A.6.4.2.3 Composite wood fuel array
The Composite wood fuel array consists of four sheets of Composite wood, 18,0 mm thick, 405 mm high, and 200 mm wide. Sheets are spaced and located as per Figure A.8. The bottom of the fuel array is located 203 mm from the floor. The fuel sheets shall be mechanically fixed at the required spacing. The Composite wood panels shall not significantly bend during the test.
The fuel array shall be located centrally within the enclosure.
A.6.4.2.4 Fuel shield
A fuel shield consisting of a metal frame with sheet metal on the top and two sides shall be provided around the fuel array as indicated in Figure A.8. The fuel shield is 380 mm wide, 850 mm high and 610 mm deep. The 610 mm (wide) x 850 mm (high) sides and the 610 mm x 380 mm top are metal sheet. The two remaining sides and bottom are open.
The metal sheet shall be aluminium with a wall thickness of 2 mm to 3 mm.
The fuel array is oriented in the fuel shield such that the 200 mm dimensions of the fuel array is parallel to the 610 mm side of the fuel shield.
A.6.4.2.5 External baffles
External baffles are constructed as shown in Figure A.9 and are located around the exterior of the fuel shield. The baffles are placed 90 mm above the floor. The top baffle is rotated 45° with respect to the bottom baffle.
A.6.4.3 Test procedure
A.6.4.3.1 General
Prior to commencing tests the composition of the extinguishing aerosol shall be analysed. Record the mass of the Composite wood panels prior to the test.
A.6.4.3.2 Operation
The n-heptane is ignited and allowed to burn completely (heptane will provide a burn time of approximately 3 min.) after the n-heptane is exhausted, the crib shall be allowed to burn freely for an additional time of 3 min resulting in a total pre-burn time of (6 ) min. At 6 min after the ignition of the n-heptane all openings are to
be closed and the extinguishing system is to be manually actuated.
At the time of actuation of the system, the amount of oxygen within the enclosure at the level of the fuel shall not be more than 0,5 vol% lower than the normal atmospheric oxygen concentration. During the test, the oxygen concentration shall not change more than 1,5 vol% due to fire products. This change shall be determined by comparing the oxygen concentration measured in the cold discharge test with the oxygen concentration measured in this fire test (averaged values).
The enclosure is to remain sealed for a total of 10 min from end of discharge. After the soak period, ventilate the enclosure and observe to determine that sufficient fuel remains to sustain combustion and for signs of reignition. The following shall be recorded:
presence and location of burning fuel;
whether or not the fire re-ignites; and
mass of the fire structure after the test.
If necessary, amend the extinguishing factor and repeat the experimental programme until three successive, successful extinguishment are achieved.
A.6.4.3.3 Results recording
After the required pre-burn period, record the following data for each test:
discharge time of extinguishant, in seconds;
time required to achieve extinguishment, in seconds. This time shall be determined by visual observation, thermocouples readings or other suitable means;
soaking time (time from the end of system discharge until the opening of the test enclosure).
A.6.4.4 Determination of design extinguishant factor
The laboratory extinguishing factor for each fuel is that which achieves satisfactory extinguishment of the fire over three successive tests (no flaming 60 s after end of discharge and no re-ignition after 10 min from end of discharge).
The design concentration is the highest of the laboratory extinguishing factors for the four fuels (see A.6.4.2.2) multiplied by an appropriate safety factor.
Extinguishing factor shall be calculated dividing the total mass of aerosol compound installed by the test room volume.
A.7 Aerosol generator explosive atmosphere test
A.7.1 Actuation test inside an explosive atmosphere environment.
A.7.1.1 Test facility
A.7.1.1.1 Construction
The test enclosure shall meet the following requirements:
steel cabinet open on top having dimensions (volume) to fit the extinguishing factor of the specific generator to be tested;
the ceiling of the cabinet/volume shall be sealed by a plastic sheet to allow the explosion (if occurs) to be vented outside avoiding any potential damage;
3 sample points shall be provided to measure the concentration of the explosive atmosphere inside the cabinet/volume:
one on the bottom, close to the cabinet floor,
one in the mid point of the test volume,
one on top, close to the ceiling;
a fan driven by an electric motor (the electric motor shall be placed outside the cabinet/volume or use an explosion proof fan unit) shall be installed on the floor to mix and obtain an homogeneous explosive atmosphere;
an ignition automotive spark plug (or any suitable ignition device) shall be installed at about the middle of the cabinet/volume (close to the same position of the aerosol generator) to ignite the explosive mixture.
A.7.1.1.2 Instrumentation
The explosive mixture shall be measured utilizing a suitable explosive meter connected to the 3 sample points.
A.7.1.1.3 Explosive atmosphere
The explosive atmosphere shall be obtained metering inside the test cabinet/volume propane or mixture of propane/butane utilizing a bottle equipped with a pressure reducer, mixing the atmosphere using the fan and checking the percentage of the propane of propane/butane mixture with the explosive meter (the range shall be between the Lowest Explosion Level and the Highest Explosion Level. The explosive atmosphere shall be checked by repeating the explosion test 3 times actuating the spark plug, the explosion will prove the atmosphere inside the test cabinet/volume is really in the explosive range.
A.7.1.2 Test procedure
A.7.1.2.1 General
Prior to commencing tests, the composition of the explosive atmosphere shall be obtained and checked according the procedure described in A.7.1.1.3.
A.7.1.2.2 Operation
The aerosol generator shall be placed inside the test cabinet/volume about the middle of the volume and connected to the actuation device/wiring. The propane or propane/butane mixture will be administered to obtain the explosive atmosphere and the generator will be left inside the explosive atmosphere for 3 min to allow the explosive atmosphere to enter inside the generator casing.
After 3 min of immersion inside the explosive atmosphere the generator shall be actuated and shall discharge without initiating any explosion.
After the test, the test cabinet/volume shall be securely vented.
A.7.1.2.3 Results recording
Record the following data for each test:
the data from the explosive meter proving that the administered atmosphere has been in the explosive range;
the result of the test, by visual observation.
A.7.1.3 Pass fail criteria of the explosive atmosphere generator actuation test
All 3 tests shall not initiate any explosion.Bibliography
EN 2, Classification of fires
EN ISO 9001, Quality management systems - Requirements (ISO 9001:2008)
CEN/TR 15276-2, Fixed firefighting systems - Condensed aerosol extinguishing systems - Part 2: Design, installation and maintenance
