In recent years, there have been a number of fire and explosion accidents in chemical enterprises in China, and once the chemical accident occurs, it will not only cause huge economic losses, but also cause major casualties, and the leakage of chemical raw materials will also cause major pollution of the environment, which can be described as infinite harm.

Take Shandong Yantai Wucailong gold mine “ 1.10 throughout the &; In terms of the explosion accident, fire and deflagration occurred respectively in the gas division unit of Baling Petrochemical on January 9 and the butadiene rubber unit of Yangzi Petrochemical on January 12. At about 17:06 on January 12, 2021, the butadiene intermediate tank of the butadiene recovery unit of Nanjing Yangzi Petrochemical Rubber Co., LTD., a butadiene device, exploded, but fortunately the accident did not cause casualties. After the preliminary investigation and analysis of the relevant departments, the cause of the accident may be: butadiene reaction in the butadiene intermediate tank to form peroxide and gather, the decomposition of the peroxide in the tank to cause butadiene polymerization reaction intensified, release a lot of heat, resulting in a sharp rise in pressure, exceeding the maximum working pressure of the storage tank, overpressure caused equipment rupture, butadiene leakage, resulting in dedetonation.

So through the above things, we understand the importance of the safety of flammable and explosive places, then how do we divide dangerous places? Let's take a look at the classification of dangerous places.

Classification of dangerous places:

According to the classification of hazardous environments formulated by the International Electrotechnical Commission (IEC), under atmospheric conditions, dust or fibrous combustible substances forming a mixture with air are burned after ignition and transmitted to the environment of not all unburned mixtures for explosive dust environment, called Class I environment; Under atmospheric conditions, the environment in which a mixture of gases, vapors or mist-like combustible substances forms with air and burns to all unburned mixtures after ignition is an explosive gas environment, called a Class II environment.

Hazardous sites are areas where hazardous environments occur or are expected to occur in such quantities as to require special measures for the construction, installation and use of electrical equipment. Hazardous sites are divided into different areas according to the frequency and duration of explosive environments.

1. Division of hazardous areas for explosive dust environment

According to the frequency and duration of occurrence of combustible dust/air mixture and the thickness of the dust layer, the classification can be divided into 20, 21 and 22 zones.

zone 20: In areas and inside containers where combustible dust occurs continuously or frequently during normal operation in quantities sufficient to form mixtures of combustible dust with air and/or where uncontrollable and extremely thick dust layers are likely to form.

zone 21: In zone 21, the amount of dust that may occur during normal operation to form a mixture of combustible dust and air is not classified as Zone 20. This area includes sites directly adjacent to the point of inrush discharge, where dust layers occur, and where mixtures of combustible dust and air may be produced in combustible concentrations under normal operation.

zone 22: zone 22, under abnormal conditions, flammable dust clouds appear occasionally and exist only for a short time, or flammable dust occasionally accumulates or may exist dust layers and produce flammable dust air mixtures. If it is not possible to guarantee the exclusion of combustible dust accumulation or dust layer, it should be divided into 21 zones.

2. Classification of dangerous areas in explosive gas environment

Hazardous sites are divided into zones 0, 1 and 2 according to the frequency and duration of the occurrence of combustible gases.

zone 0: zone 0, where the explosive gas environment occurs continuously or exists for a long time, and the hazardous environment exists for more than 1000 hours/year.

zone 1: zone 1, a place where an explosive gas environment may occur during normal operation, and the hazardous environment exists for between 10 and 1000 hours/year.

zone 2: zone 2, in normal operation, there is no possibility of explosive gas environment, if it occurs occasionally and only for a short time, the hazardous environment exists for less than 10 hours/year.

Here, “ Normal operation ” It refers to the normal driving, operation, parking, loading and unloading of flammable substances, the opening and closing of closed container covers, safety valves, discharge valves and all factory equipment are working within the scope of their design parameters.