18 - Dry Sprinkler Systems - Introduction to Fire Alarms

Summary

This video explains how dry sprinkler systems work, particularly in environments where freezing temperatures are a concern. Unlike wet systems that keep pipes filled with water, dry systems use compressed air to prevent freezing. When a sprinkler head activates, air pressure drops, allowing water to flow through the system. The video also covers the critical monitoring components, such as air and water pressure switches, which are integrated with fire alarm systems to ensure proper system functionality. Additionally, it discusses system testing and maintenance requirements to ensure reliability during a fire emergency.

Takeaways

• 😀 Wet sprinkler systems have water always present in the pipes, waiting to extinguish a fire, but this can cause issues in environments that drop below freezing.
• 😀 Dry sprinkler systems are used in areas where pipes are exposed to freezing temperatures, preventing water in the pipes from freezing and causing damage.
• 😀 The dry system uses compressed air to pressurize the pipes and keep the valve shut until the system is activated by a fire.
• 😀 The Clapper in a dry valve seals the water side of the system and is held closed by the air pressure in the system.
• 😀 Water pressure is much higher than the air pressure in a dry system, which allows air to hold the Clapper shut and prevent water from entering the system until needed.
• 😀 If a sprinkler head bursts due to heat, the loss of air pressure allows water to flow into the system and extinguish the fire.
• 😀 Dry sprinkler systems are equipped with air and water pressure switches to monitor system status and ensure functionality.
• 😀 The air pressure switch monitors the air side of the system, triggering alarms if the air pressure falls below a set threshold, indicating potential problems such as compressor failure.
• 😀 The water pressure switch detects when water flows into the system and functions similarly to a water flow switch in wet systems, but it’s designed to handle the unique pressures of a dry system.
• 😀 Proper monitoring of both high and low air pressures is critical to prevent damage from over-pressurization or to detect issues before the system fails during a fire.
• 😀 Dry sprinkler systems require regular maintenance and monitoring to ensure air pressure remains within the required range and that the system is ready to activate when needed.

Q & A

What is a wet sprinkler system and how does it work?

A wet sprinkler system is a fire protection system where the sprinkler pipes are always filled with water, which sits right at each sprinkler head. When a fire occurs, the heat causes a sprinkler head to burst, releasing the water to extinguish the fire.

Why can't wet sprinkler systems be used in areas where temperatures drop below 32°F?

In areas where temperatures drop below freezing, the water in the sprinkler pipes can freeze, causing the pipes to burst. This would lead to a malfunction and a significant mess in the system.

What is a dry sprinkler system and how does it differ from a wet system?

A dry sprinkler system is designed for environments where the temperature could fall below freezing. Unlike wet systems, the pipes are filled with compressed air instead of water. The system remains dry until a sprinkler head is triggered by heat, releasing air and allowing water to flow through the pipes to extinguish the fire.

What role does the dry valve play in a dry sprinkler system?

The dry valve controls the flow of water in a dry system. It stays closed with compressed air pushing against a Clapper. When the system loses air pressure due to a triggered sprinkler, the Clapper opens, allowing water to flow into the pipes and extinguish the fire.

Why is compressed air used in dry sprinkler systems instead of water?

Compressed air is used to maintain the integrity of the pipes in environments where water would freeze. The air keeps the pipes pressurized and dry, preventing them from freezing, until the system is activated by a fire.

How does the pressure of compressed air in a dry system compare to water pressure?

The pressure of compressed air is typically much lower than the water pressure. Air pressure in a dry system can be as low as 40 PSI, while the water pressure can range from 60 to 100 PSI, depending on the system.

What happens when the air pressure in a dry sprinkler system drops?

If the air pressure drops (for example, if the compressor fails), the Clapper in the dry valve will no longer be held shut. This causes the valve to open and water will flow into the system to extinguish the fire.

Why is it important to monitor both air pressure and water pressure in a dry sprinkler system?

Monitoring both air and water pressure is crucial for ensuring the system's functionality. If air pressure drops too low, it signals a problem with the compressor or leaks. If water pressure is too high, it could lead to system damage or delays in the water being released during a fire.

What is the role of the air pressure switch in a dry sprinkler system?

The air pressure switch monitors the air pressure in the system. It has two settings: a high-pressure switch (typically set 10 PSI above the normal pressure) and a low-pressure switch (set 10 PSI below the normal pressure). If the air pressure falls below the set range, it alerts the fire alarm system to a potential issue.

How does the water pressure switch function in a dry sprinkler system?

The water pressure switch is activated when the Clapper in the dry valve opens, allowing water to flow through the pipes. It detects the water flow and sends a signal to the fire alarm system, similar to a water flow switch in a wet system, but it’s designed to withstand the high pressure of the water flow after the system is triggered.