Research on the hottest static electricity and sta

Research on electrostatic and electrostatic protection measures

discussion setting:

in our coating production, the processed base cloth or transfer film and various guide rollers of the coater will produce a large amount of static electricity, and in the production process, we must use low boiling point, volatile flammable and explosive inorganic solvents, such as ethyl acetate, toluene, etc. In stable production, a large amount of flammable and explosive solvent gas will be produced in the cloth head and drying channel. If the method of eliminating static electricity is improper, and the static charges are accumulated continuously, it will lead to high electric field strength, dielectric breakdown, neutralization of positive and negative charges, electric sparks, ignition or detonation of inorganic solvent gases, and serious personal and equipment accidents. In view of the fact that our company has had two electrostatic fires in recent years, in order to prevent the trouble and stabilize the production safely, the following discussion is made on the electrostatic protection of the equipment

1. Electrostatic point of view

static electricity, literally, refers to moving, inactive charges. We know that matter is made up of atoms. Atoms are divided into nuclei and extranuclear electrons. Electrons surround the nuclei and do high-speed circular activities. The nucleus is positively charged and the electrons outside the nucleus are negatively charged. In the ordinary environment, the number of positive charges in the nucleus is equal to the number of negative charges of electrons outside the nucleus, so it is not electric. However, when affected by external forces, this kind of equilibrium can be broken. At this time, the electrons leave the atomic nucleus beam and become negatively charged, while the atoms become positively charged due to the loss of electrons. When this kind of charge deposit with only one polarity accumulates on an object, it forms static electricity. There are positive and negative charges. Then the static electricity scene is divided into positive static electricity and negative static electricity. With the increase of static electricity, static electricity forms an electrostatic field around it. When the energy of the electrostatic field increases to a certain range, it can puncture its medium and discharge externally. For example, on dry nights in summer, when people take off clothes such as chemical fiber, they can see sparks and sounds, which is the notice that chemical fiber rubs against the human body and brings positive static electricity to the human body

2. The generation of static electricity

static electricity is mainly caused by the following ways:

(1) friction. Because the objects with different data contact and then break up, because the beams of electrons with different atoms are different. When two kinds of materials with different data contact or rub, the core electrons will be transferred to the side with higher beams, resulting in one data being positively charged and the other data being negatively charged

(2) conduction. Because in a conductor, electrons can move freely in its outline. When in contact with the charged body, the electrons will transfer from the generated charge, resulting in the charge balance between the two, thus forming an electrostatic scene

(3) induction. The induction here refers to the induction of the adjacent electric field. For the conductor, the electrons roughly move freely in the conductive data. If the conductor is placed in another electrostatic field, because the opposite charges are overhead and attract each other, the positive and negative ions will be transferred, and the conductor will be charged due to the imbalance between the positive and negative charges caused by the induction of the electrostatic field

in ordinary environment, non conductors with smaller conductivity are more likely to generate static electricity, and the static charges generated at this time are not easily excluded. Its leakage time can reach the order of seconds, hours and days. For the conductor, even if static electricity is generated, the charge can be excluded by the conductor. If the conductor shell is insulated from the earth, the conductor can also be charged. In addition, humidity also has a great influence on static electricity. Static electricity generated when humidity is 10% - 20% is times stronger than when humidity is 70% - 90%

3. The production of static electricity in the coating production process

the processed materials produced by our company are insulating base cloth and plastic materials, such as PE, pet, etc. in the process of production, they quickly pass through the vast number of metal and rubber guide rollers of foreign fixture coaters, because they are constantly and several times pressurized, otherwise they will run, touch, break up, friction, and generate a large amount of static electricity, especially the intensity of static electricity generated by the rubber pressing roller is far better than the metal guide roller. According to the electrostatic series, the base cloth and pet are negatively charged, and the guide roller surface generates an equal amount of static charges with different signs. When measured by electrostatic test, the measured electrostatic voltage reaches thousands of volts

4. Analysis of our electrostatic removal methods

our company has adopted improper electrostatic removal methods during production, such as conductive rope, body and other large grounding electrostatic removal methods. These methods have different ways to eliminate electrostatic effects, but they cannot ensure safe production

(1) hang the electrostatic rope. This kind of method is only suitable for eliminating the accumulated data of the processed object. It cannot eliminate the static electricity generated after passing through the subsequent guide rollers: especially, the space around the production line is numerous, and it is not convenient to hang the conductive rope. And in the production operation, due to the notices such as too fast speed and mechanical vibration, it is easy to reduce the contact surface of the conductive rope, the transferred charge is insufficient, and with the increase of utilization, the beads, dust, and small aluminum layers are inexhaustible, and the electrostatic rope will fall out after a period of time. (in terms of cost, the continuous loss of electrostatic rope is large)

(2) adopt a huge body with high grounding resistance. The method of eliminating static electricity by shell is actually limited to Ohm's Law: the idea that u=ir. Ohm's law is the relationship between voltage u, current I and carrier resistance R on the premise that the reaction carrier is a conductor and the charge is uniformly and orderly diffused in the conductor. The carrier of electrostatic charge in coating production is insulating base cloth, plastic and rubber, and the electrostatic charge under it diffuses disorderly in the insulator, so it is impossible to deal with the problem of electrostatic accumulation with Ohm's law

5. Practical analysis

based on the foregoing and coating production practice, explore ways to eliminate electrostatic sparks. From the perspective of the future reform direction, we must take Coulomb's Law (formula ①) and electric field intensity (formula ②) and other electrostatic coherent reality as the basis, that is:

dielectric constant is constant in homogeneous medium