Fire Sprinkler Head Components

The sprinkler is the spray nozzle which distributes water over a defined fire hazard area. Each sprinkler operates by actuation of its own temperature linkage. The typical sprinkler consists of a frame, thermal operated linkage, cap, orifice, and deflector. Styles of each component may vary but the basic principles of each remain the same. Click here to view sprinkler head styles.

  • Frame – The frame provides the main structural component which holds the sprinkler together. The water supply pipe connects to the sprinkler at the base of the frame. The frame holds the thermal linkage and cap in place, and supports the deflector during discharge. Frame styles include standard and low profile, flush, and concealed mount. Some frames are designed for extended spray coverage, beyond the range of normal sprinklers. Standard finishes include brass, chrome, black, and white. Custom finishes are available for aesthetically sensitive spaces. Special coatings are available for areas subject to high corrosive effect. Selection of a specific frame style is dependent on the size and type of area to be covered, anticipated hazard, visual impact features, and atmospheric conditions.
  • Thermal linkage – The thermal linkage is the component which controls water release. Under normal conditions the linkage holds the cap in place and prevents water flow, however, as the link is exposed to heat it weakens and releases the cap. Common linkage styles include soldered metal levers, frangible glass bulbs, and solder pellets. Each link style is equally dependable. Upon reaching the desired operating temperature, an approximate 30 second to 4 minute time lag will follow. This lag is the time required for linkage fatigue and is largely controlled by the link materials and mass. Standard responding sprinklers operate closer to the 3-4 minute mark while quick response (QR) sprinklers operate in significantly shorter periods. Selection of a sprinkler response characteristic is dependent upon the existing risk, acceptable loss level and desired response action.
  • Cap – The cap provides the water tight seal which is located over the sprinkler orifice. This component is held in place by the thermal linkage. Operation of the linkage causes the cap to fall from position and permit water flow. Caps are constructed solely of metal or a metal with a teflon disk.
  • Orifice – The machined opening at the base of the sprinkler frame is the orifice. It is from this opening which extinguishing water flows. Most orifice openings are 1/2 inch diameter with smaller bores available for residential applications and larger openings for higher hazards.
  • Deflector – The deflector is mounted on the frame opposite the orifice. The purpose of this component is to break up the water stream discharging from the orifice into a more efficient extinguishing pattern. Deflector styles determine how the sprinkler is mounted, by the angle of their tines. Common sprinkler mounting styles are upright (mounted above the pipe), pendent (mounted below the pipe, i.e. under ceilings), and sidewall sprinklers which discharge water in a lateral position from a wall. The sprinkler must be mounted as designed to ensure proper action. Selection of a particular style is often dependent upon physical building constraints.

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