EPA-600/R-97-006
February 1997
DEVELOPMENT OF ALTERNATIVE. NON-IIALON FIRE PROTECTION SYSTEM
by
Roger A. Patterson, Garth Gobeli, and Robert E. Tapscott
Center for Global Environmental Teehnologies
New Mexico Engineering Research Institute
The University of New Mexico
Albuquerque, New Mexico 87131 -1376
and
Philip J. DiNenno
Hughes Associates, Inc.
6770 Oak Hall Lane, Suite 125
Columbia, Maryland 21045
EPA Contract Number 68-D3-014!
Project Officer:
Theodore G. Brna
Air Pollution Prevention and Control Division (MD-63)
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. North Carolina 2771 I
Prepared for:
U.S. ENVIRONMEN TAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
WASHINGTON. D.C. 20460
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NOTICE
This document h3S been reviewed in accordance with
U.S. Environmental Protection Agency policyand
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
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FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with pro-
tecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions lead-
ing to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research
program is providing data and technical support for solving environmental pro-
blems today and building a science knowledge base necessary to manage our eco-
logical resources wisely, understand how pollutants affect our health, and pre-
vent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks
from threats to human health and the environment. The focus of the Laboratory's
research program is on methods for the prevention and control of pollution to air,
land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites and groundwater; and prevention and
control of indoor air pollution. The goal of this research effort is to catalyze
development and implementation of innovative, cost-effective environmental
technologies; develop scientific and engineering information needed by EPA to
support regulatory and policy decisions; and provide technical support and infor-
mation transfer to ensure effective implementation of environmental regulations
and strategies.
This publication has been produced as part of the Laboratory's strategic long-
term research plan. It is published and made available by EPA's Office of Re-
search and Development to assist the user community and to link researchers
with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
i 11
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PREFACE
This report was prepared by the Center for Global Environmental Technologies (CGET), Advanced
Protection Technologies Division (APT). New Mexico Engineering Research Institute (NMERI), The University of
New Mexico, Albuquerque, New Mexico, and by Hughes Associates, Inc. (HAI), Columbia, Maryland, under
NMERI Project Number 31840 for the Atmospheric Protection Branch, Air Pollution Prevention and Control
Division. National Risk Management Research Laboratory (NRMRL), U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina. The NRMRL Project Officer is Theodore G. Brna, the NMERI Principal
Investigator is Robert E. Tapscott, with Roger A. Patterson, NMERI Project Manager, and Philip J. DiNenno,
Hughes Associates, Inc., (HAI) Project Manager.
This report is submitted in partial fulfillment of Contract Number 68D30141 by The University of New
Mexico under the sponsorship of the National Risk Management Research Laboratory of the U.S. Environmental
Protection Agency. This report covers a period from September 1993 to December 1995 and work was completed
as of December 1995.
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ABSTRACT
Public concern over depletion of stratospheric ozone by halogenated compounds first became focused
following a 1974 article by M. J. Molina and F. S. Rowland. The Montreal Protocol, an international treaty signed
in 1987. restricted the consumption of chlorofluorocarbons lor all applications and also placed a cap on the
consumption of halons. Effective I January 1994, consumption (production plus imports minus exports) was phased
out in the United States for all but essential uses. Owing to increased concerns about global warming, atmospheric
lifetime, and ozone depletion, halocarbons are becoming less acceptable as halon replacements, and alternatives are
receiving increased attention.
This report describes the effort to identify, test, and assess a system to extinguish fires using a technology
that does not require a halocarbon extinguishing agent. Recently, two alternative technologies—water mist system
(WMS) fire suppression technologies and low-residue particulate (LRP)—have come to the attention of researchers.
These technologies allow the use of water or dry chemicals in reduced quantities to provide acceptable fire
protection. Since the amount of agent required is reduced, collateral damage due to the extinguishing agent may be
significantly decreased. Moreover, these technologies may allow water or dry chemicals to act somewhat like total-
flood agents, permitting incrtion and extended-period protection. The project reviewed the technologies of WMSs
and low-residue particulate systems with regard to fire protection. The state-of-the-art was evaluated in view of the
current technology and the potential for near-term improvements.
Based upon the results of the information search and the assessment of the state-of-the-art for water mist fire
suppression systems (WMSs) and LRPs, WMS was recommended as the most promising near-term technology for
evaluation in this experimental program. The experimental program was to define and optimize the operating
parameters for a WMS at laboratory scale, followed by system development studies, and room-scale testing. Based
upon the success of this effort, the final project task was an engineering design and cost comparison of WMSs with
respect to the equivalent as halon system.
The significant findings from the laboratory-scale experiments were as follows: (1) fires can be
extinguished with water flux levels as low as 0.025 L/min-m2; (2) for water flux levels between 0.025 L/min-nr and
0.6 L/min-m2, the times required to extinguish the fires followed a Gaussian distribution; (3) increasing the water
ilux above 0.61./min-m" does not significantly decrease the time required to extinguish the fires in comparison to the
amount of water used; and (4) WMS does not turn corners or penetrate obstructions easily. While demonstrating that
V
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WMS can replace halon systems in some applications, the last finding indicates that WMSs do not work like totally
gaseous agents.
Room-scale experiments demonstrated that scale-up from the laboratory is straightforward. At a water flux
level of 0.46 L/min-m2, the WiMS was capable of extinguishing both Class A and B fires. Significant findings from
the room-scale testing were: (1) at the water flux levels tested, the WMS could neither inert a space (i.e., make the
contents of the space noncombustible) nor stop reignition of a hydrocarbon pool fire; (2) upon reignition, the WMS
could repeatedly reextinguish the fire; and (3) fires could be extinguished without causing collateral damage to
books, papers, and cnergi/ed electrical (computer) systems.
The engineering design and cost of WMSs indicate a high-end cost estimate of $90 to $150/m3 across a
range of technologies. For low-pressure, water-only mist systems, this cost could be reduced to below $30/m i. It is
expected that the cost of WMS will decrease over time as additional competitors enter the market and R&D costs are
recovered. Given the high cost of available recycled Halon 1301 (approximately S.'iO/kg), halon systems now
average $125/m3, and as banked supplies decrease halon costs arc expected to rise. Therefore, WMSs appear to be
cost competitive with Halon 1301 in many applications.
The end product of this effort is this report summarizing in detail all the work performed under the contract,
as well as conclusions based upon the results obtained and recommendations for any needed follow-up work.
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CONTENTS
PRRFACE i V
ABSTRACT V
FIGURES X
TABLES xiv
ABBREVIATIONS AND SYMBOLS XVI
ACKNOWI .EDGMENT X V i i
1 INTRODUCTION 1
BACKGROUND 1
ALTERNATIVE TECHNOLOGIES 2
Water Mist 2
Low-Residue Particulate (LRP) 3
PROJECT REQUIREMENTS AND DELIVERABLES 4
Task 1 - Assessment of Available Information on Alternative Protection Methods 4
Task 2 - Experimental Program and Fire Suppression System 4
Task 3 - Engineering and Cost Evaluation of WM System 5
2 CONCLUSIONS 6
3 RECOMMENDATIONS 9
4 PROJECT DESCRIPTION 11
TASK 1: ASSESSMENT OF AVAILABLE INFORMATION ON ALTERNATIVE
PROTECTION METHODS 11
TASK 2: EXPERIMENTAL TEST PROGRAM 12
TASK 3: ENGINEERING AND COST EVALUATION OF A WATER MIST SYSTEM 13
5 TASK 1: ASSESSMENT OF AVAILABLE INFORMATION ON ALTERNATIVE
PROTECTION METHODS 15
REVIEW OF WATER MIST FIRE SUPPRESSION TECHNOLOGY 15
Introduction 15
Background 16
Theoretical Considerations 16
Misting/Atomization Technology 20
Experimental Evaluation of Water Mist Systems 34
Overall Test Review and Conclusions 43
REVIEW OF LOW-RESIDUE PARTICULATE (LRP) IN FIRE SUPPRESSION
TECHNOLOGY 45
Introduction 45
Background 46
vi i
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CONTENTS (CONTINUED)
Theoretical Considerations 47
Commercial Low-Residue Particulate Fire Suppression System Technology 49
Overview of Testing to Date 49
LRP Conclusions 50
Recommendations 5 i
ASSESSMENT OF THE "STATE-OF-THE-ART" FOR WATER MIST (WM) AND
LOW-RESIDUE PARTICULATE (LRP) SYSTEM FIRE SUPPRESSION TECHNOLOGY 52
Status of Water Mist Fire Suppression System Technology 52
Status of Low-Residue Particulate Fire Suppression Technology 53
SELECTED EXPERIMENTAL INVESTIGATION 53
6 TASK 2: EXPERIMENTAL TEST PROGRAM 55
INTRODUCTION 55
OBJECTIVE 56
METHODOLOGY 56
Laboratory-Scale Experiments 56
Room-Scale Experiments 61
LABORATORY-SCALE EXPERIMENTAL RESULTS 62
Aerosol Test Chamber (ATC) Results 62
Fraunhofer Versus Malvern Comparison 64
Alternative Test Method - Water Mist Extinguishment Test Results 64
Optimum Nozzle Layout for Room-Scale Testing 72
Determination of Required Water Flux 73
Partially and Fully Obstructed Fires 76
ROOM-SCALE TEST RESULTS 76
Intermediate Field-Scale Test Site 76
Room-Scale Testing of the Water Mist Fire Suppression System 78
Post-Fire Storage and Operation of the Persona! Computer 88
SUMMARY OF FINDINGS ON MECHANISMS OF FIRE EXTINGUISHMENT 88
7 QUALITY ASSURANCE 91
INTRODUCTION 91
QUALITY ASSURANCE SUMMARY 91
DATA QUALITY INDICATOR GOALS 91
Initial Test Methods 91
Alternative Test Method 92
DATA QUALITY INDICATOR RESULTS 92
Introduction 92
Mist Concentration 93
Air Flow 95
Temperature and Relative Humidity 96
Water Flow 100
Fraunhofer Instrument 101
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CONTENTS (CONCLUDED)
Water Flux and Extinguishment Testing 101
8 TASK 3: ENGINEERING AND COST EVALUATION OF A WATER MIST SYSTEM 102
INTRODUCTION 102
Cost Estimates 103
SYSTEM TYPES AND OPERATING PRINCIPLES 104
High-Pressure, Single-Fluid System 104
Hybrid Pump/Stored Pressure System 106
Low-Pressure, Single-Fluid System 107
Low-Pressure, Dual-Fluid Systems 107
FIRE SUPPRESSION CAPABILITY 109
MARINE ENGINE ROOM AND MACHINERY SPACE APPLICATIONS 109
Cost Comparison (Marine Engine Room) 110
COMBUSTION TURBINE ENCLOSURES 112
Performance Requirements and General Specifications 112
Cost Estimates 114
EMERGENCY DIESEL GENERATOR ROOM 115
SUMMARY 116
REFERENCES 117
BIBLIOGRAPHY 121
APPENDICES
A DEVELOPMENT OF THE FRAUNHOFER SMALL ANGLE DIFFRACTION INSTRUMENT 130
B FRAUNHOFER VERSUS MALVERN SERIES 2600 PARTICLE SIZE COMPARISON 157
C SUPPLEMENTARY FIGURES 172
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FIGURES
Number Page
1 Experimental apparatus for aerosol fire suppressant evaluation 13
2 Simplified critical concentration analysis 18
3 Water droplet free-fall characteristics 19
4 Schematic of a typical Grinnell AquaMist System (low pressure) 25
5 Schematic of a typical Microguard Unifog System 26
6 Schematic of a Baumac MicroMist System nozzle array for subfloor test scenario 31
7 Test fire scenarios 36
8 Engine model 40
9 Summary of tests performed with a six-percent hydrogen in air mixture ignited in the presence of WM 44
10 Aerosol test chamber (ATC) 58
11 Water-flux gravimetric sample pattern 61
12 Droplet size distribution for a MX-20. 40 cm below the nozzle and at 6.90 MPa 63
13 Droplet size distribution for a MX-8, 40 cm beiow the nozzle and at 6.90 MPa 63
14 Droplet size distribution: MX-8/20 spray at 6.90 MPa and air flow of 4.53 m3/min 64
15 MX-8 nozzle droplet size distribution dependence on pressure at 40.6 cm 70
16 Extinguishment times as a function of water flux for two Baumac nozzles 70
17 Gaussian distribution of the variances in extinguishment below the critical concentration 71
18 Water flux for a seven-nozzle Baumac MX-8 array at 40.6 cm spacing. 73
19 Water flux pattern for a four-nozzle Baumac MX-8 array at 50.8 cm spacing 74
20 Water flux pattern for a four-nozzle Baumac MX-8 array at 40.6 cm spacing 74
21 Water flux pattern for a four-nozzle Baumac MX-8 array at 30.5 cm spacing 75
22 Water flux pattern for a single Baumac MX-8 nozzle at 3.45 MPa 75
23 Exterior view of the NMERI Field-Scale Test Chamber 77
24 Interior layout of the NMERI Field-Scale Test Chamber 77
25 Baumac MX-8 System layout for room-scale testing 79
26 Partially and fully obstructed fire test feature 79
27 Temperature variation at four locations as a function of operating time for an unobstructed
32-kW heptane pool fire subjected to WM 82
28 Temperature variation at four locations as a function of operating time for an obstructed
32-kW heptane pool fire subjected to WM 82
29 Temperature variation at four locations as a function of operating time for an obstructed (cabinet)
32-kW heptane pool fire subjected to WM 83
X
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FIGURES (CONTINUED)
Number Page
30 Temperature variation at two locations as a function of operating time for multiple reignitions of a
32-kW heptane pool fire subjected to WM 84
31 Telltale position and numbering for room-scale testing 85
32 Temperature variation at the geometric center of a basket containing shredded paper as a function of
operating time for a fire subjected to WM 87
33 Room layout for unobstructed 1/2 wood crib fires 87
34 Water inist collection apparatus 94
35 Traverse lines for airflow measurement in the intake duct 96
36 Initial air flow test results 97
37 Air flow test results with foam filter 98
38 Analysis of air flow and placement of the anemometer 99
39 Relative standard deviation as a function of air velocity 100
40 High-pressure water mist system for a machinery space 105
41 Stored high-pressure water mist system for an emergency diesel generator space 106
42 Dual-fluid system schematic 108
A-1 Exterior view of a Fraunhofer Diffraction Detector 130
A-2 Optical schematic for Fraunhofer apparatus 133
A-3 Schematic of detector showing sample diameters SI and S2 133
A-4 Laser interferometry/visibility (LIV) experimental setup 135
A-5 Phase Doppler (PD) experimental arrangement 136
A-6 Scattered light interference pattern 137
A-7 Schematic for the Three-detector aperture for PD measurements 137
A-8 Light scattering geometry 139
A-9 Wiring diagram for conversion of scanner to detector 143
A-10 Adjustments for laser and expanding telescope 145
A-11 Cross section of barrel mount showing location of focal spot 147
A-12 Detector detail, including cover glass 148
A-13 Detector positions in the aerosol test chamber 152
xi
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FIGURES (CONTINUED)
Number Page
B-l Calibration reticle on the Malvern instrument 160
B-2 Nebulizer aerosol data from the Malvern 160
B-3 Malvern analysis - MX-8/20 spray at 3.45 MPa and 4.53 mVmin 161
B-4 Malvern analysis - MX-8/20 spray at 6.90 MPa and 4.53 m'Vmin 161
B-5 Malvern analysis - MX-8/20 spray at 6.90 MPa and 7.08 m'Vmin 162
B-6 Malvern analysis - MX-20 spray at 3.45 MPa and 4.53 m3/min 162
B-7 Malvern analysis - MX-20 spray at 6.90 MPa and 4.53 m3/min 163
B-8 Malvern analysis - MX-20 spray at 6.90 MPa and 7.08 mVmin 163
B-9 Malvern analysis of MX-8, 14 cm below the nozzle at 3.45 MPa and 8.1 x 10 s m'Vmin 164
B 10 Malvern analysis of MX-8, 14 cm below the nozzle at 6.90 MPa and 1.3 x 104 mVmin 164
B-11 Malvern analysis of MX-8,40 cm below the nozzle at 3.45 MPa and 8.1 x 10" mVmin 165
B-l 2 Malvern analysis of MX-8,40 cm below the nozzle at 6.90 MPa and 1.3 x 10"4 m3/min 165
B-l 3 Malvern comparison of MX-8, 14 cm below the nozzle at 3.45 MPa and 8.1 x I0"5 mVmin and
6.90 MPa and 1.3 x 104 mVmin 166
B-14 Malvern comparison of MX-8, 40 cm below the nozzle at 3.45 MPa and 8.1 x 10 5 tnVmin and
6.90 MPa and 1.3 xlO"1 m Vmin 166
B-15 Malvern analysis of MX-20, 14 cm below the nozzle at 3.45 MPa and 3.1 x 10"3 nrVmin 167
B-l 6 Malvern analysis of MX-20, 14 cm below the nozzle at 6.90 MPa and 3.5 x 10"3 m'Vmin 167
B-17 Malvern analysis of MX-20, 40 cm below the nozzle at 3.45 MPa and 3.1 x 103 m3/min 168
B-l 8 Malvern analysis of MX-20, 40 cm below the nozzle at 6.90 MPa and 3.5 x 10"3 nr/min 168
B-l9 Malvern comparison of MX-8. 14 em below the nozzle at 3.45 MPa and 3.1 x 10"3 tnVmin and
6.90 MPa and 3.5 x 10"' mVmin 169
B-20 Malvern comparison of MX-20, 40 cm below the nozzle at 3.45 MPa and 3.1 x 103 mVmin and
6.90 MPa and 3.5 x 10"3 mVmin 169
B-21 Schematic of the Fraunhofer Detector 170
B-22 Calibration reticle on the Fraunhofer instrument 170
B-23 Nebulizer aerosol data from the Fraunhofer instrument 171
C-l Water flux for a Grinnel! AM-11 nozzle at 2.75 MPa 173
C-2 Water flux for a Grinnell AM-11 nozzle at 1.72 MPa 173
C-3 Reproducibility analysis of a Grinnell AM-11 nozzle at 2.75 MPa 174
C-4 Reproducibility analysis of a Grinnell AM-11 nozzle at 1.72 MPa 174
C-5 Water flux for a three-nozzle BETE P-54 System at 2.59 MPa 175
C-6 Water flux for a three-nozzle BETE P-54 System at 1.38 MPa 175
C-7 Reproducibility analysis for a three nozzle BETE P-54 System at 2.59 MPa 176
C-8 Reproducibility analysis for a three-nozzle BETE P-54 System at 1.38 MPa 176
xi i
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FIGURES (CONCLUDED)
Number Pajic
C-9 Water flux for a three-nozzle BETE PJ-40 System at 6.90 MPa 177
C-10 Water flux for a three-nozzle BETE PJ-40 System at 1.38 MPa 177
C-11 Reproducibility analysis of a three-nozzle BETE PJ-40 System at 6.90 MPa 178
C-12 Reproducibility analysis of a three-nozzle BETE PJ-40 System at 1.38 MPa 178
C-13 Water flux for a 14-nozzle Baumac MX-20 System at 6.90 MPa. 179
C-14 Water flux for a 14-nozzle Baumac MX-20 System at 3.45 MPa 179
C-15 Reproducibility analysis of a 14-nozzle Baumac MX-20 System at 6.90 MPa 180
C-16 Reproducibility analysis of a 14-nozzle Baumac MX-20 System at 3.45 MPa 180
C-17 Water flux for a 14-nozzle Baumac MX-8 System at 7.24 MPa 181
C-l 8 Water flux for a 14-nozzle Baumac MX-8 System at 3.93 MPa 181
C-19 Reproducibility analysis of a 14-nozzle Baumac MX-8 System at 7.24 MPa 182
C-20 Reproducibility analysis of a 14-nozzle Baumac MX-8 System at 3.93 MPa 182
C-21 Water flux for a single BETE PJ-40 nozzle at 7.07 MPa 183
C-22 Water flux for a single BETE PJ-40 nozzle at 1.38 MPa 183
C-23 Reproducibility analysis for a BETE PJ-40 single nozzle at 7.07 MPa 184
C-24 Reproducibility analysis for a BETE PJ-40 single nozzle at 1.38 MPa 184
C-25 Water flux for a seven-nozzle Baumac MX-8 System at 6.90 MPa 185
C-26 Water flux for a seven-nozzle Baumac MX-8 System at 3.45 MPa 185
C-27 Reproducibility analysis for a seven-nozzle Baumac MX-8 System at 6.90 MPa 186
C-28 Reproducibility analysis for a seven-nozzle Baumac MX-8 System at 3.45 MPa 186
C-29 Water flux for a four-nozzle Baumac MX-8 System at 3.45 MPa 187
C-30 Reproducibility analysis for a four-nozzle Baumac MX-8 System at 3.45 MPa 187
C-31 Water flux for a single Baumac MX-8 nozzle at 6.90 MPa 188
C-32 Water flux for a single Baumac MX-8 nozzle at 3.45 MPa 188
C-33 Water flux for an obstructed seven-nozzle Baumac MX-8 System at 3.45 MPa 189
C-34 Reproducibility analysis for an obstructed seven-nozzle Baumac MX-8 System at 3.45 MPa 189
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TABLES
Number Page
1 WATER MIST HARDWARE MANUFACTURERS 23
2 WATER MIST SYSTEM TYPES 23
3 FIREFIGHTING OVERVIEW OF WATER MIST SYSTEMS: PROBABILITY OF SUCCESS (%)
AS A FUNCTION OF FIRE CONFIGURATION 37
4 DESIGN CRITERIA FOR A WATER MIST TOTAL-FLOOD FIRE SUPPRESSION SYSTEM IN
MACHINERY ENCLOSURES 42
5 MANUFACTURERS' OPERATING DATA FOR NOZZLES SELECTED FOR TESTING 59
6 WATER PRESSURE AND WATER FLOW TEST MATRIX 60
7 EXTINGUISHMENT RESULTS FOR A SINGLE-NOZZLE GRLNNELL AM-11 SYSTEM 65
8 EXTINGUISHMENT RESULTS FOR A THREE-NOZZLE BETE P-54 SYSTEM 65
9 EXTINGUISHMENT RESUL TS FOR A THREE-NOZZLE BETE PJ-40 SYSTEM 66
10 EXTINGUISHMENT RESULTS FOR A 14-NOZZLE BAUMAC MX-20 SYSTEM 66
11 EXTINGUISHMENT RESULTS FOR A 14-NOZZLE BAUMAC MX-8 SYSTEM 67
12 EXTINGUISHMENT RESULTS FOR A SINGLE-NOZZLE BETE PJ-40 SYSTEM 67
13 EXTINGUISHMENT RESULTS FOR A SEVEN-NOZZLE BAUMAC MX-8 SYSTEM 68
14 EXTINGUISHMENT RESULTS FOR A FOUR-NOZZLE BAUMAC MX-8 SYSTEM 68
15 EXTINGUISHMENT RESULTS FOR A SINGLE-NOZZLE BAUMAC MX-8 SYSTEM 69
16 EFFECT OF NOZZLE SPACING ON EXTINGUISHMENT FOR BAUMAC MX-8 NOZZLES 72
17 EXTINGUISHMENT RESULTS FOR AN OBSTRUCTED BAUMAC MX-8 SYSTEM 76
18 ROOM-SCALE TEST SCENARIOS FOR THE BAUMAC MX-8 WATER MIST FIRE
SUPPRESSION SYSTEM 80
19 ROOM-SCALE CLASS B (HEPTANE) EXTINGUISHMENT TESTING OF THE BAUMAC MX-8
WATER MIST SYS'l'EM 81
20 ROOM-SCALE TELLTALE EXTINGUISHMENT WITH THE BAUMAC MX-8 WATER MIST
SYSTEM 84
21 ROOM-SCALE CLASS A EXTINGUISHMENT TESTING OF THE BAUMAC MX-8 WATER
MIST FIRE SUPPRESSION SYSTEM 86
22 SUMMARY OF COLLECTED DATA AND GOALS FOR PRECISION, ACCURACY.
AND COMPLETENESS 92
23 SUMMARY OF WATER MIST TEST CONDITIONS 93
XIV
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TABLES (CONCLUDED)
Number Page
24 COST COMPARISON FOR A 1500-M3 MARINE ENGINE ROOM 111
25 WATER AND NITROGEN REQUIREMENTS FOR A HIGH-PRESSURE SINGLE-FLUID
SYSTEM 113
26 WATER AND NI TROGEN REQUIREMENTS FOR A LOW-PRESSURE TWIN-FLUID SYSTEM.... 114
27 EQUIPMENT SUMMARY FOR AN AIR ATOMIZED SELF-CONTAINED SYSTEM 114
28 INSTALLED COST COMPARISON FOR EMERGENCY DIESEL GENERATOR ROOM 116
A-1 POSITION/EQUIPMENT MATRIX FOR MEASUREMENTS 153
B-1 MEDIAN DATA FOR THF. CALIBRATION RETICLE ON THE FRAUNHOFER INSTRUMENT 159
B-2 NEBULIZER MEDIAN DATA FOR ND 4.0 AND ND 3.5 FILTERS 159
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ABBREVIATIONS and symbols
Abbreviations
AISI
-- American Iron and Steel Institute
APT
— Advanced Protection Technologies
ASME
- American Society of Mechanical
Engineers
ASTM
-• American Society for Testing and
Materials
ATC
- aerosol test chamber
ATES
— Albuquerque Technology and
Educational Services. Inc.
CCD
-- charged coupled device
CFC
- chlorofluorocarbon
CGA
-- combustion generated aerosol
CGET
-- Center for Global Environmental
Technologies
CRD A
- Cooperative Research and
Development Agreement
CS
-- control system
DA
— data acquisition
DIN
— Deuisches Industry Norm
DOD
— Department of Defense
dpi
-- dots per inch
DQI
— data quality indicator
EPA
— Environmental Protection Agency
EPTP
-- experimental program test plan
FAA
— Federal Aviation Administration
FD
-- Fraunhofer Diffraction
FL
— focal length
FM
- Factory Mutual. Inc.
FSTC
-- field-scale test chamber
FWS
-- fine water spray
HAI
-- Hughes Associates. Inc.
IMO
— International Maritime Organization
LED-PD
— light emitting diode-photo diode
LEETC
-- laboratory extinguishment and
emissions test chamber
LIV
-- laser interferometry/visibility
LRP
— low-residue paniculate
MSC
- Maritime Safety Committee
MSDS
-- Material Safety Data Sheet
NFPA
— National Fire Protection Association
NMERI
— New Mexico Engineering Research Institute
NMRI
— Naval Medical Research Institute
NRCC
— National Research Council of Canada
NRL
- Naval Research Laboratory'
NRMRL
— National Risk Management Research
Laboratory
PC
— personal computer
PD
— phase doppler
PGA
-- pyroiechnically generated aerosols
PGSP
-- propellant generated solid
particulates
PI
— principal investigator
QA
-- quality assurance
QAPP
- quality assurance project plan
QC
-- quality control
R&D
— research and development
RH
— relative humidity
RSD
- relative standard deviation
Rn
— response time index
SFE
- Spectrex Fire Extinguishant
SNL
-- Sandia National Laboratories
SOP
— standard operating procedure
SSOP
— safety standard operating procedures
TD
— to deliver
UL
— Underwriters Laboratories, Inc.
USCG
-• United States Coast Guard
WL/FIVCF -- Wright Laboratories
WM
— water mist
WMS
-- water mist system
WPAFB - Wright-Patterson Air Force Base
Symbols
- -
approximately
X -
wavelength of incident radiation
Jim ~
micrometers
< --
less than
C -
constant factor including light intensity
f -
lens focal length
h -
zeroth order Bessel function
I, -
first order Bessel function
L --
light energy falling into one of the
concentric ring regions
N; -
number density of droplets/panicles of
radius r;
ri —
droplet/panicle radius
S --
distance in detector plane from unscattered
radiation focal position
s, ~
inner radius
S2 ~
outer radius
rh „
maximum vent flow
A --
area
H -
height
XVI
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ACKNOWLEDGMENT
The authors wish to acknowledge the technical assistance of Timothy J. O'Hern, Sandia National
Laboratories (SNL), who collaborated in the Malvern comparison and calibration work on the Fraunhofer
instrument.
XV i i
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SECTION 1
INTRODUCTION
BACKGROUND
Concern over depletion of stratospheric ozone by halogenated compounds came to the public's attention
following a 1974 article by M. J. Molina and F. S. Rowland (1). By 1978, the United States had banned the use of
chlorofluorocarbons (CFCs) in nonessential aerosol products because of concerns that their use would deplete
protective stratospheric ozone. In spite of this control, the global production and use of CFCs in other applications
continued to rise. As a result of this rise in production and use, a series of national and international regulatory
actions was enacted. The Montreal Protocol, an international treaty signed in 1987, restricted the consumption of
CFCs for nearly all applications and placed a cap on production of halons, limiting them to 1986 production levels.
The 1990 London amendments to the Protocol increased the restrictions on CFCs and halons, with halon
production levels required to be 50 percent of 1986 production and total phaseout coming in 2000. The amendments
also placed restrictions on additional chlorine- and bromine-containing materials. The Copenhagen revisions in
November 1992 saw all major signatories agree to phase out halons by 1 January 1994. Although production ceased,
halon itself is not banned. Halons can still be used for essential applications, but supplies are. limited, coming
primarily from halon "banks" (retired systems). Due to the then existing though limited—supplies, it is expected
that few, if any, new uses of halons in the U.S. will be deemed essential.
Halon substitutes can be divided into two types: replacements and alternatives (2). Replacements arc
halon-like agents, e.g., halocarbons. Alternatives are non-halon-like materials, sometimes called "not-in-kind"
agents (e.g., dry chemicals, inert gases, foam, water, carbon dioxide). Nearly all work on halon replacements has
focused on halocarbon replacements. This is, in part, due to two factors: (1) most industrial research has been
funded by companies whose principal products are halocarbons, and (2) most non-industrial research has been
funded by the Department of Defense (DoD), which emphasizes the ability to continue operations during fire and
explosion events (a requirement that has been thought to disallow the use of agents other than halocarbons). Another
factor, however, is that until recently it was believed that most alternatives would cause unacceptable levels of
collateral damage due to the extinguishing agent in many applications (.water, dry chemicals, and foams) or would
threaten room occupants with asphyxiation (carbon dioxide, inert gases). Owing to increased concerns about global
warming, atmospheric lifetime, and ozone depletion, however, halocarbons are becoming less acceptable as halon
replacements, and alternatives are receiving increased attention. Recently, two alternative technologies—water
misting (WM) and low-residue particulate (LRP)— have emerged as possible replacements for halons in selected
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applications. These technologies may allow the use of water or dry chemicals in reduced quantities to provide fire
protection. Since the amount of agent required is reduced, secondary damage may be. significantly reduced.
Moreover, these technologies may allow water or dry chemicals to act somewhat like total-flooding agents,
permitting inertion and extended-period protection. This report documents the evaluation of the above technologies
and the development of a fire protection system using one of these technologies (water misting).
ALTERNATIVE TECHNOLOGIES
Starting in the late 1940s and during the 1950s, low-residue particulate (L.RP) and water mist (WM) fire
suppression technologies were being developed as specialty applications substituting for dry chemical and water
sprinkler systems, respectively, in areas where weight and materials compatibility problems were encountered. The
introduction of halons in the early 1960s caused these systems to be set aside, since halons appeared to eclipse the
need for other systems or refinements for extinguishment, particularly of electrical or flammable liquid fires. With
international environmental agencies agreeing to phase out halons, based on the Montreal Protocol of 1987, LRP and
WMSs have re-emerged as possible alternatives to halon fire suppression systems. Renewed interest in LRP and
WMS technologies has been accelerating since 1990.
Water Mist
Water mist systems allow the use of fine water sprays to provide fire protection with reduced water
requirements and reduced secondary damage. Water suppresses or extinguishes fires through three, predominant
mechanisms that act together. These mechanisms are (1) heat extraction using water's latent heat of vaporization and
gas-phase cooling, (2) oxygen displacement by steam expansion, and (3) radiant heat attenuation involving surface
cooling by surface wetting/evaporation and blocking of radiant heat transfer. Calculations indicate that on a weight
basis, water is a more effective fire extinguisliant than halons, provided complete or near-complete evaporation of
water is achieved. Since small droplets evaporate significantly faster than large droplets, the small droplets produced
with WMSs provide this capability while potentially reducing water requirements and secondary damage. Although
no criteria have been established on the dividing line between mists and sprays, mists are tentatively defined to have
droplets 200 micrometers (pm) or less in size (a number that may change). Two types of fire protection systems
have been considered: one using pressure to force water through small openings (single-fluid systems) and the
second using a pressurized gas, usually nitrogen, to atomize the water into droplets (dual-fluid systems). Although
the concept of water misting is not new, significant work is needed to determine the potential of water misting
systems in fire suppression. The ability of water mists to stay suspended and to reduce explosion overpressures in
explosion protection must also be assessed. A research and development program is required to evaluate the ability
to extinguish fires and assess damage to powered equipment, paper records, and electronic data storage media. It is
likely that water misting could replace Halon 1301 in many fixed installations, although this remains to be
demonstrated.
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Low-Residue Particulate (LRP)
The use of dry chemical agents for extinguishing fires has been known for many years. Such agents arc at
least as effective as halons in suppressing fires and explosions in many applications. However, they may cause
unacceptable levels of secondary damage, especially to electronic components and moving parts, and their use
obscures vision. In spite of their high-effectiveness-to-weight ratios, the collateral damage, lack of uniform delivery,
and an inability to extend inertion (explosion or fire) have caused dry chemical agents to be rejected for many
applications. An area of concern when using LRP is the long-term health effect from acute inhalation of fine
particles (less then 10 um), This area is not addressed here, but must be accounted for as results become known.
Some recent research (3) indicates that fine particulate aerosols could be effective in fire suppression while
eliminating some of the disadvantages caused by larger dry chemical particles. The studies were on pyrotechnically
generated aerosols (PGA) that produce a fine particle by reaction (combustion) between an oxidant and a reductant.
The research also indicates that fine particles might be generated in-situ by chemical reaction in a spray nozzle or
through evaporation of solution mists. The use of fine particulate technology takes advantage of the well established
fire suppression capabilities of dry chemicals, with potentially reduced or eliminated collateral damage normally
associated with the use of traditional dry chemicals or powders. Additionally, using a fine particulate may offer the
ability to distribute a particulate cloud uniformly throughout a complex space and, if the particle size is small
enough, the particles may remain suspended in the protected space for times on the order of tens of minutes. These
suspension times could allow fine particles to act as "total-flood agents," yielding significant advantages over present
dry chemical systems and, potentially, some halon systems.
LRP encompasses propellant-generated solid particulates (PGSP) and PGA. Propellant technology (4)
propels fine powders into a fire suppression space via high pressure gases or pyrotechnic combustion, e.g.. rocket
propellants. This technology requires grinding of dry chemical powders, addition of flow promoting and anti-caking
ingredients, and development of delivery systems where clogging and oxidizer/fuel ratio considerations regarding
combustion have been taken into account. Experience in both fire and ordnance technology is required in designing
specifications for fire extinguishing systems.
The use of PGA originated in the late 1980s in the Soviet Union (5). The systems utilize a chemical
reaction to produce ultra-fine particles from combustion products of an oxidant and a reductant. In principle, the
resultant aerosol is distributed through the protected volume at a concentration sufficient to cause chemical inhibition
of the fire chain reaction and gas-phase cooling, hence fire extinguishment. There is some debate over the
proportion of the suppression mechanism due to chemical inhibition of the fire chain reaction versus gas phase
cooling. Although chemical particulates, at lower temperatures, can act as catalysts to recombine fire chain
propagators to give chemical inhibition effectively, solid chemical particulates may also decompose in the flames to
produce inhibiting species such as alkali hydroxides. For aerosol particles on the order of lfim in diameter, the
residence time required to produce the reactive species is short, and the diffusion of the small particle will tend to
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maintain its availability in the flame. Alternatively, the mechanism of solid particulates for gas-phase cooling is well
known and involves specific heat, fusion, vaporization, and decomposition. With small particles, depending on the
chemical composition, a sizable increase in extinguishing effectiveness is achieved and can be explained by flame
heat removal. Extensive studies for dry chemicals and powders have been carried out by Hughes Associates (6-8).
LRP technology, particularly PGA, is being pursued by several groups with much of the formulation work
being proprietary. Ongoing work includes efforts by Spring and Ball (9), Kibcrt ct al. (10), Harrison (4). Andreev et
al. (5). and Spectronix/Ansul (11).
PROJECT REQUIREMENTS AND DELIVERABLES
Task 1 - Assessment of Available Information on Alternative Protection Methods
Information on WM and LRP systems for fire protection was collected and evaluated. The search included
both U.S. and foreign literature, direct contact with researchers with experience in these areas, and inspection visits
to laboratories and field units where research was being conducted. The review is more inclusive than a standard
literature review. It was recognized that some of the information regarding WM and LRP is proprietary and/or may
not be accessible, since much of the work for governmental agencies was recent and had not been cleared for
publication. From the results of this information search, an assessment of the state-of-the-art for WM and LRP
systems with regard to fire protection has been carried out. Based on this evaluation, WM was selected as the most
promising system.
Task 2 - Experimental Program and Fire Suppression System
Based on the findings in Task 1, an experimental program to develop a WMS was planned arid conducted.
The experimental program was divided into two phases. In the first phase, a laboratory-scale experimental study was
conducted to determine basic parameters needed for developing the fire suppression system. The experimental
program included development of needed basic scientific data, engineering development and evaluation of individual
components of the fire suppression system, and evaluation of the overall effectiveness of the system in suppressing
fires in laboratory-scale experiments. As part of this effort, equipment development experiments were conducted to
select and optimize the components of the WMS.
The second phase of the experimental program consisted of room-scale experiments using the information
obtained from the laboratory-scale experiments to optimize the selection of equipment and operating parameters to
determine the overall effectiveness of the fire suppression system in actual use. Assessments were made of the
system's ability to suppress fire, protect against reignition and/or explosion, and to prevent damage to powered
equipment, paper records, and electronic data storage contained in the room.
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Task 3 - Engineering and Cost Evaluation of WM System
Three different applications of traditional halon fire suppression systems were selected. Determination of
how these halon systems could be replaced with a WMS were established. Information was sufficient to compare the
halon alternative system and included the following:
1. General design and layout, for the three systems.
2. Estimated capital and operating costs for the systems.
3. Assessment of the effectiveness of the systems' ability to Suppress fires and protect against explosion.
4. Assessment of the systems' ability to avoid damage to contents of (he space being protected.
This report provides details on the three tasks performed during this study.
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SECTION 2
CONCLUSIONS
The initial task of this project was to conduct a thorough technology review of the available information on
non-halon alternative fire protection systems. Of particular interest were LRP and WM fire suppression systems.
The technology reviews were to lay the foundation for an assessment of the state-of-the-art with regard to these
potential fire suppression technologies. Based on the results of the assessment, one of the technologies—water
misting—was selected, further developed, and a cost comparison was made against equivalent halon systems to
determine whether the chosen technology could be a cost effective replacement for halon in certain applications.
LRP fire suppression technology, particularly PGA, is at a developmental level. The research is centered
on development of formulations, determination of concentrations required to extinguish Class A and Class B fires,
documentation of acute toxicity of the aerosols generated, and development of generator systems. While the
potential for success of LRP fire suppression technology is encouraging, its development is still in its infancy.
Considerable work would be required to bring LRP on line as a new application or as a replacement for halon in
certain applications.
Water mist fire suppression technology is further along in its development, since it has drawn on the broad
base of hardware and theoretical knowledge developed for controlling air pollution aerosols, industrial scrubbing,
humidifying, air cooling, dust suppression, foam control, moistening, and water sprinkler fire suppression. At
present, at least 17 water mist system (WMS) technologies are available or are under development by different
manufacturers. Additionally, the potential suppliers of nozzles and systems greatly exceed this number should this
area of application expand.
In spite of the progress made with WMSs to date, their overall extinguishment efficiencies are still
significantly less than that of Halon 1301 systems. Work is needed to optimize WM characteristics and to test WMs
suppression and extinguishment limits. Based on the evaluation of their current stage of development and fire
suppression potential, WM technologies were chosen for development, testing and economic review.
Following the technology review of the state-of-the-art, an experimental program for evaluating WM
systems was developed, which included laboratory-scale experimental studies, equipment optimization studies, and
room-scale confirmation testing.
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The significant findings from the laboratory-scale experiments are that the lower effective limit of fire
extinguishment, that is the "critical concentration," for extinguishing n-heptane telltales, i.e., a 5-cm diameter cup
filled with water and 10-inI. n-heptane, (representing difficult to extinguish incipient fires) with a WM fire
suppression system appears to be 0.60 L/min-m2. Increasing water fluxes above 0.6 L/min-m2 do not significantly
decrease extinguishment times in proportion to total water usage. While water flux levels below this range are able
to extinguish the telltales, the extinguishment times became longer and more erratic. Extinguishment times for water
fluxes between 0.025 and 0.60 L/min-nr show standard deviations on the order of their extinguishment times.
Pooling the variances and plolling them against median extinguishment time for those extinguishment tests indicate
that the extinguishment times at these water flux levels follow a Gaussian distribution. Water fluxes below 0.025
L/min-m2 were not able to extinguish the fires.
Crowding the nozzles so as to increase the water flux decreases the fire extinguishment effectiveness, at
least for heptane fires. It is proposed that at higher concentrations, the W\1 coalesces into larger drops, which then
fall straight down and do not interact with the flame or, if above the flame, then fall through the flame. However, at
lower concentrations, the smaller drops, in addition to falling into the lire, can be swept into the side of the fire from
a greater (relative) distance, thereby aiding in extinguishing the fire by horizontal flame penetration and cooling at
the flame/fuel interface.
Based on the results of the laboratory-scale tests, a prototype operational system to generate and distribute
water mists over a larger volume (room-scale) was developed and tested at the NMliRl Intermediate Field-Scale site.
To provide effective fire suppression for an entire room with a WMS, the nozzle spacing was designed to yield a
uniform coverage of water flux over the entire protected space. For nozzles having a small circular spray pattern, the
most efficient design was a rhombohedral patterned array. Proof-of-concept testing for the WM system at the room-
scale level was based on a ceiling system designed as a rhombohedral array with a nozzle spacing of 40.6 + 5 cm,
i.e., adjustments were made for a best fit array within these parameters.
Flow rate testing of Baumac MX-8 nozzles indicated a water tlux of 0.467 L/min-m2 at 3.45 MPa for the
prototype operational system. Increasing the operating pressure to 6.90 MPa increases the water flow by 62 percent,
which yields a water flux of 0.76 L/min-m2. While the water flux designed for the WMS is below the critical
concentration of 0.6 L/min-m2, the system's capacity allows an increase in water flux to levels beyond the critical
concentration thereby providing a direct comparison to the laboratory-scale experiments.
Room-scale experiments demonstrate that scale-up from the laboratory is straightforward. At a water flux
level of 0.46 L/min-m2, the WMS is capable of extinguishing all unobstructed (open to the WM from all sides),
partially obstructed (open to WM from the top only), and fully obstructed (WM entry through vents in the cabinet
only) Class A and 13 fires. Increasing the water flux to 0.76 L/min-m2 shows that water usage increases at a greater
rate than does the decrease in extinguishment time. Significant findings from the room-scale testing are: (1) with
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continuous WMS operation at a water flux of 0.46 L/min-m2, the WM can neither inert the space nor stop reignition
of the hydrocarbon pool fire; (2) upon reignition, the WM can repeatedly reextinguish the fire; and (3) fires can be
extinguished without collateral damage to books, papers, and energized electrical (computer) systems.
The Task 3 requirement of this project was a direct system life-cycle cost comparison of the three present
halon applications and the equivalent WMS developed in Task 2. Due to uncertainties in the requirements of the
National Fire Protection Association (NFPA) Standard 750 on WM fire protection system installation, operation, and
testing procedures, the marketer of the nozzles tested was unwilling to give final costs. To complete Task 3 of the
project, three generalized WM systems were considered where enough information was available to complete an
economic analysis. The engineering design and cost of WMSs indicate a high-end cost estimate of $90 to $15Q/m'
across a range of technologies. For low-pressure, water-only mist systems, this cost could be reduced to below
$30/nr'. It is expected that the cost of WMSs will decrease over lime as additional competitors enter the market and
R&D costs are recovered. Given the high cost of available Halon 1301 (approximately $50/kg), halon systems now
average $125/m'\ WMSs appear to be cost competitive with Halon 1301 in many applications.
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SECTION 3
R F.COMMFNDATIONS
Since the inception of this program, industry has been active in developing WMSs. Part of the development
of these systems has been the drafting of NFPA Standard 750. Additionally, NFPA in conjunction with Underwriters
Laboratories (UL) and Factory Mutual (FM) is continuing development of testing and listing criteria for WM tire
suppression systems.
Since industry has an incentive to develop and market WMSs, the recommendations on future work are
directed toward developing systems and knowledge that will aid the entire fire suppression technology field and not a
single manufacturer. An area that needs additional study, so as to further the development and commercialization of
the technology, is WM droplet interactions after production within or from a nozzle. At present, there is no agreed
upon method for measuring these WM droplets in order to develop standards. Additionally, the interaction and
coalescing of WM droplets after they exit the nozzle and the horizontal transport criteria, nozzle spacing, and
mapping of si/e distribution and concentration in three dimensions below the nozzles cannot be easily done or
modeled at this time. Overcoming these difficulties will enhance the potential use and application of WM fire
suppression systems.
Another area needing further work should address the difficulty of WM to travel around corners or
obstacles. The development of an aerosol test chamber and a Fraunhofer instrument was stopped during this project
when it was determined that insufficient WM was entering the fire test zones despite the use of intake and exhaust
fans. The limitations in penetrating complex spaces and flowing around corners, given the droplet sizes and size
distributions found in the nozzles tested, may keep WMSs from fully replacing halon in total-flood systems. As a
result of these limitations, WMSs must be custom tailored and tested for the individual space to be protected, at least
for the near future.
The questions that arise are the extent of the interaction between individual nozzles and its dependence
upon nozzle spacing and the subsequent effect on drop size distribution. Additionally, what is the droplet size range
that will allow significant amounts of WM to flow around obstacles in sufficient concentration to extinguish fires?
These questions have an even greater impact on the drop size distribution of cluster nozzles, which multiple
manufacturers are now investigating.
A recommended follow-up project is one that would (1) determine and map the interaction of the WM with
distance from the nozzle, (2) determine and map the interaction of WM generated by separate nozzles and/or orifices
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in cluster nozzles and (3) determine the dependence upon noz/le or orifice spacing and how pressure affects this
dependence. The project goals would be to determine (1) the extent of any interaction between the nozzles with
regard to nozzle spacing; (2) how any of these interactions affect the drop size distribution; (3) the effect of the
system's operating pressure on the dependence noted above; and (4) the effect upon the drop size distribution
downstream of the nozzle. The results obtained would enable industry and researchers to improve knowledge of and
potential for modeling WM interactions to determine the effect of nozzle and orifice spacing and pressure on system
performance. This knowledge would aid in designing WMS and bringing these, systems to market in a timely and
cost-effective manner.
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SECTION 4
PROJECT DESCRIPTION
The technical approach of the project was tailored to assess the appropriateness of WM or low-residue
particulate (LRP) systems as replacements for halon-bascd extinguishment systems in specific applications. The
project consisted of three tasks: an information assessment (Task 1), an experimental program (Task 2), and an
engineering and cost evaluation (Task 3). Each of these tasks is discussed below.
TASK 1: ASSESSMENT OF AVAILABLE INFORMATION ON ALTERNATIVE PROTECTION METHODS
A thorough technology review of WM and LRP systems was conducted. This task began with the
considerable information already available in the Center for Global Environmental Technologies/New Mexico
Engineering Research Institute (CCF.T/NMERI) and Hughes Associates, Inc. (HAI) libraries. In addition, on-line
databases were used. To supplement the technical review, personal contacts within the technical community were
utilized when information could not be collected by other means.
The water misting review focused on (1) the production of fine droplets; (2) measurement of fine droplet
si/es; (3) types of nozzles (e.g., dual-fluid, high-pressure, etc.); (4) interactions of water droplets with fire (including
flame/plume penetration, evaporation, and transportation phenomena): (5) damage to equipment, particularly
electronic circuits, by water mists: and (6) systems presently under investigation and/or being tested in the field.
Little information has been reported in the open literature on LRP, while other information is proprietary.
For this reason, direct contact with the companies and researchers in this field was important. Among the existing
contacts utilized were the All-Russian Research Institute for Fire Protection in Russia, Spcc-trex in Israel, Fire and
Safety International in the United Kingdom, and Walter Kidde Aerospace in the U.S. The LRP review focused on
(1) a survey of present compounds and possible suppression mechanisms, (2) quantifying the performance and
qualities of existing compounds, (3) measurement of particulate size, (4) interaction of particulates with tire, and
(5) damage to electronic equipment by the particulates.
Following the technology review, the project team assessed the state-of-the-art for WM and LRP fire
suppression systems, taking into consideration the stage, of development, engineering design requirements, operation,
maintenance, overall performance potential, and potential uses of these fire suppression systems. The project team
then proposed that water misting technology development be investigated in Tasks 2 and 3.
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TASK 2: EXPERIMENTAL TEST PROGRAM
Following this technology review the project team, in collaboration with HAI, developed an experimental
program for evaluating the WMS. The experimental program included laboratory-scale experimental studies,
equipment optimization studies, and room-size confirmation testing.
A review of various particle/droplet size and size distribution methods was carried out to determine the
most appropriate system for measuring aerosol clouds. Based on the system chosen, a test apparatus was designed
and constructed for evaluating aerosol clouds and developing design requirements for fire suppression systems.
Laboratory- and room-scale experiments were conducted specifically to determine (1) extinguishment efficiency.
(2) effect of droplet size and concentration on fire suppression, (3) droplet lifetime and droplet suspension lifetime,
and (4) inertion efficiency. Room-scale extinguishment was tested for both Class A (cellulosic) and Class B (liquid
hydrocarbon fuel) fires.
Previous experiments showed that the fire suppression efficiency of LRP could be satisfactorily tested at a
laboratory-scale for both Class A and B fires using the NMERI Laboratory Extinguishment and Emission Test
Chamber (LEETC); however, this apparatus is not well suited for WM. A larger apparatus was needed to measure
the effectiveness of water misting, since evidence in the literature and previous limited experimentation with dual-
fluid nozzles indicated that misting system discharge can extinguish flames by discharge force alone. For these
reasons, the apparatus in Figure 1 was constructed. This apparatus allowed the WM to be discharged into a large
volume and then transported past a flame. Of particular importance was that the size distribution and concentration
could be measured in the vicinity of the flame. Unfortunately, during operation of the aerosol test chamber (A'l'C), it
was found that the air flow required to convey sufficient WM to the fires in the measurement zones was only 10
percent less then the air flow required to blow out the fires. An alternative method was then developed using the
Malvern and Fraunhofer instruments and the water spray chamber of the ATC to conduct the experiments listed in
the preceding paragraph . Following this phase of laboratory-scale testing, equipment development studies
determined nozzle placement and hardware required for WM delivery.
Finally, room-scale testing was conducted with the system developed on both Class A and B fires in the
NMERI Field-Scale Test Chamber (FSTC). Assessments were conducted of the system's ability to suppress fire,
protect against reignition or inert the protected space, and prevent damage to powered equipment, paper records, and
electronic data storage media contained in the room. In most instances, halon systems cause (or result in) virtually
no damage to room contents in the absence of a fire of sufficient size to cause halon breakdown. Some work
indicates that water causes little damage to electronic equipment (but significant damage to books and other paper
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Electronic Instruments
Temperature
Moisture
Water
Nozzle
To Air Pump
Optical Instruments
Droplet Size
Droplet Concentration
Air/Water Mist
Pump
Sump
Figure 1. Experimental apparatus for aerosol fire suppressant evaluation.
items), if the equipment is dried immediately and is shut down prior to its contact with water. As part of this testing,
operating (energized) electronic computers were placed in the chamber during the fire and subsequent WM
discharge. Additionally, during the room-scale fire extinguishment testing, hooks and newspapers were exposed to
both the fire and the WM discharge. Upon extinguishment of the fires, the operating personal computers, books, and
newspapers were inspected for water and fire damage. Without being cleaned, the computers were then stored under
humid conditions and checked for damage. In some cases, damage may not show up for a period of days to months.
TASK 3: ENGINEERING AND COST EVALUATION OF A WATER MIST SYSTEM
Initially, the system developed in Tasks 1 and 2 was to be compared to traditional halon tire suppression
systems for three different applications. Since the NFPA is now drafting a standard (NFPA 750) for major WMS
equipment as well as important design, installation, and inspection test and maintenance considerations and
requirements, manufacturers were unwilling to share cost data until they could develop system pricing data. To
complete Task 3, conceptual (general) design and layout drawings for three different WMS applications were
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developed for fire scenarios now using halon fire suppression systems. Systems were chosen where enough
information was available to complete the econometric analysis.
Estimated capital costs and operating costs were determined for three types of hazards over a range of
protected space variables including protected volume, ceiling height, subenclosures, ventilation control requirements,
compartment leakage requirements and type, cost, and sensitivity of detection hardware. The impact of the size of
the protected volume or hazard on capital and generating costs for halon and WMSs was developed. In general, the
design rules, equipment specifications, and other essential information followed the requirements provided in NFPA
12A (12) and proposed NFPA 750 standards. Since critical aspects of fire protection systems are availability and
reliability, hardware that is currently UL/l-'M approved was considered where possible. Estimates of the proposed
system designs were developed and related to existing halon system performance.
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TASK 1:
SECTION 5
ASSESSMENT OF AVAILABLE INFORMATION ON
ALTERNATIVE PROTECTION METHODS
REVIEW OF WATER MIST FIRE SUPPRESSION TECHNOLOGY
Introduction
Water mist fire suppression systems have been studied for at least 50 years. Although no practical or
commercially demonstrated systems evolved until recently, the basis for the use of fine liquid water droplets for gas-
phase fire suppression is relatively old. Recent interest in WM technology is motivated by two events. (I) The need
for lightweight, replacement sprinkler systems on commercial ships, driven by International Maritime Organization
(IMO) regulations requiring retrofit of commercial marine vessels, gives immediate impetus to the development of
low water demand, high efficiency, mist systems to replace sprinkler systems. (2) The phase out of halons and the
search for alternative technologies that preserve all or most of the benefits of a clean total-flood agent, without
adverse environmental impact, give further impetus to this R&D effort.
Although WMSs as replacements for shipboard sprinkler systems are relatively well developed and
commercialized, the use of WM as a Halon 1301 total-flood replacement agent is in its infancy.
Many WMSs are commercially available or in development. WM relies on relatively small (less than
200 um) droplet sprays to extinguish fires. In theory, the small drops allow the mist to move around obstructions
and extinguish fires, a characteristic of a total-flood gas. The mechanisms of extinguishment include the following:
1. Gas phase cooling Hike a total-flood "inert" gas)
2. Oxygen depletion by steam expansion
3. Wetting of surfaces
Water mist systems have attracted great interest for a number of reasons. The following are some of the
perceived advantages of WMSs:
1. Inexpensive
2. Non-toxic and environmentally friendly
3. Capable of suppressing flammable liquid pool and spray fires
4. Low water requirements (water quantities are a tenth or lower than sprinklers) resulting in reduced
collateral damage
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5. Effective against obstructed or enclosed fires, similar to a gaseous total flooding system
6. Electrically non-conductive (pure water)
7. Application as inerting or explosion suppression systems
Some of the potential benefits, such as the capability to suppress flammable liquid pool and spray fires at
lower water usage, have also been demonstrated.
Background
The efficacy of WMSs has been demonstrated in a wide range of applications and by numerous
experimental programs. These applications include Class B spray and pool fires (13-16), aircraft cabins (17-19),
shipboard machinery and engine room spaces (20-25), shipboard accommodation spaces (26), and computer and
electronics applications (18, 27).
To summarize these experimental efforts, the efficacy of a particular WMS is strongly dependent on the
ability not only to generate sufficiently small droplet sizes but to distribute critical concentrations of droplets
throughout the compartment (16, 28. 29). It is worth remarking that a widely accepted critical concentration of water
droplets required to extinguish a fire has yet to be determined. Factors that contribute lo the distribution of this
critical concentration of WM throughout the compartment consist of droplet size, velocity, spray pattern geometry as
well as the momentum and mixing characteristics of the spray jet, and the geometry and other characteristics of the
protected area. Hence, WM must be evaluated in the context of the total system, not just the extinguishing agent.
It is also apparent that WMS, when evaluated for fire extinguishment capability as opposed to the easier
task of fire suppression, will he very sensitive to the features of the area being protected. Consequently, it is
essential to develop worst-case fire scenarios and hazard geometries to evaluate fire extinguishment capability.
Theoretical Considerations
Overview —
There is no current theoretical basis for designing the optimum drop size and velocity distribution, spray
momentum, distribution pattern, and other important WMS parameters. This is, of course, quite analogous to the
lack of a theoretical basis for nozzle design for total-flood gaseous, conventional sprinkler, and water spray systems.
Therefore, a brief discussion of general design considerations is warranted.
The major difficulties with the WMS are those associated with design and engineering. These problems
arise from the need to generate, distribute, and maintain an adequate concentration of the proper size drops
throughout the compartment while gravity and agent deposition losses on surfaces deplete or reduce the
concentration, as outlined below:
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I. Critical concentration production
a. Small drop production parameters
b. Distribution and mixing parameters
2. I.oss mechanisms
a. Plate losses (fallout due to gravity, drops impacting walls and obstructions)
b. Vent losses (losses through vents primarily due to drops being carried out in the hot gas layer)
c. Evaporation losses (due to both hot gas layer and plume penetration)
Limiting Flame Temperature Basis —
There has been extensive work, both experimental and theoretical, on predicting critical adiabatic flame
temperatures, i.e., the minimum (limiting) temperature below which the flame will not propagate. Typical values for
this temperature fall within the range between 1600-1900 K depending 011 the fuel. A simplified analysis of the
amount of water required to lower the flame temperature from its initial (uninhibited) value to the lower limiting
value for a propane flame is shown in Figure 2. The calculation has been simplified in two ways. First, (he
combustion reaction occurs at stoichiometric ratios of air and propane. Second, the calculation assumes a drop is
evaporated completely and leaves the plume at the calculated plume temperature. The initial calculation was
conducted on a molecular basis and then converted into units easily related to standard hardware configuration
parameters. As shown in Figure 2, the theoretical amount of water required to reduce the flame temperature to the
limiting value is between 0.15 to U.25 L/m3 and can be termed the critical concentration required to extinguish the
flame. The actual concentration required may be less than this amount, due to the simplifications discussed.
According to Holmstedt (30). there are two possible methods by which a water spray may extinguish a fire:
cooling of the fuel and extinction of the flame. Holmstedt states that cooling of the fuel is best performed by large
drop sizes, and extinction of the flame is best obtained by small drop sizes. The relative importance of these
methods and the corresponding drop size desired varies depending on the space and/or chemicals being protected.
The major factors that determine the ability of a WM to extinguish a diffusion flame are heat absorption per
unit volume and droplet transport to all parts of the flame.
17
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Water Cone, in Air (L/ms)
2200
2000 -
1800 -
Limiting Flanle
Temperatures
Critical
Concentrations :::
Q
i—
D
2
0
Q-
E
|2
0
E
«5
LL
O
ro
-Q
co
<
Water Cone, in Air (gal/1000ft3)
Figure 2. Simplified critical concentration analysis.
Many factors have to be overcome to develop effective WM suppression fully. The complex phenomena of
drop transport and evaporation from the nozzle to the flame include many variables. A model needs to be developed
that considers fire-induced flows, radiation from flames and hot gases, convective heat transfer, absorption and
scattering of radiation, induced flows due to mist/flame interaction (pressure reduction), and the nozzle's reliability
to deliver the required sprays on a consistent basis. Additionally, the drop size (mass) and distribution effects with
regard to heat of vaporization, specific heat, and thermal conductivity for the WM need to be developed and
incorporated into the model.
While most WMSs rely on droplet sprays of less than 200 (im to extinguish fires, there exists the potential
for WM to act as a true flooding agent if the mass median drop size is below approximately 20 urn. At this drop
size, the suppression efficiency of WM is twice that of Halon 1301 per unit weight. Before this becomes possible,
however, methods of controlling droplet transport must be developed.
The predominant variables contributing to the production of the critical concentration (mentioned above)
are water drop size and flow rates. Drop size plays an important role in estimating the required water flow rate as
well as in the production of a critical concentration of drops. Figure 3 shows both the terminal velocity, i.e., the
velocity at which the gravitational force equal the aerodynamic drag force, and 3-m fall times of droplets as a
function of drop size, i.e., the time it takes for individual drops of different sizes to fall 3 meters at terminal velocity.
As shown in this figure, drops under 50 (im begin to exhibit characteristics of a gas by the increase in fall time and
18
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Three-Meier
FaO Time
Terminal
Velocity
3 100
50
150
E
£
•m
0
0
1
>
0
c
E
1
200
100
Drop Size, jjm
Figure 3. Water droplet free-fall characteristics.
decrease in terminal velocity. Conversely, large drops fall faster resulting in greater fallout losses Water flux
densities (flow rate per unit area) vary significantly among experimental test programs. The values range from
1.5 L/min-m2 (from testing done at 1IA1) to as high as 10 L/min-m2. The significantly higher water flux densities
recommended by Gameiro (31) and Mawhinney (32) may be a function of poor critical concentration production
efficiency (e.g., greater losses due to a larger drop size, poor mixing).
Water mist systems are subject to loss mechanisms that affect their ability to maintain the required drop
concentration in an enclosure. The primary loss mechanism, plate loss (fallout due to gravity), presents a seemingly
insurmountable barrier for WMSs. In order for WM to behave like a gas, a system must produce a significant
amount of drops small enough to be affected almost solely by Brownian Motion. None of the current WMSs
produces significant concentrations in this low (< 0.1 |im) range.
Other loss mechanisms include vent losses which vary as a function of the size of the vent, the size of the
fire (which drives the flow through the vent), and the concentration of drops in a compartment. Additionally
evaporation losses are difficult to calculate or estimate. The evaporation of a drop is a function of its size, initial
temperature, velocity with respect to the surrounding gas, gas temperature around the drop, etc. This estimation is
currently beyond the scope of this report, but, assuming other variables are constant, the life of a spherical drop is
proportional to the square of its diameter.
19
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Mistine/Atomization Technology
During the past decade or so, there has been an expansion of the science and technology of the
transformation of bulk liquids into fine sprays (atomization). The primary contributors to this technology have been
the combustion industry (fuel spray atomization), the chemical industry (spray drying), and the power industry
(evaporative cooling). Using developments in these industries as a source, significant information relevant to WM
applications for fire suppression can be extracted from this technology base.
Atomized sprays may be produced in various ways. Basically, all that is needed is a high relative velocity
between the liquid to be atomized and the surrounding gas. Some atomizers accomplish this by discharging the
liquid at high velocity into a relatively slow-moving stream of gas. Notable examples include the various forms of
pressure atomizers. An alternative approach is to expose the relatively slow-moving liquid to a high-velocity
airstream. The latter method is generally known as dual-fluid, air-assisted, or airblast atomization. The following is
a list of current types of atomization technologies:
1. Single-fluid pressure
2. Dual-fluid
3. Impingement
4. Effervescent
5. Electrostatic
6. Ultrasonic
Two of these technologies are incorporated in WMSs currently under development and/or consideration:
single-fluid and dual-fluid systems. Single-fluid systems (pressure atomizers) utilize water stored or pumped at high
pressure (4 to 20 MPa) and spray nozzles containing relatively small orifice sizes. Dual-fluid systems use air,
nitrogen, or other gases (1 to 2 MPa) to atomize water at a nozzle. Both types of systems have been shown to be
effective fire suppression systems. A breakdown of current WMS technology into these two types of systems is
presented below:
1. Single-fluid Systems:
Description: The single-fluid system no/zle incorporates two atomization techniques—
pressure and simplex atomization. The fluid is transformed into a sheet through
a flow chamber/pin (simplex-like) before it is forced through the relatively small
orifice at high pressures (pressure-like).
Systems: Generic systems that utilize industrial specialty nozzles and proprietary systems
include Marioff, Ultra Fog, Baumac International. Kidde-Graviner, and Kidde-
Fenwal.
20
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References: Hill et al. (17,18), Turner (21), Arvindson and Ryderman (22),
Jackman et al. (33). Marttila (34), Marker (35), Spring et al. (36),
Hills cf al. (37).
2. Dual-fluid Systems:
Description: Dual-fluid system nozzles can be classified into two basic groups: air-assisted
and air-atomized. Currently, the only air-assisted misting technology is used by
Securiplex (BP). The remaining systems can be classified as air-atomized. Both
systems incorporate the same atomization mechanism, but to different extents.
The mechanism uses a gas (usually air) at high velocity to shear the water into
small droplets. Air-atomized nozzles use an order of magnitude more air to
produce an order of magnitude smaller drops than air-assisted nozzles.
Systems: Generic (water with air, nitrogen, trifluoromethane (CHF;). etc.) systems utilize
modified industrial spray nozzles. These generic technologies include systems
designed and developed by the Naval Research Council of Canada (NRCC) and
the Naval Research Laboratory (NRI.). Several proprietary systems also exist,
including Securiplex (BP), Kidde-Graviner, Kidde-Fenwal. and ADA
Technologies.
References: Papavergos (13), Butz and Carey (14), Cousin (16), Soja (24), Gameiro (31).
Mawhinney (32), Leonard (38), Wighus (39).
Both the single-fluid and dual-fluid systems have their advantages and disadvantages. These advantages
and disadvantages are listed as follows:
1. Sinule-fluid Systems
a. Advantages: Small space and low weight
1) No air compressor and gas storage requirements (i.e., cylinders)
2) Reduced amounts and size of piping
3) Simpler design
4) Ease of installation
5) Low overall installation and operating costs
b. Disadvantages: High pressure (possible physical safety hazard ?)
1) Pump or storage requirements
2) Potential clogging problems due to small orifice nozzles
21
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Dual-fluid Systems
a. Advantages: High drop momentum (blowout of the flame and better mixing)
1) Low water supply pressures
2) Large orifice sizes (less likely to clog)
3) Adjustable drop size to meet need
4) Substitution of gaseous halon alternatives or inert gases for air atomizing fluids
b. Disadvantages: Large space and weight
1) Air compressor and/or cylinder banks
2) Increased piping and piping size for gaseous fluid
3) Complex design (hydraulics) may require regulators on each nozzle
4) Dual installation
5) Increased compartment pressure during discharge
6) High overall installation and operating costs
Commercial W\1S Technology
There are currently at least 17 WMS technologies available or under development using either dual-fluid
(Nj/air and water) or single-fluid systems. Table 1 summarizes the current manufacturers of WMSs for fire
suppression use. Some of these manufacturers are still in the R&D phase with their particular hardware. The
following descriptions of the example systems are intended to give a sense of the wide range of system
characteristics.
Although some of the commercially-available systems have received limited acceptance from overseas
approval authorities for limited applications, the approval testing and standardization effort is just getting underway
in the United States. The newly formed NFPA Water Mist Fire Suppression Systems Committee faces not only the
task of developing performance criteria but also the problem of evaluating the systems' adaptability in numerous fire
protection applications. The committee has recently drafted an outline for the standardization of WM technology.
The intent of the committee was to have the specifications completed by early 1996.
The large number of commercial systems under development and the evolutionary nature of many of the
systems makes descriptions of all the systems infeasible. However, it is useful to review one of each of the major
types of systems. The system classifications which seem to be most useful in characterizing WMSs are listed in
Table 2.
-------
TABLE 1. WATER MIST HARDWARE MANUFACTURERS
Company
Country
ADA Technologies
Baumac International A MicroMist
BETE Fog
DAR CHEM
FS !/Kidde-G ravine r
GEC-Marconi Avionics
Ginge-Kerr (BP)
Grinnell AquaMist
GW Sprinkler
HTC
Kidde-Fenwal
Marioff Hi-fog
Microguard-Unifog
Securiplex (BP)
Semco
Spraying Systems Company
Uniter
U.S.A.
U.S.A.
U.S.A.
United Kingdom
United Kingdom
United Kingdom
United Kingdom, Denmark, Norway
U.S.A.
Denmark
Sweden
U.S.A.
Finland
Germany
Canada
U.S.A./Denmark
U.S.A.
Germany
TABLE 2. WATER MIST SYSTEM TYPES
System Type
Example
Single fluid, low pressure
Single fluid, high pressure, high spray momentum
Single fluid, high pressure, low spray momentum
Dual fluid, air assisted
Dual fluid, air atomized
Grinnell AquaMist
Microguard Unifog and Marioff Hi-fog
Baumac MicroMist
Securiplex Fire Scope 2000
No example is yet commercially available
23
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Grinnell Aquamist System —
Grinncll AquaMist is a low pressure system that operates in the range of 0.6 to 1.21 MPa. At 0.6 MPa, the
nominal nozzle flow rate is 11.5 L/min. The system's operation has been tested in the range of 0.4 to 3.0 MPa and
has been optimized for the 0.6 to 1.21 MPa range. The Grinnell System is almost identical to a standard automatic
sprinkler system in terms of system hardware and operating principles. The relatively low-pressure Grinnell System
trades off efficiency in producing small droplets (an advantage of high system pressure) against the cost and
commercial advantages of using standard hardware. A schematic representation of this system is shown in Figure 4.
System characteristics—
Nozzle design: The Grinnell System operates with two nozzle types, the AM5 and AM6. Both types are
automatically operated and differ only in the deflector design. All other nozzle components are identical. The two
nozzles have been designed to perform optimally at the 0.6 to 1.21 MPa operating pressure and the 11.5 L/min flow
rate previously described. Grinnell nozzles have been calculated to operate at a nominal K-factor* of 14.9 L/min-
MPal/J. The nozzles will deliver a Sauter mean drop size of 60 to 150 um depending on location in the spray. Spray
patterns and droplet size have been consistent in all tests in the normal operating range.
Details of the nozzle design are as follows. The heat sensitive element is a 3-mm bulb with a nominal response time
index (RTI) of 35 (m-s)l/2 and a nominal conductivity factor (C) of 0.65 (in/s)"2 (40). The temperature rating is
68 °C standard, with a minimum requirement of 30 "C above ambient for higher ambient temperatures. Each nozzle
is designed with a strainer having perforations of 2 mm for particle filtration, to avoid clogging the 2.7-mm diameter
orifice within the nozzle. The nozzle frame is manufactured using zinc-free resistant brass. The nozzle waterway
seal is spring-sealed on the interior and composed of a beryllium-nickel disc with Teflon gaskets on the exterior
edges. The seal ejection spring is stainless steel. All other components are fabricated from a salt water-resistant
phosphor bronze.
Pump requirements: The system will work under normal pipe flow conditions. Pumps are specified on a
case by-case application basis as with regular automatic sprinklers.
Performance tests-
Extensive testing has been performed to evaluate the suppression/extinguishment capabilities of the Grinnell
System for shipboard applications, e.g., cabins, corridors, and public areas up to 5.0 m in height (two decks). The
results of these fire tests, performed at the minimum specified design pressures, show that this system controlled,
suppressed, or extinguished the fire with reduced direct fire damage and relatively low ceiling gas temperatures.
* K-factor is the constant of proportionality relating flow to the square root of pressure.
24
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Detector
Nozzles
Pressure
Control
Valve
HX—
Pump
(Optional)
Annunciator
Panel
Alarm
Signal
Water
Supply
Figure 4. Schematic of a typical Grinnell AquaMist System (low pressure).
25
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Additional tests run on this system show that it possesses the potential capability to suppress or extinguish
concealed as well as exposed fires, arsonist fires, and residential fire scenarios involving combustible walls and
furnishings. Testing has only recently begun on machinery space/flammable liquid hazards. The Grinncll System
appears at this point to be a viable replacement for standard sprinkler systems. Its use as a total-flood replacement
agent in highly obstructed geometries (e.g., computer facilities) has not been evaluated.
Microguard Unifog System --
The Microguard System is a high pressure, single-fluid system that operates under the premise that the most
effective water droplet size for fighting fires is 20 to 50 ,um in diameter. The theory is that if droplet sizes are
constant in this range, then 1 L of water will provide 170 nr of cooling surface. With a Microguard's standard
nozzle flow capacity of 5.0 L/min at 10 MPa, this rate translates into a potential heat absorption of 188 kW. A
schematic representation of the system is shown in Figure 5.
nA"
-An
\ t X
Nozzles 0-
/ i \T
A A1
Detector
Programmable
System
Alarm
Signal
—,WS—
Pressure
Control
Valve
-CXJ-—
ain Pump "1
Jockey
Pump
Q
Main Pump
Breaktank
Water Supply
Breaktank
Water Supply
Water Supply
Figure 5. Schematic of a typical Microguard Unifog System.
26
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System characteristics-
Pumps: The system's water flow is controlled by a pump-drive system. All pumps arc designed on an
individual case basis. For shipboard applications, the normal procedure is to design for protection of the largest
protected space and include a factor of safety, which provides for the pump's capacity to fight three separate fires
simultaneously.
F.ach pump station consists of two electrically driven main pumps and a jockey pump. The jockey pump is
used to maintain a 1 -MPa pilot pressure within the piping system, in order to avoid water hammer effects when the
main pumps activate at 10 MPa. The main pumps are designed to maintain a pressure of 10 MPa independent of
water flow. As a backup, the jockey pump is designed to provide a water flow capacity equivalent to that of three
standard nozzles. The two main pumps are supplied by individual breaktanks sized to provide a water flow to the
largest protected space for a minimum discharge time of 5 min plus a time safety factor of 2.5 for a required
discharge time of 12.5 min.
Control and monitoring: For control and monitoring of the system, a control cabinet with a programmable
logic system is provided. This logic system, programmed by a personal computer (PC) or manually, will control
water flow to any pan of the system. Constant monitoring of the pumps, water flow, breaktanks. power supply, etc.
is also performed by the logic system, which also provides sounding signals for the varying modes (fire alarms and
system failures). The system is capable of integrating a variety of detection devices that may be used to actuate the
system or provide warning in the case of manually activated systems.
Nozzle characteristics: Microguard nozzles are designed to provide water droplets of 20 to 50 (irn in
diameter in a variety of designs. The nozzles are designed in two basic styles. Open area nozzles require four
outlets per nozzle while narrow area (i.e., corridor) ones require only two. Each nozzle is capable of protecting
15 m2. For spaces smaller than 15 m'\ heads are supplied with fusible links. As an added protection against outlet
orifice clogs, each nozzle is equipped with a microliter to filter particulates from the water. All nozzles are
produced in bronze or stainless steel.
Piping: The Microguard water distribution systems are made solely of stainless steel. The system is
exterior welded to reduce interior particle contamination within the pipe and to increase the piping strength. For
special circumstances, compression fittings are used when welding is not desirable or possible. The piping system is
tested at a minimum pressure of 15 MPa. All piping systems are designed on an individual case basis dependent on
water flow requirements, length and elevation considerations, and pressure losses.
27
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Performance testing-
Currently, testing and evaluation are being performed for many applications. Shipboard uses that fall into
this evaluation process are engine rooms with bilge and casing, pump rooms, cabins, and corridors. Public areas
such as restaurants and theaters are being evaluated for both shipboard and non-shipboard use. Transformers, power
plants, and other areas with computer/electronic equipment are also scheduled for testing and evaluation.
At this time, this system has been demonstrated to be effective as a sprinkler replacement system for
shipboard applications and for certain flammable/combustible liquids. Its effectiveness as a total-flood replacement
has not been evaluated.
Marioff Hi-fog™ System --
The Marioff System is designed to act as an alternative replacement to Halon 1301 and carbon dioxide.
With Halon 1301 being internationally phased out and carbon dioxide having potentially fatal effects on humans,
water is a viable alternative for total-flood applications. In such application as ships, the Marioff System provides a
lightweight alternative to conventional sprinkler systems. Both testing to date and multiple system installations have
shown that this system is a highly effective method of suppressing and extinguishing fires. The system has
demonstrated an ability to penetrate, plume gases, act as a cooling agent, and extinguish fires.
The Marioff provides droplet sizes with an average diameter of 60 |im, which has been the primary positive
factor behind Marioffs extensive work with shipboard installations.
System characteristics—
Supply system: The system is supplied by an array of one or more banks of pre-charged gas/water
accumulators. The accumulators are installed with electrically driven low-pressure water pumps and automatically
activated electric and pneumatic recharge pumps. The normal procedure is to design for protection against a worst
case 10-MW hydrocarbon fire. The accumulator design provides for 100 percent redundancy in a second bank, in
the case of an accidental release in a wrong or non-fire area. The system is functional with both saltwater and
freshwater.
The system accumulators are always loaded with water pressurized to 28 MPa. Check valves supplied in
the system heads retain water within the piping. Recharge pumps will automatically engage if the accumulator
pressure falls below 28 MPa and will recharge until that pressure is re-established. The recharge pump will recharge
sufficiently to allow the system to have a high pressure release every 3 min until deactivation of the system.
28
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Upon manual activation, low pressure pumps are activated, valves opened, and water is provided to all
system heads at 1.6 MPa. The intention (or aim) is that this will provide cooling for the pipework and discharge
heads prior to high-pressure release, which lasts approximately 45 see before decay. Low-pressure mist remains to
cool the space so that reignition does not occur.
Control and monitoring: The system can be manually or automatically actuated. Automatic actuation
devices include friable glass bulbs and heat or smoke detectors. Alarms are provided for all electrical and pump
malfunctions or failures. The monitoring system will act according to the situation. It also starts and stops pumps as
necessary. All segments of the system are fitted with a manual override.
Nozzle characteristics: Marioff Hi-fog™ nozzles are designed to provide water droplets of 60 urn in
diameter (average) in a variety of designs. The nozzles are designed in three basic styles: (1) The first contains four
outlets per nozzle and delivers 4.5 L/min at 28 MPa and 1.5 L/min at 1.6 MPa; (2) the second has a head that
contains three central outlets with nine surrounding outlets capable of delivering 20 L/min at 28 MPa and 7 L/min at
1.6 MPa; and the third has one central outlet surrounded by six perimeter outlets capable of delivering 8 L/min at
28 MPa and 2.5 L/min at 1.6 MPa. All nozzles are produced in either stainless steel or bronze.
Nozzle spacing varies with the ship hazard being addressed; however, normal spacing is approximately 3 m
between heads.
Piping: The Marioff water distribution systems are made solely of stainless steel conforming to American
Iron and Steel Institute (AISI) 304 or 316. The connections arc approved type Deutsche* Industry Norm (DIN)
2353. The piping system is installed to a minimum test pressure of 28 MPa. All piping systems are designed on an
individual case basis dependent on water flow requirements, length and elevation considerations, and pressure losses,
lhe systems are designed with a safety factor of 4:1 based on the minimum burst pressure.
Hi-fog™ sprinkler heads-
Marioff also supplies an alternative to conventional automatic sprinkler heads. The heads have a reduced
flow rate of 4.5 L/min and operate in a similar way to the conventional heads. The head is activated by a release
bulb. This head differs from the conventional one in that the bulb is protected by a metal cover with small holes
bored for heat flow to the bulb. When the bulb reaches its response temperature, it releases a valve spindle. The
main valve is released when a spring presses the spindle valve down, allowing water flow to enter the nozzle, and
releasing the water as a high-pressure (10-MPa) fog. The nozzle system is also available with an option of two heads
releasing water when only one bulb reaches the response temperature.
Performance testing: The Marioff System has undergone extensive testing in many areas and exists in
several variants, some explicitly designed to be used in total-flood replacement applications. Shipboard testing on
29
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cabin, corridor, public area, engine room, pump room, and bilge fires has shown that this system is very effective in
controlling, suppressing, and extinguishing fires in these applications.
Testing and evaluation have been performed to test the system's ability to suppress deep-seated fires (e.g.,
slow growth furniture fires), wood cribs, pool-type fire scenarios, and fires in large room areas and public areas.
Testing has proven that WM can be an effective alternative or replacement for automatic sprinkler systems.
However, insufficient testing has been performed to assess its capabilities against small, highly obstructed fire
sources.
Baumac International Micromist System --
Baumac International has developed the MicroMist System, a humidification/ evaporative cooling system
designed for use in fire protection applications; it is being marketed by Reliable Automatic Sprinkler Co. This
system differs from the Microguard and Marioff Hi-fog systems.
The Baumac System consists of a water pumping station and provides for built-in particle filtration of 5 (iin
in diameter. The primary distinguishing factor is that the delivery system is a 12.7-mm diameter, thin wall stainless
steel pipe with many low-flow nozzles. A patented nozzle installation process has been developed to minimize tube
and nozzle installation failures or leaks. It may be produced and installed with almost limitless arrays of nozzle
spacings and/or angles. The goal is to produce and evenly deliver a large quantity of small droplets over the
protected area.
System characteristics-
The Baumac System has been developed with four primary nozzle sizes: MX-8. MX-12, MX-15, and
MX-20. The number listed in the model description gives of the nozzle orifice diameter in thousandths of an inch.
Test series (41) have been performed with the following nozzle flow rales at 6.90 MPa:
MX-8 0.102 L/min
MX-12 0.212 L/min
MX-15 0.276 L/min
MX-20 0.329 L/min
Droplet sizes for the individual nozzles have been documented in extensive testing. The droplet diameters
range from 10 to 120 jj.ru. The smaller orifice heads tend to deliver a higher concentration in the range of 10 to
70 ,um, and the larger orifice outlets provide higher diameter droplets. An example of a typical nozzle layout scheme
is shown in Figure 6.
30
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W 4.25m H
o-
o
o
o
o
o
o
o
ro
o
o
o
o
o
o
o
o
o
o
o
o
o
o
> Nozzles Nozzles
o
o
o
o
o
o
<>
99999999
Heptane
Cup
o
o
o
o
o
a
a
1
^ j
1.2
1
2m
r
*_1 -22 m
a
o
o
o
o
o
=4
* Exhaust |
Bathroom
Exhaust
Fan
(0 02 m3/s)
l«—- 1.75 m ~
«Q.77mH«— 1.73 m —~
1 t-0.05x 0.10 m
II
V/15°
0.1S m O.C.
I «V|
0.75m
0.43m
Figure 6. Schematic of a Baumac MicroMist System nozzle array for subfloor test scenario.
31
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Performance testing—
Performance testing is currently ongoing to characterize the nozzle(s) and their operating parameters. Tests
have been run for a series of applications such as subfloors, computer rooms, computer cabinets, communications
switchgear, public areas, and residential scenarios. Test results to date indicate that the Baumac System comes close
to behaving like a total-flood gas system due, primarily, to small water drop sizes and close nozzle spacing, which
minimizes the impact of obstructions.
Securiplex Fire-Scope 2000 System -
General system descriotion-
The Securiplex Fire-Scope 2000 system is an air pressure-driven system. The driver is a 65-L air cylinder
with a storage pressure of 15 MPa. The available water storage tanks have capacities of 200,400, and 600 L. One-
air cylinder is required for each 200 L of water supply.
The delivery system is controlled by a series of regulators and control valves to assure proper water delivery
and functionality of the system. The system may be actuated either manually or electronically and may be integrated
with detection devices for increased fire protection effectiveness.
No/zlcs: Securiplex uses two main dual-fluid nozzle designs. The designs consist of nozzles that deliver a
flow of 10 L/min or 20 L/min. The two heads are designed to operate at a pressure of 0.5 MPa. The spray angles of
the heads are 45, 60, and 90 degrees depending on the fire suppression requirements of the protected area.
In total-flood applications, the protection is approximately 5 m3 per nozzle for the 10 L/min nozzle and
approximately 10 in3 per nozzle for the 20 L/min nozzle. These quantities are subject to the room configuration and
fire risk assessment. The protection values are based on rooms with ceiling heights not exceeding 3.7 m. For rooms
exceeding this height, provisions for additional wall mounted heads must be included. The heads are manufactured
in bronze.
Piping: Piping for the Fire-Scope 2000 System is American Society for Testing and Materials (ASTM)
A-179 steel tubing or galvanized steel pipe, schedule 10 or better, for conventional building applications.
Other applications—
Securiplex, in conjunction with its Danish affiliate (Ginge-Kerr A.S.), is in the process of developing,
testing, and evaluating systems for shipboard and gas turbine applications. The system under consideration is known
as the Fine Water Spray (FWS) system.
32
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Tile basic concept of this system is the same as that for a conventional building system. The water is stored
in a tank and is expelled by a gas, in this case nitrogen. The concept of dual-fluid delivery nozzles is consistent with
the Securiplex Fire-Scope 2000 System. Nozzle delivery angles and flow rates also remain constant as with the
Securiplex Fire-Scope 2000 System; however, one factor in the shipboard applications does change. The WM is
delivered at lower pressures, which allows longer cooling periods in applications such as machinery or engine rooms.
Performance testing-
Securiplex and Ginge-Kerr have performed extensive testing on various applications. A number of te.sts
have been performed in simulated ship's engine room configurations. The testing shows that oil spray and pool fuel
fire conditions can be successfully controlled, suppressed, or extinguished on a consistent basis.
Securiplex has conducted tests in a mock-up of a gas turbine hood using water spray as the fire suppressant.
The tests were performed in two different scales. The first was a 30-m3 test enclosure used to develop the
characteristics for the full-scale 70-rrr enclosure. The initial work was to identify the extinguishment characteristics
of various British Petroleum-developed nozzles and to determine the efficiency of Ginge-Kerr's fire suppression
system. The suppression system consisted of dual-fluid nozzles using air and water at 0.5 MPa. The nozzles
produced a high velocity, small droplet WM.
Follow-on experiments have been performed to lest and evaluate the efficiency of FWS nozzles in fighting
various turbine hood fire scenarios in a full-scale test enclosure. The enclosure consisted of an engine mock-up used
to simulate hot engine surfaces, insulation mats, and piping, which are present in a real engine hood. Diesel fuel
pool and spray fires and diesel-soaked insulation mat fires were subjected to different air flow, WM nozzle position,
and fuel flow conditions.
The tests covered a wide range of possibilities. Large under-ventilated gas, pool, and oil spray fires were
extinguished with the addition of small amounts of water. This was due to near self-extinguishment caused by
oxygen deficiency in the hood.
The large well-ventilated, gas, pool, and oil spray fires, as well as those containing an oil spray hitting hot
metal surfaces, had varying results. The fires were extinguished in the cases where the WM droplets were able to
reach the base of the fire but not when the droplets could not do so. The oil spray on the hot metal surfaces was
extinguished consistently when the water spray system covered the full area over which the oil spray hit the metal
surface, even in the cases when the metal surface temperature remained high.
It was found that 1 m1 (medium) well-ventilated pool fires, small pool fires (< 1 m2), and fires in oil-soaked
insulation mats were very difficult to extinguish. The droplets were unable to penetrate the fire to effectively
evaporate the water in the flame zone effectively or to reach the fire's base.
33
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The final test conditions, oil-soaked insulation mats with hot metal surfaces below the mat, were semi-
successful. The fires were extinguished successfully, but tended to reignite. Reignition can be curbed with sustained
addition of the WM to displace oxygen and cool the metal surface.
Similar testing was performed in a full-scale gas turbine enclosure. The main combustibles tested were
propane, diesel fuel, and lubricating oils. These tests showed consistent success in controlling, suppressing, or
extinguishing the fires. The Securiplex System is the first commercial WMS to undergo approval testing in the U.S.
for turbine enclosures.
Experimental Evaluation of Water Mist Systems
Overview -
The efficacy of the WMS has recently been demonstrated for a range of applications through experimental
programs. These applications include the following:
1. Class B spray and pool fires (13, 14, 15, 16)
2. Aircraft cabins (17, 18, 19)
3. Shipboard machinery and engine room spaces (20, 21, 22, 23, 24, 25)
4. Shipboard accommodation spaces (26)
5. Computer and electronics applications (18, 27)
In addition. Factory Mutual, Inc. (FM), has developed a proprietary test method for testing WM applications for
turbine generator enclosures.
These experimental efforts indicate that the efficacy of a particular WMS is strongly dependent on its ability
not only to generate sufficiently small droplet sizes but to distribute a critical concentration of droplets throughout
the protected enclosure (16, 28, 29); however, a widely accepted critical concentration of water droplets required to
extinguish a fire is yet to be determined. Factors expected to affect the critical concentration of WM throughout the
compartment include droplet size and velocity, spray pattern geometry, momentum and mixing characteristics of the
spray jet, and geometry and other characteristics of the protected area. This necessitates evaluation of WMSs for
specific applications.
Naval Research Laboratory —
Over 500 WMS tests have been conducted by the Naval Research Laboratory. Many of these tests were
part of an ongoing investigation into the use of WM as a halon alternative in machinery space applications for the
U.S. Navy (38). These tests include both generic systems utilizing modified industrial spray nozzles and
commercially available fire protection misting hardware. The systems tested cover the spectrum of available
34
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technologies including dual-fluid, fixed orifice; dual-fluid sheet/slit orifice; single-fluid, high-pressure multiple-
orifice heads; and single-fluid, high-pressure grid/matrix-type systems. It was not the intent of this investigation to
compare one system against another, hut rather to determine the capabilities and weaknesses of WM technologies.
The systems were evaluated in a 3 by 3 by 2.4-m compartment under a variety of fire conditions as shown in
Figure 7. These fire scenarios included both obstructed and unobstructed Class A wood crib fires and Class B spray
arid pool fires. Obstructions varied from "shielded from above using various size plates" to "shielded on two sides
and above." The average localized mist density, based on a combined total flow averaged over the entire
compartment floor area, ranged from 0.5 to 1.5 L/min-m2' which corresponds to a volumetric flux density of 0.2 to
0,6 L/min-m3. This flux density is approximately an order of magnitude less than for a conventional sprinkler
system. Higher flux densities are currently being evaluated.
Each system was evaluated in a variety of configurations to achieve optimum results. The firefighting
capabilities of these optimized systems varied only slightly for a given flux density. The results appear dependent on
the similarity in drop size distribution between the systems, with the mass mean diameter of drops measured as DVo ?
-75 f.tm ± 25 um. (The mass mean diameter, Dvo.s. is defined as the diameter of a drop such that 50 percent of the
total liquid volume/mass is in drops of a smaller diameter.) An overview of the fire performance of three selected
systems is shown in Table 3.
Some general observations on I he firefighting performance of the WMS derived from this effort are listed
below.
1. All of the systems evaluated were able to extinguish unobstructed fires on the floor of the compartment
with spray flux densities on the order of 1.0 L/min-m2.
2. Many fires located at higher elevations in the compartment were extinguished with the remaining fires
dramatically reduced in size.
3. Large fires are easier to extinguish than small fires due to the displacement of oxygen by the
evaporation and expansion of the WM to steam as well as higher plume entrainment rates associated
with larger fires.
4. The firefighting capabilities of the two-fluid systems were found to increase by substituting nitrogen
and other inert gases for air as the second fluid.
5. Obstructed fires become more difficult to extinguish with increased horizontal drop travel distance (i.e..
horizontal distance from the higher flux density region near the spray pattern to the fire source). Many
fires were extinguished with distances on the order of 0.3 m, but were not extinguished for greater
distances. Many of the highly obstructed fires, although not extinguished, were greatly reduced in size
by the presence of the WM.
35
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CORNER CONFIGURATION
2.4 m
rtrea
8 cm Dia
Fuels
Heptane &
Diesel
SPRAY FIRE CONFIGURATION
Spray Fire
Location
T* Fire Sizes \ ~
0.2,0.4,0.8, £
1.0 MW \
Fuels /
Heptane and \
Diesel J
2.4 m
3 m
3 m
CLASS A CONFIGURATION
wood Crib
Obstructed
Tight to
Corner
2.4 m
wood Crib
Unobstructed
Center of
Compartment
Fire Size
250 KW
PAN FIRE CONFIGURATION
Obstruction Platens)
0.3 x 0.3 m
OX x 0.6 m
1.2 x 1.2 m
Fires
6 cm Dia.
15 and 30 cm
Square Pans
Fuels
Heptane &
Oiesel
Standard
Block
Fir a Location
2.4 m
Figure 7. Test fire scenarios.
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TABLE 3. FIREFIGHTING OVERVIEW OF WATER MIST SYSTEMS: PROBABILITY
OF SUCCESS (%) AS A FUNCTION OF FIRE CONFIGURATION
Test configuration
Nozzle system
Generic
Marioff
Baumac
Modified Baumac
Dual-Fluid
45 nozzles
90 nozzles
Corner configuration
Floor
80
90
95
95
0.6 m
10
10
40
90
1.2 m
10
10
20
60
1.8 m
0
0
10
25
Pan fires
Unobstructed
85
90
97
98
Obstruction plates
0.3 m
15
25
40
75
0.6 m
0
10
10
40
1.2 m
0
0
0
10
Class A wood cribs
Center
80
80
90
95
Comer
10
10
10
10
Spray fires
98
95
92
90
Notes: The values in Table 3 represent the percentage of test fires extinguished for a given fire/system
configuration. Refer to Figure 7 for a better description of the fire scenarios. Class A wood crib
fires were evaluated using a 3-min discharge time.
The Baumac MicroMist™ and the Marioff Hi-fog™ systems represent the extremes of design philosophy
for single-fluid high-pressure WMSs. The latter relies on spray momentum for distribution and mixing of drops; the
former utilizes many nozzles, which produce small droplets with little spray momentum.
The Marioff Hi-fog System utilizes high-pressure water (10.3 to 20.7 MPa) supplied by pumps or nitrogen-
pressurized storage containers. Small-diameter (12.7-mm) seamless stainless steel tubing is used to feed the nozzles.
Marioff offers a variety of nozzle types and flow rates. The basic design is a four-nozzle head with a water flow of
approximately 3.8 L/min at 10.3 MPa. The heads are thermally actuated with quick-response glass bulbs. The major
feature of the Marioff nozzle is its bimodal droplet size distribution. The flow pattern is comprised of both large
(-100 |J.m) and small (<50 urn) drops. The large droplets provide spray momentum that assists in penetration and
mixing. Typical spacing is 11.1 to 13.9 m2 of protected area per nozzle head.
The Baumac International MicroMist System utilizes 6.9-MPa pressure water supplied by a pump. The
system is basically a length of seamless stainless steel tubing with small orifice nozzles located at 0.3- to 0.6-m
intervals along the pipe. The pipe can be located around the room perimeter or across the ceiling. Each nozzle has a
very low flow rate. Typically, the total flow rate is about 4.1 L/min-m2 into the space. Design variables include the
spacing and orientation of the individual nozzles and nozzle diameter, and the spacing of nozzle banks. The current
37
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system must be actuated by a detector or some external means, although it is possible to use a more traditional
thermal actuation mechanism. The Baumac System produces a large amount of very small droplets with almost no
momentum in the spray and is the system that most closely approximates a total flood system. This system
effectively extinguishes most unobstructed fires and demonstrates superior firefighting capabilities (superior to the
other systems tested) against the obstructed pan and corner fire scenarios. The extinguishment efficiencies are,
however, less than the gaseous halon alternative extinguishment efficiencies and do not provide true total flood
capabilities.
Dual-fluid systems (air atomized) use air at 0.2 to 0.7 MPa to atomize water supplied at 0.17 to 0.7 MPa.
The droplet size distribution can be varied across a wide range by changing the relative water-to-air flow rates, air
pressure, and nozzle, orifice design. Several of these types of systems are commercially available. They have been
shown to be very effective for local control of flammable liquid hazards.
V IT Testing (Technical Research Institute of Finland) -
Toumisarri (42) reviews an on-going project at the Fire Technology Laboratory of VTT. which started in
1991 and continued to the end of 1994. The project focuses on the water-use efficiency in post-flashover fire
suppression of compartment fires. The tests compared commercially available fire hose nozzles and high-pressure
fog nozzles.
The test room is a 2.4 m by 3.5 m enclosure with one ventilation opening. The fuel is eight wood cribs
ignited with heptane pools under the cribs. Fires are allowed to burn for 3.5 min to give a heat release rate of about
3.5 to 4.5 MW.
The results showed that the commercial nozzle, on average, attenuated the burning gases in about 8 sec with
11 L of water and fully extinguished the fires with 48 L of water. The mean drop size was 0.35 pm and the water
flow rate was 80 L/min.
The fog nozzle test results showed a drastic reduction in water used to attenuate the gases, which was also
accomplished in 8 sec with 2 L of water. With the water fog, the crib fires were not extinguished completely, as with
the commercial nozzles. The mean drop size for the fog nozzle was 0.1 Jim at a flow rate of 16 L/min.
Further studies and experimentation are being performed to determine the full potential of water fog for
manual extinguishment.
38
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Shipboard Engine Room Tests (SP-Sweden) --
Current International Maritime Organization (IMO) water sprinkler regulations have not been revised in
over 25 years, which leaves the new WMSs with no chance of acceptance. To adjust for this regulatory shortcoming,
the IMO developed guidelines for new systems that would perform equivalently to the sprinkler systems specified in
the old IMO regulations. The guidelines were adopted in 1992 and a working group was formed to develop
sprinkler/water spray test methods for accommodations, public areas, and engine compartments.
Ryderman (43) discusses the development of an engine compartment test method. The factors that must be
considered in developing this method include:
1. Types of fires—spray and pool
2. Fuels—variable from high viscosity heavy oils to diescl
3. Potential fire size—up to 30 MW
4. Ignition sources—e.g., heated engine block
5. Variations in compartment configurations
A preliminary test method was developed that used three diesel fuel scenarios: a spray fire, a pool fire, and
a combination spray and pool fire. The combination is presumed to be the worst case. The test was designed to
determine the reliability and quality of system components. Three typical volumes have been suggested as test
method standards for the various engine rooms in accordance with ship sizes: 500 m\ 3000 m3, and >3000 m3.
Over 200 tests have been performed to validate this test method. The tests have shown that WMSs have the
best performance in smaller rooms and also that larger spaces could present practical installation problems. Figure 8
shows the engine model.
Also under consideration are the accommodation and public area standards. The IMO Safety Committee
(MSC) is currently reviewing proposed sprinkler equivalency guidelines that would set the minimum requirements
for WMSs as follows:
1. The sprinkler head shall be placed in an overhead position and spaced in a suitable pattern to maintain
an average application rate of 5 L/min-mz.
2. The pump and piping system shall be capable of maintaining that application rate for a simultaneous
coverage of 280 m2.
3. The sprinkler shall come into operation within the temperature range of 57 to 79 CC.
39
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Steel Plate ~ 50 mm
Vail
, Solid Steel
/ plate ~5 mr
0.35 rr, £
l\IS0.3m
End View
Flowing I Spraying /
and Concealed •—
oil spray
Steel plate mm
'/// ^///
Steel plate^-2 mm
Tray 4m g/ Tray 0.5
0.10 m gap between engine
and inside perimeter
of bilge
Tray 4 m
Notch for
flowing
fuel
Top Tray 3 m
T«pview
2.0 m
Steel Ptate~50mm
500 x300
Figure 8. Engine model.
40
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National Research Council of Canada (NRCC) --
Mawhinney (32) describes engineering design criteria for machinery space WMSs based on Canadian Navy
experiments conducted at the National Fire Laboratory in Canada.
Key WM fire suppressant characteristics include drop size distribution, spray flux, and spray momentum.
The use of spray additives can also affect system performance. Test results are based on a particular set of nozzles
for a specific set of conditions. Committing to one particular nozzle or system design for all applications is not
appropriate until all engineering constraints have been analyzed. System design must be based on fire suppression
objectives and overall system economics in making the decisions on whether to use low-pressure, intermediate-
pressure, high-pressure, or dual-fluid nozzles.
Water mist fire suppression does have total-flood limitations, particularly for the nozzles tested by
Mawhinney. For the purposes of the Canadian Navy, compartments size limits of 200 in3 maximum are set by
economic and space/weight storage restrictions.
Mawhinney concluded that WM holds potential to be an effective fire suppressant for hydrocarbon liquid
pool and spray fires, depending on the geometry of the compartment.
Table 4 presents Mawhinney's results for spray density and flow duration, depending on ventilation
conditions and degree of compartment obstruction. These results apply only to the nozzle arrangement tested, which
used a generic industrial spray nozzle that was not optimized for fire suppression.
SINTEF (Norway) —
The effectiveness of water, in the form of a fine water spray and as an extinguishant, has been recently
demonstrated in full-scale testing conducted at SINTEF Laboratories in Trondheim, Norway (44). A full-scale
mockup of an enclosed ABB Stal GT-35 gas turbine was used for these tests.
The design incorporates a dual-fluid nozzle that combines water and air to produce controlled-size water
droplets, which are readily transported by air into the base of the fire. This delivery system leads to a rapid
extinguishment of large intense fires using limited amounts of water.
The SINTEF investigators determined that a mean spherical diameter of 142 pm is ideal for extinguishing
most hydrocarbon fires. The technology (British Petroleum's dual-chambered nozzle) can produce drops from 80 to
200 pm in mean spherical diameter.
4!
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TABLE 4. DESIGN CRITERIA FOR A WATER MIST TOTAL-FLOOD FIRE SUPPRESSION
SYSTEM IN MACHINERY ENCLOSURES
Fire
category
Category
description
Ceiling flux density
(L/min-m^)
Under-deck flux
density (L/min-m2)
Duration of spray
(min)
Obstructed:
No
Yes
No
Yes
No Yes
1
Large(>1 MW)
under-ventilated:
pool and jet spray
fires
2
4
1
3
1 3
II
Large (>1 MW)
well-ventilated:
pool and jet spray
fires
4
6
1
3
2 4
Ilia
Medium
(0.4-1.0 MW),
well-ventilated,
hidden pool fires
2
4
3
3
2 4
1Mb
Small (<0.4 MW),
well-ventilated
pool fires
2
3
1
3
1 2
[lie
Fires in insulation
or rags soaked
with oil
3
5
1
2
2 5
The required nuzzle pressure of 0.5 MPa is accomplished by reducing the storage pressure of 15 MPa to
0.5 MPa. Higher fluid storage pressures reduce the space requirement.
Since drops are developed inside the dual chamber, orifices as large as 2 mm may be used, requiring less
stringent water quality requirements (larger particle impurities can be tolerated).
The scenarios run were pool fires and jet fires, i.e., typical fire scenarios for a gas turbine. Jet fires stem
from a leak in high-pressure lines of up to 4 MPa, and pool fires stem from spills from low-pressure lines.
The ability of the fine water spray to extinguish fires in gas turbines has been shown to meet initial
performance requirements with substantial safety margins. While the installation could be equipped with 200 L of
water, only 10 I. were required to extinguish a large fire, leaving ample room for additional discharges.
Federal Aviation Administration —
The Federal Aviation Administration (1;AA) has performed tests to evaluate and develop an on-board
aircraft cabin water spray system to control post-crash fires (18). Initial designs provide a system with an array of
nozzles at the ceiling centerline, which continuously discharge within the entire cabin for 3 min. Several fire
42
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scenarios include a wind-driven external fuel fire adjacent to the fuselage opening and a quiescent fuel fire impinging
on the intact fuselage. Tests have been performed for both narrow-body and wide-body aircraft. Hazard analysis
assessments, using a dose fraction model, show that, in general, the water spray system provided about 2 to 3 min of
additional survival time under a variety of conditions.
From the results, a zoned water spray system has been conceptualized, designed, and tested under full-scale
conditions. The results of the zoned system tests showed that zoned systems can work as efficiently as the previously
tested cabin system with 10 percent of the water requirement, a low percentage crucial to space and weight
limitations for aircraft.
Deflagration Suppression Studies --
A test fixture for investigating the effects of WMSs on hydrogen deflagrations was constructed and
successfully operated at the Denver Research Institute (DRI) (45). The quenching of hydrogen deflagrations at
six percent hydrogen concentration in air was demonstrated with WM. Results showed that the concentration of
WM required to quench the deflagration was 0.7 L/min-m3 of protected space. This threshold is believed to be a
function of the hydrogen concentration at the time of ignition. At mist concentrations below this threshold, there was
pronounced evidence of water droplet evaporation during the deflagration. The cooling effects were documented by
reduced temperatures and peak pressure during the deflagration.
Water mist could be a viable alternative for explosion suppression if time is allowed to inject the
concentration required to quench the mixture. Figure 9 documents the results of the DRI experiments. Further
testing is underway at DRI to document the effects of drop size on quenching concentration.
Overall Test Review and Conclusions
Much research has been conducted on WMSs, primarily for maritime applications (Class B fires).
Although the test results and estimated design parameters vary dramatically, the general conclusion appears to be the
same. WMSs are extremely effective if the WM reaches the fire. This requires that the delivery system distribute
the mist uniformly throughout the protected compartment. It also suggests that extinguishment is not significantly
aided by the entrainment of the droplets by the fire. The required system parameters needed for the WM to behave
as a total-flooding gas (namely, drop size) have been identified, and the real problem lies in adapting the system or
modifying today's technology to meet this requirement.
The limited theoretical work developed on WM fire suppression and the applied research and development
testing performed using available hardware demonstrates the high potential for WM as an effective fire suppression
agent. WMSs are. effective sprinkler replacement systems in light hazard and some ordinary hazard occupancies.
43
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El Quenched
E Deflagrated
Figure 9. Summary of tests performed with a six-percent hydrogen in air mixture ignited in the
presence of WM.
WMSs have not been shown to provide total-flood protection in highly obstructed situations, such as the
electronics/computer applications that account for 75 percent of the Halon 1301 usage. It appears that in the future a
combination of (1) theoretical work on mist transport with testing specifically designed to evaluate transport and
obstruction problems and (2) full-scale testing with both commercialized and industrial spray nozzles is needed.
It is not possible at this time to address WM as a suppression agent without including the delivery system,
nozzle characteristics, mixing and distribution behavior, etc. The data show a wide variation in the water application
rate necessary to achieve extinguishment, which is largely driven by differences in system hardware.
Summarizing this discussion, the following facts emerge:
1. A wide range (type) and number of WM technologies are available.
2. Limited testing to date demonstrates the potential efficacy of mist systems in many fire scenarios.
3. Extinguishment parameters appear significantly different for WM, total-flooding gas, and sprinkler
technologies and will most likely require separate evaluations of their effectiveness.
4. The optimum design and operating conditions for these technologies are unknown.
5. Cost and reliability are unknown but can be. expected to vary widely with method or application.
6. Design and installation standards for mist systems will be strongly dependent on the mist hardware
and system selected, a situation that is likely to be true for the next several years.
44
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7. Near-term determination of the efficacy and installation requirements can only he developed through
testing and empirical analyses.
For a WM fire suppression system to be considered a reasonable replacement for a clean total-flooding gas,
the WMS must meet the following conditions:
1. Extinguish fires in highly complex obstruction conditions throughout a compartment.
2. Maintain extinguishing concentrations for a 15- to 30-min time frame.
3. Minimize secondary or collateral damage.
For particular applications, other constraints such as space and weight, electric power demands, system
complexity, etc., may also be important.
None of the research performed to date demonstrates the ability of WM to meet the three primary
conditions of an effective total-flood replacement as outlined above. However, the potential for developing the
capabilities of WM for these applications has been shown.
It is not possible now or in the foreseeable future to use theoretical models to predict the performance of a
WMS. Sufficient information on the required drop size distribution, spray velocity, momentum, pattern or
mixing/distribution, and the interaction of such designs with turbulent diffusion flames is needed to design a system
from first principles. Relying on testing of existing technologies against realistic fire scenarios is inefficient in terms
of the quality of data and insight provided. A combination of small-scale testing to define mist spray parameters
necessary for extinguishment in obstructed geometries and full-scale testing using the most promising mist
technologies and realistic tire scenarios is the most effective intermediate-term strategy.
REVIEW OF LOW RESIDUE PARTICULATE (LRP) IN FIRE SUPPRESSION TECHNOLOGY
Introduction
LRPs, especially PGAs, have recently come to the forefront of fire suppression technology as an expanding
area of research and development. At least six independent groups are working on various aspects of this potential
fire suppression technology. LRP is being looked at as a partial replacement for halon and as a new application for
areas where costs or conditions have not yet demonstrated a feasible fire suppression alternative.
LRP systems have attracted great interest for a number of reasons. The following are the perceived
advantages of these systems:
1. Inexpensive
2. Easy to retrofit
3. Low space and weight requirements
45
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4. Potential as a total-flood agent
5. Self-contained systems
6. Zero ozone depletion potential
7. Non-toxic at flame extinguishing concentrations
Although intensive research and development has only recently been initiated for this technology, some
potential benefits have already been demonstrated, e.g., low space and weight requirements and self-contained
systems.
Background
Although the use of dry chemicals for extinguishing fires has been known for many years, they may cause
unacceptable levels of collateral damage, especially to electronic components and moving parts. In spite of their
high effectivcness-to-weiglu ratios, the collateral damage, lack of uniform delivery, and an inability to extend
inertion have caused dry chemicals to be rejected for many applications.
The use of LRP takes advantage of the well-established fire suppression capabilities of dry chemicals, with
potentially reduced or eliminated collateral damage normally associated with the use of traditional dry chemicals. A
fine solid particulate may also allow distribution of a particulate cloud uniformly throughout a complex space. If the
particle size is small enough, the particulates may remain suspended in the protected space for times on the order of
tens of minutes. These suspension times could allow fine solid particulates to act as total-flood agents, yielding
significant advantages over present dry chemical systems and potentially some halon systems. LRPs encompass
propellant generated solid particulates (PGSP) and pyrotechnically generated aerosols (PGA).
PGSP technology propels fine powders using high-pressure gases or pyrotechnics, e.g., rocket propellants
(4). This technology requires grinding the agent, adding flow-promoting and anti-caking ingredients, and developing
delivery systems where clogging and oxidizer/fuel ratios have been taken into account. Experience in both fire and
ordnance technology is required in designing specifications for fire extinguishing systems.
PGA development originated in the late 1980s in the Soviet Union (5). The systems utilize a chemical
reaction to produce ultra-fine particulates from combustion products of an oxidant and a reductant. In principle, the
resultant aerosol is distributed throughout the protected volume at a concentration sufficient to cause chemical
inhibition of the fire chain reaction and gas phase cooling, hence fire extinguishment. There is some debate over tlie
proportion of the suppression mechanism due to chemical inhibition of the fire chain reaction versus gas phase
cooling. Although chemical particulates at low temperatures can act as catalysts to recombine fire chain propagators
to give chemical inhibition, solid chemical particulates may also decompose in the flames to produce inhibiting
species stich as alkali hydroxides. For aerosol particles on the order of I jim in diameter, the residence time required
to produce the reactive species is short, and the diffusion of the small particles will tend to maintain their availability
46
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in the flame. Alternatively, the use of solid particulates as a mechanism for gas-phase cooling is well known and
involves specific heat, fusion, vaporization, and decomposition. Wilh small particles, depending on the chemical
composition, a sizable increase in extinguishing effectiveness is achieved and can be explained by flame heat
removal. Extensive studies for dry chemicals and powders have been carried out by Hughes Associates (6-8).
LRP technology, particularly PGA, is being pursued by several groups with much of the formulation work
being proprietary. Ongoing work includes efforts by Spring and Ball (9), Kiberl et al. (10), Harrison (4), Andreev et
al. (5), and Spcctronix/Ansul (11).
Theoretical Considerations
Overview —
PGA development is still in its infancy, with regard to chemistry (formulations), applications, and systems.
At present there is little theoretical basis for specifying the optimum particle size, size distribution, velocity
distribution, and other important particulate system parameters.
PGA development work today focuses on systems where the active components, an oxidizer, and a reducer
are combined with a filler (10). The components are ground into a fine powder and mixed with an epoxy resin
binder. Upon ignition of the material, the active material is ejected as a dispersion aerosol, while parts of the
combustion products form condensation aerosols. Dispersion aerosols are formed by the atomization of solids;
condensation aerosols are formed by condensation of superheated vapors or chemical reactions in the gas phase. In
general, dispersion aerosol particles predominate and their particle size is normally larger than the condensation
aerosol particle.
The residence time of the fire suppressant in the protected space depends on the ability of the aerosol
particles to remain suspended, which is dependent on particle size and velocity. The aerosol particles, if they are to
replace a gas in certain applications, must be able to flow around obstacles in a complex space. The larger the
particle size, the less able the particle will be to change direction, causing it to impinge on obstacles in die space. As
particle si/e increases, the inertial and viscous forces of the fluid begin to dominate. The ability of the aerosol to
remain suspended is predominately governed by Stokes' Law, which predicts the terminal velocity of the particles
through air and, consequently, the residence time of the aerosol. Particles on the order of 1 (im in diameter at
101.3 kPa and 20 °C will have a terminal velocity of about 10"^ ciii/s according to Stokes' I .aw. Aerosols with
particle diameters on the order of 1 um will be able to remain suspended in the protected space for times on the order
of tens of minutes.
The loss of aerosol particles in suspension can be attributed to several phenomena: settling, diffusion, and
agglomeration. Again, size and velocity of the aerosol particles determine the driving forces. Larger particles tend
47
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to fall more quickly and arc lost via settling. Smaller particles tend to diffuse to surfaces in the space by Brownian
motion. Agglomeration, the formation of larger particles from smaller particles via collisions and adhesion,
increases the particle size due to cluster formation to a point where settling again dominates.
Chemistry -
In designing an effective fire extinguishing agent, particle size requirements and size distribution
requirements for the aerosol need to be better understood, liwing et al. showed that dry chemical powders have
si/able increases in extinguishing effectiveness below a certain particle size (7, 8). Evidence suggests that below this
limit size. SL, fire extinguishment is dominated by homogeneous processes and chemical inhibition of the chain
reaction. Above the SL> heterogeneous processes and heat extraction mechanisms dominate. Below the SL, Ewing's
work demonstrated that fire extinguishment effectiveness was essentially constant with varying particle size.
However, aerosol suspension lifetimes (sedimentation), ability to flow around obstacles, and ability to penetrate the
flame may vary greatly even over these lower particle size ranges. This is an area of research that has not been well
explored.
While many industrial formulations are proprietary, most of the work in the literature has centered on alkali-
metal salts which, as dry chemical agents, have been shown to be especially effective fire suppressants. The
chemistry of the aerosols is similar to diat of dry chemical agents. The dominant mechanisms for fire suppression
are heat absorption (involving specific heat of the particulates), fusion, vaporization, decomposition, and chemical
inhibition of the fire chain reaction. Depending on the temperature at the point of interaction, the aerosol particles
act by heterogeneous or homogeneous inhibition (46). The aerosol particles, due to their small size, create a large
total surface area for capturing the active species of the fire chain reaction. Heterogeneous reactions occur on
particles still in a solid state; the particles act like catalysts offering sites for recombination of fire chain propagators.
Once particles enter higher temperature zones, homogeneous or gas-phase reactions may occur.
Heterogeneous processes typically follow the general reaction sequence:
•A + S —» AS 11 ]
AS + »A-»A: + S [21
where *A is an active free-radical species in the fire chain reaction (such as »OH, »H, or 'CHj) and S is the solid
aerosol particle surface. The trapped free radical forms AS, which reacts with another active species, *A, in the fire
chain reaction creating a stable molecule, A2 ( H20, C02, C„H2n+;>, etc.). The solid aerosol particle, S, is regenerated
and made available, for further interactions.
A typical homogeneous process (shown for an alkali metal agent) has the following general reaction
sequence (47):
48
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K + *0H + M -» KOH + M [3]
KOH + »H ^ H,0 + K [41
KOH + *OH - > H20 + KO
[5]
where M is a third-body molecule (e.g., N2), *H is a hydrogen atom, and *OH is a hydroxyl radical. The latter two
species are free radicals. K is a precursor atom and KO is an oxide of the precursor. The extinguishment process is
similar to that of halon.
Chemical precursors that interact with the active fire species are usually derived from salts of alkali-metal
cations (K+ and Na+), ammonium ion (Nil/), and anions such as carbonate (COj"2), bicarbonate (HCO.?). sulfate
(SO4'2), and phosphate (P04 '). Potassium salts are generally more active than sodium salts, and the anion associated
with each is an important factor in fire suppression effectiveness (46).
Commercial Low-Residue Particulate Fire Suppression System Technology
LRP systems (PGSP or PGA) are just now entering the marketplace in limited applications. PGA work is
more predominant than PGSP work, but formulation, specific end use delivery hardware, and performance testing
are still being developed. Industrial development is being carried out by the All-Russian Fire Research Institute for
Fire Protection, Russia; Spectronix, Inc., Israel; and Ansul Fire Protection, U.S.A., under license from Spectronix.
Government-sponsored testing is being carried out at NMRI/WPAFB, NMERI, NRL, FAA, and WL/FIVCF (see
Abbreviations and Symbols).
Overview of Testing to Date
Work done to date 011 LRPs (PGAs) has centered on formulations, concentrations required to extinguish
Class A and B fires, documentation of any potential acute toxicity from the aerosols generated, and generator
systems.
Spectronix, Inc. has been a leading commercial company in the development of PGA. Spectronix has a
Cooperative Research and Development Agreement (CRADA) with the U.S. Air Force. Additionally, Spectronix
has license and cooperation agreements with Grinnel-Ansul and Amerex in the U.S., and Chubb in the U.K.
Spectronix has approximately 12 current formulations under study and has been actively developing prototype
generators for different fire scenarios.
NMERI has completed a preliminary test series on Spcctrex Fire F.xtinguishant (SFF.) from Spectronix for
Wright Laboratories (3). The testing involved igniting small pellets of different SFE formulations in the NMERI
Laboratory Extinguishment and Emissions Test Chamber (LEETC). The LEETC is a 175-L enclosed metal test
49
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chamber, which can be used to (1) determine extinguishment characteristics of total-flood agents, and
(2) characterize and quantify emission products from extinguished fires. The testing included extinguishment of
Class A and B fires and determinations of whether the SFE would extinguish partially obstructed fires. The SFE
successfully extinguished all fires for the conditions tested.
Work at the Naval Research Laboratory (NRL) on 56- nv- compartment fires showed that SFE could
extinguish fires (48). Testing at NRL found that the heat generated during the combustion of the SFE pellet causes a
buoyant plume that rises slowly and forms a ceiling layer before gradually descending along the enclosure walls as
the layer cools, thus slowing the fire's extinguishment. Additional work using different generators, WM cooling, and
generating SFF. aerosol under water to cool the aerosol has been carried out to overcome the heat-of-coinbustion
problems. The results indicate that cooling the aerosol cloud to aid in dispersion throughout the space is not a simple
task.
Ansul Fire Protection has licensed Spectronix's technology. Ansul has the capability of making 100 kg of
SFH per month in pellet form. Ansul is actively working to develop new and improved formulations. Their testing
to date shows that SFE can extinguish a Class B fire in an enclosed space. Testing of SFE in non-enclosed spaces
and with deep-seated Class A wood crib fires indicates thai present formulations and equipment cannot reliably
extinguish fires in those scenarios.
Limited acute toxicity testing of SFE formula "A" at NMRIAVPAFR showed no lethal effects at the
recommended test levels for fire extinguishment (49). However, the animals did demonstrate stress-related activities
when subjected to the aerosol. NMRT is continuing testing to determine the mechanisms involved and to determine
long-term effects on the test animals for lower SFE exposure concentrations. As indicated earlier fine particles are
an area of concern with regard to long term health effects from acute inhalation when using LRP. However this area
is not addressed here, but must be accounted for as results become known.
LRP Conclusions
Work done to date on PGA has centered on formulations, concentrations required to extinguish Class A and
B fires, documentation of acute toxicity, and generator systems. Additional work has been done to overcome the
heat-of-combustion problems, particularly where the aerosol dispersion throughout the protected space was delayed
due to the buoyancy of the aerosol cloud. Work has just begun on containers/generators to hold the fire suppressant
pellets and to disperse the aerosol cloud without causing secondary fires from the generator systems.
Preliminary testing at NMliRl, NRL, and ANSUL has demonstrated that PGAs can extinguish Class B fires
in enclosed spaces. ANSUL's testing of PGAs in open spaces on Class B fires and on deep-seated Class A wood crib
fires show a lack of reliable extinguishment. The FAA stated at the second meeting of the International Ilalon
50
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Replacement Working Group in England during March of 1994 that PGA was unsuccessful in passing the tests for
Class A fires in a cargo compartment scenario.
Phase I testing for acute toxicity at NMRI has shown that SFE formula "A" was nontoxic at extinguishment
concentrations. However long-term health effects from inhalation of less than 10 um particles need to be fully
investigated.
While the potential for PGAs exists, it will require considerable work to bring it on line as a new
application or as a replacement for halons in certain applications.
Recommendations
Areas of investigation for a LRP program, particularly one that includes PGAs, need to encompass the
following:
1. Identification of LRP sources and their characteristics.
2. Work on particle sizes generated and on particle size effects on extinguishment, dispersion,
cleanliness, and environmental characteristics.
3. Work on effectiveness for suppression of Class A, B, C, and D fires. Particular attention is needed to
minimum concentrations and particle size distributions required to extinguish each class of fire.
4. Chemistry of particulate aerosols, particularly alkali-metal salts, anions, and oxidant/ieducing
agent/filler combinations.
5. Ability of particulate aerosols to suppress and inert explosions, along with their particle size and size
distribution effects.
6. Compatibility of the particulates and combustion products with electronic components and materials
in protected space.
7. Characterization of residue composition, amount, and thermal/electrical conductivity. Procedures for
minimizing residue should be investigated.
8. Work on the thermal emission characteristics of the burning of the PGA including time/temperature
profiles, radiative emission, and total heat output.
9. Safety considerations for handling, packaging, transportation, and shelf life. These studies should
include investigations of toxicity and the possibility of effects from an accidental ignition.
10. Environmental impacts of emissions and disposal of residues.
11. Work on generators, construction materials, fuses and other ignition devices, and their effect on the
aerosol particulates.
12. Suitability for use, specific LRPs, in occupied and unoccupied spaces.
13. Cost and/or cost effectiveness.
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ASSESSMENT OF THE "STATE-OF-THE-ART" FOR WATER MIST (WM) AND LOW-RESIDUE
PARTICULATE (LRP) SYSTEM FIRE SUPPRESSION TECHNOLOGY
The technology reviews for WM and LRP fire suppression technologies discussed above lay the foundation
for assessments of the state-of-the-art with regard to these technologies as required for Task 1. Based on the
evaluation of their current stage of development and fire suppression potential, WM technologies have been chosen
for development and econometric review. WM technology has been selected for the experimental program in this
project to define and optimize the operating parameters for the technology with respect to fire suppression at the
laboratory-scale, followed by room-scale proof-of-concept testing, and, finally, system engineering and cost
comparisons for three different applications using a traditional halon fire suppression system and the proposed
replacement system.
Status of Water Mist Fire Suppression System Technology
Water mist fire suppression technology can draw upon the broad base of hardware and theoretical
knowledge developed for controlling air pollution aerosols, industrial scrubbing, humidifying, air cooling, dust
suppression, foam control, and moistening. Currently at least 17 WMS technologies are available or are under
development by different manufacturers. The potential suppliers of nozzles and systems greatly exceed this number.
The use of relatively small (10 to 200 |im) diameter water droplets for fire protection has been established
for at least 40 years. The suppression mechanism of WMSs is primarily gas phase cooling of the name reaction zone
to below the flame temperature limit. Steam expansion and oxygen depletion are also important in suppression of
enclosed fires, particularly multidimensional flammable liquid spray fires.
The efficacy of WMSs is strongly dependent on the ability to generate sufficiently small droplet sizes and to
distribute a critical concentration of droplets throughout the compartment. Unfortunately, a widely accepted critical
concentration of water droplets required to extinguish a fire is yet to be determined. Factors that contribute to this
critical concentration of WM throughout the space to be protected consist of droplet size, size distribution, droplet
velocity, spray pattern geometry, momentum and mixing characteristics of the spray jet, and geometry and other
characteristics of the protected space. The complexity and variety of the protected spaces will require that final
choices regarding system development, although aided by this project, will necessitate evaluation of the WMS in the
context of the specific application for the reasonably near future.
Performance testing has been completed for different systems in particular applications. Among these
applications, WMSs have been demonstrated on Class B spray and pool fires, aircraft cabins, shipboard machinery
and engine room spaces, shipboard accommodation spaces, and computer and electronics applications.
Among the various systems tested, the MicroMist System by Baumac and the Hi-fog System by Marioff
represent the extremes of design philosophy for single-fluid high-pressure WMSs. Marioffs Hi-fog relies on spray
52
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momentum for distribution and mixing of the drops, while Baumae's MicroMist utilizes many nozzles that produce
small droplets with very little spray momentum.
The major feature of the Marioff nozzle is its droplet size distribution. The flow pattern is comprised of
both large (-100 (Jrn) and small (<50 urn) drops. The large droplets provide spray momentum that assists in
penetration and mixing. Also, the large droplets are believed to be required for cooling burning surfaces.
Baumae's MicroMist System most closely approximates a total-flood system. It produces a large amount of
very small droplets that have almost no spray momentum.
In spite of the progress made with WMSs to date, their overall extinguishment efficiencies are still
significantly less than that of halon. Moreover, they may be unsuitable for total flood in many applications.
Additional work needs to be carried out to optimize fine WMss and to test the fire suppression and extinguishment
limits.
Status of Low-Residue Particulate. Fire Suppression Technology
Work done to date on LRPs, particularly PGAs, has centered on formulations, concentrations required to
extinguish Class A and Class B fires, acute toxicity, and generator systems. Additional work has been done to
overcome the heat of combustion problems, where the aerosol has been delayed in dispersing throughout the space
due to the need to cool the aerosol cloud. Other areas where work has just begun is the development of containers
and generators to hold the fire suppressant pellets and to disperse the aerosol cloud without causing secondary fires
from the generator systems.
Initial testing at the NMLiRI, NRL, and ANSUL laboratories has demonstrated that PGAs can extinguish
Class B fires in enclosed spaces. Phase I testing for acute toxicity at NMRI indicated that Spectronix's SFE formula
"A" was nontoxic at extinguishment concentrations. ANSUL's extinguishment tests of PGA in open spaces on Class
B fires and on deep-seated Class A wood crib fires were unsuccessful. While the potential for LRP or PGA exists,
development will require a great deal of work to bring either LRP or PGA on line as new applications or as
replacements for halons in certain applications.
Areas of investigation for a LRP program, particularly PGA, are given in the Recommendations (see the
previous review of LRPs in fire suppression technology).
SELECTED EXPERIMENTAL INVESTIGATION
Since LRP technology is still in its infancy, pursuing development of this technology under the timetable
and requirements of Task 1 of this project is not recommended. Although LRP technology shows potential as
retrofit replacement and as low weight and/or mobile systems for fire suppression and possible inertion, significant
53
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work still needs to he clone before this technology will be ready for full application testing, development of
production standards, and incorporation into NFPA and other standards.
The assessment of the state-of-the-art for the WMS shows that this technology is viable, although additional
information and development are necessary before the WMS can replace Halon systems. Development of a WMS is
recommended as the most promising technology for investigation under the requirements of the contract.
Some potential problems or questions that would be worthwhile to incorporate into the experimental test
program are the following:
1. Determination of critical concentration, i.e., the minimum total mass of water in droplets per unit
volume required to extinguish various Class A, B, and C fires.
2. Effect of droplet size and si/e distribution on critical concentration.
3. Effect of droplet velocity on critical concentration.
•4. Effects of obstacles on critical concentration.
5. Effect of droplet size, size distribution, and droplet velocity on the ability of the mist to penetrate
complex spaces.
6. Determination of droplet lifetime and droplet suspension lifetime for inertion.
The results from the laboratory-scale experimental test program should aid in designing a WMS having the
optimum drop size, size distribution, velocity distribution, spray momentum, and other important WMS parameters.
Information obtained will be used in developing a room-scale WMS to demonstrate scale-up capabilities and proof-
of-concept testing for the WM technology chosen.
The experimental apparatus and instrument used for the aerosol fire suppressant evaluation should aid in
development of methods to determine droplet size and size distribution for efficient fire suppression in any given fire
scenario. The ability to design the droplet size distribution to ensure sufficient small droplets for efficient fire
suppression and sufficient larger droplets for cooling burning surfaces should be the long-term goal. Additionally,
the determination of suppression lifetime with regard to droplet size and size distribution would allow WMSs to be
evaluated for total-flood use.
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SECTION 6
TASK 2: EXPERIMENTAL TEST PROGRAM
INTRODUCTION
A WMS has been selected for system development in this program. WM technology is more advanced in
its development, and WMSs have the ability to he fielded in the near term as opposed to LRP systems. WMS
technology can use the broad base of hardware and knowledge developed for other industrial applications.
Additionally, a WMS can utilize much of the same control and detection equipment already approved for water
sprinkler systems.
Water mist suppresses or extinguishes fires through three predominant mechanisms: (1) heat extraction
using water's latent heat of vaporization and gas phase cooling, (2) oxygen displacement by steam expansion, and
(3) radiant heat attenuation involving surface cooling by surface wetting and evaporation and blocking of radiant
heat transfer. Secondary mechanisms that have varying effects on fire extinguishment include (1) vapor/air dilution,
effective with higher flash point hydrocarbon fuels, resulting in bringing the vapor/air concentration below its lean
flarrimabilify limit; and (2) kinetic effects and flame-front attenuation, where the WM and resultant evaporation
reduce the velocity of the flame front and overpressure in deflagration control. To date, the approach taken by most
WMS manufacturers has been to set up full-scale room tests with nozzles taken from other applications and
determine under what conditions they will extinguish various fires. The approach taken here is to determine the WM
properties that most effectively extinguish a fire and to design a WMS based on those parameters.
The following areas of investigation are worth incorporating in the development of a WMS:
1. Determination of the critical concentration, i.e., the minimum total mass of water in droplets per unit
volume required to extinguish various Class A, B, and C fires.
2. Effect of droplet size and size distribution on critical concentration.
3. Effect of droplet velocity on critical concentration.
4. Effect of obstacles on critical concentration and suppression/extinguishment of fires.
5. Effect of droplet size, size distribution, and droplet velocity on the ability of the mist to penetrate
complex spaces.
6. Determination of droplet lifetime and droplet suspension lifetime with regard to inertion.
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OBJECTIVE
In laboratory studies, the effects of droplet size, droplet size distribution, droplet velocity, and obstacles in
the path of the spray were studied with respect to how they affect the critical concentration needed to extinguish
various classes of fire. The information obtained was used to characterize and optimize the operation of selected
WM spray nozzles to be used in developing a WMS capable of replacing halon systems in selected applications.
Room-scale testing of the selected and optimized WMS was then conducted to determine the overall
effectiveness of the fire suppression system in actual use. The ability of the system to suppress fire, protect against
explosion or reignition, and to limit the damage to powered equipment, paper records, and electronic data storage
contained in the room was assessed.
METHODOLOGY
Laboratory-Scale Experiments
The test program utilized various types of single-fluid nozzles and nozzle size combinations to study the
properties of WM, leading toward an understanding of the WM properties needed to optimize spray performance for
fire suppression and extinguishment. The nozzle testing slarted with the manufacturer's recommended operating
parameters for the initial mist production. The test program ran tests maintaining water flow and pressure, then the
water flow and pressure were varied to change the mist concentration and WM properties, thereby determining the
minimum WM concentration required to extinguish Class B heptane fires.
Initial Approach —
The initial test program approach involved the construction of an aerosol test chamber (A'l'C) to allow WM
to be discharged into a large volume and then transported past a fire. This approach was taken since previous
experiments indicated that misting system discharge force alone can extinguish fires.
Nozzle testing involved collecting the following data for each test and condition run:
1. Air flow (nrVs)
2. Gravimetric WM concentration (g/L)
3. Temperature (°C)
4. Relative humidity (%)
5. l'raunhofer (small angle forward) diffraction characterization of the. WM
Fraunhofer (small angle forward) diffraction (FD) measurements included determinations of (I) arithmetic
median droplet diameter, (2) Sauter mean droplet diameter, (3) volume/mass median droplet diameter, and
56
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(4) number median droplet diameter. The measurements were also used to develop histograms for the (I) number
density according lo diameter (occurrence), (2) number density according to surface area, (3) number density
according to droplet volume, and ('1) cumulative droplet volume according to number.
Nozzle testing involved (1) maintaining a constant VVM concentration and varying droplet size by altering
air flow and water pressure to the nozzles. (2) maintaining droplet size/size distribution by holding water flow
constant and increasing or decreasing air flows to see whether WM properties affect flame penetration and
extinguishment concentration, and (3) optimizing nozzle conditions for the most effective fire extinguishment, by
placing actual or representative obstacles in the mist stream to measure the effects of obstacles on WM distribution.
Development of the Aerosol Test Chamber (ATC) -
The development of the ATC and the JrD instrument in particular, with its ability to characterize aerosol
clouds before and after interactions with a fire, was the centerpiece of the initial experimental program. At present,
no laboratory test chambers allow multi-station analysis of the interaction of aerosol clouds with fires under
controlled conditions and for different fire scenarios. Since the ATC utilizes a newly developed instrument, a
complete description of the basis for its design and operation is important to its acceptance. Due to the length of
detail on the FD instrument, its inclusion in the main body of this report proved to be cumbersome. Since it does not
directly relate to the program's primary tasks, the development of the Fraunhofer small angle forward diffraction
instrument and its use in the ATC are attached to this report as Appendix A.
Test Apparatus
The ATC (Figure 10) developed for this project has total volumes of 2.6 m-1 for the vertical test zone and
2.8 m3 for the horizontal test zone. The WM mixing chamber encompasses 2.4 m3 of the volume of the test
chamber. The ATC is located under a forced air hood, which exhausts all excess WM and fire combustion products
from (he building. Class B fires use 10 ml. of heptane floated on water in a 50.4-mm diameter pan (telltale). The
telltale is placed between two of the Fraunhofer forward diffraction detectors and two temperature/humidity
detectors in the vertical or horizontal test zones of the ATC.
Instrumentation
Instrumentation and data acquisition for the ATC incorporate the use of two or more personal computers.
Air/WM stream temperature and humidity are monitored and recorded by one data acquisition computer, while the
other personal computer(s) operate(s) the Fraunhofer small angle forward diffraction instrument (FD) and rccord(s)
all the data scans for droplet size and size distribution. Upon completion of a test series, the FD eomputer(s)
perform the data reduction and graphing of the results. Measurements and data reduction yield the following results
57
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30
Exhaust Fan
Vortical Tost
Zone \
Pump Speecj
Control I
\
\\
^4
Deflectors
Fraunhofer Diffraction \
Instrument v \
I /'
^f\
j! •
Qnrfr i
r \i
,,'V~
"in
\ U U
Horizontal
Test Zone
Front View
txhaust Hood
Water Mist
Nozzles
Flow Meter
Pressure _
Gauge
Detectors
Air Intake Fan
-V
- ^
-j
II-JL1
: >1 //q-il
K I //11 i
: || i! |-
fn)
3.7 k W Pump /
Water System
0.0003 rrf /s @ 10.3 MPa
_5L
Lett Side View
Figure 10. Aerosol test chamber (ATC).
-------
for each data run: (I) arithmetic median droplet diameter, (2) Sauter mean droplet diameter, (3) volume/mass
median droplet diameter, and (4) number median droplet diameter. Histograms for the (1) number density according
to diameter (occurrence), (2) number density according to surface area, (3) number density according to droplet
volume, and (4) cumulative droplet volume according to number are obtained. In addition, manual monitoring,
setting and recording of air flow velocity, air pressure for dual- fluid nozzles, and water pressure and flow are taken
for each data run.
Since the FD instrument developed for installation into the ATC operates similarly and on the same
principles as a Malvern small angle forward diffraction instalment (a commonly used instrument for droplet size
measurement), the latter has been used for instrument and method validation. The FD instrument incorporated into
the ATC has the capability to express its data in the same manner as the Malvern instrument.
Alternative Test Method --
After the ATC was operational, it was found that controlling WM and airflow using intake and exhaust fans
proved unreliable in extinguishing the fires. At this point the initial test program was set aside and an alternative
method was developed to enable sufficient information to be obtained lo complete the laboratory testing required to
develop a WMS for room-scale tesing.
The alternative test method used a portion of the ATC to lest single-fluid no/zlcs. The range of single-fluid
nozzles available allows a wide spread (range) in WM characteristics without the additional variables added with
dual-fluid systems. The selected nozzles represent the range of products available — low pressure/high momentum
nozzles (2.7-mm orifice diameter), intermediate pressure/momentum impingement nozzles (1.0- and 1,4-mm. orifice
diameter), and low-momentum humidification nozzles (U.2- and 0.5-mm orifice diameter). The nozzles listed in
Table 5 were tested. The test matrix used (based on manufacturers' sales literature) is presented in Table 6.
TABLE 5. MANUFACTURERS' OPERATING DATA FOR NOZZLES SELECTED FOR TESTING
Manufacturer
Droplet size range*
Spray pattern
Flow rate per nozzle
Grinneli Aqua Mist AM11
10-325 |jm
- 15°
2.0x10"6m3/s
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TABLE 6. WATER PRESSURE AND WATER FLOW TEST MATRIX
Nozzle type
Number of
nozzles
Water pressure, MPa
Water flow, 10'4 m3/s
Lower limit
Upper limit
Lower limit
Upper limit
AM11
1
0.7
1.2
*
- 1.95
P 54
3
1.4
2.8
1.60
3.18
PJ 40
3
1.4
6.9
1.19
2.65
MX-20
14
3.4
6.9
*
7.68
MX-8
14
3.4
6.9
*
2.38
* Not available.
Five telltales with 20 niL of heptane were placed in the ATC spray chamber anil lit to check burn time
regarding 02 depletion with the door and ducts closed. Heptane telltale fires were chosen for this phase of testing
since the literature and researchers presently performing room-scale fire extinguishment testing have indicated that
telltale fires are the hardest to extinguish. Burn time to deplete available 02 with telltale fires was 11 min and 28 sec.
since the heptane was not completely consumed.
For each nozzle and test condition, 4.7 by 10"4-nr" (16-oz) water tumblers were placed at 9.7-cin spacings
across the floor of the aerosol spray chamber as shown in Figure 11. At the desired operating pressures, gravimetric
samples of the water were collected in each 4.7 by 10 4-m3 tumbler. From the operating time and the weight of the
water collected in each tumbler, the spray pattern above the tumbler in L/min-m2 was determined. Each cup was
initially weighed and the full pattern run across the spray chamber. Two vertical and two horizontal rows were
checked for pattern and flow rate reproducibility. The flow test duration depended upon the nozzle(s), but steady
state test times were obtained.
The results of the flow analysis were plotted. Based upon the dif ferent spreads (ranges) in water flux for the
nozzles, five positions were chosen for the placement of the 50.4-cm telltales. The telltales were filled to within
3 rriin of the rim with water and 10 mL of heptane and were ignited. After a 30-sec preburn, the fire suppression
system was started. The times required to extinguish telltales were recorded.
For the nozzles chosen for the room-scale testing, the nozzle characteristics were determined at 40 cm from
the nozzle and at the pressures at which the nozzles will operate during the fire suppression tests. Nozzle
characteristics were determined using either the. Malvern or the Fraunhofer instrument.
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107 cm
107 cm
Reproducibility
Pattern
F G H I J K
Diameter of each cup 9.7 cm.
Figure 11. Water-flux gravimetric sample pattern.
An analysis of the laboratory results was completed before proceeding to room-scale testing. Equipment
development experiments were conducted to select and optimize the components and placement of the fire
suppression system.
Room-Scale Experiments
Room scale experiments were proof-of-conccpt and scale-up testing. These experiments were conducted
based on the laboratory-scale selection of equipment and operating parameters to determine the overall effectiveness
of the fire suppression system in actual room-scale use. Assessments were made of the system's ability to suppress
fire, protect against reignition or explosion, and to prevent damage to powered equipment, paper records, and
electronic data storage contained in the room.
The fire test matrix for the room-scale testing of the selected system follows:
1. Heptane pan unobstructed
2. Heptane pan partially and fully obstructed
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3. Heptane telltale cans
4. Paper—partially obstructed
5. Wood crib- partially obstructed center line compartment
6. Wood crib—unobstructed with operating computers and books
LABORATORY-SCALE EXPERIMENTAL RESULTS
Aerosol Test Chamber (ATC) Results
Upon getting all the components operational, it was found that, in spite of early indications, controlling WM
and air flow using only the exhaust fan proved unreliable in extinguishing the fires. To increase the WM
concentration by allowing the WM two chances (rising and falling) to enter the duct work to the test zones, the
nozzles were placet! on the bottom of the ATC's stilling chamber with the nozzles sprays directed upward. Later, the
nozzle arrays were placed across from the duct work with the nozzles spraying toward the open duct. Finally, to aid
in conveying WM into the test zones, an intake air fan was added to the ATC in anticipation that blowing air into the
chamber might significantly increase the amount of WM being conveyed into the duct work leading to the test zones.
Although the addition of the intake air fan clearly made a visual difference in the apparent amount of WM exiting the
exhaust fan, it was determined that the heptane cup-burner fires were being extinguished with WM at approximately
90 percent of the air flow required to blow the fires out. This is in spite of the fact that cup-burner fires placed in the
ATC stilling chamber were easily extinguished using the same water flow conditions that could not extinguish those
fires in the horizontal test zone.
To investigate what was happening to the WM, the droplet size distribution was determined for the WM flowing
through the horizontal test zone at 4.53 m3/rnin for a combination of MX-8 and MX-20 nozzles and compared to the
droplet size distribution generated by the individual nozzles. Figures 12 and 13 show the droplet size distribution for
a MX-20 and a MX-8 nozzle, respectively, taken on the center line 40 cm below the nozzle at an operating pressure
of 6.90 MPa. A comparison of these results to the WM size distribution results obtained from Detector 5 for the
WM flowing through the horizontal test zone indicates that, at best, less than 10 percent of the WM was conveyed
into the test zone from the stilling chamber (Figure 14). Detector 5 is the last detector position in the horizontal test
zone and is 1.6 m from the stilling chamber (see also Figure A-13). The percent WM approximation is based upon
the relative heights and shapes of the normalized curves at the 10-|.im droplet diameter for the various figures.
Because only the smallest droplet sizes made it to the test zones, continued work with the ATC as designed
was unacceptable. This method was set aside, and an alternative test method was developed to enable obtaining
sufficient information to complete the testing required to develop a WMS for room-scale testing.
62
-------
40 -
¦ Run ? )
Run 3!
Q
£
o
>
25
2
o
H
O
4>
o
10
1000
100
Droplet Diamster, micrometers
Figure 12. Droplet size distribution for a MX-20, 40 cm below the nozzle and at 6.90 MPa.
30
~—Run 1
flt— Run 2
Run 3
o
£
_3
O
>
CO
o
o
c
8
o
CL
IT
1000
10
100
1
Dronlet D'arreter, rricrometers
Figure 13. Droplet size distribution for a MX-8, 40 cm below the nozzle and at 6.90 MPa.
63
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12 --
• Pjn 2
ra
o
I-
"S
c
0)
o
a>
a.
10
100
1
1000
Droplet Oameter, micrometers
Figure 14. Droplet size distribution: MX-8/20 spray at 6.90 MPa and air flow of 4.53 m3/min.
Fraunhofer Versus Malvcrn Comparison
The Fraunhofer versus Malvern calibration and performance evaluation was set up as an aside to the
primary requirements of Task 2. Since the final development of the WMS did not depend upon the use of the
Fraunhofer instrument, the results of this comparison were not included in the main body of the report. The results of
the comparison are listed in Appendix B.
Alternative Test Method - Water Mist Extinguishment Test Results
The outlined water flux and fire testing was completed, with additional testing carried out to determine the
critical concentration for heptane telltales and the effect of obstacles on tire suppression. Water flux and
repeatability results for the individual tests are listed in Appendix C. Tables 7 through 15 show the extinguishment
testing results for the various no/./.Ies and for various numbers of evenly spaced nozzles.
Although all the nozzles were capable of extinguishing the heptane telltale fires, the amount of water used
ranged from a high of 17.5 I./m2 for the Grinnell AM-11 (Table 7) to a low of 0.085 L/m2 for the Baumac MX-8 in
this test scenario (Table 15). The data indicated that heptane fires can be extinguished with very small fluxes and
64
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TABLE 7. EXTINGUISHMENT RESULTS FOR A SINGLE-NOZZLE GRINNELL
AM-11 SYSTEM
Manufacturer and
Nozzle Type
System operating
pressure, MPa
Telltale
placements
Water flux,
L/min-m2
Extinguishment
times, s
Grinnell AM-11
2.75
E6
32.063 ± 1.593
17.1 ± 13.8
F4
19.801 ± 1.593
4.4 ± 1.5
H3
19.151 ± 1.593
6.7 ± 2.9
H9
12.571 ± 1.593
10.6 ±6.8
J10
1.756 ± 1.593
153.9 ± 106.0
Grinnell AM-11
1.72
C8
38.602 ± .0754
6.8 ± 2.3
D6
21.210± .0754
3.4 ± 0.3
F4
14.017 ± .0754
4.1 ± 1.2
H4
52.700 ± .0754
13.8 ±8.1
J2
1.930 ± .0754
Burned out*
* Three of three telltales burned until they ran out of fuel.
t Telltale placement designations illustrated in Figure 11 on page 61.
TABLE 8.
EXTINGUISHMENT RESULTS FOR A THREE-NOZZLE BETE P-54 SYSTEM
Manufacturer and
Nozzle Type
System operating
pressure, MPa
Telltale
placement:}:
Water flux,
L/min-m2
Extinguishment times,
s
BETE P-54
2.59
B4
10.666 ± 1.014
5.7 ± 1.2
D4
14.187 ± 1.014
7.8 ± 2.4
D7
21.484 ± 1.014
4.1 ± 1.1
F2
5.876 ± 1.014
9.6 ± 1.4
J2
2.541 ±1.014
20.7 ± 13.3
BETE P-54
1.38
B5
9.690 ± 0.548
8.2 ± 4.3
D3
9.203 ± 0.548
6.4 ± 2.1
E6
14.247 ±0.548
3.2 ± 0.5
G3
5.585 ± 0.548
4.8 ± 0.7
J2
2.246 ± 0.548
28.9 ± 25.2
$ Telltale placement designations illustrated in Figure 11 on page 61.
65
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TABLE 9. EXTINGUISHMENT RESULTS FOR A THREE-NOZZLE BETE PJ-40 SYSTEM
Manufacturer and
System operating
Telltale
Water flux,
Extinguishment times, s
Nozzle Type
pressure, MPa
placements
L/min-m2
BETE PJ-40
6.90
B3
1.920 ±0.361
9.3 ± 6.4
D4
3.866 ± 0.361
2.9 ± 0.5
E7
7.530 ± 0.361
6.2 ± 0.9
G8
9.824 ± 0.361
5.2 ± 1.7
H6
12.414 ±0.361
3.4 ± 1.4
BETE PJ-40
1.38
B4
1.289 ±0.361
5.4 ± 2.7
F7
3.507 ± 0.361
3.3 ± 1.3
G4
2.218 ±0.361
3.0 ± 0.2
H8
4.167 ±0.361
7.5 ± 4.0
13
1.912 ±0.361
3.9 ± 2.1
$ Telltale placement designations illustrated in Figure 11 on page 61.
TABLE 10. EXTINGUISHMENT RESULTS FOR A 14-NOZZLE BAUMAC MX-20 SYSTEM
Manufacturer and
System operating
Telltale
Water flux,
Extinguishment tir
Nozzle Type
pressure, MPa
placement!:
L/min-m2
Baumac MX-20
6.90
C8
3.335 ± 0.492
27.4 ± 13.7
C6
2.530 ± 0.492
15.1 ±8.5
D3
1.529 ±0.492
5.2 ± 1.5
G4
1.243 ±0.492
8.4 ± 2.9
12
0.884 ± 0.492
8.7 ± 5.9
Baumac MX-20
3.45
B8
2.124 ±0.357
33.5 ± 23.3
D5
1.222 ±0.357
18.0 ±12.1
F3
0.712 ±0.357
23.0 ± 30.5
13
0.725 ± 0.357
10.5 ±3.5
18
2.723 ± 0.357
14.6 ± 15.4
$ Telltale placement designations illustrated in Figure 11 on page 61.
66
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TABLE 11. EXTINGUISHMENT RESULTS FOR A 14-NOZZLE BAUMAC MX-8 SYSTEM
Manufacturer and
Nozzle Type
System operating
pressure, MPa
Telltale
placements
Water flux,
L/min-m2
Extinguishment times, s
Baumac MX-8
7.24
C5
0.734 ± 0.089
13.4 ± 15.9
E3
1.013 ±0.089
7.4 ± 2.3
F2
1.986 ±0.089
6.1 ±1.5
15
0.895 ± 0.0890
6.9 ± 2.2
K1
0.565 ± 0.089
41.7 ±29.1
Baumac MX-8
3.93
B5
0.619 ±0.052
60.8 ±51.9
E4
0.998 ± 0.052
28.8 ± 16.7
F2
1.462 ±0.052
9.4 ± 4.6
14
0.616 ±0.052
18.3 ± 11.3
K1
0.316 ±0.052
196.2 ±112.6
t Telltale placement designations illustrated in Figure 11 on page 61.
TABLE 12.
EXTINGUISHMENT RESULTS FOR A SINGLE-NOZZLE BETE PJ-40 SYSTEM
Manufacturer and
Nozzle Type
System operating
pressure, MPa
Telltale
placements
Water flux,
L/min-m2
Extinguishment times, s
BETE PJ-40
7.07
B6
0.996 ±0.156
11.4 ± 11.3
D8
1.320 ±0.156
8.9 ±6.1
F6
2.271 ±0.156
3.3 ±1.0
14
2.970 + 0.156
4.3 + 1.3
J2
2.120 ±0.156
5.9 ± 3.7
BETE PJ-40
1.38
B6
1.243 ±0.066
32.0 ± 26.0
D8
1.318 ±0.066
25.9 ± 17.6
F6
1.439 ±0.066
19.7 ± 12.6
14
1.750 ±0.066
17.1 ± 13.5
J2
0.970 ± 0.066
22.2 ± 18.4
t Telltale placement designations illustrated in Figure 11 on page 61.
67
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TABLE 13. EXTINGUISHMENT RESULTS FOR A SEVEN-NOZZLE BAUMAC MX-8 SYSTEM
Manufacturer and
System operating
Telltale
Water flux,
Extinguishment times, s
Nozzle Type
pressure, MPa
placement^
L/min-m2
Baumac MX-8
6.90
B6
0.385 ±0.014
171.1 ±79.3
D8
0.448 ±0.014
59.2 ± 44.7
F6
0.494 ±0.014
76.3 ± 47.4
14
0.539 ±0.014
48.7 ± 20.7
J2
0.471 ±0.014
85.7 ± 19.2
Baumac MX-8
3.45
B6
0.319 ±0.010
192.7 ± 105.1*
D8
0.345 + 0.010
98.8 ± 48.2
F6
0.346 ±0.010
111.2 ±37.9
14
0.415 ±0.010
63.2 ± 27.8
J2
0.389 ±0.010
107.4 ±41.5
* One of 10 telltales burned until it ran out of fuel.
t Telltale placement designations illustrated in Figure 11 on page 61.
TABLE 14. EXTINGUISHMENT RESULTS FOR A FOUR-NOZZLE BAUMAC MX-8 SYSTEM
Manufacturer and
Nozzle Type
System operating
pressure, MPa
Telltale
placement};
Water flux,
L/min-m2
Extinguishment times, s
Baumac MX-8
3.45
B6
0.257 ± 0.037
58.4 ±19.9
D4
0.359 ± 0.037
63.8 ± 28.0
F6
0.346 ± 0.037
50.2 ± 38.3
14
0.240 ± 0.037
73.8 ± 22.3
J2
0.169 ±0.037
129.6 ± 36.5
t Telltale placement designations illustrated in Figure 11 on page 61.
68
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TABLE 15. EXTINGUISHMENT RESULTS FOR A SINGLE-NOZZLE BAUMAC MX-8 SYSTEM
Manufacturer and
System operating
Telltale
Water flux,
Extinguishment times, s
Nozzle Type
pressure, MPa
placement^
L/min-m2
Baumac MX-8
6.90
B6
0.192 ±0.023
81.0 ±42.4
D7
0.631 ± 0.023
18.1 ±5.3
F6
0.315 ±0.023
16.2 ± 11.6
14
0.027 ± 0.023
56.0 ±41.5
J2
0.017 ±0.023
Burned out*
Baumac MX-8
3.45
B6
0.128 ± 0.021
138.8 ±53.2
D7
0.491 ± 0.021
102.3 ±34.4
F6
0.232 ± 0.021
82.0 ± 30.2
14
0.021 ± 0.021
139.5 ±60.3t
J2
0.011 ± 0.021
Burned out§
* Ten of 10 telltales burned until they ran out of fuel.
1 One of 10 telltales burned until it ran out of fuel.
§ Seven of 10 telltales burned until they ran out of fuel,
t Telltale placement designations illustrated in Figure 11 on page 61.
amounts of water (0.02 to 0.03 L/min-m2). Since a primary goal of a WMS is to suppress or extinguish fires with
minimal amounts of water, additional testing with one BETE PJ-40 nozzle (Table 12) and progressively fewer
Baumac MX-8 nozzles (Tables 14 through 16) was carried out to find the lowest effective limit of fire
extinguishment, referred to as the critical concentration.
Based on sales literature, the Baumac MX-8 nozzles were initially tested at 6.90 MPa with a nozzle spacing
of 15 to 18 cm. Droplet size analysis of the MX-8 nozzles at 6.90 and 3.45 MPa, measured at 40.6 cm below the
nozzle on the center line, showed the same droplet size distribution (Figure 15). Only the flow rate changed, ranging
from an average of 131.8 ± 3.2 gm/mirt at 6.90 MPa to 81.3 ± 2.0 gm/min at 3.45 MPa. Lowering the pressure and
repeatedly halving the number of nozzles and rerunning the water flux and extinguishment testing allowed the
determination of the minimum water flux required to extinguish the heptane telltales effectively.
The critical concentration or water flux for extinguishing heptane telltales with a WMS appears to be
0.60 L/min-m2. Increasing water fluxes above 0.6 L/min-m2 did not significantly decrease extinguishment times in
comparison to total water usage. Although water flux levels below this range were able to extinguish the telltales,
the extinguishment times became longer and more erratic (Figure 16). Extinguishment times for water fluxes
between 0.025 and 0.601 imin-m2 showed standard deviations on the order of their extinguishment times. Pooling
the variances and plotting them against median extinguishment lime for those extinguishment tests indicated that at
these water flux levels, the times required to extinguish the fires followed a Gaussian distribution and therefore can
69
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~—6.90 MPa
30 -
—3.45 MPa
25
a>
E
3
O
>
o
+—
c
<1>
o
o
0-
10
100
1000
1
Droplet Diameter, rricrometers
Figure 15. MX-8 nozzle droplet size distribution dependence on pressure at 40.6 cm.
240
220
200
180
W
a> 160
E
*z 140
c
0)
1 120
2
o> 100
c
2 80
60
40
20
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
Waler Flux. Umin-rre
Figure 16. Extinguishment times as a function of water flux for two Baumac nozzles.
! * MX-8
i ¦ MX-20
~ ~:
I *
¦
70
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be treated statistically (Figure 17). Further studies in this water flux range should elucidate the mechanism of fire
extinguishment with WM. Water fluxes below 0.025 L/min-m" did not extinguish the fires.
V)
-------
Optimum Nozzle. Layout for Room-Scale Testing
Table 16 shows representative data on (he effect nozzle spacing and layout have on extinguishing
unobstructed heptane telltales. Results are shown two different ways, the first two rows of data show the water flux
required of the different nozzle spacings to obtain essentially the same extinguishment times, while the next two
rowsof data show the effect on extinguishment time for a near constant water flux. Overall, the data indicates that
crowding the nozzles can have an effect opposite to that expected for fire extinguishment. The results show that as
the nozzle separation increased, the fires were extinguished either more quickly or more reproducihly while often
using less water. Table 16 indicates that nozzles spaced 40 cm apart and set in a rhombohedral pattern extinguish
the 5-cm diameter pan fire faster and more uniformly at a water tlux of 0.3 to 0.4 L/min-m2 than does the
manufacturer's nozzle array having a 15- to 18-cm nozzle spacing and a water flux of 0.3 to 0.6 limin-m2. During
discussions regarding this phenomenon, it was proposed that the WM at higher concentrations (crowding) coalesces
into larger drops. These larger drops fall straight down (rain out) and do not interact with the flame or, if above the
flame, fall through the flame. Whereas at lower concentrations, the smaller drops, in addition to falling into the fire,
can be swept into the side of the tire from a greater (relative) distance, thereby aiding extinguishment by horizontal
flame penetration and cooling at the flame/fuel interface. The distance the WM can be pulled into a fire will depend
on the fire size (draft) and the WM droplet size.
TABLE 16. EFFECT OF NOZZLE SPACING ON EXTINGUISHMENT FOR
BAUMAC MX-8 NOZZLES
Number of nozzles
14
7
4
1
Nozzle spacing, cm
15.2-19.0
40.6
40.6
Water flux, L/min-m2
0.619 ±0.052
0.415 ±0.010
0.359 ± 0.037
0.232 ± 0.021
Extinguishment time, s
60.8 ±51.9
63.2 ± 27.8
63.8 ± 28.0
82.0 ± 30.2
Water flux, L/min-m2
0.316 ±0.052
0.319 ±0.010
0.346 ± 0.037
0.315 ±0.023
Extinguishment time, s
196.2 ± 112.6
192.7 ± 105.1
50.2 ± 38.3
16.2 ± 11.6
To provide effective fire suppression for an entire room with a WMS where the placement of furniture and
obstructions are not known, the nozzle spacing design should yield a uniform water tlux coverage over the entire
protected space. The most efficient design for nozzles having a circular spray pattern is a rhombohedral patterned
array. In the seven-no/./le array system, the noz/.les were set in a rhombohedral pattern with a spray radius of 20 cm
(Figure 18). This radius was initially chosen because it allowed the most complete and uniform coverage for the
ATC stilling chamber.
72
-------
CM
E
c
E
13
a)
n
0.6-0.7
0O.5-O.G
¦ 0.4-0.5
n 0.3-0.4
~ 0.2-0.3
0.1-0.2
Sample Ftosition,
Width
5 6 7
Sample Fbsitfon, Depth
Figure 18. Water flux for a severvnozzle Baumac MX-8 array at 40.6 cm spacing.
Upon completing the extinguishment testing, additional water flux testing with four Baumac MX-8 nozzles
was conducted to optimize the nozzle spacing. Although the nozzle output varied, Figures 19 through 21 show that
a no/.zle spacing of 40.6 ± 5 cm yields the most uniform water flux pattern for large nozzle arrays, as demonstrated
by the uniform water flux rale for three of the four nozzles. As additional conformation, Figure 22 shows the water
flux for a single Baumac MX-8 nozzle which has an average 40-cm spray pattern at a water flux of 0.2 to 0.3 L/min-
m2 (similar to the four nozzle tests).
Proof-of-concept testing for this WMS at the room-scale level was based on a ceiling system designed as a
center-fed hexahedral array with a nozzle spacing of 40.6 ± 5 cm. Spacing adjustments were made to best fit the
array using these parameters.
Determination of Required Water Flux
Flow rate testing of the Baumac MX-8 nozzles indicated a water flux of 0.467 I./min-rn2 at 3.45 MPa for
the optimized nozzle spacing. Increasing the operating pressure to 6.90 MPa increased the water flow by 62 percent,
which should yield a water flux of 0.757 L/min-m2. While the target water flux level is below the 0.6 L/min-m2 level
where extinguishment could potentially be a problem when operating at 3.45 MPa, the system's capacity allows an
increase to levels where extinguishment should not be a problem (Figure. 16}.
73
-------
C\J
E
c
£
^1
X
3
LL
5>
IS
$
¦ 0.6-0.7
00.5-0.6
¦ 0.4-0.5
~ 0.3-0.4
~ 0.2-0.3
¦ 0.1-0.2
| E 0.0-0.1
K
Sample Fbsition,
Widlh
Sample Fbsition, Depth
Figure 19. Water flux pattern for a four-nozzle Baumac MX-8 array at 50.8 cm spacing.
CM
E
e
-------
CM
£
6
0)
<3
¦ 0.6-0.71
0 0.5-0.6;
¦ 0.4-0.5;
~ 0.3-0.4 |
~ 0.2-0.3
¦ 0.1-0.2
.00-0.1
Sample Position,
Width
6 7 8
Sample Position, Depth
9 10 n
Figure 21. Water flux pattern for a four-nozzle Baumac MX-8 array at 30.5 cm spacing.
0.7 - "
0.6-
CM
E
0.5-,
c
E
0.4
X
3
LL
0.3
§
0.2-
0.1
o-l
¦ 0.6-0.7
H 0.5-0.6
¦ 0.4-0.5
Q 0.3-0.4
~ 0.2-0.3
¦ 0.1-0.2
63 0-0.1
Sample Fbsition,
Width
Sample Fbsition, Depth
Figure 22. Water flux pattern for a single Baumac MX-8 nozzle at 3.45 MPa.
75
-------
Partially and Fully Obstructed Fires
Table 17 shows the results for extinguishment, testing of partially and fully obstructed heptane telltale fires.
A 53- by 60-cm board placed at approximately a 45-degree angle in the ATC stilling chamber covered a measured
floor area of 51 by 60 cm. Telltale B6 was centered at the back of the covered area, and Telltales D4 and D8 were
partially obstructed by being placed just inside of the covered area. Water-flux testing indicated that partial
obstruction reduced the WM concentration by approximately 60 percent. Increased coverage or distance from the
edge of the obstruction further reduced the WM by an additional 15 percent, for a total decrease from the original
concentration of 75 percent. Although these data are limited, they support the previous air flow data which indicate
that WMs major drawback in its potential to replace gaseous agents is its inability to turn or flow around corners.
TABLE 17. EXTINGUISHMENT RESULTS FOR AN OBSTRUCTED BAUMAC MX-8 SYSTEM
Manufacturer &
No. of
System operating
Telltale
Water flux,
Extinguishment
nozzle type
nozzles
pressure, MPa
placement^
L/min-m2
times, s
Baumac MX-8
7
3.45
B6
0.116 ±0.020
Burned out*
D8
0.191 ±0.020
183.2 ±52.1
D4
0.181 ± 0.020
226.8 ± 68.0
14
0.494 ± 0.020
77.3 ± 57.0*
J2
0.458 ± 0.020
101.9 ±42.0
" Five of 10 telltales burned until they ran out of fuel.
' One of 10 telltales burned until it ran out of fuel.
t Telltale placement designations illustrated in Figure 11 on page 61.
ROOM-SCALE TEST RESULTS
Intermediate Field-Scale Test Site
Based on the results of the laboratory-scale tests, a prototype operational system to generate and distribute
WMs over a larger volume was developed and tested in the NMERI Intermediate Field-Scale site chamber. The test
enclosure was made from a 2.4- by 2- by 6-m steel ocean shipping container with a 0.9- by 2.0-m personnel door at
the end of one side and large cargo doors that completely cover the opposite end (Figure 23 and Figure 24). A steel
partition was placed in the center of the container, essentially dividing it in half. One half is used as the Test
Chamber while the other half is the Agent Filling and Equipment Storage Room. The steel partition dividing the
ocean shipping container is equipped with a 0.6- by 0.6-m camera view port (12.7-mm thick clear Lexan) and pipe
penetrations to provide inlets for the fuel and agent, pressure transducers, thermocouples, and sampling probes.
76
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Figure 23. Exterior view of the NMERI Field-Scale Test Chamber.
EXHAUST FAN
FIRE TEST ENCLOSURE
Figure 24. Interior layout of the NMERI Field-Scale Test Chamber.
77
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The internal dimensions of the lest chamber are 2.4 m high by 2.4 m wide by 3.2 m long for an internal
volume, of 18.3 m3. The test chamber is equipped with an automatic ventilation system that can be used to sustain
the internal oxygen concentration to support combustion during agent testing. The ventilation system includes a
motorized exhaust fan and two motorized dampers. Data acquisition and equipment control are accomplished with a
National Instruments Lab Windows software-based 486DX33-MHz PC data acquisition and control system
(DA/CS). There were eight sensor input and eight output control circuits. Test data can be displayed on screens in
real time for quick viewing and interpretation of results.
Although neither required nor used for this phase of the testing, WM concentrations can be obtained
gravimetrically. Combustion products inside the test chamber can be measured during each test should additional
follow-on testing be desired. The combustion products sampling system consists of a Perkin-F.lmer System 2000
ITIR Spectrometer 486DX33-MHz PC, 1.2 m of quartz sample tubing, a 10-cm glass gas cell, a vacuum pump,
flowmeters, and miscellaneous tubing. Products which can be measured included CO, CO?., COF3, HF, and HC1.
Room-Scale Testing of the Water Mist Fire Suppression System
A ceiling array of 53 Baumac MX-8 nozzles, set in a rhornbohedral pattern with a 39.4-cm nozzle spacing
on a 30.5-cm pipe run, provided the most complete and uniform coverage for a 3.18- by 2.34-m room (Figure 25).
Since this was a proof-of-concept test series with regard to fire suppression/extinguishment, no rigorous pipe friction
or pressure loss study was conducted on the 12.5-mm outside diameter 304 stainless steel pipe used in the test nozzle
array. Friction losses were assumed to be negligible, and no compensation was made for altitude, since only the
oxygen level at which combustion cannot be supported is significant and would not change with altitude. Normal
atmospheric pressure is 17 percent lower in Albuquerque, NM, where the testing occurred, than at sea level. Water
was supplied to the nozzle system by a 1.08-mVhr high-pressure metering pump capable of 10.3 MPa developed
pressure and controlled by a 60-Hz AC variable speed controller. The nozzle array was fed from the center to
minimize pressure differentials and losses. The metering pump and water supply system were in the adjacent spaces.
The WMS testing used the same obstructions, 7.6-cm diameter heptane-fueled telltales, pool fire pans (21.0
and 45.7 cm), and wood cribs normally used for halon and halon replacement testing. All pans and telltales were
10.2 cm tall with 5.1 cm of water and 2.5 cm of heptane. The obstruction feature used in this testing is open on top
and only partially open on the sides (10 to 15 percent of the sides are open), since the halon replacement test nozzle
directs the gas/liquid stream horizontally along the top of the test chamber, and the momentum carries the vapor
down the walls and back across the floor (Figure 26). Under halon replacement test conditions, obstruction from the
sides was considered more important. Since this test apparatus allows WM to fall into it but restricts the WM
entering from the sides, the obstruction feature was considered a partially obstructed fire in these tests where the pans
were centered near one side of the obstruction feature. Table 18 lists the test scenarios used during the proof-of-
conccpt testing for the Baumac MX-8 nozzle-based WMS.
78
-------
Water Supply
Excess Recycled
Spray Pattern Coverage
from the Individual Nozzles
3.18 m
Motor Metering
Controller Pump
Pressure
Regulator
and
Flowmeter
2.34 m
Nozzle Array
Forced Air Exhaust
Intake Air
Louvered Vent Louvered Vent
Figure 25. Baumac MX-8 System layout for room-scale testing.
¦1/2 Wood Crib
— j— —j -
123 cm
pen Areas (Slits)
•Pool Fires
79 cm
93 cm
Front View
Side View
Figure 26. Partially and fully obstructed fire test feature.
79
-------
TABLE 18. ROOM-SCALE TEST SCENARIOS FOR THE BAUMAC MX-8 WATER MIST
FIRE SUPPRESSION SYSTEM
Test scenario
Conditions
Fuel
Pool fire size, kW
Repeats
1
Unobstructed with telltales
Heptane
32
6
2
Reignition
Heptane
32
2
3
Partially obstructed
Heptane
32
2
4
Partially obstructed with telltales
Heptane
292
3
5
Cabinet
Heptane
32
1
6
Partially obstructed
Paper
4
7
Partially obstructed
1/2 Wood crib
3
8
Unobstructed
1/2 Wood crib
2
The results of the room-scale extinguishment testing for Class B heptane pool fires are listed in Table 19.
For scale-up comparisons between the ATC and the room-scale data, Table 14 data represent the same nozzle
separation and pattern as used in the room-scale testing. An unobstructed 32 kW heptane pool fire was extinguished
in 1 min 40 ± 34 s using on average 5.7 L of water (Figure 27). Partially obstructing the 32 kW fire, at least from the
sides, increased the extinguishment time to 5 min 15 s, requiring the use of 17.9 L of water (Figure 28). This three-
fold increase in time indicates the relative importance of getting the WM into the flame/fuel interface from the sides
of the fire. Since WMS are designed to utilize small droplet sizes, which evaporate quickly, and to extinguish fires
with minimal water usage, penetration and cooling of the fire from above is inefficient as demonstrated by those
data. WM requires access to the flame/fuel interface to suppress and extinguish fires effectively, which was
demonstrated again for the single test of a closed cabinet for which the top was covered and there was 10 to
15 percent open area (slits) along three sides. Access to the flame/fuel interface from the side through the slits in the
cabinet allowed the WM to extinguish the fire. This fire extinguishment took 8 min 32 s and required the use of
29.1 L of water (Figure 29). Oxygen depletion was not a factor in the cabinet test, since the same conditions run
without WM consumed the fuel in 23 min 15 s. Although the Baumac MX-8 nozzles are considered low momentum
and the distance to the surface of the pool fires was 2.1 m, the WM flattened the plume and distorted it to the sides of
the pan. This often put the fire pan thermocouple (TC), which was 5 cm above the initial heptane surface, outside of
the fire plume.
One of the goals of an ideal halon replacement is the ability to inert the protected space and/or prevent
reignition after the fire has been extinguished. The WMS was tested for its ability to prevent reignition (after the fire
was extinguished) of both unobstructed and partially obstructed heptane pool fires in the protected space. Testing
was initially conducted with regard to the time the system could delay reignition and, subsequently, whether a
continuously operating system could protect against reignition. In Table 19. Test 5A was the only test for reignition
80
-------
TABLE 19. ROOM-SCALE CLASS B (HEPTANE) EXTINGUISHMENT TESTING OF THE BAUMAC MX-8 WATER MIST SYSTEM
Test
number
Test
scenario*
Conditions
Fire size,
kW
Preburn,
min:sec
Extinguishment
time, min:sec
Water pressure,
MPa (gauge)
Water flow rate,
L/min
Application rate,
L/min-m2
1
1
Unobstructed
32
1:00
1:39
3.45
3.41
0.46
2
1
Unobstructed
32
1:00
1:07
3.45
3.41
0.46
3
1
Unobstructed
32
1:00
1:47
3.45
3.41
0.46
4
1
Unobstructed
32
1:00
1:00
3.45
3.41
0.46
5
1
Unobstructed
32
1:00
2:32
3.45
3.41
0.46
6
1
Unobstructed
32
1:00
1:53
3.45
3.41
0.46
5A
2
Reignition/Water Off
32
1:38
0:10
3.45
3.41
0.46
6A
2
Reignition/ Water On
32
0
0:15
3.45
3.41
0.46
6B
2
Reignition/ Water On
32
0
1:19
3.45
3.41
0.46
6C
2
Reignition/ Water On
32
0
0:21
3.45
3.41
0.46
6D
2
Reignition/ Water On
32
0
0:43
3.45
3.41
0.46
6E
2
Reignition/ Water On
32
0
0:46
3.45
3.41
0.46
11
3
Partially Obstructed
32
1:00
5:15
3.45
3.41
0.46
12
3
Partially Obstructed
32
1:00
4:52
6.90
5.30
0.71
13
4
Partially Obstructed
292
1:00
0:27
3.45
3.41
0.46
14
4
Partially Obstructed
292
1:00
0:15
3.45
3.41
0.46
15
4
Partially Obstructed
292
1:00
0:16
3.45
3.41
0.46
21
5
Obstructed Cabinet
32
1:00
8:32
3.45
3.41
0.46
* As defined in Table 18.
-------
700
600
500
O
| 400
(5
a
E 300
o
h-
200
100
-61 cm High TC
- Telltale No. 1 TC
Fire Pan TC
TeBtale No. 6 TC
—t——; t : r^V-v i i '
c? S 8 8 8 co
o
c\i
o
CVJ
OU CVJ <*3
Water Mist System Operating Time, s
o
CVJ
•«*
S
Figure 27. Temperature variation at four locations as a function of operating time
for an unobstructed 32-kW heptane pool fire subjected to WM.
700
-~— 61 cm High TC
¦m— TeBtale No. 1 TC
; Fire Ran TC
Teltale No. 6TC
600
500
O
o
Q>
400
D.
E 300
m
H
Reig'nitibn
200
100
o
O)
o
co
o
ID
CD
m
CM
OJ
in
o
oo
o
Wayer Mst System Operating Urne, s
Figure 28. Temperature variation at four locations as a function of operating time
for an obstructed 32-kW heptane pool fire subjected to WM.
82
-------
700
«— 61 cm High TC
B— Telltale No. 1 TC
: Fire Ran TC
- Telltale No. 6 TC
600
500
p
0)
400
"is
i
E
®
h-
300
200
100
> i
R
§
8
o
IT)
Water Mst System Operating Time, s
Figure 29. Temperature variation at four locations as a function of operating time for
an obstructed (cabinet) 32-kW heptane pool fire subjected to WM.
after the water was turned off. Since the pool fire igniter utilizes 10,000 volts, safety protocols required exiting the
lest building after shutting off the WMS before igniting the heptane pool fire. The initial spark, at 10 s after the
WMS was turned off, rcignited the heptane pool fire in the presence of the WM. Subsequent reignition testing with
the W.MS operating showed that at a water flux rate of 0.46 L/min-m\ the system did not protect the space from
reignition (Figure 30). Although the WM was unable to inert the space, it was able to repeatedly extinguish the fire
in time, averaging 41 ± 25 s for five repeat extinguishments. Additionally, although the fire relit with the WMS
operating, the temperature immediately above the flame was reduced by the WM for an unobstructed fire
(Figure 30). This is in contrast to the partially obstructed fire, which showed a rebound to near initial temperature
conditions (Figure 28).
Table 20 shows extinguishment results for the 7.6-crri diameter heptane-fueled telltales tests conducted
during the unobstructed 32 kW heptane pool fires (tests I - 4) and the partially obstructed 292 kW heptane pool fires
(tests 13 - 15). The telltales were placed in all corners of the room with the upper telltales 15 cm below the nozzles
array and 11 cm behind the nearest nozzle (Figure 31). Since not all telltales could be monitored with thermo-
couples, operating times of the WMS prior to shutting down to check the telltales were arbitrary. Tests 1 through 4
indicated that between 2 to 3 min were required to extinguish the majority of the telltales. The inability to extinguish
the upper telltales, particularly 7 and 8, appears to be due to their position relative to the wall and nozzles. The WM
83
-------
700
—61 cm High TC
Fire Pan TC
600
500
Ificignition
amepuf
S 400
I 300
200
100
~~W ^T"
o
o
CD
O
cn
O
oo
O
o
o
in
O
cn
o
CM
O
CO
o
CM
o
o
o
CD
o
CD
Water Mist System Operating Time, s
Figure 30. Temperature variation at two locations as a function of operating time for
multiple reignitions of a 32-kW heptane pool fire subjected to WM.
TABLE 20. ROOM-SCALE TELLTALE EXTINGUISHMENT WITH THE BAUMAC MX-8
WATER MIST SYSTEM
Test
Test
Operating time,
Telltales extinguished
Total
number
scenario!
min:sec
1
2
3
4
5
6
7
8
1
1
7:45*
Out
Out
Out
Out
Out
Out
No
No
6
2
1
5:00
No
Out
Out
Out
Out
Out
No
No
5
3
1
3:00
Out
Out
Out
Out
Out
Out
No
No
6
4
1
2:00
No
No
Out
Out
No
Out
No
No
3
13
4
4:00*
Out
Out
Out
Out
Out
Out
Out
Out
8
14
4
3:00
Out
Out
Out
Out
Out
Out
Out
Out
8
15
4
2:30
Out
Out
Out
Out
Out
Out
Out
Out
8
t As defined in Table 18
* Upper comer telltales (1-4) were 15 cm below and 11 cm behind the nozzles, tight to the walls.
+ Telltales moved 3 cm away from the walls.
84
-------
5
6
8
1
3
4
Figure 31. Telltale position and numbering for room-scale testing.
exiting the nozzle forms a tight cone for the first 10 to 15 cm. which would place the telltales outside any WM spray
coming from any nozzle. l"he only mist reaching these telltales would have been recycled around the room.
Additionally, the 2.5-cm distance between the top of the telltale and the heptane made it extremely difficult for WM
to get to the flame/fuel interface from below in such a small diameter cylinder. Moving the ceiling telltales 3 cm
away from the wall appeals to have been adequate to allow additional access to the WM spray from above as
indicated by the results of Tests 13 - 15.
The two Class A fire extinguishment test scenarios involved (1) shredded paper in a 31-cnr wastepaper
basket and (2) the XMERI 1/2 wood crib. Temperature monitoring for the wastepaper basket consisted of a
thermocouple placed in the geometric center of the basket, a thermocouple centered 61 cm above the basket, and
thermocouples in both a floor corner (TCI) and a ceiling corner (TC6). The wood crib was constructed of
25 Douglas fir boards (3.65- by 3.65- by 50.8-cm) layered cross-wise and stacked 5 high with five boards in each
layer. The final wood crib size (50.8- by 50.8- by 18.6-cm) was placed 46 cm above a 61 - by 61 -cm heptane pool
fire. The heptane pool fire ignited the wood crib and exhausted its fuel before the crib preburn time was finished and
the WMS started. Exhaustion of the heptane fuel prior to discharge of WM is desired. Temperature monitoring
consisted of a thermocouple located 7 cm above the heptane pool fire, a second thermocouple 7 cm above the wood
crib, and two thermocouples in Corners 1 and 6.
In the initial Class A shredded-paper extinguishment test, the thermocouple was placed just above the
paper and level with the top of the wastepaper basket. The fire appeared to be extinguished in 18 s. However,
shutting down the WMS after 1 min of operation allowed the fire to smolder and reignite. To test for extinguishment
of deep-seated fires during the remaining paper fire tests, the thermocouple was placed in the geometric center of the
wastepaper basket and the fire was not considered fully extinguished until the thermocouple temperature returned to
40 ± 5 =C or below (Table 21). Operating the WMS for 1 min past reaching the 40 ± 5 °C level extinguished the
fire, leaving the remaining paper wet and unable to be reignited. During the extinguishment test at 6.90 MPa, the
85
-------
nozzles on both sides of the nearest overhead nozzle plugged-up. In spite of this plugging, the WMS easily
extinguished the fire. The temperature traces for the shredded paper fires show the relative position of the
thermocouple with respect to the flame front. The temperature rises as the fire burns past the thermocouple
(Figure 32). The traces indicate, that WM has difficulty penetrating deep-seated fires at an application rate of
0.46 L/min-m2. The fire in Test 9 was not extinguished until the fire consumed greater than 50 percent of the paper,
thereby opening a path for the water to enter and extinguish the fire. Without addition of WM. burning the
equivalent amounts of paper indicated a 10-min burn before the flame died down.
TABLE 21. ROOM-SCALE CLASS A EXTINGUISHMENT TESTING OF THE BAUMAC MX-8
WATER MIST FIRE SUPPRESSION SYSTEM
Conditions
Fuel
Preburn,
Extinguishment
Water
Water
Application
minrsec
time, min:s
pressure,
MPa
flow rate,
L/min
rate,
L/min-m2
Wastepaper
Paper
1:00
0:18
3.45
3.41
0.46
basket
Wastepaper
Paper
1:00
4:00
3.45
3.41
0.46
basket
Wastepaper
Paper
1:00
10:00
3.45
3.41
0.46
basket
Wastepaper
Paper
1:00
3:15
6.90
5.30
0.71
basket
Partially
Small wood crib
1:30
0:30
6.90
5.30
0.71
obstructed
Partially
Small wood crib
2:00
0:33
3.45
3.41
0.46
obstructed
Unobstructed
Small wood crib
2:00
0:27
3.45
3.41
0.46
Unobstructed
Small wood crib
4:00
0:45
3.45
3.41
0.46
Table 21 lists the extinguishment results for both partially obstructed and unobstructed wood crib fires. The
partially obstructed fire used the same obstruction feature as the partially obstructed pan fires except that the crib
was placed 46 cm above the base of the feature. The unobstructed wood crib fires were run with an operating PC
and a shelf of books and newspapers across the room from the fire during the extinguishment (Figure 33). Most of
the damage to the PC was caused by smoke and heat, with the WM forming only a thin film on the computer. The
film evaporated quickly after the WMS was shut down. The computer operated throughout the extinguishment test.
No noticeable film of water was detected on the books; the only effect from the fire was soot, which was easily
cleaned off the book covers.
86
-------
Water Mist System Operating Time, s
Figure 32. Temperature variation at the geometric center of a basket containing
shredded paper as a function of operating time for a fire subjected to WM.
Books
Computer
on Cart
1.14 m 1.42 m
1/2 Wood
Crib
"Heptane Pool Fire
Figure 33. Room layout for unobstructed 1/2 wood crib fires.
87
-------
Post-1'ire Storage and Operation of the Personal Computer
After exposure to the fires and subsequent WMS discharges, the PCs were stored in a room maintaining 65
to 70 percent relative humidity without any maintenance or cleanup. After 90 days the PCs continued to remain
operational; inspection of the interior components indicated no corrosion or water damage. Cleaning of the cases
was the only requirement to put the computers back in normal service.
SUMMARY OF FINDINGS ON MECHANISMS OF FIRE EXTINGUISHMENT
The beginning of this section listed six areas of investigation, which would be worthwhile to incorporate as
part of the program for the development of a WMS. Although the project docs not completely answer the questions
posed, it does shed additional light on these areas.
1. The critical concentration was initially defined as the total mass of water in droplets per unit volume
required to extinguish various classes of fire. While laboratory-scale testing (Table 15) showed that
very small water fluxes can extinguish a heptane fire (0.02 to 0.03 L/min-m2), the project showed that
there is a more important "concentration" relative to fire extinguishment. A better definition for the
critical concentration, in hindsight, might be the effective fire extinguishment water flux and would be
represented by the minimum water flux where extinguishment times versus water flux becomes a
constant. For heptane fires, this flux would be 0.6 L/min-m2 (Figure 16). It is at this point that fires
are extinguished quickly, but with the least amount of water and water-related collateral damage.
2. Unfortunately, the inability of the ATC, as designed, to permit extinguishment of fires reliably,
stopped most of the work on the questions of droplet size, size distribution and droplet velocity effects
on fire extinguishment. Possible follow-up projects may provide answers to these questions now that
a water flux testing range (0.02 to 0.6 L/min-m2) has been determined for this investigation (Figure
16). Although this water flux range was able to extinguish the heptane fires, the extinguishment times
showed standard deviations on the order of their extinguishment times. Pooling the variances and
plotting them against median extinguishment times showed that the extinguishment of the fires follow-
ed a Gaussian distribution and therefore could be treated statistically. Since extinguishment of the
fires is border line in this water flux range, changes in drop size, size distribution and droplet velocity
should show the greatest effects on fire extinguishment for heptane fires in this water flux range.
3. The WM extinguishment testing using a high-momentum Grinnell AM-1 1 nozzle showed a very
narrow directed flow which did not spread out in the ATC's stilling chamber. In spite of a water flux
of nearly 2 L/min-m2, the nozzle had difficulty or was unable to extinguish fires near the corners of the
chamber (positions J10 and J2 in Table 8). Additionally, the majority of the WM generated in the
ATC's stilling chamber did not leave the chamber in spite of air flowing through the chamber at
88
-------
4.53 m3/min (Figures 12-14). The testing of high momentum (velocity) nozzles and the inability of
the ATC intake and exhaust fans to distribute the WM have shown that droplet velocity is not a major
factor in extinguishment. If the drop velocity only aids in getting the WM to impinge on the surfaces
opposite to the nozzles, then the WMS will be less efficient regarding fire extinguishment.
4/5. The early ATC data and the water flux data obtained from the stilling chamber indicated that WMs arc
substantially line-of-sight extinguishants, at least for the drop size ranges tested. The limited data
obtained from the ATC testing indicates primarily that only the smallest drops are able to turn corners
and extinguish the fires (Figures 12 -14). Testing of nozzles that produce WMs of less than 50 ,um,
30 Mm, 20 pm, etc., may determine a drop size range where WM can act like a total-flooding agent
and effectively How around corners and obstacles.
6. At the water flux rate tested (0.46 L/min-m2) in the room-scale experiments, the WM was able to
suppress and extinguish fires, but was unable to inert the space (pool fires were reignited using an
electronic spark, Table 19). Since increasing water flux rates for these nozzles had the opposite effect
on extinguishment times, droplet size and distribution may be more important then the amount of
water for inerting a space.
Additional findings from the laboratory- and room-scale testing;
1. Water flux testing of nozzle arrays gives a reproducible determination of the water flux pattern over
the entire protected space. This also allows a determination of the spacing between nozzles which
give the most uniform (desired) water flux pattern over the entire protected space (Figures 18 through
21). A uniform water flux pattern was choosen for testing since it would represent the minimum water
flux versus extinguishment time for a room where the content placement was unknown.
2. Although the data in Figure 16 indicated 0.6 1,/rnin-m2 was the most effective water flux that would
extinguish the fires with a minimum amount of water and time, the room-scale testing was not done at
0.6 L/min-m2, since the demonstration of scale-up from laboratory- to room-scale at 0.46 L/min-m2
was considered a more important finding or result for the WMS demonstration. Additionally, though
there was no direct attempt to exactly match room and laboratory tests, scale-up from laboratory to
room testing appears straight forward. As an example, the floor room-scale telltales, in spite of the
heptane levels being 2.5 cm below the top of the lellltale and not being able to monitor all the telltales
individually during the tests, were normally extinguished in 120 to 150 s or less at a water flux of
0.46 L/min-m2 (Table 20). This compared favorably with the laboratory-scale testing on 5-cm
diameter telltales that showed an average extinguishment time of 84 ± 41 s at a similar water flux
(average 0.48 L'min-m2).
89
-------
As with the laboratory-scale tests, the room-scale testing also demonstrated that increasing rhe water
flux from 0.46 L/min-m2 to 0.71 L/min-nV had a greater impact on the water usage (+41%) than it did
on decreasing the extinguishment time (-7%).
Finally the room-scale testing showed that a WMS design, based on laboratory tests, would
successfully extinguish a variety of room-scale fires.
90
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SECTION 7
QUALITY ASSURANCE
INTRODUCTION
This section of the report outlines the quality assuance (QA) activities. Particularly the data quality
indicator (DQI) results obtained for the initial test method and outlines the approach taken to obtain data of known
and adequate quality for the alternative Lest method developed when it became apparent the ATC was unable to
reliably extinguish the 5-cm heptane pool fires as proposed in the experimental program test plan.
QUALITY ASSURANCE SUMMARY
All data quality goals for the initial test method using the ATC were achieved should follow-on work wish
to revisit this technique. Although the alternative test method was not submitted for QA review, sufficient repeats of
each test were conducted so as to yield statistically meaningful results.
Other then deciding to set aside the initial test method when it became apparent the ATC could not
reproducibly extinguish the heptane fires as designed, the quality assurance project review team place no limitations
on the data generated during this project. Additionally, there were no audits either internal or external conducted
during this Category TV project.
DATA QUALITY INDICATOR GOALS
Initial Test Methods
DQI goals proposed for the initial test program for the measured information collected to assess
appropriateness of WMS arc listed in Table 22. The objective was to ensure that all data colleclion or measurement
activities yielded data of known and adequate quality sufficient for the intended use.
Table 22 lists the significant data proposed for collection from the ATC for this project and provides DQI
goals for precision, accuracy, and completeness. The known or expected ranges for specific values are included in
Table 22. The DQIs were estimates based on the accuracy of the measuring instruments purchased and were tested
and redefined during method validation.
91
-------
TABLE 22. SUMMARY OF COLLECTED DATA AND GOALS FOR PRECISION, ACCURACY,
AND COMPLETENESS
Measurement parameter
(units)
Reference
Experimental
condition
Expected precision
(rel. std. dev.)
(%)
Expected
accuracy
(% bias)
Completeness
(%)
Mist concentration
Expected*
Gravimetric
15
10
90
Air flowf
Expected*
NMERI ATC
15
10
90
Temperature
Expected*
NMERI ATC
6
3
90
Relative humidity
Expected*
NMERI ATC
6
3
90
Water flow
Expected*
NMERI ATC
4
2
90
Fraunhofer instrument
Expected*
NMERI ATC
6
10
90
Room-scale testing
(50)
NMERI Field-
Scale Test Facility
5
10
90
* For the Aerosol Test Chamber (ATC) as built. The instrumentation for aerosol size measurement was based on Fraunhofer
diffraction theory. Based on a review of the literature regarding FD methods, including analytical instruments presently in
use, such as the Malvern, precision and accuracy were expected to be 3 and 5 percent, respectively. Listed goals took into
consideration losses due to errors from measurements of droplet concentration in moving air streams. Method
development incorporated statistical analyses to document instrument and system operation and repeatability as well as
method validation.
t Operation of the ATC at air flows above 0.5 m/s will yield results within the expected precision desired for these
measurements.
Alternative Test Method
The water-flux testing was cheeked for reproducibility by repeating the testing of two vertical and two
horizontal rows three times to determine the statistical variances of the measurements. Extinguishment testing
utilized a minimum of three repeats at the high water flux rates and 10 repeats for the lower WM ilux rates (Baumac
nozzle data) to determine the statistical variances of the measurements. The standard deviation formula used was
calculated based on the nonbiased or n-1 method.
DATA QUALITY INDICATOR RESULTS
Introduction
Although the ATC did not perform as initially planned, the data quality goals for those variables determined
before this approach was halted are included. Should follow-on testing develop from this project, the ATC may be
revisited and modified to allow all or parts of it to be used in future testing.
92
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Mist Concentration
A limited amount of ATC testing was completed for gravimetrically determining WM concentrations. The
initial goal was to determine whether the procedure would yield reproducible results. Operation and testing with the
ATC would then yield the operating range over which this sampling method would operate. Tabic 23 lists the test
results for the gravimetric WM concentration method described below. Relative standard deviations (RSD), as
described in the NRMRL QA procedures manual, versus WM concentrations average just under 10 percent, which is
less then the expected value of 15 percent for this data quality indicator.
TABLE 23. SUMMARY OF WATER MIST TEST CONDITIONS
Test conditions
Series 1
Series 2
Series 3
Series 4
Series 5
Series 6
Intake airflow, 10'2m3/s*
4.25
4.25
4.72
4.72
5.19
5.19
Water pressure, MPa
6.90
6.90
5.17
6.90
2.76
2.76
Water flow, 10"4m3/s
2.018
2.018
1.703
1.956
1.199
1.199
Water pump setting, Hz
40.6
40.6
33.5
39.7
24.3
24.3
Water mist concentration, g/L
Sample 1
0.0187
0.0241
0.0186
0.0245
0.0176
0.0167
Sample 2
0.0212
0.0232
0.0166
0.0231
0.0193
0.0186
Sample 3
0.0193
0.0231
0.0216
0.0222
0.019
0.0176
Sample 4
0.0158
0.0225
0.0174
0.0212
0.0182
0.0174
Sample 5
0.0156
0.0211
0.0149
0.0229
0.0166
0.0162
Sample 6
0.0183
0.0212
0.0198
0.0163
0.0149
Sample 7
0.0168
0.0266
0.0147
0.0150
Sample 8
0.0187
0.0223
Sample 9
0.0190
Average concentration, g/L
0.0182
0.0228
0.0183
0.0228
0.0174
0.0166
Standard deviation, g/L
0.0021
0.0011
0.0022
0.0021
0.0016
0.0014
RSD, %
11.54
4.82
12.02
9.21
9.20
8.43
* At ambient (room) temperature (22 UC) and pressure (83 kPa).
WM concentrations for each test condition during operation of the ATC were to be obtained and
determined. The gravimetric method developed to obtain the mist concentrations from the flowing aerosol streams
follows:
93
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1. To determine the volume of the vacuum flask and therefore the volume of air pulled through the
drying tube, the following procedure needs to be carried out (once) for each flask used. Set the round
bottom vacuum flask upright on a cork ring (Figure 34). Using 20 °C water in a to deliver (Tl>) at
20 °C appropriately sized graduated cylinder, fill the round bottom flask to the level of the rubber
stopper and record the amount required, i.e., the volume used in calculating the WM concentration.
Rubber Stopper Vacuum Tubing
Five-Liter Vacuum Flask Vacuum Gage Needle Vclve Drying Tube
Figure 34. Water mist collection apparatus.
2. Cap one end of the drying tube, load the drying tube 3/4 full with a molecular sieve material, add a
gauze separator, fill with drierite, and cap the remaining end. Be sure the end covers are in place at all
times since the drierite will pick up moisture from the air. Note: Since this procedure measures small
masses of WM on an analytical balance, gloves need to be used at all times to prevent including the
moisture transferred from the operator's hands.
3. Complete the assembly of the WM collection apparatus minus the drying tube (Figure 34).
4. Use an analytical balance to determine the mass of the drying tube and record it.
5. Connect the WM collection apparatus assembly to a vacuum hose attached to a vacuum pump. With
the needle valve open, evacuate the flask and then close the needle valve. (The vacuum used in the
tests was 635 mm of Hg which was the limit of the vacuum pump and corresponded to an absolute
pressure of 12.9 kPa). Remove the WM collection apparaius assembly from the vacuum pump,
remove the end cover from the desiccant end of the drying tube, and attach the drying tube to the
vacuum hose on the WM collection apparatus assembly.
6. Remove Ihe rubber stopper from the gravimetric WM sample port on the ATC, just above and in front
of the 1;D detector position being scanned or tested, remove the end cover from the drying tube, and
insert the drying tube end of the WM collection apparatus into the gravimetric WM sample port. (Do
94
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not collect a sample while a FD scan is being taken). Open the needle valve slowly, attempting to
draw the WM sample in at an even rate over approximately 30 s.
7. Remove the WM collection apparatus, replace the end cover on the drying tube, and replace the
rubber stopper in the gravimetric WM sample port on the ATC.
8. Remove the drying tube from the WM collection apparatus, replace the remaining end cover on the
drying tube, dry off the water collected on the outside of the drying tube, determine mass with an
analytical balance and record.
9. Steps 4 through 8 can be repeated with the same drying tube until the desiccant starts to change color
(blue to pink). The drying tube then needs to be recharged with fresh molecular sieve and desiccant at
this point.
10. Calculation for the determination of WM concentration:
(final drying tube mass, g - initial drying tube mass, g)/Volume, L - Cone., g/L (1)
Example: (23.2937 g - 23.1968 g)/5.380 L = 0.0180 g/L
Air Flow
The ATC displayed in Figure 10 shows, on the left side view, the air intake duct, which supplies all the
makeup air for conveying the WMs through the test chamber. Air flow measurements for controlling the mist/air
mixture velocity through the ATC are monitored continuously using a Model KM-4107 thermal anemometer for
measuring air flow velocity in the air intake duct to the ATC. The duct has a 0.092 m2 cross sectional area,
measuring 40.7 by 22.8 cm and allowing a direct proportion conversion to air flow rate (i.e., air flow rate equals
cross sectional area times air velocity). This type of instrument was the only one found that allowed accurate
measurements at the low air flow rates desired for this test apparatus. Figure 35 shows the layout of the measuring
pattern. Air flow measurements were taken every 5.1 cm at the intersection of the traverse lines and were used for
determining the average air flow across the duct and for determining where to place the thermal anemometer to get a
continuous average reading of air flow in the duct during the test runs.
All air flow testing used room air at 22 °C and at 83.1 kPa. Initial air flow testing indicated that there was a
significant side-to-side differential in air flow across the duct (Figure 36). The addition of a standard home foam air
conditioner filter eliminated this differential and enabled a uniform air (low in a duel (Figure 37).
95
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S5
S3
S1
Figure 35. Traverse lines for airflow measurement in the intake duct.
Figure 38 summarizes the air flow analyses for determining the placement of the anemometer in the intake
air duct for continuous monitoring of the air flows during testing and indicates that the standard deviation for the
measurements is of the same order as the step increment of the instrument (e.g., average standard deviation of
0.0047 nvVs [ 10.3 cfm] and reading increments of 0.0049 m'/s [ 10 cfm]). These results agree with the
manufacturers' specifications of:
Air velocity range: 0 to 30.4 m/s (0 to 6000 ft/min)
Air velocity accuracy: ± 3 reading
± 1 full scale
Resolution: 0.05 m/s (10 ft/min)
At very low air flows, the resolution of the instrument nearly equals the air flow and standard deviation of
the measurement. As air velocities increase, the percent relative standard deviation decreases and approaches the
15 percent expected at about 0.5 m/s (90 ft/min) (Figure 39). Operation of the ATC at air flows above 0.5 m/s
(90 ft/min) will yield results within the expected precision desired for these measurements.
Temperature and Relative Humidity
Temperature and relative humidity measurements were used in this test system only for control purposes
(i.e., for monitoring whether the fire suppression tests were run under repeatable test conditions). For temperature
and relative humidity measurements, the Vaisala Humitter 50 integrated relative humidity and temperature
transmitters (factory calibrated) were employed. Specifications for the transmitters are:
Operating range (for which accuracy is specified): 10 to 90 percent relative humidity (RH)
Accuracy at +'20 °C: ±3% RH
Stability: ±2% RH over 2 years
Temperature dependence: <±2% from -10" to +60 °C
96
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Dote: 17-Jun-94
Fen Setting: 0.25% of Fu'1 Speed
Air Flew Test No. 15
T ech: Glenn Matte on
Exhaust Fen S effing: Off
Water: Off;
Air T errperature: 22 C;
Air Pressure: 0 .084 MP a
SI
S2
;Test Positions
S3
S4
0.0
o.o.
0.01
0.0
_o.o"
o.o"
0.3
0.3'
0.0
0.3
jd.o
0^0
0.0
0.3
0.6
0.8'
0.3
0,3
0.3:
0.6
0.6
Average
StdDev
Ma<
M:n
0.8
1.1_
08
0.7
0,7
2.3
0,0
0.8-
0.8-
Damper Setting 0.125 % Open
S5
Airflow Recdngs
Inm3^min
0.0
0.3
0.6
0,6
1.4
1,1
1.7"
1.1
1.7
1.4
1.7 <
2.3'
1.4
1.7
2.0
1.1
m3/tnin_
m3Anin
m3/hin
m3^r1n
Air_Flow Across Intake Chute, m3/min
3.0
Ej 2.5-3.0
2.0-2.5
~ 1.5-2.0
1.0-1.5
El 0.5-1.0
0.0-0.5
1 2.0
Sample Position, Width
Sample
Position,
Depth
Figure 36. Initial air flow test results.
97
-------
Date: 17-Jm94
Fen Setting: Med.
Water Flew Off
Air T emperature: 22 C
Air FlowTestNo. 23
T ech: Glenn Mattson
Exhaust Fen sotting Off
Damper Setting 0.125% Open
Air Pressure: 0.084 MPa
Test Positions
Airflow Recdngs
SI
S2
S3
1 :
2'
3~
A
1.7
2.3
2.0
2.5
2.3
2.8
2.8
2.5
S4
S5
in m3/fmin
2.5
2.8
2.3
2.8
2.5;
2.8
2.5
2.5!
2.5
2.5
2.5:
2.8i_
"2*5;
2.8:
2.8
2.8;
2.8'
Air Flow Across Intake Chute, m3/min
c
'E
CO
E
S
o
u.
6
2.5
2.5
2.3:
2.8
3.1
7
2.3
2.3
2.3'
2.8
2,8
8
2.3
2.0
2.3
2.5
2.8
9
1.7
1.7
2.0
2.5
2.3
Average
2.5
m3/frrn
S td Dev
0.3
m3/trrn
Mot
3.1
ntf/nn
Min
1.7
rn3/tnin
3.0-3.5
~ 2.5-3.0
2.0-2.5
~ 1.5-2.0
1.0-1.5
EI 0.5-1.0
0.0-0.5
Sample Position, Width
Sample
Position,
Depth
Figure 37. Air flow test results with foam filter.
98
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Anemometer cbta
|
Date:
6-Jul-94
Tech: Glenn Mattscn
TestCondticris;
Series 1
Series 2
Series 3
Series 4
Hood Exhaust Fen S efting;
Off
Off
Off
Off
Water S ucply Pump S etting
Off
Off
Off
at
Dcrrper Pcsition S etting
0.125
0.125
0.125
0.125
System Exhaust Fen Setting
Low
0.25
Med urn
0.75
Series 1
Test No.:
20
21
24
25
26
Date:
17-Jun-94
17-Jun-94
17-Jury 94
17-Jur>94
20-Jun-94
Avercpe:
0.4
0.3
0.4
0.2
0.2
m3/hnin
Std. Dev.:
0.2
0.2
0.2
0.3
0.3
m3/tnin
Max.:
0.8
0.8
0.8
0.8
0.8
m3^irin
Min.:
0.0
0.0
0.3
0.0
0.0
m3Ar«n
Seties 2
T est No.:
18
19
27
28
29
Dcfe:
17-Jun-94
17-Jun-94
20-Jut>94
20-Jun-94
20-Jun-94
Avercge:
0.9
0.9
0.7
0.7
0.7
m3/tnin
Std. Dev.:
0.2
0.2
0.2
0.2
0.2
m3/ftin
Max.:
1.1
1.1
1.1
1.1
1.1
m3/tnin
Vl:n.:
0.6
0.6
0.3
0.3
0.3
m3/hin
Series 3
I est No.:
22
23
30
31
32
Date
17-Jur>94
17-Jun-94
20-Jun-94
20-Jun-94
20-Jun-94
.Aver aps:
2,5
2.5
2.2
1.9
1.9
m3/tTin
iStd. Dev.:
0.4
0.3
0.3
0.4
0.3
rrflArin
Mck.:
3.1
3.1
2.8
2.5
2.5
rr£Mrin
M!n.:
1.1
1.7
1.7
1.1
1.1
mS^Tin
1
Serles4
Test No.:
33
34
35
38
39
Date:
0
1
20-Jur>94
20-Jun-94
7-JJ-94
7-Ju!-94
Average:
2.6
2.6
26
2.6
2.6
m3Amin
Std Dev.:
0.4
0.3
0.4
0.3
0.4
m3yhin
Max.:
3.4
3.1
3.4
3.1
3.1
m3Anin
Min.:
1.7
1.7
1.4
1.7
iA
m3/tmin
Selection of Continuous Monitoring Pcsition:
Position: B-6. (6,S2)
T estCondticns:
Series 1
Series 2
Series 3
Series 4
Readng- Test 1
0.3
0.8
2.5
2.5
m3/tnin
Recdng-Test2
0.0
0.8
2.5
2.5
m3/ftin
Readng- Test 3
0.0
0.8
2.5
2.5
m3Arin
Readng- T est 4
0.6
1.1
2.0
2.5
m3/ftin
Readng- T est 5
0.3
0.8
1.7
2.5
m3Anin
Avercge
0.2
0.9
2.3
2.5
m3An'n
S td. Dev.
0.2
0.1
0.4
0.0
rri3Arin
Max.
0.6
1.1
2.5
2.5
m3/trin
Mn.
0.0
0.8
1.7
2.5
m3/b"in !
Figure 38. Analysis of air flow and placement of the anemometer.
99
-------
Percent RSD versus Air Flow Velocity
U3 30
0.00
0.10
0.20
0.30
0.40
0.50
Average Air Flow Velocity, m/s
Figure 39. Relative standard deviation as a function of air velocity.
To ensure the accuracy of this product line of instruments. Vaisala had its products tested at the National
Institute of Standards and Technology. The product line demonstrated an accuracy of ±1 percent Rl-I (including
calibration uncertainty, nonrcpcatability, hystcrsis and temperature dependence) at three temperatures, 0, 20, and
40 UC. Since relative humidity measurements were secondary control measurements, no independent calibration
checks were conducted to support or verify the factory calibration.
Water Flow
Again, water flow and pressure measurements were used in this test system to monitor whether the fire suppression
tests were run under repeatable test conditions. The water system is a closed loop in the spray chamber: only the
WM entering the duct work going to the. fire test zones is not recycled. The system is designed for high-pressure
fluids with the appropriate safeguards in place. The pump is a duplex positive displacement plunger type rated at
0 to 3 by 104 m7s at 24.8 MPa discharge pressure, the motor is 3.7 kW, 230v, 60 H/., and 13.2 amp controlled by a
high-speed digital signal processor control AC inverter. The pump's output is monitored by a 0 to 20.6 MPa
glycerin-fillcd pressure gauge with a full scale accuracy of ± 1.6 percent and a 4 to 18 L/min high-pressure
flowmeter with an accuracy of ± 4 percent full scale.
100
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Fraunhofer Instrument
Due to the detail given for the design and development of the Fraunhofer instrument, discussion of this
instrument and its operation is included in Appendix A.
Water Flux and Extinguishment Testing
Standard deviations were calculated using the nonbiased or n-1 method. Graphical representations of the
water flux reproducibility are included in Appendix C.
101
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SECTION 8
TASK 3: ENGINEERING AND COST EVALUATION OF A WATER MIST SYSTEM
INTRODUCTION
The Task 3 requirement of this project was a direct system life-cycle cost comparison between three present
halon applications and an equivalent WMS developed in Task 2. Due to uncertainties in the requirements coming
out of the NFPA Standard 750 on WM fire protection system installation, operation, and testing procedures, the
marketer of the nozzles tested was unwilling to give final costs. To complete the Task 3 phase of the. project, three
generalized WMSs where enough information was available to complete an econometric analysis were used.
Therefore, this task evaluates three applications of WMSs as replacements for Halon 1301 total-flood
systems. WM is currently widely used as a replacement technology for traditional automatic sprinklers, particularly
in the marine cruise ship industry, for accommodation spaces. However, WM technology as a Halon 1301 total-
flood replacement is only beginning to be used and only in relatively narrow application areas. This section will deal
with the engineering design and cost issues in three application areas where WM is a clearly demonstrated Halon
1301 replacement:
1. Marine engine room and machinery spaces
2. Combustion turbine enclosures
3. Emergency generator, engine lest cells, and similar facilities
All of these areas contain flammable materials and combustible liquid fuel hazards, but each has unique
operational and design constraints.
No computer room, telecommunications, or similar electronics facilities are discussed because to date no
WMS has been developed that can duplicate the performance of total-flood gaseous systems in these applications.
Although these applications represent approximately 70 percent of the total-flood gaseous extinguishment
applications, it is premature to develop engineering data. Several important limitations arc likely to severely limit
the use of the WMS in electronics applications except as a replacement for traditional automatic sprinklers. These
limitations include the following:
1. Inability to extinguish shielded or partially enclosed cellulosic or polymeric fuels typical of electronics
facilities.
102
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2. Unresolved issues with respect to collateral equipment damage caused by water deposited on
equipment.
3. The need to apply mist over a relatively large area (approximately 100 m7) or throughout the protected
enclosure.
Although WMSs have advantages over traditional automatic sprinkler systems in these applications, they
have, not yet been demonstrated as a replacement for clean agent total-flood systems at this time and hence are not
included in this discussion.
No WMS technology to date has been demonstrated or used for explosion inertion. While some promising
results have been obtained in certain geometries, no general system design or installation requirements have evolved.
WMSs for use in explosion inertion appear possible, but the technology has been inadequately demonstrated for this
application to date.
Cost Estimates
The cost estimates that are given for the three applications selected are based on a number of assumptions.
These are outlined below:
1. Where pumps are required for a WMS, it is assumed that sufficient electric power is available.
2. All systems assume Underwriters Laboratories (UL) or Factory Mutual (FM) approval on all hardware
components. Note that such approval is not currently available for many WMS components but
approval testing is underway.
3. For halon system cost comparisons, a current price of Halon 1301 of $50/kg is assumed. This price is
comparable with the current list prices of halon replacements such as HFC-227ea.
4. Cost estimates are based on approximate equipment list prices and installation costs. Precise cost
estimates depend on the particular installation details. The cost estimates provided are reasonable for
cost comparison purposes.
5. Maintenance costs (if both WM and Halon 1301 systems are approximately equivalent, depending on
the exact WMS selected.
6. The life cycle cost comparisons are completely driven by the probability of an accidental discharge.
The costs associated with an accidental discharge of WM are minimal. Costs are very high for an
accidental discharge of a Halon 1301 system, on (he order of $ 10/rri'1 of enclosure volume.
In all cases, these cost estimates should be considered very approximate but adequate for comparison
between systems.
103
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SYSTEM TYPES AND OPERATING PRINCIPLES
At least four different WMS types have been demonstrated to be effective in the three application areas
discussed. While the performance between systems may vary, all have the potential to be Halon 1301 replacements
in these applications. Fire extinguishing ability and system limitations (such as maximum enclosure size) are
significantly different for these systems, but all have some potential for application in these areas.
The various system types all represent proprietary technology either in nozzle design or overall system
design and will vary widely in installation cost, space, and weight requirements as well as engineering requirements.
Hence, no general specifications and few generic requirements can be applied to WMSs. Each has particular
advantages and disadvantages that may make it preferred in a particular installation. To give a more accurate
representation of WMS design options and costs for each of the three application areas selected, each of the four
generic system types will be addressed. The four system options are given below.
High-Pressure. Single-Fluid System
This type of system consists of high-pressure water storage or pumps (> 8 MPa) connected through high-
pressure stainless steel tubing to a series of uniformly spaced nozzles throughout the space. The typical coverage is
3 to 10 nr per nozzle, with flow rates on the order of 5 to 10 L/min depending on the application. The systems can
be detector-activated or manually-actuated deluge systems (all open nozzles) or individual thermally activated
nozzles, like a typical sprinkler system. For halon total-flood system applications, only detector-actuated deluge
systems have been demonstrated as equivalent.
System components consist of the following:
1. W'ater source tank or pressure cylinders
2. Diesel engine or electric powered pumps or pressurized storage cylinders
3. Filters
4. Stainless tubing with compression fittings
5. Control and test valves
6. Nozzles
7. Activation element/sensors
Operationally, these systems are almost identical to typical deluge sprinkler systems. The primary
differences are higher pressure and lower flow rates. The primary disadvantage of these systems is the electric
power requirements for the high-pressure, moderate water flow rate demands. A rule of thumb of 0.5 kW for
4 L/min at 8 MPa gives an indication of the power demand for these systems. The pump power requirement can be
overcome by the use of high-pressure water storage cylinders (-15 MPa to 30 MPa). These systems, however, do
104
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not provide sufficient flow durations (minimum of 20 min) unless an excessively large number of cylinders is used.
Typical schematics of a pump-driven and stored pressure deluge system are given in Figure 40 and Figure 41.
To Actuation Switch (manual)
tons
r Ti
f Solenoid Operated Valve
(to pump #1 start)
Pressure Switch
(60-Sccond Water Supply)
(20 MPa)
Circuit
Circuit
i' — -i^ rk^-^P^
'! (mJH J (to pump #2 start)
Nosste
Pump Set 1
Circuit 1
Circuit 2
—epitv
Pump Set 2 T
Filter
I
Fresh Water
Emergency Sea Vater
System Piping
Figure 40. High-pressure water mist system for a machinery space.
105
-------
To TimerDetection System
Solenoid
Valve
Pressure
Switch
(60-second Water Supply)
(20 MPa)
Filter
To Nozzles
Figure 41. Stored high-pressure water mist system for an emergency diesel generator space.
High-pressure WMSs have the advantages of relatively low water flow rates, excellent fire extinguishing
ability on flammable and combustible liquid spray and pool fires, very good performance on reasonably well
shielded fires, and relatively simple design.
Manufacturers of high-pressure systems include Marioff (Finland), Semco Marine (USA), and Unitor
(Germany). Systems based on industrial spray nozzle technology have been tested by the Naval Research
Laboratory using a modified Spraying Systems Company (USA) nozzle.
Hybrid Pump/Stored Pressure System
At least one mist system manufacturer has combined the advantages of stored pressure and pump-driven
systems while preserving the advantages of high-pressure, single-fluid systems. This hybrid system consists of both
high-pressure storage cylinders and pumps. The flow is pulsed on and off such that pumps recharge the cylinders
after each high-pressure discharge through the nozzles. Since high-pressure pumps are used, a pressure of 8 MPa or
higher is easily restored to the storage cylinders after each high-pressure discharge. This has the net effect of
106
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significantly lowering the. power/pumping requirement while preserving the advantage of an indefinite duration of
protection. The only current manufacturer of a hybrid system is Marioff Hi-fog (Finland).
Low-Pressure, Sinule-Fluid System
This system operates at approximately 1 to 1.2 MPa and is a derivative of traditional automatic sprinkler
technology. The nozzles are optimized to produce a WM with a fraction of -100 fim diameter drops while using
500- to 1000-Jim diameter drops to carry the ~ 100 Jim-diameter drops throughout the space. These systems are
functionally equivalent to traditional automatic sprinkler and deluge water spray systems except that the minimum
nozzle pressures are higher, the total water flow rates are lower, and the percentage of small (-100 pm) water
droplets is higher. In general, compared with the high-pressure WMS, the water flow requirements are two to three
times higher for protecting against a similar hazard. While the use of lower pressure-rating hardware has cost
advantages, the higher water flow rates and generally smaller nozzle spacings may tend to equalize the installation
costs.
Current manufacturers of low-pressure, single-fluid WMSs include Grinnell (USA), GW Sprinkler
(Denmark), and Kidde International (UK).
Low-Pressure. Dual-Fluid Svstems
This system utilizes water and nitrogen or air. The nitrogen or air is used to assist atomization at the nozzle
and to provide, some momentum to the resultant water/air/N2 jet. The air or nitrogen source is also used to pressurize
(1 MPa) water storage cylinders and to provide the power source for the water flow. These systems are effective in
producing relatively small (100 fim) droplets and hence are effective on a range of flammable and combustible liquid
hazards.
Since these systems utilize fixed-storage quantities of water and atomizing/pressurizing media, large storage
volumes of both are required for locations requiring extended duration of protection. This problem has been
mitigated by the use of pulsed flow, where the flow is cycled on then off at a 2:1 or 3:1 ratio and/or controlled by a
heat detection system. A schematic of a stored-pressure, dual-fluid system is shown in Figure 42. Currently, the
only commercial manufacturer with a listed dual-fluid system is Securiplex (Canada).
Representative system costs will be given for both halon and WMSs for each of the three application areas
selected.
107
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M*r«yal Rde
System Released
A arm &
Control
24V DC
24V DC
Fine water Spray Nocck>
Release & Control
Manual
Release
HTl
Spring Rcturh
PNELL Actuator
Vcfit.
vH r^
1 MPa
_ _j
Pre tare
Regulator
P.S.V.
P.R.V
P.S.V
Cylinder Valve
N2
15 MP?.
Watei
Stores
Tank
N o
Bank
Drami" rilling
Legend
N.C. Normally Closed S.O.V.
P1 Pr«««rc Gayflc P.S.t.
P.R.V. Ptfcftiial Pressure Relief Valve P SM
P.S.V. Pressure Safety Valve
6
Solenoid Operated Valve
Pressure Switch (Low)
Pressure Switch (High)
Valve Handle
Figure 42. Dual-fluid system schematic.
108
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FIRE SUPPRESSION CAPABILITY
Both high-pressure single-fluid and low-pressure dual-fluid WMSs have been demonstrated to be effective
in extinguishing flammable and combustible liquid fires. Low-pressure (1 MPa), single-fluid WMSs have been
demonstrated to control flammable liquid fires and to extinguish moderate size fires effectively (>2 MW) in
relatively small enclosures (500 m3); however, at the present time these systems have not been able to extinguish all
fires, particularly fires of low-flash point liquids. In applications where the enclosure is relatively small and the
combustible liquid has a high flash point, WMSs can be considered alternatives to haJon systems. Beyond this
application, low-pressure systems are not considered further.
In the other major application area of halons, computer rooms and electronics equipment, WMSs have not
been demonstrated to provide equivalent levels of fire extinguishment for cabinet-level fires, and the questions
concerning collateral damage of water on energized electrical equipment have not been resolved. In general, WM
will suppress but not extinguish obstructed deep-seated Class A material fires typical of those expected in computer
rooms. Hence, these systems are not halon replacements on the basis of this performance. They do offer advantages
over sprinkler systems in these applications. Therefore, this report deals with flammable and combustible hazards
where equivalence to halon performance has been demonstrated.
MARINE ENGINE ROOM AND MACHINERY SPACE APPLICATIONS
The governing regulation for the design and installation of a WMS on ships is the IMO MSC Circular 668
(51). The general specifications taken from the IMO Standard for such systems are as follows:
1. The system must be capable of manual release.
2. The system should be capable of fire extinction and tested to the satisfaction of the IMO
administration in accordance with Appendix B of IMO MSC Circular 668 (51).
3. The system shall be available for immediate use and capable of continuously supplying water for at
least 30 min in order to prevent reignition or fire spread within that period of time. Systems that
operate at a reduced discharge rate after the initial extinguishing (activation) period should have a
second full fire extinguishing capability available within a 5-min period of initial activation. A
pressure tank should be provided to meet the functional requirements stipulated in Safety of Life at
Sea (SOLAS) Regulation II-2/12.4.1 (52). (This requires 60 s of maximum water flow demand
without the use of pumps or external power.)
4. The system and its components should be suitably designed to withstand ambient temperature
changes, vibration, humidity, shock, impact, clogging, and corrosion normally encountered in
machinery spaces_or cargo pump rooms in ships. Components within the protected spaces should be
designed to withstand the elevated temperatures that could occur during a fire.
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5. The system and its components should be designed and installed in aecordance with international
standards acceptable to the IMO organization and manufactured and tested to the satisfaction of the
IMO administration in accordance with appropriate elements of Appendices A and B of IMO MSC
Circular 668 (51).
6. The nozzle location, type of nozzle, and nozzle characteristics should be within the limits tested to
provide fire extinction as referred to in item 3 above.
7. The electrical components of the pressure source for the system should be resistant to water
penetration. The system should be supplied by both main and emergency sources of power and should
be provided with an automatic change-over switch. The emergency power supply should be provided
from outside the protected machinery space.
8. The system should be provided with a redundant means of pumping or otherwise supplying the water-
based extinguishing medium. The system should be fitted with a permanent sea inlet and be capable
of continuous operation using seawater.
9. The piping system should be sized in accordance with an hydraulic calculation technique.
10. Systems capable of supplying water at the full discharge rate for 30 min may be grouped into separate
sections within a protected space. The sectioning of the system within such spaces should be
approved by the IMO administration in each case.
11. In all cases, the capacity and design of the system should be based on the complete protection of the
space demanding the greatest volume of water.
12. The system operation controls should be available at easily accessible positions outside the spaces to
be protected and should not be liable to be cut off by a fire in the protected spaces.
13. Pressure source components (i.e., pumps and/or storage cylinders) of the system should be located
outside the protected spaces.
14. A means for testing the operation of the system for assuring the required pressure and flow should be
provided.
15. Activation of any water distribution valve should give a visual and audible alarm in the protected
space and at a continuously manned central control station. An alarm in the central control station
should indicate the specific valve activated.
Cost Comparison (Marine Engine Room)
For purposes of cost evaluation, a compartment volume of 1500 m1 is selected with a space height of 5 m.
The WMS used is a high-pressure single-fluid system. The system is designed and installed in accordance with IMO
MSC Circular 668 (51) and represents a system tested under these requirements by the Naval Research Laboratory
(NRL). The system utilizes modified Spraying System nozzles operating at 6.90 MPa with a 3-m2 nozzle coverage
area. It is assumed that the ship's main and emergency generators have sufficient reserve capacity to meet the
110
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increased cleeiriea] power demand of the pumps. The system is manually actuated. The schematic in Figure 40
applies. Table 24 summarizes the cost estimate for the mist system. A Halon 1301 system is estimated to cost
$150/nr of protected space, following typical marine cost multipliers and current halon prices. These costs are
approximately the same as installed halon replacement prices.
TABLE 24. COST COMPARISON FOR A 1500-M3 MARINE ENGINE ROOM
System Installed cost
($) ($/m3)
Water mist system with open bilge 180,000 120
Water mist system with enclosed bilge 220,000 147
Halon 1301 system 225,000 150
Carbon dioxide 100,000 67
The cost calculations are based on the following assumptions for WM and Ilalon 1301/CO2 systems:
a. Water Mist System --
• Existing ship's generator and emergency generator have sufficient reserve capacity for
approximately 123 kW additional power requirement.
• The open bilge is fitted with open grating, and the enclosed bilge covers approximately
80 percent or more of the bilge area with a solid deck plate.
• No additional potable or fresh water tank is required.
b. Halon 1301 System and CO-, System -
• The single shot system is in accordance with IMO/lJnited States Coast Guard (USCG) guidelines.
The principal components and their specifications for the WMS are as follows:
a. Stainless steel positive displacement pumps, approximately 570 I./min at 8 MPa.
b. Stainless steel tubing and compression fittings, pressure rated to 20 MPa.
c.. Automatic electric-driven pump controller.
d. Automatic changeover switch for normal/emergency power.
e. Stainless steel, open head nozzles.
f. Miscellaneous control and shut-off valves.
Ill
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g. High-pressure storage cylinders, 12001, capacity, 50 percent by volume water charge, pressurized to
10 MPa for 1-min discharge as required by IMO MSG Circular 668 (51).
h. All pressure components including pumps, valves, cylinders, pipe supports, arc to be designed in
accordance with the American Society of Mechanical Engineers (ASM12) Power Piping Code (53).
COMBUSTION TURBINE ENCLOSURES
Performance Requirements and General Specifications
The major performance requirements for protection of combustion turbine installations are as follows:
1. Protection system must extinguish obstructed multidimensional pressurized spray and liquid pool
fires. Fuels of concern are low- and high-flashpoint liquids and possibly flammable gases.
2. Protection system must maintain protection for duration of turbine wind-down since lubricating oil
systems will continue to operate throughout the coast-down period.
3. The mist application must be of sufficiently low water flux, have the proper droplet size, and have the
appropriate momentum to ensure adequate low cooling rates on the turbine casing.
4. In some applications, explosion prevention or inerting may be required. No mist systems have been
demonstrated to date that will ensure explosion inertion over a range of enclosure and obstruction
geometries.
5. Based on an evaluation of the performance of WMSs to date and given the relatively small volumes of
these enclosures, a deluge or total-flood mist system will be required.
6. The system must be capable of automatic detection upon receipt of the appropriate detection signal,
typically from heat detectors.
7. The system and all associated components must be approvable by FM for gas turbine applications.
Comparison of costs and general specifications for a 320-m3 combustion turbine enclosure protection
system is based primarily on systems tested in accordance with FM approval guidelines, which are currently in the
draft stage for WMSs. Halon systems are assumed to be designed and installed in accordance with NFPA 12A,
Standard for Design and Installation of Halogenated F.xtinguishing Systems (12).
The following are the general specifications for WMSs:
1. Automatic operation based on thermal detection.
2. Constant or uniform cyclical flow or detection-activated flow control based on fire test requirements
for a duration of not less than 40 min.
3. For pump systems, no redundant pump is required.
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4. All components including storage cylinders, pumps, valves, controllers, tubing, fittings, and nozzles
are UL/KM listed or approved.
5. Nozzle spacing, location, and flow rate are as determined by fire testing requirements for both fire
suppression anil limitation of cooling of turbine housing.
The fire extinguishment guidance for liquid fuel-fired combustion turbines is essentially identical to those
for marine engine rooms. Systems successfully tested in accordance with IMO MSC Circular 668 (51) will give an
excellent indication of performance under fire test conditions proposed by FM for combustion turbine enclosures.
The primary threat evaluated is a high-pressure low flash point fuel (heptane) spray.
Based on the results of the IMO and FM tests, two WM technologies appear to offer the necessary fire
extinguishment performance. These are high-pressure single-fluid and low-pressure twin-fluid systems. Specific
systems/hardware that have been successfully demonstrated to date are (1) Modified Spraying System's industrial
spray nozzles, and (2) Securiplex (BP nozzle derivative) proprietary twin-fluid system. An air-assisted dual-fluid
nozzle system following a Securiplex design is proposed with the parameters given in Table 25. A schematic of this
system is shown in Figure 41.
TABLE 25. WATER AND NITROGEN REQUIREMENTS FOR A HIGH-PRESSURE
SINGLE-FLUID SYSTEM
Protected volume 75 m3 320 m3
1 -MPa water-storage tank 189 L 756 L
15 MPa nitrogen cylinder: detection system controlled cycling 1 (56.6-L) cylinder 4 cylinders
Table 26 summarizes the low-pressure water storage requirement and high-pressure cylinder storage for a
heat-detection-actuated system that cycles off and on as a function of the temperature in the protected compartment.
The low-pressure system could be used with a pumped low-pressure water supply and high-pressure stored nitrogen.
These values can be related to a .Securiplex system passing the fire tests of the FM approval standard using
approximately 378 L of water storage and one 56.6 L nitrogen cylinder with detection-controlled cycling. It appears
that the least expensive system would be a stored water/air and detection-controlled on/off system cycling since this
has the potential of significantly reducing the water and gas storage requirements and their associated cost and
storage space penalties.
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TABLE 26. WATER AND NITROGEN REQUIREMENTS FOR A LOW-PRESSURE
TWIN-FLUID SYSTEM
Cycle on (%)
100
50
33
20
Average flow rate (Lpm)
454
227
151
95
Total flow (L)
18144
9072
6048
3629
Total N2 cylinders (20.7 MPa, 56.6 L cylinders)
20
10
7
4
Cost Estimates
A detailed comparison of system equipment costs is not possible at this time given the uncertainty in the
exact nature of the system components. Approximate order of magnitude costs are given below for rough
comparison purposes.
Table 27 assumes equipment requirements for the Air Atomized Self-contained System (320 mJ protected
volume) similar to the BP/Securiplex System, as shown in Figure 41, and a nozzle spacing where each no/./le covers
an area of 2.5 mJ. The installed cost of the former system complete with detection system based on the
manufacturer's estimate of $ 150/m1 of enclosure volume is $48,000. The halon system cost for an equivalent
enclosure is approximately $125/nrr or $40,000.
TABLE 27. EQUIPMENT SUMMARY FOR AN AIR ATOMIZED SELF-CONTAINED SYSTEM
Quantity
Equipment description
Unit cost ($)
Cost ($)
14
Nozzles
200
2,800
1
Water supply tank (756 L)
2,000
2,000
1
High pressure cylinder, regulator
1,000
1,000
1 set
Carbon steel piping, fittings
1,000
1,000
1
Mixing control valves, solenoid valves
2,000
2,000
Estimated equipment cost without detection system, not installed, no mark-up 8,800
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EMERGENCY DIESEL GENERATOR ROOM
This hazard is almost identical to a marine engine room except that it is land-based and not subject to
LMO/USCG requirements; however, il would require UL/FM listed/approved hardware and components. Similar
related facilities include automotive and aircraft engine test cells and small flammable liquid storage rooms.
The design and cost of a WMS in this application is strongly dependent on the flow duration requirement.
In marine applications, the 1MO requirement is for a minimum of 30 min supply plus the ability to supply the system
from a sea water connection for an indefinite duration. Such a requirement effectively demands a pump-driven
system as opposed to a stored-pressure/water supply cylinder-based system. In the case of combustion turbines, the
maximum protection duration requirement of 40 min is based on the maximum coast-down time of a turbine during
which time the lubricating oil supply must function and the attendant fire risk still exists.
Gaseous total-flood systems had a typical equivalent duration of protection time between 15 and 30 min.
In this case, the retention time had no impact on the agent storage requirement. For mist systems, however, the
protection is eliminated when the water flow ceases. Hence, for long duration flow requirements, pumps and
attendant motors, contr ollers, power supplies, and, in many cases, redundancy of each is required. For short
durations on the order of 10 to 15 min, it is possible to utilize stored-pressure cylinders. For this example, the
duration of protection is assumed analogous to that achieved for halon systems or approximately 15 min.
The mist system will consist of high-pressure ('20 MPa) storage cylinders pressurized with nitrogen to a
50 percent fill capacity. A schematic of this system is shown in Figure 40. The flow will be pulsed 30 sec on, 30 sec
off; such pulsing flow has been found effective for fire suppression of combustible/flammable liquid risks. A 500-rrf
enclosure is assumed. The general WMS specifications for this application are as follows:
1. Storage cylinders at 20 MPa
2. Solenoid/timer controlled flow, 30 sec on, 30 sec off cycle
3. Stainless steel tubing and nozzles, 8 MPa operating pressure
4. Detector actuated with manual release option
5. Interlock to ventilation fans
6. Hardware approved by UL/FM
7. Fire testing per IMO MSG Circular 688
8. Sufficient water storage for a 15-min flow duration.
The halon system is in accordance with NFPA 12A. Table 28 lists the installed costs for these systems for
an emergency diesel generator room. A low-pressure (1 MPa) twin-fluid system in this application would have an
installed cost of approximately $45,000 (S141/m3 assuming the same 320 m3 of protected space).
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TABLE 28. INSTALLED COST COMPARISON FOR EMERGENCY DIESEL GENERATOR ROOM
System
Installed cost
($)
($/m3)*
Water Mist
50,000
156
Halon 1301
'i .—. . ,™
75,000
234
* Assuming 320 m of protected space.
SUMMARY
1. WMSs can be effectively used to protect spaces with flammable and combustible liquid hazards that
were formerly protected with Halon 1301 total-flood systems.
2. The installed cost of mist systems depends on the requirements of the installation. A system cost of
$90 to $150/m3 across a range of technologies is a high end estimate. If low-pressure, water-only mist
systems were to demonstrate adequate performance, this installed cost could be reduced to below
$30/m3 of protected space.
3. Any WMS should be tested, certified by the authority having jurisdiction, and approved for the
application intended. This includes both fire testing and component or hardware reliability testing.
No generalized fire test approval guidelines exist today, with the exception of the LMO MSC Circular
668 on marine machinery spaces. Although no generalized component reliability testing procedures
exist, they may be readily adapted from traditional fire protection equipment requirements.
4. The only application of Halon 1301 total-flood systems for which WMSs have demonstrated
equivalent performance is in flammable and combustible liquid applications. WM in computer rooms
and electronics facilities could be easily adapted to replace sprinkler systems, but near total-flooding
gas performance of a WMS relative to fire extinction is not achievable at this time. No systematic
evaluation of the damage to energized electronic equipment by WM application has been conducted;
therefore, it is an unresolved issue.
5. Given the high cost of available recycled Halon 1301 (approximately $50/kg), the cost of WMSs is
competitive with Halon 1301 systems. It is expected that the cost of the WMS, currently at $90 to
$ 150/m3 of protected space, will decrease over time as additional competitors enter the market and
R&D costs are recovered. The cost of halon replacement systems is approximately the same as Halon
1301 systems under the current 1301 price structure. Consequently, WMSs appear to be cost
competitive with Halon 1301 and other total-flood alternatives in many applications.
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REFERENCES
1. Molina, M.J. and Rowland, F.S., "Stratospheric Sink for Chlorofluoromethane: Chlorine - Atom Catalyzed
Destruction of Ozone," Nature, Vol. 249, pp. 810-812, 1974.
2. Brown, J.A., Jacobson, E., Dvorak, L.E., Gibson, J., Gupta, A., Methis, K., Mossel, J.W., Simpson, T„
Speitel, L.C., Tapscott, R.E., and Tetla, R.A., Chemical Options to Halon for Aircraft Use, DOT/FAA/CT-
95/9, Final Report, Task Group 6, International Halon Replacement Working Group, U.S. Department of
Transportation, Federal Aviation Administration, February 1995.
3. Tapscott, R.E., Dierdorf, D.S., and Moore, T.A., Preliminary Testing of Encapsulated Micron Aerosol
Agents, Letter Report, Wright Laboratories (WL/FIVCF), Tyndall Air Force Base, Florida, March 1993.
NMERI SS 2.03(6)
4. Harrison, G.C.. "Solid Particle Fire Extinguishants for Aircraft Applications," Proceedings of the Halon
Alternatives Technical Working Conference 1993, pp. 437-443, Albuquerque, New Mexico, May 11-13.
1993.
5. Andreev, V.A., Kopylov, N.P., Makeev, V.I., Merkulov, V.A., and Nikolaev, V.N., "Replacement of Halon
in Fire Extinguishing Systems," Proceedings of the Halon Alternatives Technical Working Conference
1993, pp. 409-412, Albuquerque, New Mexico, May 11-13, 1993.
6. Ewing, C.T., Hughes, J.T., and Carhart. H.W., "Dry Chemical Development - A Model for the Extinction of
Hydrocarbon Flames," NRL Memorandum Report 5267, Naval Research Laboratory, Washington, DC,
February 8, 1984.
7. Ewing, C.T., Faith, F. R., Hughes, J.T., and Carhart, H.W., "Flame Extinguishment Properties of Dry
Chemicals: Extinction Concentrations for Small Diffusion Pan Fires," Fire Technology, Vol. 25, pp. 134,
1989.
8. Ewing, C.T., Faith, F. R., Romans, J.B., Hughes, J.T., and Carhart, H.W., " Flame Extinguishment
Properties of Dry Chemicals: Extinction Weights for Small Diffusion Pan Fires and Additional Evidence for
Flame Extinguishment by Thermal Mechanisms," Journal of Fire Protection Engineering, Vol. 4,
pp. 35, 1992.
9. Spring, DJ. and Ball, D.N., "Alkali Metal Salt Aerosols as Fire Extinguishants." Proceedings of the Halon
Alternatives Technical Working Conference 1993, pp. 413-420, Albuquerque, New Mexico, May 11-13,
1993.
10. Kibert, C.J., Ranker Sr., M.E., and Dierdorf. D.S., "Encapsulated Micron Aerosol Agents (EMAA),"
Proceedings of the Halon Alternatives Technical Working Conference 1993, pp. 421-436, Albuquerque,
New Mexico, May 11-13, 1993.
11. Jacobson, E., "Part iculate Aerosols—Update on Performance and Engineering," Proceedings of the Halon
Options Technical Working Conference 1995, pp. 485-497, Albuquerque, New Mexico, May 9-11, 1995.
12. Halon 1301 Fire Extinguishing Systems, NFPA Standard 12A, 1992 Edition, National Fire Protection
Association, Quincy, Massachusetts, 1992.
13. Papavergos, P.G., "Fine Water Sprays for Fire Protection," Proceedings of the Halon Alternatives
Technical Conference 1991, pp. 206-217, Albuquerque, New Mexico, May 1991.
117
-------
14. Butz, J.R. and Carey, R., "Application of Fine Wafer Mists to Fire Suppression," Proceedings of the Union
Alternatives Technical Working Conference 1992, pp. 358-363, Albuquerque. New Mexico, May 4-13,
1992.
15. Wighus, R., "Extinguishment of Enclosed Gas Fires With Water Sprays," Fire. Safety Science - Proceedings
of the Third International Symposium, Lilsevier (ISBN 1-85166-719-9), Edinburgh, Scotland, 1991.
16. Cousin, C.S., "Recent Work on Fire Control Using Fine Water Sprays at the Fire Research Station."
Proceedings of the First International Conference on Fire Suppression Research, pp. 229-244, Stockholm
and Boras, Sweden, May 5-8, 1992.
17. Hill, R.G., Sarkos, C.P., and Marker, T.R., "Development and Evaluation of an On-Board Aircraft Water
Spray System for Postcrash Fire Protection," SAE Technical Paper 912224, Aerospace Technology
Conference and Exposition, Long Beach, California, September 23-26, 1991.
18. Hill, R.G., Marker, T.R.. and Sarkos. C.P., "Evaluation of an On-Board Water Spray Fire Suppression
System in Aircraft," Presented at the Water Mist Fire Suppression Workshop, National Institute of
Standards and Technology, Gaithersburg, Maryland, March 1, 1993.
19. Whitfield, R.T., Whitfield, Q.A., and Steel, J., Aircraft Cabin Fire Suppression by Means of an Interior
Water Spray System, CAA Paper 88014, Civil Aviation Authority, July 1988.
20. Mawhinney, JR., "Fine Water Spray Fire Suppression Project," Proceedings of the First International
Conference on Fire Suppression Research, pp. 109-127. Stockholm and Boras, Sweden, May 5-8, 1992.
21. Turner, A.R.F., "Water Mist in Marine Applications," Presented at the Water Mist Fire Suppression
Workshop, National Institute of Standards and Technology, Gaithersburg, Maryland, March 1, 1993.
22. Arvindson, M. and Ryderman. A., Tests in Simulated Ship's Engine Rooms with Hi-fog Fire Protection
System, 91 R30189, Swedish National Testing and Research Institute, Boras. Sweden, July 28, 1992,
23. Tuomissari. M., Fire Suppression Tests in Simulated Ship's Engine Room with a Hi-fog Fire Protection
System, PAL 2210/92, VTl'Fire Technology Laboratory, Helsinki, Finland, November 16, 1992.
24. Soja, E., DGME Waterfog Trials, YARD Report No. 4175-NM0609, British Ministry of Defense - Navy,
Bath, England, 1990.
25. Gameiro, V., "Fine Water Spray Fire Suppression Alternative to Halon 1301 in Machinery Spaces." The
1993 International CFC and Halon Alternatives Conference Proceedings, pp. 830-839, Washington, DC,
October 20-22, 1993.
26. Arvindson, M. and Ryderman, A., Cabin and Public Space Fire Tests with Marioffs Hi-fog Fire Protection
System, 91 R30141, Swedish National Testing and Research Institute, Boras, Sweden, February 19, 1992.
27. Tuomissari, M.. Extinguishing Tests of Simulated Computer Room Fires by a Hi-fog Sprinkler System, PAL
2196/92, VTT Fire Technology Laboratory, Espoo, Finland, August 11, 1992.
28. Mawhinney, J.R., "Characteristics of Water Mists for Fire Suppression in Enclosures," Proceedings of the
Halon Alternatives Technical Working Conference 1993, pp. 291-302, Albuquerque, New Mexico, May
11-13 1993.
29. Jackman, L.A., Nolan, P.F., and Morgan, H.P., "Characterization of Water Drops from Sprinkler Sprays,"
Proceedings of the First International Conference on Fire Suppression Research, Stockholm and Boras,
Sweden, May 5-8, 1992.
30. Holmstedt. G., "Extinction Mechanisms of Water Mist," Proceedings of the International Conference on
Water Mist Fire Suppression Systems, pp. 89-100, Boras, Sweden, November 4-5, 1993.
118
-------
31. Gameiro. V.M.. "Fine Water Spray Fire Suppression Alternative to Ilalon 1301 in Gas Turbine
Enclosures," Proceedings of the Halon Alternatives Technical Working Conference 1993, pp. 317-344,
Albuquerque, New Mexico, May 11-13, 1993.
32. Mawhinney, J.R., "Design of Water Mist Fire Suppression Systems for Shipboard Enclosures," Proceedings
of the International Conference on Water Mist tire Suppression Systems, pp. 16-45, Boras, Sweden,
November 4-5, 1993.
33. Jaekman, L.A., Glockling, J.L.D., and Nolan, P.F., "Water Sprays: Characteristics and Effectiveness,"
Proceedings of the Halon Alternatives Technical Working Conference 1993, pp. 263-274. Albuquerque,
New Mexico, May 11-13, 1993.
34. Martlila, P.K., 'Water Mist in Total Flooding Applications," Proceedings of the Halon Alternatives
Technical Working Conference 1993, pp. 309-316, Albuquerque, New Mexico, May 11-13, 1993.
35. Marker, T.R., On-board Cabin Water Spray System Under Various Discharge Configurations. Report
DOT/FAA/CT-TN91/42, Federal Aviation Administration, Atlantic City, New Jersey, October 1991.
36. Spring, D.J., Simpson, T„ Smith, D.P., and Ball, D.N., "New Applications of Aqueous Agents for Fire
Suppression," Proceedings of the Halon Alternatives Technical Working Conference 1993, pp. 303-308,
Albuquerque, New Mexico, May 11-13, 1993.
37. Hills, A.T., Simpson, T., and Smith, D.P., "Water Mist Fire Protection Systems for Telecommunications
Switch Gear and Other Electronic Facilities," Presented at the Water Mist Fire Suppression Workshop,
pp. 123-142, National Institute of Standards and Technology, Gaithersburg, Maryland, March 1, 1993.
38. Leonard, J.T., "An Investigation into the Use of Water Mist as a Halon Alternative in a Machinery Space
Application," NRL Memorandum Report, Naval Research Laboratory, Washington, DC, 1994.
39. Wighus, R., "Fine Water Spray System A Extinguishing Tests in Medium and Full Scale Turbine Hood,"
SINTEF NBL, Norwegian Fire Research Laboratory, Trondheim. Norway, 1993.
40. Cote, A.E., "Residential Quick-Response Sprinklers," Fire Protection Handbook, 16th ed., pp. 18-50/60,
NFPA, Quincy, Massachusetts,! 986
41 Hughes Associates. Lie., "MicroMist Fire Suppression Fire Performance Evaluation," Report to The
Reliable Automatic Sprinkler Co. Inc., March 22, 1994.
42. Tuomissari, M., "Suppression of Compartment Fires with a Small Amount of Water," Proceedings of the
International Conference on Water Mist Fire Suppression Systems, pp. 167-170, Boras, Sweden, November
4-5, 1993.
43. Ryderman, A„ "Development of Standards and Test Methods for Water Mist Systems," Proceedings of the
International Conference on Water Mist I ire Suppression Systems, pp. 8-15, Boras, Sweden, November 4-
5, 1993.
44. Wighus, R., Auric, P., Drangsholt, G.. and Stensaas, J.P., "Full Scale Water Mist Experiments,"
Proceedings of the International Conference on Water Mist Fire Suppression Systems, pp. 100-152, Boras,
Sweden, November 4-5, 1993.
45. Butz, J.R., French, P., and Plooster, M. "Application of Fine Water Mists to Hydrogen Deflagration."
Proceedings of the Halon Alternatives Technical Working Conference 1993, pp. 345-355, Albuquerque,
New Mexico, May 11-13,1993.
46. Birchall, J.D., "On the Mechanism of Flame Inhibition by Alkali Metal Salts," Combustion and Flame,
Vol. 14, pp. 85-96, 1970.
119
-------
47. Rosser, W.A., Inami, S.H., and Wise, H„ "The Effect of Metal Salts on Premixed Hydrocarbon Air
Flames," Combustion and Flame, Vol. 7, pp. 107-119, 1963.
48. Sheinson, R.S., Eaton, H.G., Zalosh, R.G., Black, B.H., Brown, R., Burchell, H., Salmon, G., and Smith,
W.D., "Fire Extinguishment By Fine Aerosol Generation," Presented at the 1993 International CFC and
Halon Alternatives Conference, Washington, DC, October 20-22, 1993.
49. Smith, E. A., Kimmel, E. C., Bowen, L. E., Reboulet. J. E., and Carpenter, R. L., "The Toxicological
Assessment of a Fire Suppressant and Potential Substitute for Ozone Depleting Subatances," Proceedings
of the Halon Options Technical Working Conference 1994, pp. 359-370, Albuquerque, New Mexico,
May 3-5, 1994.
50. Moore, T.A., Dierdorf, D.A., and Skaggs, S.R., Low-Ozone-Depleting Halocarbons as Total Flood Agents,
Volume 3: Intermediate-Scale Testing, EPA-600/R-95-150c, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, August 1995.
51. IMO MSC Circular 668, International Maritime Organization, London, England, United Kingdom, 1993.
52. IMO Safety of Life at Sea (SOLAS) Regulation Ef-2/12.4.1, International Maritime Organization, London,
England, United Kingdom, 1992.
53. ASME Code for Pressure Piping, B31, American Society of Mechanical Engineers, New York, New York,
1993.
120
-------
BIBLIOGRAPHY
ABB Stromberg Research Centre, "Withstand Voltage of Switchgears in the Presence of Operating Hi-fog Sprinkler
System," 9 AFX92-98, Vaasa, Finland, August 3, 1992.
Alport, R.L., "Incentive for Use of Misting Sprays as a Fire Suppression Agent," Presented at the Water Mist Fire
Suppression Workshop, National Institute of Standards and Technology, Gaithersburg, Maryland, March 1-
2, 1993.
Altman. R.L.," Extinguishing Fuel-Leak Fires with Dry Chemical," Technical Support Package ARC-11553, NASA
Ames Research Center, Moffett, California
Andrews, S.P., "Literature Review: Fire Extinguishing by Water Sprays," Fire Research Station, Building Research
Establishment, Borehamwood, United Kingdom, 1992.
Arvidson, M., "The Efficiency of Different Water Mist Systems in a Ship Cabin," Water Mist Instead of Halon ? An
International Conference on Water Mist Fire Suppression Systems, Boras, Sweden, November 4-5, 1993.
Arvidson, M., "Crib Fire Test in Principal Accordance with ISO/DIS," Swedish National Testing and Research
Institute, Boras, Sweden, 9) R30I89A, April 30, 1992.
Arvidson, M., "Tests with Marioff Hi-fog Fire Protection System in a Simulated Cable Duct," 91 R30141, Swedish
National Testing and Research Institute, Boras. Sweden, February 19, 1992.
AS'I'M L799, Standard Practice for Determining Data Criteria and Processing for Liquid Drop Size Analysis,
American Society for Testing and Materials, Philadelphia, Pennsylvania, 1987.
Bachalo, W.D. Bachalo, E.J., Hanscom. .T., and Sankar, S.V., "An Investigation of Spray Interaction with Large-scale
Eddies," Paper AIAA 93-0697, Presented AIAA 31st Aerospace Sciences Meeting, Reno, Nevada, January
11-14, 1993.
Bachalo, W.D., "Advances in Spray Drop Size and Velocity Measurement Capabilities for the Characterization of
Fire Protection Systems," Presented at the Water Mist Fire Suppression Workshop, National Institute of
Standards and Technology, Gaithersburg, Maryland, March 1-2, 1993.
Bachalo, W.D., and Houscr, M.J., "Phase Doppler Spray Analyzer for Simultaneous Measurements of Drop Size and
Velocity Distributions," Optical. Engineering, Vol. 23, No. 5, p. 583.
Bachalo, W.D., and Sankar, S.V.. "Analysis of the Light Scattering Interferometry for Spheres Larger Than the
Wavelength," Proceedings of the Fourth International Symposium on the Applications of Laser
Anemometry to Fluid Mechanics, Lisbon, Portugal, 1988.
Bachalo, W.D., Brena de la Rosa, A„ and Rudoff, R.C., "Diagnostics Development for Spray Characterization in
Complex Turbulent Flows," Paper 88-GT-241, Gas Turbines and Aeroengine Congress, Amsterdam, The
Netherlands. June 1988.
Bachalo, W.D., Rudoff, R.C., and Sankar, S.V., "Time-resolved Measurements of Spray and Velocity," Liquid
Particle Size Measurement Techniques, ed. Hirlcman, Bachalo, and Felton, ASTM STP1083, Philadelphia,
Pennsylvania, pp. 209-224, 1988.
121
-------
Bachalo, W.D., Rudoff, R.C., and Brenade la Rosa, A., "Mass Flux Measurements of a High Number Density Spray
System Using the Phase Doppler Particle Analyzer," Presented at AIAA 26th Aerospace Sciences Meeting,
Reno, Nevada, January 1988.
Bachalo, W.D., Rudoff, R.C., and Houser, M.J., "Laser Velocimetry in Turbulent Flow Field: Particle Response,"
Presented at AIAA 25th Aerospace Sciences Meeting, Reno, Nevada, January 1987.
Ball, D.N., Smith, D.P., and Spring, D.J., "New Applications of Water-based Agents for Fire Suppression in High
Risk Areas," Proceedings of the Halon Alternatives Technical Working Conference, pp. 186-205,
Albuquerque, New Mexico, 1991.
Beyler, C.L., "A Unified Model of Fire Suppression," Journal of Fire Protection Engineering, Vol. 4, No. 1,
pp. 5-16, 1992.
Bill, R.G. and Croc-e, P.A., "Perspectives on Fine Water Spray (Water Mist) Technology at Factory Mutual Research
Corporation," Water Mist Instead of Halon? — International Conference on Water Mist Fire Suppression
Systems, Boras, Sweden, November 4-5, 1993.
Bill, R.G., "Fire Performance Requirements for Fine Spray (Mist) Systems in Passenger Ship Public,
Accommodation, and Service Areas," Technical Report J.I. 0X0N7.RA, Factory Mutual Research
Corporation, Norwood, Massachusetts, July 1993.
Bill, R.G. and Hill, E.E., "Sprinkler Protection of Manufactured Homes with Cathedral Ceilings using Prototype
L.imited-Water-Supply Sprinklers," FMRC J.I. OXON8.RA, Federal Emergency Management Agency,
Factory Mutual Research Corporation, Norwood, Massachusetts, June 1993.
Bill, R.G. and Kung, H., "Evaluation of the Suppression Capability of Residential and Quick Response Sprinklers,"
FMRC J.l. OQ5NO-8.RA 070(A), prepared for Federal Emergency Management Agency, Factory Mutual
Research Corporation, Norwood, Massachusetts, December 1990.
Bill, R.G., Kung, H., Brown, W.R., and Hill, E.E., "Effects of Cathedral and Beamed Ceiling Construction on
Residential Sprinkler Performance," J.I. OM3N5.RA(3), Factory Mutual Research Corporation, Norwood,
Massachusetts, February 1988.
Bill, R.G., Kung, H., Ilill. E.E., Chan, T„ and Brown, W.R., "The Development of a Limifcd-Water-Supply
Sprinkler for Mobile Homes," J.I. 0T157.RA, Factory Mutual Research Corporation, Norwood,
Massachusetts, April 1992.
Budnick, E.B., and Fleming, R.P., "Developing an Early Suppression Design Procedure for Quick Response
Sprinklers," Fire Journal, November/December 1989.
Budnick, E.K., "Estimating die Effectiveness of State-of-the-Art Detectors and Automatic Sprinklers on Life Safety
in Residential Occupancies," Fire Technology, August 1984.
Budnick, E.K., "Mobile Home Fire Studies: Summary and Recommendations," NBSIR 79-1720, National Bureau of
Standards, Gailhersburg, Maryland, 1979.
Budnick, E.K., and Fleming, R.P., "How Quick Response Sprinklers Perform and What It Means for Their
Application," Fire Journal, September/October 1989.
Budnick, E.K., and Walton, W.D., "Quick Response Sprinklers in Office Configurations: Fire Test Results," NBSIR
88-3695, National Bureau of Standards, Gaithersburg, Maryland, 1988.
122
-------
Rudnick, E.K., DiNenno, P.J., and Scheffey, J.L., Sprinklers and Other Fire Control Methods, Encyclopedia of
Architecture: Design, Engineering, and Construction, Vol. 4, John Wiley & Sons, Inc., New York. NY
1989.
Burgess, D. and Zabetakis, M.G., "Fire and Explosion Hazards Associated with Liquefied Natural Gas," U.S.
Department of the Interior, Bureau of Mines, Washington, DC, 1963.
Campbell, C., "Huge Rise in Air Fire Safety Research Budget," Fire International, Vol. 13, No. 119. pp. 22-26,
October/November 1989.
Carey, W.M. and Dosedlo, L.J., "Preliminary Report of the Quick Response Sprinkler Project, Group 2 Performance
Tests Phase IARDD Tests," National Fire Protection Research Foundation, Quincy, Massachusetts, August
17, 1987.
Carey, W.M., "Final Report of Sprinkler Research on Low Water Supply Sprinklers," Contract No. EMW-89-R-
3083, Underwriters Laboratories, Inc., Project 89NK25259/NC188, Norlhbrook, Illinois (sponsored by
FEMA/USFA), December 1990.
Carey, W.M., "Report of the Quick Response Sprinkler Project Group 2 Performance Tests Phase IIAADD Tests
Sponsored by the National Fire Protection Research Foundation," Quincy, Massachusetts, March 25, 1988.
Carhart, H.W. and Fielding, G., "Suppression - Why Not Water?," NRL Memorandum Report 3435, Naval Research
Laboratory, Washington, TXT, 1977.
Carhart, H.W., Shcinson, R.S., Tatem, P.A., and Lugar, J.R. (1992), "Fire Suppression Research in the U.S. Navy,"
Proceedings of the First International Conference on Fire Suppression Research, Stockholm and Boras,
Sweden, May 5-8, 1992.
Carhart, H.W., Sheinson, R.S., Tatem, P.A., and Lugar, J.R.," Fire Suppression Research in the U.S. Navy,"
Proceedings of the First International Conference on Fire Suppression Research, Stockholm and Boras,
Sweden, May 5-8, 1992.
Chow, W.K., "On the Evaporation Effect of a Sprinkler Water Spray," Fire Technology, November 1989.
Chow, W.K., and Fong, N.K., "Numerical Studies on the Sprinkler Fire Interaction Using Field Modeling
Technique," Interflam "90, Uni%'ersity of Kent, Canterbury, England, Inter-Science Communications
Limited, London, England, 1990.
Coppalle, A., Nedelka, D., and Bauer, B., "Fire Protection: Water Curtains," Fire. Safely Journal, Vol. 20, pp. 241 -
255, 1993.
Cousin, C.S., "Developments in the Use of Water Fog," International Firex 93 Exhibition and Conference, London,
England, May 12, 1993.
Cousin, C.S., "The Potential of Fine Water Sprays as Halon Replacements for Fires in Enclosures," Water Mist
Instead of Halon?—International Conference on Water Mist Fire. Suppression Systems, Boras, Sweden,
November 4-5, 1993.
Cox, G. and Moss, J.B., "Fire Science and Aircraft Safety," Aircraft Fire Safety, AGARD, NATO, Sintra, Portugal,
1989.
de Ris, J., Private Communication, Factory Mutual Research Corporation, Massachusetts, June 1993. See also,
"Extinguishment of Fires by Total Flooding with Chemically Inert Gases," Technical Report J.I.
0W1EI.RC, Factory Mutual Research Corporation, Norwood, Massachusetts, April 1993 (proprietary).
123
-------
Dodge, L.G. and Schwalb, J.A., "Fuel Spray Evolution: Comparison of Experiment and CFD Simulation of
Nonevaporating Spray," Presented as Paper 88-GT-27, Gas Turbines and Aeroengine Congress and
Exposition, ASME, Amsterdam, June 1988.
Drysdale, D„ An Introduction to Fire Dynamics, John Wiley and Sons, Inc., New York, New York, 1985.
Edwards, R.D.. "I;ire Tests with High Pressure Water Protection Systems," Interoffice Correspondence, Res. File
14709, Factory Mutual Research Corporation, Norwood, Massachusetts, July 11, 1968 (proprietary).
Evans, D.D. and McCaffrey, B.J.. "Control of Blowout Fires with Water Sprays," U.S. Department of the Interior,
Minerals Management Service, Washington, DC, 1984.
Evans, D.D. and Pfenning, D., "Water Sprays Suppress Gas-well Blowout Fires," Oil and Gas Journal, Vol. 8, No.
17, pp. 80-86, April 29 1985.
Ewirig, C.T., Faith, F.R., Hughes, J.T., and Carhart, H.W., "Flame Extinguishment Properties of Dry Chemicals,"
Fire TechnologyMo\. 25, No. 2, May 1989.
Ewing, C.T., Faith, R.R., Romans, J.B., and Hughes, J.T., "Extinguishment Properties of Dry Chemicals: Extinction
Weights for Small Diffusion Pan Fires and Additional Evidences for Flame Extinguishment by Thermal
Mechanisms," Journal of Fire Protection Engineering, Vol. 4, pp. 35-52, 1992.
Ewing, C.T., Hughes, J.T., and Carhart, H.W., Dry Chemical Development—A Model for the Extinction of
Hydrocarbon Flames, NRL Memorandum Report 5267, Naval Research Laboratory, Washington. DC,
February 8, 1984.
Ewing, C.T., Hughes, J.T., and Carhart, H.W., "The Extinction of Hydrocarbon Flames Based on the Heat-
absorption Processes which Occur in Them," Fire and Materials, Vol. 8, No. 3, 1984.
Factory Mutual Research Corporation, "Approval Standard for Residential Automatic Sprinklers," Class Number
2030," Factory Mutual Research Corporation, Norwood, Massachusetts, September 1983.
Factory Mutual Research Corporation, "Draft Approval Standard for Residential and Limited Water Supply
Automatic Sprinklers," Class Number 2030, Factory Mutual Research Corporation, Norwood,
Massachusetts, January 27, 1993.
Federal Communications Commission, "Network Reliability: A Report to the Nation—The Recommendations of the
Federal Communications Commission's Network Reliability Council," National Engineering Consortium.
Washington, DC, June 10-11, 1993.
Friedman, R„ " Mechanisms of Flame Extinguishment by Dry Powders," Journal of Fire Protection Engineering,
Vol. 5, pp. 29-31, 1993.
Friedman, R„ "Some Properties of Water Fog as a Fire Suppressant," Interoffice Correspondence, Factory Mutual
Research Corporation, Norwood, Massachusetts, September 29, 1989 (proprietary).
Galea. E.R., and Markatos, N.C., "Modeling of Aircraft Cabin Fires," Fire Safety Science—Proceedings of the
Second International Symposium, Tokyo, 1988.
Gardiner, A.J.P.D., "The Mathematical Modeling of the Interactions Between Sprinkler Sprays and the Thermally
Buoyant Layers of Gases from Fires," Council for National Academic Awards (U.K.), order number
BRDX86549, London, United Kingdom, 1988.
Gaskill, J.R. and Murrow, J.I,., "Fire Protection of 1 IK PA Filters by Using Water Sprays," Lawrence Livermore
Laboratory, University of California, Livermore, CA, 1972.
-------
Girard, P. and Bjarnsholt, O., "Design Manual for Fire-Scope 2000 Systems (Draft), Ginge Kerr a/s, Copenhagen,
Denmark, 1992.
Hanauska, C., "An Overview of Water Mist Fire Suppression System Technology," The 1993 International CFC and
Halon Alternatives Conference Proceedings, Washington, DC, October 20-22, 1993.
Hanauska, C.P., and Back, G.G., Halons: Alternative Fire Protection Systems, An Overview of Water Mist Fire
Suppression Systems Technology, Hughes Associates, Inc., Columbia. Maryland, 1993.
Hayes Jr., W.D., Literature Survey on Drop Size Data, Measuring Equipment, and a Discussion of the Significance
of Drop Size in Fire Extinguishment, National Institute of Standards and Technology, Gaithersburg,
Maryland, 1985.
Henderson, N.C., Riegel, P.S., Patton. R.M., and Larcomb, D.B,, Investigation of Low-Cost Residential Sprinkler
Systems, Batlelle Columbus Laboratories, Columbus, Ohio, June 1978.
Heselden, A.J.M., and Hinkley, P.J., "Measurement of Transmission of Radiation through Water Sprays," Fire
Technology, 1 (2), pp. 130-137, May 1965.
Heskestad, G., Kung, H.-C, and Todtenkopf, N.F., Air Entrainment into Water Sprays and Spray Curtains, Factory
Mutual Research Corporation, Norwood, Massachusetts, 1976.
Hill, J.P., "Investigation of Automatic Sprinklers to Protect Digital Telecommunication Switching Equipment,"
Technical Report J.I. 0P1R2.RR, Factory Mutual Research Corporation, Norwood. Massachusetts, June
1988 (proprietary).
Hindsdale Central Office Fire Final Report, Joint Report of Office of the State Fire Marshal and Illinois Commerce-
Commission Staff, Springfield, Illinois, March 1989.
Jackman. L.A., "Mathematical Model of the Interaction of Sprinkler Spray Drops with Fire Gases," Proceedings of
the First International Conference on Fire Suppression Research, Stockholm and Boras, Sweden, May 5-8,
1992.
Jacobsen, S.E., "Approval of Water Mist Systems on Ships. Consideration of Equivalency to Sprinkler and Water
Spray Systems," Presented at the International Conference on Water Mist Fire Suppression Systems, Boras,
Sweden, November 4-5, 1993.
Kaleta, A.. "Effect of Drop Size on Extinguishing Effectiveness of Water Spray," Archiwum Combustionis, Vol. 6,
No. 3, 1986.
Khan, M.M., and Tewarson, A., "Characterization of Hydraulic Fluid Spray Combustion," l'ire Technology, Vol. 27,
No. 4, November 1991.
Kokkala, M.A., "Extinction of Liquid Pool Fires with Sprinklers and Water Sprays," Valtion Teknillinen
Tutkimuskeskus, Statens Teniska Forskningsccntral (Technical Research Centre of Finland), Espoo, 1989.
Kung, H„ "Residential Sprinkler-Protection Study," FMRC Serial No. 22442 RC75-T-41, prepared for National
Bureau of Standards, Factory Mutual Research Corporation, Norwood, Massachusetts, November 1975.
Kung, H., Haines, D., and Green, J. Jr., Development of Low-Cost Residential Sprinkler Protection, Factory Mutual
Research Corporation, Norwood, Massachusetts, February 1978.
Kung, H., Spaulding, R., and Hill E E. Jr., Residential. Fire Tests with Sidewall Sprinklers, FMRC J.I. OJ1NO.RA
070(A), Federal Emergency Management Agency, Factory Mutual Research Corporation, Norwood,
Massachusetts, December 1985.
125
-------
Kung, H.. Spaulding, R., and Hill EE. Jr., Sprinkler Performance in Residential Fire Tests, FMRC Serial No. 22574
RC80-T-16. Federal Emergency Management Agency, Factory Mutual Research Corporation, Norwood,
Massachusetts, July 1980.
Kung, H., Spaulding, R.D., Hill, E.H. Jr., and Symonds, A.P., Field Evaluation of Residential Prototype Sprinkler
Los Angeles Fire Test Program, FMRC J.I. 0E0R3.RA(1) 070(A), Federal Emergency Management
Agency, Factory Mutual Research Corporation, Norwood, Massachusetts, February 1982.
Lawson, J.R., Walton, W.D., and Evans, D.D., "Measurement of Droplet Size in Sprinkler Sprays," National
Institute of Standards and Technology, Gaithersburg, Maryland, 1988.
Lee, S. and Sichel M., "Evaporation of Liquid Droplets in a Confined Medium," Chemical and Physical Processes
in Combustion, 20th Fall Technical Meeting, Combined Technical Meetings of The Combustion
Institute/Eastern States Section and NBS/CFR Annual Conference on Fire Research, Gaithersburg,
Maryland, 1987.
Lev. Y., "Cooling Sprays for Hot Surfaces," Fire Prevention, No. 222, pp. 42-47, 1989.
Levine, R.S., "Navy Safety Center Data on the Effects of Fire Protection Systems on Electrical Equipment," National
Institute of Standards and Technology, Gaithersburg, Maryland, 1991.
Lewis, D. and von Elbe, G„ Combustion, Flames and Explosion of Gases, Third Edition, Academic Press, Orlando,
Florida, 1987.
Liu, S.T., "Analytical and Experimental Study of Evaporative Cooling and Room Fire Suppression by Corridor
Sprinkler System," National Bureau of Standards (now NIST), Gaithersburg, Maryland, 1977.
Lloyd's Register of Shipping, letter from D.G. Gaskell to Ginge-Kcrr AS, Denmark, regarding Lloyd's Register
approval covering Fine Water Spray Systems for Machinery Spaces of Category A, I April 1993.
I.ugar, J.R., "Preliminary Test Results of Fine Water Mist Fire Protection Systems Study," David W. Taylor Naval
Ship Research and Development Center, Bethesda, Maryland, 1979.
Lugar, J.R., "Status Report of Fine Water Mist Fire Protection," David W. Taylor Naval Ship Research and
Development Center, Bethesda, Maryland, 1980.
Lugar, J.R., "Water Mist Fire Protection," David W. Taylor Naval Ship Research and Development Center,
Bethesda, Maryland, 1979.
Lugar, J.R., Fornsler, R.O., Carhart, H.W., and Fielding, G.H., "Flame Extinguishment by Waterfogs and Sprays,"
Fifth Quadripartite Conference IEP ABCA-7. October 1978.
Marioff, K. and Turner, A., Marioff Hi-fog System, Marioff Company, Finland, 1991.
Matson, A.F. and Dufour, R.E., The Mechanism of Extinguishment of Fire by Finely Divided Water, NBFU
Research Report No. 10, Underwriters Laboratory, Northbrook, IL, 1955.
Mawhinney, J.R., "Engineering Criteria for Water Mist l;ire Suppression Systems," Presented at the Water Mist
Fire Suppression Workshop, National Institute of Standards and Technology. Gaithersburg, Maryland,
March I. 1993.
Mawhinney, J.R., "Waterfog Fire Suppression System Project: Full Scale Fire Tests Summary Report, ND Project
No. DNASE40291. National Research Council Canada, Ottawa, Ontario. 1993.
126
-------
Mawhinncy, J.R. and Dlugogorki, B.Z., "Experiment Report Comparing Two Methods of Measurement of Drop Size
Distributions in Sprays," NRC/IRC Internal Report, National Research Council, Ottawa, Canada, 1993.
Milke, J., Evans, D., and Hayes, J.W., "Water Spray Suppression of Fully-Developed Wood Crib Fires in a
Compartment," National Institute of Standards and Technology, Gaithersburg, Maryland, 1988.
National Board of Fire Underwriters, "The Mechanisms of Extinguishment of Fire by Finely Divided Water,"
N.B.F.U. Research Report 10, The National Board of Fire Underwriters, New York, New York, 1955.
National Fire Protection Association, "NFPA 13D, Standard for Sprinkler Systems In One- and Two-Family
Dwellings 1991," NFPA, Quincy, Massachusetts.
Notarianni. K.A. and Jason, N.H., "Water Mist Fire Suppression Workshop, March I-2, 1993: Proceedings,"
NISTIR 5207, National Institute of Standards and Technology, Gaithersburg, Maryland, June 1993.
Oldenburg, J.R. and Ide, R.F., "Comparison of Two Droplet Sizing Systems in an Icing Wind Tunnel," AJAA 90-
0668, January 1990.
Papavergos, P.G., "Fine Water Sprays for Fire Protection - A Halon Replacement Option," British Petroleum
Ventures, BP Research, Sunbury Research Centre, United Kingdom, 1990.
Papavergos, P.O., "Offshore Firespray Development for Turbine Hood Fire Protection—Potential Fire Scenarios,"
Record Note No. 229 756," British Petroleum Ventures. BP Research, Sunbury Research Centre, United
Kingdom, 1992.
Papavergos, P.O., "The Design of Fine Water Spray Nozzles for Fire Protection," BP Research Branch Report
No. 138 423/M." British Petroleum Ventures, BP Research, Sunbury Research Centre, United Kingdom,
1992.
Persson, H. and Wickstroem, U., Effect of Film Formine Foam Agent on Water Sprinklers, Statensprovingsanstalt,
SP RAPP 1982:21, 1982.
Rasbash, D.J.. "The Extinction of Fires by Water Sprays," Fire Research Abstracts and Reviews, Vol. 4, Ch. 1 and
2, pp. 28-52, 1962.
Rasbash, D.J., Rogowski, Z.W.. and Stark, G.W.V., "Mechanisms of Extinction of Liquid Fires with Water Spray,"
Combustion and Flame, Vol. 4, pp. 223, 1960.
Ravigururajan, T.E. and Beltrav, M.P., "A model for Attenuation of Fire Radiation through Water Droplets," Fire
Safety Journal, Vol. 15, pp. 171-181, 1989.
Reischl, U., "Water Fog Stream Heat Radiation," Fire Technology, Vol. 15, pp. 262-270, November 1979.
Rosander, M. and Giselsson, K., "Making the Best Use of Water for Fire Extinguishing Purposes," Fire,
pp. 43-46, October 1984.
Rudoff, R.C., Kamemoto, D.Y., and Bachalo, W.D., "Effects of Turbulence and Number Density on the Drag
Coefficient of Droplets," Presented as Paper AIAA 91-0074, 29th Aerospace Sciences Meeting, AIAA,
Reno, Nevada, January 7-10, 1991.
Sankar. S.V., Weber, B.J.. Kamemoto, D.Y., and Bachalo, W.D., "Sizing Fine Particles with the Phase Doppler
Interferometric Technique," Applied Optics, Vol. 30, No. 33, November 1991.
-------
Sarkos, C.P., "Development of Improved Fire Safely Standards Adopted by the Federal Aviation Administration,"
AGARD-CPP-467, Propulsion and Energetics Panel 73rd Symposium on Aircraft Fire Safety, Sintra,
Portugal, May 22-26, 1992.
Sarkos, C.P., "Evaluation and Optimization of an On-board Water Spray Fire Suppression System in Aircraft,"
Presented at the Water Mist Fire Suppression Workshop, National Institute of Standards and Technology,
Gaithersburg, Maryland, March 1-2, 1993.
Simpson, T. and Smith, D.P., "A Fully Integrated Water Mist Fire Suppression System for Telecommunications and
Other Electronics Cabinets," Proceedings of the International Conference on Water Mist Fire Suppression
Systems, pp. 153-166, Boras, Sweden, November 4-5, 1993.
Simpson, T., "Water Mist Fire Protection Systems for Telecommunication Switch Gear and Other Electronics
Facilities," Presented at the Water Mist Fire Suppression Workshop, National Institute, of Standards and
Technology, Gaithersburg, Maryland, March 1-2, 1993.
Spaulding, R.D. and Hill, E.E., "Communities Sprinkler Fire Tests, Scottsdale, Arizona," FMRC J.I. OG5NO.RA
070(A), Factory Mutual Research Corporation, Norwood, Massachusetts, July 1982.
Spurny, K.R., "Physical Characterization of Single Particles and of Particle Collectives," Physical Characterization
of Individual Airborne Particles, pp. 31-34, 1986.
Swedish National Testing & Research Institute, "Cabin and Public Space Fire Tests with Marioffs Ili-fog Fire
Protection System," 91 R3014I, Boras, Sweden, February 19, 1992.
Swedish National Testing & Research Institute, "Crib Fire Test in Principal Accordance with ISO/DIS 6182-1.2,"
91 R30189A, Boras, Sweden, April 30, 1992.
.Swedish National Testing & Research Institute, Tests in Simulated Ship's Engine Room with a Hi-fog Fire
Protection System, 91 R30189, Boras, Sweden, July 28, 1992.
Tamanini, F., "A Study of the Extinguishment of Vertical Wood Slabs in Self-Sustained Burning by Water Spray
Application," Combustion Science and Technology, Vol. 14, pp. 1-15, 1975.
Tewarson, A. and Khan, M., "Electrical Cables -Evaluation of Fire Propagation Behavior and Development of
Small-scale Test Protocol," Technical Report J.I. 0M2E1.RC, Factory Mutual Research Corporation,
Norwood, Massachusetts, January 1989 (proprietary).
Thomas, G.O., Edwards, M.J., and Edwards. D.H., "Studies of Detonation Quenching by Water Sprays,"
Combustion Science, and Technology, Vol. 71, pp. 233-245, 1990.
Thompson, N.J., Fire Behavior and Sprinklers, National Fire Protection Association, Boston, Massachusetts, 1974.
Tuomissari, M., Enclosed Space Fire Suppression Tests, PAL 2206/92, VTT Fire Technology Laboratory, Espoo,
Finland, October 23, 1992.
Tuomissari, M., Withstand Voltage of Switch Gears in the Presence of Operating Hi-fog Fire Protection System,
9 AFX92-98, ABB Stromberg Research Centre, Vassa, Finland, August 3, 1992.
LJnderwriters Laboratories, Inc., Final Report of Sprinkler Research, Under Contract EMW-89-R-3083 for the
Period of October 1, J 989 - September 30, 1990, Federal Emergency Management Agency, Underwriters
Laboratories, Northbrook. Illinois, Dccemher 18, 1990.
Uriano, G.A., "Advanced Technology Program: A Status Report," Presented at the Water Mist Fire Suppression
Workshop, National Institute of Standards and Technology, Gaithersburg, Maryland, March 1-2, 1993.
128
-------
VTT Fire Technology Laboratory, "Enclosed Space Fire Suppression Tests," PAL 2206/92, Espoo, Finland, October
23, 1992.
VTT Fire Technology Laboratory, "Extinguishing Tests of Simulated Computer Room Fires by a Hi-fog Sprinkler
System," PAL 2196/92, Espoo, Finland, August 11, 1992.
VTT Fire Technology Laboratory. "Fire Suppression Tests in Simulated Ship's Engine Room with a Hi-fog Fire
Protection System," PAL 2210/92, Helsinki, Finland, November 16, 1992.
VTT Fire Technology Laboratory." Manual Suppression of a Postflashover Fire with Hi-fog Nozzles," PAL
2204/92, Espoo, Finland, September 11, 1992.
Wighus, R., "Active Fire Protection - Extinguishment of Enclosed Gas Fires With Water Sprays." SINTEF Report
STF25 A91028, Trondheim, Norway 1991.
Wighus, R., "Fine Water Spray Against Hydrocarbon Fires," S1NTEF—Norwegian Fire Research Laboratory,
Trondheim, Norway, 1993.
Yao, C., "Applications of Sprinkler Technology - Early Suppression of High-challenge Fires with Fast-response
Sprinkler," Fire Safety and Science Engineering, ASTM STP 882, T.Z. ilarmathy, ed.. Philadelphia.
Pennsylvania, 1985, pp. 354-376.
YARD Memorandum No. 4998, "Review of the Use of Waterfog as a Firefighting Agent," British Ministry of
Defense - Navy, Bath, England, September 1986.
YARD Report No. 3590, "Waterfog Evaluation Trials," Vols. 1 to 3. British Ministry of Defense - Navy, Bath,
England, August, September, October 1988.
YARD, "Project Hulvul: Waterfog Evaluation Trials," British Ministry of Defense - Navy, Bath, England, 1988.
You, H Z., Kung, H-C, and Han, Z., "Spray Cooling in Room Fires," Technical Report J.I. 0J0N9.RA, Factory
Mutual Research Corporation, Norwood, Massachusetts, March 1986 (proprietary).
Zhu, J.Y., Rudoff, R.C., Bachalo, E.J., and Bachalo, W.D., "Number Density and Mass Flux Measurements Using
the Phase Doppler Particle Analyzer in Reacting and Non-reacting Swirling Flows," Presented as Paper
AIAA 93-0361, 31st Aerospace Sciences Meeting and Exhibit, Reno. Nevada, January 11-14, 1993.
129
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APPENDIX A
DEVELOPMENT OF THE FRAIJNHOFER SMALL ANGLE DIFFRACTION INSTRUMEN T
INTRODUCTION
As part of the development of the aerosol test chamber (ATC), a Fraunhofer (small angle forward)
diffraction (FD) instrument for measuring water mist droplet size and si/.e distribution was proposed for development
with this project. With improved personal computer capabilities and improvements in possible detector elements
that have come onto the market since Malvern Instruments Ltd. brought out their line of particle analyzers, NMFJRI
sought to develop a versatile, low cost Fraunhofer diffraction-based particle analyzer utilizing off-the-shelf
components. The (minimal) operational off-the-shelf components required for this system were a 4-inW helium-
neon laser, beam expander, spatial filter, collimating lens, focusing lens, IleNe line filter, neutral density filter, and a
linear variable density filter. The only speciality item used to develop the system was an over-the-counter hand
scanner that was converted to a charged-couple-devicc (CCD) detector, which will be described later in this report.
The small lightweight detector system allows aerosol measurements to be taken in cramped positions where other
instruments would not fit (Figure A-l).
10.2 c
c2>
\
6.3 cm
7.6 cm
\
25.4 cm
Figure A-1. Exterior view of a Fraunhofer Diffraction Detector.
130
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Since the development of the NMERI Fraunhofer (small angle forward) diffraction instrument is a
significant advancement due to its .small size, versatility, multi-station capability, and potential future applications in
measuring mists and particulate aerosols, this section on the Fraunhofer instrument's development and operation is
included. The instrument's small size and its potential ability to couple two detectors with different focal length
lenses together and thereby simultaneously scan aerosol particles over twice the present measuring range of any
present laser-based instrument is a significant step in improved analytical capability.
REVIEW OF AEROSOL MEASUREMENT TECHNIQUES
OVERVIEW
As part of the development of the ATC for use in Task 2, a review of measurement methods appropriate for
aerosol clouds was conducted. This part of the report concentrates on the measurement of particle size and size
distributions by methods that are appropriate for aerosol clouds. Thus, techniques involving flow obstacles such as
hot wires, sieves or meshes, and impact effects are not considered. Particle velocity and velocity distribution,
particle size and size distribution, and their simultaneous measurement in aerosols are usually based on optical
methods, especially since the advent of the laser (A-l).
Three widely utilized, non-perturbing optical methods have been employed for the measurement of particle-
size distributions in aerosol flows:
1. Phase Doppler Laser Interferometry (PD)
2. Dual Beam Laser Light Scattering Interferometry Combined with Optical Beam Visibility
Measurements (LIV)
3. Fraunhofer (Small Angle Forward) Diffraction (FD)
The modern PD method, which evolved from the LIV methodology, is currently the most common one for
studying aerosol clouds. All three methods are restricted to particles of diameter larger than approximately 2 |im, or
greater than about four times the wavelength of the measurement for optical radiation. Droplets of diameter greater
than 1 mm have been successfully measured. Particles of diameter less than about 1/10 of the measuring radiation
can be analyzed by use of Rayleigh scattering. Particles of diameter closer to the measurement radiation wavelength
must be examined in light of Mie scattering theory. These present significant complications in both instrumentation
and interpretation of results.
The. PD and LIV methods provide measurements on single particles that pass through quite small volumes
defined by the focused intersection of two equal intensity laser beams. Volumes are of the order of 0.01 by 0.01 by
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0.1 cm or 10"-' cm-1. Due to problems attendant to accurate definition of focal volumes associated with long focal
length lenses, a practical limitation to the separation from the final focusing lens to the sampling volume is around
50 cm. In both methods, large angle scattering is analyzed and mathematical relationships arc derived to relate the
time resolved measurements to both particle size and particle velocity. Size and velocity distributions are then
obtained by the statistical analyses of large numbers of individual particle measurements. In both types of
measurements, the particle size and velocity distributions and absolute number densities are obtained.
One additional restriction on the PD method is that the individual droplets must be transparent to the
probing radiation. For the case of water droplets and an argon laser with a 514.5-nm wavelength, this restriction is
of no consequence.
In order that data be accumulated in a reasonable time and that particle scattering from the beam outside the
focal volume does not distort the results, aerosols should have absolute light transmission through the spray of
between -50 and -95 percent. Higher transmissions require prohibitively long times, and lower transmissions yield
results biased in an uncertain manner toward lower velocities and larger particle diameters. Also, the PD and LIV
methods require lasers of 2 to 10 watts power as compared with the FD's requirements of only 2 to 10 inW.
The FD approach differs significantly from both the LIV and the PD methods, in both experimental
methodology and theoretical data interpretation. The FD method analyzes the small forward angle (less than 10 to
12 degrees) scattering, which originates in the large volume defined by a parallel beam of optical radiation. Thus, a
volume having 1 cm^ cross section and 100 to 1000 cm in length (V = 100 cm^ to 1000 cm^), can be studied. All
particles present in the defined volume contribute to the scattered radiation and consequently the particle size-
distribution is measured; however, absolute number density cannot be determined. Of course, much smaller volumes
can be analyzed. The FD method provides no information concerning particle velocity or velocity distributions.
FRAUNIIOFER DIFFRACTION (FD) METIIOD OF PARTICLE SIZING
A review article by Weiner discusses in detail the theory and practice of the FD method of particle analysis
(A-2). The experimental set up for use of this technique is shown in Figure A-2. The detector takes the form of a
series of concentric photosensitive rings as shown in Figure A-3.
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Beam
expander
Particle
field
Detector in
focal plane
of the lens
2 mW He-NE laser
Fourier
Fourier
transform
lens
Figure A-2. Optical schematic for Fraunhofer apparatus.
Figure A-3. Schematic of detector showing sample diameters S, and S2.
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A commercially available particle sizing instrument based on Fraunhofer diffraction theory is manufactured
by Malvern Instruments. Ltd. of the United Kingdom and is referred to in the literature as the Malvern (A-3). The
articles cited provide an extensive description and discussion of this instrument and its strengths and limitations (A-l
through A-5). A summary of conclusions concerning the Fraunhofer diffraction theory method is presented below.
1. The Malvern instrument and variations are very versatile. They can be used for size distribution
analysis of particles or droplets suspended or flowing in any clear liquid, conducting or
nonconducting, or when particles or droplets are airborne. By varying the focal length and size of the
Fourier transform lens, a large range of particle sizes can be evaluated.
2. The measurement, like most optical measurements, is nonintrusive. No probe disturbs (he flow to
introduce sampling errors.
3. In the range where Fraunhofer diffraction theory is applicable, no calibration is necessary, and the
results are independent of refractive index, to an accuracy within five percent. Below about 10 um,
however, a systematic error may occur. This does not affect precision or selectivity, both of which are
prerequisites for process control.
4. Repeatability is within three percent. Resolution is good, provided a lens of the correct focal length is
used. In the largest size ranges, resolution is only fair.
5. The Fraunhofer diffraction-based instruments are easy to set up and to operate. Typically,
measurements require a few seconds, and results may be obtained in a few minutes at most.
6. Although it is not possible to use the technique when the transmittance is low, the range of
concentration over which results are obtainable is competitive with other techniques.
7. The technique is not a single particle counter. It does not measure at a single point and, at the present
time, it is not useful for absolute concentration measurements. It does, however, give an ensemble
average over a large number of particles rapidly and over a region of space. In the majority of cases,
this type of averaging is sufficient and often necessary.
8. Particle shape is not measured. Results are often in terms of an orientation-averaged effective size
distribution.
9. Measurements are biased toward slower moving particles. This is true for any instrument sensitive to
the number of particles per unit volume of space rather than to flux. However, for particles moving at
the same or nearly the same speed, which is true for the vast majority of liquid-borne particles, the
effect is rarely significant.
10. The equivalent depth of field is very large. There is a vignetting problem, which is only significant for
the smaller sizes when using very long path lengths far from the receiving lens.
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11. In the data analysis, it is assumed that the density is the same for all particles, i.e., independent of size.
Fur a mixture where this is not true, errors will arise.
If this technique is implemented, it is recommended that the complex and expensive annular segmented
detector be replaced by a CCD camera chip. A frame grabber could be employed to digitize the information of the
diffraction pattern, and a computer program could easily be employed to analyze the information with respect to
annular diffraction regions.
The accurate location of the central spot onto the detector array could be performed by observing the
central laser spot at substantially attenuated conditions. A very small occulting mask could then be accurately placed
onto the CCD camera chip to prevent blooming at the full laser power employed for data taking.
LASER INTERFEROMETRY! VISIBILITY (LIV)
This method of particle size measurement is an outgrowth of the standard laser Doppler velocity
measurement technique. The extension provides a second set of simultaneous data from which a particle size can be
established.
Laser Doppler velocity measurements are made on single particles, and velocities are statistically summed
over many particles to establish a particle velocity distribution. Of course, determination of the number of such
measurements, together with information on the effective measurement volume, also provides information on particle
densities, but not on their sizes. An article by Farmer lays out the basis for such a combination measurement (A-6).
Figure A-4 shows the experimental details of the measurement.
Into'fwence Fthges
Contois
Enlarged View
of R^glm of
Cioss Foc:.tR Point
Beam
Splitting
.asnr
Aperature
N #
PhDto-rr.u!!!plter
n. Tube
Se f Aligning
iransmittlng
Optics
Signal
Processor
Figure A-4. Laser interferometry/visibility (LIV) experimental setup.
135
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The "pedestal" or low frequency component of the signal can be related to the particle diameter, while the
"Doppler" or high frequency component is related to particle velocity. Pedestal amplitude, when compared to the
amplitude when there is no particle in the measurement volume, is often referred to as the signal visibility, hence the
designation of the method as one involving visibility. The difference in visibility when a small particle crosses
through the measurement volume's center and when a large particle crosses the periphery of the measurement volume
is very subtle and leads to significant errors in application of the method. The general solution has been to employ
holographic spatial filters to convert the normal Gaussian beam cross section into a constant amplitude cross section
known as a "top hat" beam. This approach is illustrated and discussed in cited references (A-7, A-8).
The transition works that led to the development of the phase Doppler method (PD) for simultaneous
particle velocity and size determinations have been published by Hess and Li (A-9) and Bachalo (A-10).
PHASE DOPPLER (PD) PARTICLE SIZE AND VELOCITY DETERMINATIONS
Three references give, in chronological order, the theoretical and experimental development of the PD
method of simultaneous particle si/.e and velocity determinations (A-l I through A-13). Figure A-5 shows the
experimental arrangement (and the geometry) that was analyzed.
MEASUREMENT
VULUMt
LASER
BEAM
SPLITTER
\ DET 1
^ DET 2
DET 3
Figure A-5. Phase Doppler (PD) experimental arrangement.
Figure A-6 shows the scattered light interference pattern produced by a droplet in the measurement volume.
Figure A-7 shows a schematic for the receiver apparatus configuration that was developed for maximizing the useful
information that can be derived from a PD analysis.
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Figure A-6. Scattered light interference pattern.
3.5 mm
30.5 mri^
52.5 mm
74.4 mm
3.5 mm
101.5 mm
Figure A-7. Schematic for the Three-detector aperture for PD measurements.
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Cross-check data and theoretical analyses validating the PL) measurements relative to those performed by
both LIV and FD devices are available (A-14, A-15).
The major constraint of the PD system is that measurements are restricted to applications involving
transparent droplets. This constraint docs not impact the application to measurements of small water droplet aerosol
flows. The advantages of the PD method are:
1. PD measures individual droplet size and velocity in a small volume (about 10"*5 cm1).
2. PD measures both velocities and sizes on an absolute basis and hence can be used to calculate particle
densities, flow rates, etc.
3. PD data analyses are relatively straight forward, particularly relative to LIV analyses.
While the weaknesses to the PD method are:
1. PD can be applied only to optically transparent droplets.
2. Relatively high powered lasers are required (4 to 10 watts continuous wave).
3. PD measurements are restricted to nearby, small sample volumes and also require high particle
densities for rapid analyses.
Since this project was originally targeted to look at either water mists or particulate aerosols, PD's inability
to work with other than transparent droplets eliminated it as a viable measurement system for this project. The LIV
system was too complicated to set up and operate within the constraints of this program, as a result of the following:
(a) complexities with regard to measuring single particles that pass through quite small volumes defined by the
focused intersection of two equal intensity laser beams; (b) problems attendant with accurately defining focal
volumes associated with long focal length lenses; and (c) the practical limitation on the separation from the final
focusing lens to the sampling volume, coupled with the time needed to accumulate statistically large numbers of
individual particle measurements so as to analyze the mathematical relationships required tu define both particle size
and particle velocity.
The FD measurement system based on development of a detector system utilizing a CCD camera chip and
off-the-shelf optical hardware would yield a low cost but effective alternative to a Malvern System. The former
system would yield measurements of particle size and size distributions, but would not be able to measure particle
velocity. If the water mists or particulate aerosols are generated and dumped into a large stilling chamber to reduce
particle momentum and conveyed from the chamber by an exhaust fan on the exit from the ATC system, then the
average velocity of the particle/droplet aerosol could be measured, controlled, and varied. For these reasons, design
and construction of an FD-based system for measuring particle/droplet aerosols was chosen in order to study the
aerosol properties important to fire extinguishment.
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DEVELOPMENT OF THE FRAUNHOFER DIFFRACTION INSTRUMENT
OVERVIEW
This part of the report details the design, development, setup, and operation of the FD instrument. At
present there are no laser-based instruments that allow multi-station analysis of the interaction of aerosol clouds.
The development the FD instrument, with its ability to characterize aerosol clouds before and after interaction with a
fire, was originally to be the centerpiece of the laboratory-scale experimental program.
FRAUNHOFER SCATTERING THEORY AND CALCULATIONS
The measurement of droplet diameters is based on the Fraunhofcr small angle forward diffraction method.
This method analyzes the small angle forward scattering of light by an ensemble of small particles contained in the
volume of an aerosol defined by a parallel beam of optical radiation. All particles present in the defined volume
contribute to the scattering of the radiation; consequently, the particle size distribution is measured while absolute
number density cannot be determined.
In such measurements the light is scattered by an ensemble of particles into an annulus as shown in
Figure A-8.
12
Figure A-8. Light scattering geometry.
For this configuration the light energy falling into the annulus LS1,S?., is given by
m _ i
Ls,s, = C,£n, r^[{j5h) + Jrfc)}si-{j§(^)+J?(^)L]
,=i
(A-l)
139
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Where
2 K o
-Vl.2 = —TiSl.2
.M
(A-2)
C is a constant factor that includes the light intensity, m is the number of annuluses or bins used in the detector, Nj is
the number density of particles of radius rj, rj is the particle radius, Jn and J, are Bessel functions of the zeroth and
first order respectively, and S is the distance in the detector plane from the unscattered radiation focal position to the
detector clement being considered (either at Si or at S2). Additionally, f is the focal length of the lens that focuses
the radiation onto the detector and X is the wavelength of the incident radiation.
If the ensemble consists of only a single particle size of radius r, then the scattering consists of a peak
centered on a single annulus where the panicle radius and the annulus radii are related by
2 K
jr., = 1.375 = —rSi,2 ,A ~
(A-3)
This relationship then is employed to select the values of rj for various values of Sj^. A program was
written in Borland C/C Version 3.0™ to evaluate Equation A-2 directly, but is not presented here. The program
was directed to permit the determination of a set of particle densities, N,, which would permit the theoretically
determined data set to be brought into agreement with the experimentally determined data set.
To this end, a theoretical data file was calculated directly from Equation A-2 using the condition that Nj in
Liquation A-2 was held constant and that the values of X and f were those of the experimental setup. The
incremental steps utilized for summation of the detector elements was determined experimentally to be 0.0122 mm.
Thus Equation A-5 becomes:
(1.375)(0.0006328)(100)
(2)(3.14159X0.01 22)(i - 1) (A~4)
The Bcsscl functions J;(x) and Ju(x) were evaluated from their power series expansions and their calculation
yielded a value the same as that given in the Bessel function tables within 0.02 percent for all values of x (A-16 ).
The results of these calculations were then written to "Theory.xxx" files with the "xxx" designator indicating which
set of detector element groupings was employed.
Equation A-4 was used to select groupings or bins of particle radii that were used to provide a manageable
number of data points for display ( manageable when compared to the 1600 detector elements and the consequent
140
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1600 different particle radii). Il should be noted (hat the particle radii only changed from 1.01 fim to 0.62 j.im when
the detector element was changed from 800 to 1480.
The binning methods selected were designated as NMERT bins containing 36 groupings and Malvern bins
containing 31 groupings, which were selected so as to replicate the Malvern data set as closely as could be
determined. Usually the data sets were compressed by adding the contents of two adjacent detector elements, and
thus the resultant experimental data sets consisted of files containing 800 points. The files were normalized so that
the sum of all data elements added to 100.00. The resultant "Theory.xxx" files were then designated as
"Theory.800" (no binning), 'Theory.mal," and "Theory.nmi," respectively.
The experimental data sets were collected as two-dimensional "xxxx.bmp" files (400 by 1600) and then
reduced to a 1 by 8(X) file by averaging the successive line scans, detector element by detector element.
Two scans were made for each experimental determination: (a) a background scan taken with no aerosol
particles present and (b) a data scan made with the aerosol present in the beam.
In another Borland C/C1^™ program, the data and background scans were subtracted from each other
(element by element), the resultant file was smoothed by employing a 10-point exponential smoothing function, and
the resultant file was binned appropriately for comparison with the selected "Theory.xxx" file. Then the resultant
file was normalized to the total value of 100.00 as was done for the "Theory.xxx" file.
Finally, a least squares routine was employed, with the fitting variable being the particle number density, N,.
The value of N, was changed for each of the bins so as to force the theoretical curve to assume the same shape as the
experimental data file. The resultant distribution of N, as a function of r„ the panicle radius, was then written to a
final data file for processing in Microsoft F.xeel™ or some other spreadsheet program.
The calculations for the various diameter means are based on the following standard definitions:
m
m
Length-based diameter
(A-5)
i = l
i = 1
Volume-based diameter
(A-6)
m
D 3 7
i= I
Sauter Mean Diameter (SMD)
m
(A-7)
i=i
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[ 12
Surface area-based diameter D :>.o - IV jVj ; D ~ / ^ N , I (A-8)
/ m V
(Z N 'D >' Z N j
The definition-based equations were directly programmed and are calculated from the number density particle
distributions versus particle size.
OVERALL DETECTOR SYSTEM DESIGN
A line scan CCD detector suitable for use in ensemble distribution analysis systems and similar to those
marketed by Malvern, Inc., has been developed. The detector was adapted from commercially available hand
scanner technology. The particular hand scanner employed for this adaptation is the Easy Options 256-Shade
Grayscale hand scanner marketed by IBM, although other companies offer suitable products.
The scanner has 1664 CCD elements in a linear array, and the array is scanned in 3.2 ms. The length of the
active portion of the array is about 18 mm. Each element is effectively about 11 lim or 0.011 mm. When operated at
1/2 resolution, the 832 elements are spread across the array by averaging the pixels in pairs. Thus the effective
detector element dimension is about 22 (.im or 0.022 mm.
The original device operates as a scanner by employing a rubber roller that generates strobing pulses as it is
dragged over a surface. The pulses command the device to read out the data that have been accumulated. A total
time of 3.2 ms is employed to accumulate the next data set, which is left in storage until the next readout strobe pulse
is acquired. The pulses are generated by interrupting a light emitting diode-photo diode (LED-PD) pair with a
slotted wheel geared to the roller.
In this mode of operation, the exposure time for the data storage in the array is constant and independent of
the rate at which the strobe pulses arrive. The data set (the image) has good fidelity from line scan to line scan, and
the maximum rate at which the image can be formed is 3.2 ms per line, although much longer acquisition times can
be tolerated, at least up to times on the order of 50 ms per line.
DETECTOR MODIFICATIONS OF THE SCANNER DEVICE
The. major modification of the scanner was to replace the roller-generated strobe pulses with a pulse train
derived from an oscillator. To this end, the LED-PD unit is directly driven by a small square wave oscillator whose
frequency can be var ied from 12.8 Hz to 294 Hz by the adjustment of a potentiometer. The upper frequency limit
was chosen to give a period of 3.4 ms, which is slightly longer than the minimum scan time of 3.2 ms. Additionally,
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the scan button on the scanner head was bypassed in such a way that by giving the scan command to the host
computer a separate momentary switch initiates the scanning or strobing for the detector array.
The circuit employed is given in the following diagram (Figure A-9) together with the appropriate
connections to the scanner head circuit board.
The detector was substituted for the photo diode detector unit in a Malvern Model 70 particle size analyzer
and the results compared with those obtained by the original Malvern detector system. The data recorded by using
the new CCD scanner detector were close to the data acquired on the Malvern instrument when the linear pixel
elements of the CCD array were grouped in a manner so as to closely approximate the. nonlinear detector element
radii of the Malvern system. The major difference between the two sets of data was the existence of the sharp
diffraction-like spike structures that show up in the CCD array data.
There are two possible approaches to accommodating this problem: (a) Utilize the software to manipulate
the background subtraction so that the sharp peaks are deleted from the final data. Tnis is best done by employing an
exponential smoothing function on the data, which has very little, if any, effect on the overall data shape but does
very effectively remove very rapid cell to cell structure, (b) Track down the source of the unwanted peak structures
and eliminate them. There are currently two likely candidates for producing the diffraction-like structures.
1. Since the detector sits at the Fourier transform plane, this type of diffraction-like structure could be
formed by the existence of a hard beam stop in the optical system. Thus the alignment and setup of
the laser spatial filter should be checked as well as all details of the input optical system to identify
any possible hard beam aperture stop. If located these stops must be removed. A stop was identified
+ 12
1KO
6.8KO
150K12
555
0.33jiT 0.022mJ
0.1 jx/ |
470KQi
A/U
Ai'
X Cut trace
\t
Added I Existing
Circuit | Circuit
'Slotted
Wheel
Removed
Figure A-9. Wiring diagram for conversion of scanner to detector.
143
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in the Malvern instrument and removed. This removal had no effect on the observed diffraction-like
patterns so that it appears that this approach is fruitless.
2. The CCD detector array has a cover glass over the active area. Since the system utilizes coherent
(laser) radiation, the possibility that multiple pass interference effects in the cover glass are
contributing to the observed "diffraction-like" effects can not be. disregarded. The cover glass was
removed from the linear array as an experiment to determine whether the device would function
satisfactorily without such protection. Unfortunately, the device functioned only for a few minutes
before becoming unusable. This approach thus does not seem to be a realistic alternative.
The most effective method for removing this spiking proved to be one of taking a moving average of data
points along the array itself. A standard 10-point exponential moving average proved to be a very effective method
of smoothing the array data without modifying the array data sufficiently to have any measurable effect on the
particle size resolution. Thus, this is used as the standard method of treating the data and has been incorporated as
the standard smoothing function of the program "Reduce." A software option switch has been placed in the program,
which permits this smoothing function to be turned off at the decision of the user for a means of looking directly at
the unsmoothed data.
LASER, SPATIAL FILTER AND COLLIMAT1NG LENS SETUP
Overview
The laser currently being employed is a Uniphase Model 1011 of 4 mW power. The laser beam is first
expanded by a I Ox beam expanding telescope to a diameter of approximately 10 mm. This beam is then incident
onto a Newport Corporation Model 900 spatial filter, which employs a lOx microscope objective as the focusing
element and then is focused through a 25-|J.m diameter pinhole. Subsequently, the output beam from the spatial filter
is collimated by either a 50-mm or a 30-mm focal length (FL) lens. This filtered and collimated output beam is
employed for the Eraunhofer diffraction measurements of aerosol particle size distributions.
Assembly and Alignment Details
Laser and Telescope Assembly-
Thc laser and expanding telescope are assembled as a single unit by employing the set screws in the ocular
end of the telescope to mount the expanding telescope to the output end of the round laser head. Care was taken to
ensure that the output beam is centered on the telescope objective, which is done by adjusting the three mounting
screws (Figure A-10).
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Ac.:jstment: Allen Set Screws
Figure A-10. Adjustments for laser and expanding telescope.
Spatial Filter Assembly-
The spatial filter assembly is positioned on the optical rail at any selected position in front of the expanding
telescope. It is necessary to ensure that the input beam to the spatial filter focusing lens (the lOx microscope
objective) is centered on the input aperture of the objective. The x-y-z micrometer adjustments are used to maneuver
the pinhole into the exact focal position of the spatial filler focusing objective. (The pinhole is held in position on
the faces of the x-y micrometer by a magnetic chuck and it is necessary to be sure that the positioning of the pinhole
onto the ends of the adjustment faces is square and secure.)
In a dimly lit room, the pinhole is visually aligned as well as possible and then the z drive is adjusted (the
focus adjustment) until some laser light can be observed passing through the pinhole. The direction of motion of the
transmitted laser spot when the x or the y adjustment is changed is noted. If the spot moves in the same direction as
the adjustment, i.e., if the spot moves left when the pinhole is moved left, then the pinhole is located beyond the
focus of the objective lens. If the spot's motion is opposite to that of the pinhole motion, then the pinhole is located
before the focus of the objective lens. The pinhole is carefully moved along the z-axis toward the lens focus, making
x and y adjustments on the pinhole position as necessary to maintain laser light transmission through the pinhole.
When the pinhole has been maneuvered very close to die focal point of the objective lens, the intensity of
transmitted light will increase markedly, as will the size of the spot, and the apparent motion of the transmitted spot
will decrease sharply as either x or y adjustments are made to the pinhole lateral position and the sensitivity to small
/-direction (lateral) adjustments will increase greatly. At this point the transmitted intensity becomes of nearly
uniform intensity across the area of the transmitted spot, and the spot simply "winks" out without any apparent
translational movement when x or y adjustments are made. This condition constitutes proper positioning of the.
spatial light filter.
-------
Collimating Lens—
The collimating lens, mounted directly in front of the spatial filter, is positioned so that it is approximately
one lens focal length (FL) away from the pinhole, i.e., about 30 mm or 50 mm depending on which focusing lens is
selected. The 30-mm FL lens will produce a smaller laser beam cross section for measurements than will the 50-mm
FL lens.
The alignment and adjustment of the collimating lens is carried out by first ensuring that the incident
radiation is centered in the x - y plane of the lens. Adjustments can be made with lateral movements of the lens. The
adjustment of the 7. or axial position of the lens relative to the spatial filter is then made so that the laser spot
diameter remains constant from the position immediately following the lens to the final beam splitter position. This
is readily done by using a white card lo mark the beam diameter at both positions and then adjusting the lens axial
position to make the two diameters equal.
MULTIPLE MEASUREMENT STATION CONFIGURATION
The CCD detector elements employed with the NMERI detection system have adequate signal-to-noise
ratios such that only a small portion of the 4-mW laser beam need be employed for measurements. Thus, multiple
measurement stations can be set up by splitting off minor portions of the beam and passing each portion through a
part of the aerosol stream at various locations for measurements. In the setup employed for the ATC, 80/20. 70/30,
and 60/40 beam splitters (HO percent transmission / 20 percent reflection, etc.) are used so that 20. 30, or 40 percent
of the beam is successively directed through the aerosol sampling volume for successive station positions. When the
vertically positioned stations are to be employed, a beam splitter (20/80) and mirror are employed to direct the beam
to those stations.
INITIAL SETUP AND ALIGNMENT
The initial setup of a newly fabricated detector device requires setting the proper position for the focusing
lens in the barrel mount, establishing the position of the beam stop shield, and installing the edge stop. These steps
need be performed only once for each new detector device.
StcpJ_
Using the retaining rings, the focusing lens is positioned initially in the barrel mount at about two-thirds of
the way along the interior threads toward the detector end. The barrel is then placed in the collimated laser beam,
and the location of the focal spot is determined by its display on a semitransparent paper card, which is spaced by a
microscope slide away from the end of the barrel, i.e., the plane of the barrel rim which contains the two threaded
116
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mounting holes. The microscope slide accounts for the thickness of the cover glass on the CCD detector. The laser
beam is attenuated, if necessary, to obtain a clear view of the focused spot. The location of the focusing lens is
moved, as necessary, in order to position the focused spot 1 mm away from the plane of the barrel rear
(Figure A-l 1). A IleNe line filter is then positioned over the outside retaining ring in the barrel, and a rubber o-ring
is inserted and clamped into position by using a third retaining ring.
Focal Spot
n
7
/
Collimated Beam
/'
Retaining Ring
Lens
Figure A-11. Cross section of barrel mount showing location of focal spot.
Step 2
The detector array, without the barrel-mounted lens and filter, is then connected to the computer board and
allowed to scan while exposed to dim room light. Using an opaque card that is slowly moved across the array from
one end, the direction of scanning is established as well as the position of addresses near 100 to 200 (out of 1600).
An aluminum foil mask is temporarily secured across the array such that the low address elements are
obscured and the edge falls between address 100 to 200. The scanner is activated and the dark-to-light transition
position is observed. The position of the edge stop is adjusted until the lower 100 to 160 array elements are blocked
out as illustrated by the position of the dark-to-light edge position in the scanned image. The aluminum foil mask is
then secured.
The scanner/detector element has a glass cover that shields the array from unwanted and/or deleterious
atmospheric effects. While this docs in fact protect the array from potential problems, it also introduces some
problems associated with its employment as a detector array for its intended applications. Figure A-12 is a top view
of the detector array, its scale greatly enhanced, which illustrates the problem associated with employment of such a
device in the application as a detector for Fraunhofer diffraction ensemble studies.
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Si-CCD Array
Beam Width at
"Edge Stop" Location
Cover Glass
Incident Unscattered Laser Beam
Figure A-12. Detector detail, including cover glass.
The cone of radiation from the scattering region is focused (in this case) by a 100-mm FL lens. The
colli mated laser beam is about 20 mm in diameter. Thus, the peripheral optical rays have an angle of about
5.7 degrees relative to the normal. By using nominal dimensions of 1 mm for the cover glass thickness and 0.5 mm
separation from the active array elements, the incident cone is about 250 |im wide at the position where the metallic
edge stop is ( and can be) placed. This translates to a penumbra type of cutoff of the central beam of about four
detector elements (1/2 of the beam diameter at the beam-stop position times 22 |im per detector element). The data
were, therefore, corrected by setting all data points on the small detector element side of the first major maximum of
the background run equal to zero. This procedure ensured that data derived from such questionable regions of the
runs were excluded from consideration. This procedure had the effect of limiting the dynamic range of the
measurements, reducing the theoretical range from about 200:1 to a value nearer to 100:1.
At this point the detector is scanned while still exposed to dim room light, and the resultant image is saved
for the purpose of establishing the precise position of the edge stop. The resultant file is processed through
"Average4" software program and displayed as a plot by using Excel. The approximate position of the light-to-dark
transition is noted, and the data file is explored in that region.
The barrel-mounted lens and HeNe line filter assembly is then attached to the detector array face plate by
two 4-40 screws into the rim face of the barrel. The barrel is offset from the center axis of die array so that the edge
stop is approximately aligned with the barrel center axis. (For detectors previously employed or set up, the linear
Step 3
148
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variable filter must be removed from its position in front of the scanner array. Then the 25.4-rrim diameter viewing
port on the top rear of the detector lens-filter barrel is uncovered by removing the aluminum foil tape cover.)
Step 4
At this point the detector device is secured into its measurement position.
Sicp 5
The beam-splitter/diagonal mirror rail mount is then slid into a position where the diverted beam is
approximately centered on the detector barrel filter. The position of the unattenuated and focused laser beam onto
the detector array should also be observed.
The position of the rail mount and the angular adjustment of the diagonal mirror are changed so that the
focused laser beam is positioned within 0.5 mm of the array end of the edge stop, in the barrel-mounted lens, on the
aluminum foil mask. The retroreflected beam (the reflection of the incident laser beam from the front surface of the
line filter mounted in the detector barrel) must be returned as nearly as possible onto the diagonal mirror. Some
small overfill or misalignment of the retroreflected beam is allowable.
Step 6
The rail slide is then locked into position and the diagonal mirror adjustment screws arc tightened.
FINAL DETECTOR SETUP AND ALIGNMENT
Tlie linear variable density filter is inserted into its receptacle immediately in front of the detector array with
the high attenuation edge toward the edge stop. The filter is held against the lens-filter barrel with strips of high-
density foam rubber. The filter is secured in position with black electrical tape making sure the open ends of the
slotted receptacle and the filter are obscured.
The viewing port is covered with aluminum foil tape. (Black tape is sufficiently transparent to light that the
detector will show some residual background signal.)
A neutral density 1.0 attenuator is then placed over the laser output and the detector is scanned. The scan
rate may be slowed down considerably for this step by adjusting the rate potentiometer. The level potentiometer
should be set approximately to the center of its range.
149
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The scanned image is then observed. The position of the deteetor rail slide and the angular adjustment of
the diagonal mirror should be adjusted so that an overexposed white stripe is observed at the beam stop edge. This
white stripe represents overexposure of the CCD caused by the edge of the focused laser beam.
The detector adjustment screws are employed to shift the detector position in the direction perpendicular to
the array orientation. The overexposed white stripe grows or diminishes in extent along the array orientation as
adjustments are made until the stripe dimension is maximized. At this point the incident focused laser beam is
located along the axis of the CCD array.
Next, small adjustments are made in the detector position along the CCD array axis. Adjustments in the
direction that begins to narrow the overexposed white stripe should be made. The adjustment is continued to the
point where the sharp white line narrows down and just disappears. At this point the focused laser beam is properly
aligned for taking data.
During data processing by "Reduce," the focused laser beam position should be entered as the "edge"
address position minus half of the focused beam width for the neutral density filter presently in use, counted in
detector elements.
SOFTWARE DEVELOPMENT
All software programs are written in Borland C/C++ Version 3.0. Three programs are employed to provide
flexibility in the successive manipulations of the data.
1. "Average4" takes the data as generated by the hand scanner software which is usually a 1600 by 400
clement bitmap file and provides a 400-element average of each of the 1600-detector element outputs.
2. "Reduce" permits the subtraction of two such averaged data sets (the data and the background),
permits a 10-point exponential average of the data for smoothing purposes, and permits the data to be
"binned" or grouped together for purposes of making convenient graphical presentations of the
information.
3. "Leastsq" provides a fit of the experimental data from "Reduce" to the theoretical data points
previously calculated from Fraunhofer diffraction theory. These theoretical points are generated by a
program named "FileJJOl," so named because of its extensive calculations of the two Bessel functions
Jo and J i.
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DATA TAKING PROCEDURES
Acquiring data and analyzing it to generate the final histograms and drop size medians will depend upon the
equipment available. This section describes what is done on the ATC instrument system to generate the data for
presentation of the final results. The intention is to document the steps taken to obtain the results, for use in
understanding how the data are obtained and for determining the reproducibility of the instrument.
The Fraunhofer instrument computers are minimally 486DX-25MHz-based systems; 386-based systems are
too slow to process the data in a timely fashion. The main Fraunhofer instrument computer is set up to operate as the
server for the other aerosol test chamber computers. After booting up, the Proimage program is opened on this
computer. Proimage Version 1.10™, a scanning program developed by Prolab Tech Company, came with the IBM
Easy Options01 handscanners. If other scanners are obtained, the scanning program may need to be different.
After the Fraunhofer instrument computer has booted up, the additional Fraunhofer instrument computer
(optional) and the data acquisition computer system are booted up. The data acquisition computer was programmed
with a continuously monitoring multistation temperature and relative humidity program. The data acquisition
computer screen offered the following options: (a) to freeze the screen; (b) to start accumulating data, whereupon
the program records a data file every 0.66 sec: (c) to place a marker in the data file when a Fraunhofer scan has been
taken; and (d) to stop taking data.
Upon releasing the lockout for the high pressure, variable speed/signal water pump and the ATC exhaust
fan. the breakers are turned on and the exhaust hood fan is started. If the ATC has not been operated for awhile, the
water reservoir will need to be filled to 15 cm below the top of the grating to maintain a constant system volume and
sufficient water reserves. Additionally, the in-line filters must be removed, back flushed with water, and replaced
before the ATC is operational.
When the Fraunhofer instrument computer is on-line, both the detector hardware and the software must be
set up for scanning water mists. The detector head itself was delivered with the scanning switch set to the 400 dots
per inch setting (dpi), which is recommended for operation as a Fraunhofer detector device. The Proimage software
(under Windows) is opened, and the settings for image type, resolution, and image size set to Index 256 Gray,
400 dpi. and custom image size of 10.2 cm wide by 2.5 cm long, respectively.
At this point, the Fraunhofer instrument computer is now capable of scanning water mists when the
appropriate detector from the switch box is selected. The scan mode is activated when the image box button "Scan"
is selected, under file:acquire, and the detector activation switch is depressed. For data reduction, background
scans—without the presence of the aerosol—are run and saved, for the appropriate detectors (Positions 2 through 7
in Figure A-13). Then data scans, runs in the presence of the aerosol, are obtained following the same procedure.
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When satisfactory scans have been acquired, llie scanned image is converted into a "xxx.bmp" file and saved under
an appropriate file name. For proper analysis of aerosols, both runs must be acquired.
The procedure for setting-up a test run follows: (a) With the vertical deflector plates in place and the
horizontal deflector plate in the open position, the test zone window is opened and 10 niL of fuel are pipetted onto
the water in the 5-cm cup burner located in the horizontal test zone; (b) upon removing the pipette, the fuel is ignited
and the window closed: (c) using the controller for the 0.0003 m3/s high pressure, variable speed water pump, the
pump is started and set to the flow desired; (d) the toggle and rheostat switches controlling the aerosol test chamber
fans are turned on and set; and (e) when all the desired test conditions are set, their operating parameters are
recorded.
After the air flow and water pressure/flow have stabilized, the first detector in the horizontal duct
(Figure A-13 and Table A-l) is scanned and saved thereby obtaining a measurement of the water mist as it enters the
duct. The vertical deflector plates are then removed and the horizontal deflector plate is closed. This allows the
water mist to flow into the test zone where water mist data scans for the appropriate detectors can be obtained, for
example, for Positions 3 and 4, which are before and after the first cup-burner position in the horizontal duct.
Adjustment to the air or water flow depending on the test parameters can be made while scanning and saving
Positions 3 and 4 or until the cup burner is extinguished and the desired data collected.
V1 Cffit)
6 --
S6.ll
;S™ii I p?
, —-7.^ . r A* , . --r-
Oi
j;
R.
/
/
7 iTn r
' u;u /
3 2 M
Front View
1
Airflow
L;
(i=.
' 'I
V •'
(o
I l
M
Left Side View
Figure A-13. Detector positions in the aerosol test chamber.
152
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TABLE A-1. POSITION/EQUIPMENT MATRIX FOR MEASUREMENTS
— —. ————II ¦ ¦ - . .1^—¦¦ ¦ | |
Position in Temperature Relative Humidity Fraunhofer Gravimetric
Figure A-13 detector concentration
1 X X
2 X XX
3 X X X X
4 X X X X
5 X X X X
6 X X X X
7 X X X X
After the desired scans have been taken during the course of the test series, gravimetric water mist
concentration samples are taken from the appropriate test positions, just above and in front of the respective
detectors.
At the end of a test series, the relative humidity and temperature recordings are terminated, and a
gravimetric water mist concentration sample is obtained from Position 2, just above and in front of the first, detector.
Operation of the aerosol test chamber intake and exhaust fans is continued until the system is dry and all the
combustion products and residual fuel vapors are exhausted from the aerosol test chamber.
To complete She data collection, the relative humidity and temperature data files are moved from the data
acquisition computer to the primary (or server) Fraunhofer instrument PC as a data file for incorporation into the
final spreadsheet. The Fraunhofer instrument's PC scanning program is then closed, and the data reduction program
to calculate the required parameters is opened.
DATA ANALYSIS
This section describes what is done with the results obtained from the ATC instrument system. The
intention is to document the steps taken to generate the final histograms and drop size medians for presentation based
upon the results obtained from the ATC. This section is included to help document the steps taken to obtain the final
results and for use in understanding how the data are generated and for determining the data quality indicators
(DQIs).
For ease of operation, the. computer should have a program item icon set up, titled "Data Reduction," which
analyzes the data since the Borland C/CM™ programs run under DOS. This will permit quick access to the
Proimage™, data reduction, and Excel 5.0™ programs without the need to exit Windows™. A director)' and/or
153
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subdirectory must be employed that contains both the recorded "xxx.bmp" data files and the Borland CYC1-"™
programs for the data analysis. The recorded xxx.bmp files are usually 1600 columns by 400 rows in size. The
program "Average4" is employed to provide a 1600 column by 1 row file which is made up of a 400-element
average of each of the columns.
The data reduction program is opened to load and activate the "Average4" program, which asks for the
following menu items:
1. Input the recorded experimental file name as "xxx.BMP."
2. Input the output file name as desired, (usually xxx.AVG).
3. Input the column number to start average, usually 0.
4. Input the column number to end average, usually 1599.
The program will then write the processed 1600 by 1 data file to the disk in ASCII format. NOTE: The column
selection availability displayed by the program in the final two steps is derived from the input data and represents the
actual format of the xxx.BMP file being processed.
Assuming that both a background and a data file have been processed through "Average4," the files are then
further processed through "Reduce." The function of "Reduce" is to reduce the data to a format satisfactory for
performing a theoretical analysis. The program provides the following functions:
1. Subtracts the background from data files column by column if so desired.
2. Employs a 10-point exponential smoothing factor to the resultant data file if so desired. This function
smoothes the data while having only a minimal effect on data shape.
3. Groups the data into selected particle size bins as desired. Three options are selectable: No Binnina.
which employs the full resolution of the detector device and the resultant analysis emphasizes small
particle radii; NMF.RI Bins, which provides grouping of particles with radii ± 0.5 Jim. except for large
particles that arc grouped according to single detector elements; and Malvern Bins, which simulates
the detector groupings of the Malvern particle sizing apparatus.
For the "Reduce" program:
1. Follow the menu items provided.
2. Input the position of the focused laser beam as selected according to the information obtained in the
FINAL DETECTOR SETUP AND ALIGNMENT section.
3. Input the experimental data file name (usually xxx.AVG). If the file does not exist, the program
terminates with that error message.
154
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4. Input the background data file name (usually xxx.AVG). A similar error message occurs if this file
does not exist.
5. The output file name is selected, (usually xxx.OUT).
6. The processed data file is written in ASCII format to hard disk.
The file that is outputted from "Reduce" is then fitted to the appropriate theoretical functions by using
"Leastsq." This program calculates the particle size distribution, the volume/mass weighted particle size distribution,
the cumulative volume/mass weighted particle size distribution, and the droplet surface area weighted size
distribution. It also calculates arithmetical mean particle size, volume/mass weighted mean particle size, and Sauter
mean particle size. All sizes are given as diameters in micrometers.
For the "Leastsq" subprogram:
1. Enter the theoretical filename:
A. Theorv.800 for no binning.
B. Theory.nmi for NMERI binning.
C. Theory.mal for Malvern binning.
2. Enter the experimental filename, output from "Reduce," (usually xxx.OUT).
3. Enter the output data filename (recommended xxx.FIT).
The output file, written in ASCII format to hard disk, will carry the column headers given below—
LENGTH N_MHD. DIAJVIED. VOL_Ml2D. SAUTER
followed by the file size and various particle sizes in appropriate columns.
Under these columns will be another set of column headers:
BIN DIA. NMBR. VOL_DIA. SUM_V. SURI;_D.
The resultant file dimension will be 6 columns by (file size) rows with the designated data provided in each column.
The file that is outputted from "I.eastsc]" as a xxx.FIT file can then be processed with any
spreadsheet/graphing program to display the above results in table and histogram form for each data set. The
original program used was Microsoft Excel Version 4.0 although other products can be utilized.
155
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REFERENCES
A-l. Rader, D. J., and O'Hearn, T. J., "Optical Direct-Reading Techniques: In Situ Sensing, Aerosol
Measurement, Principles, Techniques, and Applications, Van Nostrand Reinhold, New York, New York,
pp. 345-380, 1993.
A-2. Weiner, Bruce B„ "Particle and Droplet Sizing Using Frauenhofer Diffraction," Modern Methods of
Particle Size Analysis, John Wiley and Sons, Inc., New York, New York, pp. 135-172, 1984.
A-3. Dodge, L. G., "Calibration of the Malvern Particle Si/.er," Applied Optics, Vol. 23, pp. 2415-2429, 1984.
A-4. Lefebvre, A., Atomization and Sprays, Hemisphere Publishing Corporation. New York, New York, 1989.
A-5. Masters. K., Spray Drying Handbook, John Wiley and Sons, Inc., New York, New York, 1985.
A-6. Farmer, W. M., "Measurements of Particle Size, Number Density, and Velocity Using a Laser
Interferometer," Applied Optics, Vol. 11, pp. 2603-2612, 1972.
A-7. Gr6han. G. and Gouesbet, Ci., "Simultaneous Measurements of Velocities and Sizes of Particles in Flows
Using a Combined System Incorporating a Top-Hat Beam Technique," Applied Optics, Vol. 25, pp. 3527-
3538, 1986.
A-8. Maerla, M., and Hishida, K., "Application of Top-Hat Laser Beam to Particle Sizing in LDV System,"
Modern Methods of Particle Size Analysis, John Wiley and Sons, Inc., New York, New York, pp. 431 -441,
1984.
A-9. Hess, C. G., and Li, F., "An Instrument to Measure the Size, Velocity, and Concentration of Particles in a
Flow," Modern Methods of Particle Size Analysis, John Wiley and Sons, Inc., New York, New York,
pp. 271-282, 1984.
A-10. Bachalo, W. D„ "Method for Measuring the Size and Velocity of Spheres by Dual-Beam Light-Scatter
Inteiferometry," Applied Optics, Vol. 19, pp. 363-370, 1980.
A-l 1. Bachalo, W. D., and Houser, M. J., "Phase/Doppler Spray Analyzer for Simultaneous Measurements of
Drop Size and Velocity Distributions," Optical Engineering, Vol. 23. No. 5, pp. 583-590, 1984.
A-12. Bachalo, W. D., "The Phase Doppler Method: Analysis and Application," Particle and Particle System
Characterization, Vol. 11, No. 1, pp. 283-299, 1994.
A-13. Sankar, S. V., and Bachalo, W. D„ "Response Characteristics of the Phase Doppler Particle Analyzer for
Sizing Spherical Particles Larger Than the Light Wavelength," Applied Optics, Vol. 30, No. 12, pp. 1487-
1496, 1991.
A-14. Al-Chalabi, S. A. M., Hardalupas, Y., Jones, A. R., and Taylor, A. M. K. P., "Calculation of Calibration
Curves for the Phase Doppler Technique: Comparison Between Mie Theory and Geometrical Optics,"
Optical Particle Sizing, Theory and Practice, G. Gouesbet and G. Grehan. Plenum Press, New York, New
York, pp. 107-120. 1988.
A-15. Jackson, T. A., and Samuelsen, G. S., "Performance Comparison of Two Interferometric Droplet Sizing
Techniques," Society of Photo-Optical Instrumentation Engineers, Vol. 573, pp. 73-79, 1985.
A-16. Weast, R. C., Handbook of Chemistry and Physics, The Chemical Rubber Co., Cleveland, Ohio, 1971.
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APPENDIX B
FRAUNHOFER VERSUS MALVERN SERIES 2600 PARTICLE SIZE COMPARISON
As part of the development of the ATC, a Fraunhofer (small angle forward) diffraction instrument for
measuring water mist droplet size and size distribution was proposed for development with this project.
Improvements in detector technologies and increased personal computer capabilities have come on the market since
Malvern Instruments Ltd. brought out their line of particle analyzers, thereby allowing the development of a
versatile, low cost Fraunhofer diffraction-based particle analyzer utilizing off-the-shelf components. The off-the-
shelf components required for this system were a 4-mW helium-neon (HeNe) laser, beam expander, spatial filter,
collimating lens, focusing lens, HeNe line filter, neutral density filter, and a linear variable density filter. The only
speciality item used to develop this system was an over-the-counter hand scanner, which was converted to a CCD
detector, as described in Appendix A. The small, lightweight detector system allows aerosol measurements to be
taken in small quarters, where other instruments would not fit (Figure A-l in Appendix A).
A joint effort with Sandia National Laboratories (SNL) was proposed for validating the new Fraunhofer
instrument against a Malvern 2600 Particle Sizer. Since the DQI goals were to ensure that all data collection or
measurement activities yield data of known and adequate quality sufficient for the intended use, one of the most
effective ways to accomplish this is a side-by-side comparison with an instrument already accepted in the field for
this application.
Figures B-l through B-8 show the Malvern data taken at Position 5 for the calibration reticle, an air-
atomized nebulizer, and for various water mist and air flows in the horizontal fire test zone of the ATC. Fraunhofer
instrument data were taken at the same time at Positions 3 and 4. Analysis of the Fraunhofer data indicated non-
reproducible results between the positions and within the repeats of the individual detectors.
To investigate the cause for the non-consistent results in extinguishing the heptane cup-burner fires in the
ATC, the Malvern and Franhofer instruments were removed from the ATC. The instruments were set up over a sink,
which would collect the spray from a single nozzle. Figures B-9 through B-20 show the Malvern results for these
tests. With regard to the ATC testing, the data showed that the Baumac MX-8 and MX-20 nozzles produced
essentially the same water mist size distribution and maintained these distributions at two test distances below the
nozzles, 14 cm and 40 cm respectively. The only significant difference between the nozzles was the water flow rates
at equivalent pressures. As discussed in the main body of the report, the significant finding from this testing
regarding the ATC was that only approximately 10 percent of the water mist was turning the corner and entering the
fire test zones. This approximation was based upon comparison of the water mist distribution curves relative to the
157
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10-j.tm droplet diameter percentage in the spray from the nozzle. At this point the ATC was set aside and the
alternative test method was developed.
The Fraunhofer data taken during the single nozzle comparison again indicated non-reproducible results.
Initially, it was believed that an electrical connection was at fault since it shut down the instrument several times
during the test series. Rebuilding the electrical connection and checking the rest of the wiring indicated that some of
the detectors were not sufficiently grounded. The wiring problems were corrected and the Baumac MX-8 and MX-
20 data runs were repeated for the Fraunhofer instrument. Again, the results did not consistently match the Malvern
instrument.
Part of the problem with the Fraunhofer instrument was the determination of the set back of the focal point
from the end stop. One proposal was to fine tune the focus of the Fraunhofer instrument by using the calibration
reticle designed for the Malvern instrument. After mechanically determining the Fraunhofer's focal point to
± 4 pixels, the final focal point would be determined indirectly by adjusting the focal point setting in the computer
computations used to reduce the data. The fine tuning was based on the calibration reticle having spheres fixed in
glass, which give a volume median diameter of 46.5 ± 1.9 p.rn on the Malvern instrument. While this did yield
results that compared favorably to the Malvern data, it was not consistent on a day-to-day basis. It was determined
that direct measurement of the focal point and the set back behind the end stop would be required to make the
instrument work as desired and to enable it to be reproducible on a day-to-day basis. It was at this point that work
stopped on this phase of die project.
Subsequent work by NMERI to bring this technology on-line included redesigning the detector to give
control and adjustment along all three axes (Figure B-21). Adjustment along the three axes will allow the focal point
to be determined and the incident laser beam to be accurately focused on the CCD. Figure B-21 shows a schematic
of the redesigned detector. The significant change was the decoupling of the lens barrel from the CCD detector
housing (the box). The lens barrel was shortened to compensate for the plate holding the CCD and electronics. The
CCD detector was mounted to a plate attached to two translation stages, which allow independent adjustment in the x
and y axes. Focusing the lens on the CCD was accomplished by bonding the lens to an adjustment ring and manually
screwing the lens in and out until the focal point was determined using the full width at half maximum method, which
is the common method used in adjusting optics. Upon focusing the lens, the laser beam was split and a second beam
was brought into the detector at approximately a 10-degree angle. 'Ilie second beam gives a reference point (the
distance or number of pixels between the focal points of the two beams is constant) for determining the set back of
the focal point when the CCD detector is shifted so that the primary beam lands on the end stop. Once the primary
focal position is determined, the secondary beam is blocked and not used during actual testing.
Tables B-1 and B-2 and Figures B-22 and B-23 show the results for three repeat scans on two different
neutral density (ND) filter setups taken over a two-day period for the calibration reticle and for a water mist
158
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nebulizer run on regulated-air from a lank instead of the less uniform house-air used in the Malvern analysis. The
reticle series 1211DT1 to l211DT3and the nebulizer series 1212DT2A to 1212DT2C used an ND filter of 4.0,
while the remaining series used an ND filter of 3.5. The volume median data for the calibration reticle on the
Fraunhofer instrument fall within the accepted range of 46.5 ± 1.9 )im. The percent of relative standard deviation for
the calibration reticle test series ranged from 0 percent for the number and volume medians to 1.70 percent for the
Sauter median and finally 4.12 percent for the Surface area median. All results fall below the expected six percent
relative, standard deviation proposed in the DQI goals.
Further work on the Fraunhofer instrument needs to be carried out to define and optimize the working space
and the parameters to be used under different test conditions.
TABLE B-1. MEDIAN DATA FOR THE CALIBRATION RETICLE ON THE FRAUNHOFER INSTRUMENT
Run number
Number median, (xm
Surface area
median, urn
Volume median, p.m
Sauter median, |itm
1211DT1
45.56
42.08
47.96
45.88
1211DT2
45.56
40.95
47.96
45.40
1211DT3
45.56
41.54
47.96
45.67
1212DT5A
45.56
37.51
47.96
46.53
1212DT5B
45.56
39.37
47.96
47.30
1212DT5C
45.56
40.04
47.96
47.28
TABLE B-2. NEBULIZER MEDIAN DATA FOR ND 4.0 AND ND 3.5 FILTERS
Run number
Number median, p.m
Surface area
median, (am
Volume median, ,um
Sauter median,
1212DT2A
4.56
5.23
8.28
6.52
1212DT2B
4.56
5.26
8.28
6.57
1212DT2C
6.08
5.41
8.28
6.87
1212DT5D
4.56
5.11
8.28
6.42
1212DT5E
4.56
5.19
8.28
6.50
1212DT5F
4.56
5.38
8.28
6.85
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Run 1
Run 2
Run 3
M M
10 100
Droplet Diameter, micrometers
1000
Figure B-1. Calibration reticle on the Malvern instrument.
Run 2
«
E 20
n
O
>
o
H
o
c
-------
0)
E
3
O
>
CO
o
H
c
5
o
c
-------
ffl
E
D
O
>
"5
o
I-
c
®
e
CD
Q.
«— Run 1
Run 2
Run 3
10 100
Droplet Diameter, micrometers
1000
Figure B-5. Malvern analysis - MX-8/20 spray at 6.90 MPa and 7.08 mVmin.
Run 1
Run 2
Run 3
10 100
Droplet Diameter, micrometers
1000
Figure B-6. Malvern analysis - MX-20 spray at 3.45 MPa and 4.53 m /min.
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Run 1
Hit— Run 2
Run 3
1 10 100 1000
Droplet D'ameter, micrometers
Figure B-7. Malvern analysis - MX-20 spray at 6.90 MPa and 4.53 m3/min.
16
~ Run 1
—¦—Run 2
Run 3
14
12
10
8
6
4
2
0
1000
100
10
Droplet Diameter, micrometers
Figure B-8. Malvern analysis - MX-20 spray at 6.90 MPa and 7.08 m3/min.
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35
30
m 25
E
_3
O
> 20
o
I-
c
0
o
CD
a.
15
10
_/\.J V M ft if V/\
f
1
10 100
Droplet Diameter, micrometers
Run 1
B— Run 2
Run 3
1000
Figure B-9. Malvern analysis of MX-8,14 cm below the nozzle at 3.45 MPa and 8.1 x 10"5 m3/min
Run 1
—m— Run 2
Run 3
1000
Droplet Diameter, micrometers
Figure B-10. Malvern analysis of MX-8,14 cm below the nozzle at 6.90 MPa and 1.3 x 104 m3/min.
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10 100
Droplet Diameter, micrometers
Figure B-11. Malvern analysis of MX-8, 40 cm below the nozzle at 3.45 MPa and 8.1 x 10'5 m3/min.
35
30
Run 1 J
25
20
15
10
5
0
1000
100
10
Droplet Diameter, micrometers
Figure B-12. Malvern analysis of MX-8, 40 cm below the nozzle at 6.90 MPa and 1.3 x 10 4 m3/min.
165
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6.90 MPa
25
I
I
>
20
o
c
CL
100
1000
10
1
Droplet D'ameter, micrometers
Figure B-13. Malvern comparison of MX-8,14 cm below the nozzle al 3.45 MPa and 8.1 x 10"5 m3/min
and 6.90 MPa and 1.3 x 10"4 m3/min.
>
1
t-
o
c
6.90 MPa
3.45 MPa
BhM1 II
10 100
Droplet D'ameter, micrometers
1000
Figure B-14. Malvern comparison of MX-8, 40 cm below the nozzle at 3.45 MPa and 8.1 x 10"5 m3/min
and 6.90 MPa and 1.3 x10"4 m3/min.
166
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TECHNICAL REPORT DATA
{Please read Instructions on the reverse before compk
1. REPORT NO. 2.
EPA-600/R-97-006
3
4. TITLE AND SUBTITLE
Development of Alternative, Non-Halon Fire
Protection System
5. REPORT DATE
February 1997
6. PERFORMING ORGANIZATION CODE
7. author(s) r ^ _ Patterson, G. Gobeli, and R. E. Tapscott
(NMERI); and P. J. DiNenno (Hughes)
8. PERFORMING ORGANIZATION REPORT NO.
NMERI 95/11/31840
9. PERFORMING ORGANIZATION NAME AND ADDRESS
The University of New Mexico
Albuquerque, NM 87131
Hughes Associates, Inc.
6770 Oak Hall Lane, Columbia, MD 21045
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D3-0141 (NMERI)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 9/93 - 12/95
14. SPONSORING AGENCY CODE
EPA/600/13
15. supplementary notes ^PPCD project officer is Theodore G. Brna, Mail Drop 4, 919/
541-2683. P
16. abstract^th the phaseout of halon production, two alternative technologies—water
misting and low-residue particulates—have come to the forefront. These technolo-
gies use water or dry chemicals in reduced quantities to provide acceptable fire pro-
tection. A review and assessment of the state-of-the-art for these technologies
were conducted. Consequently, water misting was recommended as the most pro-
mising near-term technology. An experimental program defined and optimized the
operating parameters for a water mist system at laboratory-scale, followed by room-
scale testing. In the laboratory, a water flux of 0.6 L/min-sq m effectively extin-
guished Class A and B (heptane) fires. Below this water flux level, the extinguish-
ment times varied significantly, while water fluxes above this level did not decrease
extinguishment times in comparison to the amount of water used. Room-scale experi-
ments demonstrated that scale-up from the laboratory is straightforward and can
minimize the requirements for room-scale tests. A cost comparison of water mist
systems with respect to the equivalent halon system indicates that water mist is
competitive in many applications. Water misting fire suppression system design and
costs are estimated at $90-$150/cu m across a range of technologies. Halon systems
now average $125/cu m in many applications.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. cosati Field/Group
Pollution
Fire Fighting
W ater
Mist
Tetrafluoroethylene Polymer
Pollution Prevention
Stationary Sources
Halon
13 B
13 L
07B
04B
111
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
?^gO. OP PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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