Dry sprinkler heads are designed for use in environments where freezing temperatures could damage or disable a standard wet pipe sprinkler system. They function by keeping water away from the cold area until a fire is detected.
Here's a breakdown of how they work:
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Sealed Barrel: A dry sprinkler head includes a length of pipe, often called the barrel, that extends from the heated area of the fire protection system into the cold area where the sprinkler head is located. This barrel is normally filled with pressurized air or nitrogen.
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Water Seal: The water supply is held back from the barrel by a valve located in a heated area of the building, often within the branch line itself, or at a remote location (e.g., dry valve).
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Heat Activation: When a fire occurs, the heat-sensitive element (typically a fusible link or glass bulb) in the sprinkler head activates.
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Air/Nitrogen Release: The activation of the heat-sensitive element causes the release of the pressurized air or nitrogen from the barrel.
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Valve Opening: The loss of air pressure in the barrel causes the valve holding back the water supply to open. This valve can be mechanically connected to the barrel, or can be a remote dry valve.
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Water Flow: Water then flows through the barrel and out of the sprinkler head orifice.
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Deflector Action: The water impacts the deflector, which is designed to distribute the water in a specific pattern to suppress the fire.
In essence, dry sprinkler heads act as remotely operated valves, triggered by heat and pressure release, that allow water to flow only when needed. This design prevents water from freezing in the pipes and rendering the sprinkler system ineffective.
