The machinery manufacturing industry covers a wide range, including transportation, machine tools, agricultural machinery, textile machinery, power machinery and precision instruments
Generally, there are casting, forging, heat treatment, machining and assembly workshops
Evaluation and detection of occupational hazards in the machinery industry
Machining is the use of a variety of machine tools for turning, planing, drilling, grinding, milling and other cold processing of metal parts;
In the process of machine manufacturing, it is usually through casting, forging, welding, stamping and other essentials to make metal parts, and then through cutting to make qualified parts, and finally assembled into a machine.
There are many occupational hazards in the machinery industry, especially in the machinery manufacturing industry.
The following is to explain which occupational hazard factors need attention.
Occupational hazard factors
Forging is a kind of processing method that applies an external force to the blank to produce part or all of the plastic deformation of the blank, so as to obtain the forging.
Noise is the most harmful occupational hazard in forging process.
Forging hammers (air hammers and pressure hammers) can produce strong noise and vibration, which is generally impulse noise, and its intensity is more than 100dB (a).
According to the noise detection of forging workshop in a machinery factory, the results are 83-100, 2dB (a), with an average of 92, 08db (a).
Punching machine and shearing machine can also produce high-intensity noise, but its intensity is generally smaller than that of forging hammer.
The temperature of the heating furnace is as high as 1200 ℃, and the forging temperature is between 500 ~ 800 ℃.
In the process of production, high temperature and strong radiant heat can be produced in the workplace.
Dust and poison hazards
Metal dust and coal dust can be produced in the process of charging, discharging and forging in the forging furnace and forging hammer, especially in the furnace of the fuel industry.
Combustion furnace can produce carbon monoxide, sulfur dioxide, nitrogen oxides and other harmful gases.
It can be divided into manual and mechanical modeling.
Manual molding refers to the process of manual completion of sand tightening, mold stripping, trimming and box closing.
Workers with high labor intensity are directly exposed to dust, chemical poisons and physical factors, which cause great occupational hazards.
The productivity of mechanical molding is high, the quality is stable, the labor intensity of workers is low, the chances of workers contacting with dust, chemical poisons and physical factors are less, and the occupational hazards are relatively small.
A large amount of sand dust is produced during molding, casting sand falling and cleaning. The nature and harm of dust are mainly determined by the type of molding sand. For example, when quartz sand is used for molding, it is most harmful because of the high content of free silica.
According to our detection of dust concentration in the workplace of the molding workshop of a machinery factory, the results are 27, 5-62 and 3mg / m3, with an average of 39 and 5mg / m3.
Poisons and physical hazards
The coal drying, melting and pouring of sand mold and sand core produce high temperature and heat radiation;
If coal or gas is used as fuel, carbon monoxide, sulfur dioxide and nitrogen oxides will be produced;
If high-frequency induction furnace or microwave oven is used for heating, there will be high-frequency electromagnetic field and microwave radiation.
3. Heat treatment
The main purpose of the heat treatment process is to change the properties of the metal (hardness, toughness, elasticity, conductivity, etc.) without changing the shape of the parts, so as to achieve the performance required by the process and improve the product quality.
Heat treatment includes normalizing, quenching, annealing, tempering and carburizing.
Heat treatment can be divided into general heat treatment, surface heat treatment (including surface quenching and chemical heat treatment) and special heat treatment.
Normalizing, annealing, carburizing, quenching and other heat treatment processes of mechanical parts need a wide range of auxiliary materials, such as acid, alkali, metal salt, nitrate and cyanide.
These excipients are highly corrosive and toxic substances.
For example, when barium chloride is used as heating medium and the process temperature reaches 1300 ℃, a large amount of barium chloride evaporates and produces barium chloride dust to pollute the air of the workshop;
During the chlorination process, a large amount of ammonia is discharged into the air of the workshop;
Cyanides (potassium ferrocyanide, etc.) are used in Carburizing and carburizing processes;
Nitrogen oxides are produced by the action of molten nitrate and oil stain of the workpiece in salt bath furnace.
In addition, organic agents such as methanol, ethanol, propane, acetone and gasoline are often used in the heat treatment process.
Normalizing and annealing of mechanical parts.
Carburizing, quenching and other heat treatment processes are carried out under high temperature. All kinds of heating furnace, salt bath and heated work in the workshop are heat sources.
These heat sources can create high temperature and strong thermal radiation working environment.
All kinds of motors, fans, industrial pumps and mechanical running equipment can produce noise and vibration.
However, the noise intensity of most heat treatment workshops is small, and the phenomenon of noise exceeding the standard is rare.
Use various machine tools for turning, planing, drilling, grinding, milling and other cold processing of metal parts;
In the process of mechanical manufacturing, metal parts are usually made by casting, forging, welding, stamping and other methods, and then qualified parts are made by cutting, and finally assembled into machines.
The occupational hazards in the production process are relatively small, mainly the emulsion used in metal cutting and the impact of cutting on workers.
The commonly used emulsion is composed of mineral oil, naphthenic acid or oleic acid and alkali (caustic soda).
Due to the high-speed transfer of machine tools, emulsion splashes, easy to pollute the skin, can cause folliculitis or acne and other skin diseases.
In the process of machining, there are also a lot of metal and mineral dust in the process of rough grinding and fine grinding.
The synthetic grindstone is mainly composed of emery (alumina crystal), in which the content of silicon dioxide is very small, while the natural grindstone contains a lot of free silicon dioxide, which may lead to aluminum pneumoconiosis and silicosis.
The mechanical noise produced by most machine tools is between 65 dB (a) and 80 dB (a), and the phenomenon of excessive noise is rare.
The occupational hazard factors of special machining are related to machining tools;
Such as metal dust of EDM, high temperature and ultraviolet radiation of laser processing, etc;
Electron beam X-ray and metal dust, etc;
There are metal dust, ultraviolet radiation and high frequency electromagnetic radiation in ion beam processing. If tungsten electrode is used, there will be ionizing radiation;
In addition, the equipment operation produces noise and vibration.
5. Mechanical assembly
There are few occupational hazard factors in the simple mechanical assembly process, and the hazard is basically the same as that of general machining.
However, the occupational hazards in the complex assembly process are mainly related to the special assembly process.
If we need to use all kinds of welding, there is the problem of welding occupational hazards;
If adhesives are needed, there are occupational hazards of adhesives
If the coating process is needed, there will be occupational hazards of the coating process.
The occupational hazards of the machinery manufacturing industry mainly focus on the hazards of silicon dust in casting production, organic solvents such as benzene and homologues in coating production and welding (smoke) dust in welding operation.
Therefore, the problems of occupational hazard protection in the machinery manufacturing industry are as follows:
In the layout of the workshop, we should consider reducing the cross pollution of occupational hazards.
For example, the melting furnace in the casting process should be placed outdoors or far away from the public places where people gather;
Riveters, welding and painting processes shall be arranged separately.
The molding sand with low free silica content should be selected as far as possible, and manual molding and sand cleaning should be reduced.
Sand cleaning is the post with the highest dust concentration in foundry production, which should be given key protection.
For example, installation of high-power ventilation and dust removal system, spray wet operation should be carried out to reduce dust concentration in the air of workplace.
And do a good job in personal protection, wear dust masks in line with the relevant national standards.
Antivirus and emergency rescue
For the equipment that may produce chemical poisons in the process of heat treatment and metal smelting, sealing measures should be taken or local ventilation device should be installed.
For workplaces producing highly toxic gases such as carbon monoxide, hydrogen cyanide, formaldehyde and benzene, such as some special quenching, painting and adhesive posts, emergency rescue plans for acute occupational poisoning accidents should be formulated, warning signs should be set, and gas masks or gas masks should be equipped.
Noise is one of the important occupational hazards in the machinery manufacturing industry.
Noise control mainly includes the control of high-intensity noise equipment such as air hammer, air compressor, grinding, polishing, stamping, plate shearing and cutting in casting and forging.
High-intensity noise sources can be arranged in a centralized way, and sound insulation shield can be set.
The aerodynamic noise source should be silenced at the inlet or outlet.
Sound insulation and absorption treatment shall be adopted for the centralized control room and post operation room.
When entering the workplace with noise intensity over 85dB (a), anti noise earplug or earmuff should be worn.
Vibration is a common occupational hazard in the machinery manufacturing industry.
Vibration reduction measures or rotation operation should be taken for riveting, forging press, molding sand tamping machine, sand dropping, sand cleaning and other vibration equipment.
Radio frequency protection
Appropriate shielding materials should be selected to shield the equipment producing high frequency, microwave and other radio frequency radiation, or to provide distance isolation protection and time protection.
It is necessary to do a good job in summer heat prevention and cooling work for high-temperature workers such as casting, forging and heat treatment.
Comprehensive measures of engineering technology, health care and labor organization and management should be taken, such as the reasonable arrangement of heat sources, the supply of cool and salty drinks, rotation operation, air conditioning in the centralized control room and operation room, etc.