WJH FAA Technical Center

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WJH FAA Technical Center John W. Reinhardt Fire
Safety Section, AAR-440 Atlantic City Intl
Airport, New Jersey 08405 609.485.5034
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• OBJECTIVES
• To determine the critical parameters required
  to scale a water mist system combined with
  nitrogen, used as an aircraft cargo compartment
  fire suppression system that have met the MPS.

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CONSIDERATION The scaling consideration
of the water mist/N2 fire extinguishing system is
for cargo compartments of volume sizes of 719 ft3
(298 in x 125 in x 42 in) and 6252 ft3 (590 in x
164 in x 80 in).
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• ADOPT NFPA 750 STANDARD ON WATER MIST
• FIRE PROTECTION SYSTEMS
• This NFPA document was prepared by the Technical
  Committee on Water Mist Fire Suppression Systems
  and acted on by the National Fire Protection
  Association, Inc. on November 1999. It was
  issued by the Standards Council on January 2000,
  with an effective date of February 11, 2000
• In developing this standard, the committee
  addressed system components and hardware, system
  types, installation requirements, design
  objectives, hazard classifications, calculations,
  water supplies, atomizing media, plans,
  documentation, acceptance criteria, and
  maintenance considerations
• NFPA 750 represents a significant advancement in
  water mist technology and the knowledge base
  associated with its application.

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• SCALING APPROACH
• Characterize the WMS/N2 system that passed the
  MPS tests using the NFPA 750 standard and other
  techniques
• Use defined system parameters and transpose them
  to different scale cargo compartment, paying
  close attention to the vertical plane (z-axis).
  Adjust system as needed in scaled compartment to
  provide same critical parameters values.

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• CHARACTERIZATION OF WATER MIST
• NFPA 750 Section A-5-2 (Appendix A)
• System Flow Rate
• System Operating Pressure
• General Water Requirements
• Nozzle Characteristics
• Nozzle Spray Characteristics
• Nozzle Installation Parameters
• Activation Device
• General Design Parameters

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• CHARACTERIZATION OF WATER MIST (CONT.)
• NFPA 750 Section A-2-6.1 (Appendix A)
• Will characterize FAAs WMS/N2 system using the
  recommended method to determine the cumulative
  volumetric distribution of water droplets
• NFPA 750 Section B-1 (Appendix B Water Mist
  Droplet Size Characterization and Measurement)
• If the equipment is available, will
  characterize FAAs WMS/N2 system using one of the
  following techniques optical imaging,
  diffraction, or Doppler refraction (Sauter Mean
  Diameter, Dv0.10).

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• CHARACTERIZATION OF WATER MIST (CONT.)
• Water collection (mass flow) on a 18 by 18 pan
  located on the fire zone at 36 above the cargo
  compartment floor in order to determine water
  availability.

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• NITROGEN MEASUREMENT
• The measurement of the nitrogen volumetric
  concentration, in the scaled cargo compartment,
  will be achieved by determining the oxygen
  volumetric concentration in the hypoxic condition
  (using gas analyzers).
• COMPUTER MODELING
• Task group member recommended usage of computer
  modeling techniques to facilitate scaling
  analysis using critical characterized parameters.
  It may be used If provided by task group member.

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• STATUS
• The characterization of the FAAs WMS/N2 has been
  initiated using the NFPA 750 standard.
• Test fixtures to determine water mass in the fire
  zone is under construction
• Searching for a Phase Doppler Particle Analyzer
  or similar equipment to measure particle size
  distribution and velocity of the mist on the fire
  zone. Anyone who owns one and is willing to
  share the equipment please contact John Reinhardt
  at 609-485-5034 or john.reinhardt_at_faa.gov