(1) The nature and harm of mine dust
1. The concept of dust
(1) All dust. Full dust refers to the collection of all solid particles suspended in the air for a certain period of time by a general open sampler.
(2) Respirable dust. Respirable dust refers to floating dust that can be inhaled into the lungs of the human body and stay in the alveolar region. Very fine dust with an aerodynamic diameter of less than 7.07 m is the main dust causing pneumoconiosis.
(3) Floating dust and falling dust, the dust suspended in the air is called floating dust, and the dust deposited on the top of the roadway, the gang, the bottom plate and the object is called dust.
2. Dust properties
(1) The content of free silica in the dust. The content of free silica in dust is the decisive factor that harms the human body. The higher the content, the greater the harm. Free silica is a major cause of silicosis.
(2) The particle size of the dust. Dust particle size refers to the size of the dust particle size. In general, the smaller the dust particles, the greater the harm to people.
(3) Dispersion of dust. The degree of dust dispersion refers to the percentage of dust particles of various grain sizes in the overall composition of the dust. In the dust composition, the larger the percentage of dust particles smaller than 5 m, the greater the harm to humans.
(4) The concentration of dust. The concentration of dust refers to the amount of floating dust contained in a unit volume of air. The higher the dust concentration, the greater the harm to the human body.
(5) Adsorption of dust. The adsorption capacity of dust is closely related to the surface area of ​​dust particles. The larger the dispersion, the larger the surface area and the enhanced adsorption capacity. The main indicators are hygroscopicity and toxicity.
(6) The chargeability of dust. Dust particles can carry electric charge. The source is that coal rock is charged by friction during pulverization, or it is charged by collision with ions in the air. The amount of dust particles depends on the size of the dust particles and is related to temperature and humidity. When the amount of electricity is increased, the amount of charge is reduced when the humidity is increased.
(7) Combustion and explosiveness of coal dust. When coal dust reaches a certain concentration in the air, it can be burned and exploded under the ignition of an open flame.
3. Danger of dust
The hazards of mine dust are mainly reflected in the following four aspects:
(1) polluting workplaces, endangering human health and causing occupational diseases;
(2) Certain mineral dust (such as coal dust and sulfur dust) can explode under certain conditions;
(3) Accelerate mechanical wear and shorten the service life of precision instruments;
(4) Reduce workplace visibility and increase the incidence of industrial accidents.
(2) Mine dust prevention and control technology
Mine dust prevention technology includes wind, water, dense, clean and protective, and is mainly based on wind and water. The wind is the ventilation and dust removal; the water refers to the wet operation; the dense refers to the closed dust; the net is the purification of the wind; the protection is to take personal protective measures. The main dust prevention techniques in the mine production process are described below.
2. Drilling work surface dustproof
(1) Dust-proof work surface of the gun. The pneumatic rock drill or the electric coal drill is a process in which the working face of the blasting machine has a long duration and a high dust generating amount. Generally, the amount of dust generated in the dry eye-catching process accounts for 80% to 90% of the total dust production of the working face, and 40% to 60% when wet. Therefore, eye dust prevention is the focus of dust control on the working face.
1 eye dust. The main technologies for eye dust prevention are wet rock drilling, dry rock drilling and dust collection.
Air-drilling wet rock drilling: This is an effective basic dust-proof method for rock roadway excavation at home and abroad.
Dry rock drilling and dust collection: When it is impossible to carry out wet rock drilling, if the rock expands when it meets water, the rock crack develops, and the wet operation is poor, the dustproof effect is poor, etc., it can be used for dry type such as orifice dust collector. Hole dust removal technology.
Coal electric drill wet type: In coal roadway and semi-coal roadway, the use of coal electric drill wet type eye can obtain good dust reduction effect, and the dust reduction rate can reach 75%~90%.
2 Shoot the gun to prevent dust. Shooting is the largest process of dust production in the blasting face. The main dust prevention measures are as follows:
Water Cannon Mud: This is the most effective measure to reduce the amount of dust generated during shooting.
Shotgun spray: This is a simple and effective dust reduction measure. Spraying during shooting can reduce dust concentration and gun smoke.
(2) Ventilation and dust removal on the excavation face. Although the dustproof measures have been taken in the excavation working face, some fine dust is still suspended in the air, especially the mechanization of the excavation is increasing, the dust production intensity is increasing sharply, and the dust production intensity of the excavation working face is greatly high. In the blasting work surface, it is difficult to control dust with general dustproof measures. Therefore, ventilation and dust removal technology has been studied at home and abroad to effectively control high concentration dust sources.
1 ventilation dust removal system. Reasonable ventilation and dust removal system is a necessary condition for controlling the movement and diffusion of suspended dust on the working face. There are mainly three kinds of ventilation systems used at home and abroad: long-pressure short-draw ventilation and dust removal system, long-extraction ventilation dust removal system and long-pumping short-pressure ventilation dust removal system.
2 ventilation and dust removal equipment . The main equipments include wet dust removal fan, wet dust collector, bag filter and supporting extraction bellows and walled air duct.
3 ventilation process requirements. The relationship between the position of the pressure and the suction nozzle: the matching of the pressure of the compressed air; the installation position of the local ventilator; the series connection requirement of the extraction type local ventilator and the dust removal local ventilator.
(3) Anchor spray protection is dustproof. Anchor spray support technology has developed rapidly, and it is also one of the main sources of dust in coal mines. The dust of anchor spray support mainly comes from the production process and equipment such as anchoring eye, mixture transfer, mixing and feeding, shotcrete and jetting machine itself.
For these dust-producing sources, anchor spray protection mainly adopts the preparation of dip material to feed the jet machine, add water to the double water ring, add the different diameter hoist tube, low pressure near spray, water curtain purification and ventilation dust removal.
3. Transport and transfer dustproof
(1) Mechanical control automatic spray dust reduction device. The device is characterized by simple structure, easy manufacture, convenient use and maintenance, and good dust-reducing effect.
(2) Electrical control automatic spray dust reduction device. The device is suitable for different dust sources in the coal mine reloading transportation system. It is controlled by electric appliances to realize automatic spraying, and has various forms such as light control, voice control, touch and magnetic control.
4. Comprehensive dust prevention measures
Comprehensive dust-proof measures include wet drilling, flushing the wall of the well, using water cannon mud, shooting spray, loading rock (coal) watering and purifying the air flow.
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