Fire sprinkler systems were invented over 120 years ago since then several 100 million sprinkler heads have been installed throughout the world. Since that time sprinklers have effectively protected thousands of buildings and properties, helped to protect the financial collapse of several businesses, saved countless lives, prevented numerous burn injuries, and protected the environment from catastrophic fire-related pollution. In India, the fire and rescue department which comes under the state government is primarily responsible for fire protection engineering and fire prevention.
The rules for fire protection and fire prevention were made in the form of state fire safety regulations or Municipal By-Laws and the National Building Code. In our country, the Bureau of Indian Standards published the National Building Code or NBC. Fire sprinklers are designed to cope with a fire risk presented by each individual building and may also be specifically configured to save lives. As we all know water is the most effective firefighting medium available. Sprinklers will distribute water right into the origin of fire during its early stages through a specially fabricated sprinkler head. Sprinkler heads are designed to get activated at various temperatures to suit various applications.
Sprinklers will explode when it’s rated temperature is reached due to fire, once it is activated it will discharge water and operate a local fire alarm. It can also operate a remote alarm to the emergency rescue team and the fire and rescue department. A typical sprinkler head consists of a threaded body to connect to pipework, with a valve seal to hold back the water. The valve seal is occupied by a glass bulb that contains a glass bulb filled with a glycerin-based liquid that has a high coefficient of expansion. A small measured volume of vapor remains trapped when the bulb is completely sealed.
When the liquid enlarges under the effect of heat from a fire, pressure in the bulb rises until the vapor is compressed. The further rise in temperature creates a rapid buildup of pressure sufficient to shatter the bulb and release the valve seal and allow the water to flow onto a water distribution deflector. This results in an even distribution of water droplets in a pre-arranged pattern over the fire. Operating temperatures of a variety of sprinkler’s heads are identified by the color of the bulb. A very large array of sprinkler heads are available to the specifiers.
Each type of head is designed to cope up with different fire risks, different operating temperatures, and different operational requirements. The fire risks are commonly described as a light hazard, ordinary hazard, or extra-high hazard. With a deflector attached to spray a proportion of the water discharged onto the surface of the ceiling, conventional sprinklers can be installed in either the upright or pendant position. For certain instances where all the water needs to be discharged downwards, spray sprinklers in upright or pendant positions are used.
Sidewall sprinklers are generally used to keep ceilings clear of pipework or to avoid having to disorder the existing ceilings while installing. In light hazards, each sprinkler protects up to 17 square meters of fire risks and protect up to nine square meters of fire risks during ordinary hazards. Sidewall sprinklers are specifically designed to give an extended coverage of water distribution with one sprinkler able to safeguard an area up to 21 square meters. Sprinklers must have a quick response bulb, to perform effectively.
In fire hazard circumstances, few deaths result from direct contact with fire flames. The serious threat comes from the inhalation of the products of burning such as carbon monoxide, hydrogen cyanide, hydrogen chloride, or other toxic gases and the related heat. The rapid reaction time of quick response sprinklers reduces the life-threatening levels of toxic gases and temperatures. Quick response sprinklers provide more time for the people to evacuate from the fire risk areas in environments where there are people who cannot escape without assistance such as in hospitals or homes. A sprinkler head is connected to a water supply, all over the buildings via a network of pipes. The area protected by each sprinkler head can vary from nine square meters to 21 square meters depending on the fire risks.
The pipework is specially designed to ensure the correct flow and pressure of water which is maintained at each sprinkler head. The water supply to the system can be fed from the water supply provided by the state water authority. For light to medium fire risks such as residential, offices, hotels, and light manufacturing and commercial occupancies a pumped supply from a water storage tank or reservoir is normally necessary for high fire risk areas such as heavy manufacturing and warehouse storage. The international design requirements are specified in the British standard BS v 306 part 2 and LPC FM or NFPA design rules. The flow of water to the sprinkler heads is automatically delivered by a control and alarm valves.
There are mainly five types of sprinkler systems.
- Wet pipe systems
- Dry pipe systems
- Deluge systems
- Pre-action systems
- Foam water systems
All these types of sprinkler systems require different valve arrangements. A wet system usually protects places where the temperature does not fall below the freezing point. Because it helps to permanently charge water inside the pipe. On the other hand, a dry system is installed, where the pipework is charged with compressed air if static water is not available.
Both the wet and dry system as the name suggests allows the system pipework is allowed to charge with water in summer and with air in winter when there is a risk that the room temperature can fall below freezing point. The pre-action system includes a standard sprinkler system and an independent electrical system of heat or smoke detectors installed in the same areas as of the sprinklers. The main control panel automatically opens the control valve when the signals received into the detectors and allowing water to flow into the sprinkler pipework. When the individual sprinkler heads reach their operating temperature, the water is released automatically.
Any physical damage caused to a sprinkler in a non-fire situation will not result in water discharge but will cause both visual and audible alarms to be raised at the main control panel. A deluge system, unlike any other typical sprinkler system, is designed exactly for high hazard applications with fast fire growth potential. The deluge valve is operated by a separate detection system responding to a fire. Throughout the protected area this system brings a large number of open sprinklers into action simultaneously.
The reason sprinklers are so effective is because it set OFF the fire before it has time to grow and spread without any excessive use of water. Most of the major countries have rescued from fire hazards by using fire sprinklers to good effect. The fire sprinklers are unique, not only detect a fire and raise an alarm but also operate to control and extinguish the fire in many cases before the arrival of the fire brigade.
Only the sprinkler heads closest to the fire operate, water is discharged by a sprinkler directly on to a fire at a rate of a minimum of 60 liters per minute. Sprinklers are economical to install and have a lifespan of at least 25 years.
The fire threat will never change, it will always be with us threatening life, property, and the environment we live in. Fire sprinklers can protect us and future generations from fire hazards and it’s after-effects.