Sprinkler Heads

The sprinkler head keeps the water in the system by a plug or cap held tightly against the orifice (opening) by levers or other restraining devices. The levers are held in place by the arms of the sprinkler body. In the past, the restraining device was usually a fusible metal link that melted at a predetermined temperature. More recently, a glass bulb with colored liquid and an air bubble is used. Heat expands the liquid, which compresses the air bubble until it is absorbed. Expansion continues with rising temperature until the bulb bursts at a predetermined temperature and releases water in a solid stream through the orifice.

The deflector on the sprinkler head converts the solid stream to a spray. It is more efficient to direct the spray down and horizontally rather than up, for better water distribution near the head and more effective coverage below.

Sprinkler head types include upright heads that sit on top of exposed supply piping (Fig. 45-3), and pendant heads that hang below the piping (Fig. 45-4). Side-wall sprinklers (Fig. 45-5) are usually located adjacent to one wall of smaller rooms, as in hotels or apartments, and throw a spray of water across the room, allowing

Sprinkler Pendant

an entire small room to be covered by one sprinkler head.

Pendant heads may be recessed, with part of the sprinkler body concealed above suspended ceilings and the deflector below the ceiling. Flush heads have only the heat-detecting element below the ceiling. Concealed heads are entirely above the ceiling, with a cover plate that falls away in a fire. Sprinkler head finishes are available in plain or polished brass, satin or polished chrome, stainless steel, and gold. The manufacturer may be able to coat ornamental pendants to match a desired decor, but sprinkler heads are never permitted to be field coated.

The air around a standard sprinkler may reach around 538°C (1000°F) before the standard 175°F-rated sprinkler opens, causing a lag time. Quick-response sprinkler heads are now required throughout light hazard occupancies, including office buildings, motels, and

hotels. They are more thermally sensitive and open sooner than older styles, and are able to fight a fire with fewer open heads, causing less water damage. The quick-response sprinklers track air temperature rise. The earlier operation is considered to offer superior life protection. They may, however, open for extraordinary heat that is not fire related.

Early suppression fast-response (ESFR) sprinklers are used for specific challenging fire hazards, for example where storage is piled high. The sprinkler's higher pressure and flow penetrate the fire's base faster. Quick-response, early suppression (QRES) sprinklers are similar to ESFR sprinklers, but with a smaller orifice for light-hazard occupancies. They are expected to be available soon for business, retail, public assembly, and educational applications.

Extended coverage sprinklers are used for unobstructed construction with flat smooth ceilings and no projecting lighting fixtures or grilles. Extra-large orifice sprinkler heads emit large quantities of water where water pressures are low. Multilevel sprinklers use sprinklers at lower levels in a space that has other sprinklers at a higher level. Normally, the lower sprinklers would be inhibited by the action of the higher sprinklers. Flow control sprinklers close automatically when ceiling temperatures are reduced, saving water and damage. A new development is a single head that may provide multiple types of sprays. Larger droplets penetrate the fire while a finer spray cools ceilings.

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