Fire protection solutions for LNG facilities

FIRE PROTECTION SOLUTIONS
FOR LIQUEFIED NATURAL GAS

TABLE OF CONTENTS
Section Page______ ____
Introduction 1
The Natural Gas Fire Problem 2
The Candidate Fire Extinguishing Agents 5
The ANSUL Natural Gas Fire Extinguishment Concept 6
The Experimental Experience 8
The General Behavior of Extinguishing Agents 9
The Specific Agent Flow Rate Requirements
For Natural Gas Fires 11
The ANSUL Recommended Agent Quantity Requirements 12
Bibliography 26

INTRODUCTION
Page 1
INTRODUCTION
The liquefaction of natural gas, which reduces its volume by a
factor of over 600, has made the storage and transportation of this
fuel economically attractive. However, this liquefaction technique
has also served to increase the amount of energy in storage,
process and transportation equipment by the same amount.
This tremendous concentration of energy has not been overlooked
by the gas utilities, nor gone unnoticed by the authorities and the
general public. The safety of natural gas, especially from the fire
protection standpoint, has been the subject of considerable
research in recent years, and many techniques have been refined
in the overall fire protection approach to the hazard.
As with any other potential hazard, the fire protection for a natural
gas facility consists of three elements: fire prevention, fire control,
and fire extinguishment. Figure 1 illustrates these elements as
they relate to LNG (Liquefied Natural Gas) processes.
The considerations for fire prevention are well documented in the
National Fire Protection Association’s Standard on “Storage and
Handling of Liquefied Natural Gas (LNG),” NFPA 59A1. In addition,
the techniques for fire control, especially for exposure protection,
are not that different with natural gas than with many other flam-
mable materials. There is a great amount of historical experience
in this area. The primary element to which this publication
addresses itself is the extinguishment of fires involving natural
gas, in the liquefied, vapor and gaseous states. A brief description
of vapor dispersion, which can minimize downwind drift of vapor
clouds, and radiation intensity is also made10.
NFPA 59A recommends that “normally gas fires (including LNG)
should not be extinguished until the fuel source can be shut off.”
However, a gas fire which places personnel in severe danger, a
gas shutoff valve which is involved in the fire, or a fire which indi-
rectly endangers personnel through thermal failure of equipment in
the fire area, may necessitate immediate extinguishment.
Therefore, this publication assumes that there are a number of
situations where the extinguishment of natural gas fires is not only
appropriate, but desirable.
Fire Protection
FIGURE 1
OVERALL FIRE PROTECTION APPROACH
003380
Fire Prevention
Process and Site Design
Construction Material
Operation Criteria
Vapor Dispersion
Provisions of NFPA
Standard 59A
Industry Standards
Fire Control
Exposure Protection
Water
High Expansion Foam
Fire Extinguishment
Dry Chemicals
High Expansion Foam
Dry Chemicals

THE NATURAL GAS FIRE PROBLEM
Page 2
In the past, the natural gas fire problem was rather simple when
compared to today’s situation. At that time, nearly all our natural
gas was processed, transported, stored and distributed in the
vapor state. With the widespread application of cryogenic tech-
niques in recent years, the processing, transportation, storage and
vaporization of liquefied natural gas has added a new dimension
to the problem. Instead of being concerned about the fire extin-
guishing requirements for only the vapor state, design criteria
became necessary for both the vapor and liquid states.
Figure 2 illustrates some of the physical and chemical properties
of natural gas. The properties are approximated since the compo-
sition of natural gas covers a rather broad range.
Composition___________
Methane 83–99%
Ethane 1–13%
Propane 0.1 –3%
Butane 0.2–1.0%
Physical Properties_________________
Normal Boiling Point –255 to –263 °F
(–160 to –164 °C)
Density liquid at NBP 3 1/2 to 4 lb/gal
(Normal Boiling Point) (0.42-0.48 kg/L)
Density vapor at NBP (compared 1.47
with air at 70 °F (21.2 °C))
Liquid to vapor expansion 600 to 1
Heat of vaporization 220-248 Btu/lb
(512-577 kj/kg)
Theoretical vaporizing capability
of 1 cu. ft. (0.3 m2) of:
Dry earth 6 gal (22.7 L) LNG
(Liquefied Natural Gas)
Wet earth 20 gal (75.71 L) LNG
Water 24 gal (75.708 L) LNG
(1 gal water =
3.2 gal LNG)
Air 0.0005 gal
(0.6019 L) LNG
Combustion Properties____________________
Flammable range 5-14% (methane at
normal temperatures)
6-13% (methane near
minus 260 °F)
Heat of combustion 22,000 Btu/lb
(51,172,000 J/kg)
Burn rate, steady state pool 0.2-0.6 in./minute
Pool fire flame height 3 times base dimensions
of pool (slight wind)
FIGURE 2
Approximate Properties of Natural Gas2
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Page 3
THE NATURAL GAS FIRE PROBLEM (Continued)
After analysis of the characteristics of a natural gas fire, ANSUL
has concluded that the problem may be simplified to the extent
shown in Figure 3. This figure essentially illustrates the following:
A. State: The natural gas at the source of the fire problem will be
in either the vapor or the liquid state.
B. Configuration: A natural gas release may be rapid, producing
a pressurized flow. If the release occurs outdoors, the problem
is simplified. If, however, it occurs in a contained volume, flam-
mable concentrations may produce potentially explosive
conditions. Liquefied natural gas leaks may take the form of a
pressurized flow and, if the leakage rate is adequate, the
problem may be further complicated by the formation of a
liquid pool.
C. Variables: In the case of pressure fires in both the vapor and
liquid states, there are three very important variables that will
directly influence the ease or difficulty of extinguishment:
Impingement: If the natural gas jet is impinging on a vertical
surface (process equipment) or a horizontal surface (ground),
a fire will be significantly more difficult to extinguish than if the
jet is not impinging on a surface.
Preburn: The length of time that a fire has burned in an imping-
ing jet situation will proportionately increase the extinguishing
agent application rate that is required.
Obstructions: The presence of obstructions in the fire area will
influence the number of extinguishing agent application points
required to insure adequate agent coverage.
Within a contained volume, an important variable to be consid-
ered is that other flammables (refrigerants, etc.) may be
present. These other flammables could behave quite differ-
ently than natural gas with regard to flammable and explosive
limits.
The behavior of LNG (Liquefied Natural Gas) in a spill situation
is an important consideration in determining extinguishing
agent application requirements. The characteristics of the
surface on which a spill occurs will influence the initial rate of
vaporization. However, an approximation of the initial rate of
vaporization on both solid surfaces and water can be said to
be in the range of 50 ft3 per minute of vapor per ft2 (15.24 m3
per minute per m2) of LNG surface area.
State
Configuration
Variables
Natural Gas
Vapor
Pressure Contained
Liquid
Pressure/Pool Spill
Impingement
Preburn
Obstructions
Other
Flammables
Impingement
Preburn
Obstructions
Vaporization
Rate
Obstructions
FIGURE 3
Definition of the Natural Gas Fire
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Page 4
THE NATURAL GAS FIRE PROBLEM (Continued)
The steady-state vaporization rate, in contrast, is approxi-
mately 1 ft3 per minute of vapor per ft2 of LNG surface area
(0.3048 m3 per minute per m2). This rate is equivalent to a 1 ft
(0.3 m) deep pool evaporating in 10 hours, assuming that
steady-state had already been reached.
While a fire situation will produce a higher rate of vaporization
at steady-state, a fire of greater intensity will occur in an initial
spill situation. These factors are taken into account in the
design criteria (See Figure 12).
With this definition of the characteristics of a natural gas fire, it was
then possible to review candidate agents to determine their
compatibility with the problem.

THE CANDIDATE FIRE EXTINGUISHING AGENTS
Page 5
THE CANDIDATE FIRE EXTINGUISHING AGENTS
Historically, the only extinguishing agents accepted as effective on
natural gas vapor fires were dry chemicals and carbon dioxide.
Furthermore, due to the dry chemicals’ tremendous effectiveness
advantages over carbon dioxide, the latter is usually employed
only in areas where the dry chemicals may damage sensitive
equipment or where a total flooding technique can be employed.
Such agents as water, protein foam, aqueous film forming foams
(AFFF) and other water base agents have been found to have little
or no effectiveness in the extinguishment of vapor fires, or for that
matter, pressure fires in general. Hence, most fire extinguishment
experimentation and actual fire extinguishing experience in the
natural gas vapor fire field have been restricted to the dry chemi-
cal agents.
With the advent of LNG (Liquefied Natural Gas), most of the water
base agents were immediately ruled out since they were not only
ineffective, but their application on an LNG spill could worsen the
situation. NFPA 113 (“Standard for Low-, Medium-, and High-
Expansion Foams”) cautions against the use of foam or AFFF on
refrigerated or cryogenic fluids due to severe boiling and increased
vapor release that would follow.
One noteworthy exception to the use of water base agents on LNG
is high expansion foam, which has an extremely low water content.
High expansion foam experimentation on LNG fires has demon-
strated that this agent does have vapor dispersion and fire control
capabilities. Use of high expansion foam is discussed later in this
document.
At the moment, the only known agents that have demonstrated an
ability to completely extinguish LNG fires are the dry chemicals. In
this agent category, three types presently account for 95% of the
applications in the United States:
A. Sodium Bicarbonate Base (ANSUL PLUS-FIFTY): This
agent, which is the dry chemical first developed, has been
largely replaced by the more effective potassium bicarbonate
base material in the oil and gas industry.
B. Monoammonium Phosphate Base (ANSUL FORAY): This
agent is approximately as effective as the sodium bicarbonate
base material on flammable liquids and vapors. It has the
added advantage of being an effective extinguishing agent in
Class A (ordinary combustibles) fires.
C. Potassium Bicarbonate Base (ANSUL ‘Purple-K’): This
agent, which was introduced commercially in the United States
in the 1960s, has been shown to be more effective than the
sodium bicarbonate base material. Hence, it is becoming the
standard dry chemical in high intensity fire applications.

THE ANSUL NATURAL GAS FIRE EXTINGUISHMENT CONCEPT
Page 6
THE ANSUL NATURAL GAS FIRE EXTINGUISHMENT
CONCEPT
ANSUL has given very careful consideration to the characteristics
of the natural gas fire, the compatibility of, and experimental infor-
mation on, the available fire extinguishing agents. Combining this
with the practical aspects of the fire situation, ANSUL has devel-
oped a conceptual approach to the extinguishment of natural gas
fires. This concept, which outlines the selection and application of
most appropriate extinguishing agent for the various potential fire
situations, is illustrated in Figure 4.
The ANSUL concept is based on the following:
A. Vapor – Pressure Fires: The only extinguishing agents
commercially available in a wide range of equipment and
capable of extinguishing flammable gas fires are the dry chem-
icals and carbon dioxide. Of these two types, the dry chemi-
cals are more effective and have the added advantage of
concise experimental data to support the design criteria in this
application. Of the two more common dry chemicals, the
potassium bicarbonate base agent is more effective, but is
also more expensive than the sodium bicarbonate base agent.
Therefore, some users prefer the sodium bicarbonate base
agent from an economical standpoint.
State
Configuration
Best Solution
Natural Gas
Vapor
Pressure Contained
Liquid
Pressure/Pool Spill
Dry Chemical Carbon
Dioxide
Dry Chemical
or
Dry Chemical
and
High Expansion
Foam
Dry Chemical
or
Dry Chemical
and
High Expansion
Foam
FIGURE 4
The ANSUL Concept
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THE ANSUL NATURAL GAS FIRE EXTINGUISHMENT CONCEPT
Page 7
THE ANSUL NATURAL GAS FIRE EXTINGUISHMENT
CONCEPT (Continued)
B. Vapor – Contained Fires: The most appropriate means for
extinguishing a fire or inerting the atmosphere prior to a fire in
an enclosed volume is by using a gaseous extinguishing agent
and a total flooding approach. In enclosed volumes, these
systems are normally operated automatically when gas detec-
tors sense a concentration of 1/4 to 1/2 the lower explosive
limit of the fuel involved.
Since there may be flammables other than natural gas in the
protected volume, the system should be designed to produce
an agent concentration adequate to inert the most difficult fuel
present.
C. Liquid – Pressure/Pool Fires: LNG (Liquefied Natural Gas)
pressure fires of any significance will usually produce pools of
the fuel in the vicinity of the failure. For the same reasons
outlined for pressure fires with the vapor, the dry chemicals are
the most effective agents for LNG pressure fires. However, the
presence of obstructions (process equipment, piping, etc.) is
extremely significant since the dry chemical may not extin-
guish flames that are substantially shielded from the agent
stream. In this case, one has two alternatives:
Provide enough dry chemical application points to preclude
the possibility of any flames being shielded by obstructions.
Utilize high expansion foam to bring the spill fire under control
by vapor dispersion and radiation reduction, after which it may
be desirable to extinguish the remaining flames with dry chem-
ical.
D. Liquid – Spill Fires: In this type of fire, there are two signifi-
cant considerations that must be taken into account during the
design of the fire extinguishment equipment. One is the rate of
natural gas vaporization anticipated as a result of the spill of
LNG on the surrounding surface. The design criteria devel-
oped for both dry chemical and high expansion foam were
based on experiments where the burning LNG was vaporizing
at an approximate rate of 0.5 in./minute (1.27 cm/minute). A
“fresh” LNG spill on the ground, especially if the ground has a
high moisture content, will result in an increased vaporization
rate up to 3.0 times steady state conditions17. This higher
vaporization rate will increase the fire intensity. This problem is
very important in automatic systems where the agent is
intended to be applied very quickly (within seconds) after igni-
tion.
This problem is not so significant with manually operated fire
extinguishing equipment as the LNG (Liquefied Natural Gas)
spill will usually freeze the ground to such an extent that the
vaporization rate will have reached equilibrium before the
extinguishers are manned. This does not, however, imply that
it is sound practice to delay the application of the agent until a
stabilized condition is attained.
The minimum dry chemical application rates which will just
extinguish a steady state LNG spill fire (negligible ground
heating effect and maximum radiation-induced burning rates)
are increased by a factor of up to 2.5 for the burning rates that
exist for fires immediately following the LNG spill on land. (See
Figure 12.)
A second important consideration is the presence of obstruc-
tions in the spill area. Like pressure/pool fires, two alternatives
are available: Use of dry chemical from sufficient application
points to preclude the possibility of shielded flames; or use of
high expansion foams to control the fire followed by dry chem-
ical to extinguish the remaining flames.
It should be recognized that in both pool and spill fires vapor
concentration reduction may be desirable under certain conditions.
The application of high expansion foam can accomplish this as
previously stated. Specific reference to its use is found on Page
14.

THE EXPERIMENTAL EXPERIENCE
Page 8
THE EXPERIMENTAL EXPERIENCE
The basis for ANSUL’s concept and design recommendations is a
direct result of five major testing programs involving the control
and extinguishment of natural gas and LNG fires. The programs
are illustrated in Figure 5.
Types of Agents
Site Date Tests Tests Tested___ ____ _____ _____ ______
Longview, 1951 91 Vapor-Non- Sodium
Texas7 lmpinging Jet Bicarbonate
Vapor-Horizontal
Impinging Jet
Vapor-Downward
Impinging Jet
Vapor-Split Pipe
Impinging Jet
Six Lakes, 1965 48 Vapor-Non- Sodium
Michigan8 lmpinging Jet Bicarbonate
Vapor-Horizontal Potassium
Impinging Jet Bicarbonate
Monoammonium
Phosphate
Six Lakes, 1969 107 Vapor-Non- Potassium
Michigan9 lmpinging Jet Bicarbonate
Potassium
Chloride
Marinette, 1972 43 LNG Pool Fires Sodium
Wisconsin10 Bicarbonate
Potassium
Bicarbonate
High Expansion
Foam
Monoammonium
Phosphate
Norman, 1973 100 LNG Pool Fires Sodium
Oklahoma17 (Accelerated Bicarbonate
Boil-Off Rates) Potassium
Bicarbonate
High Expansion
Foam
FIGURE 5
ANSUL Large Scale Natural Gas Fire Testing Programs
The 1951 Longview program established the technical information
for the use of sodium bicarbonate base dry chemical on four vari-
ations of gas pressure fires that are typically found in the natural
gas transmission industry.
The 1965 Six Lakes program was conducted to compare the effec-
tiveness of potassium bicarbonate, monoammonium phosphate
and sodium bicarbonate base dry chemicals on two of the four gas
transmission hazards tested in the Longview program. From this
experimentation, definite design criteria for the potassium bicar-
bonate base agent were developed for the two hazards tested,
and correlations between the relative extinguishing effectiveness
of sodium and potassium bicarbonate base agents produced the
potassium bicarbonate base agent design criteria for the other two
hazards.
The 1969 Six Lakes program established the potassium bicarbon-
ate base agent requirements for low flow rate (200-1600 ft3/sec
(5.7-45.3 m3/sec)) gas fires and also served to compare the rela-
tive fire extinguishing effectiveness of potassium bicarbonate and
potassium chloride base dry chemicals.
The 1972 program, conducted at ANSUL’s Fire Technology
Center, was performed to determine the minimum agent require-
ments for sodium bicarbonate, potassium bicarbonate, monoam-
monium phosphate and high expansion foam on LNG pool fires of
400 (37.2 m2) and 1200 (111.5 m2) ft2 in area.
The 1973 tests, conducted at Norman, Oklahoma, determined that
“fresh” LNG spills with accelerated boil-off rates increased dry
chemical flow rates for extinguishment.

THE GENERAL BEHAVIOR OF EXTINGUISHING AGENTS
Page 9
In situations other than total flooding, it is generally accepted that
if an extinguishing agent is not applied to a fire at a sufficient rate,
the fire will not be extinguished12. It is also known that, up to a
certain point, increasing the agent’s application rate will result in a
shorter extinguishment time.
This extinguishing time and agent application rate relationship has
been found to be hyperbolic as shown in Figure 6.
003385
FIGURE 6
General Relationship of Agent Rate and Extinguishing Time
AGENT APPLICATION RATE (R – lb/sec (kg/sec))Rminute
tminute
EXTINGUISHINGTIME(t–sec)

Page 10
(Continued)
Another illustration of this behavior is shown in Figure 7, where the
agent quantity and agent application rate are plotted. In a number
of experimental programs, it has been determined that there is an
optimum agent application rate (Ropt) at which rate the least
amount of agent (Qminute) will be required for extinguishment.
Application rates less than Ropt result in longer extinguishment
times and the expenditure of more agent than at Ropt.
Furthermore, if the application rate is less than Rmin, an infinite
quantity of agent would theoretically be unable to extinguish the
subject fire.
Rmin has been found to be in the range of 0.4 to 0.5 Ropt, which
accounts for the 2.0 factor of safety usually put on Rminute to
arrive at a design rate. If the agent is applied at a rate greater than
Ropt, the time of extinguishment is usually not reduced to any
significance (as shown in Figure 6) resulting essentially in the
wasting of agent (Q >> Qminute).
003386
FIGURE 7
General Relationship of Agent Rate and Quantity
AGENT APPLICATION RATE (R – lb/sec (kg/sec))
Rminute
Qminute
AGENTQUANTITY(Q–lb)
Ropt

THE SPECIFIC AGENT FLOW RATE REQUIREMENTS FOR NATURAL GAS FIRES
Page 11
THE SPECIFIC AGENT FLOW RATE REQUIREMENTS FOR
NATURAL GAS FIRES
After all the experimental information was analyzed, recom-
mended design criteria were developed for the application of the
extinguishing agents to the various natural gas fire configurations.
These recommendations are graphically shown in Figures 8
through 15.
Figure 8: Recommended Dry Chemical Design Application Rates
for the Extinguishment of Non-lmpinging Natural Gas and LNG
Pressure Fires.
Figure 9: Recommended Dry Chemical Design Application Rates
for the Extinguishment of Horizontal Impinging Natural Gas and
LNG Pressure Fires.
Figure 10: Recommended Dry Chemical Design Application
Rates for the Extinguishment of Downward Impinging Split Pipe
Natural Gas and LNG Fires.
Figure 11: Effects of Dry Chemical Application Rate on Fire
Extinguishment Time for LNG Spill Fires with a Total Evaporation
Rate of 0.5 Inches per Minute.
Density for the Extinguishment of LNG Pool Fires for Various
Vaporization Rates.
Density for the Extinguishment of LNG Fires for the Steady State
Vaporization Rate.
Density for the Extinguishment of LNG Fires for Initial Accelerated
Vaporization Rates.
Figure 15: Effects of Foam Application Rate of Control Time for
LNG Spill Fires Using 500:1 High Expansion Foam.
Figures 16 Through 20: Recommended Dry Chemical Design
Quantities Based on the Recommended Application Rates Shown
above, using 30 Second Effective Discharge Time. These figures
can be used to estimate total agent design quantities desired.
In general, the following additional criteria apply:
A. Dry Chemical Fire Extinguishers utilizing high velocity dry
chemical streams are superior to soft or “fan” streams for the
extinguishment of natural gas or LNG fires. Care should be
exercised on LNG spill fires to avoid disrupting the liquid
surface of the fuel with the agent which would cause an
increase in the burning intensity.
B. All the design criteria for dry chemical on natural gas pressure
fires employ a safety factor of two (2.0) on the minimum rate
found necessary to effect extinguishment in the experimental
programs. When designing automatic fixed nozzle dry chemi-
cal systems, the applied safety factors would be increased
substantially to achieve much higher application rate densities
(Ib/sec/ft2). The minimum design rate for LNG spills in Figure
11 also has a safety factor of 2.0 times the rate found neces-
sary to effect extinguishment in the testing.
C. Dry chemical extinguishers and extinguishing systems should
be selected to produce optimized discharge times according to
application conditions.
D. From NFPA 11 “Standard for Low-, Medium-, and High-
Expansion Foam”3: “In (testing), control was established with
expansion ratios greater than 250:1, although an expansion
ratio of about 500:1 proved most effective.”
E. The design rate selected for high expansion foam must
produce fire control with at least 90% reduction of the radiant
heat flux under the conditions described in Figure 15. It is
generally accepted that a minimum application rate of 6 ft3 per
minute per ft2 (1.8288 m3 per minute per m2) is desirable as
determined by testing. Under some circumstances faster
control times may be essential, or longer control times accept-
able. The entire foam application rate/fire control time relation-
ship has been included in Figure 15.
F. In the combined use of high expansion foam and dry chemi-
cals, the high expansion foam application must be continued
until the dry chemical has completely extinguished all flames.
For the graphs in Figures 8 through 15, the criteria shown in solid
lines are based on actual experimentation and those shown in
dashed lines are correlations (based on relative extinguishing
effectiveness of the agents) or extrapolations. The design infor-
mation on LNG pressure fires are theoretical and it assumes that
the LNG completely and immediately flashes to a vapor at 70 °F
(21 °C). upon exiting the failure point. The dry chemical rates are
then based on the free volume of natural gas using an expansion
factor of 600. This approach is justified on the basis of reported
correlations attained in experimentation with gaseous and liquid
propane.14

THE ANSUL RECOMMENDED AGENT QUANTITY REQUIREMENTS
Page 12
RECOMMENDED DRY CHEMICAL DESIGN APPLICATION
RATES FOR NON-IMPINGING NATURAL GAS AND LNG
PRESSURE FIRES (2.0 SAFETY FACTOR APPLIED)
FIGURE 8
003387
(Based on data from
References 7, 8 and 9.)
LNG agent requirements
are theoretical and assume
that the LNG completely
vaporizes upon contact with
the air and immediately
expands to its 70 °F
(21.1 °C) condition (600
times expansion).
PLUS-FIFTY
DryChemicalDesignApplicationRate–lb/sec(kg/sec)
0 500 1000 1500 2000 2500
(14.2) (28.3) (42.5) (56.6) (70.8)
Natural Gas Flow Rate – ft3/sec (m3/sec)
70
(31.8)
60
(27.2)
50
(22.7)
40
(18.1)
30
(13.6)
20
(9.1)
10
(4.5)
0
0 500 (1893) 1000 (3785) 1500 (5678)
LNG Flow Rate – gal/minute (liters/minute)
‘Purple-K’

Page 13
RATES FOR HORIZONTAL IMPINGING NATURAL GAS AND
LNG PRESSURE FIRES (2.0 SAFETY FACTOR APPLIED)
FIGURE 9
003388
(Based on data from
Dashed lines indicate
extrapolations or correla-
tions: LNG agent require-
ments are theoretical and
assume that the LNG
completely vaporizes upon
contact with the air and
immediately expands to its
70 °F (21.1 °C) condition
(600 times expansion).
PLUS-FIFTY
0 200 400 600 800 1000
(5.7) (11.3) (17) (22..7) (28.3)
70
(31.8)
60
(27.2)
50
(22.7)
40
(18.1)
30
(13.6)
20
(9.1)
10
(4.5)
0
0 200 (757) 400 (1514) 600 (2271)
‘Purple-K’

Page 14
RATES FOR DOWNWARD IMPINGING SPLIT PIPE NATURAL
GAS AND LNG PRESSURE FIRES (2.0 SAFETY FACTOR
APPLIED)
FIGURE 10
003389
(Based on data from
Dashed lines indicate
extrapolations or correla-
tions: LNG agent require-
ments are theoretical and
assume that the LNG
completely vaporizes upon
contact with the air and
immediately expands to its
70 °F (21.1 °C) condition
(600 times expansion).
PLUS-FIFTY
0 100 200 300 400 500
(2.8) (5.7) (8.5) (11.3) (14.2)
70
(31.8)
60
(27.2)
50
(22.7)
40
(18.1)
30
(13.6)
20
(9.1)
10
(4.5)
0
0 100 (378.5) 200 (757.1) 300 (1135.7)
‘Purple-K’

Page 15
DRY CHEMICAL APPLICATION RATE VS. EXTINGUISHMENT
TIME FOR LNG SPILL FIRES WITH BURNING RATE OF
0.5 IN./MINUTE (1.27 cm/minute)
Based on data from Reference 10. Design Application Rate is
Based on 2.0 Safety Factor Applied to Minimum Rate
PLUS-FIFTY Design Application Rate
PLUS-FIFTY
Minimum PLUS-FIFTY
‘Purple-K’
‘Purple-K’ Design Application Rate
ExtinguishmentTime–(seconds)
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
(0.05) (0.10) (0.15) (0.2) (0.24) (0.29) (0.34)
Dry Chemical Application Rate – (lb/sec/ft2)
30
25
20
15
10
5
0
Minimum ‘Purple-K’
FIGURE 11
003390

Page 16
DENSITIES FOR A RANGE OF LNG POOL BURNING RATES
(2.0 SAFETY FACTOR APPLIED)
FIGURE 12
003391
PLUS-FIFTY
0.5 1.0 1.5
(1.27) (2.5) (3.81)
LNG Linear Burning Rate – in./minute (cm/minute)
‘Purple-K’
DryChemicalDesignApplicationDensity–(lb/sec/ft2)
0.07
(0.34)
0.06
(0.29)
0.05
(0.24)
0.04
(0.2)
0.03
(0.15)
0.02
(0.10)
0.01
(0.05)
0

Page 17
RATES FOR LNG POOLS BURNING AT 0.5 IN./MINUTE
(1.27 cm/minute) (2.0 SAFETY FACTOR APPLIED)
FIGURE 13
003392
10 50 100 500 1000 5000 10000
(0.9) (4.6) (9.3) (46.5) (92.9) (464.5) (929)
LNG Area – ft2 (m2)
1000
(453.6)
500
(226.8)
300
(136.1)
200
(90.7)
100
(45.4)
50
(22.7)
30
(13.6)
20
(9.1)
10
(4.54)
5
(2.27)
3
(1.36)
2
(0.91)
1 (0.45)

Page 18
RECOMMENDED DRY CHEMICAL DESIGN APPLICATION RATES
FOR LNG POOLS BURNING AT 1.5 IN./MINUTE (3.81 cm/minute)
(2.0 SAFETY FACTOR APPLIED)
10 50 100 500 1000 5000 10000
(0.9) (4.6) (9.3) (46.5) (92.9) (464.5) (929)
1000
(453.6)
500
(226.8)
300
(136.1)
200
(90.7)
100
(45.4)
50
(22.7)
30
(13.6)
20
(9.1)
10
(4.54)
5
(2.27)
3
(1.36)
2
(0.91)
1 (0.45)
FIGURE 14
003393
PLUS-FIFTY‘Purple-K’

Page 19
EFFECT OF FOAM APPLICATION RATE ON CONTROL TIME
FOR LNG SPILL FIRE USING 500:1 HIGH EXPANSION FOAM
If LNG pools are burning, the common practice is to provide foam
discharge for 3 times the average response time for fire fighting
personnel to arrive on site and extinguish the fire with dry chemi-
cal. In the absence of this information, it has been generally
accepted for the purpose of design that a minimum 60 minute
continuous foam discharge is adequate for foam concentrate
storage tank sizing. ANSUL recommends continuous foam
discharge for burning LNG situations.
If LNG pools are not burning and foam is being used for vapor miti-
gation, it is desirable to keep a minimum of 3 ft. (0.91 m) depth of
foam over the spill area. Manually ON/OFF cycling the discharge
as required is recommended to maximize available foam concen-
trate supplies. After initial foam coverage based on 3 minutes of
discharge, it is possible that reapplications may only be required
every 30 minutes. This can be affected by individual site condi-
tions.
Steady state LNG pool evaporation is approximately 0.025 in.
(0.0635 cm) per minute. When maintaining a 3 ft (0.91 m) foam
depth over the spill area of non-burning LNG, the evaporation rate
may increase in the range of 0.050 in. (0.127 cm) to 0.075 in.
(0.191 cm) per minute from the heat input provided by the foam
drainage. Evaporation rates of continuously foamed LNG that is
burning may be in a range above 0.075 in. (0.191 cm) per minute.
The evaporation data listed above is based on JET-X Agent and
Hardware testing conducted at ANSUL’s R&D facility in a cement
containment pit using LNG that was above 99% Methane.
Fire Control is defined as when the radiant heat flux
has been reduced by 90 percent or more.
FireControlTime–Seconds
0 5 6 10 15
(1.5) (1.83) (3.05) (4.6)
High Expansion Foam Application Rate – ft3/minute/ft2 (m3/minute/m2)
300
250
200
150
100
50
0
Six (6) ft3/minute/ft2 (1.83 m3/minute/m2)
is a generally accepted minimum
design rate.
FIGURE 15
003394

Page 20
RECOMMENDED DRY CHEMICAL DESIGN QUANTITIES FOR
NON-IMPINGING NATURAL GAS AND LNG PRESSURE FIRES
FIGURE 16
003395
(Based on Recommended
Application Rates and
30 Seconds Effective
Discharge Time)
PLUS-FIFTY
DryChemicalDesignQuantities–lb(kg)
0 500 1000 1500 2000 2500
(14.2) (28.3) (42.5) (56.6) (70.8)
1400
(635)
1200
(544.3)
1000
(453.6)
800
(362.9)
600
(272.2)
400
(181.4)
200
(90.7)
0
0 500 (1893.7) 1000 (3785.4) 1500 (5678.1)
‘Purple-K’

Page 21
HORIZONTAL IMPINGING NATURAL GAS AND LNG
PRESSURE FIRES
FIGURE 17
003396
Discharge Time)
PLUS-FIFTY
0 200 4000 600 800 1000
(5.7) (11.3) (17) (22.7) (28.3)
1400
(635)
1200
(544.3)
1000
(453.6)
800
(362.9)
600
(272.2)
400
(181.4)
200
(90.7)
0
0 200 (757.1) 400 (1514.2) 600 (2271.2)
‘Purple-K’

Page 22
DOWNWARD IMPINGING SPLIT PIPE NATURAL GAS AND
LNG PRESSURE FIRES
FIGURE 18
003397
Discharge Time)
PLUS-FIFTY
0 100 200 300 400 500
(2.8) (5.7) (8.5) (11.3) (14.2)
1400
(635)
1200
(544.3)
1000
(453.6)
800
(362.9)
600
(272.2)
400
(181.4)
200
(90.7)
0
0 100 (378.5) 200 (757.1) 300 (1135.6)
‘Purple-K’

Page 23
LNG POOLS BURNING AT 0.5 IN./MINUTE (1.3 cm/minute)
(30 SECOND DISCHARGE TIME)
10 100 1000 10000
(0.9) (9.3) (93) (929)
10000
(4536)
1000
(453.6)
100
(45.4)
10 (4.5)
DryChemicalDesignQuantity–lb/kg
FIGURE 19
003398
PLUS-FIFTY
‘Purple-K’

Page 24
LNG POOLS BURNING AT 1.5 IN./MINUTE (3.8 cm/minute)
(30 SECOND DISCHARGE TIME)
10 100 1000 10000
(0.9) (9.3) (93) (929)
10000
(4536)
1000
(453.6)
100
(45.4)
10 (4.5)
DryChemicalDesignQuantity–lb(kg)
FIGURE 20
003399
PLUS-FIFTY‘Purple-K’

COMMERCIALLY AVAILABLE FIRE SUPPRESSION EQUIPMENT
Page 25
COMMERCIALLY AVAILABLE FIRE SUPPRESSION
EQUIPMENT
A. High Expansion Foam: Foam expansion rates of 500:1 are
favored for fire control and are well-suited for vapor dispersion.
ANSUL recommends the following high expansion foam
generators for LNG with performance characteristics as
shown.
Calculating Foam Quantity For Local Application (LNG)
High Expansion Generators Typical Discharge Characteristics
Generator Inlet
Pressure Foam Output Solution Flow
Generator psi (bar) cfm (cmm) gpm (lpm) Expansion________ ____________ ____________ ____________ _________
JET-X-2A 50 (3.45) 2,240 (63) 35 (132.5) 465:1
75 (5.17) 3,200 (91) 42 (159) 555:1
100 (6.89) 3,735 (106) 50 (189.3) 545:1
JET-X-15A (LNG) 50 (3.45) 12,625 (357) 180 (681.4) 525:1
75 (5.17) 14,495 (410) 220 (832.8) 495:1
100 (6.89) 18,240 (516) 260 (984.2) 525:1
JET-X-20 40 (2.76) 13,443 (381) 212 (802.5) 474:1
50 (3.45) 16,034 (454) 238 (900.9) 504:1
75 (5.17) 21,145 (599) 294 (1112.9) 538:1
100 (6.89) 24,301 (688) 338 (1279.5) 538:1
B. Dry Chemical: A complete line of dry chemical extinguish-
ment systems have been designed specifically for natural gas
and flammable liquid applications. Figure 21 summarizes the
ANSUL dry chemical product line, illustrating the flow rates,
which can be related to the data contained in this report.
Category Agents Extinguisher Capacity Flow Rate
Hand Portable PLUS-FIFTY 10, 20, 30 lb 1.5-2.5 lb/sec
(4.5, 9, 13.6 kg) (0.7-1.1 kg/sec)
‘Purple-K’ 9, 18, 27 lb
(4.1, 8.2, 12.2 kg)
Wheeled PLUS-FIFTY 150, 350 lb (68, 158.8 kg) 4.5-8.5 Ib/sec (2-3.9 kg/sec)
‘Purple-K’ 125, 300 lb (56.7, 136.1 kg)
Hand Hose Line PLUS-FIFTY 150, 350, 500, 1000, 4.5-10.0 Ib/sec
Systems 1500, 2000, 3000 lb (2-4.5 kg/sec)
(68, 158.8, 226.8, 453.6, for hand lines
680.4, 907.2, 1360.8 kg)
Vehicle Mounted ‘Purple-K’ 125, 300, 450, 900, 1350, 25-100 Ib/sec
1800, 2700 lb (11.3-45.4 kg/sec)
(56.7, 136.1, 204.1, 408.2, for turrets for 1350 lb (612.4 kg)
612.4, 816.5, 1224.3) capacity and larger
Engineered 4-100 Ib/sec (1.8-45.4 kg/sec)
Systems for piped systems depending on their capacity
FIGURE 21
C. Detection and Control: This report is not intended to provide
detailed coverage of the detection and control aspects of fire
control and extinguishment. However, it should be recognized
that whether automatic or manual, the detection control
system design is integral to the extinguishing system design, if
an optimum total system control and extinguishing capability is
to be realized.

BIBLIOGRAPHY
Page 26
BIBLIOGRAPHY
1. National Fire Protection Association, “Storage and Handling of
Liquefied Natural Gas (LNG),” NFPA Standard 59A.
2. Walls, W. L., “LNG: A Fire Service Appraisal,” FIRE
JOURNAL, January, 1972.
3. National Fire Protection Association, “Standard For Low-,
Medium-, and High-Expansion Foams,” NFPA 11.
4. REMOVED
5. REMOVED
6. REMOVED
7. “Natural Gas Fire Tests,” Technical Bulletin Number 32, Ansul
Incorporated, Marinette, Wisconsin.
8. “Fire Tests With Natural Gas Jets – Six Lakes,” Ansul
Incorporated, Marinette, Wisconsin.
9. “Fire Tests With Natural Gas Jets – Six Lakes,” Ansul
Incorporated, Marinette, Wisconsin (1969).
10. “LNG Fire Control, Fire Extinguishment and Vapor Dispersion
Tests,” University Engineers, 1972.
11. REMOVED
12. Guise, A. B., and Lindlof, J. A., “A Dry Chemical Extinguishing
System,” NFPA QUARTERLY, Volume 49, Number 1, July,
1955.
13. REMOVED
14. Guise, A. B., “Fire Tests Made On LP Gas,” LP GAS, May,
1948.
15. REMOVED
16. REMOVED
17. ”An Experimental Study on the Mitigation of Flammable Vapor
Dispersion and Fire Hazards Immediately Following LNG
Spills On Land,” For AGA by University Engineers, February,
1974.

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