A fire sprinkler is the part of a fire sprinkler system that discharges water when the effects of a fire have been detected, such as when a predetermined temperature has been exceeded.
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In 1812, British inventor Sir William Congreve patented a manual sprinkler system using perforated pipes along the ceiling. When someone noticed a fire, a valve outside the building could be opened to send water through the pipes.
Henry S. Parmalee of New Haven, CT created and installed the first automatic fire sprinkler system in 1874, using solder that melted in a fire to plug holes in the otherwise open water pipes. At the time he was the president of Mathusek Piano Works. Parmelee invented his sprinkler system in response to exorbitantly high insurance rates. Parmelee patented his idea and had great success with it in the U.S. Parmelee called his invention the "automatic fire extinguisher". He then traveled to Europe to demonstrate his method to stop a building fire before total destruction.
His invention did not get as much attention as he had planned. Most people could not afford to install a sprinkler system. Once Parmelee realized this, he turned his efforts on educating the insurance companies about his system. He talked about how the sprinkler system would reduce the loss ratio, thus saving money for the insurance companies. He knew that he could never succeed in obtaining contracts from the business owners to install his system unless he could ensure for them a reasonable return in the form of reduced premiums.
In this connection he was fortunate enough to enlist the sympathies of two men, who both had connections in the insurance industry. The first of these was Major Hesketh, who, in addition to being a cotton spinner in a large business in Bolton, was Chairman of the Bolton Cotton Trades Mutual Insurance Company. The Directors of this Company and more particularly its Secretary, the late Peter Kevan, took an interest in Parmelee’s early experiments, and eventually it was to Major Hesketh, its Chairman, that Parmelee owed his first order for the Sprinkler Installations which were installed in the Cotton Spinning Mills of John Stones & Company, at Astley Bridge, Bolton, to be followed soon afterwards by the Alexandra Mills belonging to Mr. John Butler of the same town.
Although he got a contract through his efforts, the Bolton Cotton Trades Mutual Insurance Company was not a very big company outside of its local area. Parmelee needed a wider influence. He found this influence in James North Lane, the Manager of the Mutual Fire Insurance Corporation of Manchester. This company was founded in 1870 by the Textile Manufacturers' Associations of Lancashire and Yorkshire as a protest against high insurance rates. They had a policy of encouraging risk management and more particularly the use of the most up-to-date and scientific apparatus for extinguishing fires. Even though he put tremendous effort and time into educating the masses on his sprinkler system, by 1883 only about 10 factories were protected by the Parmelee sprinkler.
Back in the US, Frederick Grinnell, who was manufacturing the Parmelee sprinkler, designed a newer and more effective version which became known as the Grinnell sprinkler. He increased sensitivity by removing the fusible joint from all contact with the water, and, by seating a valve in the center of a flexible diaphragm, he relieved the low-fusing soldered joint of the strain of water pressure. By this means the valve seat was forced against the valve by the water pressure, producing a self-closing action, so that the greater the water pressure, the tighter the valve. The flexible diaphragm had a further and most important function. It caused the valve and its seat to move outwards simultaneously until the solder joint was completely severed. Grinnell got a patent for his version of the sprinkler system. He also took his invention to Europe, where it was a much bigger success than the Parmelee version. Eventually, the Parmelee system was withdrawn, which left an open path for Grinnell and his invention.
Fire sprinkler application and installation guidelines, and overall fire sprinkler system design guidelines, are provided by the National Fire Protection Association (NFPA) 13, (NFPA) 13D, and (NFPA) 13R.
The states,California and Pennsylvania require sprinklers in at least some new residential construction. [1]
Fire sprinklers can be automatic or open orifice. Automatic fire sprinklers operate at a predetermined temperature, utilizing a fusible element, a portion of which melts, or a frangible glass bulb containing liquid which breaks, allowing the plug in the orifice to be pushed out of the orifice by the water pressure in the fire sprinkler piping, resulting in water flow from the orifice. The water stream impacts a deflector, which produces a specific spray pattern designed in support of the goals of the sprinkler type (i.e., control or suppression). Modern sprinkler heads are designed to direct spray downwards. Spray nozzles are available to provide spray in various directions and patterns. The majority of automatic fire sprinklers operate individually in a fire. Contrary to motion picture representation, the entire sprinkler system does not activate, unless the system is a special deluge type.
Open orifice sprinklers are only used in water spray systems or deluge sprinklers systems. They are identical to the automatic sprinkler on which they are based, with the heat sensitive operating element removed.
Automatic fire sprinklers utilizing frangible bulbs follow a standardized color coding convention indicating their operating temperature. Activation temperatures correspond to the type of hazard against which the sprinkler system protects. Residential occupancies are provided with a special type of fast response sprinkler with the unique goal of life safety.
Each closed-head sprinkler is held closed by either a heat-sensitive glass bulb (see below) or a two-part metal link held together with fusible alloy such as Wood's metal[2] and other alloys with similar compositions.[3] The glass bulb or link applies pressure to a pip cap which acts as a plug which prevents water from flowing until the ambient temperature around the sprinkler reaches the design activation temperature of the individual sprinkler. Because each sprinkler activates independently when the predetermined heat level is reached, the number of sprinklers that operate is limited to only those near the fire, thereby maximizing the available water pressure over the point of fire origin.
The bulb breaks as a result of the thermal expansion of the liquid inside the bulb.[4] The time it takes before a bulb breaks is dependent on the temperature. Below the design temperature, it does not break, and above the design temperature, it takes less time for higher temperatures. The response time is expressed as a response time index (RTI), which typically has values between 35 and 250 m½s½, where a low value indicates a fast response.[5] Under standard testing procedures (135 °C air at a velocity of 2.5 m/s), a 68 °C sprinkler bulb will break within 7 to 33 seconds, depending on the RTI.[6] The RTI can also be specified in imperial units, where 1 ft½s½ is equivalent to 0.55 m½s½. The sensitivity of a sprinkler can be negatively affected if the thermal element has been painted.
| Maximum Ceiling Temperature | Temperature Rating | Temperature Classification | Color Code (with Fusible Link) | Glass Bulb Color |
|---|---|---|---|---|
| 100°F / 38°C | 135-170°F / 57-77°C | Ordinary | Uncolored or Black | Orange (135°F) or Red (155°F) |
| 150°F / 66°C | 175-225°F / 79-107°C | Intermediate | White | Yellow (175°F) or Green (200°F) |
| 225°F / 107°C | 250-300°F / 121-149°C | High | Blue | Blue |
| 300°F / 149°C | 325-375°F / 163-191°C | Extra High | Red | Purple |
| 375°F / 191°C | 400-475°F / 204-246°C | Very Extra High | Green | Black |
| 475°F / 246°C | 500-575°F / 260-302°C | Ultra High | Orange | Black |
| 625°F / 329°C | 650°F / 343°C | Ultra High | Orange | Black |
From Table 6.2.5.1 NFPA13 2007 Edition indicates the maximum ceiling temperature, nominal operating temperature of the sprinkler, color of the bulb or link and the temperature classification.
ESFR, or ESFR Sprinkler, denotes a special type of fire sprinkler. Early Supression Fast Response sprinkler heads were developed in the 1990s to take advantage of the latest fast-response fire sprinkler technology to provide fire suppression of specific high-challenge fire hazards. The sprinklers are specifically designed to fully suppress a fire that is within the design limits of the piping system. Prior to the introduction of these sprinklers, protection systems were designed to control fires until the arrival of the fire department.
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