Cause and prevention of electrostatic fire in the

Causes and prevention of static fire in gas stations

in recent years, gas station fires have been on the rise, threatening the safety of people's lives and property. The main causes of fire in gas stations include open fire, lightning strike, static electricity, etc. This paper only analyzes the problems of preventing static fire in gas stations, and puts forward corresponding countermeasures

1. Causes of static electricity in gas stations

any object is charged internally. In general, the number of positive and negative charges is equal, and there is no external electrification phenomenon. However, when two different objects contact or rub, electronic gain and loss will occur between objects. The object that gets the electron will be negatively charged, and the object that loses the electron will be positively charged. Under certain conditions, the charges carried by objects cannot be lost and accumulate, which will produce a high static voltage. When two objects with different charges are separated or contacted, electric sparks will appear between objects, which is the phenomenon of electrostatic discharge. The main causes of static electricity are friction, piezoelectric effect, inductive electrification, adsorption electrification, etc. There is relative friction between oil molecules, between oil and oil pipe wall, between oil and input body, between oil and air, and between oil and other objects in the process of receiving, dispatching, operation and movement of oil in gas stations, which produces static electricity. Due to the physical properties of gasoline, it is difficult to lose and accumulate a large number of electrostatic charges. Its voltage can reach tens of thousands of volts. In case of discharge conditions, spark discharge is very easy to cause fire

2. Conditions of static ignition in gas stations

the generation of static electricity is closely related to the conductivity (resistivity) of substances. The smaller the resistivity, the better its conductivity, the less likely it is to generate static electricity. According to the experiment, it is concluded that substances with a resistivity of 1012 Ω cm are most likely to generate static electricity, while the resistivity of gasoline is generally about 1012 Ω cm, so it is easy to generate and accumulate static electricity, thus forming a high potential. When the charged body is close to an object that is not charged or has a low electrostatic potential, if the potential difference reaches more than 300V, discharge will occur and sparks will be generated. When the spark energy generated by electrostatic discharge reaches or exceeds the minimum energy of oil vapor (0.2 ~ 0.25 MJ), it will ignite the combustible gas mixture formed by the mixing of gasoline vapor and air, causing combustion and explosion. In the process of gasoline loading, unloading, filling, pumping and so on, the oil level potential generated due to flow, injection, filtration, impact and other reasons can often reach 2 ~ 2. The utilization of new materials has also attracted 30000 volts of UAV industry enterprises, mold companies, and new material B2B projects. At the same time, the fire caused by electrostatic discharge must meet the following four conditions:

(1) there must be conditions for generating static electricity (including inductive electrification)

(2) it must have electrostatic accumulation and reach the electrostatic voltage that causes spark discharge

(3) there must be a certain amount of explosive mixture in the spark gap

(4) the spark energy of electrostatic discharge must reach the minimum ignition energy of explosive mixture

3. General rules of static fire in gas stations

everything has its rules in the process of occurrence and development, and static fire in gas stations is of course no exception. Mastering the law of static fire in gas stations can be targeted and improve the quality and level of fire prevention. The laws of electrostatic ignition in gas stations include:

(1) electrostatic ignition accidents are prone to occur in dry areas. According to statistics, electrostatic ignition mostly occurs in Northwest and North China, where the climate is dry, and other regions are relatively much less

(2) electrostatic fire accidents are prone to occur in hot seasons. The data from the oil department shows that when the temperature reaches above 37 ℃ and the atmospheric humidity is below 15%, electrostatic ignition accidents are easy to occur

(3) aviation gasoline and other oil products with low ignition temperature are also prone to electrostatic ignition in winter

(4) precautions and characteristics of static rubber tensile strength testing machine are prone to electric ignition when refueling motor vehicles. During the refueling process, the oil droplets that appear when the oil rushes out of the container rub with the air, which can form a high electrostatic potential and cause electrostatic ignition

(5) static ignition is also easy to occur when the open flow is filled and the pipe orifice is bound with a filter sleeve. The reason is that open flow filling is easy to form combustible gas mixture, and static electricity will be generated and accumulated in large quantities. When the filter sleeve is tied to the nozzle, a large amount of static electricity will be brought during the refueling process, which will accumulate more and more, often up to tens of thousands of volts, which is easy to discharge and ignite the oil vapor

in addition, when the gas station does not meet the fire safety requirements, poor management, low safety operation skills of employees, it is also easy to induce electrostatic fire accidents due to the wide use of ultra-thin film and the lack of residual film recovery technology and mechanism. For example, in April 2000, a city gas station oil

tank truck was unloaded without good electrostatic grounding, and electrostatic discharge occurred between the unloading pipe and the oil tank, which ignited the combustible gas formed by the mixing of gasoline vapor and air at the oil outlet, resulting in a fire. Fortunately, the operator was alert and used the self-contained fire extinguisher to put out the fire in time, which did not cause heavy losses

4 harm of human static electricity and preventive measures

during human activities, the contact separation between clothes and external media or clothes, and other reasons will make clothes and soles have a certain amount of static charge. The human body is a good conductor of static electricity. The charge generated locally by clothes makes the human body carry a certain potential through electrostatic induction, forming a charge around the human body. Later, as the local charge of clothes gradually flows to the surface of the whole body, it reaches a steady state of static electricity. For example, when people walk on the insulated ground such as rubber plate or carpet, contact electrification occurs due to the continuous contact and separation between the sole and the ground, which can bring 2 ~ 3KV potential to the human body; Wearing nylon, wool and blended clothes, when standing up from the artificial leather chair, the human body can generate nearly 10000 volts of high-voltage static electricity; In winter, when taking off nylon fiber clothes from the sweater, the human body can carry high-voltage static electricity of more than 10kV. These human static electricity will pose a serious threat to the fire safety of gas stations. For example, in October, 1998, when a gas station in a city was unloading oil, the daughter of the station owner Zhang (8 years old) and his friend Li (7 years old) were playing in the tank farm. Electrostatic discharge occurred due to friction between clothes, which led to the deflagration of combustible gas formed by gasoline vapor and air in the station, causing serious burns to two children. Therefore, we must pay attention to the prevention of fire caused by human static electricity

in order to prevent the harm of human static electricity, the following safety measures should be taken for 30t:

(1) a hand-held metal grounding body should be set at the entrance of the dangerous area

(2) it is strictly forbidden for workers to wear foamed plastic and plastic soled shoes. They must wear anti-static shoes, anti-static clothes or cotton work clothes, and must use anti-static labor protection supplies and tools that meet safety regulations. It is strictly forbidden for staff to wear or take off chemical fiber clothes, and they are not allowed to comb their hair, change clothes or fight with each other. When wearing anti-static clothes, it is strictly forbidden to have two or more clothes made of polyester, acrylic, nylon and other materials in underwear

(3) staff should not sit in chairs made of high resistance materials such as artificial leather

(4) it is not suitable to paint insulating paint on the floor of dangerous areas, and it is strictly prohibited to use rubber plates, plastic plates and other insulating substances to pave the ground

5 countermeasures and measures to prevent static fire in gas stations

static fire in gas stations has the characteristics of strong paroxysm, easy explosion, great difficulty in extinguishing and easy to cause casualties. Therefore, we must increase preventive measures and take the initiative to do a good job in prevention

(1) strengthen the concept of legal system and establish gas stations according to law. For gas stations that do not meet the requirements of fire laws and regulations, they should be immediately closed for rectification and thorough rectification, and can be reopened only after passing the inspection of the fire department

(2) do a good job in electrostatic knowledge education and training, and key posts must work with certificates, so that employees can fully understand the causes of static electricity in gas stations, effectively understand the conditions of static electricity fire in gas stations, and understand and master the laws of static electricity fire in gas stations, so as to lay a solid theoretical foundation for the prevention of static electricity fire in gas stations

(3) strengthen management and improve system norms. According to the standard requirements of fire protection work, a complete set of strict and standardized fire safety systems should be established and improved, such as the safety target system of gas station leaders and employees at all posts, the duty patrol system, the prohibition of open fire system, the entry and exit system of locomotives, vehicles and personnel, the oil receiving and delivery and inspection system, the facility maintenance system, the allocation, management, use and maintenance system of fire equipment, etc. We should earnestly implement the rules and regulations, educate employees to form the habit of consciously abiding by the rules and regulations, prohibit non operators from refueling operations, and prevent irrelevant personnel from staying and playing in the station, so as to form a good fire safety atmosphere

(4) Master safe operation technology and standardize safe operation behavior. The first is to reduce the generation of electrostatic field. Since most of the static electricity of oil products is generated in the process of receiving, sending, filling and transportation, when canning oil, the filler pipe should be extended to 10 ~ 20mm from the bottom of the tank according to the regulations, and the open flow tank should not be used as far as possible. It is strictly forbidden to bind the filter sleeve or other filter media at the oil outlet; The second is to accelerate the release of static electricity. To prevent static electricity from accumulating in oil tanks, pipelines and oil pumps, it is necessary to have a good electrostatic grounding device and form a channel according to the situation. It is not allowed to connect the electrostatic grounding with other grounding. At the same time, the grounding resistance should be measured in spring and autumn every year. For the grounding of discharging static electricity alone, the resistance shall not exceed 100 Ω. The grounding resistance of the anti-static device at the beginning and end of the oil pipeline shall not be greater than 30 Ω. The static grounding device must be used when the oil tank truck is filling oil. During the transportation of oil, the oil tank truck must have a good electrostatic grounding wire to reduce the accumulation of oil static electricity

third, avoid the formation of combustible mixed gases, and prevent oil splashing, leakage and emission during the receiving and sending of oil; Fourth, prevent human static electricity; Fifth, add antistatic agent to the oil to reduce the generation of electrostatic charge