The test method involves mounting the conditioned specimen
in a well-defined flux field and measuring the time of ignition, spread
of flame, its final extinguishment together with a stack thermocouple
signal as an indication of heat release by the specimen during burning.
8.1.1 Prepare a properly conditioned specimen
for test in a cool holder away from the heat of the radiant panel.
Prior to insertion in the specimen holder, the back and edges of the
specimen should be wrapped in a single sheet of aluminium foil of
0.02 mm thickness and dimensions of (175 + a) mm x (820 + a) mm where
"a" is twice the specimen thickness. When inserted in the specimen
holder each specimen should be backed by a cool 10 ± 2 mm board
of non-combustible refractory insulating material with the same lateral
dimensions and density as the dummy specimen. When mounting non-rigid
specimens in the holder, shims should be placed between specimen and
holder flange to ensure that the exposed specimen face remains at
the same distance from the pilot flame as a rigid specimen. For such
materials, the shims may often only be required for a 100 mm length
at the hot end of the specimen.
8.1.2 The dummy specimen in a specimen holder
should be mounted in position facing the radiant panel. The equipment
fume exhaust system should be started.
8.1.3 The radiant panel is operated to realize
the test conditions as specified in 6.3.
Start the millivolt recorder recording the output signal of the stack
thermocouples, as well as signal from the total radiation pyrometer
or heat-fluxmeter positioned, as described in 6.3.2.
8.1.4 When the radiant panel and stack signals
have attained equilibrium, after the preheat period, light the pilot
flame, adjust its fuel flow rate and observe both signals for at least
three minutes and verify continued signal stability.
8.1.5 After both signals reach stable levels,
remove the dummy specimen holder and insert the specimen in the test
position within 10 s. Immediately start both the clock and chronograph
.
8.1.6 Operate the event marker of the chronograph
to indicate the time of ignition and arrival of the flame front during
the initial rapid involvement of the specimen. The arrival at a given
position should be observed as the time at which the flame front at
the longitudinal centreline of the specimen is observed to coincide
with the position of two corresponding wires of the viewing rakes.
These times are recorded manually both from measurement on the chronograph
chart and from observations of the clock. As far as possible, the
arrival of the flame front at each 50 mm position along the specimen
should be recorded. Record both the time and the position on the specimen
at which the progress of flaming combustion ceases. The panel operating
level, as well as stack signals, should be recorded throughout the
test and continued until test termination.
8.1.7 Throughout the conduct of the test, no change
should be made in the fuel supply rate to the radiant panel to compensate
for variations in its operating level.