ANSUL_Fire Protection Solutions for LNG

7/23/2019 ANSUL_Fire Protection Solutions for LNG

1/29

FIRE PROTECTION SOLUTIONS

FOR LIQUEFIED NATURAL GAS


2/29

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 RequirementsFor Natural Gas Fires 11

The ANSUL Recommended Agent Quantity Requirements 12

Bibliography 26


3/29

INTRODUCTIONPage 1

INTRODUCTION

The liquefaction of natural gas, which reduces its volume by afactor of over 600, has made the storage and transportation of thisfuel economically attractive. However, this liquefaction techniquehas 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 overlookedby the gas utilities, nor gone unnoticed by the authorities and thegeneral public. The safety of natural gas, especially from the fireprotection standpoint, has been the subject of considerableresearch in recent years, and many techniques have been refinedin the overall fire protection approach to the hazard.

As with any other potential hazard, the fire protection for a naturalgas facility consists of three elements: fire prevention, fire control,and fire extinguishment. Figure 1 illustrates these elements asthey relate to LNG (Liquefied Natural Gas) processes.

The considerations for fire prevention are well documented in theNational Fire Protection Associations Standard on Storage andHandling of Liquefied Natural Gas (LNG), NFPA 59A1. In additionthe techniques for fire control, especially for exposure protectionare not that different with natural gas than with many other flam-

mable materials. There is a great amount of historical experiencein this area. The primary element to which this publicationaddresses itself is the extinguishment of fires involving naturagas, in the liquefied, vapor and gaseous states. Abrief descriptionof vapor dispersion, which can minimize downwind drift of vapoclouds, and radiation intensity is also made10.

NFPA 59A recommends that normally gas fires (including LNGshould not be extinguished until the fuel source can be shut off.However, a gas fire which places personnel in severe danger, agas shutoff valve which is involved in the fire, or a fire which indi-rectly endangers personnel through thermal failure of equipment inthe fire area, may necessitate immediate extinguishment.

Therefore, this publication assumes that there are a number osituations where the extinguishment of natural gas fires is not onlyappropriate, but desirable.

Fire Protection

FIGURE 1

OVERALL FIRE PROTECTION APPROACH003380

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


4/29

THE NATURAL GAS FIRE PROBLEMPage 2

THE NATURAL GAS FIRE PROBLEM

In the past, the natural gas fire problem was rather simple whencompared to todays situation. At that time, nearly all our naturalgas was processed, transported, stored and distributed in thevapor 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 dimensionto the problem. Instead of being concerned about the fire extin-guishing requirements for only the vapor state, design criteriabecame necessary for both the vapor and liquid states.

Figure 2 illustrates some of the physical and chemical propertiesof natural gas. The properties are approximated since the compo-sition of natural gas covers a rather broad range.

Composition___________

Methane 8399%

Ethane 113%

Propane 0.1 3%

Butane 0.21.0%

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 1.47with 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 capabilityof 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 atnormal temperatures)

6-13% (methane nearminus 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 dimensionsof pool (slight wind)

FIGURE 2

Approximate Properties of Natural Gas2003381


5/29


THE NATURAL GAS FIRE PROBLEM (Continued)

After analysis of the characteristics of a natural gas fire, ANSULhas concluded that the problem may be simplified to the extentshown in Figure 3. This figure essentially illustrates the following:

A. State: The natural gas at the source of the fire problem will bein either the vapor or the liquid state.

B. Configuration: A natural gas release may be rapid, producinga pressurized flow. If the release occurs outdoors, the problemis simplified. If, however, it occurs in a contained volume, flam-mable concentrations may produce potentially explosiveconditions. Liquefied natural gas leaks may take the form of apressurized flow and, if the leakage rate is adequate, theproblem may be further complicated by the formation of aliquid pool.

C. Variables: In the case of pressure fires in both the vapor andliquid states, there are three very important variables that willdirectly influence the ease or difficulty of extinguishment:

Impingement: If the natural gas jet is impinging on a verticalsurface (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 extinguishingagent application rate that is required.

Obstructions:The presence of obstructions in the fire area wilinfluence 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 bepresent. These other flammables could behave quite differently than natural gas with regard to flammable and explosivelimits.

The behavior of LNG (Liquefied Natural Gas) in a spill situationis an important consideration in determining extinguishingagent application requirements. The characteristics of thesurface on which a spill occurs will influence the initial rate ovaporization. However, an approximation of the initial rate ovaporization on both solid surfaces and water can be said tobe 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

OtherFlammables

Impingement

Preburn

Obstructions

VaporizationRate

Obstructions

FIGURE 3

Definition of the Natural Gas Fire003382


6/29


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 thatsteady-state had already been reached.

While a fire situation will produce a higher rate of vaporizationat steady-state, a fire of greater intensity will occur in an initialspill situation. These factors are taken into account in thedesign criteria (See Figure 12).

With this definition of the characteristics of a natural gas fire, it wasthen possible to review candidate agents to determine theircompatibility with the problem.


7/29

THE CANDIDATE FIRE EXTINGUISHING AGENTSPage 5

THE CANDIDATE FIRE EXTINGUISHING AGENTS

Historically, the only extinguishing agents accepted as effective onnatural gas vapor fires were dry chemicals and carbon dioxide.Furthermore, due to the dry chemicals tremendous effectivenessadvantages over carbon dioxide, the latter is usually employedonly 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 littleor no effectiveness in the extinguishment of vapor fires, or for thatmatter, pressure fires in general. Hence, most fire extinguishmentexperimentation and actual fire extinguishing experience in thenatural gas vapor fire field have been restricted to the dry chemi-cal agents.

With the advent of LNG (Liquefied Natural Gas), most of the waterbase agents were immediately ruled out since they were not onlyineffective, but their application on an LNG spill could worsen thesituation. NFPA 113 (Standard for Low-, Medium-, and High-Expansion Foams) cautions against the use of foam or AFFF onrefrigerated or cryogenic fluids due to severe boiling and increasedvapor release that would follow.

One noteworthy exception to the use of water base agents on LNGis 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 controlcapabilities. Use of high expansion foam is discussed later in thisdocument.

At the moment, the only known agents that have demonstrated anability to completely extinguish LNG fires are the dry chemicals. Inthis agent category, three types presently account for 95% of theapplications in the United States:

A. Sodium Bicarbonate Base (ANSUL PLUS-FIFTY): Thisagent, which is the dry chemical first developed, has beenlargely replaced by the more effective potassium bicarbonatebase material in the oil and gas industry.

B. Monoammonium Phosphate Base (ANSUL FORAY): Thisagent is approximately as effective as the sodium bicarbonatebase material on flammable liquids and vapors. It has theadded advantage of being an effective extinguishing agent inClass A (ordinary combustibles) fires.

C. Potassium Bicarbonate Base (ANSUL Purple-K): Thisagent, which was introduced commercially in the United Statesin the 1960s, has been shown to be more effective than thesodium bicarbonate base material. Hence, it is becoming thestandard dry chemical in high intensity fire applications.


8/29

THE ANSUL NATURAL GAS FIRE EXTINGUISHMENT CONCEPTPage 6

THE ANSUL NATURAL GAS FIRE EXTINGUISHMENTCONCEPT

ANSUL has given very careful consideration to the characteristicsof the natural gas fire, the compatibility of, and experimental infor-mation on, the available fire extinguishing agents. Combining thiswith the practical aspects of the fire situation, ANSUL has devel-

oped a conceptual approach to the extinguishment of natural gasfires. This concept, which outlines the selection and application ofmost appropriate extinguishing agent for the various potential firesituations, is illustrated in Figure 4.

The ANSUL concept is based on the following:

A. Vapor Pressure Fires: The only extinguishing agentscommercially available in a wide range of equipment andcapable 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 ofconcise experimental data to support the design criteria in thisapplication. Of the two more common dry chemicals, thepotassium bicarbonate base agent is more effective, but isalso more expensive than the sodium bicarbonate base agent.Therefore, some users prefer the sodium bicarbonate baseagent from an economical standpoint.

State

Configuration

Best Solution

Natural Gas

Vapor

Pressure Contained

Liquid

Pressure/Pool Spill

Dry Chemical CarbonDioxide

Dry ChemicalorDry ChemicalandHigh ExpansionFoam

Dry ChemicalorDry ChemicalandHigh ExpansionFoam

FIGURE 4

The ANSUL Concept003382


9/29

THE ANSUL NATURAL GAS FIRE EXTINGUISHMENT CONCEPTPage 7

THE ANSUL NATURAL GAS FIRE EXTINGUISHMENTCONCEPT (Continued)

B. Vapor Contained Fires: The most appropriate means forextinguishing a fire or inerting the atmosphere prior to a fire inan enclosed volume is by using a gaseous extinguishing agentand 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 explosivelimit of the fuel involved.

Since there may be flammables other than natural gas in theprotected volume, the system should be designed to producean agent concentration adequate to inert the most difficult fuelpresent.

C. Liquid Pressure/Pool Fires: LNG (Liquefied Natural Gas)pressure fires of any significance will usually produce pools ofthe fuel in the vicinity of the failure. For the same reasonsoutlined for pressure fires with the vapor, the dry chemicals arethe most effective agents for LNG pressure fires. However, thepresence of obstructions (process equipment, piping, etc.) isextremely significant since the dry chemical may not extin-guish flames that are substantially shielded from the agentstream. In this case, one has two alternatives:

Provide enough dry chemical application points to precludethe possibility of any flames being shielded by obstructions.

Utilize high expansion foam to bring the spill fire under controlby vapor dispersion and radiation reduction, after which it maybe 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 thedesign of the fire extinguishment equipment. One is the rate ofnatural gas vaporization anticipated as a result of the spill ofLNG on the surrounding surface. The design criteria devel-oped for both dry chemical and high expansion foam werebased on experiments where the burning LNG was vaporizingat an approximate rate of 0.5 in./minute (1.27 cm/minute). Afresh LNG spill on the ground, especially if the ground has ahigh moisture content, will result in an increased vaporizationrate up to 3.0 times steady state conditions17. This highervaporization rate will increase the fire intensity. This problem isvery important in automatic systems where the agent isintended to be applied very quickly (within seconds) after igni-tion.

This problem is not so significant with manually operated fireextinguishing equipment as the LNG (Liquefied Natural Gas)spill will usually freeze the ground to such an extent that thevaporization rate will have reached equilibrium before theextinguishers are manned. This does not, however, imply thatit is sound practice to delay the application of the agent until astabilized condition is attained.

The minimum dry chemical application rates which will justextinguish a steady state LNG spill fire (negligible groundheating effect and maximum radiation-induced burning rates)are increased by a factor of up to 2.5 for the burning rates thatexist for fires immediately following the LNG spill on land. (SeeFigure 12.)

A second important consideration is the presence of obstruc-tions in the spill area. Like pressure/pool fires, two alternativesare available: Use of dry chemical from sufficient applicationpoints to preclude the possibility of shielded flames; or use ofhigh 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 vaporconcentration reduction may be desirable under certain conditionsThe application of high expansion foam can accomplish this aspreviously stated. Specific reference to its use is found on Page

14.


10/29

THE EXPERIMENTAL EXPERIENCEPage 8

THE EXPERIMENTAL EXPERIENCE

The basis for ANSULs concept and design recommendations is adirect result of five major testing programs involving the controland extinguishment of natural gas and LNG fires. The programsare illustrated in Figure 5.

Types of Agents

Site Date Tests Tests Tested___ ____ _____ _____ ______

Longview, 1951 91 Vapor-Non- SodiumTexas7 lmpinging Jet Bicarbonate

Vapor-HorizontalImpinging Jet

Vapor-DownwardImpinging Jet

Vapor-Split PipeImpinging Jet

Six Lakes, 1965 48 Vapor-Non- SodiumMichigan8 lmpinging Jet Bicarbonate

Vapor-Horizontal PotassiumImpinging Jet Bicarbonate

MonoammoniumPhosphate

Six Lakes, 1969 107 Vapor-Non- PotassiumMichigan9 lmpinging Jet Bicarbonate

PotassiumChloride

Marinette, 1972 43 LNG Pool Fires SodiumWisconsin10 Bicarbonate

PotassiumBicarbonate

High ExpansionFoam

MonoammoniumPhosphate

Norman, 1973 100 LNG Pool Fires SodiumOklahoma17 (Accelerated Bicarbonate

Boil-Off Rates) PotassiumBicarbonate

High ExpansionFoam

FIGURE 5

ANSUL Large Scale Natural Gas Fire Testing Programs

The 1951 Longview program established the technical informationfor the use of sodium bicarbonate base dry chemical on four vari-ations of gas pressure fires that are typically found in the naturalgas transmission industry.

The 1965 Six Lakes program was conducted to compare the effec-

tiveness of potassium bicarbonate, monoammonium phosphateand sodium bicarbonate base dry chemicals on two of the four gastransmission hazards tested in the Longview program. From thisexperimentation, definite design criteria for the potassium bicar-bonate base agent were developed for the two hazards tested,and correlations between the relative extinguishing effectivenessof sodium and potassium bicarbonate base agents produced thepotassium bicarbonate base agent design criteria for the other twohazards.

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 andpotassium chloride base dry chemicals.

The 1972 program, conducted at ANSULs Fire TechnologyCenter, 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 of400 (37.2 m2) and 1200 (111.5 m2) ft2 in area.

The 1973 tests, conducted at Norman, Oklahoma, determined thatfresh LNG spills with accelerated boil-off rates increased drychemical flow rates for extinguishment.


11/29

THE GENERAL BEHAVIOR OF EXTINGUISHING AGENTSPage 9

THE GENERAL BEHAVIOR OF EXTINGUISHING AGENTS

In situations other than total flooding, it is generally accepted thatif 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 acertain point, increasing the agents application rate will result in ashorter extinguishment time.

This extinguishing time and agent application rate relationship hasbeen 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

EXTINGUISHING

TIME

(t

sec)


12/29

THE GENERAL BEHAVIOR OF EXTINGUISHING AGENTSPage 10

THE GENERAL BEHAVIOR OF EXTINGUISHING AGENTS

(Continued)

Another illustration of this behavior is shown in Figure 7, where theagent quantity and agent application rate are plotted. In a numberof experimental programs, it has been determined that there is anoptimum 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 extinguishmenttimes and the expenditure of more agent than at Ropt.Furthermore, if the application rate is less than Rmin, an infinitequantity of agent would theoretically be unable to extinguish thesubject fire.

Rmin has been found to be in the range of 0.4 to 0.5 Ropt, whichaccounts for the 2.0 factor of safety usually put on Rminute toarrive at a design rate. If the agent is applied at a rate greater thanRopt, the time of extinguishment is usually not reduced to anysignificance (as shown in Figure 6) resulting essentially in thewasting of agent (Q >> Qminute).

003386

FIGURE 7General Relationship of Agent Rate and Quantity

AGENT APPLICATION RATE (R lb/sec (kg/sec))

Rminute

Qminute

AGENTQUAN

TITY

(Q

lb)

Ropt


13/29

THE SPECIFIC AGENT FLOW RATE REQUIREMENTS FOR NATURAL GAS FIRESPage 11

THE SPECIFIC AGENT FLOW RATE REQUIREMENTS FORNATURAL GAS FIRES

After all the experimental information was analyzed, recom-mended design criteria were developed for the application of theextinguishing 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 Shownabove, 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 drychemical streams are superior to soft or fan streams for theextinguishment of natural gas or LNG fires. Care should beexercised on LNG spill fires to avoid disrupting the liquidsurface of the fuel with the agent which would cause anincrease in the burning intensity.

B. All the design criteria for dry chemical on natural gas pressurefires employ a safety factor of two (2.0) on the minimum ratefound necessary to effect extinguishment in the experimentalprograms. When designing automatic fixed nozzle dry chemi-

cal systems, the applied safety factors would be increasedsubstantially to achieve much higher application rate densities(Ib/sec/ft2). The minimum design rate for LNG spills in Figure11 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 shouldbe selected to produce optimized discharge times according toapplication conditions.

D. From NFPA 11 Standard for Low-, Medium-, and High-Expansion Foam3: In (testing), control was established withexpansion ratios greater than 250:1, although an expansionratio of about 500:1 proved most effective.

E. The design rate selected for high expansion foam musproduce fire control with at least 90% reduction of the radiantheat flux under the conditions described in Figure 15. It isgenerally accepted that a minimum application rate of 6 ft3 pe

minute per ft2 (1.8288 m3 per minute per m2) is desirable asdetermined by testing. Under some circumstances fastecontrol times may be essential, or longer control times accept-able. The entire foam application rate/fire control time relationship has been included in Figure 15.

F. In the combined use of high expansion foam and dry chemicals, the high expansion foam application must be continueduntil the dry chemical has completely extinguished all flames.

For the graphs in Figures 8 through 15, the criteria shown in solidlines are based on actual experimentation and those shown indashed lines are correlations (based on relative extinguishingeffectiveness of the agents) or extrapolations. The design infor-mation on LNG pressure fires are theoretical and it assumes thathe LNG completely and immediately flashes to a vapor at 70 F(21 C). upon exiting the failure point. The dry chemical rates arethen based on the free volume of natural gas using an expansionfactor of 600. This approach is justified on the basis of reportedcorrelations attained in experimentation with gaseous and liquidpropane.14


14/29

THE ANSUL RECOMMENDED AGENT QUANTITY REQUIREMENTSPage 12

RECOMMENDED DRY CHEMICAL DESIGN APPLICATIONRATES FOR NON-IMPINGING NATURAL GAS AND LNGPRESSURE FIRES (2.0 SAFETY FACTOR APPLIED)

FIGURE 8003387

(Based on data fromReferences 7, 8 and 9.)LNG agent requirementsare theoretical and assumethat the LNG completelyvaporizes upon contact withthe air and immediatelyexpands to its 70 F(21.1 C) condition (600times expansion).

PLUS

-FIFT

Y

DryChemicalDesig

nApplicationRatelb/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)

Purpl

e-K


15/29


RECOMMENDED DRY CHEMICAL DESIGN APPLICATIONRATES FOR HORIZONTAL IMPINGING NATURAL GAS ANDLNG PRESSURE FIRES (2.0 SAFETY FACTOR APPLIED)

FIGURE 9003388

(Based on data fromReferences 7, 8 and 9.)Dashed lines indicateextrapolations or correla-tions: LNG agent require-ments are theoretical andassume that the LNGcompletely vaporizes uponcontact with the air andimmediately expands to its70 F (21.1 C) condition(600 times expansion).

PLUS

-FIFTY

DryChemicalDesig


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)


Purpl

e-K


16/29


RECOMMENDED DRY CHEMICAL DESIGN APPLICATIONRATES FOR DOWNWARD IMPINGING SPLIT PIPE NATURALGAS AND LNG PRESSURE FIRES (2.0 SAFETY FACTORAPPLIED)

FIGURE 10003389

(Based on data fromReferences 7, 8 and 9.)Dashed lines indicateextrapolations or correla-tions: LNG agent require-ments are theoretical andassume that the LNGcompletely vaporizes uponcontact with the air andimmediately expands to its70 F (21.1 C) condition(600 times expansion).

PLUS

-FIFTY

DryChemicalDesig


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)


Purpl

e-K


17/29


DRY CHEMICAL APPLICATION RATE VS. EXTINGUISHMENTTIME FOR LNG SPILL FIRES WITH BURNING RATE OF0.5 IN./MINUTE (1.27 cm/minute)

Based on data from Reference 10. Design Application Rate isBased 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 11003390


18/29


RECOMMENDED DRY CHEMICAL DESIGN APPLICATIONDENSITIES FOR A RANGE OF LNG POOL BURNING RATES(2.0 SAFETY FACTOR APPLIED)

FIGURE 12003391

PLUS

-FIFTY

0.5 1.0 1.5(1.27) (2.5) (3.81)

LNG Linear Burning Rate in./minute (cm/minute)

Purp

le-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


19/29


RECOMMENDED DRY CHEMICAL DESIGN APPLICATIONRATES FOR LNG POOLS BURNING AT 0.5 IN./MINUTE(1.27 cm/minute) (2.0 SAFETY FACTOR APPLIED)

FIGURE 13003392

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)

DryChemicalDesignApplicationRatelb/sec(kg/sec)


20/29


RECOMMENDED DRY CHEMICAL DESIGN APPLICATION RATESFOR 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)

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)

DryChemicalDesignApplicationRatelb/sec(kg/sec)

FIGURE 14003393

PLUS-FIFTY

Purple

-K


21/29


EFFECT OF FOAM APPLICATION RATE ON CONTROL TIMEFOR LNG SPILL FIRE USING 500:1 HIGH EXPANSION FOAM

If LNG pools are burning, the common practice is to provide foamdischarge for 3 times the average response time for fire fightingpersonnel to arrive on site and extinguish the fire with dry chemi-cal. In the absence of this information, it has been generallyaccepted for the purpose of design that a minimum 60 minutecontinuous foam discharge is adequate for foam concentratestorage tank sizing. ANSUL recommends continuous foamdischarge 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 dischargeas required is recommended to maximize available foam concen-trate supplies. After initial foam coverage based on 3 minutes ofdischarge, it is possible that reapplications may only be requiredevery 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) foamdepth over the spill area of non-burning LNG, the evaporation ratemay 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 foamdrainage. Evaporation rates of continuously foamed LNG that isburning may be in a range above 0.075 in. (0.191 cm) per minuteThe evaporation data listed above is based on JET-X Agent andHardware testing conducted at ANSULs R&D facility in a cemencontainment pit using LNG that was above 99% Methane.

Fire Control is defined as when the radiant heat fluxhas been reduced by 90 percent or more.

FireCon

trolTimeSeconds

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 15003394


22/29


RECOMMENDED DRY CHEMICAL DESIGN QUANTITIES FORNON-IMPINGING NATURAL GAS AND LNG PRESSURE FIRES

FIGURE 16003395

(Based on RecommendedApplication Rates and30 Seconds EffectiveDischarge Time)

PLU

S-FIF

TY

DryChemicalDesignQuantitieslb(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)


Pur

ple-K


23/29


RECOMMENDED DRY CHEMICAL DESIGN QUANTITIES FORHORIZONTAL IMPINGING NATURAL GAS AND LNGPRESSURE FIRES

FIGURE 17003396


PLU

S-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


24/29


RECOMMENDED DRY CHEMICAL DESIGN QUANTITIES FORDOWNWARD IMPINGING SPLIT PIPE NATURAL GAS ANDLNG PRESSURE FIRES

FIGURE 18003397


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)


Pur

ple-K


25/29


RECOMMENDED DRY CHEMICAL DESIGN QUANTITIES FORLNG 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)

LNG Area ft2 (m2)

10000(4536)

1000(453.6)

100(45.4)

10 (4.5)

DryChemicalDesignQuantitylb/kg

FIGURE 19003398

PLU

S-FIFT

Y

Purple-K


26/29


RECOMMENDED DRY CHEMICAL DESIGN QUANTITIES FORLNG 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)

LNG Area ft2 (m2)

10000(4536)

1000(453.6)

100(45.4)

10 (4.5)

DryChemicalDesignQuantitylb(kg)

FIGURE 20003399

PLU

S-FIFT

Y

Purple-K


27/29

COMMERCIALLY AVAILABLE FIRE SUPPRESSION EQUIPMENTPage 25

COMMERCIALLY AVAILABLE FIRE SUPPRESSIONEQUIPMENT

A. High Expansion Foam: Foam expansion rates of 500:1 arefavored for fire control and are well-suited for vapor dispersion.ANSUL recommends the following high expansion foamgenerators for LNG with performance characteristics as

shown.Calculating Foam Quantity For Local Application (LNG)High Expansion Generators Typical Discharge Characteristics

Generator InletPressure Foam Output Solution Flow

Generator psi (bar) cfm (cmm) gpm (lpm) Expansion________ ____________ ____________ ____________ _________

JET-X-2A 50 (3.45) 2,240 (63) 35 (132.5) 465:175 (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) 525:175 (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) 504:175 (5.17) 21,145 (599) 294 (1112.9) 538:1100 (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 gasand flammable liquid applications. Figure 21 summarizes theANSUL 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/secSystems 1500, 2000, 3000 lb (2-4.5 kg/sec)

(68, 158.8, 226.8, 453.6, for hand lines680.4, 907.2, 1360.8 kg)

Vehicle Mounted Purple-K 125, 300, 450, 900, 1350, 25-100 Ib/sec1800, 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 providedetailed coverage of the detection and control aspects of firecontrol and extinguishment. However, it should be recognizedthat whether automatic or manual, the detection controlsystem design is integral to the extinguishing system design, ifan optimum total system control and extinguishing capability isto be realized.


28/29

BIBLIOGRAPHYPage 26

BIBLIOGRAPHY

1. National Fire Protection Association, Storage and Handling ofLiquefied Natural Gas (LNG), NFPA Standard 59A.

2. Walls, W. L., LNG: A Fire Service Appraisal, FIREJOURNAL, 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, AnsulIncorporated, Marinette, Wisconsin.

8. Fire Tests With Natural Gas Jets Six Lakes, AnsulIncorporated, Marinette, Wisconsin.

9. Fire Tests With Natural Gas Jets Six Lakes, AnsulIncorporated, Marinette, Wisconsin (1969).

10. LNG Fire Control, Fire Extinguishment and Vapor DispersionTests, University Engineers, 1972.

11. REMOVED

12. Guise, A. B., and Lindlof, J. A., A Dry Chemical ExtinguishingSystem, 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 VaporDispersion and Fire Hazards Immediately Following LNGSpills On Land, For AGA by University Engineers, February,

1974.


29/29

-75158-2

Copyright

2007

AnsulIncorporated

ANSUL INCORPORATED

MARINETTE, WI 54143-2542

715-735-7411

Documents

ANSUL_Fire Protection Solutions for LNG