GB/T 20284-2006Single burning item test for building materials and products (English PDF)

4.1 Overview

The test apparatus comprises a combustion chamber, a trolley, an ignition source, a smoke collection hood, an exhaust duct, measuring instruments within the exhaust duct, a white-light smoke measurement system, and flue gas analysis instruments. A schematic diagram of the test apparatus is shown in Figure 1.

4.3 Trolley

The trolley is used to support the specimen (see Figure 1). Once the trolley is positioned within the combustion chamber, its inlet and outlet openings must be sealed, with the exception of the air inlet at the bottom. Perforated plates shall be installed at the front, left, and right sides of the trolley base. These plates shall have hole diameters of 8 mm~12 mm and an open area ratio of 40%~60%. The specimen shall be mounted on the trolley base plate (see 6.5), and the base plate shall be positioned horizontally.

NOTE. Using a spirit level is a convenient way to check the level of the cart's base plate.

The backing board shall be a calcium silicate board as specified in GB/T 40238, with dimensions as follows.

a) Backing board for the short wing of the specimen. (>=570 + specimen thickness) mm × (1500 ± 5) mm;

b) Backing board for the long wing of the specimen. (1,000 + air gap ± 5) mm × (1500 ± 5) mm.

4.4 Ignition source

The ignition source is a triangular metal burner, see Figure 3a). It shall be positioned in the corner of the U-shaped slot in the trolley base plate, with its top surface (25 ± 3) mm above the top surface of the U-shaped slot.

The ignition source shall be designed to allow gas to flow smoothly and evenly out of the top surface of the burner. Internally, the ignition source shall be arranged from bottom to top with a 10 mm thick air layer, a 50 mm thick packed layer composed of ceramic spheres with diameters of 4 mm~8 mm, and a 20 mm thick packed layer composed of ceramic spheres with diameters of 2 mm~4 mm, see Figure 3b).

Figure 3 -- Schematic diagram of ignition sources

The gas used for the ignition source shall be propane with a purity of not less than 95%.

A mass flow controller shall be used to regulate the propane flow rate. The mass flow controller shall have a measurement range of at least 0 g/s~2.3 g/s, with a reading accuracy of 1% within the 0.6 g/s~2.3 g/s range.

A remote ignition method shall be used for the ignition source. Safety facilities, such as gas safety valves and emergency stop devices, shall be provided to ensure the safe use of gas.

4.5 Smoke collection hood

The smoke collection hood is fixed to the top of the support frame within the combustion chamber. The length of the hood's base shall be no less than 1450 mm, and its width no less than 1255 mm. A collector shall be provided at the top of the hood, and this collector shall be equipped with a connection port for the exhaust duct.

4.6 Smoke exhaust duct

The exhaust duct is connected to the collector. The inner diameter (D) of the duct shall be 300 mm~400 mm. The length of the straight duct section shall be no less than 12D.

4.7 Measuring instruments in smoke exhaust ducts

4.7.1 Pressure-measuring probe

The pressure difference of the airflow within the smoke exhaust duct shall be measured using a bidirectional pressure probe (see Figure 4) or a hemispherical pressure probe (see Figure 5). The pressure probe shall be installed in a straight section of the smoke exhaust duct at a position along the duct axis no less than 8D from the inlet end of that section. Conduits of equal length shall be used to connect the pressure probe to the pressure sensor. The pressure sensor shall have a measurement range of 0 Pa~200 Pa and an accuracy of ±5 Pa.

4.9 Flue gas analysis instruments

4.9.1 The volume fractions of oxygen and carbon dioxide in the flue gas within the exhaust duct shall be measured using a gas analyzer. Moisture shall be removed using a desiccant before the flue gas sample enters the gas analyzer.

4.9.2 The oxygen analyzer shall be of the paramagnetic type or another gas analyzer with equivalent performance. The measurement range shall be at least 16%~21% (Voxygen / Vair). The resolution of the output value shall not exceed 0.01%.

4.9.3 The carbon dioxide analyzer shall be an infrared (IR) type or another gas analyzer with equivalent performance. The measurement range shall be at least 0%~10%. The resolution of the output value shall not exceed 0.01%. The linearity of the carbon dioxide analyzer shall not exceed ±1% of the full scale.

4.10 Environmental parameter measurement instrument

4.10.1 An instrument for measuring ambient temperature. shall be a Type K thermocouple with a diameter of (2 ± 1) mm that complies with the requirements of

GB/T 16839.1.This thermocouple shall be fixed to the outer wall of the combustion chamber at a distance of no more than 0.20 m from the trolley inlet/outlet and the ground.

4.10.2 An air relative humidity measuring instrument. with an accuracy of ±5% within

the relative humidity range of 20%~80%.

4.10.3 An atmospheric pressure measuring instrument. with an accuracy of ±200 Pa.

4.11 Data acquisition system

The data acquisition system shall automatically record the measured output values from the mass flow controllers, pressure probes, thermocouples, gas analyzers, white-light smoke measurement system, and other instruments. The accuracy of the data acquisition system shall be ±0.01% for oxygen and carbon dioxide volume fractions,

±0.5°C for temperature data, and ±0.1 s for time data. For other measured data, the accuracy shall be ±0.01% of the full-scale output value.

5.1 General

The test apparatus shall be calibrated in accordance with 5.2~5.3.

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