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Fire Sprinkler – Design Features

The current design of a Fire Sprinkler has evolved over many years, using historical data and studying their effectiveness on real fires in all types of construction, occupancies and hazards. Using today’s advanced technology the design parameters have been refined and specialized and include the expected scope of protection, operation and suppression intended by using computerized fire models and full scale testing.

A Fire Sprinkler is manufactured and “listed” as a single device and consists of four major components. None of these components can be altered, removed and/or interchanged with components from other sprinklers, or devices:

Link and Lever/ Solder Type
Liquid filled Bulb Type
  • The deflector helps direct the flow of water from the sprinkler when activated. It shapes the spray pattern and even helps define the size of water droplets based on the volume and pressure of water being discharged.
  • The element, or link is the “trigger mechanism” that releases and insures removal of the plug, or plate, to open the waterflow path completely upon activation. Today’s Fire Sprinklers use either a a glass bulb filled with a liquid that expands when heated and breaks the bulb, or a metal link and lever that is usually soldered in a manner that when heated to a specific temperature will melt and open the “link”.
  • The plug, or plate, or seal which covers the opening, or orifice located in the frame, or body of the Sprinkler. It prevents water from being discharged at that location until removed and it is held in place by the element, or link. Activation of the “trigger” removes the element, or link and plate which allows internal system pressure to fully open the waterflow path.
  • The frame, or body holds all the components together AND controls the amount of waterflow through it’s orifice. By using the mathematical formula of flow through an orifice, the volume of waterflow can be determined by the K-factor of the sprinkler (which is assigned by the manufacturer and based on the size of the orifice) and the internal system pressure at that point. Quantity (flow) equals K-factor times the square root of the Pressure. When the frame is threaded for connection to pipe distribution system, those threads are National Pipe Threads NPT.

Generally, Fire Sprinklers are also individually designed and configured to be used in several positions, or orientations, to accommodate various construction and building features. There are basically three standard sprinkler orientations that are widely manufactured and listed for each of the following orientations. Note that specific installation rules have been developed for each orientation. See NFPA 13.

Upright – In general, the sprinkler is orientated vertically on the top of the piping.

Pendent – In general, the sprinkler is orientated vertically on the bottom of the piping.

Sidewall – In general, the sprinkler is orientated horizontally on the side of the piping. Although there is also a “Vertical Sidewall” where the sprinkler is oriented vertically on top of the piping, but the deflector has been designed to direct the water in one horizontal direction…

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