WATER MIST SYSTEM

• A substantial reappraisal to fire protection problems evident over recent years.
• As a result of extensive research & development, KI group of companies remains at the forefront of new technology in fire safety, offering a range of state-of-the-art fire extinguishing systems.
• Among the most exciting advances & developments is the use of water, that most natural of substances, deployed as a highly efficient fine mist (spray).

• Water as a fire suppressant!
• Kidde single fluid nozzle - offers: (1) optimum droplet size distribution, (2) flow rates, and (3) spray coverage characteristics
• Countless trials at Silvani
• Markets for Kidde Product

• Fuel Cooling
  
  • Cooling of burning materials and potential fuel sources to below auto-ignition temperatures
  • Inhibition of fuel vaporization

• Flame Quenching
  
  • Reduce flame temperature to 1600 K at which combustion chain reactions cannot be sustained.
  • Increase heat capacity by 20-50%.

• Inerting
  
  • Inerting as a result of steam production, which excludes oxygen from the flame zone.
  • Dilute vapor-phase concentration of fuel & oxygen

Water as a Fire Suppressant

Problem & Solution Summary

• Its use in the past has been limited, by means of distribution, which utilize only a small fraction of its fire-fighting capability.
• Recognizing that the phenomena contributing to fire suppression are related to the surface area-to-volume ratio of the agent, the efficiency of water is optimized by delivery to the hazard zone as a fine spray.
• As well as achieving fire extinction bya combination of cooling & inerting processes, water offers the additional benefits of thermal radiation attenuation, smoke scrubbing, and the absorption of water-soluble toxic & irritant gases.
• Not a Chemical Agent like Halons
• Potentially, an Outstanding Physically-acting agent, owing to:
  • its high Heat Absorption Capability,
  • its latent heat of vaporization, having values of 4.2 J/g & 2442 J/g at room temperature.

• This heat sink capability can effect fire extinguishment (1) by cooling of burning materials to inhibit fuel vaporization
• This heat sink capability can effect fire extinguishment (2) by quenching of flame, where an increase in heat capacity of the fire gas atmosphere by 20-50% can reduce the flame temperature to around 1600 K, at which combustion reactions cannot be sustained.

• A further useful property of water:
  
  • 1700-fold increase in volume upon vaporization
  • This effect in the flame zone provides inerting, by diluting the gas-phase concentrations of fuel & oxygen

• Fuel / Flame Cooling
  
  • High heat capacity - High latent heat of vaporization
  • Inerting - 1700-fold expansion ongoing from liquid to gas Problem
  • Has exceptional thermodynamic (heat absorption) potential, but heat absorption & vaporization processes are relatively slow.
  • Often achieves only a small fraction of its full thermodynamic potential.
  • These phenomena are surface-related.

• Problem Solution
  
  • Maximize surface area-to-volume ratio - Maximize kinetics (i.e. Speed) of heat sink
  • Practical Solution - Use efficient atomization technique to deploy Water as a Fine Mist (Spray).

• No official definition of average droplet size
• Water as a fine mist (spray)
• Genuine Water Mist Systems - volume median diameter of 50-200 micron
• BFPSA/Eurofeu - maximum diameter of 400 micron
• NFPA - maximum diameter of 1000 micron
• Minimum permitted diameter of 40 micron
• Considerably less agent than traditional deluge & spray systems.
• Substantial system capability
• Weight benefits
• Negligible secondary water damage in the protected zone.
• Additional benefits of thermal radiation attenuation
• Removal of a proportion of airborne smoke particulate
• Absorption of water-soluble toxic & irritant gases
• VDM of ca. 150 micron
• 10% only of water volume in droplets < 50 micron
• 10% only of water volume in droplets > 250 micron

Sprinkler & Water Mist

• Operating pressure:
  • Sprinkler: 1-12 bar
  • Mist System: 3-300 bar

• Droplet diameter:
  • Sprinkler: 1-2mm
  • Mist System: 50-200 micron

• Deposition rate:
  • Sprinkler: 4-16 L min^-1
  • Mist System: 3-15 L min^-1

• Discharge time:
  • Sprinkler: 30-120 min
  • Mist System: 15 sec - 6 min

• Water mist has been proved to be extremely efficient in tackling Class B (Liquid Hydrocarbon) Fires
• The Kidde system is, therefore, ideally suited to the protection of Gas Turbine Packages & other Rotating Machinery Units.
• Initial trials were conducted at Kidde's corporate research facility in UK.
• This was followed by a program comprising several hundred tests in a full scale simulated gas turbine enclosure on the Milan premises of KFP's sister company, Silvani.
• These latter trials at Silvani represented a significant advance on earlier studies, since the suppression system featured a self-contained production specification skid operated via a control panel linked to Flame Detectors.
• Kidde Water Mist System
• A risk-specific solution for local applications & numerous fire threats
• Non-toxic / No moving parts
• Highly efficient fire suppression capability
• Wide range of Class B (liquid hydrocarbons) applications

• Customized engineering
• Modular extinguishing packages
• Stored pressure systems
• Dry pipe manifold avoids freezing problems
• Coupling to hazard detection & alarm systems
• (Optional) Discharge programming

Factors in System Design

• Fire Risk Scenario:
  • Fuel Type
  • Quantity
  • Configuration

• Geometry of protected zone
• Ventilation effects
• Temperature conditions
• Factors in System Design:
• Unit location & ambient conditions
• Existing hazard detection & control
• Proposed hazard detection & control
• Materials & component specifications

• Rapid extinguishment of liquid hydrocarbon fires
• Prevention of fire spread - Immediate attenuation of radiated heat - Surface wetting
• Minimal water use - System capacity & weight benefits - Negligible secondary water damage
• Degree of smoke stripping
• Scrubbing of toxic / irritant water-soluble gases
• Attainment of survivable atmosphere

• Consultancy services - Feasibility & risk analysis
• Scientific & technical services - KI Research / KFP Engineering
• System design & engineering as "Design Authority"
• Manufacture & Supply
• Installation supervision & commissioning