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Oil storage and transportation industry should be careful to prevent electrostatic hazards

static electricity has two sides. On the one hand, the application of electrostatic technology has been widely used in various industries and fields of human production, life and scientific research, such as electrostatic copying, electrostatic dust removal, electrostatic separation, electrostatic corrosion prevention, electrostatic papermaking, electrostatic breeding, etc; On the other hand, electrostatic phenomenon will also bring all kinds of harm to human beings in a very wide range. Due to the continuity of the production process and the particularity of the management object, the harm caused by static electricity in the oil storage and transportation industry may even bring serious consequences. However, as long as we pay attention to static electricity, scientifically understand and correctly grasp the process and law of static electricity harm, practically strengthen safety management, and take positive and effective measures, we will be able to control the harm caused by static electricity

first, the generation and harm of static electricity

when two objects with different properties rub against each other or peel off rapidly after close contact, electron transfer will occur due to their different attraction to electrons. If the object is insulated from the earth, the charge cannot leak and stays in the interior or surface of the object in a relatively static state. This charge is called static electricity

(I) causes of static electricity

the causes of static electricity can be explained mainly from two aspects: the internal characteristics of substances and the influence of external conditions

1. Internal characteristics

(1) the escape work equipment of substances adopts electronic experiments. Because different substances require different external work (escape work) to separate electrons from the original object surface, electron transfer will occur on the close contact surface between the two, and substances with small escape work lose electrons and carry positive charges. The difference of electronic work of various substances is the basis of electrostatic generation

(2) dielectric constant different dielectric constant (permittivity) is a major factor determining capacitance. Another factor affecting charge accumulation is that under specific configuration conditions, the capacitance and resistance of the object combine to determine the dissipation law of static electricity. For liquids with large dielectric constant, the resistivity is generally low

because we are composite Engineers (3) the resistivity of materials is different. The generation of static electricity is closely related to the conductivity of materials. It is expressed in resistivity and inversely proportional to resistivity. According to the conclusion of a large number of experiments, when the resistivity of a substance is less than 106 Ω • cm, static electricity will leak quickly because of its good conductivity. Substances with resistivity greater than 106 Ω • cm and less than 1010 Ω • cm usually have a small amount of charge and are not easy to generate static electricity. Substances with resistivity greater than 1010 Ω • cm and less than 1015 Ω • cm are most likely to carry static electricity, which is the key object of anti-static work. However, when the resistivity is greater than 1015 Ω • cm, the substance is not easy to generate static electricity, but once static electricity is generated, it is difficult to eliminate it. Therefore, the resistivity is taken as the condition to distinguish whether static electricity can accumulate

it must be pointed out that water is a good conductor of static electricity, so static electricity will be generated when water droplets flow relatively with the oil. When a small amount of water is caught in the insulating oil, it will increase the static electricity of the oil

2. External action conditions

(1) attaching a charged polar ion or free electron to an object insulated from the earth can also make the object appear to be electrostatic. After people move in places with charged particles, because charged particles are adsorbed on the human body, they will also be charged

(2) close contact and rapid separation are two different substances. Through close contact and rapid separation, external energy can be transformed into electrostatic energy and stored in substances. In addition to friction, its main manifestations include impact, tearing, stretching, peeling, twisting, extrusion, filtration and crushing

(3) inductive electrification. A charged object can cause charges of opposite polarity to appear in different parts of the surface of another conductor nearby that is not connected with it. This phenomenon is inductive electrification

(4) in the electrostatic field, the molecules inside or on the surface of the polarizing insulator can produce polarization and generate charge, which is called electrostatic polarization. For example, when the insulating container is filled with static liquid, the outer wall of the container is also charged, which is the reason

(II) electrostatic hazard

1 Electrostatic sparks cause combustion and explosion

when the charged body is close to the uncharged body or the object with low electrostatic potential, discharge will occur and sparks will be generated. When the spark energy of electrostatic discharge reaches or exceeds the minimum ignition energy of surrounding combustibles, and the concentration or content of combustibles in the air is also within the explosion limit, it can immediately cause combustion or explosion

2. Hinder production

in some production processes, if static electricity is not eliminated, it will hinder production or reduce product quality. For example, in the application of synthetic fibers such as polyester, acrylic and nylon, the problem of static electricity is very serious. In the powder processing industry, the static electricity generated in the production process will not only bring the risk of fire and explosion, but also reduce the production efficiency and affect the product quality. In the plastic and rubber industry, due to the friction between products and rollers, as well as the extrusion and stretching of products, more static electricity will be generated. If it cannot be dissipated quickly, it will absorb a lot of dust

II. Basic measures to prevent electrostatic hazards

the principle of preventing electrostatic hazards is to control static 4 Elastic deformation: after removing the load, the generation of electricity and the accumulation of static electricity should be prevented. To control the accumulation of static electricity, complex data analysis should be carried out to try to accelerate the leakage and neutralization of static electricity, so that static electricity does not exceed the safety limit. The control of static electricity is mainly to control the process and reasonably select the materials used in the process. Grounding, humidification, adding antistatic agent, etc. are all methods to accelerate electrostatic leakage. Methods to eliminate electrostatic hazards by using induction neutralizer, external power neutralizer, radiation neutralizer and other devices are all methods to accelerate electrostatic neutralization

(I) process control method

process control method is to take measures in process flow, equipment structure, material selection and operation management, so as to limit the generation of static electricity or control the accumulation of static electricity, so as to reach a dangerous level

1. Limit the conveying speed

reduce the friction speed in liquid conveying or the flow rate of liquid materials in the pipeline and other working parameters, which can limit the generation of static electricity