Part IV – Test Method to Determine the Heat Release Rate From Cabin Materials Exposed to Radiant Heat
(a) Summary of Method
(1) The specimen to be tested is
injected into an environmental chamber
through which a constant flow of air passes.
The specimen’s exposure is determined by a
radiant heat source adjusted to produce the
desired total heat flux on the specimen of
3·5 Watts/cm2, using a calibrated calorimeter.
The specimen is tested so that the exposed
surface is vertical. Combustion is initiated by
piloted ignition. The combustion products
leaving the chamber are monitored in order to
calculate the release rate of heat.
(b) Apparatus. The Ohio State University
(OSU) rate of heat release apparatus as described
below, is used. This is a modified version of the
rate of heat release apparatus standardised by the
American Society of Testing and Materials
(ASTM), ASTM E-906.
(1) This apparatus is shown in Figure 1.
All exterior surfaces of the apparatus, except
the holding chamber, shall be insulated with
25 mm thick, low density, high-temperature,
fibreglass board insulation. A gasketed door
through which the sample injection rod slides
forms an airtight closure on the specimen hold
chamber.
(2) Thermopile. The temperature
difference between the air entering the
environmental chamber and that leaving is
monitored by a thermopile having five hot and
five cold, 24 gauge Chromel-Alumel junctions.
The hot junctions are spaced across the top of
the exhaust stack 10 mm below the top of the
chimney. One thermocouple is located in the
geometric centre, with the other four located
30 mm from the centre along the diagonal
toward each of the corners (Figure 5). The
cold junctions are located in the pan below the
lower air distribution plate (see sub-paragraph
(b)(4)). Thermopile hot junctions must be
cleared of soot deposits as needed to maintain
the calibrated sensitivity.
(3) Radiation Source. A radiant heat
source for generating a flux up to 100 kW/m2,
using four silicon carbide elements, Type LL,
20 inches (50·8 cm) long by 0·625 inch
(15·8 mm) O.D., nominal resistance 1·4 ohms,
is shown in Figures 2A and 2B. The silicon
carbide elements are mounted in the stainless
steel panel box by inserting them through
15·9 mm holes in 0·8 mm thick ceramic fibre
board. Location of the holes in the pads and
stainless steel cover plates are shown in Figure
2B. The diamond shaped mask of 19 gauge
stainless steel is added to provide uniform heat
flux over the area occupied by the 150 by
150 mm vertical sample.
(4) Air Distribution System. The air
entering the environmental chamber is
distributed by a 6·3 mm thick aluminium plate
having eight, No. 4 drill holes, 51 mm from
sides on 102 mm centres, mounted at the base
of the environmental chamber. A second plate
of 18 gauge steel having 120, evenly spaced,
No. 28 drill holes is mounted 150 mm above
the aluminium plate. A well-regulated air
supply is required. The air supply manifold at
the base of the pyramidal section has 48,
evenly spaced, No. 26 drill holes located
10 mm from the inner edge of the manifold so
that 0·03 m3/second of air flows between the
pyramidal sections and 0·01 m3/second flows
through the environmental chamber when total
air flow to apparatus is controlled at
0·04 m3/second.
(5) Exhaust Stack. An exhaust stack,
133 mm by 70 mm in cross section, and
254 mm long, fabricated from 28 gauge
stainless steel, is mounted on the outlet of the
pyramidal section. A 25 mm by 76 mm plate of
31 gauge stainless steel is centred inside the
stack, perpendicular to the air flow, 75 mm
above the base of the stack.
(6) Specimen Holders. The 150 mm x
150 mm specimen is tested in a vertical
orientation. The holder (Figure 3) is provided
with a specimen holder frame, which touches the
specimen (which is wrapped with aluminium foil
as required by sub-paragraph (d)(3)) along only
the 6 mm perimeter, and a “V” shaped spring to
hold the assembly together. A detachable 12 mm
x 12 mm x 150 mm drip pan and two 0·020 inch
stainless steel wires (as shown in Figure 3) should
be used for testing of materials prone to melting
and dripping. The positioning of the spring and
frame may be changed to accommodate different
specimen thicknesses by inserting the retaining
rod in different holes on the specimen holder.
Since the radiation shield described in
ASTM E-906 is not used, a guide pin is added
to the injection mechanism. This fits into a
slotted metal plate on the injection mechanism
outside of the holding chamber and can be
used to provide accurate positioning of the
specimen face after injection. The front
surface of the specimen shall be 100 mm from
the closed radiation doors after injection.
The specimen holder clips onto the
mounted bracket (Figure 3). The mounting
bracket is attached to the injection rod by three
screws which pass through a wide area washer
welded onto a 13 mm nut. The end of the
injection rod is threaded to screw into the nut
and a 5.1 mm thick wide area washer is held
between two 13 mm nuts which are adjusted to
tightly cover the hole in the radiation doors
through which the injection rod or calibration
calorimeter pass.
(7) Calorimeter. A total-flux type
calorimeter must be mounted in the centre of a
13 mm Kaowool “M” board inserted in the
sample holder must be used to measure the
total heat flux. The calorimeter must have a
view angle of 180º and be calibrated for
incident flux. The calorimeter calibration must
be acceptable to the Authority.
(8) Pilot-Flame Positions. Pilot ignition
of the specimen must be accomplished by
simultaneously exposing the specimen to a
lower pilot burner and an upper pilot burner, as
described in sub-paragraphs (b)(8)(i) and
(b)(8)(ii), respectively. The pilot burners must
remain lighted for the entire 5-minute duration
of the test.
(i) Lower Pilot Burner. The
pilot-flame tubing must be 6·3 mm O.D.,
0·8 mm wall, stainless steel tubing. A
mixture of 120 cm3/min. of methane and
850 cm3/min. of air must be fed to the
lower pilot flame burner. The normal
position of the end of the pilot burner
tubing is 10 mm from and perpendicular
to the exposed vertical surface of the
specimen. The centreline at the outlet of
the burner tubing must intersect the
vertical centreline of the sample at a
point 5 mm above the lower exposed
edge of the specimen.
(ii) Upper Pilot Burner. The pilot
burner must be a straight length of 6·3 mm
O.D., 0·8 mm wall, stainless steel tubing
360 mm long. One end of the tubing shall
be closed, and three No. 40 drill holes shall
be drilled into the tubing, 60 mm apart, for
gas ports, all radiating in the same direction.
The first hole must be 5 mm from the closed
end of the tubing. The tube is inserted into
the environmental chamber through a
6·6 mm hole drilled 10 mm above the upper
edge of the window frame. The tube is
supported and positioned by an adjustable
“Z” shaped support mounted outside the
environmental chamber, above the viewing
window. The tube is positioned above and
20 mm behind the exposed upper edge of
the specimen. The middle hole must be in
the vertical plane perpendicular to the
exposed surface of the specimen which
passes through its vertical centreline and
must be pointed toward the radiation source.
The gas supplied to the burner must be
methane adjusted to produce flame lengths
of 25 mm.
(iii) Not required.
(c) Calibration of Equipment
(1) Heat Release Rate. A burner as
shown in Figure 4 must be placed over the end
of the lower pilot flame tubing using a gas-tight
connection. The flow of gas to the pilot flame
must be at least 99% methane and must be
accurately metered. Prior to usage, the wet test
meter is properly levelled and filled with
distilled water to the tip of the internal pointer
while no gas is flowing. Ambient temperature
and pressure of the water, are based on the
internal wet test meter temperature. A baseline
flow rate of approximately 1 litre/min. is set
and increased to higher preset flows of 4, 6, 8,
6 and 4 litres/min. The rate is determined by
using a stopwatch to time a complete
revolution of the west test meter for both the
baseline and higher flow, with the flow
returned to baseline before changing to the next
higher flow. The thermopile baseline voltage is
measured. The gas flow to the burner must be
increased to the higher preset flow and allowed
to burn for 2·0 minutes, and the thermopile
voltage must be measured. The sequence is
repeated until all five values have been
determined. The average of the five values
must be used as the calibration factor. The
procedure must be repeated if the percent
relative standard deviation is greater than 5%.
Calculations are shown in paragraph (f).
(2) Flux Uniformity. Uniformity of
flux over the specimen must be checked
periodically and after each heating element
change to determine if it is within acceptable
limits of ± 5%.
(3) Not required.
(d) Sample Preparation
(1) The standard size for vertically
mounted specimens is 150 x 150 mm with
thicknesses up to 45 mm.
(2) Conditioning. Specimens must be
conditioned as described in Part 1 of this
Appendix.
(3) Mounting. Only one surface of a
specimen will be exposed during a test. A
single layer of 0·025 mm aluminium foil is
wrapped tightly on all unexposed sides.
(e) Procedure
(1) The power supply to the radiant
panel is set to produce a radiant flux of 3·5
Watts/cm2. The flux is measured at the point
which the centre of the specimen surface will
occupy when positioned for test. The radiant
flux is measured after the air flow through the
equipment is adjusted to the desired rate. The
sample should be tested in its end use
thickness.
(2) The pilot flames are lighted and
their position, as described in sub-paragraph
(b)(8), is checked.
(3) The air flow to the equipment is set
at 0·04 ± 0·001 m3/s at atmospheric pressure.
Proper air flow may be set and monitored by
either: (1) An orifice meter designed to
produce a pressure drop of at least 200 mm of
the manometric fluid, or by (2) a rotometer
(variable orifice meter) with a scale capable of
being read to ± 0·0004 m3/s. The stop on the
vertical specimen holder rod is adjusted so that
the exposed surface of the specimen is
positioned 100 mm from the entrance when
injected into the environmental chamber.
(4) The specimen is placed in the hold
chamber with the radiation doors closed. The
airtight outer door is secured, and the recording
devices are started. The specimen must be
retained in the hold chamber for 60 seconds
± 10 seconds, before injection. The thermopile
“zero” value is determined during the last
20 seconds of the hold period.
(5) When the specimen is to be
injected, the radiation doors are opened, the
specimen is injected into the environmental
chamber, and the radiation doors are closed
behind the specimen.
(6) Reserved.
(7) Injection of the specimen and
closure of the inner door marks time zero. A
continuous record of the thermopile output
with at least one data point per second must be
made during the time the specimen is in the
environmental chamber.
(8) The test duration time is five
minutes.
(9) A minimum of three specimens
must be tested.
(f) Calculations
(1) The calibration factor is calculated
as follows:
) (
F0 = Flow of methane at baseline (1pm)
F1 = Higher preset flow of methane (1pm)
V0 = Thermopile voltage at baseline (mv)
V1 = Thermopile voltage at higher flow (mv)
Ta = Ambient temperature (K)
P = Ambient pressure (mm Hg)
Pv = Water vapour pressure (mm Hg)
(2) Heat release rates may be calculated
from the reading of the thermopile output
voltage at any instant of time as:
HRR = Heat Release Rate kW/m2
Vm = Measured thermopile voltage (mv)
Vb = Baseline voltage (mv)
Kh = Calibration Factor (kW/mv)
(3) The integral of the heat release rate
is the total heat release as a function of time
and is calculated by multiplying the rate by the
data sampling frequency in minutes and
summing the time from zero to two minutes.
(g) Criteria. The total positive heat release
over the first two minutes of exposure for each of
the three or more samples tested must be
averaged, and the peak heat release rate for each
of the samples must be averaged. The average
total heat release must not exceed 65 kilowattminutes
per square metre, and the average peak
heat release rate must not exceed 65 kilowatts per
square metre.
(h) Report. The test report must include the
following for each specimen tested:
(1) Description of the specimen.
(2) Radiant heat flux to the specimen,
expressed in Watts/cm2.
(3) Data giving release rates of heat (in
kW/m2) as a function of time, either
graphically or tabulated at intervals no greater
than 10 seconds. The calibration factor (Kh)
must be recorded.
(4) If melting, sagging, delaminating,
or other behaviour that affects the exposed
surface area or the mode of burning occurs,
these behaviours must be reported, together
with the time at which such behaviours were
observed.
(5) The peak heat release and the
2 minute integrated heat release rate must be
reported.
(h) Report. The test report must include the
following for each specimen tested:
(1) Description of the specimen.
(2) Radiant heat flux to the specimen,
expressed in Watts/cm2.
(3) Data giving release rates of heat (in
kW/m2) as a function of time, either
graphically or tabulated at intervals no greater
than 10 seconds. The calibration factor (Kh)
must be recorded.
(4) If melting, sagging, delaminating,
or other behaviour that affects the exposed
surface area or the mode of burning occurs,
these behaviours must be reported, together
with the time at which such behaviours were
observed.
(5) The peak heat release and the
2 minute integrated heat release rate must be
reported.
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