NATIONAL BUREAU OF STANDARDS REPORT

8926

REPORT OF VISIT TO BRITISH FIRE RESEARCH STATION

5 and 6 JULY 1965

By

A. F. Robertson

i nb report has been prepared

for information and record

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U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAO OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

42102-12-4212120 July 12, 1965 8926

REPORT OF VISIT TO BRITISH FIRE RESEARCH STATION

5 and 6 JULY 1965

By

A. F. Robertson

IMPORTANT NOTICE NATIONAL BUREAU OF SI

for use within the Government, and review. For this reason, tt whole or in part, is not autho Bureau of Standards, Washing

the Report has been specifically

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

iss accounting documents intended

i subjectid to additional evaluation

3 listing of this Riport, either in

it Offlca of tha Director, National

y tha Government agency for which

copies for Its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

REPORT OF VISIT TO BRITISH FIRE RESEARCH STATION

5 and 6 JULY 1965

By

A. F. Robertson

ABSTRACT

The workers at the Fire Research Station have made significant progress in study of smoke production by diffusion flames

and the influence of N

2

, CO^ , and ^0 as addatives on the air

side. Work on experimental burn out tests has progressed well

and preliminary results suggest that the findings may tend to

justify rather than discredit the standard time-temperature

curve as a basis for fire testing. Elaborate heat flux instrumentation has been involved in these tests with the objective

of deriving a heat balance for the fires.

Work on thermal decomposition products has not developed

well because of staffing problems. The program for study of

fire performance of prestressed concrete beams has been initiated.

This includes study of the influence of continuity over supports

on the behavior of such structures. I saw one of the first of

these tests. It appears unlikely that continuity without axial

restraint will provide much benefit with respect to fire en- durance . Introduction

Advantage was taken of the need to be in London in connection with a meeting of the IMCO group concerned with fire tests for marine constructions

to visit the Fire Research Station for two days. This report summarizes the

observations made during this visit and describes some work of special interest

to us in connection with our current program plans.

fr * * *

I visited Messrs. Ashton and Malhotra to discuss their work on doors and

burn-out tests. Their work on doors is being done primarily for ISO and they

are exploring ways of measuring hot gas passage through dooxs by use of a flat canopy over the unexposed surface as shown. They had set alumina plates

into the canopy; these were fitted with both copper disc thermocouples as well

as an adjacent thermocouple to measure air or gas temperature. Malhotra had

considered the incorporation of a photometer, but this has not been done yet.

They find that temperature measured at point B tends to be higher than at

point A. They, like we, are inclined to favor a radiation measurement of heat

transfer through the door.

2

The work on the British Iron and Steel Federation burn-out tests has been

assigned to another group under Mr. Butcher who was ill during tay visit. His

assistant, Mr. Chitty, showed me some of their results. The tests are being

conducted in a specially built structure as shown in the sketch. The position

of cribs is shown for the usual test in which 1/3 of the floor area is covered.

A few tests are also planned in which the fuel will be distributed over 2/3 of

the floor area. The cribs are built up of nominal 2 in. x 2 in. x 3-1/2 ft

sticks without fastening or gluing. They are arranged with single stick

spacing and built to a height sufficient to provide the required fire load

which has included 1-1/2, 3, 6, and 12 lb/ft^ of gross floor area. The cribs

marked with an X are supported on three ring dynanometers which are located

in a tube set into the floor. The cribs are all lit with kerosene-soaked

fiberboard strips to start all together. Tests have been conducted with two

ventilation arrangements, the windows wide open or half closed. The window

area is equal to one half that of the wall in which they are set. Their

height is 6 feet. They are unglazed and open from the start of the test.

3

follows

1. Vermiculite plaster heat flux meter on end wall. Thermocouples

are located at the surface and 1/4 and 1/2 in. below.

2. A special copper constantan heat flux meter within and near one

pile at four elevations. These are mounted on the surface of a water-cooled copper pipe.

3. In addition to the thermocouples located 3 in. below the ceiling,

they have introduced additional couples at about 2 and 6 feet down.

4. An aspirating thermocouple is placed through the back wall.

5. Both a McGuire radiometer and a radiation pyrometer are set to

view the flames through the window.

- 4 -

Results are still in process of being analyzed, but the following summary

seems to be indicated:

1. In general, the damage to protective covering for steel seems more

severe than that produced by a fire test of similar duration in a furnace

2. The six-pound fire load exposure provides a severe fire and will

require good protection for structural steel.

3. As sketched from memory after study of a collection of time-temperature

curves, the data were about as follows:

o

Koo

lOoo

$ Soo

WlK^DoW - M

In general, the tests with 1/4 window area seemed to provide the

most severe exposure although peak temperatures were somewhat less.

4 o Measurements had been made following Ingberg's suggestion that the

severity could be assessed by measuring the area below the curve

above base temperatures of 150 and- 300°F. The following plots show,

roughly, the results obtained and apparently justify the use of the

standard time- temperature curve.

c. 5

^0

’T’ V N\5i

5. Winds had caused trouble during a few tests resulting in unusual

circulation of air in the room during which one or more cribs did

not burn with the others.

6. Although data were not well analyzed, it appeared that there would

not be wide (> ± 20%) . variations in crib burning rate except for

the situation of unuaual wind effects.

7. The aspirating thermocouple did not appear to be too useful. Results were quite similar to those with bare thermocouples except

for the period after flaming had ceased.

8. The objective of Thomas and Hesselden was to develop a heat balance

for the system. Anenometer measurements were not too successful

and window air flow would be based on geometry and room temperatures.

9. The basic series to explore fire load and ventilation had been

completed, but additional tests were planned to study the influence

of thermal properties of wall lining on severity.

10.

Difficulty had been encountered in properly burning the cribs involved in the 1-1/2 Ib/sq ft floor area. Probably because of the

poor height to width ratio of the cribs.

6

Mr. Ashton and Malhotra had a test of a prestressed concrete beam in

progress during our visit:

Two prestress cables were used, one for positive moments

and the other for negative moments. I saw the specimen

at about 3 hours after the start of test. It was nearly 1 straight at that time, but cracks had developed across

the top slab over the supports, probably a result of

expansion of the web. The specimen failed apparently

in compression over one of the supports at about 4-3/4 hr.

A somewhat similar construction, but simply supported at

the ends without continuity had failed at just over

4 hours. Apparently, performance was not significantly

increased by continuity. These tests were being conducted for the Building Research Station. The specimens

had aged for about 2 years indoors prior to test.

I visited Dr. Rashbash and Mr. Stark, his assistant. The work on study

of smoke production from diffusion flames by Dr. McClintock had started off

very well and is covered in his reports FR Note 570, 582 and 592. He found

that soot formation of ethylene diffusion flames could be reduced by dilution

of the air by ^0, and CO2

. The latter two gases apparently being most

effective. These results seem to confirm the findings we have made on smoke

production of cellulosic materials with N2 as diluent. McClintock' s work

has been terminated by his resignation.

Dr. Rashbash called my attention to the report, "Recirculation and Fuel

Air Mixing as Related to Oil Burner Design" by Cooper, Kamo, Mar'ek and Salbing,

API Pub 1723, also, "Atmosphere from Fires in Rooms with Little Ventilating"

by A. J. Kelly, FR Note No. 494.

Mr. Stark's work on smoke and decomposition product production from

cellulosic and plastic materials in enclosures has also suffered by resignations. Apparently, work on cellulosic materials is nearing completion. The


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