A Deluge System is a fixed fire protection system in which the pipe system is empty until the deluge valve operates to distribute pressurised water from open nozzles or sprinklers. Deluge systems are more complex than wet pipe and dry systems because they contain more components and equipment. The deluge valve is activated by a fire detection system installed in the same area as the sprinklers. Engineers may use various detection systems, including smoke, heat, ultraviolet (UV), or infrared (IR) detection. The Deluge system can be activated by a hydraulic, pneumatic, electric, or manual release system or any combination of these release systems. But, in all cases, the deluge valve itself is activated hydraulically. When the detection device is activated, the deluge valve is tripped, and water flows into the piping system, discharging through all spray nozzles or sprinklers simultaneously.
Deluge systems are used where occupancy or special hazards require the quick application of large quantities of water. These systems are used to create a buffer zone in high-hazard areas or areas where fire may spread rapidly. Engineers can also use them to cool surfaces to prevent deformation or structural collapse or protect tanks, process lines, or transformers against explosion. Other examples include storage or process areas containing a low flash point, tanks containing combustible solutions, equipment pits or product handling systems. When designing a deluge system, efforts should be made to acquire specific information regarding the hazard to be protected.
Foam-water deluge systems are those using foam-water sprinklers or spray nozzles and an air-foam concentrate introduced into the water at a controlled rate on the system side of the deluge valve. Foam water systems are used to control and extinguish fires that require a smothering and cooling agent. Examples are extraction plants, aircraft hangars and areas where flammable-liquid spill fires may occur.
Some installation standards state that discharge rate should not exceed a discharge rate of 3,000 GPM (11,355 L/min) for a single system. System size may be further limited by the water supply available to the system and/or the hazard classification. If there is any question concerning the adequacy of the deluge system’s coverage, seek the insurance underwriter's advice or a qualified consulting engineering firm.
System Requirements
Section 7.3 of NFPA 13-2007 provides the installation rules and characteristics unique to deluge systems. Also, refer to NFPA 72 National Fire Alarm Code for specific requirements on the design of hydraulic, pneumatic, and electrical detection systems.
Deluge systems are required to be hydraulically calculated. Since all sprinklers are open, every sprinkler on the system discharges water simultaneously when the deluge valve operates. Note: The system’s operation area is easy to determine; it is the entire area protected by the deluge system. Chapter 22 of NFPA 13 discusses the procedures for calculating the hydraulic demand of the sprinkler system and verifying whether the available water supply will meet the requirements.
Releasing Devices
Deluge equipment is designed to allow for a variety of release devices. The release system detection device itself may be thermostatic (fixed-temperature/rate-of-temperature-rise) or manual. Releasing devices, including automatic sprinklers used as releasing devices, are listed with specific spacing requirements that Engineers and Designers must follow. Where thermal activation is utilised, the release system's activation temperature shall be lower than the sprinkler's activation temperature to ensure that the releasing system will operate before the sprinkler system. NOTE: Where heat-responsive devices are used, NFPA 13 requires a supply of spare fusible elements (at least 2 of each temperature rating) to be kept on the premises for replacement purposes.
The release system shall serve all areas that the deluge system protects to ensure that the release system will activate and provide water to the system and the affected area in the event of a fire. NFPA 13 requires the detection devices or systems to be automatically supervised (monitored).
Device Compatibility
All components of pneumatic, hydraulic, or electrical systems shall be compatible to ensure that all system components function as an integrated unit. For example, in electrical systems, the solenoid valve must be listed with the deluge valve and the fire detection system, including the control panel. Correct coordination of the detection devices, releasing equipment, and the control panel is imperative for the system's prompt and reliable operation.
Manually-Operated Release System
Manually operated release systems are usually integrated into one of the other types of release systems. NFPA 13 requires the manual release device to be a stand-alone arrangement to ensure operation, regardless of the associated detection system's potential failure. Usually, a system will incorporate a manual release at the valve, exits, operator station, or other convenient locations to operate the system during a fire emergency.
Release Control Panel
The release panel is an essential component for system operation and is required to be listed.
Devices for Test Purposes and Testing Apparatus
Where detection devices installed in circuits are located were not readily accessible for testing, NFPA 13 requires an additional detection device to be provided on each circuit for test purposes at an accessible location. Engineers shall connect the device to the circuit to ensure a proper test of the circuit.
A means of producing the heat or impulse used to operate the detection device shall be available at the location. Where explosive vapours or materials are present, Engineers shall use hot water, steam, or other testing methods not involving an ignition source.
Water Control Valves
The automatic water control valve must be provided with hydraulic, pneumatic, or mechanical manual means for an independent operation of detection devices and sprinklers.
Valve Rooms and Protection Against Freezing
Because the deluge valve is hydraulically operated, Engineers must protect system water control valves and supply pipes against freezing. A heated enclosure may be required. NFPA 13 requires valve rooms to be lighted and heated with a permanent heat source, such as a baseboard or unit heater.
Note: Heat tape is not permitted to be used instead of heated valve enclosures to protect deluge valves and supply pipe against freezing.
Pressure Gauges
NFPA 13 requires listed pressure gauges to be installed below the deluge valve and on the air supply to deluge valves. Refer to NFPA 13 section 8.17.3 for additional information on gauges.
Water Supply
Since deluge systems are hydraulically-calculated, Engineers should obtain the water supply's static and residual water-pressure characteristics by conducting an on-site water-flow test. Prior water-supply data may already be available from the following sources: job specifications, consulting engineer, architect, insurance underwriter, owner, or local water department. Preliminary data must be applicable and may need to be verified. If a fire pump is required, acquire a pump supply curve from the pump manufacturer. However, be sure to check with authorities having jurisdiction (approving body) regarding pump characteristics (percentage over rated capacity at a percentage of rated PSI).
Drainage
A deluge system may produce a large volume of water. Engineers should notify the owner as early as possible concerning the total volume of water expected to ensure proper drainage and, where necessary, collection.
Floatable Combustible Liquids
Suppose the area being protected contains a large volume of a floatable combustible liquid. In that case, Engineers should install a safe drainage or diking system to prevent the possibility of transferring the fire to adjacent areas.
Equipment Shut-Down
Because a deluge system applies water to the total system areas simultaneously, it may be advisable to install equipment that will automatically shut down selected production equipment. Examples of equipment that the system might automatically shut down during deluge system operation are:
Equipment is prone to more severe water damage when “ON” than “OFF”.
Pumps, pipelines, and conveyors supply combustible solids, liquids, or gases to the system area.
Equipment would present a serious electrical hazard if exposed to water (e.g. transformers, generators, conveyors, high-capacity battery chargers, high-amperage motors, etc.)
If the drafting they create, large-volume air handling systems would serve to spread the fire to adjacent areas.
Corrosive Atmospheres
Request information from the owner or owner’s representative regarding the system’s environment. Corrosive elements may be present in the system’s area, requiring unique material or protective coating for all deluge system components. Note: For outside exposed piping or where corrosive atmospheres exist, use steel/galvanised pipe and steel malleable or ductile iron fittings or copper.
Draft Curtains
Draft curtains may be required to separate each deluge system when multiple systems serve a common roofed area. The draft curtains suppress the operation of any system adjacent to the system serving the fire area. Proper placement of draft curtains will prevent the unnecessary use of water otherwise needed to fight the fire.
Explosion-Proof Electrical Equipment
If the system protects areas where explosive vapours may be present, explosion-proof electrical equipment is required. Check with the owner or other authorities regarding ratings.
Flow Control Valve Substitution for Deluge Valve.
The Flow Control Valve may be used for some deluge applications. This valve offers the same operating features as a deluge valve. Besides, it provides ON-OFF remote control.
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