What are the classifications of dust? What are the national standards?

User Conch asks: Dust environment work, on the one hand, will lead to pneumoconiosis; on the other hand, when the concentration and oxygen concentration reach a certain limit and there is an open flame, an explosion can occur, which is very harmful. What are the classifications of dust? What are the national standards for the classification of environmental hazards in dust operations?

Expert reply: Information Center of Sinosteel Wuhan Safety and Environmental Protection Research Institute Co., Ltd. Wang Xiaoxuan

What are the classifications of dust?

Productive dust can be classified from different angles:

1. Classification of substances that form dust

This is a very common classification method for different types of dust. The dust produced by coal is called coal dust, the dust produced by cotton fabric is called cotton dust, and the dust produced by asbestos is called asbestos dust.

Substances can be divided into several categories, and the corresponding dust can be divided into the following categories:

(1) Inorganic dust, including mineral dust, metallic dust and artificial inorganic dust.

1 mineral dust, such as quartz, asbestos, coal dust and so on.

2 metallic dust, such as iron, lead, zinc and its oxide dust.

3 artificial inorganic dust, such as silicon carbide, cement, glass powder and so on.

(2) Organic dust, including animal dust, vegetable dust and artificial organic dust.

1 animal dust, such as animal hair, bird hair, bone, hair dust and so on.

2 plant dust, such as grain dust, tobacco dust, tea dust, etc.

3 artificial organic dust, such as synthetic fiber, organic dye dust.

(3) Mixed dust refers to a mixture of several substances in the above-mentioned various types or similar types of dust.

2. Classification according to the production process of generating dust

Different kinds of production processes use or produce different materials to produce different dusts. Therefore, it can be classified not only by dust-forming substances, but also by various processes and different types of processes. For example, lead soot is produced during the lead smelting process, and can be classified into lead sintered soot, lead smelting soot, and lead ingot soot. Since different production processes often produce dust of different particle sizes and different physical properties, this classification is beneficial for accurate selection of dust control measures.

According to the nature of the process, the dust can be roughly divided into:

(1) Disposable soot refers to the part of soot that is directly discharged by the source of smoke.

(2) Secondary soot refers to the soot emitted by one collection and not completely excluded. The corresponding various moving and scattered soot spots are called secondary soot or unorganized soot.

At present, there is still a classification method, that is, all dust sources other than one soot, such as crushing, transportation, storage, powder field, burning and other processes or locations, are called bursting dust.

3, according to the dust particle size

According to the visible conditions of dust, it can be divided into three categories:

(1) Visible dust refers to dust with a particle size larger than 10 or more visible to the naked eye.

(2) Microscopic dust refers to dust with a particle size of 0.25-10 which can be observed by a general optical microscope.

(3) Ultra-microscopic dust refers to dust with a particle size of less than 0.25, which can only be seen under a microscope or electron microscope.

Dust particle size is different, and the depth and location of the lungs that may be inhaled are also different. In this respect, the conclusions obtained from different test conditions are not the same, and a more detailed discussion will be given in this chapter.

4, according to the physical classification of dust

Dust has a variety of properties, such as dust hygroscopicity, viscosity, flammability, electrical conductivity, etc., therefore, can be distinguished according to different physical properties:

(1) hygroscopic dust, non-hygroscopic dust;

(2) sticky dust, slightly sticky dust, medium sticky dust, strong sticky dust;

(3) combustible dust and non-burning dust;

(4) high specific resistance dust, general resistance value dust, conductive dust;

(5) Soluble dust and insoluble dust.

5, according to the mechanism of dust damage to the human body

Different dusts have different mechanisms for causing disease in humans. According to this different nature, dust can be classified, for example, into:

(1) Dust containing free ceria dust or more silica-containing dust, such as quartz dust, talc, mica dust, etc. Inhalation of this dust will cause fibrosis of the lung tissue and form a nodule.

(2) Asbestos dust is a dust with a fibrous structure, and inhalation of such dust will cause asbestosis and induce tumor disease.

(3) Radioactive dust inhalation into the human body will cause radiation damage.

(4) Toxic dust such as lead dust, dust containing partitions, manganese and chromium, will cause various poisoning symptoms when inhaled into the human body.

(5) Generally non-toxic dust such as coal dust, cement dust, etc., long-term inhalation of the human body will lead to various pneumoconiosis.

What are the national standards for the classification of environmental hazards in dust operations?

GB/T5817-2009 "Dignity Classification of Dust Workplaces" was approved by the National Standards Committee and was implemented on December 1, 2009. This standard is a revision of the GB5817-1986 "Classification of Hazard Levels of Productive Dust Operations". The standard uses the dust concentration exceeding the standard as a grading indicator of the degree of hazard in the dust workplace, which helps enterprises to strengthen the hierarchical management of dust workplaces, improve the environmental conditions of workplaces, protect the health of employees, promote the harmonious development of enterprises, and also supervise and manage occupational health. The department provides a basis for the supervision of dust workplaces.

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