Static electricity phenomenon
Dry weather, combing hair with a plastic comb, the comb will attract hair; in the dark when you take off the body of nylon clothes, not only can you hear the sound, but also see sparks. These are caused by friction generated by high voltage static electricity, static electricity phenomenon is a common natural phenomenon. Static electricity can bring trouble and harm to people. In the chemical fiber production and printing process, due to static electricity and attract air lint and dust, will make the product quality decline. The danger of static electricity is that static sparks can ignite flammable substances and cause explosions. Oil in the pipeline flow, coal from the pipeline mouth high-speed spray, air containing coal dust in the air duct flow and gasoline in the car tank transportation. Will be due to friction caused by static electricity, when the accumulation of static electricity to reach a considerable voltage; will produce electrostatic sparks and cause an explosion.
Static prevention
How to prevent the harm caused by static electricity? The most simple and reliable method is to use a wire to ground the equipment. In order to generate the charge into the earth in a timely manner. We see tanker trucks dragged behind a chain that touches the ground, is the reason. Increase air humidity is also an effective way to prevent static electricity, air humidity, charge can be released at any time. In doing static experiments, the air humidity is not easy to do when the success of the reason is this. Textile factories, detonators, explosives and other production workshops on the air humidity requirements are particularly strict, one of the purposes is to prevent the explosion caused by static electricity.
Electrostatic applications
Electrostatic precipitator It is the principle shown in Figure 8.19. B is a metal cylinder. A is suspended in the center of the cylinder wire. The wire and tens of kilovolts of negative high-voltage end connected. Cylinder B connected to the positive pole of the high-voltage power supply and ground. In this way, in the vicinity of the wire to form a strong electric field area, enough to make the surrounding gas ionization. These are ionized gas in motion and dust meet. The dust is electrically charged. Under the action of the electric field force, these charged dust will move toward the electrode (A, B). After reaching the electrodes, the dust will gradually fall down along the electrodes. Therefore, it can reduce the dust pollution of the atmosphere.
Electrostatic painting The principle of electrostatic dust removal is the same, is the use of high voltage formed by the electrostatic field to paint the new technology. It has the advantages of high efficiency, less waste, good quality and health of workers compared with manual painting. Figure is a rotary cup type electrostatic paint spraying device schematic diagram. The paint enters the high-speed rotating metal cup B through the paint delivery pipe A. The paint sprayed from the spray cup is atomized due to the high-speed rotation of the spray cup. Paint mist particles due to the spray cup connected to the negative high voltage (60-120kV) and negatively charged, mutually exclusive and uniformly dispersed, at the same time, under the action of the electric field force, connected to the positive high voltage to the workpiece C to fly, be adsorbed on the work surface to form a bright and solid layer of paint. Electrostatic paint spraying due to the small range of electric field force, so it will not pollute the air. At present, electrostatic painting has been widely used in machine parts, train cars and other processing.
Electrostatic flocking textiles often have a variety of beautiful patterns, some of which is the use of electrostatic flocking method of production. Figure 8.21 is a schematic of the process. The bottom is a piece of high-voltage power supply connected to the positive pole of the metal mesh, the shape of the disk, can be stored fluff. Metal plate and metal mesh to form a strong electric field, beforehand with adhesive drawing on the pattern of textiles, placed on the metal plate, driven by a reel, through a strong electric field. Fluff in the metal mesh Because of the negative charge, be repelled and fall through the metal mesh, under the action of the electric field force, quickly poured to the textile, part of which is glued to the adhesive. Not be glued to the fluff, its negative charge by the textile neutralization, and then take the positive charge and was repelled out, and in the electric field force, and soon back to the metal mesh, so that the textile coating glue place constitutes a beautiful pattern.
Static electricity in the industrial application is very wide, in addition to the above list of several examples, there are electrostatic imaging. Electrostatic copying, as well as high-voltage electric work and many other aspects. In modern scientific research is also widely used, such as electrostatic gas pedal.
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