BS/EN 3844-2-2019 pdf download.Aerospace series — Flammability of non-metallic materials
Part 2: Small burner test, horizontal — Determination of the horizontal flame propagation.
6 Test apparatus
6.1 Test cabinet
Tests shaH be conducted in a draught-free cabinet, as shown in Figure 1 or other equivalent enclosures. Details and dimensions of a suitable test cabinet are given in Figure 2.
Cabinets of bigger dimensions may be used If it has been proven that similar results are obtained. 1 mm thick metal sheet shall be used for the bottom surface of the cabinet.
It is recommended to paint the entire inside back walls of the cabinet mat black to facilitate the viewing of the test specimen. A mirror may be located on the Inside back surface to facihtate observation of the hidden surface.
It is suggested that the cabinet be located Inside an exhaust hood for clearing the cabinet of smoke and fumes after each test.
6.2 Specimen holder
The specimen holder shall be tabricated ol corrosion-resistant metal.
A specimen holder shall be provided, such that the exposed area of the specimen is at least 50 mm 305 mm. An example for a construction is given In Figure 3.
Each of the rectangular frames must be 6,5 mm in thickness. An example for a construction is given in Figure 3.
6.3.1 Burner type
The burner shall be a Bunsen or Timi type, have a 9.5 mm inside diameter barrel, and shall be equipped
with a needle valve to adjust the gas flow rate and thereby adjust the flame height.
The burner shall have no air supplied either directly or by aspiration. The Bunsen burner defined in
ASTM-D 5025 has been found acceptable.
6.3.2 Burner fuel
Methane gas shall be used as burner tuel. Natural gas is also acceptable ii it contains more than 90 %
methane.
6.3.3 Plumbing for gas supply
The necissary gas connections and the applicable plumbing shall be essentially as specified in Figure 4.
A control valve system with a delivery rate designed to furnish gas to the burner under a pressure of
(17 ± 2) kPa at the burner inlet shall be installed between the gas supply and the burner.
6.3.4 Flame height indicator
A ilame indicator shall be used. A suitable indicator is shown in Figure 5. The indicator shall have two height indicators, e.g. prongs marking the distances 22 mm and 38 mm above the top of the burner. When the flame is properly adjusted, then the tip of the flame shall be at the 38 mm prong and for pure methane the tip of the inner cone of the flame will be at the 22 mm prong. The flame height indicator may be removable.
6.3.5 Flame temperature
When the height is adjusted, measure the flame temperature with the help of a calibrated temperature measurement device and an allocated thermocouple (Type K. 0 1.5 mm). The tip of the thermocouple shall be completely in the flame. The flame temperature shall be at least 843 °C.
6.4 Timer
One or more stop-watches or other timers, calibrated and graduated to the nearest 0.1 s, shall be used to measure the time of flame application and the time of the specimen burning.
6.5 Ruler
A ruler or a scale, calibrated and graduated to the nearest 1 mm. shall be used to measure the burn length and for specimen preparation.
7.2 Specimens orientation
For materials which may have anisotropic flammability properties (i.e. different properties in different directions, such as machine and cross-machine direction for extrusions, warp and weft for woven fabrics, etc.), the specimens shall be tested in both directions.
The values for every direction have to be averaged and reported separately.
7.3 Specimens size
The specimens shall be a rectangle of at least 75 mm x 305 mm. unless the actual size used in the aircraft is smaller.
The specimen thickness shall be no thicker than the minimum thickness to be qualified for use in the aircraft. The specimen thickness will not exceed 3 mm.
7.4 Specimens preparation
Mark gauge lines on the back surface (opposite the exposed surface) of the specimen as shown in Figure 6.
8 Conditioning
Condition specimens at (23 ± 2) °C and at (50 ± 5) % relative humidity for mm. 24 h. Remove only one specimen at a time from the conditioning environment immediately before being tested.
9 Burner adjustment
a) Assure that the air supply to the burner is shut off.
b) Open the stopcock in the gas line fully.
c) Light the burner.
d) Adjust the gas flowraie to produce a flame height of 38 mm. 10 Test procedure
Make sure that the test cabinet is essentially draught free. Place the burner at least 76 mm away from the test position.BS/EN 3844-2-2019 pdf download.