This report has been prepared v

for information ?

n

:i record

purposes an: is not to be referenced

in any pub/icat/oa.

NATIONAL BUREAU OF STANDARDS REPORT

^326

MOTORBOAT FIRE EXTINGUISHER EVALUATION

by

To Go Lee

Ho Shoub

Jo Mo Cameron

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards is suggested in the following listing

of the divisions and sections engaged in technical work. In general, each section is engaged in

specialized research, development, and engineering in the field indicated by its title. A brief

description of the activities, and of the resultant reports and publications, appears on the inside

of the back cover of this report.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instru- ments. Magnetic Measurements. Process Technology. Engineering Electronics. Electronic

Instrumentation. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

Technology. Length. Engineering Metrology.

Heat and Power. Temperature Measurements. Thermodynamics. Cryogenic Physics.

Engines and Lubrication. Engine Fuels.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid

State Physics. Electron Physics. Atomic Physics. Nuclear Physics. Radioactivity. X-rays. Betatron. Nucleonic Instrumentation. Radiological Equipment. AEC Radiation Instruments. Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics.

Mass and Scale. Capacity, Density, and Fluid Meters. Combustion Controls.

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Organic Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Mineral Products. Porcelain and Pottery. Glass. Refractories. Enameled Metals. Concreting Materials. Constitution and Microstructure.

Building Technology. Structural Engineering. Fire Protection. Heating and Air Conditioning. Floor, Roof, and Wall Coverings. Codes and Specifications.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics.

Data Processing Systems. Components and Techniques. Digital Circuitry. Digital Systems.

Analogue Systems.

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials.

Gas Liquefaction.

Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular

Propagation Services.

Radio Propagation Engineering. Frequency Utilization Research. Tropospheric Propagation

Research.

Radio Standards. High Frequency Standards. Microwave Standards. • Office of Basic Instrumentation • Office of Weights and Measures
NATIONAL BUREAU OF STANDARDS REPORT

HBS PROJECT NBS REPORT

1002-20-4825 September 22, 1955 4326

MOTORBOAT FIRE EXTINGUISHER EVALUATION

by

T. G 0 Lee

H. Shoub

Jo Mo Cameron

Fire Protection Section

Building Technology Division

for

Department of the Treasury

Uo So Coast Guard

Requisition No . CG31626-B

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

The publication

unless permissl 25.D.C, Such

cal ly prepared

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 201 5.

e or In part, is prohibited

>f Standards, Washington

a report has been specifiar report for its own use,

MOTORBOAT FIRE EXTINGUISHER EVALUATION

ABSTRACT

A study has been made of the relative effectiveness

of fifteen different small hand-portable fire extinguishers

considered suitable for application to flammable liquids

The evaluation was based on the performance of the extinguishers using five different extinguishing agents on ten

fires o These fires were selected either because they were

standard extinguisher tests or simulation of possible conditions of hazards on small motorboats » Statistical methods

have been used for evaluation of the relative merit of the

fires for extinguisher testing, the effect of ambient variables on the tests, and the* value of the several extinguisher types for use on the fires*

I* INTRODUCTION

The program of tests described in this report was initiated to establish the relative extinguishing efficiency

of certain small fire extinguishers, all but one of which

are of a size and type allowed by the Coast Guard for use

on motorboats, and to determine if the test fires by which

these extinguishers are evaluated are adequate and impar - tially discriminating

The present motorboat regulations, promulgated in 1941,

provide that the smallest allowable extinguishers are to be

the 1-qt carbon tetrachloride, 4-lb carbon dioxide and 1 ^-

gal foam sizes* With the development of small dry chemical

extinguishers, a 4-lb minimum was established for that type

also *

2

Generally, the Coast Guard's minimum size rule has

remained unchallenged except that a manufacturer of carbon

dioxide equipment has claimed that the 2-lb (with subsequent manufacturing change, 2-g— lb) CO2 extinguisher was

at least the equal of the 1-qt pump gun carbon tetrachloride

device (1),* In several tests conducted both by the Coast

Guard and the National Bureau of Standards the results were

inconclusive, but with some indication that the small CO^

device was as effective as the minimum carbon tetrachloride

pump gun. Further, neither of the extinguishers appeared

to be adequate to cope with the problem of fires of a size

and configuration possibly occurring on small motorcraft.

In an attempt to better evaluate fire extinguisher

effectiveness, the Coast Guard devised and constructed

several fire set ups which simulated the geometrical configuration of a small motorboat engine compartment , a bilge space, and a galley stove facility o These models,

together with several test fires used by commercial testing agencies and the National Bureau of Standards, were

used by the Coast Guard in a preliminary examination of

a number of small extinguishers suitable for use on flammable liquids o The results of these tests were inconclusive, but suggested that a more complete investigation of

the problem was necessary, and indicated that certain

modifications of equipment would be to advantage (2),

Since early in 195% the National Bureau of Standards has

continued the investigation of the problem., The proposal

for further tests of fifteen extinguishers on ten different fires, made in an NBS preliminary report ( 3)5 was

agreed to by the Coast Guard., The work on these tests

together with results and conclusions, is the subject of

this report.

2 o DESCRIPTION OF TEST EXTINGUISHERS AND AGENTS

The fifteen extinguishers chosen for the purposes of

these tests were all of readily obtainable commercial makes.

Each carried the Underwriters' Laboratories B-2 rating.

* No. in parenthesis refers to reference on page 28.

- 3

-

All were new, or late models in like-new working conditions

Including devices using all types of extinguishing agents

commonly available, they were chosen to determine the effect

on extinguishment of the agent, capacity, discharge rate,

duration and range of discharge, and continuous or intermittent discharge patterns

With three exceptions, two extinguishers of each brand

were used in the test program* Used alternately, this

served to facilitate charging procedure and tended to reduce wears However, the extinguishers were examined and

the discharge performance noted at the end of the program*

In no case was there evidence of wear or damage sufficient

to affect the operating efficiency in any way* Table 1

lists the extinguishers used in the tests* The devices

are also shown in figure 1 *

The extinguishers were charged with standard materials

which, where applicable, met the requirements of Federal

Specif ications * Carbon tetrachloride, Federal Supply

Service stock, Specification O-F38OA, was used in both

pump gun and stored pressure vaporizing liquid extinguishers* This was the product of three different manufacturers, and was supplied as Type I regular and Type II colored* The single chlorobromome thane extinguisher was charged

with material stated to meet the requirements of U. S. Air

Force Specification No. l4l63« The liquids were procured

in small containers so that generally each filling of an

extinguisher was from a previously unopened can.

The dry chemical used in three extinguishers was recently received and had the free flowing property charac - teristic of this material* Although tests have shown that

the powders may be used interchangeably, in this program

dry chemical manufactured for the particular extinguisher

was used in each case*

Carbon dioxide extinguishers were filled from 50-lb

commercial cylinders by means of a standard CO 2 liquid

type pump. In order to minimize the intake of moisture

into the extinguisher, which might adversely affect the

charge in dry chemical devices or deteriorate the working

parts of vaporizing liquid models, oil-pumped nitrogen was

used as the propelling gas in stored pressure extinguishers.

To secure correct and consistent pressurization, charging

was done with a reducing valve having a calibrated gage,

and at an ambient temperature of approximately 70°F. For

the one extinguisher depending on a carbon dioxide cartridge as a propelling medium, charges were secured from

and refilled by the extinguisher manufacturer.

The 1^-gal foam extinguisher was charged with chemical

procured from a manufacturer of foam materials . This

charge, tested in extinguishers of several brands, had been

found to give consistently good performance which was in

full compliance with all applicable requirements. By preparing a charge for a 2-g—gal extinguisher and dividing it

for the two samples, it was possible to provide uniform,

waste-free filling of the devices.

In charging, instructions on the extinguisher label

or charge were closely followed. In most cases, charges

were established on a weight basis with a tolerance of

0.05 lb. However, in order to provide a space of constant

volume for the gas in stored pressure carbon tetrachloride

and dry chemical extinguishers, in which the propelling

gas and extinguishing charge occupy the same chamber, the

charge weight in these devices was regulated to 0.01 lb.

Operating pressures were in all cases maintained constant,

and at the manufacturers stated value.

The fifteen test extinguishers may be classified into

four groups according to the type of agent employed. Of

eight extinguishers in the vaporizing liquid group, all

but one, a chlorobromomethane model, were charged with

carbon tetrachloride. Four hand pump CClq extinguishers

were used, two each of l~qt and l-g--qt capacities, which

pairs were further subdivided into liquid-pump and airpump types. The discharge of the two liquid-pump extinguishers was marked by a slightly intermittent action.

The other thirteen extinguishers of the test were characterized by a continuous type discharge, whatever their

propelling means. The two liquid-pump carbon tetrachloride were also the only devices in which the discharge

rate was entirely under the control of the operator, with

average observed rates of 0.055 lb/sec (0.048 min and

0.071 max) for the 1-qt size, and 0.088 lb/sec (0.077 min

and 0.101 max) for the l-g-~qt. The values shown were

obtained as averages over the total discharge time of an

extinguisher during the tests. Variations in discharge

rates for a* single device may be attributed to differences in operator strength and also to time loss occasioned by the operator's maneuvering to adopt the most

effective position for the particular fire configuration.

Air-pump extinguishers had average discharge rates of

0.056 and 0.04-7 lb/sec for the 1-and l-§--qt sizes, respectively. The low rate for the larger device was apparently inherent in the design as examination showed there was

no clogging of the passages. The remaining three carbon

tetrachloride extinguishers, of 1-,1-g-- and 2-qt capacities \ as well as the 1-qt chlorobromomethane device were of the

stored pressure type, which shows consistent discharge rates

and characteristics.
_

»

' 4

,
- 5

-

The carbon dioxide type extinguishers were of 2-J-— 5—

and 10-lb capacities * The gas pressure in a fully charged

extinguisher of any size is approximately 850 lb/in2 at

70° Fo From 75 to 80 percent of the discharge is in a form

effective for extinguishing fires*

Two of the three extinguishers in the dry chemical

group were of the stored pressure type, a 5-lb device

operating at 150 lb/in2 and a 4-lb model at 350 lb/in2 . The gas -cartridge extinguisher, of 4-lb capacity, develops

a maximum pressure of approximately 200 lb when operated*

The single extinguisher of the foam type, li-gal

capacity, is the only device of the fifteen tested that is

rated for use on class A fires as well as class B* However, it is not suitable for class C fires, a type for

which the other fourteen extinguishers of the program are

acceptable* The foam extinguisher is also the only one

in which the discharge, once initiated, could not be terminated before total exhaustion*

Discharge rate curves, determined empirically, for

extinguishers at approximately 70° F are shown in figure 3»

Rates for hand-pump carbon tetrachloride extinguishers are

not given, but the overall rate of 1-qt in 50 sec, required

in Federal Specification O-F-351? is included,, While the

observed discharge rates of the hand-pump extinguishers

averaged less than that specified, the rate for all but the

last 25 percent of the discharge was usually at least as

great as that required*

3* DESCRIPTION OF TEST METHODS

As previously stated, the Coast Guard had devised certain

test fires in its preliminary examination of the problem of

determining the effectiveness of extinguishers for motorboat

use* With modifications to improve the consistency of

results and eliminate variables where possible, these fires

formed the basis for the test program, conducted at the

National Bureau of Standards*

The fire models comprised three that have been used as

standard tests of small extinguishers for flammable liquid

fires* These were the 4- ft square spill area, the cotton

waste fire, and the nominal 2 -ft tub* Four fires were made in a compartment simulating with various degrees and_modes of

opening the engine space of a small motorcraft* In addition,

three fires considered to be types of possible hazard, open

bilge, alcohol spill from galley stove, and leak from a damaged container were included in the test*
5

.
-6

Changes in engine compartment opening were effected through

removal in whole or part of the end plates and top. The design

of three of these fire models was such that the fuel consumption

rates were maintained approximately the same, about 18 ml/sec.

The components of the compartment model are shown in figure 2,

with the construction and dimensions of the parts in figures

4- and 5 ° Each of the test fires is shown pictorially and in diagram

together with all pertinent data on the following ten pages.

As proposed in the NBS Preliminary Report, the tests were

conducted with a commercial mixture of heptanes* stated to

be available indefinitely „ This fuel, having a narrow distillation range at approximately 200° F, while forming a

constituent of gasolines , was used in order to create reproducible conditions of fuel consumption throughout the test

program as well as to provide fair burning equilibrium throughout the course of a single tria± 0 The properties of gasoline,

on the other hand, a.re known to fluctuate seasonally, and vary

with the producer and point of origin. Gasoline also,

because of its wide volatile range, exhibits marked

differences in characteristics during the burning of a

specimen, with rapid consumption of the more volatile portions

and ending in progressively slower burning of heavy fractions.

Although radiant energy measurements for gasolines (leaded

and unleaded) and the heptane mixture were approximately the

same, some duplicate tests were made with the two fuel types

at intervals throughout the program. In these there were no

appreciable differences noted in extinguisher performance

that could be attributed to the type of fuel used. The

distillation curves for the test fuel and the average of a number of gasolines are shown in figure 6 (4),

Although fuel consumption rates for other fire models

were determined from time to time during the program, those

for fires VI through X, using the bilge and engine

compartment, were established during each series of tests

to check the consistency of the test and also to learn what

effect, if any, changes in ambient conditions, ranging from

calm to moderately high winds and from 32° to 85°F, had on

the fuel consumption

In the final program -for extinguisher valuation, a test of each of the fifteen extinguishers on the ten fires,

defined as a series, was repeated five times „ This was

done to provide sufficient data for a significant statistical

analysis of the results 0 The reliability of the interpretation from this number of trials is discussed in a further

section of this report»

*Skellysolve C, Skelly Oil Company, Kansas City, Missouri.
'
-7-

Fire Model I

Type: 4 ft x 4 ft fuel spill

Test Apparatus: Shown in sketch and picture

Fuel: 2£ qt in recessed area

Preburn Time: 5 seconds

Fuel Consumption Rate: About 40 ml/sec (estimated)

Attack: Begin application at windward edge of fire

RECESS DEEP,

MINIMUM SLAB

THICKNESS-4'

\

® ^ v/ ® AN*® 1 1

* ^ 4-0 X4-0 1 - 6 —

-c^ 7* n" y 7* n* >— f U A / U ^

- 8 -

Fire Model II

Type: Fuel saturated cotton waste - 2 ft x 4 ft area

Test Apparatus: 8 lb cotton waste as shown in picture and sketch

Fuel: 2 qt sprinkled over cotton waste

Preburn Time: 10 seconds

Wind Direction: Toward long edge

Attack: Begin application at center of windward long edge

2' -0"X 4'-0"ARE A OF COTTON WASTE

CENTERED IN 4-0u X 4-0" TEST AREA

;WASTE 5" TO 6"

DEEP

—

t -01, X4'-0

, 'TEST AREA >

111

“ 9

”

Fiye Model III

Type: Two-foot (nominal) tub

Test Apparatus: Tub as shown* Water to bring level

to 10£ in* below top of tub

Fuel: 2 qt poured on top of 1 gal water in tub

Preburn Time: 20 seconds

Fuel Consumption Rate: About 10*5 ml/sec

Attack: Begin application to windward of tub, against

opposite side wall.

24" I.D —

21" I.D.-—)J

14 GA. STEEL SIDES

AND BOTTOM

- 10- Fire Model IV

Type: Running, vertical and horizontal

Test Apparatus: 1-gal covered bucket, set on metal stand,

bucket flush with sides of stand in downwind corner, hole to direct stream upwind

Fuel: 3 qt poured in bucket

Flow Time: 10 seconds

Flow Rate: 14-10 ml/sec (from 0 to 60 sec)

Preburn Time: 20 seconds

Attack: Begin application to windward of spill

0.16! HOLE I FROM

BOTTOM OF BUCKET

BRACES(8)

6g I.D. X 7"X I4GA.

STEEL BUCKET

1 2" X 1 2"X 14 GA . TOP

j£x|’x|xi2"ANGLE LEGS (4)

4'-0"X4'-0''TEST AREA

¥

-11

Fire Model V

Type: Flowing, vertical surface

Test Apparatus : Shown in sketch and picture

Fuel: 1 gal. 95$ ethyl alcohol

Flow Time: 10 seconds

Preburn Time: 30 seconds

Wind Direction: Frontal

Flow Rate: Above 11.5 ml/sec

Attack: Apparatus facing upwind, operator to windward

- 12 -

Fire Model VI

Type: Bilge

Test Apparatus: Shown in picture and sketch* 1-in.

water in pan

Fuel: 1 gal on water in pan, and wood grating C (3 long 4 short)

Preburn Time: 60 seconds

Wind Direction: Toward long edge

Fuel Consumption Rate: 15*2+1 ml/sec

Attack: Begin application at center of windward long edge.

z

WOOD GRATING C

fx X

kl"

..BAFFLES (3)

I ^

HIGH 22"L0NG

(2” GAP AT ALTERNATE ENDS)

14 GA. STEEL PAN 4 X24 X48

INSIDE DIMENSIONS

-13-

Fire Model VII

Type of Fire: Compartment (empty)

Test Apparatus: As shown in picture & sketch; 1-in. water in pan

Fuel: 1 gal on water, and wood grating A (4 long and 4 short)

Preburn Time: 60 seconds

Fuel Consumption Rate: 11.8+1 ml/sec

Method of Attack: Through open top, at operator's discretion

—26^X48^ CLEAR OPENING

’*"-14 GA. STEEL

ENGINE COMPARTMENT

30"X30'

, X50" (INSIDE)

WOOD GRATING "A"X

\STEEL PAN

Fire Model VIII

Type: Engine Compartment (top and two lower ends opened)

Test Apparatus: Shown in picture and sketch; 1-in* water in pan

Fuel: 1 gal on water, and wood grating B (3 long 3 short)

Preburn Time: 60 seconds

Wind Direction: Either opened end

Fuel Consumption Rate: 17*8+.7 ml/sec

Attack: Discharge agent into windward lower opened end and then

from top of compartment

26^ X48^CLEAR OPENING

H

-15-

Fire Model IX

Type: Engine Compartment (top and one end opened)

Test Apparatus: Shown in picture and sketch; 1-in. water in pan

Fuel: 1 gal on water, and wood grating C (3 long 4 short)

Preburn Times 60 seconds

Wind Direction: Opened end

Fuel Consumption Rate: 192± , 7 ml/sec

Attacks Discharge agent into opened end, follow through and aim

into top of compartment

— 26-g X48g CLEAR OPENING-*-

-16-

Fire Model X

Type: Engine Compartment (one end opened)

Test Apparatus: Shown in pictures and sketch; 1-in. water in pan

Fuel: 1-gal on water, and wood grating D(2 long and 2 short)

Preburn Time: 60 seconds

Wind Direction: Opened end

Fuel Consumption Rate: 18.0+1.2 ml/sec

Attack: Application through open end

26^ X4"0PENING-j [«-

~1

1 TJ

1 ~ j

L. / L

7

WOOD GRATING “O' PAN

17-

The schedules used for the series are shown below (numbers

refer to extinguishers, Table 1)„ The same schedule was used

for all ten fires in a given series

Schedule for

Series 1 Series 2 Series 3 Series 4 Series 5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

4 11 14 3 8 13 2 10 15 1 5 9 6 7 12

5 7 15 9 10 14 3 4 12 2 6 13 1 8 11

6 8 10 1 12 15 5 11 13 3 7 14 2 4 9

9 12 13 2 7 li l 6 14 4 8 15 3 5 10

It will be noted that any schedule has the property that each

day's operation or run is divided into five time periods of

three extinguishers eacho In the course of the program, all 15

extinguishers were used in each of the time periods

The experiment was programmed so that the intercomparison

between extinguishers would not be affected by differences in

weather conditions or other factors changing with timeo This

was done by arranging the sets of three extinguishers in a balanced way so that an interlocking chain of comparisons could

be made among all extinguishers „ As a by-product of this

experimental arrangement it was possible to determine any

variability between the time periods, all five of which were

covered in one day’s operation by one particular operator

For the actual experimental work, two operators were

employed o The program was arranged so that an operator would

handle alternate fire models during a series 0 Thus by the

end of the scheduled tests, each operator would have used a particular extinguisher on a given fire model at least twice

Comparatively experienced operators were used to minimize

learning effect on the results * However, as it was impossible

to provide operators thoroughly familiar with the specialized

test fires used, a small effect of this kind was inevitable e This is seen in an analysis of the results of the first two

series of fires „ In attacking the fires, the operators

approached as closely as possible, using a glove where

necessary, or as near as required for the apparent optimum

use of the extinguisher s » On fire No„ 7 the physical limitation

of approach may have been a factor in reducing the effectiveness of some extinguishers o In three cases of unmistakable

mishap to the operator during the tests, reruns were made

immediately

The extent of the data recorded during a test is shown

in a typical sheet, figure 7° Extinguisher temperatures were

maintained as nearly as possible at 70° F by conditioning in a

special cabinet prior to use 0 Wind velocities, measured with

an anemometer mounted approximately 4 ft above ground level,

Were the average over the time between ignition of the fuel

and final extinguishment or exhaustion of the extinguisher

charge o Extinguisher performance was rated on a basis of six

~19

5o DISCUSSION OF RESULTS

In considering the 9*+ groups of wholly consistent results,

either extinguishment or failure in all five trials of a device on a particular fire, it may be assumed that the

performance effectiveness of these extinguishers was such

that variation in weather conditions and operator skill

during any of the five runs was not sufficiently great as to

change' the outcome , However, the relative success or failure

scorings within a group were affected by these variables

Some extinguishers were almost uniformly successful

in fighting fires, while others were equally consistent

in noneffectiveness o Also, an extinguisher may be successful

against a hazard such as fire model III on every trial, and

fail all five times to extinguish fire VIII, a more severe

type o The performance of the extinguisher on an intermediate

type fire should be neither all success nor all failure , It

will be successful under the right combination of environmental conditions and operator technique, and even a minor

deviation from these conditions may lead to failure® If

against a particular fire an extinguisher may have only 10

percent success, these successes are achieved only under a very restrictive set of conditions. Another extinguisher

may achieve 80 percent success, being less sensitive to minor

deviations from optimum operating conditions. In these

tests, the 5-lb carbon dioxide extinguisher, which had the

greatest number of nonuniform group results, appears to be

an example of a high sensitivity type device.

The performance of an extinguisher can be described in

terms of its percentage success against a given fire. To

establish this value to the nearest percent would take an

inordinate number of tests. If an additional five tests are

made when two or three successes are observed in the initial

five trials, the combined results will still only show about

equal numbers of successes and failures if the extinguisher

has a long run success probability of 50 percent.

These uncertainties point up a difficulty in relying

solely on the record of successes or failures. In the

first place, there is no weight given to the ease with which

the fire .is extinguished. And secondly, it ignores completely

valuable Information that can be gained from the evaluation

by an experienced operator. It is quite clear that the

Inadequacy of a completely ineffective extinguisher on a particular fire can be determined from, a single trial. By

assigning a score to each trial, an attempt is made to

recover some otherwise lost information.

Fire model III was found to be the least difficult of the

ten to extinguish, with only some carbon -tetrachloride

pump-guns failing (Nos,l, 2, and 6), For many years this

fire was considered a standard test for evaluating small

- 20

extinguishers of this type 0 However, our negative results

have been corroborated by other investigators . Coast Guard

tests (2) showed only 50 percent success using 1- and l-§--qt

devices, with extinguishment in no case occurring in less

than 42 sec. Another test with 1 -qt pump guns showed complete

failure in all of nine trials ( 5 ) on the 2 -ft tube The

results indicate that to have any effectiveness at all on

this fire, carbon tetrachloride extinguishers must have a high rate of discharge.

Where the fuel is fed to the fire through a small opening,

as in fire No. 4-, extinction can sometimes be accomplished

with a carbon tetrachloride extinguisher by directing the

stream of vaporizing liquid directly at the source, thus

diluting the fuel to a point it no longer sustains combustion.

The comparative results of carbon tetrachloride performance on fire models VI and VII indicate that these

extinguishers are sensitive to model configuration, more so

for example than are the carbon dioxide extinguishers, as

shown in the following table of total scores for five runs.

Extinguisher

Capacity

No.

CCli,

li-qt 2-qt

7 8

co 2

2i-qt 5 -lb 10-lb

9 10 11

Fire Model

VI

VII

-7 -4

12 8

-3 9 19

-3 9 15

The poorer performance of carbon tetrachloride extinguishers

on fire VI than on VII may be attributed to lack of confining

surfaces on the bilge fire. Thus there is a reduction in the

volume of vapors formed as there are no hot surfaces to cause

vaporization, and no means of preventing the quick dissipation

of the volatile products. As can be seen from the table,

there were no significant differences in the performance of

carbon dioxide extinguishers on the two fires. The better

confinement offered by model VII was probably offset by the

possibility of close approach to fire VI when using carbon

dioxide extinguishers.

In fire models VIII, IX and X, where the fuel consumption

rates throughout the program were approximately equal

( 18 , 5+1.4 ml/sec), confinement was apparently the primary

factor affecting extinguisher performance. The following

table, giving the total rating for 5 runs of several extinguishers shows there was markedly better performance on those

fire models with highly confined configurations, which tended

to accumulate the agent to a concentration level necessary for

extinguishment

-21 -

Extinguisher

Capacity

No®

CBM

1-qt

b

CCI4

li-qt

7

2-qt

8

2i-lb

9

co 2

5-lb

10

10-lb

11

Dry Chem®

5-lb

lb

Fire Model

VIII 0 -10 -10 -IV -2 10 0

IX 9 -2 -2 2 11 8

X 14 10 12 5 5 13 lb

It is seen from the scores that the vaporizing liquid and some

dry chemical types were more sensitive to differences in these

fires than were the carbon dioxide extinguisher s

Accumulation of vaporizing agent, however, may not be

the only explanation for this apparent correlation between

degree of confinement of fire models and effectiveness of

extinguishment® Another possible factor may well be the

relation of the agent to the flammable limits of the fuel,

which for heptane range from 0 o 8 to 7 percent® Although

the fuel consumption rates for the three fires were about

equal, the fires were not necessarily burning at the same

fuel/oxygen ratio® Thus in some fires, for example No® X,

the model configuration is such that air diffusion is restricted,

especially as compared with No® VIII, with the apparent result

that the fuel mixture was considerably richer than in other

fires® On the basis of flammability limit tests, it has been

suggested that the volume of vaporizing liquids required for

such a fire is much less than that for fires having a lean

mixture, to the enhancement of extinguisher efficiency on

some enclosed hazards (6)®

In conducting the tests, it was found that optimum

methods of attack varied with the fire models and particularly with the extinguishers® Generally, carbon tetrachloride

was oest employed by spraying on a hot surface, preferably

metallic for maximum vaporization, and in such manner as to

cover the area with the decomposition products® Dry

chemical extinguishers appeared most effective when operation was such as to cover the whole flaming area at once®

Carbon dioxide types seemed to work best when the agent was

discharged near the fuel surface so that the heavy gas

apparently displaced the oxygen to a point below the

combustible limit® The use of foam, effective only if flowed

onto the burning liquid surface, was made difficult by

obstructions such as floor boards, engine block or compartment

walls® To secure results that would be impartial and

unprejudiced, the operators in every case endeavored to use

an extinguisher to its maximum effectiveness® That this

occurred is borne out by the increase in scores in the second

run over those of the first® The learning that occurred initially

was applied to the advantage of the extinguishers in all the

subsequent trials® Generally, the method of attack was

standardized early in the program and thereafter maintained

throughout the tests®
' $

,* . - '
-22 -

60 ANALYSIS OF RESULTS

6ol Analysis of Data on Scores

Table 2 gives the sums of the scores obtained on each of

the five separate trials on the different test fires 0 The data

for each fire were analyzed to determine whether any statistically significant differences were introduced into the results

because of the day-to-day variation in the environmental

conditions,. Fires VI, VII, VIII, and X do show statistically

significant variation from day to day. However, for almost

all fires there is a marked increase in the scores on the last

4 series when compared to the scores on the first series . The

statistically significant day-to-day variation for fires VII,

VIII, and X is due almost entirely to the increase in scores

from the first to the subsequent series. These fires have a wood grating or other obstruction to limit the operators

access to the fire. The improvement in scores in the later

series is undoubtedly due to the improvement in technique

evolved by the operators as the tests were repeated.

6.2 Analysis of Data on Number of Successes

Tables 3 and 4 give a tabulation of the number of times

each extinguisher succeeded in putting out the ten test

fires o The order of listing is roughly that of relative

effectiveness of the device but is also determined by

extinguisher type. An inspection of the data of Table 3

suggests that Fire II is not representative of the same

type of fire as the other 9 fires. It will be noted that

Fire VIII has about the same low number of successes but it

nevertheless ranks the extinguishers in essentially the same

order as the remaining fires. Fire II gives a discordant

ranking and for this reason the statistical analysis has been

carried out omitting this fire.

This anomalous behavior of Fire II is confirmed by the

statistical analysis carried out in transformed units given

in Appendix A. With the omission of Fire II, the observed

variability of results can be regarded as being in accordance

with its theoretical expectation, whereas with the inclusion

of Fire II this is not so.

Table 4 shows the data tabulated to display the differences

between series. Each entry represents the number of successes

of a given extinguisher summed over all fires in a series.

A statistically significant effect shown by these data is the

fact that series 1 is lower than ' succeeding series. This is

shown in the analysis given in Appendix B.

-23-

6o 3 Ranking of Test Fires

It was pointed out above that Fire II appears to be a different type of fire than the other 9 and for this reason

it has been excluded from the comparison of fires©

The remaining 9 fires rank themselves in order of

severity (most difficult to put out has rank 1) as follows:

Fire

Percent of tim.es

fire put out in

75 attemnts Rank

Average scores

from

75 attemrts Rank

VIII 26,7 1 -1 © 05 1

IV 37-3 2 -0.53 2

VI 4-2 o 7 3 -0ol9 4

IX 44 c 0 4 -Oo45 3

VII 57.

5 0.43 5

V 66o 7 6 0° 79 7

I 69-3 7 0 © 68 6

X 70 o 7 8 0©86 • 8

III 82 o 6 9 1-97 9

From an inspection of these values, one is led to suggest

that for quick screening of extinguishers, Fire III could be

usedo An extinguisher that failed to put out Fire III is

certainly rather weak in relation to the performance of the

extinguishers used in this test© Fire III also requires the

least amount of equipment of all the fires© One could then

rate the extinguishers that pass the test of Fire III by

choosing an intermediate test, such as VII, and a difficult

test, such as Fire VIIIo

To sharpen the comparison of extinguishers, at least from

the point of view of statistical analysis, it would be

convenient to have a measure on a continuous scale, such as

the area of a given type fire that could be put out. Without

this, the alternative is to rate extinguishers on a scale

of several test fires in a sequence related to the severity of

fires encountered in practice » For this purpose, extinguishment could be defined as the capacity of a device to put out

a particular test fire four times in five trials, and further,

-24-

to achieve an average score as described in this report of

approximately +1 or greater , It is possible that requirements

should be set according to the severity of the hazard expected,

with consideration given to the establishment of the middle

grade of fire severity as that most likely to be encountered.

The other two test fires may then be reserved as representative

of cases either of very minor hazard or greater conditions

of severity. It should be remembered, however, that even

fire No, VIII does in no manner encompass the limit of possible

hazard on motorcraft, but rather defines the limit of extinguishing capacity of devices of a size considered in this

report

6,4- Ranking of the Extinguishers

The extinguishers have been grouped according to type,

and their performance and relative rankings based on several

methods of comparison are presented in Table 5° All methods

of performance measurement give essentially the same rankings.

The standard deviation of 4,7 of individual averages, column C

of Table 5? is not considered excessive. To reduce this

deviation by 50 percent would require making 15 additional

trials of each extinguisher on each fire.

As had been expected, a high rate of discharge in any

particular type of extinguisher enhanced the effectiveness of

the performance. This is shown in an examination of the results

of tests on hand pump and stored pressure type carbon

tetrachloride devices and also the 5-lb low pressure dry chemical

extinguisher as against the two higher pressure 4-lb models.

Of the 15 extinguishers tested, only 3 were capable

of meeting the requirements as herein established for the

most severe fire, model No, VIII, These were the 10-lb

carbon dioxide, the 4-lb cartridge operated dry chemical and

the 4-lb stored pressure dry chemical devices. The 1-qt

chlorobromome thane extinguisher narrowly misses the required

performance on Fire VIII, but because of high effectiveness

on the other fires, stands with the other three extinguishers

in a group showing the highest percentage of successes for

the whole program. The 5-lb dry chemical, 5-lb carbon

dioxide, and 1-g— and 2-qt stored pressure carbon tetrachloride

extinguishers are suitable for an intermediate fire such as

No, VII, Fire No, III could be successfully handled under

these standards by the I-?— gal foam extinguisher, the 2-g—lb

carbon dioxide, the 1-qt stored pressure carbon tetrachloride

and the 1-g— qt high-rate pump-gun carbon tetrachloride devices.

The two 1-qt and one of the 1-g—qt vaporizing liquid pump guns

were unsuited for use on even this minimum fire.

-25-

In considering ease of operation of the several types and

the possibility of their successful use by a novice, it is

necessary to remark that the 10-lb carbon dioxide extinguisher,

while highly effective, has a charge weight of 2-g- times that of

other devices in its effectiveness group and a total weight in

excess of three times that of the next heaviest,, This

extinguisher, also, has a relatively short discharge range,

forcing a close approach to the fire for effective use. Stored

pressure vaporizing liquid extinguishers may be operated at a distance, and this combined with the good performance of

chlorobromome thane makes that extinguisher a recommended type.

The dry chemical extinguishers are, however, the type most

likely to lend themselves to effective use as their moderateto-good range and high accomplishment for their size are

further augmented by the shielding effect which the powder

affords against radiant heat,

6,5 Influence of Ambient Conditions on the Results

The fire test program was conducted outdoors between

February and June under ambient conditions of the following

limits: wind velocity from 1,3 to 17° 5 mph, temperature,

32°F to 85°F, relative humiditv, 23 to 100 percent, and solar

radiant intensity from 0 to lob g cal/cm^ min. As mentioned

earlier, the burning rates of bilge and compartment type fire

models tended to increase with increase of wind speed and/or

temperature o However, the results based on scoring did not

show any apparent influence of any individual measured ambient

factor, with the exception of wind speed.

Analysis of the data indicates that wind speed, as a single variable, showed some statistically significant effect

on the scores of only a few fire models. The degree of wind

sensitivity depends more on fire model than on type of

extinguisher. Results of fire Model II, VI and IV were, in

the order given, adversely affected by increase in wind speed,

whereas Model VII seemed to be favorably influenced by this

condition. The rest of the models showed no significant

trend.

The following table shows the number of cases in which

the wind velocity increased or decreased in successive series

with a similar directional change in the scores on Fire Models

II, VI, IV and VII,

/
. ’
- 26

Fire Score increased iScore remained Score decreased

Model Wind from previous series the same from previous

series

II Increased 3 7 10

Decreased 10 9 1

VI Increased 8 8 11

Decreased 7 3 3

IV Increased 2 11 2

Decreased 11 10

VII Increased 10 8 V

Decreased 5 9 V

Total (above

)

56 65 39

Total for the program* 119 182 99

All

and

fires and all extinguishers except

foam extinguishers.

the four hand pump CCI4

.

The inequality between the number of cases of increase in

score and the number of decreases is a reflection of the increase

in proficiency of the operators between the first and second

or subsequent series. The great number of cases of scores

remaining the same indicates the relative reproducibility of the

scoring system used in this program.

7 o CONCLUSIONS

The following conclusions seem justified on the basis of

the work reported:

1. The tests performed indicate significant differences

between the effectiveness of hand pumped carbon tetrachloride

and carbon dioxide extinguisher types, the latter being

significantly more effective on the basis of equal weight of

extinguishing agent.

2. The 1-qt chlorobromome thane , 10-lb carbon dioxide, and

two ^-lb dry chemical extinguishers ranked very closely with

each other as useful devices for attack on the test fires.

- 27 -

3° The test fires used for the study presented a useful

scale for evaluation of extinguisher performance. From these

three fires have been selected to provide a qualitative means

for evaluation of performance of other devices intended for

use on hydrocarbon type flammable liquid fires.

The rather large variations in ambient conditions

observed during the tests did not affect extinguisher perform

ance enough to cause statistically significant differences

being observed in the results for most fire types used.

ACKNOWLEDGEMENT

The authors wish to acknowledge the valuable help and

suggestions given by A. F. Robertson, Chief, Fire Protection

Section, and the assistance of J. Loftus in performing the

tests

.
' i* '

•

'
-28

80 REFERENCES

1. Uo So Coast Guard, Research and Development Division,

Motorboat Fire Tests, 29 March 19^6.

2, Uo So Coast Guard, Testing and Development Division,

Motorboat Fire Tests, Project No. CGTD-lA-13-19 , August

1950°

3o Ho Shoub and To Go Lee, First Progress Report on Motorboat

Fire Extinguisher Evaluation, NBS Report 3823 , December

16 , 195

^

^o 0. Co Blade, Bureau of Mines, Depto Interior, National

Motor Gasoline Survey of Summer 195*+? Report of

Investigation 5111 , January 1955°

5= To Bo Edwards, Army Fire Extinguishment Research Program

for Field Operation, Proceedings Symposium on Fire

Extinguishment Research and Engineering, Uo S „ Naval

Civil Engineering Research and Evaluation Laboratory,

Port Hueneme , California ? November, 1954..

60 Eo Ho Coleman and Go Wo Stark, A Comparison of the

Extinguishing Efficiency of Bromochloromethane and Carbon

Tetrachloride, Chemistry and Industry, p. 563 , 1955°

-29-

APPENDIX A

In order to perform an analysis of variance on the data on

Table 3 of the report, the number of successes must be transformed to units in which the variability is essentially constant

This is accomplished by the arcsin transformation /See "The

Use of Transformations/ by Mo So Bartlett, Biometrics , Volo 3

(March 1949) pp» 39-52/, The technique of analysis of variance

is described in The Design and Analysis of Industrial

Experiments , edited by D, L, Davies, Oliver and Boyd, London,

19W.

Table A1

Analysis of variance of transformed data (Fire II included)

,

Source of variation Degrees Sum of Squares Mean Square

of

Freedom

Extinguishers 14-

Fire 9

Error 126

Total IW

53,719-16

20,363-19

30.521.74- 24-2,2 36

104,604,09

The theoretical value for the mean square for error is

821/n = 82V 5 - 164,2, To test whether the observed value

can be regarded as conforming to theory, we compute

F = 242,236/164,2 = 1,48 and compare this to the tabular

value for Fi 26 5 od 4 The value of the F-ratio turns out to

be significant at the 1 percent level, indicating the presence

of extraneous variation.

Inspection of the data suggests that Fire II, which gives

a discordant ranking of the extinguishers relative to the

other nine fires, is at fault. The analysis of variance was

then computed omitting Fire II,

Table A2

Analysis of variance

Source of variation

Extinguishers

Fires

of transformed data (Fire

d , f

o

Sum of squares

14 55 , 895-86

8 15 , 885-26

112 22 . 238,21

tvt 93,819.13

II omitted)

Mean square

Error 198, 56

Total

-30 -

The F-ratio for testing the agreement between observation

and theory with respect to the error mean square is

F = 198. 56/16402 = 1„21 which is less than the critical value

(5 percent level). Hence, one regards the variance stabilizing

transformation as being appropriate.

The standard deviation of the averages for an individual

extinguisher turns out to be 4. 7 and that of a difference

between two extinguishers averages, 6.6.

-31-

appendix B

Analysis of data on series and time periods within series.

The arcsin transformation was applied to the percent

successes for each extinguisher on 9 fires (omitting II), The

analysis given here is described in "Tables of partially

balanced designs with two associate classes", R. C. Bose,

Wo Eo Clatworthy, and S. S. Shrikhande, Tech, Bull, No. 107,

North Carolina Agriculture Experiment Station, August 195*+<> Source of variation

Extinguishers (unadjusted)

Sets of 3 (adjusted for ext.

)

series

order

residual

Error

Total

d.f

lb

2b

b

b

16

Sum of squares Mean square

3,445,558.74

175,3^5-88

100,675.41

12,022.88

62,647.59

389,419.72

4,010,324.35

7 , 306.08

25 , 168 . 85*

3,005.7^

3,915.47

10.8l7.12 a

*This is statistically significantly larger than error, and

series 1 is significantly lower than the other series.

aThe expected value of the error mean square is 9,122,22, The

observed value is in good agreement with its theoretical

expectation.

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Figure 1 Test Extinguishers

Figure 2 - Motor Compartment Components

TIME

,

SEC.

FIG.

3

APPROXIMATE

DISCHARGE

RATES

OF

TEST

EXTINGUISHERS

Figure 4

Engine Compartment and "Engine"

Both units made from 2-in. by 2-in. by 1/8-in. angle

and 14 ga steel plate fastened with 1/4-in. bolts

Engine compartment

made with bottom

open, long sides

covered, top and

end plates

removable

.

"Engine" covered

on all sides.

Figure 5

Wood Floor Gratings

Gratings are constructed of Ponderosa Pine, No. 2

common, nominal 1-in. by in. mill lumber (dressed

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Fire No. ^7 -

Extinguisher No., 3 A

Figure 7

- Typical Data Sheet

Motorboat Fire Test Data

Date S- 6'S V'Time

Manufacturer Sfop fir4. Extg Total wt 3 , 33T

Extg Temp IQ

WEATHER:

^Tuhn^) cloudy overcast

raun in/hr

Atm, Temperature ML

Wind Direction

(to apparatus)

Humidity 37 7,

Fuel / ff*/ Hzptc

Delay to ignition

Preburn

at\<z~

Time Fire Out

Time Extg Used

Final Wt #76

XFinal Pressure

Agent Expended

Wood initial wt

Wood final wt

&O

MS

Rating: -3 , -2 , -1 ; +1 , +3

REMARKS:

fiafeKtity easy

3 :oo

Extg type size L^L

Type of Charge QC Gas /Vx

Charge wt

Charge Pressure /TO

(JM) \rt% J

Test Area Shaded? o

Solar Radiation g cal/cm^min

Velocity rev/min //?^ MPH /<3~7

Barometer . x-9. ?o

Wet Bulb 6 ^

Temp of Fuel, water

Flow Time

. 77T„ .

Area of Fire Spread

,'LU

Vj Method of Attack fo Initial Position ± -ft.

Target /des Qf conj?Aff^\t^

Procedure Side fs S/ct(S

Final Position 3 ftOperator Recorder/^

Units: lb, sec ,°F,psi
.

'

.
>-UJ

FIG. 8

PERFORMANCE

RATINGS

OF

EXTINGUISHERS

ON

FIRE

MODELS

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

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Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

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publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.
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