In the past fifteen years the variety of sprinklers available has grown tremendously.
Years ago an engineer would simply specify an upright, pendent or sidewall sprinkler, a sprinkler temperature classification and thread and outlet size. Today, sprinkler specification is a much more difficult task. Characteristics such as the Response Time Index, water spray pattern, (Fig. 14.18) operating component type and appearance
must be addressed. While there have been numerous advances in sprinkler technology, sprinklers still work in the same manner as they did 100 years ago. Sprinklers are heat sensitive devices, which open to flow water at a preset temperature.
More specifically, a sprinkler operating component releases at a specified temperature. Upon release of the operating component, the sprinkler plug falls from the sprinkler orifice and water flows through the orifice, hitting the sprinkler deflector and spraying into a predetermined spray pattern and onto the fuel below.
Of sprinkler components the most interesting is the operating component (see Fig. 14.14). There are two basic types of operating components, the fusible-style operating component, which is a soldered type element that melts when subjected to sufficient heat, and the glass bulb operating components, which is an oil containing glass bulb that become pressurized and fails under sufficient heat. For either type of sprinkler operating component, sufficient heat must be provided over a sufficient period of time to cause the solder to melt or bulb to fail. Neither the fusible or glass bulb operating component are better than the other; however, specification of a quick response operating component, available in either fusible or glass bulb style, will result in faster operating times than a standard response operating component. This is a result of the low mass to surface area ratio of the quick response operating component as opposed to that of a standard response operating component. In offices and other light hazard applications quick response sprinklers have proven superior to standard response sprinklers. As a result, it is a current code requirement that all light hazard occupancies be protected with quick response sprinklers.
