FIRE FIGHTING SYSTEMS
A fire-fighting system is probably the most important building services, because its purpose is to protect human life and property, strictly in that order. It consists of three fundamental parts:
A large tank of water in tanks, either underground or on top of the building, called fire storage tanks
A specialized pumping system, and Sprinkler
A large network of pipes terminating in either hydrants or sprinklers (almost all buildings require both)
A fire hydrant is a vertical steel pipe with an outlet, to which two fire hoses are stored (a hydrant is called a vertical tube in America). During a fire, firefighters go out, break the pipes, attach one to the outlet, and open manually so that the water rushes out of the nozzle of the pipe. The quantity and speed of water is so great that it can hit the fireman holding the pipe if it is not standing in the correct direction. As soon as the fireman opens the hydrant, the water will gush and the sensors will detect a drop in pressure in the system. This pressure drop will trigger the fire pumps to turn on and start pumping water at a considerable flow.
A sprinkler is a nozzle attached to a connected pipes installed just below the roof. Each sprinkler has a small glass bulb with a liquid in it. This bulb normally blocks the flow of water. In a fire, the liquid in the bulb will become hot. It will widen and break the glass bulb, removing the obstacle and spraying water from the sprayer. The main difference between a fire hydrant and a sprinkler is that a sprinkler will automatically fire in a fire. A fire hydrant must be operated manually by trained firefighters – it can not be used by lay people. A sprinkler is usually activated very quickly in a fire – perhaps before the fire station has been informed of the fire – and is therefore very effective in extinguishing a fire in the early stages, before it develops into a fire. A great fire. For this reason, a watering system is considered very good at extinguishing fires before they spread and become unmanageable. According to the NFPA of America, hotels with sprinklers suffered 78% less material damage caused by fire than hotels without a study in the mid-1980s.
The amount of water in the fire storage tanks is determined by the level of risk of the project under consideration. Most building codes have at least three levels, namely Light Hazard (such as schools, residential buildings and offices), Ordinary Hazard (like most factories and warehouses) and High Hazard (places that store or use Flammable materials such as foam factories, aircraft hangars, paint plants, fireworks factories). The relevant building code indicates which type of structure belongs to each category. The amount of water to be stored is usually given in hours of pumping capacity. In a one-hour system, the tanks are large enough to supply the fire with water for a period of one hour when the fire pumps are turned on. For example, building codes may require that fire protection systems have a capacity of one hour and a high risk of 3 or 4 hours of capacity. Water is usually stored in underground concrete tanks. It is essential to ensure that this water tank is always full, so that it must not have outlets outside those that lead to the fire pumps. These tanks are separated from the tanks used to provide water to the occupants, which are usually called domestic water tanks. Designers will also try to ensure that the water in the fire reservoirs does not stagnate and develop algae that could clog the pipes and pumps, making the system unnecessary in a fire.
Fire pumps are usually housed in a pumping room very close to the fire tanks. The key is that the pumps should be located at a level just below the bottom of the fire tank, the pump takes water from the tank that flows with the presure. most important systems, there must be emergency pumps in the event of a failure of the main pump. There is a main electric pump, a electric backup pump, and a second backup pump works with diesel, in case the electricity fails, which is common. Each of these pumps is capable of pumping the required amount of water by itself – they are individual in capacity. There is also a fourth type of pump called jockey pump. It is a small pump attached to the system that is continuously activated to maintain the correct pressure in the distribution systems, which is normally 7 Kg / cm2 or 100 psi. If there is a small leak somewhere in the system, the jockey pump will turn on to compensate. Each jockey pump will also have a backup. The pumps are controlled by pressure sensors. When a firefighter opens a fire hydrant, or when a sprinkler is lit, water springs from the system and the pressure drops. The pressure sensors will detect this fall and turn on the fire pumps. But the only way to turn off a fire pump is for a firefighter to do it manually in the pump room. This is an international code of practice designed to prevent pumps from turning off due to malfunction of the control system. The capacity of the pumps is determined by considering a number of factors, some of which are:
The area covered by hydrants and sprinklers
The number of hydrants and sprinklers
The supposed operating area of the nozzles
The type and layout of the building.
The distribution system
The distribution system consists of pipes made of steel or galvanized steel painted red. These can be welded together to make secure joints, or tied with special clamps. When they run underground, they are wrapped with a special coating that prevents corrosion and protects the pipe. There are essentially two types of distribution systems. Automatic wet systems are networks of water-filled pipes connected to pumps and storage tanks, as described heretofore. Dry automatic systems are networks of pipes filled with pressurized air instead of water. When a firefighter opens a fire hydrant, pressurized air rushes first. Pressure sensors in the pump room will detect a pressure drop and start the water pumps that will pump water to the system and reach the fire hydrant that the fireman keeps after an interval of a few seconds. This is done wherever there is a risk of freezing fire hoses if filled with water, which would render them unnecessary in a fire. Some building codes also allow for manual distribution systems that are not connected to fire pumps and fire tanks. These systems have an entrance for firefighters to pump water into the system. Once firefighters pump water into the distribution system, firefighters can open fire hydrants in the right places and start directing the water to the fire. The input that allows the engine water from the fire in the distribution system is called a Siamese connection. In high-rise buildings, it is mandatory that each staircase have a wet riser, a vertical fire hose with a hydrant on each floor. It is important that the distribution system is designed with a main ring, a main loop that is connected to the pumps so that there are two ways for the water to flow in case one side is blocked.
In more complex and hazardous installations, high and medium speed water spray systems and foam systems (for hazardous chemicals) are used. The foam acts as an insulating blanket on top of a burning liquid, cutting off its oxygen. Special areas such as server rooms, whose contents are damaged by water, use gas suppression systems. In these, the gas is pumped into the pipelines in the room to cut off the oxigen supply to the fire.
When designing a firefighting system, remember the following:
Underground Tanks: Water must flow from the municipal supply first to fire-extinguishing tanks, then to domestic water tanks. This is to prevent stagnation in the water. The overflow from fire fighting to domestic tanks must be at the top, so that the fire-fighting tanks remain full at all times. Normally, fire fighting water should be separated into two tanks, so that if one is cleaned there is water in the other tank in case of fire.
It is also possible to have a system in which the fight against fire and domestic water are in a common tank. In this case the outlets of the fire pumps are located at the bottom of the tank and the outlets of the domestic pumps must be located at a sufficient height from the floor of the tank to ensure that the total quantity of water required for fire Is never evacuated by domestic pumps. The connection between the two tanks is via the suction manifold, a large diameter pipe that connects all the fire pumps in the pump chamber. It is therefore not necessary to provide a sleeve in the common wall between the two fire-fighting tanks.
The connection of each tank to the suction header must be placed in a sump; If the connection is placed 300mm above the bottom of the tank without a sump, then a 300mm high water basin will remain in the tank, which means that the entire volume of the tank water will not be usable . Ideally, the bottom of the fire hall should be located about 1 m below the bottom of the tank. This arrangement ensures positive suction for the pumps, which means they will always have water. All pumping chambers must have a soil drainage system; The pumps are still leaking. The best way to do this is to slope the soil to a sump, and install a dehydration pump if the water can not flow by gravity. In cases where there is an extreme shortage of space, submersible pumps may be used for firefighting. This will eliminate the need for a fire hall.
Create a special tree for the wet risers next to each staircase. Approximately 800 x 1500 mm should suffice. It is best to provide this on the main landing rather than the average landing, as the pipes will reach further on the floor.