Progress of environmental pollution and control te

Abstract: starting from the classification, causes, characteristics of environmental pollution factors in the welding workshop and the harm mechanism to the health of operators, and based on the full reference of relevant treatment technologies and design concepts at home and abroad, this paper puts forward corresponding treatment methods for the actual situation of general industrial enterprises in China. The development of environmental pollution control technology in welding workshop is prospected. The design principles of environmental pollution control engineering in welding workshop are put forward. It provides a scientific reference for improving the existing governance theory and improving the processing efficiency of the existing design

key words: prevention and control measures for pollution factors in the welding workshop

1 introduction

welding is a process method that uses electric energy to heat, promote the welded metal to be locally liquid or close to liquid, and combine them to form a solid and non removable joint. It is a very common mechanical process method in factories

there are many kinds of pollution and great harm in the welding process, which can lead to a variety of occupational diseases (such as silicosis of welders, manganese poisoning, electric flame retardation, which factors affect the accuracy of P testing machine reaching B1 and B2 levels, u thermal insulation material photoophthalmia, etc.), and has become a major environmental hazard. With the deepening of relevant research, the treatment technology is becoming more and more perfect, and the welding pollution has been relatively effectively controlled. Based on the specific situation of welding workshops in China, combined with the latest research results and practical technology at home and abroad, this paper puts forward practical prevention countermeasures from the formation, characteristics and harm of welding pollution

2 Analysis of the current situation of pollution control technology in welding workshops at home and abroad

the research on welding pollution in foreign countries began earlier than that in China, and the treatment technology is relatively advanced and mature. Welding pollution treatment equipment has developed from single, fixed and large-scale to complete set, combination, mobility, miniaturization and low resource consumption. For the treatment of the main polluted welding smoke and dust, local ventilation is the main method, supplemented by comprehensive ventilation, so as to improve the pollution of the working environment

although the research on welding pollution in China started late, it has developed rapidly. On the basis of fully drawing lessons from relevant foreign product design and research results, a design idea suitable for China's national conditions has been formed. However, due to the gap in the overall level, there is still a certain gap compared with foreign similar products in the design and manufacture of treatment equipment, operation cost control and treatment effect

3 welding workshop pollution

according to different formation methods, the pollution of welding workshop can be divided into chemical harmful pollution and physical harmful pollution

3.1 chemical harmful pollution

chemical harmful pollution refers to the welding smoke and harmful gases formed in the welding process

3.1.1 welding fume [1]

welding fume is formed by oxidation and condensation of steam generated by metallic and non-metallic substances under overheated conditions. Therefore, the chemical composition of welding fume depends on the composition of welding materials (welding wire, welding rod, flux, etc.) and the materials to be welded and the difficulty of evaporation. Welding materials with different components and materials to be welded will produce welding fumes with different components during welding (see Table 1). Table 1 chemical composition of common structural steel electrode dust (mg/m3)

the characteristics of welding dust are:

(1) welding dust particles are small, and the dust is fragmented, with a particle size of about 1 m

(2) the viscosity of welding smoke is large

(3) the temperature of welding fume is high. In the exhaust duct and filter element, the air temperature is 60 ~ 80 ℃

(4) the amount of dust generated during welding is large. Generally speaking, the amount of smoke and dust produced by a welder for one day is about 60 ~ 150g. Several welding (cutting) methods generate dust per minute during welding (cutting) and per kilogram of molten welding material (see Table 2). Table 2 dust generation of several welding (cutting) methods

3.1.2 harmful gases

harmful gases are generated under high-temperature arc during welding, mainly including ozone, nitrogen oxide, carbon monoxide, fluoride and chloride

3.2 physical harmful pollution

physical harmful pollution includes: noise, high-frequency electromagnetic radiation and optical radiation

3.2.1 noise

the noise in the welding workshop is mainly the aerodynamic noise generated in the process of plasma spraying and cutting. Its size depends on different gas flow, gas properties, site conditions and the diameter of welding gun nozzle. Most of these noises are above 100dB

3.2.2 high frequency electromagnetic radiation

high frequency electromagnetic radiation is generated with the expanded application of argon arc welding and plasma welding. When plasma welding and argon arc welding adopt high-frequency oscillator to start the arc, the oscillator should produce strong high-frequency oscillation, puncture the air gap between thorium tungsten electrode and nozzle, and ignite the plasma arc. In addition, another part of the energy radiates into space in the form of electromagnetic waves, forming a high-frequency electromagnetic field, which pollutes the local environment. The intensity of high-frequency electromagnetic radiation depends on the output power of high-frequency equipment, the working frequency of high-frequency equipment, the distance of high-frequency oscillator, and whether the equipment and transmission line are shielded

3.2.3 light radiation

in various welding processes, especially various open arc welding, poorly protected hidden arc welding and electroslag welding in the slag forming stage, exposed arc should be generated to form light radiation. The intensity of light radiation depends on the following factors: welding process parameters, welding method, distance and relative position from the welding point, and protection method

4 harm of welding workshop pollution to operators

the occurrence of welding occupational diseases is the result of the comprehensive action of various welding pollution factors. Welder occupational diseases include welder pneumoconiosis, manganese poisoning, fluorosis, metal smoke heat and electro-optic ophthalmia. Among them, the medical clinical manifestations of chemical pollution (welding smoke and harmful gases) are cough, expectoration, chest tightness, shortness of breath and sometimes hemoptysis. The medical clinical manifestations of physical pollution are diverse. Noise can cause operator irritability and headache; The main effect of high-frequency electromagnetic radiation on human body is cupping machine. The technical principle of testing machine. Neurasthenia syndrome, such as dizziness, headache, fatigue, palpitation, weight loss, hair loss, etc; During the welding process, light radiation will lead to the occurrence of electro-optic ophthalmia, mild eye discomfort and foreign body feeling, and severe eye burning and severe pain

the occurrence of welders' occupational diseases mainly depends on the following factors: the concentration and nature of welding smoke and gas and their pollution degree, the opportunity and duration of welders' exposure to harmful pollution, the physical fitness and personal protection status of welders, the quality of welders' production environment and the interaction of various harmful factors. Only when the welder works in a poor working environment or lacks labor protection for a long time, it is possible to cause occupational diseases

5 prevention, treatment and development direction of welding workshop pollution

the three ways to prevent welding workshop pollution are pollution source control, transmission path treatment and personal protection

5.1 control of pollution sources

the types and quantities of pollution generated in the welding process depend on the production process, production equipment and the technical ability of operators

5.1.1 optimization of production process

different welding processes produce different types and quantities of pollutants. If conditions permit, mature submerged arc welding should be used instead of open arc welding, which can greatly reduce the pollution degree of pollutants

5.1.2 equipment improvement

on the premise of determining the production process, equipment with a high degree of mechanization and automation should be selected. Low dust and low toxicity welding rods should be used to reduce smoke concentration and toxicity. When purchasing new equipment, we should pay attention to the environmental protection performance of the equipment and choose more integrated equipment equipped with purification parts

5.1.3 improve the technical level of operators [2]

high level welding workers can skillfully and flexibly implement the operation rules in the welding process, such as constantly observing the drying degree of welding rods, the inclination angle of welding rods, the length of welding rods and the position of weldments, and making corresponding technical adjustments. Compared with unskilled workers, the dust emission is reduced by more than 20%, the welding speed is 10% faster, and the welding quality is good

5.2 control of transmission routes

5.2.1 control of welding smoke and harmful gases

control of welding smoke and harmful gases has two control modes in transmission routes: comprehensive ventilation and local exhaust

comprehensive ventilation, also known as dilution ventilation, dilutes the concentration of harmful substances in the indoor air with clean air, so that the concentration of harmful substances in the indoor air does not exceed the maximum allowable concentration specified in the health standards, and continuously discharges the polluted air outdoors or collects and purifies it. Comprehensive ventilation includes natural ventilation and mechanical ventilation [3]. In foreign countries, natural ventilation is generally used for outdoor welding operations or welding in open space, and mechanical ventilation is usually used for indoor operations. Through the axial flow fan installed on the wall or ceiling, the welding smoke in the workshop is discharged outdoors, or recycled in the workshop after purification by the purifier, so as to reduce the smoke concentration in the workshop. Circulating the purified air solves the energy loss in the workshop, which is widely used abroad

local exhaust is to control the local air flow, so that local workplaces are not polluted by harmful substances and maintain a good air environment. Generally, the local exhaust unit is composed of 4 parts: gas collecting hood, air duct, purification system and fan. Local exhaust can be divided into fixed local exhaust system and mobile local exhaust system according to different gas gathering methods. The fixed local exhaust system is mainly used for the operation place and workers' operation. In addition, a large welding production workshop equipped with a wide variety of experimental attachments can be fixed at one time according to the actual situation. The working state of the mobile local exhaust system is relatively flexible, and different working postures can be adopted according to different working conditions to ensure the processing efficiency and the convenience of operators. The cleaning system of welding fume and harmful gas usually adopts the bag type or the combination of electrostatic precipitation and adsorbent, which has high treatment efficiency and stable working state

5.2.2 noise control

the noise in the welding workshop is mainly reflected sound. Therefore, if conditions permit, sound-absorbing materials should be arranged on the walls in the workshop. Arranging sound absorbers in space can reduce the noise by about 30dB

5.2.3 high frequency electromagnetic radiation control

welding work should ensure that the workpiece is well grounded. At the same time, strengthen ventilation and cooling, and control the temperature and humidity of the workplace

5.2.4 control of light radiation

welding stations should be equipped with protective screens, which are mostly gray or black; The wall surface of the workshop is decorated with absorbent materials. The above two measures can reduce the reflection of arc light and protect the operator's eye health

5.3 personal protection

when welding work is carried out in some specific places, such as underwater, high altitude, in tanks or shipyards, due to the limitations of the place, the overall protection is difficult to achieve. At this time, personal protection becomes the main protective measure. Personal protective equipment is designed according to the characteristics of various hazard factors, with strong pertinence and many kinds, such as masks, helmets, protective glasses, hard hats, ear muffs, masks, etc

6 conclusion

there are many kinds of pollution in the welding workshop. Comprehensive treatment should be carried out from three aspects: pollution source, transmission route and personal protection. The pollution control plan should be formulated in combination with the specific situation of the workshop, which cannot be divorced from reality and affect the normal production operation. The design of the treatment scheme should fully consider the treatment methods of various pollutants on the premise of ensuring the treatment effect