Water Mist Systems Chapter 6

Objectives Evaluate water mist as a potential halon replacement Discuss the applications for water mist systems Compare the performance objectives of a water mist spray to the spray of a large-drop sprinkler

Objectives (con’t.) List water mist system types and configurations Discuss the reasons why zoning of water mist systems can increase system effectiveness for systems with limited water supplies

Water Mist Performance Objectives Fire control: a reduction in thermal exposure, threat to occupants, or fire-related characteristics Fire suppression: a sharp reduction in heat release rate and prevention of regrowth Fire extinguishment: complete suppression of the fire

Water Mist Droplets Water mist: spray with water droplets of less than 1000 microns at the minimum operation pressure of the discharge nozzle Droplet Size Performance Objectives Water Mist Pressure and Droplet Size –Low-pressure water mist systems –Intermediate-pressure water mist systems –High-pressure water mist systems

Water Mist Droplets (con’t.) Figure 6-1 Droplet size

Water Mist System Design Local application method: agent is applied directly onto the hazard Total flooding method: completely filling a room or enclosure volume with a fire protection agent

Water Mist System Design (con’t.) Figure 6-11 Water mist system configuration

Water Mist System Design (con’t.) Zoned application systems: volume is protected by several distinct suppression zones, each with its own detection system Types of Water Mist System –Deluge water mist systems –Wet pipe water mist systems –Preaction water mist systems –Dry pipe water mist systems Water Mist System Calculation Criteria (see Table 6-1, Page 202)

Water Mist Applications Potential uses for water mist technology are diverse Electronic/Telecommunications Applications Gas Turbine Applications Gas-Well Blowout Applications Exposure Protection Applications Life Safety Applications

Automatic Sprinkler Systems as a Halon Replacement Standard automatic sprinkler system being considered as a replacement for a halon system Present no personnel safety concerns No effect on the ozone layer The only concern is relative to property damage in cases where electronic devices or irreplaceable objects are protected

Ultra High-speed Explosion Suppression Systems and Ultra High-speed Water Spray Systems Chapter 7

Detonations and Deflagrations Detonation: a reaction in which the flame front expands at a rate greater than the speed of sound Deflagration: a reaction in which the flame front moves into the unburned material at less than the speed of sound

Design Approaches Point protection: application of suppressant directly onto an expected point of hazard Area protection: application of suppressant over the entire floor surface area of a room or enclosure

Explosion Suppression Systems First explosion suppression systems were introduced by the British in the late 1940s to protect aircraft engines and extended to industrial use in the early 1950s Cylinder filled with a suppressing agent, a detection system, and a system of control circuitry Designed to protect enclosed vessels or containers in which over pressurization is the primary concern

Explosion Suppression Systems (con’t.) Detection Systems for Explosion Suppression Systems Fire Alarm Control Units (FACU) for Explosion Suppression Systems Applications for Explosion Suppression Systems –Aerosol Fill Rooms –Diptanks

Explosion Suppression Systems (con’t.) Applications for Explosion Suppression Systems (con’t.) –Dust Collectors –Grain Elevators –Other Dust Hazards –Vaporous Hazards –Industrial Processes –Other Hazards