Foam fire extinguishing installations and other types of installations: characteristics and application
Foam fire extinguishing installations
Foam fire extinguishing installations are used primarily for extinguishing flammable liquids and flammable liquids in flammable tanks substances and petroleum products located both inside buildings and in the open air. Foam fire extinguishing installations are divided into deluge and sprinkler systems. Deluge installations are used to protect local areas of buildings, electrical devices, and transformers. Sprinkler and deluge installations for water and foam fire extinguishing have a fairly similar purpose and design. Foam fire extinguishing installationsThey differ in that they have a reservoir with a foaming agent and dosing devices; in addition, they are characterized by separate storage of the components of the fire extinguishing agent. Dosing pumps are used as dosing devices for such installations, ensuring the supply of foam concentrate to the pipeline; automatic dispensers with Venturi tube and diaphragm-plunger regulator. With an increase in water flow, the pressure drop in the Venturi pipe increases, the regulator provides the supply of an additional amount of foam concentrate; ejector-type foam mixers; dosing tanks using the pressure difference created by a Venturi tube. Automatic foam fire extinguishing installationsfirst began to be developed at VNIIPO in 1960-1963. Their schematic diagrams differed little from the diagrams of sprinkler and deluge water fire extinguishing installations. A metering foaming device was additionally installed and the design of the foam sprinkler (generator for foam formation) was changed. Automatic foam fire extinguishing installationsCurrently, they are widely used in the national economy, and OPS and OPD type sprinklers are mass-produced by industry. In subsequent years (1965-1968), such schemes were used in automatic fire extinguishing installations for tanks with flammable liquids. They use stationary generators of the GVP type as foam-forming devices. The improvement of stationary foam fire extinguishing installations is associated with the development of new foam concentrates, designs of foam-forming and dosing devices. In 1976, VNIIPO produced gas-mechanical foam, the bubbles of which were filled with freon vapor, and proposed a fire extinguisher design using freon-mechanical foam. Automatic foam fire extinguishing installationsFoaming agents with concentrations of 3 to 6% are used to produce airy foam. Foam consists of air bubbles, water and a foaming agent. When extinguishing a fire, it creates a cover of flammable liquids or other substances, preventing the access of oxygen and cooling the fire. An important characteristic of foam is its stability (decomposes very slowly) and the ability to quickly extinguish a fire. The foam composition has its own classification: — low expansion foam — heavy foam, foam expansion ratio 4 — 20 (foam sprinklers, foam generators, barrels);
— medium expansion foam — expansion ratio 2 — 200 (stationary installations);
-high expansion foam — light foam, expansion 200 — 1500 (light foam generators). Similar types of fire extinguishers also contain similar foam substances.
Air foam is used to extinguish fires of flammable liquids in: industrial facilities, warehouses, tankers for transporting oil and flammable chemicals, oil refineries and chemical plants. Stationary foam fire extinguishing installationsinclude a water supply source, a foam concentrate supply system, distribution valves and a distribution pipeline with nozzles (foam sprinklers, foam chambers, foam generators, nozzles).
Automatic gas fire extinguishing installations
Automatic gas fire extinguishing installationsare a set of stationary technical fire extinguishing equipment for fighting fire in fires through the automatic release of a gas extinguishing agent. Constructivelyautomatic gas fire extinguishing installationsare divided into two types: centralized and modular. Liquefied and compressed gases are used as fire extinguishing agents. The following liquefied gases are used: freon, hexaphosphorus sulfur and carbon dioxide. Compressed gases — nitrogen, argon and inergen.
Automatic gas fire extinguishing installationsIt is advisable to use in cases where the use of water can cause a short circuit or other damage to equipment, so they are used in server rooms, data warehouses, libraries, museums, and on aircraft. Such systems provide the ability to delay the supply of a gas extinguishing agent, for example, this may be necessary to evacuate people from a dangerous area. It is also possible to create a fire extinguishing concentration of a gas extinguishing agent in the protected volume or above the surface of the burning material during the time required to extinguish the fire. The gas fire extinguishing system is also included as an integral part in explosion suppression systems and is used to neutralize explosive mixtures.
Powder fire extinguishing installations
Installations Powder fire extinguishinguses fire extinguishing powder. They are used to localize and eliminate fires of classes A, B, C and electrical equipment, in particular, live electrical installations. Such installationscan be used to localize or extinguish a fire in a protected area, local extinguishing of a part of the area or volume, or extinguishing the entire protected volume. Powder fire extinguishing installations do not provide complete cessation of combustion and should not be used to extinguish fires of flammable materials that are prone to spontaneous combustion and smoldering inside the volume of the substance (sawdust, cotton, grass flour, paper); chemicals and their mixtures, pyrophoric and polymeric materials prone to smoldering and burning without air access. Powder fire extinguishers are used in the same conditions.