A11107 3307E3

imbsik 84-2887

Flame Spread on Combustible

Solar Collector Glazing Materials

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Fire Research

Gaithersburg, MD 20899

July 1984

Final Report

Supported in part by:

Department of Energy

Office of Solar Heat Technologies

Active Heating and Cooling Division

1 J Washington, DC 20585

,U56

84-2887

1984

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NBSIR 84-2887

FLAME SPREAD ON COMBUSTIBLE

SOLAR COLLECTOR GLAZING MATERIALS

Emil Braun

Paula J. Allen

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Fire Research

Gaithersburg, MD 20899

July 1984

Final Report

Supported in part by:

Department of Energy

Office of Solar Heat Technologies

Active Heating and Cooling Division

Washington, DC 20585

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U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

TABLE OF CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES v

Abstract 1

1. INTRODUCTION 1

2 . BACKGROUND 3

2.1 Solar Collector Fires and Performance Requirements . . 3

2 . 2 Flame Spread 4

3. TEST MATERIALS 5

3.1 Dimensional Properties 5

3.2 Fire Properties 6

3.2.1 Bunsen Burner Test 6

3.2.2 Ignition Tests 7 3.2.3 Flame Spread Tests 9

3.2.4 Rate of Heat Release 11

4. LARGE SCALE TESTS 13

4.1 Experimental Design 13

4.2 Instrumentation 14

4.3 Results 15

5. DISCUSSION 18

5.1 Correlation Between ASTM D635 and Other Tests .... 18

5.2 Evaluation of Bench-Scale to Large-Scale Correlation . 20

6. CONCLUSIONS 21

7. ACKNOWLEDGEMENTS 22

iii
LIST OF TABLES

Page

Table 1. Description of Materials Used in Small-Scale Tests . . 25

Table 2. Summary of ASTM D635 Test Results 26

Table 3. A Comparison of Minimum Incident Flux, q"

Necessary for Ignition 27

Table 4. Comparison of Time to Flame Attachment (TFA) for

Ease of Ignition Tes£ and Ignition Time for ISO

Apparatus at 34 kW/m 28

Table 5. Summary of Test Results Using ASTM E162 Average

Values for Three Samples 29

Table 6. Summary of Test Results From the ISO Apparatus .... 30

Table 7. Summary of D^ta Obtained From The Cone Calorimeter

at 25 kW/m and Spark Induced Ignition 31

Table 8. Maximum Values Obtained from Roof

Mounted Instrumentation 32

Table 9. Summary of Specimen Ranking 33

iv
LIST OF FIGURES

Page

Figure 1. ASTM D635 Apparatus 3 4

Figure 2. Sketch of Ignition Apparatus 35

Figure 3. Schematic of ISO Flame Spread Apparatus 36

Figure 4. Time for Piloted Ignition as a Function of External

Radiant Flux Using ISO Apparatus 37

Figure 5. Time for Piloted Ignition as a Function of External

Radiant Flux Using ISO Apparatus 38

Figure 6. Time for Piloted Ignition as a Function of External

Radiant Flux Using ISO Apparatus 39

Figure 7. Schematic of ASTM E162 40

- 1/2 Figure 8. Flame Spread Rate, V , as a Function of External

Incident Flux Using ISO Apparatus 41

- 1/2 Figure 9. Flame Spread Rate, V , as a Function of External

Flux Using ISO Apparatus 42

Figure 10. Over-All View of Rate of Heat Release Apparatus,

Cone Calorimeter 43

Figure 11. Photograph of Large Scale Fire Test Assembly with

Ignition Cribs in Place 44

Figure 12. Description of Instrumentation for Large Scale

Solar Glazing Tests 45

Figure 13. Maximum Extent of Flame Spread for Large Scale

Solar Glazing Tests 46

Figure 14. Flame Spread Rate for Large Scale Fire Tests of

Solar Collector Glazings 47

Figure 15. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using Polycarbonate,

PC, Glazing 48

Figure 16. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using Glass Fiber

Reinforced Plastic, GRP-2, Glazing

Figure 17. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using Glass Fiber

Reinforced Plastic, GRP-1, Glazing 50

v
LIST OF FIGURES (Continued)

Page

Figure 18. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using PMMA

Glazing 51

Figure 19. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using Polycarbonate, PC, Glazing .... 52

Figure 20. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using GRP-2 Glazing 53

Figure 21. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using GRP-1 Glazing 54

Figure 22. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using PMMA Glazing 55

vi
FLAME SPREAD ON COMBUSTIBLE SOLAR COLLECTOR GLAZING MATERIALS

Emil Braun

Paula J. Allen

Abstract

The use of ASTM D635 and associated criteria as an evaluation method for

solar collector glazings was investigated. Four materials commonly used in

solar collector applications were evaluated by ASTM D635. Four other test

methods were used to characterize the glazing materials as to ignition, flame

spread, and heat release rate. These results were compared to large scale

fire tests of these materials. Based on the large scale tests, it was found

that ASTM D635 produced test results that were not consistent with those

obtained from the large scale tests.

Good agreement was found between the rank ordering of the large scale

tests and heat release rate and ignition properties as measured in the cone calorimeter and modified ISO test.

Key words: ASTM D635; fire test; flame spread; glazing materials;

ignition; large scale fire tests; rate of heat release; small scale fire

t tests; solar collectors.

1 . INTRODUCTION

The design and construction of buildings are controlled by local and

national building codes. These codes attempt to ensure that a safe and

durable structure is assembled. The codes mandate that building designs

comply with specific structural and fire requirements. With the increased use

of solar collectors, concern has been directed towards ascertaining the impact

solar collectors have on the fire performance of the entire roof assembly.

Solar collectors made of combustible components could provide a path for rapid

flame spread from one area of a roof to another area. The fire hazard

associated with roof mounted solar collectors include the combustibility of

materials used in the construction of the collector itself (i.e., pipes,

1
glazing, casing, absorber plate, insulation), the transfer fluids, and the

construction of the roof assembly (i.e., roofing material and insulation).

Model building codes [1,2,3]^ utilize ASTM D635 [4] as one of the test

methods for classifying plastic wall and roof panels. Based on this classification, maximum permitted areas are defined for each occupancy group.

Requirements [5,6] for roof mounted solar collectors use the same test method

and classification system to evaluate the acceptability of plastic covers on solar collectors. The Uniform Building Code [6] specifies that for buildings

not over three stories in height or 836 m (9,000 ft"

6

) in total floor area combustible glazings whose thickness exceeds 0.254 mm (0.01 inch) are limited

to

Classification Percent of Roof Area

CC1 33 1/3

CC2 25

For plastic glazing less than 0.254 tarn (0.010 inch) thick, any plastic may be

used provided the area of the collectors does not exceed 33 1/3 percent of the

total roof area.

A correlation between D635 and actual fire performance has not yet been

established. It was the purpose of this study to evaluate the flame spread

characteristics of combustible solar collector glazing materials and compare

small-scale fire measurements to large scale fire performance. The candidate

materials were subjected to the five small scale tests listed below.

Small Scale Tests

Test Name

ASTM D635

Ease of Ignition Test

Modified ISO apparatus

ASTM E162

Cone calorimeter

Measurement

Rate or extent of burning

Time-to-flame attachment

Ignition time

Flame spread rate

Flame spread index

Ignition time

Rate of heat release

^ Figures in brackets indicate literature references at the end of this

report .

2
These tests measured several fire properties that were useful in characterizing combustible glazing materials. It was assumed that the glazing material

would not be the first item ignited. Ignition and flame spread along combustible solar glazing material would be driven by the presence of an existing

fire in close proximity to a solar collector system. With the exception of

ASTM D635, all of the test methods used to characterize these materials evaluate fire performance under conditions of an externally imposed heat flux.

Since no test method directly simulated end use conditions, ignition and flame

spread test methods were selected that varied in:

1. sample mounting geometry;

2. sample size;

3. level of incident energy;

4. ignition mechanism.

Each glazing material was also evaluated in a large scale fire test of a simulated roof assembly with directly mounted flat plate solar collectors.

These tests were designed to determine material response to an existing fire

occurring adjacent to a solar collector system. Large scale and small scale

test results were analyzed for correlation factors.

2. BACKGROUND

2.1 Solar Collector Fires and Performance Requirements

A recent fire incident involving a newly installed solar collector system

[7,8] dramatizes the complex nature of evaluating the fire risk associated

with solar collector systems. Such a system is a multi-component assembly.

Its fire performance is dependent on the interaction of the component parts

upon exposure to a fire environment. The case cited involved the self-heating

of collector and roofing materials caused by the stagnation heating of the

solar collector system. This incident has led to work [9,10] investigatin','

low temperature, long term exposure of collector and roofing materials.

Some work has been done on component evaluation specifically aimed at

solar collector applications. Most notably, Lee and Walton [11] conducted

3
fire experiments on solar heat transfer liquids and developed a flash point

criteria for the selection of appropriate system fluids.

In general, building codes classify roof finishing materials by their

performance in ASTM E108 [22]. This test method determines the fire

characteristics of roof coverings when exposed to fires originating outside of

the building on which they are installed. Glazing materials used in solar

collectors are evaluated by ASTM D635 [4], In an attempt to bridge this gap,

Walton and Waksman [12] conducted a series of E108 tests on actual solar

collectors. Their tests involved three types of glazings; tempered glass,

glass fiber reinforced plastic, and poly(methyl methacrylate) (PMMA). With

regard to surface flame spread , they observed that flame spread on the PMMA

glazing was greater than on the roof covering material, and that glass fiber

reinforced plastic glazing exhibited more rapid flame spread than PMMA.

However, since they were using actual solar collectors, the collectors varied

in design and construction as well as the glazing material. It is, therefore,

difficult to attribute collector fire performance to one specific component.

2.2 Flame Spread

The basic understanding of the phenomenon of flame spread is currently

being developed. While three modes of heat transfer are possible (conduction,

convection, and radiation), the dominant mode is determined, in large part, by

the geometry of the sample, the direction of flame propagation and the direction and magnitude of airflow. Several combinations of the above have recently

been investigated resulting in the development of empirical models for predicting flame spread rate across a combustible solid. The chemical and

physical phenomena governing flame spread over the surface of combustible

solids have recently been reviewed by Fernandez-Pello and Hirano [13].

Flame spread in large scale fires is predominantly controlled by

radiation feedback from the flame. It would be expected that this would also

be valid for full scale solar collector fire tests. A theory of radiatively

driven flame spread was formulated by Rockett [14].

4
Quintiere [15] has recently developed an improved test method based on

that theory, configured for vertically oriented samples with horizontal,

against- the-wind flame spread. The analysis relates , the rate of flame

spread, to q”, the external imposed flux and to two material constants, C

and q" . : o,ig

V

°° = C (q" . - q")

f

" n o,ig H e'

where C = a derived material constant

q" . = minimum flux for piloted ignition. o,ig

The flame rate coefficient, C, is a function of flame transfer distance,

rate of heat transfer from the flame, and thermal properties of the substrate

(thermal diffusivity, thermal conductivity, and heat transfer coefficient).

This relationship is applicable to against-the-wind flame spread on a specimen

thermally equilibrated to an external (non-zero) radiant flux field prior to

ignition.

The translation of laboratory measurements of C and q^ ^

to predictions

of full-scale flame spread has not yet been systematized. It was, indeed, an objective of this study to see if such a relationship could be observed.

3. TEST MATERIALS

A total of seven materials were selected for laboratory evaluation. Four

samples were representative of glazing materials suitable for solar collector

applications. Two types of roofing shingles common to the building industry

and a fiberboard sample with uniform physical and fire characteristics were

included.

3.1 Dimensional Properties

Table 1 is a tabulation of material identification, thickness, and

density. The glazing materials had a thickness range of 1 to 1.6 mm, vh 1 ! ••

5
the roofing shingles were approximately twice as thick. The fiberboard sample

was four to six times as thick as any glazing material. The poly(methyl methacrylate) (PMMA) and the polycarbonate were the thickest of the glazing

samples. The two glass fiber reinforced plastic samples were the thinnest

materials evaluated.

O O Material density varied from 900 kg/nr fiberboard to 1780 kg/m fiber

glass shingles. While PMMA and polycarbonate (PC) samples were the thickest

o o glazing materials, they had the lowest density: 1350 kg/nr and 1220 kg/mJ

* respectively. The fiber glass shingles had an ASTM E108 rating of Class A,

while asphalt shingles where rated Class C.

3.2 Fire Properties

All seven materials were subjected to five small scale fire tests. Two

tests measured ignition, two measured flame spread, and one measured the rate

of heat release characteristics of the candidate materials. In addition, the

samples were classified according to the results obtained from ASTM D635.

Ease of ignition, flame spread rate, and heat release rate each provide single

property measurements of fire performance. Within the context of a test

method, each property measurement is conducted under controlled conditions.

3.2.1 Bunsen Burner Test

Solar collector glazings are classified according to the results obtained

from ASTM D635. There are two acceptable rating levels, in addition to test

failure. A CC1 rating implies that the test material did not burn 25.4 mm

beyond the initial mark. A CC2 rating indicates a burning rate less than

1.1 mm/s. A burning rate in excess of CC2 is unacceptable and not permitted

for use in roofing assemblies.

ASTM D635 describes a small scale laboratory screening procedure for

comparing the relative rate of burning or extent and time of burning of selfsupporting plastics. A test specimen, 125 ram long by 12.5 mm wide by normal

thickness, is supported horizontally at one end with its transverse axis

inclined at 45° to the horizontal, Figure 1. A screen of wire gauze is placed

6
10 mm below the lower edge of the specimen such that 13 mm of the specimen

extend beyond the edge of the gauze. A bunsen burner is adjusted so that with

air ports open a 25 mm blue flame is produced. The free end of the sample is

exposed to the flame for 30 seconds. The rate of burning is measured over a

75 mm distance beginning 25 mm from the exposed edge of the specimen. If the

specimen extinguishes before reaching the 100 mm mark, the time to extinguishment and the distance burned are recorded.

Table 2 summarizes the results of tests on seven materials conducted in

accordance with ASTM D635. Three materials self-extinguished prior to the

termination of the test. The extent of burning was greatest for the polycarbonate sample, 50 mm, and the shortest for one of the glass fiber reinforced plastic (GRP-2), 15 mm. The fiber glass shingles produced an intermediate value of 25 mm. Burning rate values were obtained for the remaining

four materials. The values varied from 0.12 to 0.71 mm/s. The solar

collector materials, PMMA and GRP-1 , burned approximately five times as fast

as the fiberboard and Class C asphalt shingles.

Material classification indicates that there were only two CC1 rated

materials, glass fiber reinforced plastic, GRP-2 and fiber glass based

shingles, FGS. All other materials were rated CC2. No material was found to

have a rate of burning in excess of 1.1 mm/s, which would prevent it from

being used on any roof structure.

3.2.2 Ignition Tests

Two test methods have recently been developed that measure ignition delay

of a material when exposed to an external source of energy. The test method

developed by Lawson and Parker [16], known as an ease of ignition test, determines the time to flame attachment of a vertically mounted sample exposed to a predetermined flux field from a methane flame. The other test method uses a flame spread apparatus currently under consideration by the International

Standards organization (ISO) [17]. Quintiere has modified the test procedure

in order to determine ignition time as a function of incident flux.

7
In the ease of ignition test, two parallel vertically oriented specimens,

140 mm wide by 152 mm high, are mounted with their outer surfaces facing each

other but separated by 50 mm. The facing surfaces of both specimens are exposed to a methane diffusion flame produced by multiported burners located

below each mounted specimen. Methane gas is initially ignited by an electrical spark igniter also located below the specimens but in the gas stream. A

stablized flame extends approximately 150 mm above the specimens which are mounted in two parallel holders. Figure 2 is a sketch of the ignition

apparatus. The burner flame exposure constitutes, on the average, an external

flux of 34 kW/m across the specimen surface. The ignition time is defined as the time from initial flame exposure until a flame attaches itself to the

surface of a specimen.

A schematic of the ISO apparatus is shown in Figure 3. The apparatus

consists of a radiant panel heat source, pilot flame, and sample holder. The

radiant source is a porous refractory panel measuring 280 mm by 483 mm,

similar to that employed in the ASTM E162 test apparatus. The sample holder

is 155 mm high by 800 mm long with a pilot flame located at one end of the

sample holder. The radiant panel is positioned over the sample holder so that

a nonuniform flux distribution is developed for flame spread measurements.

For the determination of ignition time as a function of incident flux,

the fuel-to-air ratio feeding the radiant panel is adjusted to produce a different incident flux. This flux field is nearly uniform over the first 10 mm of the sample holder. Tests at several incident flux levels are used to

determine the minimum incident flux necessary for ignition.

Figures 4, 5, and 6 are plots of ignition time as a function of external

flux for all seven materials. Using a method described by Quintiere, it is

possible to calculate the minimum incident flux, ^necessary for

ignition. These are indicated by vertical lines and labeled with the calculated values. A list of q" . for all seven materials, table 3, shows that o,ig

fiber glass shingles and polycarbonate glazing require two to three times more

incident flux for ignition than PMMA and fiber glass glazings.

8
Table A is a comparison of time to flame attachment (TFA) as determined

in the ease of ignition test and the time to ignition for the ISO apparatus.

O _ Times listed are for an external flux of 34 kW/m . The values reported for

the ISO apparatus were determined by linear interpolation of the data. No

ignition time could be determined for the polycarbonate sample in the ease of

ignition test, because it melted and flowed out of the exposure zone. However, ISO results indicate that this material is the most resistant to

ignition of the seven materials tested.

Comparisons between the two ignition measurements are remarkable in their

similarities. With one exception, ignition times are shorter than TFA, but

the rank order of materials are nearly the same. Sample GRP-1 , a glass fiber

reinforced plastic glazing, has the shortest TFA but an ignition time comparable to the roofing materials, whereas the TFA and ignition time of another

glass fiber reinforced plastic, GRP-2, are more consistent with each other.

Comparison of Rank Order of TFA and ISO Ignition Time

TFA ISO

polycarbonate Long time polycarbonate

f iberboard fiberboard

fiber glass shingles asphalt shingles

asphalt shingles GRP-1

PMMA fiber glass shingle

GRP-2 PMMA

GRP-1 Short time GRP-2

3.2.3 Flame Spread Tests

The surface flammability of materials can be measured by various test

methods. Two were selected for the evaluation of surface flame spread of

combustible glazing materials.

ASTM E162 [18] was one of the test methods used to evaluate surface flame

spread. This test method also provides a laboratory te6t procedure for

measuring and comparing the surface flammability of materials when exposed to

9
a varying level of radiant heat flux, however, flame spread is measured horizontally downward. A specimen is exposed to a vertically oriented radiant heat

source consisting of a 305 mm by 457 mm porous refractory panel, figure 7.

The specimen, 152 mm by 457 mm, is inclined toward the panel such that

ignition is forced by a pilot flame at the high heat flux upper edge. The

flame's progress down the specimen is timed. The exhaust stack is equipped

with eight thermocouples, which are used for determining the average peak

temperature of the exhaust gases. The flame spread index, I

g

, is computed as

the product of the flame spread factor, F

g

, and the heat evolution factor, Q:

I = F x Q

s s

Three samples of each material were tested, with the results tabulated in

Table 5. The poorest performing material was PMMA, I

g = 346, while the best

was fiber glass shingles with an I of 22. The polycarbonate was nearly as

O good at 38. The two glass fiber reinforced plastic samples appear to demonstrate large differences in fire performance with I 0 values of 80 and 199.

However, sample GRP-1 exhibited the most erratic burning behavior. The range

of I was 8 to 180. Based on this, it was not possible to distinguish between

the two GRP samples.

A review of the data tabulated in Table 5 shows that the specimens

differed substantially in their heat release indices, but only moderately in

flame spread values proper.

The previously cited ISO apparatus was used with the radiant panel set to

produce a maximum heat flux of 50 kW/nr1 at the location of the pilot flame.

O This decreased to approximately 2 kW/m at the opposite end. Flame spread

data obtained under these conditions were analyzed according to Quintiere's

- 1/2 procedure [15]. With this method the data for are plotted as a function

of q". Finite flame spread is achieved when q" < q” < q" . . The q" is

0 o,s 0 o,ig O jS

the minimum external heat flux required to sustain flame spread and, depending

on the material, may be equal to or greater than zero. The q” . term should

o , ig

have the same value, approximately, as the minimum flux for piloted ignition

“ 1/2 ... measured in ignitability tests. Since is a linear function of q^ over

the narrow range, q" . to q" , the slope of the line is the rate coo , lg o ,

s

efficient C.

10
- 1/2 Figures 8 and 9 are plots of V

^ as a function of external incident

flux with q" labeled. Using q" along with the previous data, the rate

O J S O y S coefficients, C, can be computed for all seven samples, Table 6. For a given

flux profile and assuming thermal equilibrium, C determines the maximum flame

spread rate. The rate coefficient indicated that the polycarbonate sample,

S2, and the glass fiber reinforced plastic, GRP-2, should be approximately

comparable, while the other glass fiber reinforced plastic sample, GRP-1

,

should be better than PMMA, but only marginally worse than samples PC and GRP2. Given C and , it is possible to calculate [15] an ignition temperature,

T

ig , from

V f - [ no (T. - T ) ] lg s

J -2

where T

g is an initial uniform temperature of the substrate. These values are also listed in Table 6 and will be useful in evaluating large scale test

results. Taken together, the flame spread data measured by F

g (Table 5) and

by C (Table 6) suggest that all test materials show similar flame spread

behavior, to within a factor of two, except for FB, which is substantially

better

.

3.2.4 Rate of Heat Release

A bench-scale rate of heat release calorimeter, has recently been

developed based on the oxygen consumption principle [19]. This principle

states that the heat released per unit mass oxygen consumed is approximately a constant for a wide range of organic fuels. It has been shown [20] that

O 13.1 x 10 kJ/kg of oxygen is a representative value for typical combustible

materials. The heat release rate is computed from the measurements of mass

flow rate and oxygen concentration through the exhaust stack, while the

effective heat of combustion can readily be determined by using the heat

release rate and the corresponding measured mass loss rate of the sample.

Specimens are mounted in a horizontal, face-up orientation, below a temperature controlled heater, Figure 10. The specimen was 100 x 100 min In

size at full sample thickness. The heater was similar to an ISO designed

heater [21] with a spark ignitor added to improve ignition repeatability.

11
horizontally mounted heater can be operated over a range of temperatures such

O that the incident flux on the sample surface can be varied from 10 kW/m to

100 kW/m2

.

The maximum heat release rate, effective heat of combustion, and ignition

time are tabulated in Table 7. The maximum heat release rate and effective

heat of combustion were obtained directly from a data reduction program.

Since the measurements were taken prior to the implementation of an ignition

time logging scheme, the ignition time was inferred from the weight loss

data. The ignition time was defined as the time from exposure of the sample

to the cone heater until the occurance of sensible weight loss. Therefore,

these ignition times are approximate. These values, however, are comparable

to the values determined from the ISO flame spread apparatus at the same external incident flux.

Ignition time at 25 kW/m2

Solar Glazing Material

CONE

(s)

ISO Flame

Spread Test

(s)

PMMA 60 50

PC — —

GRP-1 44 59

GRP-2 107 81

Reference & Roofing Material

ISO Flame

Spread Test

(s)

CONE

(s)

FB 150 127

FGS 320 321

AS 110 120

Except for samples PMMA and PC, the peak heat release rates are all

within the range of 215 kW/m to 421 kW/m . PMMA has a peak heat release rate

one third larger than the other samples. Polycarbonate, PC, would not ignite

at 25 kW/m . The effective heat of combustion of the roofing shingles were

slightly more than the other materials.

Because the polycarbonate would not ignite at 25 kW/m , additional tests were conducted on this sample and on PMMA at 50 kW/m . As noted below,

increasing the external incident flux increased the maximum heat release rate

of PMMA by 50 percent. The effective heat of combustion, however, decreased

12
by about 30 percent. If all samples increased their heat release rate by 50

percent at 50 kW/m^, the 880 kW/m^ recorded for polycarbonate would be very

high.

Rate of Heat Release at 50 kW/m2

Max. Heat Effective Heat Ignition

Release Rate of Combustion Time

(kW/m 2

) (MJ/kg) (s)

PMMA 1136 25 20

PC 880 32 53

4. LARGE SCALE TESTS

Four large scale outdoor tests were conducted to evaluate flame spread

characteristics of combustible solar glazings. The glazings used in these

tests were similar to the samples evaluated in the laboratory tests, samples

PMMA, PC, GRP-1, and GRP-2. Measurements were made of the extent of flame

spread across the glazing and the temperature and heat flux to adjacent

surfaces

4.1 Experimental Design

A simulated roof section, 2.4 m wide by 4.8 m long, was constructed,

Figure 11. The roof deck was made from standard steel studs and plywood

(nominal 12.7 mm) sheets. The plywood was covered with Class A fiber glass

shingles, similar to sample FGS except below the simulated solar collectors.

Provisions were made for the placement of wood cribs at one end of the structure. The entire structure was placed on a frame support configured to maintain the roof at an inclination of 60° from the horizontal. The frame support

was placed on a wagon to allow for the correct positioning of the test structure relative to prevailing the wind.

A simulated solar collector system was directly mounted on the central

portion of the roof deck. The solar collectors were divided into six sections

of 0.6 m by 1.22 m steel boxes covering a total of 1.22 m by 3.66 m of roof

13
decking. Each collector box was framed with steel studs and backed by a 1.6 mm thick steel sheet. The glazing, therefore, was raised 90 mm above the

roof surface. No additional insulation was used in the collector construction

in order to eliminate additional design variables. The glazing material was attached to the collector box studs. Wood finishing straps were placed over

the glazing edges and also affixed to the box studs.

Three wood cribs placed in an "L" pattern at one end of the roof assembly

were used as the source of external energy. Each wood crib was an arrangement

of 38 mm by 38 mm white pine wood strips with a finished size of 457 mm by

508 mm long by 152 mm wide. Rows of three 508 mm long strips were alternated

with rows of seven 152 mm strips to a full height of 457 mm. Each wood crib

weighed approximately 9 kg. Each crib was placed in a metal pan containing

470 ml of heptane. The heptane was used to rapidly involve the cribs in

flames. This was an attempt to simulate a fully involved roof fire. The cribs were allowed to burn until they self-extinguished.

4.2 Instrumentation

The roof assembly was instrumented with thermocouples and total heat flux

meters. These monitored the thermal impact of the fire at various locations.

Eight thermocouples and five heat flux meters were distributed on the roof

assembly as shown in Figure 12. In addition, wind direction and speed were

recorded throughout each test.

Type K thermocouples 0.51 mm (20 mil) in diameter were surface mounted on

the fiber glass shingles, wood straps, and glazing. Gardon type water-cooled

heat flux meters were used to measure incident heat flux. They were mounted

flush with the surface of the glazing and fiber glass shingles. Wind speed

was determined by a calibrated anemometer, while the wind direction was measured by a circular potentiometer. All instruments were connected to a digital data acquisition system that recorded the data on magnetic tape at a fixed time interval of 10 seconds.

14
4.3 Results

Figure 13 shows the extent of maximum flame spread across the simulated

collectors. The darkly shaded area represents the area over which the flame

propagated and the lightly shaded area is significant thermal degradation

beyond the maximum extent of flame spread. In figure 13 A and B, fire damage

was limited to the first panel adjacent to the fire cribs and approximately

one-third of the second panel. Althought figure 13A shows that flame propagation was limited to less than the full area of the first panel, all of the

polycarbonate material in that panel was consumed. The material near the top

of the panel melted and flowed down into the flame front. Thermal radiation

impinging on the second panel distorted and melted it, but flames did not

propagate beyond the wood cover strip between panel sections.

The GRP-2 sample evaluated in the second test propagated a flame into the

second panel, while GRP-1, figure 13C, exhibited flame propagation into the

third panel. Fire damage in these tests exceeded the maximum observed flame

spread by only a small amount and, therefore, was not shown in figures 13B and

C.

The results of PMMA testing is shown in figure 13D. Flames propagated

across the entire collector area. When this test ended no glazing material

remained on the roof structure. Total burning time of each test, which is the

total time of visible flame on the test structure, and the time at which flame

propagation stopped, resulting in stationary burning, are listed below.

Test

Number

Specimen

Code

Burn Time

(s)

Flame Spread

Termination

(s)

1 PC 1220 305

2 GRP-2 1270 525

3 GRP-1 2100 1640

4 PMMA 1860 1600

15
Damage to the roof structure varied for each test. During the polycarbonate test the plywood deck and roof supports ignited because they were not

properly shielded from the ignition cribs. This was corrected in subsequent

tests. There was only limited damage to the fiber glass shingles. A little

surface melting above the first panel was noted after the test. Similar

results were observed with GRP-2, used in the second test. While GRP-1, used

in the third test, appeared to have a similar effect on the roof structure,

holes charred through the plywood deck were found behind the first panel

section. The presence of additional combustibles below the steel bottom sheet

of the collector panel or plywood deck could have dramatically altered the

test results. During test three, the fiber glass shingles around the first

collector panel section ignited. This, however, may have been the result of

changes in wind direction. The effects of wind on flame spread will be

discussed below. Both GRP materials, when subjected to a thermal load, filled

the collector space (i.e., the space formed by the glazing, metal sides, and

bottom collector plate) with visible smoke. The smoke moved in advance of the

flame front and was most clearly visible in test three, GRP-1.

The PMMA used in the last test had the greatest adverse impact on the

roof structure. Flaming of the fiber glass shingles was observed. In addition, with the flames burning on the fourth collector panel section, open

flaming of the plywood deck and roof supports occurred behind the first

collector panel. These were manually extinguished before the destruction of

the roof supports prematurely terminated the test.

Because we were dealing with a large scale structure where the preferred

movement of the flame front changes during the test, the flame velocity in any

one direction is not a meaningful measure of overall performance. Instead of

a linear flame velocity, the rate at which the flame involved the collector

surface was computed. Based on test observations and photographs taken at

approximtely one minute intervals throughout a test, estimates were made of

the area flame spread rate. Figure 14 compares the area velocity for all four

tests. Initially, observable flame spread took longer to occur for the polycarbonate sample than the other three glazing materials. All four materials

exhibited a high initial velocity. With the exception of the polycarbonate

sample, area velocity decreased as a function of time. The high initial

16
velocity can be attributed to vertical flame spread. Vertical flame spread,

which is normally more rapid than horizontal, occurred under conditions of

high external incident energy while lateral flame spread took place under a decreasing external energy field. No lateral flame spread occurred during the

test of the polycarbonate sample.

Figures 15 to 18 show the center line incident energy on the surface of

the collector glazing for several distances from the wood cribs. The fluctuations in the level of incident energy for a given location was primarily due

to variations in the wind speed and direction. These variations affected the

burning characteristics of the wood cribs as well as flame spread along the

glazing surface. While the initial peaks in figures 15 and 18 at the 0.3 m

location are extremely high, it should be noted that this was undoubtedly due

to the melting and collapse of the glazing material around the heat flux meter

into the collector cavity. The heat flux meter was, therefore, completely

enveloped in flames. This is a mode of exposure for which the heat flux meter

was not calibrated. Later readings were probably valid because the flames had

progressed away from the rear of the heat flux meter. The second peak seen on figure 15 at the 0.3 m location was due to increased ventilation around the

cribs because prior to this point in time the polycarbonate surface had

extinguished. However, the second peak seen on figure 16, at the same locations, was caused by re-ignition of the sample GRP-2, which was the result

of a change in wind direction.

The effects of wind speed and direction on flame spread are shown in

figures 19 to 22. Figure 20 shows a large increase in flame velocity just

prior to extinguishment. This coincided with a rapid increase in wind speed

in the direction of flame spread. Visually, re-ignition of the glazing

material occurred due to the wind driving the flames from the ignition cribs across the glazing surface. Figures 21 and 22 show what appear to be more

subtle effects.

Table 8 is a tabulation of peak values obtained from the instruments

located above the simulated collectors on the fiber glass shingles. The ignition or non-ignition of the fiber glass shingles covering the roof is note<i in

table 8. Two tests (3 & 4) resulted in the ignition of the shingles, while

tests 1 and 2 did not cause ignition of the roof covering.

17
5. DISCUSSION

5.1 Correlation Between ASTM D635 and Other Tests

The applicability of ASTM D635 and its associated classification system

to controlling the fire risk of combustible roof glazings can be evaluated by

comparing either the classification system or test results to other measures

of fire performance. By looking only at the classification system, one is

implicitly assuming that ASTM D635 is an appropriate method for determining a materials fire performance in end-use applications. With the introduction of

new materials, it is necessary to probe deeper into the design of the test

method to insure that acceptable materials are not overlooked and, more

importantly, that unacceptable materials are not permitted to be used.

According to the classification system used by several building codes the

only glazing material meeting the requirements of a class CC1 material was

found to be the glass fiber reinforced plastic, GRP-2. This material was tested in the second large scale test. The other glazing materials were in

Class CC2. No glazing material failed to meet either requirement. Based on

this classification system, sample GRP-2 should perform significantly better,

in the other fire properties tests as well as in the large scale tests, than

the other three glazing materials. In addition, the remaining three materials

should exhibit approximately equivalent fire properties.

A review of the small-scale data indicates that sample GRP-2 did not

perform dramatically better than the other samples. In fact, the polycarbonate, PC, appeared to be more resistant to ignition and have a lower

flame spread rate than sample GRP-2. From the point of view of fire performance, the PMMA sample was by far the poorest material. It was the easiest

to ignite in addition to having the highest flame spread rate. Overall the

small scale tests do not show sample GRP-2 to have significantly better fire

performance than samples PC and GRP-1. On the other hand, PMMA does appear to

be significantly different than the other materials tested.

18
A comparison of large scale fire tests shows similar trends. The polycarbonate, and the glass fiber reinforced plastic, GRP-2 were not markedly

different from each other, while PMMA was the only material to completely burn

the entire length of the simulated roof section. The fire performance of the

GRP-1 was in between PMMA and the other two glazing samples.

The major difference between samples PC and GRP-2 was noted in the

improved dimensional stability shown by the glass fiber reinforced plastic.

The fiber glass substrate remained intact throughout the fire test, while the

polycarbonate melted, dripped and flowed into the fire exposing the collector

back plate surface to the full thermal load of the external fire. The fiber

glass base provided a thermal barrier to fire advance not provided by the

polycarbonate sample. This was true for both fiber glass based materials.

However, as noted in the third large scale test, the combustibles were seen pyrolyizing off of the unexposed surface of the fiber glass. This can also

represent a fire threat. These combustibles can be collected in dead-end

spaces and subsequently ignite spreading the fire beyond what might be anticipated by surface flame spread data alone. This may be a more serious problem

for passive heating systems, where large wall or roof sections open directly

into the living space, than for active solar collectors. While the ablating

characteristics of polycarbonate minimize this type of fire hazard in passive

systems, the interior of a building is more likely to be exposed to the full

thermal load of an external fire.

For traditional roof finishing materials, this classification system

rates fiber glass shingles as CCl and asphalt shingles as CC2. While this

appears reasonable, the other measures of fire performance indicate a large

difference exists among materials classified as CC2.

The test method exposes a small sample of a candidate material to a small

short term exposure from a bunsen burner flame. Under these test conditions,

external radiation is nil, and the forward radiation from the burning samples

minimized. End-use conditions dictate a somewhat different fire environment. The large scale tests indicated the importance of wind direction In controlling the flame spread rate. An increase in wind speed, in the intend-- i direction of flame spread, effectively increased the external radiation

19
impinging on the polymer surface. This is equivalent to imposing an external

energy field on the sample and testing with forced airflow across the sample.

ASTM D635 results show rates of 0.71 mm/ s and 0.69 mm/ s for PMMA, and

GRP-1, respectively. While these materials are both in the same material

class, large scale tests show a marked difference in flame spread as well as other small scale test results. ASTM D635 test data do show that polycarbonate is different from PMMA and GRP-1 even though they are in the same material class.

5.2 Evaluation of Bench-Scale to Large-Scale Correlation

The small number of specimens tested preclude a detailed correlation of

bench-scale to large-scale results. It is, however, possible to examine rankordering and, on that basis, suggest which bench-scale tests are desirable and

which are poor. The analysis in the previous section already indicated that

results obtained from the established test, ASTM D635, does correlate well

with other laboratory tests. Rank-ordering of the data for all the tests are shown in Table 9.

Specimens are fully correctly rank-ordered by two procedures: (1) the

values of

^ in the ISO flame spread test, and (2) the values of the peak

heat release rate and time to ignition in the cone calorimeter. The ASTM E162

values for I show only one reversal in rank-ordering, while the value of C in

the ISO test shows a reverse ranking. The ease of ignition test does not

yield any suitable ordering. These observations indicate that heat release

rate measurements (as conducted in the cone calorimeter) or radiant ignition

measurements (as determined in the cone calorimeter or in the ignition testing

variant of the ISO flame spread apparatus) offer the most promise.

Rate of heat release and ignition time testing requires the specification

of incident fluxes. These were somewhat arbitrarily specified in the present

study. A systematic evaluation of end-use exposures would be necessary in

order to validate the observed correlations at other exposure conditions.

20
6. CONCLUSIONS

The glazing material used in the design and construction of a solar

collector system represents one component of a multicomponent assembly. The

selection of any one material could adversely affect the fire performance

characteristics of an entire assembly. This, in turn, could degrade the fire

properties of a roof structure. At this point in time, ASTM D635 does not

appear to correlate with any of the other tests performed and is a less severe evaluation tool for measuring flame spread potential of solar glazing

materials. At best, this test method may provide a screening tool useable by

the material developer to evaluate products in the laboratory.

For those localities that have fire performance requirements for roof

finishing materials, the preferred test method appears to be the large scale

roofing test, ASTM E108. It would seem more consistent with current fire

design requirements to require comparable testing of solar collectors and roof

finishing materials. It should be pointed out, however, that requirements may

be necessary for all solar collector components, separately and in combination, before an adequate assessment of potential fire performance can be

made. In addition, no correlation currently exists between ASTM E108 and full

scale fire tests of solar collector systems. Data currently available are unclear as to the ability of ASTM E108 to properly distinguish between acceptable and unacceptable fire performance of solar collector systems.

Evaluation of a number of newer bench scale test procedures showed widely

disparate behaviors. Even though the large scale fire environment has an important flame spread component, a flame spread index, such as I

g (ASTM E162)

or C (ISO test) was not the most successfully predictive variable. Instead,

the heat release rate (cone calorimeter) and the ignitability properties

(modified ISO test; cone calorimeter) were found useful. Ease-of-ignition by

flame impingement (ease of ignition test) was not found useful.

21
7 . ACKNOWLEDGMENTS

The authors would like to acknowledge the help of many staff members at

the Center for Fire Research. We appreciate the assistance given by William

Bailey, Roy McLane, and David Swanson in the construction of the large scale

test structures. For reducing the data from the ISO flame spread apparatus,

we thank Margaret Harkleroad. The financial support of the Office of Solar

Heat Technologies, Department of Energy, is also gratefully acknowledged.

22
8 . REFERENCES

[Ij Light Transmitting Plastic Construction, Article 24, Building Officials

and Code Administrators International, Inc., 1981.

[2] Light-transmitting Plastics, Chapter 26, Southern Building Code Congress

International, Inc., Birmingham, Alabama, 1982.

[3] Uniform Building Code Standard No. 52-4, Method of Test for Determining

Classification of Approved Light-Transmitting Plastics, International

Conference of Building Officials, 1982.

[4] Standard Test Method for Rate of Burning and/or Extent and Time of

Burning of Self-Supporting Plastics in a Horizontal Position, ASTM

D635-81, American Society for Testing and Materials, Philadelphia, PA

(1981).

[5] Recommended Requirements to Code Officials for Solar Heating, Cooling

and Hot Water Systems, ANSI/CABO 1.0-198, Council of American Building

Officials, Falls Church, Va.

[6] Uniform Building Code, Section 1714, Solar Energy Collectors,

International Conference of Building Officials, 1982.

[7] Harvey, C.S., "Fire in a Residential Solar Panel: A Potential National

Problem," The International Fire Chief, Vol. 46, No. 9, (Sept. 1980).

[8] Walton, W.D., "Solar Collector Fire Incident Investigation," Nat. Bur.

Stand. (U.S.), NBSIR 81-2326; 1981 August. 45 p.

[9] Loftus, J. J. , National Bureau of Standards, personal communications.

[10] The Boeing Company, "National Bureau of Standards - Solar Exposure/

Temperature Measurements Flat Plate Solar Collector," -

No. TR2-5 6 15-8000-039 (1980).

[11] Lee, B.T. and Walton, W.D. , "Fire Experiments and Flash Point Criteria

for Solar Heat Transfer Liquids," Nat. Bur. Stand. (U.S.), NBSIR 79-1931

1979 November. 40 p.

[12] Walton, W.D. and Waksman, D. , "Fire testing of Roof Mounted Solar

Collectors by ASTM E-108," Nat. Bur. Stand. (U.S.), NBSIR 81-2344 1981

November. 74 p.

[13] Fernandez-Pello , A.C. and Hirano, T. , Controlling Mechanisms of Flame

Spread, Combustion Science and Technology, 32, 1-31 (1983).

[14] Rockett, J.A. , Mathematical Modeling of Radiant Panel Test Methods, Fire

Safety Research, Nat. Bur. Stand. (U.S.) Special Publ. 411; 1973 August.

251 p.

[15] Ouintiere, J.G. , A Simplified Theory for Generalizing Results from a Radiant Panel Rate of Flame Spread Apparatus," Fire and Materials,

Vol. 5, No. 2, 1981.

23
[16] Lawson, J.R. and Parker, W.J., "Development of an East of Ignition Test

Using a Flame Exposure," Nat. Bur. Stand. (U.S.) NBSIR 82-2503 1982

June. 64 p.

[17] Robertson, A.F. , "A Flammability Test Based on Prposed ISO Spread of

Flame Test, Third progress report, Intergovernmental Maritime

Consultative Organization, IMCO FP/215 (1979).

[18] Standard Method of Test for the Surface Flmmability of Materials Using a Radiant Heat Energy Source, ASTM E162-75, American Society for Testing

and Materials, Philadelphia, PA (1982).

[19] Babrauskas , V. , "Development of the Cone Calorimeter — A Bench-Scale

Heat Release Rate Apparatus Based on Oxygen Consumption," Nat. Bur.

Stand. (U.S.) NBSIR 82-2611, 1982 November. 84 p.

[20] Huggett, C. "Estimation of Rate of Heat Release by Means of Oxygen

Consumption Measurements," Fire and Materials, Vol. 4 (1980).

[21] Technical Report ISO/TR 5657-1982 (E), Fire Test Reaction to Fire

Ignitability of Building Materials, International Organization for

Standardization (July 1982).

[22] Standard Methods of Fire Tests of Roof Coverings, ASTM El08-80a,

American Society for Testing and Materials, Philadelphia, PA (1982).

24
TABLE 1

Description of Materials Used in Small-Scale Tests

Sample ID IZEg.

Thickness

(mm)

Density

(kg/m 3

)

PMMA Poly(methyl methacrylate) - cast 1.59 1350

PC Polycarbonate 1.52 1220

GRP-1 Glass fiber reinforced plastic 1.02 1380

GRP2

Glass fiber reinforced plastic 1.14 1570

FB Fiberboard 6.35 900

FGS Fiber glass shingles 2.54 1780

AS Asphalt shingles 3.18 1420

25
TABLE 2

Summary of ASTM D635 Test Results

Sample ID

Burn Rate

(mm/ s

)

Burn Time

(s)

Extent of Burn

(mm) Classification

PMMA 0.71 CC2

PC 120 50 CC2

GRP-1 0.69 CC2

GRP210 15 CC1

FB 0.12 CC2

FGS 23 25 CC1

AS 0.15 CC2

26
TABLE 3

A Comparison of Minimum Incident Flux,

Necessary for Ignition

Sample ID Description

q"o,ig

(kW/m^)

PMMA Poly (methyl methacrylate) 8.7

FB Fiberboard 9.7

AS Asphalt shingles 14.5

GRP-1 Glass fiber reinforced plastic (1.02 mm) 16.0

GRP2

Glass fiber reinforced plastic (1.14 mm) 17.3

FGS Fiber glass shingles 23.0

PC Polycarbonate 30.0

27
TABLE 4

Comparison of Time to Flame Attachment (TFA) for

Ease of Ignition Test and Ignition Time for ISO

Apparatus at 34 kW/m2

TFA ISO Ratio

Sample ID (s) (s) ISO/TFA

PMMA 62 30 0.5

PC

__(a) 290 —

GRP-1 35 67 1.9

GRP2

47 29 0.6

FB 106 95 0.9

FGS 101 64 0.6

AS 85 69 0.8

(a) Could not be tested since specimen melted out of holder prior to

ignition.
TABLE 5

Summary of Test Results Using ASTM E162

Average Values for Three Samples

Range of

Sample ID F Q I I

s s s

PMMA 10 34 346 317-364

PC 7 5 38 13-61

GRP-1 9 7 80 8-180

GRP2

10 19 199 152-268

FB 5 35 173 158-187

FGS 7 3 22 1-30

AS 11 18 214 149-290

differences in F x Q and I are due to round off errors

s s

29
TABLE 6

Summary of Test Results From the ISO Apparatus

q"

o, lg

q"

o , s C T.ig

Sample ID (kW/m2

) (kW/m2

) (m 3 /kJ) (°C)

PMMA 8.7 2.5 370 289

PC 30.0 17.5 170 561

GRP-1 16.0 12.8 200 402

GRP217.3 3.5 170 419

FB 9.7 3.0 500 307

FGS 23.0 11.0 330 487

AS 14.5 2.5 260 381

30
TABLE 7

Summary of Data Obtained From The Cone Calorimeter

at 25 kW/m2 and Spark Induced Ignition

Sample ID

Maximum Heat

Release Rate

(kW/m2

)

Effective Heat

of Combustion

(MJ/kg)

Ignition

Time

(s)

PMMA 703 36 50

PC __(a) — —

GRP-1 259 28 59

GRP2

227 28 81

FB 421 34 127

FGS 215 45 321

AS 314 44 120

(a) ^Does not

2 ignite at 25 kW/m .

31
Table

<u 3 CM CM vO

cu OCX v£3 o\

m <r

»4

U 0 • • • • < 44 w

COCU Q o o rH <r 3 3 o CU o

•H rH

44 oo 44 o o CO CO 3 3 •H z z cu cu 44 •H 3 >4 >4 3 43 toO a) CO H

>4 •U

coc 3 CM

•H 3 0 O 2 "z

NO 00 00 iH

TJ •H CM rH CM

O CU 44 4*! M3

44 3 3 u 3 •H o 4-4 0 •H

44

—s

4-4 3 CM O CU 0 43 O T3 2 B? 1 o o CM M 1 CM 00 <3" 0

-X rH 40 40

44 o 3 H a) 3

4-1 0 O 3 •H X) 3 /—s

44

a) 44 rH

O rH CM <r 00 3 3 CO H o 00 o *H o O

•H 3 rH CO 00 ON o 3 M rH

44 43

U

O •H

4-4 co •H

CU

O 3 3 cu rH CU CM iH a. 3 0 1 1 <ri CO > •H CJ Pj Pj s O P-I 2 2 3 0 <U e> o P4 o 3 a 44 0 CO •H CM X tH 1 CUH 3 3

a> too 43 •H 0 44 3a <U rH CM CO -4t CU 44 CO

CO

CU H 3

32
Summary

of

Specimen

Ranking

Ph CM rH

CD Pd 25 1 1 •U Pd CJ Pi Ph HIM EC Ph Pd Pd 6 e

•H \

CJ CJ

Ph 12 O Jd

rH

CO LTl

CJ CM

CM rH

cd -u 25 1 1 C CO 00 CJ Ph Ph o Ph Pd Pd CJ u CJ CJ

+J i CD CO g Ph e CD CJ Pd

CO E-h Ph CJ rH

4-1 TO

cO 00 CM

O CD •H 1 CP Ph CJ Ph w a = O Ph 2

CP •CT CJ

u

cj

Ph£o o

CMI PhPdCJ

CM2>i—I W

CP CO <3 Ph o

OhO

Ph I Ph

Pdcj

cj

CM

PhPd

cj

CMI o go

•H

•u •HG

W 00 M

CMI £

cj 3

cj

LOCO

25Q

CP<

CMI Ph

Pd

CJ

COCJ

Ph

CO

CJ CP3

Ph

CJ

Ph

CD 00 CJ G C

•H cO

CO

g

cO Ph CD O

Ph 4H

CJ Ph

CD CD Q Ph

CMI I Ph

PdCJ

go

*H

4-1 c0CJ

•rH 4H

•H

C

CO o

CO •H

CO 4-1 i—1

•H

CJ

G

00

at •rH 6

cO o

CP z

CO jQ CJ

33

Identical

values
Figure 1. ASTM D635 Apparatus

34
WATER

OUTLET

FRONT VIEW OF SPECIMEN

AND BURNER

FRONT VIEW OF APPARATUS

Figure 2. Sketch of Ignition Apparatus

35
Figure 3. Schematic, of ISO Flame Spread Apparatus

36
IGNITION

TIME

(s)

Figure 4. Time for Piloted Ignition as a Function of External

Radiant Flux Using ISO Apparatus

37
IGNITION

TIME

(s)

\

Figure 5. Time for Piloted Ignition as a Function of External

Radiant Flux Using ISO Apparatus

38
IGNITION

TIME

(s)

1500 -

1350 - 1200 - 1050 - 900 - 750 - 600 - 450 - 300 - 150 -

0

• FB

| Min. incident flux, q

"Q jg

_i i i

i

i i

i i 10 20 30 40 50 60 70 80 90

EXTERNAL HEAT FLUX (kW/m 2

)

Figure 6. Time for Piloted Ignition as a Function of External

Radiant Flux Using ISO Apparatus

100

39
Fuel/air

Figure 7. Schematic of ASTM E162

AO
CM

I

CO

E

E

LLJ h-

<

ccQ

<

LU

DC

Q.

CO

HI

<

-J

ll

Figure 8. Flame Spread Rate, V

- 1/2

as a Function of External

Incident Flux Using ISO Apparatus

41
CM

0)

"s. E

E

LU

I-

<

DC

Q

<

LU

DC

CL

C0

LU

Z>

<

10 20 30 40

EXTERNAL HEAT FLUX (kW/m 2

)

Figure 9. - 1/2 Flame Spread Rate, V , as a Function of External

Flux Using ISO Apparatus

42
Figure 10. Over-All View of Rate of Heat Release Apparatus,

Cone Calorimeter

43
44

Figure

11.

Photograph

of

Large

Scale

Fire

Test.

Assembly

with

Ignition

Cribs

in

Place
T - Thermocouple

Figure 12. Description of Instrumentation for Large Scale

Solar Glazing Tests

45
B - PLASTIC REINFORCED FIBERGLASS, GRP-2

Figure 13. Maximum Extent of Flame Spread for Large Scale

Solar Glazing Tests

46
AREA

VELOCITY

x

10~°

(m^/s)

Figure 14. Flame Spread Rate for Large Scale Fire Tests of

Solar Collector Glazings

47
HEAT

FLUX

(kW/m

TIME (s)

Figure 15. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using Polycarbonate,

PC, Glazing

48
HEAT

FLUX

(kW/m

TIME (s)

Figure 16. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using Glass Fiber

Reinforced Plastic, FRP-2, Glazing

49
HEAT

FLUX

(kW/m

180 360 540 720 900 1080 1260 1440 1620 1800

TIME (s)

Figure 17. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using Glass Fiber

Reinforced Plastic, GRP-1, Glazing

50
HEAT

FLUX

(kW/m

180 360 540 720 900 1080 1260 1440 1620 1800

TIME (s)

Figure 18. Incident Energy Profile Along Horizontal Center

Line of Large Scale Fire Test Using PMMA Glazing

51
AREA

VELOCITY

Figure 19. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using Polycarbonate, PC, Glazing

52

WIND

SPEED

(km/h)
Figure 20. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using GRP-2 Glazing

53

WIND

SPEED

(km/h)
AREA

VELOCITY

Figure 21. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using GRP-1 Glazing

54

WIND

SPEED

(km/h)
Figure 22. Flame Spread Rate and Wind Speed for Large Scale

Fire Test Using PMMA Glazing

55

WIND

SPEED

(km/h)
NIS.U4A 1REV. 6° U,§, ggPT. ©P @©MM,

BIBLIOGRAPHIC DATA

SHEET flee Instrueti &n§)

1. PUBLICATION OR

RSP0RT NO.

%, PgffgFming ©fgan. ftepeft Ne.

NISI! 84-2887 July 1984

4. TITLE AND SUBTITLE

Flame Spread on Combustible Solar Collector Glazing Materials

5. AUTHOR(S)

Emil Braun and Paula J. Allen

6. PERFORMING ORGANIZATION (If joint or other than NBS, see Instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

10. SUPPLEMENTARY NOTES

[“""1 Document describes a computer program; SF-185, FIPS Software Summary, Is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant Information, If document Includes a significant

bl bl lography or literature survey, mention It here)

The use of ASTM D635 and associated criteria as an evaluation method for

solar collector glazings was investigated. Four materials commonly used in

solar collector applications were evaluated by ASTM D635. Four other test

methods were used to characterize the glazing materials as to ignition, flame

spread, and heat release rate. These results were compared to large scale

fire tests of these materials. Based on the large scale tests, it was found

that ASTM D635 produced test results that were not consistent with those

obtained from the large scale tests.

Good agreement was found between the rank ordering of the large scale tests

and heat release rate and ignition properties as measured in the cone calorimeter and modified ISO test.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) ASTM D635; fire test; flame spread; glazing materials; ignition; large scale

fire tests; rate of heat release; small scale fire tests; solar collectors.

13. AVAILABILITY

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| | For Official Distribution. Do Not Release to NTIS

r~l Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

[ X | Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

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