FIRE SPRINKLER SYSTEM
When considering fire sprinkler design for any building, it's important to follow the following steps:
1. Determine the fire hazard level in the building Every building should be classified for fire risk under the following categories: light hazard, ordinary hazard group 1, ordinary hazard group 2, extra hazard group 1, or extra hazard group 2. Factors involved in classifying a building's hazard level include the material used in construction, the occupancy level, the materials stored in the building, the processes performed in the building (and whether these processes include flammable liquids), ceiling heights, ease of egress, and the amount of floors and rooms.
2. Determine the design area and design density
The design area is a theoretical space within the building that's designated as the worst possible place where a fire can break out. Once determined as the highest risk area in the building, this area's risk level is usually applied to the entire building. Once that's done, determine the amount of water per square meter would be needed to put a fire out in the design area. The calculations should be done in liters of water per minute. This will help you determine the type of sprinkler heads, fire sprinkler design, and amount of water pressure you'll need.
3. Determine which fire sprinkler design will best meet your needs
You'll need to find a fire sprinkler design that can deliver the amount of water per square foot required to put out a fire in your design area. Doing this entails complex calculations that account for the initial water pressure, as well as reductions or elevations to it due to friction in the pipes, momentum from the speed the water travels, and the difference in elevation between the water pump and the sprinkler heads. Nowadays, these calculations are often performed by computer software-although fire sprinkler installation professionals are still required to learn to do them by hand as part of their when designing your fire sprinkler system, you have a lot of choices. Here are a few of the more common ones. The hazard levels they are appropriate for can vary, depending on the height and size of the building and other factors that can affect water pressure, but this list includes some examples of building types these fire sprinkler designs are generally appropriate for.
Control Mode Sprinklers are the standard fire sprinkler design. These stop a fire from spreading by dumping water directly on the fire when it starts, lowering its core temperature to the point where the fire can no longer sustain its heat. This fire sprinkler design also "pre-wets" flammable material adjacent to the fire.
Suppression Sprinklers are specially suited to work quickly and handle fast-growing and challenging fires. Instead of pre-wetting the area as the control mode fire sprinkler design does, the suppression sprinklers release a deluge of water directly on the core of the fire-lowering the temperature quickly and efficiently. This fire sprinkler design is often preferred in buildings containing highly flammable materials, as they quickly stop an already-severe fire from growing.
Fast-Response Sprinklers work more quickly than other designs. In some areas, this is the required fire sprinkler design for light-hazard occupancies.
Water Mist Sprinklers are often used on offshore oil drilling rigs and ships, as well as in areas where water damage is a special concern. Unlike many fire sprinkler designs which extinguish solely by removing the heat from a fire, the water mist fire sprinkler design attacks a fire on two fronts: its warmth and its oxygen supply. It does not douse the area, which is better for rooms containing water-sensitive equipment.
Instead of spraying water, water mist sprinklers spray high-pressure mist, which is converted to steam when it encounters the heat from the fire. When converting to steam, the mist water droplets deplete the oxygen supply in the room, effectively suffocating the fire. In addition, the water mist is a powerful cooling agent and blocks the fire's radiant heat, dropping its temperature and keeping it from spreading.
Residential sprinklers are specially designed to protect people in the room of origin from being injured by a fire. This fire sprinkler design is often the best choice for residential developers and landlords.
Decorator Sprinklers sometimes called concealed sprinklers, can be designed to blend in with the ceiling so as not to be visible. This fire sprinkler design can come in custom colors, and the sprinkler head is typically recessed. A cap is placed over the recess and colored to match the ceiling. The glue used to attach it will dissolve in case of a fire, dropping off and exposing the sprinkler head. These are often the fire sprinkler design of choice in homes.
Extended Coverage Sprinklers are designed so that each sprinkler head covers a wide area-and limits the amount of sprinkler heads needed to protect a building. This fire sprinkler design is also useful in areas with lots of flammable material, as the wide footprint for each sprinkler head will "pre-wet" surrounding materials in case of a fire. These can be installed with a residential, quick-response, or standard design.
Low-Pressure Sprinklers are designed to handle fire protection needs in tall buildings where water pressure may be reduced in the upper floors. This fire sprinkler design is often used in skyscrapers and tall tenement buildings. Using this fire sprinkler design can be more cost-effective than other designs. It will also reduce pipe size and reduce the need for a fire pump.
Early Suppression Fast Response (ESFR) Sprinklers are designed to control fires that start in storage areas piled high with flammable materials. They are typically used in high-risk storage facilities.
Wet-Pipe or Dry-Pipe are two versions of fire sprinkler design you can install. With a wet-pipe system, the water is constantly running through the pipes. This is the most common type of system, and is most typically found in residential buildings that are constantly heated. With a dry-pipe fire sprinkler design, the pipes are filled with compressed air, and hooked up to the water source via a pump or valve. When a sprinkler head is activated, the valve is tripped and water floods the pipes. This system is more difficult to maintain than a wet-pipe fire sprinkler design, but it is ideal for buildings that are not constantly heated, as they protect pipes from bursting.
Dry Pipe Fire Sprinkler System
A dry pipe sprinkler system is one in which pipes are filled with pressurized air or nitrogen, rather than water. This air holds a remote valve, known as a dry pipe valve, in a closed position. Located in a heated space, the dry-pipe valve prevents water from entering the pipe until a fire causes one or more sprinklers to operate. Once this happens, the air escapes and the dry pipe valve releases. Water then enters the pipe, flowing through open sprinklers onto the fire.
Advantages of using dry pipe fire sprinkler systems include:
- Dry pipe sprinkler systems provide automatic protection in spaces where freezing is possible.
- Typical dry pipe installations include unheated warehouses and attics, outside exposed loading docks and within commercial freezers.
Many people view dry pipe sprinklers as advantageous for protection of collections and other water sensitive areas. This perceived benefit is due to a fear that a physically damaged wet pipe system will leak while dry pipe systems will not. In these situations, however, dry pipe systems will generally not offer any advantage over wet pipe systems. Should impact damage happen, there will only be a mild discharge delay, i.e. 1 minute, while air in the piping is released before water flow.
Disadvantages of using dry pipe fire sprinkler systems include:
- Increased complexity - Dry pipe systems require additional control equipment and air pressure supply components which increases system complexity. Without proper maintenance this equipment may be less reliable than a comparable wet pipe system.
- Higher installation and maintenance costs - The added complexity impacts the overall dry-pipe installation cost. This complexity also increases maintenance expenditure, primarily due to added service labor costs.
- Lower design flexibility - There are strict requirements regarding the maximum permitted size (typically 750 gallons) of individual dry-pipe systems. These limitations may impact the ability of an owner to make system additions.
- Increased fire response time - Up to 60 seconds may pass from the time a sprinkler opens until water is discharged onto the fire. This will delay fire extinguishing actions, which may produce increased content damage.
- Increased corrosion potential - Following operation, dry-pipe sprinkler systems must be completely drained and dried. Otherwise remaining water may cause pipe corrosion and premature failure. This is not a problem with wet pipe systems where water is constantly maintained in piping.
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