FIRE SPRINKLER AND FIRE ALARM SYSTEMS
Supposing a fire occurs in the dead of the night, and no one is home except you, and you're so deep in sleep, what happens? Well, if you have a properly installed fire alarm and sprinkler systems, then there’s at least a good line of defense to help manage the situation until help arrives.
The major question always asked is if you can replace either with the other, and this illustration answers that: fire alarms notify you that a fire has started while fire sprinklers contain or even extinguish the fire before external help comes. This article will give detailed explanations about the design of fire alarms and sprinklers as well as their functions.
What Is a Fire Alarm System?
A fire alarm system is an electronic gadget installed in a building for detection of fire accidents. When the sensors pick up fire signals, they immediately alert occupants of a building. Automatic fire systems are able to detect fire signals by monitoring fire-related environmental changes. According to fire alarm safety regulations, buildings in the US should be equipped with adequate fire detection/alarm systems. Refusing to install a functional fire alarm system is a risky action that puts a building and its occupants at risk. Also, depending on the jurisdiction, it can attract serious regulatory complications for non-compliance.
Types of Fire Alarm Systems
Fire alarm systems could be automatic or manually actuated. Nowadays the manually-activated systems are no more in vogue as they require a person who detects a fire to notify other occupants of the building of a fire accident, and this is not as efficient, because if no one notices the fire accident early enough, everyone is still at risk.
Automatic fire alarm systems detect fire signals and immediately notify occupants that a fire outbreak has occurred and thus the building should be evacuated. Also, these automatic fire alarm systems send signals outside the premises so as to alert emergency services and prepare the building to control the spread of the fire.
Advantages of Fire Alarm Systems
There are a couple of benefits a fire alarm system offers beside the obvious task of detecting fire outbreaks and notifying a building's occupants. For instance, they are reliable and so occupants need not worry much about the loss of lives and property in the event of a fire due to undetected fires.
Also, there is the added benefit of merging a fire alarm system and a burglary alarm system in one, thus shooting two birds with a single stone. The other advantage is that fire alarm systems provide remote monitoring services as they notify persons outside the building of the fire outbreak, thus providing assistance to persons who may be trapped in the fire quickly.
Design of Fire Alarm Systems
There are requirements for installing, testing and maintaining fire alarm systems contained in the NFPA Code 72. NFPA stands for the National Fire Protection Association.
There are different variations of fire alarm systems with different functions and designs. Recently, there have been improvements on how occupants are alerted which include voice messaging, vibrating pads, text messages and high output visual alarms. These innovations make it easier to tailor specific solutions to each building and design unique alarm systems that best resonates with occupants.
What is a Fire Sprinkler System?
The first defence a building's occupants have against a fire outbreak is a functional fire sprinkler system.
When the fire sprinklers detect heat that is fire-sensitive, they become activated and spray water to both douse the fire, as well as wet surfaces so as to deprive them of combustive abilities. They also prevent flashovers, which refers to a situation where everything in a room is suddenly ignited when it reaches auto-ignition temperature. Some sprinkler systems are designed to totally douse and extinguish fires in more dense environments like a storage facility.
Types of Fire Sprinkler Systems
The National Fire Protection Association specifies various types of fire sprinkler systems required for various buildings. It is necessary to first determine the right design for the building in order to ensure proper functioning and performance in the event of a fire. Different types of buildings - residential buildings, commercial buildings, data centers, restaurants, and so on - all require different designs of fire sprinkler systems.
Design of Fire Sprinkler Systems
Designing a fire sprinkler system is very complex. It requires a licensed professional engineer to design.
The design follows five different steps outlined below.
1. Evaluating the water supply
2. Understanding the building
3. Determing what standard to use
4. Determining what type of pipes are required
5. Determing the amount of water required
1. Evaluating the water supply:
The very first step in the design on a fire sprinkler system is to determine the building's water supply, because everything a sprinkler does is dependent on water. An automatic water supply is required for sprinkler systems, thus no human intervention is required for the water that flows through the sprinkler system. There are many sources of automatic water supply including ponds, reservoirs, rivers, pressure tanks, water tanks, gravity tanks, water towers, or more commonly, the city water.
Whatever source is used, the important factor is its capacity to control fire, which is determined by the flow rate (calculated in Gallons per Minute, GPM), pressure (calculated in Pounds per Square Meter, PSM), and duration (the amount of time it can maintain the required flow and pressure). A flow test performance is often used to determine these at a nearby fire hydrant.
Normally, two hydrants are needed to perform this test; A and B. While no water is flowing from both hydrants, a static pressure reading is taken at hydrant A; and then hydrant B is opened for another pressure reading to be taken at hydrant B. This pressure reading identifies the amount of pressure required to push water through sprinkler heads. The tool used in measuring the pressure of water flowing from hydrant B is called a pitot tool.
This water supply capacity test is the most fundamental aspect of designing a fire sprinkler system, because almost all the other steps involve ensuring the hydraulic demands do not exceed this capacity.
2. Understanding the building:
It is just as important to know and understand the exact building where the fire sprinkler will be installed so as to ascertain what kind of sprinkler the building requires. Designers of fire sprinkler systems need to first study the architectural and engineering plans of the building before they begin further work. Is the building a commercial structure or a residential building? What is the fuel load? etc
3. Determing what standard to use
The next step is to determine which sprinkler standard suits the building. For commercial buildings, the NFPA 13 is the standard. This standard has full sprinkler coverage and is used in offices, warehouses, industrial buildings and mercantile spaces.
Low-rise residential buildings will require the NFPA 13R standard, while one- or two- family dwellings require NFPA 13D, both of which are affordable and convenient and don't require the availability of sprinklers in vacant spaces such as attics and closets. However, some larger residential buildings still require full-coverage NPFA 13 sprinkler systems.
4. Determining what type of pipes are required:
After noting what sprinkler standard is best for the building, the next step is to determine whether a dry pipe system, wet pipe system or pre-action sprinkler system is needed for the building. In most buildings, the wet pipe system is used where the pipes are constantly filled with water at all times.
However, some structures such as parking garages require a dry pipe system to curb water freezing. In such pipes, a pressurized gas holds shut a dry valve which stops the water in an insulated section of the pipe until the water is required. When the sprinkler heads are activated, the gas depressurizes, thereby opening the dry valve and allowing water flow.
A pre-action system functions similar to the dry valve type, but is used where any accidental discharge would be severe. A pre-action valve, functioning as a dry valve, holds back the water, while a separate trigger activates the sprinkler heads in the event of a fire outbreak.
5. Determing the amount of water required
The amount of water needed to control a fire depends on various factors such as the kind of fire and the size of the fire. There are calculations which help sprinkler designers develop systems with sufficient water pressure and flow, including occupancy hazard, design area and density/curve area.
Need to speak with a professional for your building project? Contact us! At JPC Design Consortium, we have a line of design professionals ready to help you actualize your building ideas.