The Ignitability Test

Ignitability is an important property for the following substancescombustible solids, 

The minimum ignition energy decreases drastically as the ambient temperature rises. It increases as pressure decreases, and there is a certain pressure above which a substance will not ignite. It increases when some inert gas is added to the air, whereas it decreases when oxygen is added. 

In this section, two other methods of ignitability testing are introduced. One is for the 

2 Small gas flame ignitability test ( ) Classification test of the class II hazardous substances as per the Fire Services Law. 

This test enables comparative ignition experiments with easily ignitable solid inorganic substances. The sample is brought into contact with a small gas flame and one observes if ignition occurs. 

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It is usually advisable to carry out the ignition test first. This will provide useful information as to the general properties of the compound and, in particular, the residue may be employed for the detection of any inorganic elements which may be present. 

Test for elements. If the mixture is an aqueous solution, evaporate a small portion (c. 1 ml) to dryness upon platinum foil or in a small crucible. Use a portion of the residue to test for elements (Section 9.3) and another portion for the Ignition test, below. 

The Arrhenius expression (Equation 19.1) using the activation energy and pre-exponential factor derived from TGA measurements of a PA6 sample in N2 was incorporated in a standard ID pyrolysis model described in Section 19.6. The thermal properties used in the model are the ones from the ignition tests (Section 19.4.2.2) as described in Section 19.6 in conjunction with the MDSC experiments (Section 19.3.2.2). Figures 19.25a-c show the predicted surface temperature histories for... 

Here / g denotes the ignition temperature that can be determined from the ignition tests and a is the Stefan-Boltzmann radiation constant. 

For ease of numerical solutions, x = 0 is always located at the top surface as shown in Figure 19.28. The thickness of the unpyrolyzed material also changes as pyrolysis continues. The effective thermal properties (k and c) of the polymer are deduced from the ignition tests as detailed in Section 19.6.3. 

Derived from the Ignition Tests, Along with the Literature Values Reported... 

The ignition test was carried out using samples previously used in environmental tests to compare the state of their burning to that of new samples. No difference was observed between the previously tested samples and the new ones, proving that impact, vibration, and temperature, such as imposed in these tests, will not affect the... 

B) Fractional Distillation of an Ethanol-Water Mixture. Place the 50 mL of distillate from the simple distillation experiment in a 100-mL round-bottomed flask, add one or two boiling chips, and assemble the apparatus for fractional distillation. Follow the procedure (above) for the fractional distillation of a cyclohexane-toluene mixture. Repeat the ignition test. Is any difference noted ... 

Results of the ignition test for different gaseous fuels (CEC PIER Contract 500-05-026). 

Upon completion of the ignition test, the burner has to be evaluated for the safe and reliable combustion performance. For example, in order to satisfy UL certification requirements it has to be continuously fired at maximum capacity for 250 hours with daily monitoring of its combustion performance (exhaust temperature and composition, fuel burning rate, controls operation, etc.). All the data are collected and recorded in corresponding data collection sheets that includes the following parameters along with registered visual observation ... 

Besides the theoretical analysis of the oxygen balance, some results from tests performed as part of the basic assessment also give good indication on an explosion risk related to handling a certain substance. Primarily these are energy values determined with the help of DTA or DSC measurements, the burning number, and first results obtained from the ignitability test of solid substances. 

This test method determines the material properties related to piloted ignition of a vertically oriented sample under a constant and uniform heat flnx and to lateral flame spread on a vertical snrface dne to an externally applied radiant-heat flux. For the ignition test, a 155-nun (6-inch) square sample is exposed to a... 

The ignition and combustion tests are performed in normal air, whereas the fire propagation test is performed in 40% oxygen concentration in the FMR 4910 test standard and in normal air in the UL 2360 test standard. Heat flux values used in the tests are 0-60 kW/min for the ignition tests in the FMR 4910 test standard and 0-75 kW/m in the UL 2360 test standard. In the combustion tests, sample surface is exposed to 50 kW/m in both the test standards. In the fire propagation tests in the FMR 4910 test standard, only the bottom 20% of the vertical sample is exposed to 50 kW/m in the presence of a pilot flame. 

In the ignition tests, 155-xl55-mm samples are exposed to various external heat flux values and times to flame attachment are measured [15,16]. The values of k, p, Cp, ATig are determined from the relationship between the time to flame attachment and external heat flux [15,16]. These values can be used to calculate the TRP value [Eq. (53.4)]. 

The two combustion tests, the Beilstein test (Experiment 52B) and the ignition test (Experiment 52C), can be performed easily and quickly, and they often give valuable information. It is recommended that they be performed on all unknowns. 

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