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Manual Arc Welding
2019-07-27

Hand arc welding is a manually operated welding method that uses the heat generated by the arc to melt and weld the electrode.

YISHANG -Hand Arc Welding

Advantages:

It has the characteristics of convenience and flexibility and good welding quality.


Disadvantages:

1. Slow speed and large smoke.

2, suitable for welding all positions.

3, welding fume

1) Possible occupational diseases: welder pneumoconiosis

2) Industry examples:

Sporting goods manufacturing industry: copper pipe punching

Mechanical industry: manual arc welding, gas shielded welding, argon arc welding, carbon arc gouging, gas welding

Transportation equipment manufacturing: assembly of locomotive components, platform assembly, ship piping installation, ship electrical installation, ship anchor chain, etc.

YISHANG -Hand Arc Welding-1

Influencing factors

There are many health hazards in electric welding operations, which can be divided into two major categories: physical factors and chemical factors. The former has ultraviolet rays, infrared rays, and the like generated by high-temperature arc light. The latter is a variety of components of electric welding aerosols. There are various metals such as iron, manganese, aluminum, chromium, lead, nickel, radioactive elements, etc., and gases such as manganese oxide, hydrogen fluoride, nitrogen oxides, etc. High temperature, vibration and noise are not very obvious.

The welding aerosol has a very high dispersion and biological activity is significantly higher than other dusts. The welding rod and welding method are different, the composition of the welding aerosol is also changed greatly, and the biological activity is also different [2]; the biological activity is also related to the solubility and freshness of the welding fume.


Damage to workers' health caused by electric welding

1. The influence of welder's pneumoconiosis and lung function

In arc welding, the welding core, the coating and the metal base material in the welding rod melt, evaporate, oxidize and agglomerate at high temperature of the arc, and generate a large amount of smoke of metal oxides and other substances, which may cause welder pneumoconiosis during long-term inhalation. The electric welder's pneumoconiosis usually occurs under closed and poorly ventilated operating conditions, and the average age of onset is about 18 years [3]. Pulmonary ventilation function test showed that exposure to electric welding dust can cause a certain degree of lung ventilation function damage, and the lung ventilation function indexes of FVC, FEV1.0, FEV1.0%, MMF, V50, V25, PEFR are significantly reduced [4]; Smoking factors and dust-removing factors may have synergistic effects on the welder's lung ventilation function; the welder's lung ventilation function damage has a tendency to increase with the extension of the dusting age [5].

2. Manganese poisoning

Various weldments and welding rods contain varying amounts of manganese. Generally, the manganese content in the core is very low, only about 0.3 to 0.6%. In order to improve the mechanical strength, wear resistance, corrosion resistance and other properties, the manganese content can be as high as 23% when using manganese-containing electrodes. In the poorly ventilated places such as cabins, boilers or closed containers, long-term inhalation of manganese-containing soot can cause manganese poisoning, which can detect hemorrhagic manganese, elevated urinary manganese, and changes in neurobehavioral function [6]. Early screening indicators for manganese poisoning.

3. Welding fume heat

Electric welding fume heat, also known as welder heat, is a kind of metal fume heat. The systemic disease caused by the increase of body temperature and the increase of peripheral blood leukocyte count caused by inhalation of metal oxides is often in contact with metal oxide. 6-12 hours after the smoke (8) onset, dizziness, fatigue, chest tightness, shortness of breath, muscle and joint pain, after fever, leukocytosis, severe chills, chills.

4. The impact on the nervous system

A large number of studies have shown that there are neurological damages related to occupational exposure in electric welding operations, mainly related to information processing and processing functions such as memory, analysis and localization, which are manifested as neurophysiological, neuropsychological, and neurobehavioral abnormalities [9], and in welding fume. Manganese, aluminum, lead, etc. are inextricably linked. Adopt WHO. In the NCTB test, the total score of behavioral function was negatively correlated with urinary manganese [10], suggesting that changes in neurobehavioral function can be used as an early indicator of prevention of manganese poisoning [11]. Foreign studies have reported that the total score of behavioral functions of electric welding workers is higher than that of the control group. The author's analysis may be caused by workers' health effects and work-related skills training effects [12]. The influence of electric welding on the function of workers' parasympathetic investigation has also been reported [13]. It has been reported in foreign countries that the age of onset of Parkinson's syndrome in the welder population is significantly earlier [14] (average 46 years, mean 63 years in the control group), suggesting that welding is one of the risk factors for Parkin's syndrome.

5. The impact on the eyes and skin

Ultraviolet (UVR) and infrared (IFR) damage to the eyes and skin is an important aspect of occupational damage in welding operations. The obvious increase in eye symptoms of electric welders has been reported, including electro-optic ophthalmia, chronic blepharitis, conjunctivitis, crystal opacity, etc., and the prevalence of chronic blepharitis and conjunctivitis has increased with the increase of working age [ 15]. The main damage to excessive UVR exposure is photosensitive keratitis, which is associated with infrared contact. Recent studies abroad have shown that exposure to excessive UVR by workers can lead to the risk of non-melanocyte skin cancer [16] and other chronic diseases such as malignant melanoma.

6. Impact on the reproductive system

The outcome of reproductive toxicity is of great significance. Therefore, in the past 10 years, some researches on reproductive toxicity of electric welding work have been carried out at home and abroad, mainly concerning male semen quality, female worker's reproductive outcome and damage mechanism. Studies have shown that: women with electric welding have increased menstrual flow, shortened cycle, prolonged menstruation, increased vaginal discharge, spontaneous abortion, premature delivery, and dysmenorrhea, which are higher than the control group [18]. The appearance of semen in manganese poisoning was uniform grayish white, the pH value was normal, and the average liquefaction time was longer than that of the control group. The test results showed that the average ejaculation, sperm count, sperm survival rate and active sperm rate of male workers with manganese poisoning were lower than those of the control group, and the sperm deformity rate of male workers with manganese poisoning was significantly higher than that of the control group [19]. It is believed that manganese metal can affect the male spermatogenesis system, has a direct toxic effect on sperm development, and can kill sperm, which causes changes in male semen quality. Foreign countries have also reported changes in sex hormone secretion in welders, and sperm quality has declined, but it has no effect on the sex ratio of offspring [20].

7. Effects on enzyme and antibody levels in the body

In recent years, there have been many reports on the effects of electric welding on the enzymes and antibodies in workers. Studies have shown that total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) in the welder's serum decreased significantly, and malondialdehyde (MDA) levels increased significantly, but did not exist. Dose-effect relationship, the electric welder in the oxidative stress state, the antioxidant capacity is weakened, suggesting that the biofilm is damaged.

In order to investigate the effect of welding fume on human immunoglobulin content, the IgG, IgA and IgM contents were determined by a one-way immuno-agar diffusion method for welders and healthy controls. The results showed that the difference of IgG and IgA in the electric welding group was significantly higher than that in the control group (P<0.001). The IgM content in the electric welding group was not significantly different from the control group (P>0.05); Manganese has a correlation with IgG and IgA, respectively r=0.982, r=0.991 [24], suggesting that welding fume has an effect on human immunoglobulin content.

Heat stress proteins (HSPs) are a group of evolutionarily highly conserved proteins that the body induces increased synthesis under various stress conditions. Under physiological conditions, they are necessary for cell survival, and the level of stress increases, which can improve the tolerance and stress ability of the running to damage the tissue cells to protect the harmful effects of the harmful cells. The body's own stability plays an important role. The level of HSP65 antibody in the welder plasma was detected by enzyme-linked immunosorbent assay. The results showed that the plasma antibody level of the welder was higher than that of the control group (P<0.05); the abnormal detection rate was 26.1%, and it was considered that the weld mixed dust can induce the synthesis of HSP65 antibody level in the body as a stressor [25]. Therefore, it is believed that the level of HSDP65 antibody in the welder's plasma can reflect the degree of damage caused by welding mixed dust to workers.

8. The impact on the internal organs

The effect of electric welding on the liver and spleen of workers was investigated by B-ultrasound. Results The left liver length and thickness of the workers in the electric welding group were higher than those of the control group, and there were significant differences. Electric welding has certain damage to the liver and spleen of workers, and it has a tendency to increase with the extension of working age [26]. It has been reported in foreign countries that the risk of pancreatic endocrine tumors in welders is also significantly higher than that of normal people.

9. The impact of trace elements in the body

It has been reported that plasma emission spectrometers are used to detect trace elements of Mn, Cu, Zn, Fe and Pb in the serum of manganese welding workers. Results The serum levels of manganese and iron in the contact group were significantly higher than those in the control group (P<0.05). The serum levels of zinc and lead were significantly lower than those in the control group (P<0.01). The working age and age of the contact group showed that each There were no statistically significant differences in serum trace elements. Conclusion: Excessive inhalation of manganese can affect the changes of trace elements in Mn, Cu, Zn, Fe and Pb, which cause imbalance of trace elements in the body and promote the occurrence of manganese poisoning [28]. It has been reported that the Mn content of erythrocyte in women with electric welding is higher than that of men, and the change of copper and zinc content in erythrocytes is positively correlated with manganese.

The degree of damage of argon arc welding is relatively larger than that of electrode arc welding, but it is not so large that it is daunting. The infrared radiation is about 1 to 1.5 times that of ordinary electrode arc welding. The ultraviolet radiation generated by argon arc welding arc is about For welding rod arc welding 5 to 30 times, when welding in a limited space, the concentration of ozone can be increased to a dangerous level. During the welding process, harmful gases such as carbon dioxide and carbon monoxide and metal dust are generated, which are generated by the welder. Certain hazards. Therefore, we must do a good job in the welding process, the material of the electrode should be selected, and the radioactive small tungsten-tungsten tungsten should be selected as much as possible. When grinding the electrode, wear a mask and gloves, and wash your hands after work; if you have a regular physical examination for a long time of welding, you will have a hold in your work, just like we are sunbathing and drying for a long time. It will be bad for people.

10. Electro-optic ophthalmia

Some people are swayed by electric welding during the day, and suddenly they can't open their eyes at night, and they have severe eye pain and tears. This is often electro-optic ophthalmia.

Arc welding of electric and gas welding, ultraviolet light, seashore and plateau of the sun, and solar reflection of snow-capped mountains can produce a large amount of ultraviolet rays and cause electro-optic ophthalmia, especially welders. The main manifestation of electro-optic limited inflammation is: after 2 to 12 hours of exposure to ultraviolet radiation, the corneal epithelium is damaged, the patient feels eye pain, is afraid of light, and the eyes are difficult to open. The eye pain is like many sand particles entering the eye. The object is very blurred. Ophthalmologic examination revealed hyperencephalia, red eyes, conjunctival congestion and edema, and corneal epithelial shedding. Although the condition of the electro-optic inflammatory disease is fierce, the prognosis is good. At the time of onset, topical anesthetics (such as 0.5% tetracaine) can be used 1 or 2 times to immediately eliminate the symptoms of eye pain, and use anti-inflammatory eye drops to prevent infection. With the rapid repair of the conjunctiva and corneal epithelium, it can be cured after 2 to 5 days.

In order to prevent electro-optic ophthalmia, the welder must wear a protective mask or glasses when operating. In addition, ultraviolet light after reflection from the plateau, snow or desert can also cause electro-optic ophthalmia, so it is also necessary to wear protective glasses.

Compared with electrode arc welding, argon arc welding has a higher degree of damage to the human body. As long as the protection is not harmful to the human body during work, we all know that the current density of argon arc welding is large and the light emitted is relatively strong. The ultraviolet radiation generated by its arc is about 5 to 30 times that of ordinary electrode arc welding, and the infrared ray is about 1 to 1.5 times that of electrode arc welding. The ozone content generated during welding is high. Therefore, try to choose air circulation. Local welding, the protection measures for argon arc welding are basically the same as those of hand arc welding. It is not necessary to say here. When welding, try to select electrode materials with less radioactivity of thorium tungsten and thorium tungsten. If conditions permit, it should be carried out regularly. Body checkup. Work should be done in the work and rest, usually pay attention to exercise, and participate in some sports activities, because the welder is a special operator, the degree of harm in the work is relatively higher than other types of work!


Operating procedures

1. Before the work, check the power cord of the welder, the lead wire and the joints are good. The crossover roadway should be overhead or add a protective cover. The secondary circuit and the outer casing of the welder must have good grounding, and the grounding resistance should not exceed 4 ohms; The clamping and insulation properties of the clamps must be good.

2. It is not allowed to be welded in the open air on rainy days. When working in wet areas, stand in a place with insulated materials and wear insulated shoes.

3. The work of the mobile or electric welder from the power network wiring or line inspection, grounding, etc. should be carried out by an electrician.

4. When pushing the knife switch, the body should be skewed. It is necessary to push the foot once and then turn on the welding machine; when stopping, the electric welding machine must be turned off before the power knife switch can be pulled off.

5. When moving the position of the welding machine, it is necessary to stop the power supply first, and the power supply suddenly stops during the welding. The welding machine should be closed immediately.

6. When welding in a crowded place, it is necessary to install a cover to block the arc. When there is no cover, the surrounding people should be reminded not to look directly at the arc.

7. Wear gloves when changing the electrode. Do not lean on the iron plate or other conductive objects. Wear protective goggles when knocking on the slag.

8. When welding non-ferrous metal devices, it is necessary to strengthen ventilation and detoxification, and if necessary, use a filter gas mask.

9. In the state where the welding tongs are short-circuited with the workpiece, the power switch should not be closed; when the work is stopped, the welding tongs should be separated from the workpiece. The welding tongs should be placed in a well-insulated place, and the power supply should only be cut off when not working.

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