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Technical Note (National Research Council of Canada. Division of Building Research), 1965-06-01
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Inert Gas Generator: Extinguishment Tests
McGuire, J. H.
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No.
DIVISION OF BUILDING RESEARCH
NATIONAL RESEARCH COUNCIL OF CANADA
444
NOTlE
'Jr
EClHIN II CAlL
,
liMITED
DiSTRI BUTlon
PREPARED BY J. H. McGuire CHECKED BY GWS APPROVED By NBH
ｾ June 1965
PREPARED FOR limited distribution
SUBJECT
INERT GAS GENERATOR: EXTINGUISHMENT TESTS
The following ｮｯｴｾｳ summarize extinguishment tests carried out by the Fire Re search Section, NRC. in the M- 59 burn area with the NRC experimental inert gas generator (which has an output of between 3000 and 4000 cfm).
Burn area and fire s
The burn area is largely of masonry construction and has dimensions 40 by 40 by 40 ft. Four exhaust fans are located above the roof and the exhaust vents, although closed by
hydraulically operated dampers when the fans are not operating, are not completely sealed. In ｡､､ｩｴｩｯｾＬ ventilation equipment can inject air into the area at a height of about lOft. The relevant openings were not sealed during the course of the first test and it was this feature which was principally responsible for the failure to extinguish the crib fire completely.
The cribs were largely composed of 2-in. by 4-in. by 3-ft or later by 4-in. by 4-in. by 3-ft pieces of timber and were built to a height of about 3 ft. The gasoline fire was in a l-ft..:. square tray.
Oxygen concentration measurements
.'
2
-instrument and sampling was continuous. The instrument operates at 120°F and hence the measured sample cannot have a vapour pressure exceeding 88 mm or a vapour content
(by volume) exceeding 12 per cent, The output of the inert gas generator, however. has a moisture vapour content of about 60 per cent" For all 02 readings other than zero and 21 per cent. therefore. a correction factor will be necessary. A true oxygen concentration of 8 per cent would give a reading of 10 per cent. All results given in this note are uncorrected. Thermocouple measurements
As the atmosphere in the burn area becomes opaque within a few minutes of beginning inert gas injection, thermo-couples were installed some 6.... in. above the top of the crib and the surface of the gasoline to give some indication as to when flaming combustion was substantially reduced.
Test 1:8 January 1964
At this time the inert gas generator was the original version as described in DBR Internal Report No. 294.
*
Time, Thermocouple, of 02.
%
Min. Gasoline Crib (uncorrected)
0 550 20 1 1,200 20 5 1,600 19 8 1,180 1,780 18.5 18 630 1,020 16 23 200 (out) 900 14.5 32 770 13 40 180 740 12.5 Remarks Fires lit Generator started Atmosphere opaque, Fires not visible.
Generator off for two periods of about 3 min. each
):' McGuire, J. H. An experimental inert gas generator. National Research Council, Division of Building Research, Ottawa. Internal Report 294, May 1964.
3
-Immediately the test area was ventilated the crib fire came up to full intensity again.
Test 2: 13 January 1964
Oxygen analysis was made at a height of 4 ft and the cribs were on bases 9 ft and 4 ft respectively above the floor. The generator was as described in DBR Internal Report 294. The burn area ventilation system inlets were closed off.
Time, Min.
Tl;l.ermocouple, of Upper Crib Lower Crib
02,
0/0
(uncorrected) Remarks 0 19.5 4 1,750 1,300 19.5 8 1,500 1,140 18 12 1,290 400 16.5 16 660 350 15. 5 20 610 350 14.5 24 410 260 13. 5 30 400 200 12.5 37 400 200 11.5 Fires lit Generator started Both fires visibleNo flames visible (atmosphere opaque)
Neither of the cribs rekindled. The oxygen analyzer was obviously reading low at the top end of the scale. It was also found to read 1 to 2 per cent high at the zero end and was probably
reading satisfactorily at centre scale. The temperature indicator in use with the thermocouple above the upper crib had a 200°F off-set.
Other tests
Several other tests have given results similar to the last-mentioned. This was so even when a different type of water vapourization chamber was installed on the generator and the gas was delivered to the burn area at an excessive temperature and with a substantially lower water vapour content. Forty per cent of the water, which should have been consumed, was running away from the ｡ｰｰ｡ｲ｡ｴｵｳｾ
