Foam fire extinguishing systems and other types of systems: characteristics and application.

Foam fire extinguishing installations and other types of installations: characteristics and application.

Foam fire extinguishing systems and other types of systems: characteristics and application

Foam fire extinguishing systems
Foam fire extinguishing systemsare used primarily to extinguish flammable liquids and combustible liquids in tanks, flammable substances and petroleum products located both inside buildings and outdoors. Foam fire extinguishing units are divided into deluge and sprinkler. Deluge units are used to protect local areas of buildings, electrical equipment, transformers. Sprinkler and deluge water and foam fire extinguishing units have a fairly similar purpose and design. Foam fire extinguishing unitsare distinguished by the fact 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 that supply the foaming agent to the pipeline are used as dosing devices for such installations; automatic dosing devices with a Venturi pipe and a diaphragm-plunger regulator. With an increase in water flow, the pressure drop in the Venturi pipe increases, the regulator provides an additional supply of foaming agent; ejector-type foam mixers; dosing tanks that use the pressure drop created by the Venturi pipe. Automatic foam fire extinguishing installations were first developed at VNIIPO in 1960-1963. Their basic diagrams differed little from the diagrams of sprinkler and drencher water fire extinguishing installations. A dosing foaming device was additionally installed and the design of the foam sprinkler (foam generator) was changed. Automatic foam fire extinguishing systemsare currently widely used in the national economy, and sprinklers of the OPS and OPD types are mass-produced by industry. In subsequent years (1965-1968), such schemes were used in automatic fire extinguishing installations for tanks with flammable liquids. Stationary generators of the GVP type are used as foam-forming devices in them. Improvement of stationary foam fire extinguishing installations is associated with the development of new foaming agents, designs of foaming and dosing devices. In 1976, VNIIPO obtained gas-mechanical foam, the bubbles of which are filled with freon vapors, and proposed a fire extinguisher design using freon-mechanical foam. Automatic foam fire extinguishing installationsfoam generators with a concentration of 3 to 6% are used to obtain air foam. Foam consists of air bubbles, water and foam generator. When extinguishing a fire, it creates a cover of flammable liquids or other substances, preventing oxygen from reaching the fire and cooling the source of fire. An important characteristic of foam is its stability (it decomposes very slowly) and the ability to quickly extinguish a fire. Foam composition has its own classification: — low expansion foam — heavy foam, foam expansion ratio 4 — 20 (foam sprinklers, foam generators, nozzles);
— 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 unitsinclude a water supply source, a foam supply system, distribution valves and a distribution pipeline with nozzles (foam sprinklers, foam chambers, foam generators, nozzles).