2020-07-01
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| Category of rooms | Characteristics of substances and materials that are (traded) in the room |
| А explosive | Combustible gases, flammable liquids with a flash point of not more than 28°C in such an amount that steam-gas-air may form explosive mixtures, which develops when ignited estimated overpressure explosion in the room of more than 5 kPa. The substances and materials capable of burning and exploding in contact with water, air or oxygen with one another in such a quantity that the calculated excess explosion pressure in the room exceeds 5 kPa |
| B explosive | Flammable dust or fibers, flammable liquid with a flash point above 28°C, combustible liquid in such an amount that can form explosive dust-air or steam-air mixture, the combustion of which develops rated overpressure explosion in the room of more than 5 kPa |
| C (В1-В4) flammable | Flammable and nonflammable liquid, solid combustible and fire-retardant substances and materials (including dust and fibers), substances and materials capable of interacting with water, air or with each other only to burn, under the condition that the room in which they are in the presence or turning, do not apply to category A or B |
| D (Г) | Non-combustible substances and materials in the hot, hot or molten state, the processing of which is accompanied by the release of radiant heat, sparks and flames; flammable gases, liquids and solids, that are burned or disposed of as a fuel |
| E (Д) | Non-combustible materials and substances in the cold |
After establishing categories of rooms it is necessary to set a category of entire buildings in which these premises are. The building belongs to the category A, if the total area of the spaces of category A is greater than 5% of the area of all premises or 200 m2.
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The building relates to the category B, if the total area of the premises of categories A and B is greater than 5% of the area of all premises or 200 m2 (but floor space of category A is less than 5% or 200 m2).
If the premises are equipped with automatic fire-fighting units, the buildings in categories A or B corresponding area of the premises should not exceed 25% of the total floor space of 1000 m2 and 3500 m2 (building category C(B)) and 5000 m2 (building category D).
Rules for Electrical Installations regulate the electrical device in production facilities and in external processing plants, based on the classification of hazardous areas, and mixtures thereof. Explosive zones are characterized by the ability to release flammable gases, flammable liquids or combustible dusts with lower flammable limit less than 65 g/m3.
For the class B-I zone areas are related, in which can form explosive mixtures in the amount of more than 5% of the volume space (under normal operating conditions) can be formed.
Zone of the class B-IA includes areas and premises in which an explosive mixture in the amount of more than 5% of the volume space is formed only in the case of accidents and malfunctions.
Zone of the class B-IB includes areas and premises in which the presence of flammable gases and vapors with lower concentration limit LCL more than 15% by volume, as well as possessing a pungent smell; a local explosive mixtures in the amount of less than 5% of the volume of the room can be formed.
Zone of the class B-IG includes outdoor installations which contain combustible gases and flammable liquids.
Zone of the class B-II includes areas and premises, in which explosive dust-air mixtures under normal operation can be formed.
Zone of the class B-IIA includes areas and premises, in which explosive dust-air mixtures only in case of accidents and malfunctions can be formed.
Fire hazard zones in the Rules PUE include rooms and outdoor installations, comprising: zone P-I – areas with combustible liquids; zone P-II – combustible dust with LCL more than 65 g/m3; zone P-IIA – solid combustible materials, do not able to form explosive mixtures; zone P-III – outdoor installations with combustible liquids or solid combustible materials.
As already noted, GOST 12.1.004-91 «Fire safety. General Requirements» provides a definition of the probability of exposure to people (fire hazardous factors) qfhf and its comparison with the standard probability of the exposure Q fhf (it assumed to be equal 10-6 / year):
qfhf <Q fhf .. (9.2)
Achieving the desired impact on the probability of fire hazardous factors staff starts with the proper designing or choice of industrial building. It is considered to be properly designed in the case along with the decision of functional, strength, health, and other technical and economic problems provided the fire safety conditions.
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Control questions for self-examination:
1. What is the fire safety of the object?
2. What are the key regulations governing the requirements for fire and explosion safety of industrial facilities?
3. List various fire hazards.
4. What groups of combustibility of substances do you know?
5. What are the parameters estimated fire and explosion safety of industrial facilities?
6. List the types of combustion.
7. What is the purpose of determining the flash point? What is the ignition temperature?
8. Method of determining the flash point and ignition temperature of the liquid fuel.
9. Tell about methods of fire and explosion hazard assessment for enterprises.
10. What are the premises for the category of fire and explosion?
11. What is the quantitative measure of categorization of premises?
12. Classification of hazardous areas and the mixtures according to the Rules for Electrical Installations.
13. Method for determining the category of fire and explosive objects.
Laboratory work 10
Means and methods of extinguishing fires. Fire prevention
Objective: learning the basic activities that provide fire prevention; learn how to have emergency exits, directions and dimensions of escape routes; learn the basic means and methods of extinguishing fires.
