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Ignition sensibility of nylon fibres
Dust explosibility is up to now a well known problem in the industrial safety field. On the contrary, much less is known about the explosibility of clouds of fibrous materials dispersed in air. Nevertheless, some related accidents are reported in the scientific and technical literature. Some sort of nylon fibres, called flock, is used in the textile industry to produce a special kind of fabric. The production process involves the dispersion in air of the fibres studied in this work. Several experimental tests were run on flock samples having various length and diameter, in order to study the ignition energy, the possibility of auto ignition of deposited layers and the explosion severity indices (maximum explosion pressure, pmax and dust explosion constant Kst. The ignition energy measurements were made using a modified Hartmann apparatus, the possibility of auto ignition was studied by means of a hot plate and the explosion severity indices were measured using a 20 L spherical vessel equipped with chemical igniters. In some case a statistical criterion was also developed to analyse the significance of the results obtained. The explosion characteristics of the studied nylon fibres (flock) were found to be very similar to those of an explosible organic dust. The measurements of the severity indices classified the samples into the St 1 class. The maximum values of the pressure and of the rate of pressure rise were found at a concentration of 750 g/m3. The Minimum Ignition Energy (MIE) was as low as 145 mJ and an influence of the fibre dimension was observed. At the moment, both the length and the diameter of the fibres seem to influence the MIE, according to (Von Pidoll, 2002). The MIE values were found at nominal concentrations (calculated for the 1.2 L Modified Hartmann Apparatus) ranging from 750 g/m3 and 1000 g/m3; this shows a good agreement with the results of the experimentation with the 20 L vessel. But for a sample (G2), all the measurements where made only at 180 ms delay time; the tests on sample G2 showed that the MIE increased at a lower delay time. The statistic analysis of the results showed that consecutive dispersion of the same sample after a failed ignition, led to a low reproducibility of the ignition phenomenon. This seems to depend on the electrostatic adhesion of part of the samples to the inner surfaces after a first dispersion. The ignition probability showed a strong dependence on the spark energy between E1, MIE and E3. The difference between MIE and E3 increases as both the diameter and the length of the fibre increases. The smouldering combustion and autoignition tests revealed that until 270 deg C no autoignition phenomenon occurs to layers of up to 80 mm. on the contrary melting and thermal decomposition give a significant production of combustible gases. The dependence of the MIE respect to the fibre diameter and length needs deeper investigation, the experimentation will be further extended to a wider set of samples.
Ignition sensibility of nylon fibres
Dust explosibility is up to now a well known problem in the industrial safety field. On the contrary, much less is known about the explosibility of clouds of fibrous materials dispersed in air. Nevertheless, some related accidents are reported in the scientific and technical literature. Some sort of nylon fibres, called flock, is used in the textile industry to produce a special kind of fabric. The production process involves the dispersion in air of the fibres studied in this work. Several experimental tests were run on flock samples having various length and diameter, in order to study the ignition energy, the possibility of auto ignition of deposited layers and the explosion severity indices (maximum explosion pressure, pmax and dust explosion constant Kst. The ignition energy measurements were made using a modified Hartmann apparatus, the possibility of auto ignition was studied by means of a hot plate and the explosion severity indices were measured using a 20 L spherical vessel equipped with chemical igniters. In some case a statistical criterion was also developed to analyse the significance of the results obtained. The explosion characteristics of the studied nylon fibres (flock) were found to be very similar to those of an explosible organic dust. The measurements of the severity indices classified the samples into the St 1 class. The maximum values of the pressure and of the rate of pressure rise were found at a concentration of 750 g/m3. The Minimum Ignition Energy (MIE) was as low as 145 mJ and an influence of the fibre dimension was observed. At the moment, both the length and the diameter of the fibres seem to influence the MIE, according to (Von Pidoll, 2002). The MIE values were found at nominal concentrations (calculated for the 1.2 L Modified Hartmann Apparatus) ranging from 750 g/m3 and 1000 g/m3; this shows a good agreement with the results of the experimentation with the 20 L vessel. But for a sample (G2), all the measurements where made only at 180 ms delay time; the tests on sample G2 showed that the MIE increased at a lower delay time. The statistic analysis of the results showed that consecutive dispersion of the same sample after a failed ignition, led to a low reproducibility of the ignition phenomenon. This seems to depend on the electrostatic adhesion of part of the samples to the inner surfaces after a first dispersion. The ignition probability showed a strong dependence on the spark energy between E1, MIE and E3. The difference between MIE and E3 increases as both the diameter and the length of the fibre increases. The smouldering combustion and autoignition tests revealed that until 270 deg C no autoignition phenomenon occurs to layers of up to 80 mm. on the contrary melting and thermal decomposition give a significant production of combustible gases. The dependence of the MIE respect to the fibre diameter and length needs deeper investigation, the experimentation will be further extended to a wider set of samples.
Ignition sensibility of nylon fibres
Marmo, L. (author) / Cavallero, D. (author) / Suppo, V. (author)
2007
6 Seiten, 4 Bilder, 5 Tabellen, 11 Quellen
Conference paper
Storage medium
English
Minimum ignition energy of nylon fibres
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