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What Are The Four Types of Fire Sprinkler Systems ?

What Are The Four Types of Fire Sprinkler Systems?

Fire sprinklers are used to minimize injuries and death in an emergency fire. These systems work to suppress the spread of fire and heat damage, which can cut off escape routes or cause structural collapse. Many insurance companies offer discounts on houses and shops equipped with fire sprinkler systems. Sprinkler systems designs are based on the requirements of local building codes usually by a licensed engineer or architect. The National Fire Protection Association (NFPA) is the most popular standard for fire sprinklers design. NFPA standard 13 describes types of sprinkler systems, materials, installation, and instructions.
the four types of fire sprinkler systems

Design basics

Sprinkler design is based on the size of a building and the potential for fire. NFPA 13 categorizes types of hazards in a building as:

1. light hazard
2. ordinary hazard
3. extraordinary hazard

Buildings which fit the ordinary hazard category are a low risk of fire and contain non-combustible materials that produce a fire, or a very high heat. In general, extraordinary hazards occure in industrial areas , where there is a presence of chemicals or flammable materials.

On the basis of these categories, NFPA suggests appropriate flow rates, which should be released in case of fire. These flow rates are applied for each square foot of building space. For example, a minor hazard requires 1 gallon of water per minute. If the building is 5,000 square feet in space, the sprinkler system is designed to release 5,000 gallons of water per minute. Water pressure and type of material are also determined according to the volume of the project and the type of the system.

The fire sprinkler fusable bulb is broken and water is released
The fire sprinkler fusible bulb is broken and water is released

Types of fire sprinkler systems:

1. Wet system:

The most common sprinkler design system is the traditional wet pipe system. This system is pretty simple, compared to other designs. Just pipes, water supply, pipe fittings and sprinkler heads. The tubes are filled with water, which is released only in case of fire.

The sprinkler heads contain a defusable element, such as a metal chain or filaments. Exposed to high heat, this element will be broken, allowing the sprinklers to operate. With a wet pipe system, only the sprinkler heads work after exposition to a predetermined heat . 

2. Dry system:

Dry systems are used in areas where wet systems would be used inefficiently, for example, the water could be frozen. These include places such as warehouses and garages.

With a dry sprinkler system, there is no water in the pipes. Instead, the tubes are filled with air, which holds the water back at its root and keeps it filled the pipes. When the element on the sprinkler head is broken due to heat, the air rushes out of the head. This is used to fill the water in the pipes, and then exit through the sprinkler heads. There is a small delay when using a dry-system design, as it takes time for the air to leave the pipe and then water reaches the heads.

The fire pump room
The fire pump room

3. Chemical system ( Foam system ):

Some sprinkler designs are based on foam or chemicals rather than water. Foam is typically put into sections, in serious fire hazards it fights the fire more effectively than water. Chemical systems are used in areas in which water can cause damages such as museums and computer rooms. These systems use traditional sprinkler pipes and heads, but based on chemicals such as halon to suppress the fire. Halon works by absorption of oxygen in the room, which stops the spread of fire. Chemical systems must be designed carefully, due to environmental, health or related products risks.

4. Pre-action system:

Pre-action systems are an alternative to chemical sprinklers. They are often placed in museums or buildings which contain expensive equipment. Pre-action systems start with dry pipes, the system gets a signal from a fire alarm or smoke detector, a valve is opened, and the system is changed from dry to wet.

Before water is released from the pipes, the sprinkler will receive a second signal, may be an electronic signal from the building fire alarm system. After this second signal is activated, water is released from the pipes in the traditional way. A pre-action system offers the advantages of the dry system without any delay caused by air pipes.