Rome, 64 A. D. Emperor Nero watched in horror as the great city of Rome burned for six days and seven nights. Afterwards 70% of the city was left in smoldering ruins and devastation. (The Burning of Rome, 64 AD 1) Why the exact cause of the fire is unknown, we wonder if an effective sprinkler system could have prevented this incident and others like it. A city that was well known for their magnificent construction, architecture, and irrigation systems was almost completely destroyed by one incident. Many codes do not require a specific type of Automatic Sprinkler System.
While the most common type found is the Wet Pipe System; Dry Pipe, Preaction, and Deluge Systems can be found in many different occupancy types. The two main purposes of automatic sprinkler systems are to extinguish fires and control the fire until appropriate personnel arrive to extinguish the fire. Automatic sprinkler systems are expected in all occupancy types, except residential, unless the hazard is not compatible with water. For these hazards there are several other types of suppression systems that can be installed to manage the incident. By installing an automatic sprinkler system, you increase life safety and property protection.
What is the standard of sprinkler systems? The goal is to increase life safety and decrease property damage. The National Fire Protection Association (NFPA) has been the leader in mandating standards and requirements when it comes to sprinkler systems. They have developed many standards that address the installation, inspection, and maintenance of sprinklers. Wet pipe systems are closed water systems attached to a piping system containing pressurized water at all times. This type of automatic sprinkler system is the most common type, and can be found in all most all occupancy types.
Unless the potential of freezing pipes or other special conditions apply, this type of system will be encountered most frequently. The operation of this sprinkler system is very simple. The wet-pipe system consists of sprinkler heads attached to sprinkler supply lines that interlace the occupancy. When a fire first starts there is minimum heat generated. As the fire grows and the thermal layer is disturbed, heat rises to the targeted sprinkler heads. Depending on the rated temperature of the sprinkler head, a fusible disc or link melts from the heat and initiates the flow of water.
While most fires are controlled by one or two sprinkler heads, in the case of fast moving fires more may be needed to control the fire. When water is flowed from the system, typically other things may happen. In all most all wet-pipe systems, there is some type of audible alarm activated at the standpipe. This will trigger other alarms in the building, and most of the time notifies an agency that will then notify the Fire Department of a water flow alarm or others like it. Dry pipe systems use air or nitrogen to keep the supply line pressurized at all times.
This type of automatic sprinkler system is commonly found in the colder areas where the possibilities of freezing pipes are encountered. Dry-pipe systems provide the same adequate protection similar to wet-pipe systems. The piping is charged with air or nitrogen, and when a sprinkler head is activated the drop in the pressure opens a valve at the standpipe that allows water to flow into the systems. (Bahme 25) Just like the wet-pipe system, normally one or two sprinkler heads are needed to control the fire. There will also be an alarm that is activated notifying the appropriate agency to contact the Fire Department.
At lest once a week the system should be tested to make sure that the air pressure within the piping is maintained. The third type of automatic sprinkler system is the Pre-action System. This type of system is a closed piping system that contains air, which may or may not be under pressure. When a fire occurs the fire detecting device signals the control valve to open charging the system. This type of system is usually used where the possibility of broken pipes and sprinkler heads may result. The most common places found include electrical rooms, computer rooms, and other areas that may house expensive equipment.
There can be several types of pre-action system including a recycling system. This system is capable of charging the piping, discharging water, then cutting itself off. In the event that the fire rekindles, it can discharge again. It then has the ability to recycle the water. Deluge systems are much like Pre-action systems except that the sprinkler heads are open and the system is not charged. Similar to that of the pre-action systems, a fire detection device, usually a heat sensor, activates the discharge valve on the system.
The difference is that the entire sprinkler component of the system is open; therefore the area that is activated is deluged in water. These types of automatic sprinkler system can be found where a high hazard of flammable liquid may be encountered. The most common place is aircraft hangars. Caution should be taken though; in confined spaces the oxygen level can be deficient when these systems are activated due to the copious amounts of water. Combined Dry-Pipe and Pre-action systems are composed of both the systems mentioned above.
These systems have the dry pipe features with the pre-action features in the event the dry pipe portion fails. These systems are used when an area is too large to be covered by a dry pipe system. On the same note though, combined systems were originally developed for protection during cold climates. Long lines would be subject to freezing. These systems are commonly found when dealing with long piers. (Bahme 30) It is important to note this type of system is considered two independent systems. Testing requires individual standards for both type; consisting of the dry pipe system and the pre-action system.
Limited water supply systems are those where supply water cannot be properly supplied to the occupancy. These systems consist of many wide range types and can be used as outside sprinklers and confined space sprinklers. Some research obtained shows that one type of limited water sprinkler type could be the antifreeze sprinkler system. This type of system is very uncommon and is normally not accepted and used in recent automatic sprinkler systems. In conclusion, there are several types of water sprinklers used in today’s management to help increase life safety and decrease property damage.
By including detection devices and the correct sprinkler heads, these systems can mean the difference between life and death. The occupancy should have the correct automatic sprinkler system that will properly suppress the material relevant in that occupancy regardless of the type. The preferred automatic sprinkler system should all be able to notify the occupants, summon the correct agency to suppress the fire, sound alarms, supervise fire control, and initiated a wide variety of auxiliary functions involving environmental, utility, and process controls. (IFSTA 559)