Fire Protection Systems essay part 2
Fire Protection Systems essay part 1
Steam smothering system
Originally steam was used to extinguish fires on ships. One of the first experiments on the steam extinguishing systems were conducted in the late 19th century, and at industrial sites they have been used from the mid 20th century. Water steam has been applied in stationary installations with limited openings, at process units for extinguish outdoor fire, in chemical and petroleum industries.
Steam smothering system is based on the fact that the steam introduced into the room where the fire occurred, reduces the amount of oxygen in the combustion zone. Together with reducing oxygen concentration, there is a partial cooling of the combustion zone and a mechanical flameout with jets of steam. Extinguishing effect is achieved by 35% volume concentration of steam, provided that the equipment and building envelope are heated above the condensation temperature of steam at atmospheric pressure. Intense steam condensation occurs at lower temperatures, in this case the fire be can not extinguished. Preference is given to saturated steam, although superheated steam can also be used. Together with the dilution effect, the steam cools technological devices without causing sharp temperature stresses. In turn, the steam supplied as a compact jet, is able to mechanically detach the flame.
In confined spaces, perforated pipe outlet pair of which must have a diameter of 4.5 mm, are used as internal distribution of steam pipelines of stationary steam extinguishing systems. For dripping from the supply steam inlets, there must be provided purgers, located in the most low-lying areas along the gradient of tubes.
The steam supply into enclosed spaces, perforated pipes should be laid around the inner perimeter of the room at a height of 0.2-0.3 m above the floor. Pipe openings are arranged so that steam jets are directed horizontally into the room. The main indicator in calculation of steam extinguishing systems is the flow rate of steam. Estimated time for extinguishing is the time from the moment of steam supply to the complete elimination of extinguishing fire. Note that it should not exceed three minutes.
To prevent contact of flammable gas mixtures, resulting in accidents in the petrochemical and gas industry, with ignition sources, there is designed steam fire curtain. It must have sufficient density and range, exclusive breakthrough of combustible mixture into the protected zone of the object. Device for creation curtain of steam is an annular collector tube, along the axis of which the entire upper part of the same diameter is drilled. The collector can be placed on metal, concrete or brick piers. Collector must have drain valve for condensate discharge or precipitation. Along the axis of the collector, there is a rigid gas-tight enclosure to prevent slippage of the combustible mixture between individual jets in the initial section of the curtain. Openings in the enclosures must be closed by tight doors.
Trajectory of the jet necessarily exceeds the protected zone. Outdoor steam curtain is started in the following cases: when the signal of the device installed on the furnace control of the flame on the stove burner; when signals from the gas analyzers (detectors) for combustible gases and vapors installed in hazardous locations; when visual detection of accidents involving flammable liquids, vapors and gases; when reporting on emergency gas contamination on adjacent process units.
Steam smothering systems are typically used for cargo holds, storage for flammable materials of vessels which have boilers of sufficient capacity. Newly built riverboats don’t use steam extinguishing systems. The main drawbacks of the steam extinguishing systems are: dangerous to human life, resulting in damage to goods and mechanisms, can be used only indoors and under boilers.
Fireline systems
According to the purpose, aqueducts are divided into: drinking and sanitary, industrial and fire line. In turn, fire lines are divided into high and low pressure lines. High-pressure fire lines create pressure required to extinguish a fire in the highest building without fire trucks in 5 minutes after report of a fire. For these purposes, pumping stations or other individual rooms are equipped with stationary fire pumps. Low-pressure fire lines use fire pumps on the fire hydrants during a fire to provide the required pressure.
Plumbing facilities are designed, built and operated accounting a pass of flow of water for firefighting purposes, besides it is taken into account the maximum flow of water for drinking and industrial needs. Along with this, clean water tanks and water towers provide emergency supply of water for fire fighting, and second lift pumping stations are equipped with fire pumps. When extinguishing fires, pumping-sleeve systems assembled, which are also basic high-pressure fire lines, consisting of a water source, water intakes, suction line, pump station combined first and second lifting conduits, and water mains. In particular, culverts are designed for transporting water from the second lift pumping station to the water supply of the city or object. Water towers are used for regulating pressure and flow rate in the water supply network, and installed at its beginning, middle, or end. Water supply network is used for reliable and uninterrupted transportation of water to consumers in the required quantities under a pressure sufficient to supply water to the most remote and upstream point of the draw, as well as for fighting fires.
Water supply networks are divided into: ring and dead-end. Ring network is most often used in urban and industrial water supply systems, and blind ones are used to supply small villages, cattle farms, etc. Ring water supply networks allow disabling emergency pipeline sections without interrupting water supply in the following areas. At the same time, the total length of ring networks and their cost is much higher than the cost and length of dead-end systems. Furthermore, they attenuate the hydraulic impact. At the same time, the overall length, and hence the cost of the ring network significantly exceeds the cost and length of dead-end networks. In order water in the pipes does not freeze in winter, they are paved below the freezing depth of soil.
Fire pump system
Fire centrifugal pump is a device for supplying water to the place of extinguishing fire. Pumps are mounted on special fire equipment – motopumps, pumping stations, fire tankers. Fire pumps depending on the nature of the pressure may be of several types: normal pressure (pumps create outlet pressure to 2.0 MPa), high pressure (outlet pumps create pressure above 2.0 MPa) and combined (pumps consist of series-connected normal and high pressure pumps, which have one common drive).
The structure of fire pump system includes: impeller, body with outlet diffuser, body of bearing supports, body cap, discharge manifold, foam shifter, shutoff valve, drive shaft and sealing device, device for determining the frequency of pump control panel, and a vacuum pump. The pump is not self-priming, so before starting to work it must be filled. If the water source is an outdoor pond, first start vacuum device that sucks water into the fire pump. If the work goes from the pump tank of fire engine, it is possible to fill by the opening of valves. For normal operation of the pump, you must have the tightness of internal working cavities. Therefore, pumps are periodically checked for leaks by vacuum. Pump is not easy to make, it is a complex and time-consuming process. Most of its parts are cast through a complex and costly casting tooling. Pump parts in most cases are made of aluminum. The main problem facing the pump manufacturers is to ensure the accuracy and positioning of the internal surfaces of the flow of the pump’s body and wheels.
All systems are designed to protect people and property from the effects of fire hazards. This helps to minimize the dynamics of increase of fire hazards, evacuation of people and property to a safe area and extinguishing the fire. The main requirement for the above fire safety systems is the reliability and resistance to fire hazards. System of fire safety and protection of object includes: fire protection system, fire prevention system and a set of organizational and technical measures to ensure fire protection.
Do you like this essay?
Our writers can write a paper like this for you!
(1 votes, average: 4.00 out of 5)
Loading...