| Zugriffsnummer | 33247 |
| Dokumenttyp | Dissertation |
| Peer Review | unbekannt |
| Sprache | Deutsch |
| Titel | Zündwirksamkeit von Ultraschall in explosionsfähigen Atmosphären |
| Autor(in); Institution |
Simon, Lars Hendrik; 3.7, Grundlagen des Explosionsschutzes, PTB-Braunschweig
|
| Quelle/Jahr | (2014), IX, 106 S. |
| Schriftenreihe | Berichte aus dem Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik: 48 |
| Dissertationsvermerk | Dissertation, Technische Universität Braunschweig, 2014 |
| ISBN | 978-3-86387-541-1 |
| URL | |
| Verlag | Berlin: Mensch-und-Buch-Verl. |
| Zusammenfassung | International safety regulations consider ultrasound to be an ignition source. Currently, applications of ultrasound in explosive atmospheres have to comply with harsh requirements which are based only on theoretical estimations in analogy to other ignition sources rather than experimental data. Moreover, there are no publications or significant records on these estimations.Therefore, the research presented here gives a comprehensive assessment of the incendivity of ultrasound in explosive atmospheres. Hence, for airborne and liquid-borne ultrasound, worst-case conditions that provoke ignition were theoretically evolved and successively transformed into experimental setups. This way, it was possible to systematically investigate these worst-case situations and to show that ultrasound really can ignite explosive atmospheres if the acoustic energy is transformed into heat by a highly sound absorbing target. For airborne ultrasound, ignition of sulfur dust-air mixtures and carbon disulphide-air mixtures was observed. A 20 kHz ultrasound standing wave field such as it is used for acoustic levitation was considered to be the worst case. Due to extreme sound pressure levels targets of porous materials heated up until ignition eventually was triggered by their hot surface. In the case of liquid-borne ultrasound, on the one hand, it was shown that highly focused MHz ultrasound can cause ignition at liquid surfaces adjacent to explosive atmospheres of vapors with a low autoignition temperature. In this case, a target of highly temperature resistant plastic was used to transform acoustic energy into heat. On the other hand, acoustic cavitation is not capable of igniting explosive atmospheres. On the basis of the results of the research it is now possible to revise the current regulations and to specify measures to safely operate ultrasonic applications in explosive atmospheres. In this context, requirements for the safe operation of ultrasonic applications in explosive atmospheres are presented and discussed. For airborne and liquid-borne ultrasound new threshold values are suggested that mean an augmentation by two orders of magnitude compared to the currently valid threshold while keeping the same level of safety. |
