

The already famous English chemist William Ramsay also did not have a ready answer, but he offered Rayleigh his cooperation. Intuition prompted Ramsay to suggest that the nitrogen in the air contains admixtures of an unknown and heavier gas, and Dewar drew Rayleigh’s attention to the description of Cavendish’s ancient experiments (which had already been published by this time).

Spectral analysis played a major role in the study of the new gas. The spectrum of the gas released from the air, with its characteristic orange, blue and green lines, was sharply different from the spectra of already known gases. William Crookes, one of the most prominent spectroscopists of that time, counted almost 200 lines in its spectrum. The level of development of spectral analysis at that time did not make it possible to determine whether the observed spectrum belonged to one or more elements. A few years later, it turned out that Ramsay and Rayleigh were holding in their hands not just one stranger, but several - a whole galaxy of inert gases.

On August 7, 1894, in Oxford, at a meeting of the British Association of Physicists, Chemists and Naturalists, a report was made on the discovery of a new element, which was named argon.

Isotopes

Argon is represented in the earth's atmosphere by three stable isotopes: 36Ar (0.337%), 38Ar (0.063%), 40Ar (99.600%). Almost the entire mass of the heavy isotope 40Ar arose on Earth as a result of the decay of the radioactive isotope of potassium 40K (the content of this isotope in igneous rocks averages 3.1 g/t). The decay of radioactive potassium occurs in two directions simultaneously:

The first process (ordinary β-decay) occurs in 88% of cases and leads to the formation of a stable isotope of calcium. In the second process, where 12% of the atoms participate, electron capture occurs, resulting in the formation of a heavy isotope of argon. One ton of potassium contained in rocks or waters generates approximately 3,100 argon atoms over the course of a year. Thus, 40Ar gradually accumulates in minerals containing potassium, which makes it possible to measure the age of rocks; The potassium-argon method is one of the main methods of nuclear geochronology. The probable sources of origin of the 36Ar and 38Ar isotopes are unstable products of the spontaneous fission of heavy nuclei, as well as the reaction of capture of neutrons and alpha particles by the nuclei of light elements contained in uranium-thorium minerals. The overwhelming majority of cosmic argon consists of the isotopes 36Ar and 38Ar. This is due to the fact that potassium is approximately 50,000 times less abundant in space than argon (on Earth, potassium predominates over argon by 660 times). The calculation made by geochemists is noteworthy: by subtracting radiogenic 40Ar from the argon of the earth's atmosphere, they obtained an isotopic composition very close to the composition of cosmic argon.

Technical requirements

Argon gas. Highest grade GOST 10157-79 as amended. 1, 2, 3

Argon gas of high purity TU 6-21-12-94

Liquid argon High grade GOST 10157-79 as amended. 1, 2, 3

Argon gas is transported in steel cylinders (GOST 949-73) of gray or black color under a pressure of 150 kgf/cm². For transportation by road, medium-volume cylinders are placed in special metal containers (pallets).

Liquid argon is poured into special tanks with powder, vacuum-powder or vacuum-multilayer insulation intended for the transportation of liquid argon.