ISO/TR 5660-3:2003 pdf download

ISO/TR 5660-3:2003 pdf download.Reaction-to-fire tests -Heat release,smoke production and mass loss rate 一Part 3: Guidance on measurement.
4.5 Determining orifice plate calibration factor
4.5.1 Calibration using methane (see 10.2.4 of ISO 5660-1:2002)
It is recommended that the calibration consisting of burning methane be carried out when the heater has been set at the required heat flux. This allows the differential pressure transducer (DPT) to warm up. The fan is shut down and the DPT re-adjusted to zero. The fan is then set to the required air flow and then the burning of methane is carried out.
ISO 5660-1 requires that at the start of each day, one heat release calibration corresponding to a heat release flow rate of 5 kW of the supplied methane be carried out. An orifice constant between 0,040 and 0,046 should be obtained with 99,9 % or 99,5 % methane at a flow rate of 8 1/mm referenced to standard temperature and pressure, or 0,1 g/s (6 g/min). Daily calibration factors should agree within approximately ±1 %.
It should be noted that the heat release calibration using methane does not constitute an absolute calibration of the instrument, but rather that it verifies the orifice plate constant, which appears in the calculations [see Equation (5) in 12.1, Equation (7) in 12.3.2 and Equation (9) in 12.4 of ISO 5660-1:2002]. It is not a direct measurement of heat release.
Black polymethylmethacrylate (PMMA) (with a thickness of 6 mm or greater) can also be used within each laboratory to check repeatability of the cone calorimeter performance.
When zeroing the differential pressure transducer (DPT), ensure that the duct fan and any “decoupled” extractor system are switched off. Air should be prevented from flowing over the open end of the stack and across the orifice plate. If necessary, a plastic bag or equivalent should be used to block the open end of the stack.
It is important to keep records of the values of A’02 (oxygen analyser reading, mole fraction of oxygen), Te (absolute temperature of gas at the orifice meter) and Ap (orifice meter pressure differential) which lead to good calibration factors which should also be noted every time the calibration is carried out. In this way any discrepancy is immediately identified and early correction can be carried out.
4.5.2 Calibration using liquids
It should be noted that when calibrating using liquids, which usually have low flash points, it is essential that calibrations be performed on a cold system (the cone heater is not powered). The liquid should be held in a stable vessel, and the vessel should be stable under the cone before ignition of the liquid. The burning liquid should not be disturbed until it is all burned.
In addition to burning methane for calibration, users have used a variety of materials such as alcohols. The heats of combustion of ethanol and propan-2-ol are 26,8 kJ/g and 30,2 kJ/g, respectively. It is desirable to use propan-2-ol with a purity 99,5 %.
4.6 Weighing device calibration (see 10.1.3, 10.1.4 and 10.2.3 of ISO 5660-1:2002)
The weighing device is simple and generally problem free. Follow the manufacturer’s instructions on recommendations for taring, calibrating and setting the damping of the weighing device.
4.7 Additional comments on the orifice calibration factor
Some variation of the orifice plate calibration factor (also known as the methane calibration factor) may be observed for various reasons. However, any large (5 %) changes in values are indicative of malfunction in the system. In the majority of cases, the problem is caused by leaks into the sampling lines, in which case the recorded factor will be higher than usual. Other items that can cause problems are
blockages in the gas sampling line,
— connections between the orifice plate and the differential pressure transducer,
The most common cause for this is some leakage in the system. However，in one instance a userencountered low values of the order indicated above. After extensive testing indicating that no leaks werepresent in the system and everything else was functioning correctly, the refrigeration system was suspectedand it was flushed with propanone.