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NATIONAL BUREAU OF STANDARDS REPORT

6301

SURFACE FLAMMABILITY OF PROTECTED METALS

by

M. W. Sandholzer & E. W. Bender

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U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

MB® PROJECT

1000-12-4801 February 2, 1959

MBS REPORT

6301

SURFACE FLAMMABILITY OF PROTECTED METALS

by

M. W. Sandholzer & E. W. Bender

for

Tri-Service Building Materials Investigation Committee

iMPORTANT NOTICE

NATIONAL BUREAU Of ST/

Intended for use within the ( to additional evaluation and n

listing of this Report) either li the Office of the Director, Nal however, by the Government i to reproduce additional copie.

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

progress accounting documents

rmallf published it is subjected

reproduction, or open-literature

sion Is obtained In writing from Such permission is not needed,

prepared If that agency wishes

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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SURFACE FLAMMABILITY OF PROTECTED METALS

ABSTRACT

A number of protected - metal siding and roofing materials,

supplied from three different manufacturers, have been tested

for flame-spread hazard by two different methods. An inclined

tunnel test and a radiant panel test were used.

The results obtained by the two methods for the various

products tested are presented in tabular form. Relative

evaluation of the products by the two methods differed to some

extent, presumably because of the difference in type of exposure

employed.

1. INTRODUCTION

At the request of the U. S. Army Corps of Engineers and

latterly of the Tri-Service Building Materials Investigation

Committee, flame-spread tests have been made on various protec tedmetal siding and roofing materials at several different times

during the past few years. Results of the tests have been presented in several reports, submitted in compliance with the

individual requests. The present report gives the results

obtained in the most recent series of these tests, and, to

facilitate a comparison of the behavior of the various products

under exposure to flame, such previously-reported data as are

comparable have been included.

2. TEST MATERIALS

The materials tested have been supplied by inspectors from

the Office of the Chief of Engineers. They were usually obtained

directly from the factory, but were occasionally taken from stocks

delivered at job sites. A description of the various products

received, as compiled from visual inspection, from literature

supplied by the manufacturer, and from statements of the manufacturer's representatives is given in Table 1, together with

the approximate date at which test results for the respective

products were reported.
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3. TEST METHODS

The materials were tested by two different flame-spread

methods, an inclined tunnel test and a radiant panel test.

The inclined tunnel test, which has been used in many

previous tests of this type of product, involved placement of

the specimen as the cover or upper enclosing surface of a tunnel

12 ft long, and about *+0 in. wide and 9 in. deep. This tunnel

was inclined at a slope of 5 in. vertical to 12 in. horizontal.

The three fixed sides of the tunnel were of sheet metal lined

with asbestos-millboard. The igniting flame was applied to the

under surface of the specimen at the lower end.

All specimens for this test were so assembled as to have one

joint running the 12-ft length, and they were placed with the

surface intended for interior exposure facing downward and exposed to the igniting flame. The flame was applied for 35 minutes,

and was produced by burning gas with a calorific value of approximately 1100 BTU/cu ft, at a rate of 3 cu ft/min for 30 minutes

and at a rate of 5 cu ft/min for 5 minutes. The length of the

igniting flame, measured with an unprotected sheet metal cover

in place of the test specimen, was about 2\ ft. Two specimens

of each material were tested.

The radiant panel method has been described in the article,

"A Method for Measuring Surface Flammability of Materials Using

a Radiant Energy Source," Proc. ASTM, Vol. 56, 1956. It provides

a means for exposing small specimens in a standard fashion to a

radiant heat and ignition source. Measurements are made of the

rates of flame spread and heat release. These factors are combined to produce a flame-spread index which provides a numerical

means for classification of material flammability. Smoke production by the specimen is reported in terms of the weight of

material deposited on a glass filter disk.

For some of the tests made by this radiant panel method, the

corrugations in the materials were flattened out as much as

feasible before the test specimens were cut. In other cases

the test specimens were cut with the corrugations running lengthwise of the specimen, and on one product tests were also made with

the corrugations running crosswise of the specimen. From two to

four specimens of each material were tested*
,*
- 3 -

4. TEST RESULTS

The results of the inclined tunnel tests are presented in

Table 2. Only the corrugated materials were subjected to this

test. All CIS materials were tested with the interior surface

exposed to the igniting flame (the interior and exterior surfaces

were the same on all C2S materials). When the two specimens

tested in each case showed a difference in behavior, the two

individual values obtained are given.

Table 3 shows the results obtained by the radiant panel method.

The values given are averages of the results from the two to four

determinations made in each case.

5., DISCUSSION OF TEST RESULTS

The results of the inclined tunnel tests indicate little

difference in performance of the three CIS Galbestos materials,

except that the grey colored product showed a somewhat greater

final flame-spread than the others. Among the C2S Galbestos

materials, the grey colored product appeared to give the best

performance. Of the Steelbestos products tested, the grey Color

Steelbestos gave somewhat the best results. In both the Galbestos

and Steelbestos groups, the C2S materials generally showed a greater

flame-spread than the CIS materials. Among the Plasteel products,

the black Plasteel showed the least flame spread and little tendency toward dripping. Galvanizing of the sheet metal core had

no significant effect on the behavior of the material.

The radiant panel method provides a different type of exposure

from that of the inclined tunnel method, and consequently may

indicate a different relative evaluation of products tested. In

the tunnel test, the igniting gas flame sweeps over the surface

of the specimen, combining with and rapidly burning off combustible

gases evolved from the surface coating heated by the flame. Some

types of coating break down under comparatively moderate heating

but form a protective layer of char which tends to retard heating

ahead of the flame and limit flame-spread. In the radiant panel

test, however, flames do not sweep over the unburned portion of

the specimen, which is heated independently by radiant energy and

is unaffected by heat from the flames. Thus, flame-spread progresses as fast as combustible gases are produced by the radiant

heating of new material, and coatings which break down under

moderate heat will tend to show a rapid flame spread regardless

of the type of char produced..
.
Referring to the radiant panel results in Table 3, the maroon

colored products of the three groups (Galbestos, Steelbestos, and

Plasteel) showed a fairly similar performance, and it appeared

to be a decidedly better performance than that of the grey colored

products in the respective groups. Data on the behavior of the

black colored products in this test are not available. The tests

on Plasteel showed a greater flame-spread index for the corrugated materials, tested lengthwise, than for the flat stock. As

in the tunnel test, galvanizing of the sheet metal core had no

significant effect on the flame-spread results.

Considering the relative evaluation of the products by the

two test methods, the results of the tunnel tests generally indicated a slightly better performance for the grey colored products

than for the maroon colored products in the respective groups. As

tested by the radiant panel method, however, the grey products

showed a poorer performance than the maroon products. The differences indicated by the radiant panel method were considerably

more pronounced than those indicated by the tunnel method.

6. CONCLUSIONS

Several of the products tested showed a similar and reasonably

satisfactory performance in the inclined tunnel test.

The results of the radiant panel test indicated a decidedly

better performance for three of the products than for the others.

Relative evaluation of the products by the two methods differed

to some extent, presumably because of the difference in the type

of heat and flame exposure employed.

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TABLE 2. Results of Inclined Tunnel Tests

Date of Product Color Time dripping Maximum f lame spread

Report designation first appeared 0-30 min. 3° "35

6/55 Galbestos C2S black

min

4-.0

ft

1.0

ft

filled tunnel

extending out top

1/57 Galbestos C2S maroon 6.0 and 7*0 3.5 12.0

II Galbestos C2S grey none 2.5 and 4-.

4-. 5 and 9*5

6/55 Galbestos CIS black 3.0 and none 0.5 3.0

1/57 Galbestos CIS maroon none 1.5 3-5

It Galbestos CIS grey none 1.5 4-. 5 and 7*5

6/55 Steelphalt black 2.0 and 3*0 3.5 filled tunnel

extending out top

1/57 Steelbestos

C2S maroon 5.0 and 7«0 2 . 5 and 5 * 5 12.0

6/55 Steelbestos

CIS

black 3.0 and 4-.0 2.0 and 4-.0 7.0

1/57 Steelbestos

CIS maroon none 1.5 6.5

12/58 Color Steelbestos CIS grey none 2.0 2.5

6/55 Plasteel black 8.0 and none 0.5 4-.

1/57 Plasteel maroon 1.5 and 2.0 1.5 12.0

1/59 Plasteel C2S grey 2.5 and 4-.0 6.0 and 4-.0 7.5

II Plasteel

CP-400, C2S II 4-.0 and 1.8 4.5 and 5*0 8.0 and 7*0

II Plasteel CIS II 1.5 4-.0 and 6.0 7.5 and 6.0

II Plasteel

CP-400, CIS II 2.0 and 1.0 4.0

! 7 . 0 and 6 .

TABLE 3. Results of Radiant Panel Tests

Date of Product Color Direction, con- Flame spread, I Smoke production

Report designation dition of

corrugation interior

surface

weatheri

surface'

interior

surface

weather

surface

1/57 Galbestos C2S maroon flattened -- 3.7

mg mg

2.3

If Galbestos C2S grey II — 37.0 3.3

If Galbestos CIS maroon II 0.0 1.5 1.2 1.7

II Galbestos CIS grey II 0.0 56.0 2.0 2.1

n Steelbestos

C2S maroon II — 7.2 — 1.0

II Steelbestos

CIS II II 0.0 8.9 1.5 0.9

12/58 Color Steelbestos CIS grey II — 54.0 — 2.2

II Color Steelbestos CIS II lengthwise 23.0 98.0 o.5 2.2

II Color Steel-r

bestos CIS II crosswise 9.5 — 0.9 —

1/57 Plasteel maroon flattened — 5-5 —

i" 0.5

1/59 Plasteel CIS grey lengthwise l4.0 84. o 0.9 1.2

II Plasteel CIS II no corrugations 1.0 35.0 0.8 1.4

II Plasteel

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85.0 0.9 2.1

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CP-400, CIS II no corrugations 3.2 30.0 1.0 1.1 •

1

U. S. DEPARTMENT OF COMMERCE

Ltawls L, Strauss, Secretaty

NATtONAL BUREAU OF STANDARDS

A. V. Astlh, Director THE NATIONAL RIJREAI) OF STANOAltOS

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