Provided for in the design of buildings and facilities fire prevention measures depend primarily on the fire or explosion hazards are placed in separate rooms and facilities. The premises and buildings are generally divided on the extent of fire or explosion into five categories according to the ONTP-24.
Category A – is the premise that use flammable liquids with flash point below or 28oS and combustible gases in such quantities that they can form an explosive mixture with air, an explosion which will create pressure for more than 5 kPa (eg, storage of gasoline).
Category B – this is the room in which the passing stand-suspended combustible fibers or dust, and flammable liquids with flash point over 28oS in such numbers that they formed with the air mixture in the explosion may create pressure over 5 kPa (hay-making workshop flour milling and separation vyboynye mills and kruporushek, black oil, agriculture, and power boiler). Learn more about safety degree!
Category B – this is the room in which the process or store solid combustible substances, including releasing dust or fibers, unable to create explosive mixtures with air and flammable liquids (sawmills, carpentry, and animal feed shops, shops, dry primary processing of flax and cotton; kormokuhni, grain cleaning offices mills, closed stores of coal, storage of fuel and lubricants without gasoline, electric, or RU substation with transformers).
Category D – a space in which fuel is burned, including gas, or treated with fire-retardant material in the hot, incandescent or molten state (boilers, forges, engine rooms, diesel power).
Category D – is the room in which inflammable substances are found in virtually cold (irrigation pumping stations, greenhouses, except for the heated gas, workshops on processing vegetables, milk, fish, meat).
Categories for the production of fire danger to a large extent determine the requirements for the design and planning solutions buildings and structures, as well as other issues of security against fire and explosion. They meet the standards for technological design or special lists approved by the ministries (departments). Guidance for this can serve as “Notes on the definition of the category of productions for the explosive, explosion and fire hazard” (SN 463-74) and “Methods of categorization of the chemical industry for the production of explosive, explosion and fire hazard.”
Terms of fire in buildings and structures are largely determined by their degree of fire resistance (the ability of a building or structure as a whole to resist destruction by fire). Buildings and structures for fire resistance are divided into five classes (I, II, III, IV and V). The degree of fire resistance of buildings (structures) depends on the flammability and fire resistance of the main building structures and the spread of fire in these structures.
For flammability constructions are divided into fire-proof, nonflammable and flammable. Fireproof structure made of fireproof materials, nonflammable – from the slow-combustible or protected from fire and high temperatures fireproof materials (such as fire doors, made of wood and covered with asbestos sheet roofing, and steel).
Fire resistance of building structures is characterized by their fire-resistance rating, which is defined as the time in hours, after which they lose or enclosing the bearing capacity, ie, can not perform their normal operational functions.
Loss of carrying capacity means the collapse of the structure.
The loss of a protecting power – heating structures during a fire up to temperature, the excess of which can cause spontaneous ignition of substances that are in adjacent buildings or structures in the formation of through cracks or holes through which the combustion gases can penetrate into the neighboring room.
Limits of fire resistance of structures set empirically.
For this sample design, made a life-size, placed in a special furnace and simultaneously act upon it with the required load.
From time to start testing until one of the signs of loss of carrier or a protecting power, and is considered to be fire-resistance rating. Limiting heating design is to increase the temperature on the unheated surface of the average by more than 140oS or at any point on the surface is higher than in the 180oS compared with the temperature of the design before the test, or more than 220oS regardless of the temperature of the structure before the test.
The lowest limit of the fire have unprotected metal construction, and the largest – reinforced concrete.
The required degree of fire resistance of industrial buildings industrial enterprises depends on the placement of fire danger in these industries, the area between fire walls, floors and number of storeys of the building. The required degree of fire resistance must match the actual degree of fire resistance, which is determined from the tables of SNiP II-2-80, containing information about the range of fire resistance of building structures and limits the spread of fire on them.
For example, the main parts of the buildings I and II degree of fire resistance are fireproof, and differ only by the limits of fire resistance of building structures. In buildings of I degree the spread of fire on the main building structure is not allowed at all, and in the buildings of a maximum limit of II degree of spread of 40 cm, is allowed only for internal load-bearing walls (septa). The main parts of buildings V degree are combustible.